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diff --git a/Build/source/texk/web2c/texprofdir/texprof.w b/Build/source/texk/web2c/texprofdir/texprof.w new file mode 100644 index 00000000000..722106017fa --- /dev/null +++ b/Build/source/texk/web2c/texprofdir/texprof.w @@ -0,0 +1,33304 @@ +% TeXprof is copyright (C) 2024 by Martin Ruckert +% Hochschule Muenchen, Lothstrasse 64, 80336 Muenchen +% and put under the MIT/X11 license. +% +% Prote is copyright (C) 2021 by Thierry Laronde and put under +% the MIT/X11 license. +% +% As TeX and e-TeX are reserved names for the unchanged (except for the +% necessary implementation of system dependencies) instances of, resp., +% Donald E. Knuth's program and the NTS team's e-TeX implementation, the +% name Prote is reserved for this kerTeX implementation. +% +% Hence, this is neither TeX (even if it is compatible at start) nor +% e-TeX (even if is compatible when entering the first set of +% extensions). + +% Version 0 was released in September 1982 after it passed a variety of tests. +% Version 1 was released in November 1983 after thorough testing. +% Version 1.1 fixed ``disappearing font identifiers'' et alia (July 1984). +% Version 1.2 allowed `0' in response to an error, et alia (October 1984). +% Version 1.3 made memory allocation more flexible and local (November 1984). +% Version 1.4 fixed accents right after line breaks, et alia (April 1985). +% Version 1.5 fixed \the\toks after other expansion in \edefs (August 1985). +% Version 2.0 (almost identical to 1.5) corresponds to "Volume B" (April 1986). +% Version 2.1 corrected anomalies in discretionary breaks (January 1987). +% Version 2.2 corrected "(Please type...)" with null \endlinechar (April 1987). +% Version 2.3 avoided incomplete page in premature termination (August 1987). +% Version 2.4 fixed \noaligned rules in indented displays (August 1987). +% Version 2.5 saved cur_order when expanding tokens (September 1987). +% Version 2.6 added 10sp slop when shipping leaders (November 1987). +% Version 2.7 improved rounding of negative-width characters (November 1987). +% Version 2.8 fixed weird bug if no \patterns are used (December 1987). +% Version 2.9 made \csname\endcsname's "relax" local (December 1987). +% Version 2.91 fixed \outer\def\a0{}\a\a bug (April 1988). +% Version 2.92 fixed \patterns, also file names with complex macros (May 1988). +% Version 2.93 fixed negative halving in allocator when mem_min<0 (June 1988). +% Version 2.94 kept open_log_file from calling fatal_error (November 1988). +% Version 2.95 solved that problem a better way (December 1988). +% Version 2.96 corrected bug in "Infinite shrinkage" recovery (January 1989). +% Version 2.97 corrected blunder in creating 2.95 (February 1989). +% Version 2.98 omitted save_for_after at outer level (March 1989). +% Version 2.99 caught $$\begingroup\halign..$$ (June 1989). +% Version 2.991 caught .5\ifdim.6... (June 1989). +% Version 2.992 introduced major changes for 8-bit extensions (September 1989). +% Version 2.993 fixed a save_stack synchronization bug et alia (December 1989). +% Version 3.0 fixed unusual displays; was more \output robust (March 1990). +% Version 3.1 fixed nullfont, disabled \write{\the\prevgraf} (September 1990). +% Version 3.14 fixed unprintable font names and corrected typos (March 1991). +% Version 3.141 more of same; reconstituted ligatures better (March 1992). +% Version 3.1415 preserved nonexplicit kerns, tidied up (February 1993). +% Version 3.14159 allowed fontmemsize to change; bulletproofing (March 1995). +% Version 3.141592 fixed \xleaders, glueset, weird alignments (December 2002). +% Version 3.1415926 was a general cleanup with minor fixes (February 2008). +% Version 3.14159265 was similar (January 2014). +% Version 3.141592653 was similar but more extensive (January 2021). + +% A reward of $327.68 will be paid to the first finder of any remaining bug. + +% This is the 1.1 version of Prote, developed during August 2021, +% and corrected during september/october 2021 and amended in august 2023 +% for file primitives behavior matching input behavior. +% +% 1.0: adds primitives needed by LaTeX as listed in ltnews31. +% - 2022-07-21: tiddying formal fix: a spurious line was a left over +% of a removed paragraph (pointed by Martin Ruckert). Suppressed. +% +% 1.1: 2023-08-01: the new file primitives are used in LaTeX expecting +% the input behavior that ".tex" be appended if no extension. So +% modified to provide this. +% +% History towards 1.0 release: +% 0.99.4: +% - typos and style corrections provided by Martin Ruckert for +% clean translation in Pascal (forward declarations and underscores +% omitted); +% - adjustements against e-TeX 2.6 instead of 2.1 (T. Laronde). +% 0.99.7: +% - \expanded was using an e-TeX procedure not doing def handling +% => using scan_toks() now. Reported by Martin Ruckert and +% test code narrowed down by Phelype Oleinik. +% 0.99.8: +% - \expanded again: scan_toks() sets def_ref. But back_list() +% has to take not the refernce count, but the first token. +% Passing def_ref, a next invocation of scan_toks() was inserting +% a missing left brace and then reading pass the end of the token +% list to find a matching right one. def_ref => link(def_ref). +% Test code narrowed down by Phelype Oleinik (a great help!). +% - The API for file related primitives has been changed: no error +% is reported on failure to find/open and nothing is returned +% (matches current other implementations). +% 0.99.9: +% - Fix typos in Pascal replacement text; xchg_buffer_length=0 => +% xchg_buffer_length:=0 (caught by Martin Ruckert). +% 0.99.10: +% - KerTeX Public License -> X11/MIT license. +% 1.0: +% - Just naming the official release. No change. +% +% This work was done by Thierry Laronde and is under the MIT/X11 +% license. +% +% + +% Here is TeX material that gets inserted after \input webmac +\def\hang{\hangindent 3em\noindent\ignorespaces} +\def\hangg#1 {\hang\hbox{#1 }} +\def\textindent#1{\hangindent2.5em\noindent\hbox to2.5em{\hss#1 }\ignorespaces} +\font\ninerm=cmr9 +\let\mc=\ninerm % medium caps for names like SAIL +\def\Prote{{\tenrm P\kern-0.1em R\kern-0.15em\raise.11ex\hbox{o}% + \kern-0.22em T\kern-0.05em E}} +\def\texprof{{\TeX}prof} +\ifpdftex +\sanitizecommand{\texprof}{TeXprof} +\sanitizecommand{\eTeX}{eTeX} +\sanitizecommand{\Prote}{PRoTE} +\fi +\font\tenlogo=logo10 +\def\MP{{\tenlogo META}\-{\tenlogo POST}} +\def\eTeX{$\varepsilon$-\TeX} +\font\revrm=xbmc10 % for right-to-left text +% to generate xbmc10 (i.e., reflected cmbx10) use a file +% xbmc10.mf containing: +%+++++++++++++++++++++++++++++++++++++++++++++++++ +% if unknown cmbase: input cmbase fi +% extra_endchar := extra_endchar & +% "currentpicture:=currentpicture " & +% "reflectedabout((.5[l,r],0),(.5[l,r],1));"; +% input cmbx10 +%+++++++++++++++++++++++++++++++++++++++++++++++++ +\ifx\beginL\undefined % this is TeX + \def\XeT{X\kern-.125em\lower.5ex\hbox{E}\kern-.1667emT} + \def\TeXeT{\TeX-\hbox{\revrm \XeT}} % for TeX-XeT + \def\TeXXeT{\TeX-\hbox{\revrm -\XeT}} % for TeX--XeT +\else + \ifx\eTeXversion\undefined % this is \TeXeT + \def\TeXeT{\TeX-{\revrm\beginR\TeX\endR}} % for TeX-XeT + \def\TeXXeT{\TeX-{\revrm\beginR\TeX-\endR}} % for TeX--XeT + \else % this is \eTeX + \def\TeXeT{\TeX-{\TeXXeTstate=1\revrm\beginR\TeX\endR}} % for TeX-XeT + \def\TeXXeT{\TeX-{\TeXXeTstate=1\revrm\beginR\TeX-\endR}} % for TeX--XeT + \fi +\fi +\def\PASCAL{Pascal} +\def\pdfTeX{pdf\TeX} +\def\ph{\hbox{Pascal-H}} +\def\pct!{{\char`\%}} % percent sign in ordinary text +\def\grp{\.{\char'173...\char'175}} +\font\logo=logo10 % font used for the METAFONT logo +\def\MF{{\logo META}\-{\logo FONT}} +\def\<#1>{$\langle#1\rangle$} +\def\section{\mathhexbox278} + +\def\(#1){} % this is used to make section names sort themselves better +\def\9#1{} % this is used for sort keys in the index via @@:sort key}{entry@@> + +\let\@@=\relax % we want to be able to \write a \? + +\def\title{\texprof} +\def\LaTeX{L\kern-.36em\raise.3ex\hbox{\sc A}\kern-.15em\TeX}% +% system dependent redefinitions of \title should come later +% and should use: +% \toks0=\expandafter{\title} +% \edef\title{...\the\toks0...} +%\let\maybe=\iffalse % print only changed modules +\def\topofcontents{\hsize 5.5in + \vglue 0pt plus 1fil minus 1.5in + \def\@@##1]{\hbox to 1in{\hfil##1.\ }} + } +\def\botofcontents{\vskip 0pt plus 1fil minus 1.5in} +\pageno=3 +\def\glob{13} % this should be the section number of "<Global...>" +\def\gglob{20, 26} % this should be the next two sections of "<Global...>" + +\def\.#1{\leavevmode\hbox{\tentex % typewriter type for strings + \let\\=\BS % backslash in a string + \let\'=\RQ % right quote in a string + \let\`=\LQ % left quote in a string + \let\{=\LB % left brace in a string + \let\}=\RB % right brace in a string + \let\~=\TL % tilde in a string + \let\ =\SP % space in a string + \let\_=\UL % underline in a string + \let\&=\AM % ampersand in a string + \let\^=\CF % circumflex in a string + #1\kern.05em}} +\def\{\leavevmode\hbox{\bf\def\_{\UL}% + #1\/\kern.05em}} % boldface type for reserved words +\def\\#1{\leavevmode\hbox{\it\def\_{\UL}% + #1\/\kern.05em}} % italic type for identifiers +\def\vb#1{{\rm #1}} +%\def\^{\ifmmode\mathchar"222 \else\char`^ \fi} % pointer or hat +\def\LQ{{\tt\char'22}} % left quote in a string +\def\RQ{{\tt\char'23}} % right quote in a string +\def\UL{{\tt\char`\_}} % underline character in a C identifier +\def\CF{{\tt\char`^}} +\def\dotdot{\mathrel{.\,.}} % double dot, used only in math mode +\setbox\MGbox=\hbox{\kern1pt$\rightarrow$\kern1pt} % C pointer to field +\def\MG{\copy\MGbox} +@s dotdot TeX +@s alpha_file int +@s byte_file int +@s word_file int +@s uint8_t int +@s int16_t int +@s uint16_t int +@s int32_t int +@s uint32_t int +@s halfword int +@s nonnegative_integer int +@s small_number int +@s glue_ratio double +@s Xdimen int +@s Kern int +@s Font int +@s Glue int +@s Disc int +@s Lig int +@s Rule int +@s List int +@s Kind int +@s Info int +@s kpse_file_format_type int +@s Stretch int +@s in TeX +@s line normal +@s to do + +@* Introduction. +This is \texprof, an implementation of \TeX\ with an extension providing profiling +capabilities. To be useful nowadays, the profiling capability is not the only +extension of Donald Knuth's original implementation of \TeX. + +To obtain the present \CEE/ program, Donald Knuth's \PASCAL\ program was +modified in a first step using most of the \eTeX\ extensions by +Peter Breitenlohner and Phil Taylor. +@^Breitenlohner, Peter@> +@^Taylor, Phil@> +Then further extensions were added using the \Prote\ change file +of Thierry Laronde. +@^Laronde, Thierry@> +Then the constants defining the size of \TeX's data structures, +notably the size of the |mem| array, were increased considerable. All these +changes to the \PASCAL\ program are necessary to run a current \LaTeX\ on the +resulting \TeX\ engine. The next important step was then to translate this +literate \PASCAL\ program to a literate \CEE/ program using the +{\tt web2w} source code translator. The use of the \CEE/ based \.{cweb} system +instead of the \PASCAL\ based \.{WEB} system greatly simplifies the tool chain +necessary for producing an executable program and allows true source level +debugging of the resulting program. The latter is indispensable to carry out +large scale modifications of the \TeX\ program and is of enormous help even +for smaller modifications. +The first modification of the resulting \CEE/ program was then the addition +of \CEE/ routines from the \TeX\ Live project to enable the use of the +kpath search library by Karl Berry. +@^Berry, Karl@> +The last and final step was the addition of profiling capabilities +which includes, as the latest addition, the definition of numerous +primitives that enable the \TeX\ profiler to pretend to be \pdfTeX. +The code used there reuses parts of the \CEE/ version of \pdfTeX\ by +H\`an Th\^e\llap{\raise 0.5ex\hbox{\'{}}} Th\`anh. +@^Th\`anh, H\`an Th\^e\llap{\raise 0.5ex\hbox{\'{}}}@> + +All these changes left their traces in the text that follows. +No attempt was made to streamline the text and rid it from the traces +of its exciting history. +So with the next paragraph you can start reading Donald Knuth's +introduction to his \TeX\ program. Enjoy! +\medskip + +This is \TeX, a document compiler intended to produce typesetting of high +quality. +The \PASCAL\ program that follows is the definition of \TeX82, a standard +@:PASCAL}{\PASCAL@> +@!@:TeX82}{\TeX82@> +version of \TeX\ that is designed to be highly portable so that identical output +will be obtainable on a great variety of computers. + +The main purpose of the following program is to explain the algorithms of \TeX\ +as clearly as possible. As a result, the program will not necessarily be very +efficient when a particular \PASCAL\ compiler has translated it into a +particular machine language. However, the program has been written so that it +can be tuned to run efficiently in a wide variety of operating environments +by making comparatively few changes. Such flexibility is possible because +the documentation that follows is written in the \.{WEB} language, which is +at a higher level than \PASCAL; the preprocessing step that converts \.{WEB} +to \PASCAL\ is able to introduce most of the necessary refinements. +Semi-automatic translation to other languages is also feasible, because the +program below does not make extensive use of features that are peculiar to +\PASCAL. + +A large piece of software like \TeX\ has inherent complexity that cannot +be reduced below a certain level of difficulty, although each individual +part is fairly simple by itself. The \.{WEB} language is intended to make +the algorithms as readable as possible, by reflecting the way the +individual program pieces fit together and by providing the +cross-references that connect different parts. Detailed comments about +what is going on, and about why things were done in certain ways, have +been liberally sprinkled throughout the program. These comments explain +features of the implementation, but they rarely attempt to explain the +\TeX\ language itself, since the reader is supposed to be familiar with +{\sl The \TeX book}. +@.WEB@> +@:TeXbook}{\sl The \TeX book@> + +@ The present implementation has a long ancestry, beginning in the summer +of~1977, when Michael~F. Plass and Frank~M. Liang designed and coded +a prototype +@^Plass, Michael Frederick@> +@^Liang, Franklin Mark@> +@^Knuth, Donald Ervin@> +based on some specifications that the author (in the following, unless +specified, ``the author'' refers to D.E.~Knuth) had made in May of that year. +This original proto\TeX\ included macro definitions and elementary +manipulations on boxes and glue, but it did not have line-breaking, +page-breaking, mathematical formulas, alignment routines, error recovery, +or the present semantic nest; furthermore, +it used character lists instead of token lists, so that a control sequence +like \.{\\halign} was represented by a list of seven characters. A +complete version of \TeX\ was designed and coded by the author in late +1977 and early 1978; that program, like its prototype, was written in the +{\mc SAIL} language, for which an excellent debugging system was +available. Preliminary plans to convert the {\mc SAIL} code into a form +somewhat like the present ``web'' were developed by Luis Trabb~Pardo and +@^Trabb Pardo, Luis Isidoro@> +the author at the beginning of 1979, and a complete implementation was +created by Ignacio~A. Zabala in 1979 and 1980. The \TeX82 program, which +@^Zabala Salelles, Ignacio Andr\'es@> +was written by the author during the latter part of 1981 and the early +part of 1982, also incorporates ideas from the 1979 implementation of +@^Guibas, Leonidas Ioannis@> +@^Sedgewick, Robert@> +@^Wyatt, Douglas Kirk@> +\TeX\ in {\mc MESA} that was written by Leonidas Guibas, Robert Sedgewick, +and Douglas Wyatt at the Xerox Palo Alto Research Center. Several hundred +refinements were introduced into \TeX82 based on the experiences gained with +the original implementations, so that essentially every part of the system +has been substantially improved. After the appearance of ``Version 0'' in +September 1982, this program benefited greatly from the comments of +many other people, notably David~R. Fuchs and Howard~W. Trickey. +A final revision in September 1989 extended the input character set to +eight-bit codes and introduced the ability to hyphenate words from +different languages, based on some ideas of Michael~J. Ferguson. +@^Fuchs, David Raymond@> +@^Trickey, Howard Wellington@> +@^Ferguson, Michael John@> + +No doubt there still is plenty of room for improvement, but the author +is firmly committed to keeping \TeX82 ``frozen'' from now on; stability +and reliability are to be its main virtues. + +On the other hand, the \.{WEB} description can be extended without changing +the core of \TeX82 itself, and the program has been designed so that such +extensions are not extremely difficult to make. +The |banner| string defined here should be changed whenever \TeX\ +undergoes any modifications, so that it will be clear which version of +\TeX\ might be the guilty party when a problem arises. +@^extensions to \TeX@> +@^system dependencies@> + +This program contains code for various features extending \TeX, +therefore this program is called `\Prote' and not +`\TeX'; the official name `\TeX' by itself is reserved +for software systems that are fully compatible with each other. +A special test suite called the ``\.{TRIP} test'' is available for +helping to determine whether a particular implementation deserves to be +known as `\TeX' [cf.~Stanford Computer Science report CS1027, +November 1984]. + +A similar test suite called the ``\.{SELLETTE} test'' is available for +helping to determine whether a particular implementation deserves to be +known as `\Prote'. + +@d eTeX_version 2 /* \.{\\eTeXversion} */ +@d eTeX_revision ".6" /* \.{\\eTeXrevision} */ +@d eTeX_version_string "-2.6" /*current \eTeX\ version*/ +@# +@d TeX_banner "This is TeX, Version 3.141592653" /*printed when \TeX\ starts*/ +@# +@# +@d TEX ETEX /*change program name into |ETEX|*/ +@# +@d eTeX_states 1 /*number of \eTeX\ state variables in |eqtb|*/ +@# +@d Prote_version_string "3.141592653-2.6-1.1.0" /*current \Prote\ version*/ +@d Prote_version 1 /* \.{\\Proteversion} */ +@d Prote_revision ".1.0" /* \.{\\Proterevision} */ +@# +@d Prote_banner "This is Prote, Version " Prote_version_string + /*printed when \Prote\ starts*/ +@# +@d banner Prote_banner + +@ Different \PASCAL s have slightly different conventions, and the present +@!@:PASCAL H}{\ph@> +program expresses \TeX\ in terms of the \PASCAL\ that was +available to the author in 1982. Constructions that apply to +this particular compiler, which we shall call \ph, should help the +reader see how to make an appropriate interface for other systems +if necessary. (\ph\ is Charles Hedrick's modification of a compiler +@^Hedrick, Charles Locke@> +for the DECsystem-10 that was originally developed at the University of +Hamburg; cf.\ {\sl Software---Practice and Experience \bf6} (1976), +29--42. The \TeX\ program below is intended to be adaptable, without +extensive changes, to most other versions of \PASCAL, so it does not fully +use the admirable features of \ph. Indeed, a conscious effort has been +made here to avoid using several idiosyncratic features of standard +\PASCAL\ itself, so that most of the code can be translated mechanically +into other high-level languages. For example, the `\&{with}' and `\\{new}' +features are not used, nor are pointer types, set types, or enumerated +scalar types; there are no `\&{var}' parameters, except in the case of files +--- \eTeX, however, does use `\&{var}' parameters for the |reverse| function; +there are no tag fields on variant records; there are no assignments +|double=int|; no procedures are declared local to other procedures.) + +The portions of this program that involve system-dependent code, where +changes might be necessary because of differences between \PASCAL\ compilers +and/or differences between +operating systems, can be identified by looking at the sections whose +numbers are listed under `system dependencies' in the index. Furthermore, +the index entries for `dirty \PASCAL' list all places where the restrictions +of \PASCAL\ have not been followed perfectly, for one reason or another. +@!@^system dependencies@> +@!@^dirty \PASCAL@> + +Incidentally, \PASCAL's standard |round| function can be problematical, +because it disagrees with the IEEE floating-point standard. +Many implementors have +therefore chosen to substitute their own home-grown rounding procedure. + +@ The following is an outline of the program, whose +components will be filled in later, using the conventions of \.{cweb}. +@.WEB@> +For example, the portion of the program called `\X\glob:Global +variables\X' below will be replaced by a sequence of variable declarations +that starts in $\section\glob$ of this documentation. In this way, we are able +to define each individual global variable when we are prepared to +understand what it means; we do not have to define all of the globals at +once. Cross references in $\section\glob$, where it says ``See also +sections \gglob, \dots,'' also make it possible to look at the set of +all global variables, if desired. Similar remarks apply to the other +portions of the program. + +The program starts with inserting header files and occassionaly a function +must be placed before declaring \TeX's macros, because the function +uses identifiers that \TeX will declare as macros. + +@p @<Header files and function declarations@>@; +@h +enum {@<Constants in the outer block@>@; + @!empty_string=256 /*the empty string follows after 256 characters*/ +}; +@<Types in the outer block@>@; +@<Forward declarations@>@; +@<Global variables@>@; +@# +static void initialize(void) /*this procedure gets things started properly*/ + {@+@<Local variables for initialization@>@; + @<Initialize whatever \TeX\ might access@>; + } @# +@<Basic printing procedures@>@; +@<Error handling procedures@>@; + +@ The overall \TeX\ program begins with the heading just shown, after which +comes a bunch of procedure declarations and function declarations. +Finally we will get to the main program, which begins with the +comment `|start_here|'. If you want to skip down to the +main program now, you can look up `|start_here|' in the index. +But the author suggests that the best way to understand this program +is to follow pretty much the order of \TeX's components as they appear in the +\.{WEB} description you are now reading, since the present ordering is +intended to combine the advantages of the ``bottom up'' and ``top down'' +approaches to the problem of understanding a somewhat complicated system. + +@ There is no need to declare labels in \CEE/. + +@ Some of the code below is intended to be used only when diagnosing the +strange behavior that sometimes occurs when \TeX\ is being installed or +when system wizards are fooling around with \TeX\ without quite knowing +what they are doing. Such code will not normally be compiled; it is +delimited by the codewords `$|@t\#\&{ifdef} \.{DEBUG}@>|\ldots|@t\#\&{endif}@>|$', with apologies +to people who wish to preserve the purity of English. + +Similarly, there is some conditional code delimited by +`$|@t\#\&{ifdef} \.{STAT}@>|\ldots|@t\#\&{endif}@>|$' that is intended for use when statistics are to be +kept about \TeX's memory usage. The |@t\#\&{ifdef} \.{STAT}@>| $\ldots$ |@t\#\&{endif}@>| code also +implements diagnostic information for \.{\\tracingparagraphs}, +\.{\\tracingpages}, and \.{\\tracingrestores}. +@^debugging@> + +@ This program has two important variations: (1) There is a long and slow +version called \.{INITEX}, which does the extra calculations needed to +@.INITEX@> +initialize \TeX's internal tables; and (2)~there is a shorter and faster +production version, which cuts the initialization to a bare minimum. +Parts of the program that are needed in (1) but not in (2) are delimited by +the codewords `$|@t\#\&{ifdef} \.{INIT}@>|\ldots|@t\#\&{endif}@>|$'. + +\TeX\ Live has established the common practice +to select the initialization code at runtime +using the |iniversion| variable. + +@<Initialize whatever...@>= +@<Set initial values of key variables@>@/ +#ifdef @!INIT +if (iniversion) /* \TeX\ Live*/ + {@+@<Initialize table entries (done by \.{INITEX} only)@>@;@+} +#endif + +@ The declaration of the necessary type definitions are +contained in header files. + + +@<Header files and function declarations@>= +#include <stdbool.h> +#include <string.h> +#include <math.h> + +@ Further it is necessary to define some build in primitives of +\PASCAL\ that are otherwise not available in~\CEE/. +@:PASCAL H}{\ph@> + +@d odd(X) ((X)&1) +@d chr(X) ((unsigned char)(X)) +@d ord(X) ((unsigned int)(X)) +@d abs(X) ((X)>-(X)?(X):-(X)) +@d round(X) ((int)((X)>=0.0?floor((X)+0.5):ceil((X)-0.5))) + +@ The following parameters can be changed at compile time to extend or +reduce \TeX's capacity. They may have different values in \.{INITEX} and +in production versions of \TeX. +@.INITEX@> +@^system dependencies@> + +@<Constants...@>= +@!mem_max=5000000, /*greatest index in \TeX's internal |mem| array; + must be strictly less than |max_halfword|; + must be equal to |mem_top| in \.{INITEX}, otherwise | >= mem_top|*/ +@!mem_min=0, /*smallest index in \TeX's internal |mem| array; + must be |min_halfword| or more; + must be equal to |mem_bot| in \.{INITEX}, otherwise | <= mem_bot|*/ +@!buf_size=2000000, /*maximum number of characters simultaneously present in + current lines of open files and in control sequences between + \.{\\csname} and \.{\\endcsname}; must not exceed |max_halfword|*/ +@!error_line=79, /*width of context lines on terminal error messages*/ +@!half_error_line=50, /*width of first lines of contexts in terminal + error messages; should be between 30 and |error_line-15|*/ +@!max_print_line=79, /*width of longest text lines output; should be at least 60*/ +@!stack_size=5000, /*maximum number of simultaneous input sources*/ +@!max_in_open=15, /*maximum number of input files and error insertions that + can be going on simultaneously*/ +@!font_max=255, /*maximum internal font number; must not exceed |max_quarterword| + and must be at most |font_base+256|*/ +@!font_mem_size=8000000, /*number of words of |font_info| for all fonts*/ +@!param_size=10000, /*maximum number of simultaneous macro parameters*/ +@!nest_size=500, /*maximum number of semantic levels simultaneously active*/ +@!max_strings=500000, /*maximum number of strings; must not exceed |max_halfword|*/ +@!string_vacancies=90000, /*the minimum number of characters that should be + available for the user's control sequences and font names, + after \TeX's own error messages are stored*/ +@!pool_size=6250000, /*maximum number of characters in strings, including all + error messages and help texts, and the names of all fonts and + control sequences; must exceed |string_vacancies| by the total + length of \TeX's own strings, which is currently about 23000*/ +@!save_size=100000, /*space for saving values outside of current group; must be + at most |max_halfword|*/ +@!trie_size=1000000, /*space for hyphenation patterns; should be larger for + \.{INITEX} than it is in production versions of \TeX*/ +@!trie_op_size=35111, /*space for ``opcodes'' in the hyphenation patterns*/ +@!dvi_buf_size=16384, /*size of the output buffer; must be a multiple of 8*/ +@!file_name_size=1024, /*file names shouldn't be longer than this*/ +@!xchg_buffer_size=64, /*must be at least 64*/ + /*size of |eight_bits| buffer for exchange with system routines*/ + +@ Like the preceding parameters, the following quantities can be changed +at compile time to extend or reduce \TeX's capacity. But if they are changed, +it is necessary to rerun the initialization program \.{INITEX} +@.INITEX@> +to generate new tables for the production \TeX\ program. +One can't simply make helter-skelter changes to the following constants, +since certain rather complex initialization +numbers are computed from them. They are defined here using +\.{WEB} macros, instead of being put into the above |enum| list in order to +emphasize this distinction. + +@d mem_bot 0 /*smallest index in the |mem| array dumped by \.{INITEX}; + must not be less than |mem_min|*/ +@d mem_top 5000000 /*largest index in the |mem| array dumped by \.{INITEX}; + must be substantially larger than |mem_bot| + and not greater than |mem_max|*/ +@d font_base 0 /*smallest internal font number; must not be less + than |min_quarterword|*/ +@d hash_size 45000 /*maximum number of control sequences; it should be at most + about |(mem_max-mem_min)/(double)10|*/ +@d hash_prime 35999 /*a prime number equal to about 85\pct! of |hash_size|*/ +@d hyph_size 8191 /*another prime; the number of \.{\\hyphenation} exceptions*/ +@^system dependencies@> + +@ In case somebody has inadvertently made bad settings of the ``constants,'' +\TeX\ checks them using a global variable called |bad|. + +This is the first of many sections of \TeX\ where global variables are +defined. + +@<Glob...@>= +static int @!bad; /*is some ``constant'' wrong?*/ + +@ Later on we will say `\ignorespaces|if (mem_max >= max_halfword) bad=14|', +or something similar. (We can't do that until |max_halfword| has been defined.) + +@<Check the ``constant'' values for consistency@>= +bad=0; +if ((half_error_line < 30)||(half_error_line > error_line-15)) bad=1; +if (max_print_line < 60) bad=2; +if (dvi_buf_size%8!=0) bad=3; +if (mem_bot+1100 > mem_top) bad=4; +if (hash_prime > hash_size) bad=5; +if (max_in_open >= 128) bad=6; +if (mem_top < 256+11) bad=7; /*we will want |null_list > 255|*/ + +@ Labels are given symbolic names by the following definitions, so that +occasional |goto| statements will be meaningful. We insert the label +`|end|' just before the `\ignorespaces|} |\unskip' of a procedure in +which we have used the `|goto end|' statement defined below; the label +`|restart|' is occasionally used at the very beginning of a procedure; and +the label `|reswitch|' is occasionally used just prior to a |case| +statement in which some cases change the conditions and we wish to branch +to the newly applicable case. Loops that are set up with the |loop| +construction defined below are commonly exited by going to `|done|' or to +`|found|' or to `|not_found|', and they are sometimes repeated by going to +`|resume|'. If two or more parts of a subroutine start differently but +end up the same, the shared code may be gathered together at +`|common_ending|'. + +Incidentally, this program never declares a label that isn't actually used, +because some fussy \PASCAL\ compilers will complain about redundant labels. + +@ Here are some macros for common programming idioms. + +@d incr(A) A=A+1 /*increase a variable by unity*/ +@d decr(A) A=A-1 /*decrease a variable by unity*/ +@d negate(A) A=-A /*change the sign of a variable*/ +@d loop @+while (true) @+ /*repeat over and over until a |goto| happens*/ +@f loop else + /*\.{WEB}'s |else| acts like `\ignorespaces|while true do|\unskip'*/ +@d do_nothing /*empty statement*/ +@d empty 0 /*symbolic name for a null constant*/ + +@* The character set. +In order to make \TeX\ readily portable to a wide variety of +computers, all of its input text is converted to an internal eight-bit +code that includes standard ASCII, the ``American Standard Code for +Information Interchange.'' This conversion is done immediately when each +character is read in. Conversely, characters are converted from ASCII to +the user's external representation just before they are output to a +text file. + +Such an internal code is relevant to users of \TeX\ primarily because it +governs the positions of characters in the fonts. For example, the +character `\.A' has ASCII code $65=0101$, and when \TeX\ typesets +this letter it specifies character number 65 in the current font. +If that font actually has `\.A' in a different position, \TeX\ doesn't +know what the real position is; the program that does the actual printing from +\TeX's device-independent files is responsible for converting from ASCII to +a particular font encoding. +@^ASCII code@> + +\TeX's internal code also defines the value of constants +that begin with a reverse apostrophe; and it provides an index to the +\.{\\catcode}, \.{\\mathcode}, \.{\\uccode}, \.{\\lccode}, and \.{\\delcode} +tables. + +@ Characters of text that have been converted to \TeX's internal form +are said to be of type |ASCII_code|, which is a subrange of the integers. + +@<Types...@>= +typedef uint8_t ASCII_code; /*eight-bit numbers*/ + +@ The original \PASCAL\ compiler was designed in the late 60s, when six-bit +character sets were common, so it did not make provision for lowercase +letters. Nowadays, of course, we need to deal with both capital and small +letters in a convenient way, especially in a program for typesetting; +so the present specification of \TeX\ has been written under the assumption +that the \PASCAL\ compiler and run-time system permit the use of text files +with more than 64 distinguishable characters. More precisely, we assume that +the character set contains at least the letters and symbols associated +with ASCII codes 040 through 0176; all of these characters are now +available on most computer terminals. + +Since we are dealing with more characters than were present in the first +\PASCAL\ compilers, we have to decide what to call the associated data +type. Some \PASCAL s use the original name |unsigned char| for the +characters in text files, even though there now are more than 64 such +characters, while other \PASCAL s consider |unsigned char| to be a 64-element +subrange of a larger data type that has some other name. + +In order to accommodate this difference, we shall use the name |text_char| +to stand for the data type of the characters that are converted to and +from |ASCII_code| when they are input and output. We shall also assume +that |text_char| consists of the elements |chr(first_text_char)| through +|chr(last_text_char)|, inclusive. The following definitions should be +adjusted if necessary. +@^system dependencies@> + +@s text_char char +@d text_char unsigned char /*the data type of characters in text files*/ +@d first_text_char 0 /*ordinal number of the smallest element of |text_char|*/ +@d last_text_char 255 /*ordinal number of the largest element of |text_char|*/ + +@<Local variables for init...@>= +int @!i; + +@ The \TeX\ processor converts between ASCII code and +the user's external character set by means of arrays |xord| and |xchr| +that are analogous to \PASCAL's |ord| and |chr| functions. + +@<Glob...@>= +static ASCII_code @!xord[256]; + /*specifies conversion of input characters*/ +static text_char @!xchr[256]; + /*specifies conversion of output characters*/ + +@ Since we are assuming that our \PASCAL\ system is able to read and +write the visible characters of standard ASCII (although not +necessarily using the ASCII codes to represent them), the following +assignment statements initialize the standard part of the |xchr| array +properly, without needing any system-dependent changes. On the other +hand, it is possible to implement \TeX\ with less complete character +sets, and in such cases it will be necessary to change something here. +@^system dependencies@> + +@<Set init...@>= +xchr[040]=' '; +xchr[041]='!'; +xchr[042]='"'; +xchr[043]='#'; +xchr[044]='$'; +xchr[045]='%'; +xchr[046]='&'; +xchr[047]='\'';@/ +xchr[050]='('; +xchr[051]=')'; +xchr[052]='*'; +xchr[053]='+'; +xchr[054]=','; +xchr[055]='-'; +xchr[056]='.'; +xchr[057]='/';@/ +xchr[060]='0'; +xchr[061]='1'; +xchr[062]='2'; +xchr[063]='3'; +xchr[064]='4'; +xchr[065]='5'; +xchr[066]='6'; +xchr[067]='7';@/ +xchr[070]='8'; +xchr[071]='9'; +xchr[072]=':'; +xchr[073]=';'; +xchr[074]='<'; +xchr[075]='='; +xchr[076]='>'; +xchr[077]='?';@/ +xchr[0100]='@@'; +xchr[0101]='A'; +xchr[0102]='B'; +xchr[0103]='C'; +xchr[0104]='D'; +xchr[0105]='E'; +xchr[0106]='F'; +xchr[0107]='G';@/ +xchr[0110]='H'; +xchr[0111]='I'; +xchr[0112]='J'; +xchr[0113]='K'; +xchr[0114]='L'; +xchr[0115]='M'; +xchr[0116]='N'; +xchr[0117]='O';@/ +xchr[0120]='P'; +xchr[0121]='Q'; +xchr[0122]='R'; +xchr[0123]='S'; +xchr[0124]='T'; +xchr[0125]='U'; +xchr[0126]='V'; +xchr[0127]='W';@/ +xchr[0130]='X'; +xchr[0131]='Y'; +xchr[0132]='Z'; +xchr[0133]='['; +xchr[0134]='\\'; +xchr[0135]=']'; +xchr[0136]='^'; +xchr[0137]='_';@/ +xchr[0140]='`'; +xchr[0141]='a'; +xchr[0142]='b'; +xchr[0143]='c'; +xchr[0144]='d'; +xchr[0145]='e'; +xchr[0146]='f'; +xchr[0147]='g';@/ +xchr[0150]='h'; +xchr[0151]='i'; +xchr[0152]='j'; +xchr[0153]='k'; +xchr[0154]='l'; +xchr[0155]='m'; +xchr[0156]='n'; +xchr[0157]='o';@/ +xchr[0160]='p'; +xchr[0161]='q'; +xchr[0162]='r'; +xchr[0163]='s'; +xchr[0164]='t'; +xchr[0165]='u'; +xchr[0166]='v'; +xchr[0167]='w';@/ +xchr[0170]='x'; +xchr[0171]='y'; +xchr[0172]='z'; +xchr[0173]='{'; +xchr[0174]='|'; +xchr[0175]='}'; +xchr[0176]='~';@/ + +@ Some of the ASCII codes without visible characters have been given symbolic +names in this program because they are used with a special meaning. + +@d null_code 00 /*ASCII code that might disappear*/ +@d carriage_return 015 /*ASCII code used at end of line*/ +@d invalid_code 0177 /*ASCII code that many systems prohibit in text files*/ + +@ The ASCII code is ``standard'' only to a certain extent, since many +computer installations have found it advantageous to have ready access +to more than 94 printing characters. Appendix~C of {\sl The \TeX book\/} +gives a complete specification of the intended correspondence between +characters and \TeX's internal representation. +@:TeXbook}{\sl The \TeX book@> + +If \TeX\ is being used +on a garden-variety \PASCAL\ for which only standard ASCII +codes will appear in the input and output files, it doesn't really matter +what codes are specified in |xchr[0 dotdot 037]|, but the safest policy is to +blank everything out by using the code shown below. + +However, other settings of |xchr| will make \TeX\ more friendly on +computers that have an extended character set, so that users can type things +like `\.^^Z' instead of `\.{\\ne}'. People with extended character sets can +assign codes arbitrarily, giving an |xchr| equivalent to whatever +characters the users of \TeX\ are allowed to have in their input files. +It is best to make the codes correspond to the intended interpretations as +shown in Appendix~C whenever possible; but this is not necessary. For +example, in countries with an alphabet of more than 26 letters, it is +usually best to map the additional letters into codes less than~040. +To get the most ``permissive'' character set, change |' '| on the +right of these assignment statements to |chr(i)|. +@^character set dependencies@> +@^system dependencies@> + +@<Set init...@>= +for (i=0; i<=037; i++) xchr[i]=chr(i); /* \TeX\ Live*/ +for (i=0177; i<=0377; i++) xchr[i]=chr(i); /* \TeX\ Live*/ + +@ The following system-independent code makes the |xord| array contain a +suitable inverse to the information in |xchr|. Note that if |xchr[i]==xchr[j]| +where |i < j < 0177|, the value of |xord[xchr[i]]| will turn out to be +|j| or more; hence, standard ASCII code numbers will be used instead of +codes below 040 in case there is a coincidence. + +@<Set init...@>= +for (i=first_text_char; i<=last_text_char; i++) xord[chr(i)]=invalid_code; +for (i=0200; i<=0377; i++) xord[xchr[i]]=i; +for (i=0; i<=0176; i++) xord[xchr[i]]=i; + +@* Input and output. +The bane of portability is the fact that different operating systems treat +input and output quite differently, perhaps because computer scientists +have not given sufficient attention to this problem. People have felt somehow +that input and output are not part of ``real'' programming. Well, it is true +that some kinds of programming are more fun than others. With existing +input/output conventions being so diverse and so messy, the only sources of +joy in such parts of the code are the rare occasions when one can find a +way to make the program a little less bad than it might have been. We have +two choices, either to attack I/O now and get it over with, or to postpone +I/O until near the end. Neither prospect is very attractive, so let's +get it over with. + +The basic operations we need to do are (1)~inputting and outputting of +text, to or from a file or the user's terminal; (2)~inputting and +outputting of eight-bit bytes, to or from a file; (3)~instructing the +operating system to initiate (``open'') or to terminate (``close'') input or +output from a specified file; (4)~testing whether the end of an input +file has been reached. + +\TeX\ needs to deal with two kinds of files. +We shall use the term |alpha_file| for a file that contains textual data, +and the term |byte_file| for a file that contains eight-bit binary information. +These two types turn out to be the same on many computers, but +sometimes there is a significant distinction, so we shall be careful to +distinguish between them. Standard protocols for transferring +such files from computer to computer, via high-speed networks, are +now becoming available to more and more communities of users. + +The program actually makes use also of a third kind of file, called a +|word_file|, when dumping and reloading base information for its own +initialization. We shall define a word file later; but it will be possible +for us to specify simple operations on word files before they are defined. + +@<Types...@>= +typedef uint8_t eight_bits; /*unsigned one-byte quantity*/ +typedef struct {@+FILE *f;@+text_char@,d;@+} alpha_file; /*files that contain textual data*/ +typedef struct {@+FILE *f;@+eight_bits@,d;@+} byte_file; /*files that contain binary data*/ + +@ Most of what we need to do with respect to input and output can be handled +by the I/O facilities that are standard in \PASCAL, i.e., the routines +called |get|, |put|, |eof|, and so on. But +standard \PASCAL\ does not allow file variables to be associated with file +names that are determined at run time, so it cannot be used to implement +\TeX; some sort of extension to \PASCAL's ordinary |reset| and |rewrite| +is crucial for our purposes. We shall assume that |name_of_file| is a variable +of an appropriate type such that the \PASCAL\ run-time system being used to +implement \TeX\ can open a file whose external name is specified by +|name_of_file|. +@^system dependencies@> + +@<Glob...@>= +static unsigned char @!name_of_file0[file_name_size+1]={0}, + *const @!name_of_file = @!name_of_file0-1;@;@/ + /*on some systems this may be a \&{record} variable*/ +static int @!name_length;@/ /*this many characters are actually + relevant in |name_of_file| (the rest are blank)*/ + +@ To open files, \TeX\ used \PASCAL's |reset| function. +We use the {\tt kpathsearch} library to implement new functions +in the section on \TeX\ Live Integration. +Here we give only the function prototypes. + +\TeX's file-opening functions do not issue their own +error messages if something goes wrong. If a file identified by +|name_of_file| cannot be found, +or if such a file cannot be opened for some other reason +(e.g., someone may already be trying to write the same file) +\TeX's file-opening functions return |false|. +This allows \TeX\ to undertake appropriate corrective action. +@^system dependencies@> + +@p +static FILE*open_in(char*filename,kpse_file_format_type t,const char*rwb); /* \TeX\ Live*/ +static bool a_open_in(alpha_file *f); /*open a text file for input*/ +static bool b_open_in(byte_file *f); /*open a binary file for input*/ +static bool w_open_in(word_file *f); /*open a word file for input*/ +static FILE *open_out(const char *file_name, const char *file_mode); /* \TeX\ Live*/ +static bool a_open_out(alpha_file *f); /*open a text file for output*/ +static bool b_open_out(byte_file *f); /*open a binary file for output*/ +#ifdef @!INIT +static bool w_open_out(word_file *f); /*open a word file for output*/ +#endif + +@ Files can be closed with the \ph\ routine `|pascal_close(f)|', which +@:PASCAL H}{\ph@> +@^system dependencies@> +should be used when all input or output with respect to |f| has been completed. +This makes |f| available to be opened again, if desired; and if |f| was used for +output, the |pascal_close| operation makes the corresponding external file appear +on the user's area, ready to be read. + +These procedures should not generate error messages if a file is +being closed before it has been successfully opened. + +@p static void a_close(alpha_file *f) /*close a text file*/ +{@+pascal_close((*f)); +} +@# +static void b_close(byte_file *f) /*close a binary file*/ +{@+pascal_close((*f)); +} +@# +static void w_close(word_file *f) /*close a word file*/ +{@+pascal_close((*f)); +} + +@ Binary input and output are done with \PASCAL's ordinary |get| and |put| +procedures, so we don't have to make any other special arrangements for +binary~I/O. Text output is also easy to do with standard \PASCAL\ routines. +The treatment of text input is more difficult, however, because +of the necessary translation to |ASCII_code| values. +\TeX's conventions should be efficient, and they should +blend nicely with the user's operating environment. + +@ Input from text files is read one line at a time, using a routine called +|input_ln|. This function is defined in terms of global variables called +|buffer|, |first|, and |last| that will be described in detail later; for +now, it suffices for us to know that |buffer| is an array of |ASCII_code| +values, and that |first| and |last| are indices into this array +representing the beginning and ending of a line of text. + +@<Glob...@>= +static ASCII_code @!buffer[buf_size+1]; /*lines of characters being read*/ +static int @!first; /*the first unused position in |buffer|*/ +static int @!last; /*end of the line just input to |buffer|*/ +static int @!max_buf_stack; /*largest index used in |buffer|*/ + +@ The |input_ln| function brings the next line of input from the specified +file into available positions of the buffer array and returns the value +|true|, unless the file has already been entirely read, in which case it +returns |false| and sets |last=first|. In general, the |ASCII_code| +numbers that represent the next line of the file are input into +|buffer[first]|, |buffer[first+1]|, \dots, |buffer[last-1]|; and the +global variable |last| is set equal to |first| plus the length of the +line. Trailing blanks are removed from the line; thus, either |last==first| +(in which case the line was entirely blank) or |buffer[last-1]!=' '|. + +An overflow error is given, however, if the normal actions of |input_ln| +would make |last >= buf_size|; this is done so that other parts of \TeX\ +can safely look at the contents of |buffer[last+1]| without overstepping +the bounds of the |buffer| array. Upon entry to |input_ln|, the condition +|first < buf_size| will always hold, so that there is always room for an +``empty'' line. + +The variable |max_buf_stack|, which is used to keep track of how large +the |buf_size| parameter must be to accommodate the present job, is +also kept up to date by |input_ln|. + +If the |bypass_eoln| parameter is |true|, |input_ln| will do a |get| +before looking at the first character of the line; this skips over +an |eoln| that was in |f.d|. The procedure does not do a |get| when it +reaches the end of the line; therefore it can be used to acquire input +from the user's terminal as well as from ordinary text files. + +Standard \PASCAL\ says that a file should have |eoln| immediately +before |eof|, but \TeX\ needs only a weaker restriction: If |eof| +occurs in the middle of a line, the system function |eoln| should return +a |true| result (even though |f.d| will be undefined). + +Since the inner loop of |input_ln| is part of \TeX's ``inner loop''---each +character of input comes in at this place---it is wise to reduce system +overhead by making use of special routines that read in an entire array +of characters at once, if such routines are available. The following +code uses standard \PASCAL\ to illustrate what needs to be done, but +finer tuning is often possible at well-developed \PASCAL\ sites. +@^inner loop@> + +@p static bool input_ln(alpha_file *f, bool @!bypass_eoln) + /*inputs the next line or returns |false|*/ +{@+int last_nonblank; /*|last| with trailing blanks removed*/ +if (bypass_eoln) if (!eof((*f))) get((*f)); + /*input the first character of the line into |f.d|*/ +last=first; /*cf.\ Matthew 19\thinspace:\thinspace30*/ +if (eof((*f))) return false; +else{@+last_nonblank=first; + while (!eoln((*f))) + {@+if (last >= max_buf_stack) + {@+max_buf_stack=last+1; + if (max_buf_stack==buf_size) + @<Report overflow of the input buffer, and abort@>; + } + buffer[last]=xord[(*f).d];get((*f));incr(last); + if (buffer[last-1]!=' ') last_nonblank=last; + } + last=last_nonblank;return true; + } +} + +@ The user's terminal acts essentially like other files of text, except +that it is used both for input and for output. When the terminal is +considered an input file, the file variable is called |term_in|, and when it +is considered an output file the file variable is |term_out|. +@^system dependencies@> + +@<Glob...@>= +static alpha_file @!term_in; /*the terminal as an input file*/ +static alpha_file @!term_out; /*the terminal as an output file*/ + +@ Here is how to open the terminal files +in \ph. The `\.{/I}' switch suppresses the first |get|. +@:PASCAL H}{\ph@> +@^system dependencies@> + +@d t_open_in term_in.f=stdin /*open the terminal for text input*/ +@d t_open_out term_out.f=stdout /*open the terminal for text output*/ + +@ Sometimes it is necessary to synchronize the input/output mixture that +happens on the user's terminal, and three system-dependent +procedures are used for this +purpose. The first of these, |update_terminal|, is called when we want +to make sure that everything we have output to the terminal so far has +actually left the computer's internal buffers and been sent. +The second, |clear_terminal|, is called when we wish to cancel any +input that the user may have typed ahead (since we are about to +issue an unexpected error message). The third, |wake_up_terminal|, +is supposed to revive the terminal if the user has disabled it by +some instruction to the operating system. The following macros show how +these operations can be specified in \ph: +@:PASCAL H}{\ph@> +@^system dependencies@> + +@d update_terminal fflush(term_out.f) /*empty the terminal output buffer*/ +@d clear_terminal fflush(term_in.f) /*clear the terminal input buffer*/ +@d wake_up_terminal do_nothing /*cancel the user's cancellation of output*/ + +@ We need a special routine to read the first line of \TeX\ input from +the user's terminal. This line is different because it is read before we +have opened the transcript file; there is sort of a ``chicken and +egg'' problem here. If the user types `\.{\\input paper}' on the first +line, or if some macro invoked by that line does such an \.{\\input}, +the transcript file will be named `\.{paper.log}'; but if no \.{\\input} +commands are performed during the first line of terminal input, the transcript +file will acquire its default name `\.{texput.log}'. (The transcript file +will not contain error messages generated by the first line before the +first \.{\\input} command.) +@.texput@> + +The first line is even more special if we are lucky enough to have an operating +system that treats \TeX\ differently from a run-of-the-mill \PASCAL\ object +program. It's nice to let the user start running a \TeX\ job by typing +a command line like `\.{tex paper}'; in such a case, \TeX\ will operate +as if the first line of input were `\.{paper}', i.e., the first line will +consist of the remainder of the command line, after the part that invoked +\TeX. + +The first line is special also because it may be read before \TeX\ has +input a format file. In such cases, normal error messages cannot yet +be given. The following code uses concepts that will be explained later. +(If the \PASCAL\ compiler does not support non-local |@!goto|\unskip, the +@^system dependencies@> +statement `|goto exit(0)|' should be replaced by something that +quietly terminates the program.) + +@<Report overflow of the input buffer, and abort@>= +if (format_ident==0) + {@+write_ln(term_out,"Buffer size exceeded!");exit(0); +@.Buffer size exceeded@> + } +else{@+cur_input.loc_field=first;cur_input.limit_field=last-1; + overflow("buffer size", buf_size); +@:TeX capacity exceeded buffer size}{\quad buffer size@> + } + +@ Different systems have different ways to get started. But regardless of +what conventions are adopted, the routine that initializes the terminal +should satisfy the following specifications: + +\yskip\textindent{1)}It should open file |term_in| for input from the + terminal. (The file |term_out| will already be open for output to the + terminal.) + +\textindent{2)}If the user has given a command line, this line should be + considered the first line of terminal input. Otherwise the + user should be prompted with `\.{**}', and the first line of input + should be whatever is typed in response. + +\textindent{3)}The first line of input, which might or might not be a + command line, should appear in locations |first| to |last-1| of the + |buffer| array. + +\textindent{4)}The global variable |loc| should be set so that the + character to be read next by \TeX\ is in |buffer[loc]|. This + character should not be blank, and we should have |loc < last|. + +\yskip\noindent(It may be necessary to prompt the user several times +before a non-blank line comes in. The prompt is `\.{**}' instead of the +later `\.*' because the meaning is slightly different: `\.{\\input}' need +not be typed immediately after~`\.{**}'.) + +@d loc cur_input.loc_field /*location of first unread character in |buffer|*/ + +@ The following routine calls |input_command_line| +to retrieve a possible command line. +@^system dependencies@> + +@p static bool init_terminal(void) /*gets the terminal input started*/ +{@+ +t_open_in; +if (input_command_line()) return true; /* \TeX\ Live */ +loop@+{@+wake_up_terminal;pascal_write(term_out,"**");update_terminal; +@.**@> + if (!input_ln(&term_in, true)) /*this shouldn't happen*/ + {@+write_ln(term_out); + pascal_write(term_out,"! End of file on the terminal... why?"); +@.End of file on the terminal@> + return false; + } + loc=first; + while ((loc < last)&&(buffer[loc]==' ')) incr(loc); + if (loc < last) + {@+return true; + /*return unless the line was all blank*/ + } + write_ln(term_out,"Please type the name of your input file."); + } +} + +@* String handling. +Control sequence names and diagnostic messages are variable-length strings +of eight-bit characters. Since \PASCAL\ does not have a well-developed string +mechanism, \TeX\ does all of its string processing by homegrown methods. + +Elaborate facilities for dynamic strings are not needed, so all of the +necessary operations can be handled with a simple data structure. +The array |str_pool| contains all of the (eight-bit) ASCII codes in all +of the strings, and the array |str_start| contains indices of the starting +points of each string. Strings are referred to by integer numbers, so that +string number |s| comprises the characters |str_pool[j]| for +|str_start[s] <= j < str_start[s+1]|. Additional integer variables +|pool_ptr| and |str_ptr| indicate the number of entries used so far +in |str_pool| and |str_start|, respectively; locations +|str_pool[pool_ptr]| and |str_start[str_ptr]| are +ready for the next string to be allocated. + +String numbers 0 to 255 are reserved for strings that correspond to single +ASCII characters. This is in accordance with the conventions of \.{WEB}, +@.WEB@> +which converts single-character strings into the ASCII code number of the +single character involved, while it converts other strings into integers +and builds a string pool file. Thus, when the string constant \.{"."} appears +in the program below, \.{WEB} converts it into the integer 46, which is the +ASCII code for a period, while \.{WEB} will convert a string like \.{"hello"} +into some integer greater than~255. String number 46 will presumably be the +single character `\..'; but some ASCII codes have no standard visible +representation, and \TeX\ sometimes needs to be able to print an arbitrary +ASCII character, so the first 256 strings are used to specify exactly what +should be printed for each of the 256 possibilities. + +Elements of the |str_pool| array must be ASCII codes that can actually +be printed; i.e., they must have an |xchr| equivalent in the local +character set. (This restriction applies only to preloaded strings, +not to those generated dynamically by the user.) + +Some \PASCAL\ compilers won't pack integers into a single byte unless the +integers lie in the range |-128 dotdot 127|. To accommodate such systems +we access the string pool only via macros that can easily be redefined. +@^system dependencies@> + +@d si(A) A /*convert from |ASCII_code| to |packed_ASCII_code|*/ +@d so(A) A /*convert from |packed_ASCII_code| to |ASCII_code|*/ + +@<Types...@>= +typedef int32_t pool_pointer; /*for variables that point into |str_pool|*/ +typedef int32_t str_number; /*for variables that point into |str_start|*/ +typedef uint8_t packed_ASCII_code; /*elements of |str_pool| array*/ + +@ @<Glob...@>= +static packed_ASCII_code @!str_pool[pool_size+1]; /*the characters*/ +static pool_pointer @!str_start[max_strings+1]; /*the starting pointers*/ +static pool_pointer @!pool_ptr; /*first unused position in |str_pool|*/ +static str_number @!str_ptr; /*number of the current string being created*/ +static pool_pointer @!init_pool_ptr; /*the starting value of |pool_ptr|*/ +static str_number @!init_str_ptr; /*the starting value of |str_ptr|*/ + +@ Several of the elementary string operations are performed using \.{WEB} +macros instead of \PASCAL\ procedures, because many of the +operations are done quite frequently and we want to avoid the +overhead of procedure calls. For example, here is +a simple macro that computes the length of a string. +@.WEB@> + +@d length(A) (str_start[A+1]-str_start[A]) /*the number of characters + in string number \#*/ + +@ The length of the current string is called |cur_length|: + +@d cur_length (pool_ptr-str_start[str_ptr]) + +@ Strings are created by appending character codes to |str_pool|. +The |append_char| macro, defined here, does not check to see if the +value of |pool_ptr| has gotten too high; this test is supposed to be +made before |append_char| is used. There is also a |flush_char| +macro, which erases the last character appended. + +To test if there is room to append |l| more characters to |str_pool|, +we shall write |str_room(l)|, which aborts \TeX\ and gives an +apologetic error message if there isn't enough room. + +@d append_char(A) /*put |ASCII_code| \# at the end of |str_pool|*/ +{@+str_pool[pool_ptr]=si(A);incr(pool_ptr); +} +@d flush_char decr(pool_ptr) /*forget the last character in the pool*/ +@d str_room(A) /*make sure that the pool hasn't overflowed*/ + {@+if (pool_ptr+A > pool_size) + overflow("pool size", pool_size-init_pool_ptr); +@:TeX capacity exceeded pool size}{\quad pool size@> + } + +@ Once a sequence of characters has been appended to |str_pool|, it +officially becomes a string when the function |make_string| is called. +This function returns the identification number of the new string as its +value. + +@p static str_number make_string(void) /*current string enters the pool*/ +{@+if (str_ptr==max_strings) + overflow("number of strings", max_strings-init_str_ptr); +@:TeX capacity exceeded number of strings}{\quad number of strings@> +incr(str_ptr);str_start[str_ptr]=pool_ptr; +return str_ptr-1; +} + +@ To destroy the most recently made string, we say |flush_string|. + +@d flush_string {@+decr(str_ptr);pool_ptr=str_start[str_ptr]; + } + +@ The following subroutine compares string |s| with another string of the +same length that appears in |buffer| starting at position |k|; +the result is |true| if and only if the strings are equal. +Empirical tests indicate that |str_eq_buf| is used in such a way that +it tends to return |true| about 80 percent of the time. + +@p static bool str_eq_buf(str_number @!s, int @!k) + /*test equality of strings*/ +{@+ /*loop exit*/ +pool_pointer j; /*running index*/ +bool @!result; /*result of comparison*/ +j=str_start[s]; +while (j < str_start[s+1]) + {@+if (so(str_pool[j])!=buffer[k]) + {@+result=false;goto not_found; + } + incr(j);incr(k); + } +result=true; +not_found: return result; +} + +@ Here is a similar routine, but it compares two strings in the string pool, +and it does not assume that they have the same length. + +@p static bool str_eq_str(str_number @!s, str_number @!t) + /*test equality of strings*/ +{@+ /*loop exit*/ +pool_pointer j, @!k; /*running indices*/ +bool @!result; /*result of comparison*/ +result=false; +if (length(s)!=length(t)) goto not_found; +j=str_start[s];k=str_start[t]; +while (j < str_start[s+1]) + {@+if (str_pool[j]!=str_pool[k]) goto not_found; + incr(j);incr(k); + } +result=true; +not_found: return result; +} +@t\4@>@<Declare \Prote\ procedures for strings@>@; + +@ The initial values of |str_pool|, |str_start|, |pool_ptr|, +and |str_ptr| are computed by the \.{INITEX} program, based in part +on the information that \.{WEB} has output while processing \TeX. +@.INITEX@> +@^string pool@> + +@p +static bool get_strings_started(void) /*initializes the string pool*/ +{@+ +int k, @!l; /*small indices or counters*/ +pool_ptr=0;str_ptr=0;str_start[0]=0; +@<Make the first 256 strings@>; +@<Add the empty string to the string pool@>; +return true; +} + +@ @d app_lc_hex(A) l=A; + if (l < 10) append_char(l+'0')@;@+else append_char(l-10+'a') + +@<Make the first 256...@>= +for (k=0; k<=255; k++) + {@+if ((@<Character |k| cannot be printed@>)) + {@+append_char('^');append_char('^'); + if (k < 0100) append_char(k+0100)@; + else if (k < 0200) append_char(k-0100)@; + else{@+app_lc_hex(k/16);app_lc_hex(k%16); + } + } + else append_char(k); + make_string(); + } + +@ The first 128 strings will contain 95 standard ASCII characters, and the +other 33 characters will be printed in three-symbol form like `\.{\^\^A}' +unless a system-dependent change is made here. Installations that have +an extended character set, where for example |xchr[032]==@t\.{\'^^Z\'}@>|, +would like string 032 to be the single character 032 instead of the +three characters 0136, 0136, 0132 (\.{\^\^Z}). On the other hand, +even people with an extended character set will want to represent string +015 by \.{\^\^M}, since 015 is |carriage_return|; the idea is to +produce visible strings instead of tabs or line-feeds or carriage-returns +or bell-rings or characters that are treated anomalously in text files. + +Unprintable characters of codes 128--255 are, similarly, rendered +\.{\^\^80}--\.{\^\^ff}. + +The boolean expression defined here should be |true| unless \TeX\ +internal code number~|k| corresponds to a non-troublesome visible +symbol in the local character set. An appropriate formula for the +extended character set recommended in {\sl The \TeX book\/} would, for +example, be `|k in[0, 010 dotdot 012, 014, 015, 033, 0177 dotdot 0377]|'. +If character |k| cannot be printed, and |k < 0200|, then character |k+0100| or +|k-0100| must be printable; moreover, ASCII codes |[041 dotdot 046, +060 dotdot 071, 0136, 0141 dotdot 0146, 0160 dotdot 0171]| must be printable. +Thus, at least 80 printable characters are needed. +@:TeXbook}{\sl The \TeX book@> +@^character set dependencies@> +@^system dependencies@> + +@<Character |k| cannot be printed@>= + (k < ' ')||(k > '~') + +@ The |pool_file| variable is no longer needed and has been removed. + +Instead of reading the other strings from the \.{TEX.POOL} file, +it is sufficient here to add the empty string. +@<Add the empty string to the string pool@>= +make_string(); + +@ Without a string pool file there is no need for a pool check sum either. +But this is a convenient place to define the function |s_no| that will +add literal strings to the string pool at runtime, thereby obtaining their +string number. + +@p static int s_no(const char *str) +{@+ + if (str[0]==0) return empty_string; + if (str[1]==0) return str[0]; + str_room(strlen(str)); + while (*str!=0) append_char(*str++); + return make_string(); +} + +@ The function |s_no| is used in |initialize| and needs a forward +declaration. + +@<Forward declarations@>= +static int s_no(const char *str); + +@* On-line and off-line printing. +Messages that are sent to a user's terminal and to the transcript-log file +are produced by several `|print|' procedures. These procedures will +direct their output to a variety of places, based on the setting of +the global variable |selector|, which has the following possible +values: + +\yskip +\hang |term_and_log|, the normal setting, prints on the terminal and on the + transcript file. + +\hang |log_only|, prints only on the transcript file. + +\hang |term_only|, prints only on the terminal. + +\hang |no_print|, doesn't print at all. This is used only in rare cases + before the transcript file is open. + +\hang |pseudo|, puts output into a cyclic buffer that is used + by the |show_context| routine; when we get to that routine we shall discuss + the reasoning behind this curious mode. + +\hang |new_string|, appends the output to the current string in the + string pool. + +\hang 0 to 15, prints on one of the sixteen files for \.{\\write} output. + +\yskip +\noindent The symbolic names `|term_and_log|', etc., have been assigned +numeric codes that satisfy the convenient relations |no_print+1==term_only|, +|no_print+2==log_only|, |term_only+2==log_only+1==term_and_log|. + +Three additional global variables, |tally| and |term_offset| and +|file_offset|, record the number of characters that have been printed +since they were most recently cleared to zero. We use |tally| to record +the length of (possibly very long) stretches of printing; |term_offset| +and |file_offset|, on the other hand, keep track of how many characters +have appeared so far on the current line that has been output to the +terminal or to the transcript file, respectively. + +@d no_print 16 /*|selector| setting that makes data disappear*/ +@d term_only 17 /*printing is destined for the terminal only*/ +@d log_only 18 /*printing is destined for the transcript file only*/ +@d term_and_log 19 /*normal |selector| setting*/ +@d pseudo 20 /*special |selector| setting for |show_context|*/ +@d new_string 21 /*printing is deflected to the string pool*/ +@d max_selector 21 /*highest selector setting*/ + +@<Glob...@>= +static alpha_file @!log_file; /*transcript of \TeX\ session*/ +static int @!selector; /*where to print a message*/ +static int8_t @!dig[23]; /*digits in a number being output*/ +static int @!tally; /*the number of characters recently printed*/ +static int @!term_offset; + /*the number of characters on the current terminal line*/ +static int @!file_offset; + /*the number of characters on the current file line*/ +static ASCII_code @!trick_buf[error_line+1]; /*circular buffer for + pseudoprinting*/ +static int @!trick_count; /*threshold for pseudoprinting, explained later*/ +static int @!first_count; /*another variable for pseudoprinting*/ + +@ @<Initialize the output routines@>= +selector=term_only;tally=0;term_offset=0;file_offset=0; + +@ Macro abbreviations for output to the terminal and to the log file are +defined here for convenience. Some systems need special conventions +for terminal output, and it is possible to adhere to those conventions +by changing |wterm|, |wterm_ln|, and |wterm_cr| in this section. +@^system dependencies@> + +@<Basic printing procedures@>= +#define @[put(F)@] @[fwrite(&((F).d)@],@[sizeof((F).d),1,(F).f)@]@; +#define @[get(F)@] @[(void)!fread(&((F).d),sizeof((F).d),1,(F).f)@] + +#define @[pascal_close(F)@] @[fclose((F).f)@] +#define @[eof(F)@] @[feof((F).f)@] +#define @[eoln(F)@] @[((F).d=='\n'||eof(F))@] +#define @[erstat(F)@] @[((F).f==NULL?-1:ferror((F).f))@] + +#define @[pascal_read(F,X)@] @[((X)=(F).d,get(F))@] +#define @[read_ln(F)@] do get(F); while (!eoln(F)) + +#define @[pascal_write(F, FMT,...)@] @[fprintf(F.f,FMT,## __VA_ARGS__)@] +#define @[write_ln(F,...)@] @[pascal_write(F,__VA_ARGS__"\n")@] + +#define @[wterm(FMT,...)@] @[pascal_write(term_out,FMT, ## __VA_ARGS__)@] +#define @[wterm_ln(FMT,...)@] @[wterm(FMT "\n", ## __VA_ARGS__)@] +#define wterm_cr @[pascal_write(term_out,"\n")@] +#define @[wlog(FMT, ...)@] @[pascal_write(log_file,FMT, ## __VA_ARGS__)@] +#define @[wlog_ln(FMT, ...)@] @[wlog(FMT "\n", ## __VA_ARGS__)@] +#define wlog_cr @[pascal_write(log_file,"\n")@] + +@ To end a line of text output, we call |print_ln|. + +@<Basic print...@>= +static void print_ln(void) /*prints an end-of-line*/ +{@+switch (selector) { +case term_and_log: {@+wterm_cr;wlog_cr; + term_offset=0;file_offset=0; + } @+break; +case log_only: {@+wlog_cr;file_offset=0; + } @+break; +case term_only: {@+wterm_cr;term_offset=0; + } @+break; +case no_print: case pseudo: case new_string: do_nothing;@+break; +default:write_ln(write_file[selector]); +} @/ +} /*|tally| is not affected*/ + +@ The |print_char| procedure sends one character to the desired destination, +using the |xchr| array to map it into an external character compatible with +|input_ln|. All printing comes through |print_ln| or |print_char|. + +@<Basic printing...@>= +static void print_char(ASCII_code @!s) /*prints a single character*/ +{@+ +if (@<Character |s| is the current new-line character@>) + if (selector < pseudo) + {@+print_ln();return; + } +switch (selector) { +case term_and_log: {@+wterm("%c",xchr[s]);wlog("%c",xchr[s]); + incr(term_offset);incr(file_offset); + if (term_offset==max_print_line) + {@+wterm_cr;term_offset=0; + } + if (file_offset==max_print_line) + {@+wlog_cr;file_offset=0; + } + } @+break; +case log_only: {@+wlog("%c",xchr[s]);incr(file_offset); + if (file_offset==max_print_line) print_ln(); + } @+break; +case term_only: {@+wterm("%c",xchr[s]);incr(term_offset); + if (term_offset==max_print_line) print_ln(); + } @+break; +case no_print: do_nothing;@+break; +case pseudo: if (tally < trick_count) trick_buf[tally%error_line]=s;@+break; +case new_string: {@+if (pool_ptr < pool_size) append_char(s); + } @+break; /*we drop characters if the string space is full*/ +default:pascal_write(write_file[selector],"%c", xchr[s]); +} @/ +incr(tally); +} + +@ An entire string is output by calling |print|. Note that if we are outputting +the single standard ASCII character \.c, we could call |print('c')|, since +|'c'==99| is the number of a single-character string, as explained above. But +|print_char('c')| is quicker, so \TeX\ goes directly to the |print_char| +routine when it knows that this is safe. (The present implementation +assumes that it is always safe to print a visible ASCII character.) +@^system dependencies@> + +@<Basic print...@>= +static void print(char *s) /* the simple version */ +{ @+if (s == NULL) s="???"; /*this can't happen*/ + while (*s!=0) print_char(*s++);@+ +} + +static void printn(int @!s) /*prints string |s|*/ +{@+ +pool_pointer j; /*current character code position*/ +int @!nl; /*new-line character to restore*/ +if (s >= str_ptr) {print("???"); return;}/*this can't happen*/ +@.???@> +else if (s < 256) + if (s < 0) { print("???");return; } /*can't happen*/ + else{@+if (selector > pseudo) + {@+print_char(s);return; /*internal strings are not expanded*/ + } + if ((@<Character |s| is the current new-line character@>)) + if (selector < pseudo) + {@+print_ln();return; + } + nl=new_line_char;new_line_char=-1; + /*temporarily disable new-line character*/ + j=str_start[s]; + while (j < str_start[s+1]) + {@+print_char(so(str_pool[j]));incr(j); + } + new_line_char=nl;return; + } +j=str_start[s]; +while (j < str_start[s+1]) + {@+print_char(so(str_pool[j]));incr(j); + } +} + +@ Control sequence names, file names, and strings constructed with +\.{\\string} might contain |ASCII_code| values that can't +be printed using |print_char|. Therefore we use |slow_print| for them: + +@<Basic print...@>= +static void slow_print(int @!s) /*prints string |s|*/ +{@+pool_pointer j; /*current character code position*/ +if ((s >= str_ptr)||(s < 256)) printn(s); +else{@+j=str_start[s]; + while (j < str_start[s+1]) + {@+printn(so(str_pool[j]));incr(j); + } + } +} + +@ Here is the very first thing that \TeX\ prints: a headline that identifies +the version number and format package. The |term_offset| variable is temporarily +incorrect, but the discrepancy is not serious since we assume that this +part of the program is system dependent. +@^system dependencies@> + +According to the conventions of \TeX\ Live, + we print the |dump_name| if no format identifier is known. +@<Initialize the output...@>= +wterm("%s",banner); +if (format_ident==0) wterm_ln(" (preloaded format=%s)", dump_name); +else{@+slow_print(format_ident);print_ln(); + } +update_terminal; + +@ The procedure |print_nl| is like |print|, but it makes sure that the +string appears at the beginning of a new line. + +@<Basic print...@>= +static void print_nl(char *@!s) /*prints string |s| at beginning of line*/ +{@+if (((term_offset > 0)&&(odd(selector)))||@| + ((file_offset > 0)&&(selector >= log_only))) print_ln(); +print(s); +} + +@ The procedure |print_esc| prints a string that is preceded by +the user's escape character (which is usually a backslash). + +@<Basic print...@>= +static void printn_esc(str_number @!s) /*prints escape character, then |s|*/ +{@+int c; /*the escape character code*/ +@<Set variable |c| to the current escape character@>; +if (c >= 0) if (c < 256) printn(c); +slow_print(s); +} + +static void print_esc(char *@!s) /*the fast way*/ +{@+int c; /*the escape character code*/ +@<Set variable |c| to the current escape character@>; +if (c >= 0) if (c < 256) printn(c); +print(s); +} + +@ An array of digits in the range |0 dotdot 15| is printed by |print_the_digs|. + +@<Basic print...@>= +static void print_the_digs(eight_bits @!k) + /*prints |dig[k-1]|$\,\ldots\,$|dig[0]|*/ +{@+while (k > 0) + {@+decr(k); + if (dig[k] < 10) print_char('0'+dig[k]); + else print_char('A'-10+dig[k]); + } +} + +@ The following procedure, which prints out the decimal representation of a +given integer |n|, has been written carefully so that it works properly +if |n==0| or if |(-n)| would cause overflow. It does not apply |%| or |/| +to negative arguments, since such operations are not implemented consistently +by all \PASCAL\ compilers. + +@<Basic print...@>= +static void print_int(int @!n) /*prints an integer in decimal form*/ +{@+int k; /*index to current digit; we assume that $\vert n\vert<10^{23}$*/ +int @!m; /*used to negate |n| in possibly dangerous cases*/ +k=0; +if (n < 0) + {@+print_char('-'); + if (n > -100000000) negate(n); + else{@+m=-1-n;n=m/10;m=(m%10)+1;k=1; + if (m < 10) dig[0]=m; + else{@+dig[0]=0;incr(n); + } + } + } +@/do@+{dig[k]=n%10;n=n/10;incr(k); +}@+ while (!(n==0)); +print_the_digs(k); +} + +@ Here is a trivial procedure to print two digits; it is usually called with +a parameter in the range |0 <= n <= 99|. + +@p static void print_two(int @!n) /*prints two least significant digits*/ +{@+n=abs(n)%100;print_char('0'+(n/10)); +print_char('0'+(n%10)); +} + +@ Hexadecimal printing of nonnegative integers is accomplished by |print_hex|. + +@p static void print_hex(int @!n) + /*prints a positive integer in hexadecimal form*/ +{@+int k; /*index to current digit; we assume that $0\le n<16^{22}$*/ +k=0;print_char('"'); +@/do@+{dig[k]=n%16;n=n/16;incr(k); +}@+ while (!(n==0)); +print_the_digs(k); +} + +@ Old versions of \TeX\ needed a procedure called |print_ASCII| whose function +is now subsumed by |print|. We retain the old name here as a possible aid to +future software arch\ae ologists. + +@d print_ASCII printn + +@ Roman numerals are produced by the |print_roman_int| routine. Readers +who like puzzles might enjoy trying to figure out how this tricky code +works; therefore no explanation will be given. Notice that 1990 yields +\.{mcmxc}, not \.{mxm}. + +@p static void print_roman_int(int @!n) +{@+ +pool_pointer j, @!k; /*mysterious indices into |mystery|*/ +nonnegative_integer @!u, @!v; /*mysterious numbers*/ +const char mystery[] ="m2d5c2l5x2v5i"; +j=0;v=1000; +loop@+{@+while (n >= v) + {@+print_char(so(mystery[j]));n=n-v; + } + if (n <= 0) return; /*nonpositive input produces no output*/ + k=j+2;u=v/(so(mystery[k-1])-'0'); + if (mystery[k-1]==si('2')) + {@+k=k+2;u=u/(so(mystery[k-1])-'0'); + } + if (n+u >= v) + {@+print_char(so(mystery[k]));n=n+u; + } + else{@+j=j+2;v=v/(so(mystery[j-1])-'0'); + } + } +} + +@ The |print| subroutine will not print a string that is still being +created. The following procedure will. + +@p static void print_current_string(void) /*prints a yet-unmade string*/ +{@+pool_pointer j; /*points to current character code*/ +j=str_start[str_ptr]; +while (j < pool_ptr) + {@+print_char(so(str_pool[j]));incr(j); + } +} + +@ Here is a procedure that asks the user to type a line of input, +assuming that the |selector| setting is either |term_only| or |term_and_log|. +The input is placed into locations |first| through |last-1| of the +|buffer| array, and echoed on the transcript file if appropriate. + +This procedure is never called when |interaction < scroll_mode|. + +@d prompt_input(A) {@+wake_up_terminal;print(A);term_input(); + } /*prints a string and gets a line of input*/ + +@p static void term_input(void) /*gets a line from the terminal*/ +{@+int k; /*index into |buffer|*/ +update_terminal; /*now the user sees the prompt for sure*/ +if (!input_ln(&term_in, true)) fatal_error("End of file on the terminal!"); +@.End of file on the terminal@> +term_offset=0; /*the user's line ended with \<\rm return>*/ +decr(selector); /*prepare to echo the input*/ +if (last!=first) for (k=first; k<=last-1; k++) printn(buffer[k]); +print_ln();incr(selector); /*restore previous status*/ +} + +@* Reporting errors. +When something anomalous is detected, \TeX\ typically does something like this: +$$\vbox{\halign{#\hfil\cr +|print_err("Something anomalous has been detected");|\cr +|help3("This is the first line of my offer to help.")|\cr +|("This is the second line. I'm trying to")|\cr +|("explain the best way for you to proceed.");|\cr +|error;|\cr}}$$ +A two-line help message would be given using |help2|, etc.; these informal +helps should use simple vocabulary that complements the words used in the +official error message that was printed. (Outside the U.S.A., the help +messages should preferably be translated into the local vernacular. Each +line of help is at most 60 characters long, in the present implementation, +so that |max_print_line| will not be exceeded.) + +The |print_err| procedure supplies a `\.!' before the official message, +and makes sure that the terminal is awake if a stop is going to occur. +The |error| procedure supplies a `\..' after the official message, then it +shows the location of the error; and if |interaction==error_stop_mode|, +it also enters into a dialog with the user, during which time the help +message may be printed. +@^system dependencies@> + +@<Error handling...@>= +static void print_err(char *s) +{@+if (interaction==error_stop_mode) wake_up_terminal; + if (filelineerrorstylep) print_file_line(); /* \TeX\ Live */ + else print_nl("! "); + print(s); +} + +@ The global variable |interaction| has four settings, representing increasing +amounts of user interaction: + +@d batch_mode 0 /*omits all stops and omits terminal output*/ +@d nonstop_mode 1 /*omits all stops*/ +@d scroll_mode 2 /*omits error stops*/ +@d error_stop_mode 3 /*stops at every opportunity to interact*/ + +@<Glob...@>= +static int @!interaction; /*current level of interaction*/ + +@ @<Set init...@>= +if (interaction_option<0) interaction=error_stop_mode; +else interaction=interaction_option; /* \TeX\ Live */ + +@ \TeX\ is careful not to call |error| when the print |selector| setting +might be unusual. The only possible values of |selector| at the time of +error messages are + +\yskip\hang|no_print| (when |interaction==batch_mode| + and |log_file| not yet open); + +\hang|term_only| (when |interaction > batch_mode| and |log_file| not yet open); + +\hang|log_only| (when |interaction==batch_mode| and |log_file| is open); + +\hang|term_and_log| (when |interaction > batch_mode| and |log_file| is open). + +@<Initialize the print |selector| based on |interaction|@>= +if (interaction==batch_mode) selector=no_print;@+else selector=term_only + +@ A global variable |deletions_allowed| is set |false| if the |get_next| +routine is active when |error| is called; this ensures that |get_next| +and related routines like |get_token| will never be called recursively. +A similar interlock is provided by |set_box_allowed|. +@^recursion@> + +The global variable |history| records the worst level of error that +has been detected. It has four possible values: |spotless|, |warning_issued|, +|error_message_issued|, and |fatal_error_stop|. + +Another global variable, |error_count|, is increased by one when an +|error| occurs without an interactive dialog, and it is reset to zero at +the end of every paragraph. If |error_count| reaches 100, \TeX\ decides +that there is no point in continuing further. + +@d spotless 0 /*|history| value when nothing has been amiss yet*/ +@d warning_issued 1 /*|history| value when |begin_diagnostic| has been called*/ +@d error_message_issued 2 /*|history| value when |error| has been called*/ +@d fatal_error_stop 3 /*|history| value when termination was premature*/ + +@<Glob...@>= +static bool @!deletions_allowed; /*is it safe for |error| to call |get_token|?*/ +static bool @!set_box_allowed; /*is it safe to do a \.{\\setbox} assignment?*/ +static int @!history; /*has the source input been clean so far?*/ +static int @!error_count; /*the number of scrolled errors since the + last paragraph ended*/ + +@ The value of |history| is initially |fatal_error_stop|, but it will +be changed to |spotless| if \TeX\ survives the initialization process. + +@<Set init...@>= +deletions_allowed=true;set_box_allowed=true; +error_count=0; /*|history| is initialized elsewhere*/ + +@ Since errors can be detected almost anywhere in \TeX, we want to declare the +error procedures near the beginning of the program. But the error procedures +in turn use some other procedures, which need to be declared |forward| +before we get to |error| itself. + +It is possible for |error| to be called recursively if some error arises +when |get_token| is being used to delete a token, and/or if some fatal error +occurs while \TeX\ is trying to fix a non-fatal one. But such recursion +@^recursion@> +is never more than two levels deep. + +@<Error handling...@>= +static void normalize_selector(void);@/ +static void get_token(void);@/ +static void term_input(void);@/ +static void show_context(void);@/ +static void begin_file_reading(void);@/ +static void open_log_file(void);@/ +static void close_files_and_terminate(void);@/ +static void clear_for_error_prompt(void);@/ +static void give_err_help(void);@/ +#ifdef @!DEBUG +static void debug_help(void); +#else +#define debug_help() do_nothing +#endif + +@ Individual lines of help are recorded in the array |help_line|, which +contains entries in positions |0 dotdot(help_ptr-1)|. They should be printed +in reverse order, i.e., with |help_line[0]| appearing last. + +@d hlp1(A) help_line[0]=A;@+} +@d hlp2(A, B) help_line[1]=A;help_line[0]=B;@+} +@d hlp3(A, B, C) help_line[2]=A;help_line[1]=B;help_line[0]=C;@+} +@d hlp4(A, B, C, D) help_line[3]=A;help_line[2]=B;help_line[1]=C;help_line[0]=D;@+} +@d hlp5(A, B, C, D, E) help_line[4]=A;help_line[3]=B;help_line[2]=C;help_line[1]=D;help_line[0]=E;@+} +@d hlp6(A, B, C, D, E, F) help_line[5]=A;help_line[4]=B;help_line[3]=C;help_line[2]=D;help_line[1]=E;help_line[0]=F;@+} +@d help0 help_ptr=0 /*sometimes there might be no help*/ +@d help1(A) @+{@+help_ptr=1;hlp1(A) /*use this with one help line*/ +@d help2(A, B) @+{@+help_ptr=2;hlp2(A, B) /*use this with two help lines*/ +@d help3(A, B, C) @+{@+help_ptr=3;hlp3(A, B, C) /*use this with three help lines*/ +@d help4(A, B, C, D) @+{@+help_ptr=4;hlp4(A, B, C, D) /*use this with four help lines*/ +@d help5(A, B, C, D, E) @+{@+help_ptr=5;hlp5(A, B, C, D, E) /*use this with five help lines*/ +@d help6(A, B, C, D, E, F) @+{@+help_ptr=6;hlp6(A, B, C, D, E, F) /*use this with six help lines*/ + +@<Glob...@>= +static char *@!help_line[6]; /*helps for the next |error|*/ +static int @!help_ptr; /*the number of help lines present*/ +static bool @!use_err_help; /*should the |err_help| list be shown?*/ + +@ @<Set init...@>= +help_ptr=0;use_err_help=false; + +@ The |jump_out| procedure just cuts across all active procedure levels and +goes to |end_of_TEX|. This is the only nontrivial |@!goto| statement in the +whole program. It is used when there is no recovery from a particular error. + +Some \PASCAL\ compilers do not implement non-local |goto| statements. +@^system dependencies@> +In such cases the body of |jump_out| should simply be +`|close_files_and_terminate|;\thinspace' followed by a call on some system +procedure that quietly terminates the program. + +@<Error hand...@>= +static void jump_out(void) +{@+ close_files_and_terminate(); exit(0); +} + +@ Here now is the general |error| routine. + +@<Error hand...@>= +static void error(void) /*completes the job of error reporting*/ +{@+ +ASCII_code c; /*what the user types*/ +int @!s1, @!s2, @!s3, @!s4; + /*used to save global variables when deleting tokens*/ +if (history < error_message_issued) history=error_message_issued; +print_char('.');show_context(); +if (interaction==error_stop_mode) + @<Get user's advice and |return|@>; +incr(error_count); +if (error_count==100) + {@+print_nl("(That makes 100 errors; please try again.)"); +@.That makes 100 errors...@> + history=fatal_error_stop;jump_out(); + } +@<Put help message on the transcript file@>; +} + +@ @<Get user's advice...@>= +loop@+{@+resume: if (interaction!=error_stop_mode) return; + clear_for_error_prompt();prompt_input("? "); +@.?\relax@> + if (last==first) return; + c=buffer[first]; + if (c >= 'a') c=c+'A'-'a'; /*convert to uppercase*/ + @<Interpret code |c| and |return| if done@>; + } + +@ It is desirable to provide an `\.E' option here that gives the user +an easy way to return from \TeX\ to the system editor, with the offending +line ready to be edited. But such an extension requires some system +wizardry, so the present implementation simply types out the name of the +file that should be +edited and the relevant line number. +@^system dependencies@> + +There is a secret `\.D' option available when the debugging routines haven't +been commented~out. +@^debugging@> + +@<Interpret code |c| and |return| if done@>= +switch (c) { +case '0': case '1': case '2': case '3': + case '4': case '5': case '6': case '7': + case '8': case '9': if (deletions_allowed) + @<Delete \(c)|c-"0"| tokens and |goto resume|@>@;@+break; +@t\4\4@>@; +#ifdef @!DEBUG +case 'D': {@+debug_help();goto resume;@+} +#endif +case 'E': if (base_ptr > 0) if (input_stack[base_ptr].name_field >= 256) + {@+print_nl("You want to edit file "); +@.You want to edit file x@> + slow_print(input_stack[base_ptr].name_field); + print(" at line ");print_int(line); + interaction=scroll_mode;jump_out(); + } @+break; +case 'H': @<Print the help information and |goto resume|@>@; +case 'I': @<Introduce new material from the terminal and |return|@>@; +case 'Q': case 'R': case 'S': @<Change the interaction level and |return|@>@; +case 'X': {@+interaction=scroll_mode;jump_out(); + } @+break; +default:do_nothing; +} @/ +@<Print the menu of available options@>@; + +@ @<Print the menu...@>= +{@+print("Type <return> to proceed, S to scroll future error messages,");@/ +@.Type <return> to proceed...@> +print_nl("R to run without stopping, Q to run quietly,");@/ +print_nl("I to insert something, "); +if (base_ptr > 0) if (input_stack[base_ptr].name_field >= 256) + print("E to edit your file,"); +if (deletions_allowed) + print_nl("1 or ... or 9 to ignore the next 1 to 9 tokens of input,"); +print_nl("H for help, X to quit."); +} + +@ Here the author of \TeX\ apologizes for making use of the numerical +relation between |'Q'|, |'R'|, |'S'|, and the desired interaction settings +|batch_mode|, |nonstop_mode|, |scroll_mode|. +@^Knuth, Donald Ervin@> + +@<Change the interaction...@>= +{@+error_count=0;interaction=batch_mode+c-'Q'; +print("OK, entering "); +switch (c) { +case 'Q': {@+print_esc("batchmode");decr(selector); + } @+break; +case 'R': print_esc("nonstopmode");@+break; +case 'S': print_esc("scrollmode"); +} /*there are no other cases*/ +print("...");print_ln();update_terminal;return; +} + +@ When the following code is executed, |buffer[(first+1)dotdot(last-1)]| may +contain the material inserted by the user; otherwise another prompt will +be given. In order to understand this part of the program fully, you need +to be familiar with \TeX's input stacks. + +@<Introduce new material...@>= +{@+begin_file_reading(); /*enter a new syntactic level for terminal input*/ + /*now |state==mid_line|, so an initial blank space will count as a blank*/ +if (last > first+1) + {@+loc=first+1;buffer[first]=' '; + } +else{@+prompt_input("insert>");loc=first; +@.insert>@> + } +first=last; +cur_input.limit_field=last-1; /*no |end_line_char| ends this line*/ +return; +} + +@ We allow deletion of up to 99 tokens at a time. + +@<Delete \(c)|c-"0"| tokens...@>= +{@+s1=cur_tok;s2=cur_cmd;s3=cur_chr;s4=align_state; +align_state=1000000;OK_to_interrupt=false; +if ((last > first+1)&&(buffer[first+1] >= '0')&&(buffer[first+1] <= '9')) + c=c*10+buffer[first+1]-'0'*11; +else c=c-'0'; +while (c > 0) + {@+get_token(); /*one-level recursive call of |error| is possible*/ + decr(c); + } +cur_tok=s1;cur_cmd=s2;cur_chr=s3;align_state=s4;OK_to_interrupt=true; +help2("I have just deleted some text, as you asked.",@/ +"You can now delete more, or insert, or whatever."); +show_context();goto resume; +} + +@ @<Print the help info...@>= +{@+if (use_err_help) + {@+give_err_help();use_err_help=false; + } +else{@+if (help_ptr==0) + help2("Sorry, I don't know how to help in this situation.",@/ + @t\kern1em@>"Maybe you should try asking a human?"); + @/do@+{decr(help_ptr);print(help_line[help_ptr]);print_ln(); + }@+ while (!(help_ptr==0)); + } +help4("Sorry, I already gave what help I could...",@/ + "Maybe you should try asking a human?",@/ + "An error might have occurred before I noticed any problems.",@/ + "``If all else fails, read the instructions.'");@/ +goto resume; +} + +@ @<Put help message on the transcript file@>= +if (interaction > batch_mode) decr(selector); /*avoid terminal output*/ +if (use_err_help) + {@+print_ln();give_err_help(); + } +else while (help_ptr > 0) + {@+decr(help_ptr);print_nl(help_line[help_ptr]); + } +print_ln(); +if (interaction > batch_mode) incr(selector); /*re-enable terminal output*/ +print_ln() + +@ A dozen or so error messages end with a parenthesized integer, so we +save a teeny bit of program space by declaring the following procedure: + +@p static void int_error(int @!n) +{@+print(" (");print_int(n);print_char(')');error(); +} + +@ In anomalous cases, the print selector might be in an unknown state; +the following subroutine is called to fix things just enough to keep +running a bit longer. + +@p static void normalize_selector(void) +{@+if (log_opened) selector=term_and_log; +else selector=term_only; +if (job_name==0) open_log_file(); +if (interaction==batch_mode) decr(selector); +} + +@ The following procedure prints \TeX's last words before dying. + +@d succumb {@+if (interaction==error_stop_mode) + interaction=scroll_mode; /*no more interaction*/ + if (log_opened) error(); + if (interaction > batch_mode) debug_help(); + history=fatal_error_stop;jump_out(); /*irrecoverable error*/ + } + +@<Error hand...@>= +static void fatal_error(char *@!s) /*prints |s|, and that's it*/ +{@+normalize_selector();@/ +print_err("Emergency stop");help1(s);succumb; +@.Emergency stop@> +} + +@ Here is the most dreaded error message. + +@<Error hand...@>= +static void overflow(char *@!s, int @!n) /*stop due to finiteness*/ +{@+normalize_selector(); +print_err("TeX capacity exceeded, sorry ["); +@.TeX capacity exceeded ...@> +print(s);print_char('=');print_int(n);print_char(']'); +help2("If you really absolutely need more capacity,",@/ + "you can ask a wizard to enlarge me."); +succumb; +} + +@ The program might sometime run completely amok, at which point there is +no choice but to stop. If no previous error has been detected, that's bad +news; a message is printed that is really intended for the \TeX\ +maintenance person instead of the user (unless the user has been +particularly diabolical). The index entries for `this can't happen' may +help to pinpoint the problem. +@^dry rot@> + +@<Error hand...@>= +static void confusion(char *@!s) + /*consistency check violated; |s| tells where*/ +{@+normalize_selector(); +if (history < error_message_issued) + {@+print_err("This can't happen (");print(s);print_char(')'); +@.This can't happen@> + help1("I'm broken. Please show this to someone who can fix can fix"); + } +else{@+print_err("I can't go on meeting you like this"); +@.I can't go on...@> + help2("One of your faux pas seems to have wounded me deeply...",@/ + "in fact, I'm barely conscious. Please fix it and try again."); + } +succumb; +} + +@ Users occasionally want to interrupt \TeX\ while it's running. +If the \PASCAL\ runtime system allows this, one can implement +a routine that sets the global variable |interrupt| to some nonzero value +when such an interrupt is signalled. Otherwise there is probably at least +a way to make |interrupt| nonzero using the \PASCAL\ debugger. +@^system dependencies@> +@^debugging@> + +@d check_interrupt {@+if (interrupt!=0) pause_for_instructions(); + } + +@<Global...@>= +static int @!interrupt; /*should \TeX\ pause for instructions?*/ +static bool @!OK_to_interrupt; /*should interrupts be observed?*/ + +@ @<Set init...@>= +interrupt=0;OK_to_interrupt=true; + +@ When an interrupt has been detected, the program goes into its +highest interaction level and lets the user have nearly the full flexibility of +the |error| routine. \TeX\ checks for interrupts only at times when it is +safe to do this. + +@p static void pause_for_instructions(void) +{@+if (OK_to_interrupt) + {@+interaction=error_stop_mode; + if ((selector==log_only)||(selector==no_print)) + incr(selector); + print_err("Interruption"); +@.Interruption@> + help3("You rang?",@/ + "Try to insert an instruction for me (e.g., `I\\showlists'),",@/ + "unless you just want to quit by typing `X'."); + deletions_allowed=false;error();deletions_allowed=true; + interrupt=0; + } +} + +@* Arithmetic with scaled dimensions. +The principal computations performed by \TeX\ are done entirely in terms of +integers less than $2^{31}$ in magnitude; and divisions are done only when both +dividend and divisor are nonnegative. Thus, the arithmetic specified in this +program can be carried out in exactly the same way on a wide variety of +computers, including some small ones. Why? Because the arithmetic +calculations need to be spelled out precisely in order to guarantee that +\TeX\ will produce identical output on different machines. If some +quantities were rounded differently in different implementations, we would +find that line breaks and even page breaks might occur in different places. +Hence the arithmetic of \TeX\ has been designed with care, and systems that +claim to be implementations of \TeX82 should follow precisely the +@:TeX82}{\TeX82@> +calculations as they appear in the present program. + +(Actually there are three places where \TeX\ uses |/| with a possibly negative +numerator. These are harmless; see |/| in the index. Also if the user +sets the \.{\\time} or the \.{\\year} to a negative value, some diagnostic +information will involve negative-numerator division. The same remarks +apply for |%| as well as for |/|.) + +@ Here is a routine that calculates half of an integer, using an +unambiguous convention with respect to signed odd numbers. + +@p static int half(int @!x) +{@+if (odd(x)) return(x+1)/2; +else return x/2; +} + +@ Fixed-point arithmetic is done on {\sl scaled integers\/} that are multiples +of $2^{-16}$. In other words, a binary point is assumed to be sixteen bit +positions from the right end of a binary computer word. + +@d unity 0200000 /*$2^{16}$, represents 1.00000*/ +@d two 0400000 /*$2^{17}$, represents 2.00000*/ + +@<Types...@>= +typedef int scaled; /*this type is used for scaled integers*/ +typedef int32_t nonnegative_integer; /*$0\le x<2^{31}$*/ +typedef int8_t small_number; /*this type is self-explanatory*/ + +@ The following function is used to create a scaled integer from a given decimal +fraction $(.d_0d_1\ldots d_{k-1})$, where |0 <= k <= 17|. The digit $d_i$ is +given in |dig[i]|, and the calculation produces a correctly rounded result. + +@p static scaled round_decimals(small_number @!k) + /*converts a decimal fraction*/ +{@+int a; /*the accumulator*/ +a=0; +while (k > 0) + {@+decr(k);a=(a+dig[k]*two)/10; + } +return(a+1)/2; +} + +@ Conversely, here is a procedure analogous to |print_int|. If the output +of this procedure is subsequently read by \TeX\ and converted by the +|round_decimals| routine above, it turns out that the original value will +be reproduced exactly; the ``simplest'' such decimal number is output, +but there is always at least one digit following the decimal point. + +The invariant relation in the \&{repeat} loop is that a sequence of +decimal digits yet to be printed will yield the original number if and only if +they form a fraction~$f$ in the range $s-\delta\le 10\cdot2^{16}f<s$. +We can stop if and only if $f=0$ satisfies this condition; the loop will +terminate before $s$ can possibly become zero. + +@p static void print_scaled(scaled @!s) /*prints scaled real, rounded to five + digits*/ +{@+scaled delta; /*amount of allowable inaccuracy*/ +if (s < 0) + {@+print_char('-');negate(s); /*print the sign, if negative*/ + } +print_int(s/unity); /*print the integer part*/ +print_char('.'); +s=10*(s%unity)+5;delta=10; +@/do@+{if (delta > unity) s=s+0100000-50000; /*round the last digit*/ +print_char('0'+(s/unity));s=10*(s%unity);delta=delta*10; +}@+ while (!(s <= delta)); +} + +@ Physical sizes that a \TeX\ user specifies for portions of documents are +represented internally as scaled points. Thus, if we define an `sp' (scaled +@^sp@> +point) as a unit equal to $2^{-16}$ printer's points, every dimension +inside of \TeX\ is an integer number of sp. There are exactly +4,736,286.72 sp per inch. Users are not allowed to specify dimensions +larger than $2^{30}-1$ sp, which is a distance of about 18.892 feet (5.7583 +meters); two such quantities can be added without overflow on a 32-bit +computer. + +The present implementation of \TeX\ does not check for overflow when +@^overflow in arithmetic@> +dimensions are added or subtracted. This could be done by inserting a +few dozen tests of the form `\ignorespaces|if (x >= 010000000000)| +\\{report\_overflow}', but the chance of overflow is so remote that +such tests do not seem worthwhile. + +\TeX\ needs to do only a few arithmetic operations on scaled quantities, +other than addition and subtraction, and the following subroutines do most of +the work. A single computation might use several subroutine calls, and it is +desirable to avoid producing multiple error messages in case of arithmetic +overflow; so the routines set the global variable |arith_error| to |true| +instead of reporting errors directly to the user. Another global variable, +|rem|, holds the remainder after a division. + +@<Glob...@>= +static bool @!arith_error; /*has arithmetic overflow occurred recently?*/ +static scaled @!rem; /*amount subtracted to get an exact division*/ + +@ The first arithmetical subroutine we need computes $nx+y$, where |x| +and~|y| are |scaled| and |n| is an integer. We will also use it to +multiply integers. + +@d nx_plus_y(A, B, C) mult_and_add(A, B, C, 07777777777) +@d mult_integers(A, B) mult_and_add(A, B, 0, 017777777777) + +@p static scaled mult_and_add(int @!n, scaled @!x, scaled @!y, scaled @!max_answer) +{@+if (n < 0) + {@+negate(x);negate(n); + } +if (n==0) return y; +else if (((x <= (max_answer-y)/n)&&(-x <= (max_answer+y)/n))) + return n*x+y; +else{@+arith_error=true;return 0; + } +} + +@ We also need to divide scaled dimensions by integers. + +@p static scaled x_over_n(scaled @!x, int @!n) +{@+bool negative; /*should |rem| be negated?*/ +scaled x_over_n; +negative=false; +if (n==0) + {@+arith_error=true;x_over_n=0;rem=x; + } +else{@+if (n < 0) + {@+negate(x);negate(n);negative=true; + } + if (x >= 0) + {@+x_over_n=x/n;rem=x%n; + } + else{@+x_over_n=-((-x)/n);rem=-((-x)%n); + } + } +if (negative) negate(rem); +return x_over_n;} + +@ Then comes the multiplication of a scaled number by a fraction |n/(double)d|, +where |n| and |d| are nonnegative integers | <= @t$2^{16}$@>| and |d| is +positive. It would be too dangerous to multiply by~|n| and then divide +by~|d|, in separate operations, since overflow might well occur; and it +would be too inaccurate to divide by |d| and then multiply by |n|. Hence +this subroutine simulates 1.5-precision arithmetic. + +@p static scaled xn_over_d(scaled @!x, int @!n, int @!d) +{@+bool positive; /*was |x >= 0|?*/ +nonnegative_integer @!t, @!u, @!v; /*intermediate quantities*/ +scaled xn_over_d; +if (x >= 0) positive=true; +else{@+negate(x);positive=false; + } +t=(x%0100000)*n; +u=(x/0100000)*n+(t/0100000); +v=(u%d)*0100000+(t%0100000); +if (u/d >= 0100000) arith_error=true; +else u=0100000*(u/d)+(v/d); +if (positive) + {@+xn_over_d=u;rem=v%d; + } +else{@+xn_over_d=-u;rem=-(v%d); + } +return xn_over_d;} + +@ The next subroutine is used to compute the ``badness'' of glue, when a +total~|t| is supposed to be made from amounts that sum to~|s|. According +to {\sl The \TeX book}, the badness of this situation is $100(t/s)^3$; +however, badness is simply a heuristic, so we need not squeeze out the +last drop of accuracy when computing it. All we really want is an +approximation that has similar properties. +@:TeXbook}{\sl The \TeX book@> + +The actual method used to compute the badness is easier to read from the +program than to describe in words. It produces an integer value that is a +reasonably close approximation to $100(t/s)^3$, and all implementations +of \TeX\ should use precisely this method. Any badness of $2^{13}$ or more is +treated as infinitely bad, and represented by 10000. + +It is not difficult to prove that $$\hbox{|badness(t+1, s) >= badness(t, s) + >= badness(t, s+1)|}.$$ The badness function defined here is capable of +computing at most 1095 distinct values, but that is plenty. + +@d inf_bad 10000 /*infinitely bad value*/ + +@p @<Declare \Prote\ arithmetic routines@>@/ +static halfword badness(scaled @!t, scaled @!s) /*compute badness, given |t >= 0|*/ +{@+int r; /*approximation to $\alpha t/s$, where $\alpha^3\approx + 100\cdot2^{18}$*/ +if (t==0) return 0; +else if (s <= 0) return inf_bad; +else{@+if (t <= 7230584) r=(t*297)/s; /*$297^3=99.94\times2^{18}$*/ + else if (s >= 1663497) r=t/(s/297); + else r=t; + if (r > 1290) return inf_bad; /*$1290^3<2^{31}<1291^3$*/ + else return(r*r*r+0400000)/01000000; + } /*that was $r^3/2^{18}$, rounded to the nearest integer*/ +} + +@ When \TeX\ ``packages'' a list into a box, it needs to calculate the +proportionality ratio by which the glue inside the box should stretch +or shrink. This calculation does not affect \TeX's decision making, +so the precise details of rounding, etc., in the glue calculation are not +of critical importance for the consistency of results on different computers. + +We shall use the type |glue_ratio| for such proportionality ratios. +A glue ratio should take the same amount of memory as an +|int| (usually 32 bits) if it is to blend smoothly with \TeX's +other data structures. Thus |glue_ratio| should be equivalent to +|short_real| in some implementations of \PASCAL. Alternatively, +it is possible to deal with glue ratios using nothing but fixed-point +arithmetic; see {\sl TUGboat \bf3},1 (March 1982), 10--27. (But the +routines cited there must be modified to allow negative glue ratios.) +@^system dependencies@> + +@d set_glue_ratio_zero(A) A=0.0 /*store the representation of zero ratio*/ +@d set_glue_ratio_one(A) A=1.0 /*store the representation of unit ratio*/ +@d unfix(A) ((double)(A)) /*convert from |glue_ratio| to type |double|*/ +@d fix(A) ((glue_ratio)(A)) /*convert from |double| to type |glue_ratio|*/ +@d float_constant(A) ((double)(A)) /*convert |int| constant to |double|*/ + +@<Types...@>= +#if __SIZEOF_FLOAT__==4 +typedef float float32_t; +#else +#error @=float type must have size 4@> +#endif +typedef float @!glue_ratio; /*one-word representation of a glue expansion factor*/ + +@* Packed data. +In order to make efficient use of storage space, \TeX\ bases its major data +structures on a |memory_word|, which contains either a (signed) integer, +possibly scaled, or a (signed) |glue_ratio|, or a small number of +fields that are one half or one quarter of the size used for storing +integers. + +If |x| is a variable of type |memory_word|, it contains up to four +fields that can be referred to as follows: +$$\vbox{\halign{\hfil#&#\hfil&#\hfil\cr +|x|&.|i|&(an |int|)\cr +|x|&.|sc|\qquad&(a |scaled| integer)\cr +|x|&.|gr|&(a |glue_ratio|)\cr +|x.hh.lh|, |x.hh|&.|rh|&(two halfword fields)\cr +|x.hh.b0|, |x.hh.b1|, |x.hh|&.|rh|&(two quarterword fields, one halfword + field)\cr +|x.qqqq.b0|, |x.qqqq.b1|, |x.qqqq|&.|b2|, |x.qqqq.b3|\hskip-100pt + &\qquad\qquad\qquad(four quarterword fields)\cr}}$$ +This is somewhat cumbersome to write, and not very readable either, but +macros will be used to make the notation shorter and more transparent. +The \PASCAL\ code below gives a formal definition of |memory_word| and +its subsidiary types, using packed variant records. \TeX\ makes no +assumptions about the relative positions of the fields within a word. + +Since we are assuming 32-bit integers, a halfword must contain at least +16 bits, and a quarterword must contain at least 8 bits. +@^system dependencies@> +But it doesn't hurt to have more bits; for example, with enough 36-bit +words you might be able to have |mem_max| as large as 262142, which is +eight times as much memory as anybody had during the first four years of +\TeX's existence. + +N.B.: Valuable memory space will be dreadfully wasted unless \TeX\ is compiled +by a \PASCAL\ that packs all of the |memory_word| variants into +the space of a single integer. This means, for example, that |glue_ratio| +words should be |short_real| instead of |double| on some computers. Some +\PASCAL\ compilers will pack an integer whose subrange is `|0 dotdot 255|' into +an eight-bit field, but others insist on allocating space for an additional +sign bit; on such systems you can get 256 values into a quarterword only +if the subrange is `|-128 dotdot 127|'. + +The present implementation tries to accommodate as many variations as possible, +so it makes few assumptions. If integers having the subrange +`|min_quarterword dotdot max_quarterword|' can be packed into a quarterword, +and if integers having the subrange `|min_halfword dotdot max_halfword|' +can be packed into a halfword, everything should work satisfactorily. + +It is usually most efficient to have |min_quarterword==min_halfword==0|, +so one should try to achieve this unless it causes a severe problem. +The values defined here are recommended for most 32-bit computers. + +@d min_quarterword 0 /*smallest allowable value in a |quarterword|*/ +@d max_quarterword 65535 /*largest allowable value in a |quarterword|*/ +@d min_halfword 0 /*smallest allowable value in a |halfword|*/ +@d max_halfword 0x3FFFFFFF /*largest allowable value in a |halfword|*/ + +@ Here are the inequalities that the quarterword and halfword values +must satisfy (or rather, the inequalities that they mustn't satisfy): + +@<Check the ``constant''...@>= +#ifdef @!INIT +if ((mem_min!=mem_bot)||(mem_max!=mem_top)) bad=10; +#endif +@;@/ +if ((mem_min > mem_bot)||(mem_max < mem_top)) bad=10; +if ((min_quarterword > 0)||(max_quarterword < 127)) bad=11; +if ((min_halfword > 0)||(max_halfword < 32767)) bad=12; +if ((min_quarterword < min_halfword)||@| + (max_quarterword > max_halfword)) bad=13; +if ((mem_min < min_halfword)||(mem_max >= max_halfword)||@| + (mem_bot-mem_min > max_halfword+1)) bad=14; +if ((font_base < min_quarterword)||(font_max > max_quarterword)) bad=15; +if (font_max > font_base+256) bad=16; +if ((save_size > max_halfword)||(max_strings > max_halfword)) bad=17; +if (buf_size > max_halfword) bad=18; +if (max_quarterword-min_quarterword < 255) bad=19; + +@ The operation of adding or subtracting |min_quarterword| occurs quite +frequently in \TeX, so it is convenient to abbreviate this operation +by using the macros |qi| and |qo| for input and output to and from +quarterword format. + +The inner loop of \TeX\ will run faster with respect to compilers +that don't optimize expressions like `|x+0|' and `|x-0|', if these +macros are simplified in the obvious way when |min_quarterword==0|. +@^inner loop@>@^system dependencies@> + +@d qi(A) A+min_quarterword + /*to put an |eight_bits| item into a quarterword*/ +@d qo(A) A-min_quarterword + /*to take an |eight_bits| item out of a quarterword*/ +@d hi(A) A+min_halfword + /*to put a sixteen-bit item into a halfword*/ +@d ho(A) A-min_halfword + /*to take a sixteen-bit item from a halfword*/ + +@ The reader should study the following definitions closely: +@^system dependencies@> + +@d sc i /*|scaled| data is equivalent to |int|*/ + +@<Types...@>= +typedef uint16_t quarterword; /*1/4 of a word*/ +typedef int32_t halfword; /*1/2 of a word*/ +typedef int8_t two_choices; /*used when there are two variants in a record*/ +typedef int8_t four_choices; /*used when there are four variants in a record*/ +typedef uint64_t fullword; +typedef struct { @;@/ + halfword @!rh; + union { + halfword @!lh; + struct { quarterword @!b0;quarterword @!b1;} ; + };} two_halves; +typedef struct { @;@/ + quarterword @!b0; + quarterword @!b1; + quarterword @!b2; + quarterword @!b3; + } four_quarters; +typedef struct { @;@/ + union { + fullword @!w; + int @!i; + glue_ratio @!gr; + two_halves @!hh; + four_quarters @!qqqq; + };} memory_word; +typedef struct {@+FILE *f;@+memory_word@,d;@+} word_file; + +@ When debugging, we may want to print a |memory_word| without knowing +what type it is; so we print it in all modes. +@^dirty \PASCAL@>@^debugging@> + +@p +#ifdef @!DEBUG +static void print_word(memory_word @!w) + /*prints |w| in all ways*/ +{@+print_int(w.i);print_char(' ');@/ +print_scaled(w.sc);print_char(' ');@/ +print_scaled(round(unity*unfix(w.gr)));print_ln();@/ +@^real multiplication@> +print_int(w.hh.lh);print_char('=');print_int(w.hh.b0);print_char(':'); +print_int(w.hh.b1);print_char(';');print_int(w.hh.rh);print_char(' ');@/ +print_int(w.qqqq.b0);print_char(':');print_int(w.qqqq.b1);print_char(':'); +print_int(w.qqqq.b2);print_char(':');print_int(w.qqqq.b3); +} +#endif + +@* Dynamic memory allocation. +The \TeX\ system does nearly all of its own memory allocation, so that it +can readily be transported into environments that do not have automatic +facilities for strings, garbage collection, etc., and so that it can be in +control of what error messages the user receives. The dynamic storage +requirements of \TeX\ are handled by providing a large array |mem| in +which consecutive blocks of words are used as nodes by the \TeX\ routines. + +Pointer variables are indices into this array, or into another array +called |eqtb| that will be explained later. A pointer variable might +also be a special flag that lies outside the bounds of |mem|, so we +allow pointers to assume any |halfword| value. The minimum halfword +value represents a null pointer. \TeX\ does not assume that |mem[null]| exists. + +@s pointer int +@d pointer halfword /*a flag or a location in |mem| or |eqtb|*/ +@d null min_halfword /*the null pointer*/ + +@<Glob...@>= +static pointer @!temp_ptr; /*a pointer variable for occasional emergency use*/ + +@ The |mem| array is divided into two regions that are allocated separately, +but the dividing line between these two regions is not fixed; they grow +together until finding their ``natural'' size in a particular job. +Locations less than or equal to |lo_mem_max| are used for storing +variable-length records consisting of two or more words each. This region +is maintained using an algorithm similar to the one described in exercise +2.5--19 of {\sl The Art of Computer Programming}. However, no size field +appears in the allocated nodes; the program is responsible for knowing the +relevant size when a node is freed. Locations greater than or equal to +|hi_mem_min| are used for storing one-word records; a conventional +\.{AVAIL} stack is used for allocation in this region. + +Locations of |mem| between |mem_bot| and |mem_top| may be dumped as part +of preloaded format files, by the \.{INITEX} preprocessor. +@.INITEX@> +Production versions of \TeX\ may extend the memory at both ends in order to +provide more space; locations between |mem_min| and |mem_bot| are always +used for variable-size nodes, and locations between |mem_top| and |mem_max| +are always used for single-word nodes. + +The key pointers that govern |mem| allocation have a prescribed order: +$$\advance\thickmuskip-2mu +\hbox{|null <= mem_min <= mem_bot < lo_mem_max < + hi_mem_min < mem_top <= mem_end <= mem_max|.}$$ + +Empirical tests show that the present implementation of \TeX\ tends to +spend about 9\pct! of its running time allocating nodes, and about 6\pct! +deallocating them after their use. + +@<Glob...@>= +static memory_word @!mem0[mem_max-mem_min+1], + *const @!mem = @!mem0-mem_min; /*the big dynamic storage area*/ +static pointer @!lo_mem_max; /*the largest location of variable-size memory in use*/ +static pointer @!hi_mem_min; /*the smallest location of one-word memory in use*/ + +@ In order to study the memory requirements of particular applications, it +is possible to prepare a version of \TeX\ that keeps track of current and +maximum memory usage. When code between the delimiters | +#ifdef @!STAT +| $\ldots$ +|@t\#\&{endif}@>| is not ``commented out,'' \TeX\ will run a bit slower but it will +report these statistics when |tracing_stats| is sufficiently large. + +@<Glob...@>= +static int @!var_used, @!dyn_used; /*how much memory is in use*/ +#ifdef @!STAT +#define incr_dyn_used @[incr(dyn_used)@] +#define decr_dyn_used @[decr(dyn_used)@] +#else +#define incr_dyn_used +#define decr_dyn_used +#endif + +@ Let's consider the one-word memory region first, since it's the +simplest. The pointer variable |mem_end| holds the highest-numbered location +of |mem| that has ever been used. The free locations of |mem| that +occur between |hi_mem_min| and |mem_end|, inclusive, are of type +|two_halves|, and we write |info(p)| and |link(p)| for the |lh| +and |rh| fields of |mem[p]| when it is of this type. The single-word +free locations form a linked list +$$|avail|,\;\hbox{|link(avail)|},\;\hbox{|link(link(avail))|},\;\ldots$$ +terminated by |null|. + +@d link(A) mem[A].hh.rh /*the |link| field of a memory word*/ +@d info(A) mem[A].hh.lh /*the |info| field of a memory word*/ + +@<Glob...@>= +static pointer @!avail; /*head of the list of available one-word nodes*/ +static pointer @!mem_end; /*the last one-word node used in |mem|*/ + +@ If memory is exhausted, it might mean that the user has forgotten +a right brace. We will define some procedures later that try to help +pinpoint the trouble. + +@p @<Declare the procedure called |show_token_list|@>@/ +@<Declare the procedure called |runaway|@>@; + +@ The function |get_avail| returns a pointer to a new one-word node whose +|link| field is null. However, \TeX\ will halt if there is no more room left. +@^inner loop@> + +If the available-space list is empty, i.e., if |avail==null|, +we try first to increase |mem_end|. If that cannot be done, i.e., if +|mem_end==mem_max|, we try to decrease |hi_mem_min|. If that cannot be +done, i.e., if |hi_mem_min==lo_mem_max+1|, we have to quit. + +@p static pointer get_avail(void) /*single-word node allocation*/ +{@+pointer p; /*the new node being got*/ +p=avail; /*get top location in the |avail| stack*/ +if (p!=null) avail=link(avail); /*and pop it off*/ +else if (mem_end < mem_max) /*or go into virgin territory*/ + {@+incr(mem_end);p=mem_end; + } +else{@+decr(hi_mem_min);p=hi_mem_min; + if (hi_mem_min <= lo_mem_max) + {@+runaway(); /*if memory is exhausted, display possible runaway text*/ + overflow("main memory size", mem_max+1-mem_min); + /*quit; all one-word nodes are busy*/ +@:TeX capacity exceeded main memory size}{\quad main memory size@> + } + } +link(p)=null; /*provide an oft-desired initialization of the new node*/ +#ifdef @!STAT +incr(dyn_used); +#endif +@; /*maintain statistics*/ +return p; +} + +@ Conversely, a one-word node is recycled by calling |free_avail|. +This routine is part of \TeX's ``inner loop,'' so we want it to be fast. +@^inner loop@> + +@d free_avail(A) /*single-word node liberation*/ + {@+link(A)=avail;avail=A; + decr_dyn_used; + } + +@ There's also a |fast_get_avail| routine, which saves the procedure-call +overhead at the expense of extra programming. This routine is used in +the places that would otherwise account for the most calls of |get_avail|. +@^inner loop@> + +@d fast_get_avail(A) @t@>@;@/ + {@+A=avail; /*avoid |get_avail| if possible, to save time*/ + if (A==null) A=get_avail(); + else{@+avail=link(A);link(A)=null; + incr_dyn_used; + } + } + +@ The procedure |flush_list(p)| frees an entire linked list of +one-word nodes that starts at position |p|. +@^inner loop@> + +@p static void flush_list(pointer @!p) /*makes list of single-word nodes + available*/ +{@+pointer @!q, @!r; /*list traversers*/ +if (p!=null) + {@+r=p; + @/do@+{q=r;r=link(r); +#ifdef @!STAT +decr(dyn_used); +#endif + }@+ while (!(r==null)); /*now |q| is the last node on the list*/ + link(q)=avail;avail=p; + } +} + +@ The available-space list that keeps track of the variable-size portion +of |mem| is a nonempty, doubly-linked circular list of empty nodes, +pointed to by the roving pointer |rover|. + +Each empty node has size 2 or more; the first word contains the special +value |max_halfword| in its |link| field and the size in its |info| field; +the second word contains the two pointers for double linking. + +Each nonempty node also has size 2 or more. Its first word is of type +|two_halves|\kern-1pt, and its |link| field is never equal to |max_halfword|. +Otherwise there is complete flexibility with respect to the contents +of its other fields and its other words. + +(We require |mem_max < max_halfword| because terrible things can happen +when |max_halfword| appears in the |link| field of a nonempty node.) + +@d empty_flag max_halfword /*the |link| of an empty variable-size node*/ +@d is_empty(A) (link(A)==empty_flag) /*tests for empty node*/ +@d node_size(A) info(A) /*the size field in empty variable-size nodes*/ +@d llink(A) info(A+1) /*left link in doubly-linked list of empty nodes*/ +@d rlink(A) link(A+1) /*right link in doubly-linked list of empty nodes*/ + +@<Glob...@>= +static pointer @!rover; /*points to some node in the list of empties*/ + +@ A call to |get_node| with argument |s| returns a pointer to a new node +of size~|s|, which must be 2~or more. The |link| field of the first word +of this new node is set to null. An overflow stop occurs if no suitable +space exists. + +If |get_node| is called with $s=2^{30}$, it simply merges adjacent free +areas and returns the value |max_halfword|. + +@p static pointer get_node(int @!s) /*variable-size node allocation*/ +{@+ +pointer p; /*the node currently under inspection*/ +pointer @!q; /*the node physically after node |p|*/ +int @!r; /*the newly allocated node, or a candidate for this honor*/ +int @!t; /*temporary register*/ +restart: p=rover; /*start at some free node in the ring*/ +@/do@+{@<Try to allocate within node |p| and its physical successors, and +|goto found| if allocation was possible@>; +@^inner loop@> +p=rlink(p); /*move to the next node in the ring*/ +}@+ while (!(p==rover)); /*repeat until the whole list has been traversed*/ +if (s==010000000000) + {@+return max_halfword; + } +if (lo_mem_max+2 < hi_mem_min) if (lo_mem_max+2 <= mem_bot+max_halfword) + @<Grow more variable-size memory and |goto restart|@>; +overflow("main memory size", mem_max+1-mem_min); + /*sorry, nothing satisfactory is left*/ +@:TeX capacity exceeded main memory size}{\quad main memory size@> +found: link(r)=null; /*this node is now nonempty*/ +#ifdef @!STAT +var_used=var_used+s; /*maintain usage statistics*/ +#endif +@;@/ +return r; +} + +@ The lower part of |mem| grows by 1000 words at a time, unless +we are very close to going under. When it grows, we simply link +a new node into the available-space list. This method of controlled +growth helps to keep the |mem| usage consecutive when \TeX\ is +implemented on ``virtual memory'' systems. +@^virtual memory@> + +@<Grow more variable-size memory and |goto restart|@>= +{@+if (hi_mem_min-lo_mem_max >= 1998) t=lo_mem_max+1000; +else t=lo_mem_max+1+(hi_mem_min-lo_mem_max)/2; + /*|lo_mem_max+2 <= t < hi_mem_min|*/ +p=llink(rover);q=lo_mem_max;rlink(p)=q;llink(rover)=q;@/ +if (t > mem_bot+max_halfword) t=mem_bot+max_halfword; +rlink(q)=rover;llink(q)=p;link(q)=empty_flag;node_size(q)=t-lo_mem_max;@/ +lo_mem_max=t;link(lo_mem_max)=null;info(lo_mem_max)=null; +rover=q;goto restart; +} + +@ Empirical tests show that the routine in this section performs a +node-merging operation about 0.75 times per allocation, on the average, +after which it finds that |r > p+1| about 95\pct! of the time. + +@<Try to allocate...@>= +q=p+node_size(p); /*find the physical successor*/ +@^inner loop@> +while (is_empty(q)) /*merge node |p| with node |q|*/ + {@+t=rlink(q); + if (q==rover) rover=t; + llink(t)=llink(q);rlink(llink(q))=t;@/ + q=q+node_size(q); + } +r=q-s; +if (r > p+1) @<Allocate from the top of node |p| and |goto found|@>; +if (r==p) if (rlink(p)!=p) + @<Allocate entire node |p| and |goto found|@>; +node_size(p)=q-p /*reset the size in case it grew*/ + +@ @<Allocate from the top...@>= +{@+node_size(p)=r-p; /*store the remaining size*/ +@^inner loop@> +rover=p; /*start searching here next time*/ +goto found; +} + +@ Here we delete node |p| from the ring, and let |rover| rove around. + +@<Allocate entire...@>= +{@+rover=rlink(p);t=llink(p); +llink(rover)=t;rlink(t)=rover; +goto found; +} + +@ Conversely, when some variable-size node |p| of size |s| is no longer needed, +the operation |free_node(p, s)| will make its words available, by inserting +|p| as a new empty node just before where |rover| now points. +@^inner loop@> + +@p static void free_node(pointer @!p, halfword @!s) /*variable-size node + liberation*/ +{@+pointer q; /*|llink(rover)|*/ +node_size(p)=s;link(p)=empty_flag; +q=llink(rover);llink(p)=q;rlink(p)=rover; /*set both links*/ +llink(rover)=p;rlink(q)=p; /*insert |p| into the ring*/ +#ifdef @!STAT +var_used=var_used-s; +#endif +@; /*maintain statistics*/ +} + +@ Just before \.{INITEX} writes out the memory, it sorts the doubly linked +available space list. The list is probably very short at such times, so a +simple insertion sort is used. The smallest available location will be +pointed to by |rover|, the next-smallest by |rlink(rover)|, etc. + +@p +#ifdef @!INIT +static void sort_avail(void) /*sorts the available variable-size nodes + by location*/ +{@+pointer p, @!q, @!r; /*indices into |mem|*/ +pointer @!old_rover; /*initial |rover| setting*/ +p=get_node(010000000000); /*merge adjacent free areas*/ +p=rlink(rover);rlink(rover)=max_halfword;old_rover=rover; +while (p!=old_rover) @<Sort \(p)|p| into the list starting at |rover| and +advance |p| to |rlink(p)|@>; +p=rover; +while (rlink(p)!=max_halfword) + {@+llink(rlink(p))=p;p=rlink(p); + } +rlink(p)=rover;llink(rover)=p; +} +#endif + +@ The following |while | loop is guaranteed to +terminate, since the list that starts at +|rover| ends with |max_halfword| during the sorting procedure. + +@<Sort \(p)|p|...@>= +if (p < rover) + {@+q=p;p=rlink(q);rlink(q)=rover;rover=q; + } +else{@+q=rover; + while (rlink(q) < p) q=rlink(q); + r=rlink(p);rlink(p)=rlink(q);rlink(q)=p;p=r; + } + +@* Data structures for boxes and their friends. +From the computer's standpoint, \TeX's chief mission is to create +horizontal and vertical lists. We shall now investigate how the elements +of these lists are represented internally as nodes in the dynamic memory. + +A horizontal or vertical list is linked together by |link| fields in +the first word of each node. Individual nodes represent boxes, glue, +penalties, or special things like discretionary hyphens; because of this +variety, some nodes are longer than others, and we must distinguish different +kinds of nodes. We do this by putting a `|type|' field in the first word, +together with the link and an optional `|subtype|'. + +@d type(A) mem[A].hh.b0 /*identifies what kind of node this is*/ +@d subtype(A) mem[A].hh.b1 /*secondary identification in some cases*/ + +@ A |@!char_node|, which represents a single character, is the most important +kind of node because it accounts for the vast majority of all boxes. +Special precautions are therefore taken to ensure that a |char_node| does +not take up much memory space. Every such node is one word long, and in fact +it is identifiable by this property, since other kinds of nodes have at least +two words, and they appear in |mem| locations less than |hi_mem_min|. +This makes it possible to omit the |type| field in a |char_node|, leaving +us room for two bytes that identify a |font| and a |character| within +that font. + +Note that the format of a |char_node| allows for up to 256 different +fonts and up to 256 characters per font; but most implementations will +probably limit the total number of fonts to fewer than 75 per job, +and most fonts will stick to characters whose codes are +less than 128 (since higher codes +are more difficult to access on most keyboards). + +Extensions of \TeX\ intended for oriental languages will need even more +than $256\times256$ possible characters, when we consider different sizes +@^oriental characters@>@^Chinese characters@>@^Japanese characters@> +and styles of type. It is suggested that Chinese and Japanese fonts be +handled by representing such characters in two consecutive |char_node| +entries: The first of these has |font==font_base|, and its |link| points +to the second; +the second identifies the font and the character dimensions. +The saving feature about oriental characters is that most of them have +the same box dimensions. The |character| field of the first |char_node| +is a ``\\{charext}'' that distinguishes between graphic symbols whose +dimensions are identical for typesetting purposes. (See the \MF\ manual.) +Such an extension of \TeX\ would not be difficult; further details are +left to the reader. + +In order to make sure that the |character| code fits in a quarterword, +\TeX\ adds the quantity |min_quarterword| to the actual code. + +Character nodes appear only in horizontal lists, never in vertical lists. + +@d is_char_node(A) (A >= hi_mem_min) + /*does the argument point to a |char_node|?*/ +@d font(A) type(A) /*the font code in a |char_node|*/ +@d character(A) subtype(A) /*the character code in a |char_node|*/ + +@ An |hlist_node| stands for a box that was made from a horizontal list. +Each |hlist_node| is seven words long, and contains the following fields +(in addition to the mandatory |type| and |link|, which we shall not +mention explicitly when discussing the other node types): The |height| and +|width| and |depth| are scaled integers denoting the dimensions of the +box. There is also a |shift_amount| field, a scaled integer indicating +how much this box should be lowered (if it appears in a horizontal list), +or how much it should be moved to the right (if it appears in a vertical +list). There is a |list_ptr| field, which points to the beginning of the +list from which this box was fabricated; if |list_ptr| is |null|, the box +is empty. Finally, there are three fields that represent the setting of +the glue: |glue_set(p)| is a word of type |glue_ratio| that represents +the proportionality constant for glue setting; |glue_sign(p)| is +|stretching| or |shrinking| or |normal| depending on whether or not the +glue should stretch or shrink or remain rigid; and |glue_order(p)| +specifies the order of infinity to which glue setting applies (|normal|, +|fil|, |fill|, or |filll|). The |subtype| field is not used. + +@d hlist_node 0 /*|type| of hlist nodes*/ +@d box_node_size 7 /*number of words to allocate for a box node*/ +@d width_offset 1 /*position of |width| field in a box node*/ +@d depth_offset 2 /*position of |depth| field in a box node*/ +@d height_offset 3 /*position of |height| field in a box node*/ +@d width(A) mem[A+width_offset].sc /*width of the box, in sp*/ +@d depth(A) mem[A+depth_offset].sc /*depth of the box, in sp*/ +@d height(A) mem[A+height_offset].sc /*height of the box, in sp*/ +@d shift_amount(A) mem[A+4].sc /*repositioning distance, in sp*/ +@d list_offset 5 /*position of |list_ptr| field in a box node*/ +@d list_ptr(A) link(A+list_offset) /*beginning of the list inside the box*/ +@d glue_order(A) subtype(A+list_offset) /*applicable order of infinity*/ +@d glue_sign(A) type(A+list_offset) /*stretching or shrinking*/ +@d normal 0 /*the most common case when several cases are named*/ +@d stretching 1 /*glue setting applies to the stretch components*/ +@d shrinking 2 /*glue setting applies to the shrink components*/ +@d glue_offset 6 /*position of |glue_set| in a box node*/ +@d glue_set(A) mem[A+glue_offset].gr + /*a word of type |glue_ratio| for glue setting*/ + +@ The |new_null_box| function returns a pointer to an |hlist_node| in +which all subfields have the values corresponding to `\.{\\hbox\{\}}'. +(The |subtype| field is set to |min_quarterword|, for historic reasons +that are no longer relevant.) + +@p static pointer new_null_box(void) /*creates a new box node*/ +{@+pointer p; /*the new node*/ +p=get_node(box_node_size);type(p)=hlist_node; +subtype(p)=min_quarterword; +width(p)=0;depth(p)=0;height(p)=0;shift_amount(p)=0;list_ptr(p)=null; +glue_sign(p)=normal;glue_order(p)=normal;set_glue_ratio_zero(glue_set(p)); +return p; +} + +@ A |vlist_node| is like an |hlist_node| in all respects except that it +contains a vertical list. + +@d vlist_node 1 /*|type| of vlist nodes*/ + +@ A |rule_node| stands for a solid black rectangle; it has |width|, +|depth|, and |height| fields just as in an |hlist_node|. However, if +any of these dimensions is $-2^{30}$, the actual value will be determined +by running the rule up to the boundary of the innermost enclosing box. +This is called a ``running dimension.'' The |width| is never running in +an hlist; the |height| and |depth| are never running in a~vlist. + +@d rule_node 2 /*|type| of rule nodes*/ +@d rule_node_size 4 /*number of words to allocate for a rule node*/ +@d null_flag -010000000000 /*$-2^{30}$, signifies a missing item*/ +@d is_running(A) (A==null_flag) /*tests for a running dimension*/ + +@ A new rule node is delivered by the |new_rule| function. It +makes all the dimensions ``running,'' so you have to change the +ones that are not allowed to run. + +@p static pointer new_rule(void) +{@+pointer p; /*the new node*/ +p=get_node(rule_node_size);type(p)=rule_node; +subtype(p)=0; /*the |subtype| is not used*/ +width(p)=null_flag;depth(p)=null_flag;height(p)=null_flag; +return p; +} + +@ Insertions are represented by |ins_node| records, where the |subtype| +indicates the corresponding box number. For example, `\.{\\insert 250}' +leads to an |ins_node| whose |subtype| is |250+min_quarterword|. +The |height| field of an |ins_node| is slightly misnamed; it actually holds +the natural height plus depth of the vertical list being inserted. +The |depth| field holds the |split_max_depth| to be used in case this +insertion is split, and the |split_top_ptr| points to the corresponding +|split_top_skip|. The |float_cost| field holds the |floating_penalty| that +will be used if this insertion floats to a subsequent page after a +split insertion of the same class. There is one more field, the +|ins_ptr|, which points to the beginning of the vlist for the insertion. + +@d ins_node 3 /*|type| of insertion nodes*/ +@d ins_node_size 5 /*number of words to allocate for an insertion*/ +@d float_cost(A) mem[A+1].i /*the |floating_penalty| to be used*/ +@d ins_ptr(A) info(A+4) /*the vertical list to be inserted*/ +@d split_top_ptr(A) link(A+4) /*the |split_top_skip| to be used*/ + +@ A |mark_node| has a |mark_ptr| field that points to the reference count +of a token list that contains the user's \.{\\mark} text. +In addition there is a |mark_class| field that contains the mark class. + +@d mark_node 4 /*|type| of a mark node*/ +@d small_node_size 2 /*number of words to allocate for most node types*/ +@d mark_ptr(A) link(A+1) /*head of the token list for a mark*/ +@d mark_class(A) info(A+1) /*the mark class*/ + +@ An |adjust_node|, which occurs only in horizontal lists, +specifies material that will be moved out into the surrounding +vertical list; i.e., it is used to implement \TeX's `\.{\\vadjust}' +operation. The |adjust_ptr| field points to the vlist containing this +material. + +@d adjust_node 5 /*|type| of an adjust node*/ +@d adjust_ptr(A) mem[A+1].i + /*vertical list to be moved out of horizontal list*/ + +@ A |ligature_node|, which occurs only in horizontal lists, specifies +a character that was fabricated from the interaction of two or more +actual characters. The second word of the node, which is called the +|lig_char| word, contains |font| and |character| fields just as in a +|char_node|. The characters that generated the ligature have not been +forgotten, since they are needed for diagnostic messages and for +hyphenation; the |lig_ptr| field points to a linked list of character +nodes for all original characters that have been deleted. (This list +might be empty if the characters that generated the ligature were +retained in other nodes.) + +The |subtype| field is 0, plus 2 and/or 1 if the original source of the +ligature included implicit left and/or right boundaries. + +@d ligature_node 6 /*|type| of a ligature node*/ +@d lig_char(A) A+1 /*the word where the ligature is to be found*/ +@d lig_ptr(A) link(lig_char(A)) /*the list of characters*/ + +@ The |new_ligature| function creates a ligature node having given +contents of the |font|, |character|, and |lig_ptr| fields. We also have +a |new_lig_item| function, which returns a two-word node having a given +|character| field. Such nodes are used for temporary processing as ligatures +are being created. + +@p static pointer new_ligature(quarterword @!f, quarterword @!c, pointer @!q) +{@+pointer p; /*the new node*/ +p=get_node(small_node_size);type(p)=ligature_node; +font(lig_char(p))=f;character(lig_char(p))=c;lig_ptr(p)=q; +subtype(p)=0;return p; +} +@# +static pointer new_lig_item(quarterword @!c) +{@+pointer p; /*the new node*/ +p=get_node(small_node_size);character(p)=c;lig_ptr(p)=null; +return p; +} + +@ A |disc_node|, which occurs only in horizontal lists, specifies a +``dis\-cretion\-ary'' line break. If such a break occurs at node |p|, the text +that starts at |pre_break(p)| will precede the break, the text that starts at +|post_break(p)| will follow the break, and text that appears in the next +|replace_count(p)| nodes will be ignored. For example, an ordinary +discretionary hyphen, indicated by `\.{\\-}', yields a |disc_node| with +|pre_break| pointing to a |char_node| containing a hyphen, |post_break==null|, +and |replace_count==0|. All three of the discretionary texts must be +lists that consist entirely of character, kern, box, rule, and ligature nodes. + +If |pre_break(p)==null|, the |ex_hyphen_penalty| will be charged for this +break. Otherwise the |hyphen_penalty| will be charged. The texts will +actually be substituted into the list by the line-breaking algorithm if it +decides to make the break, and the discretionary node will disappear at +that time; thus, the output routine sees only discretionaries that were +not chosen. + +@d disc_node 7 /*|type| of a discretionary node*/ +@d replace_count(A) subtype(A) /*how many subsequent nodes to replace*/ +@d pre_break(A) llink(A) /*text that precedes a discretionary break*/ +@d post_break(A) rlink(A) /*text that follows a discretionary break*/ + +@p static pointer new_disc(void) /*creates an empty |disc_node|*/ +{@+pointer p; /*the new node*/ +p=get_node(small_node_size);type(p)=disc_node; +replace_count(p)=0;pre_break(p)=null;post_break(p)=null; +return p; +} + +@ A |whatsit_node| is a wild card reserved for extensions to \TeX. The +|subtype| field in its first word says what `\\{whatsit}' it is, and +implicitly determines the node size (which must be 2 or more) and the +format of the remaining words. When a |whatsit_node| is encountered +in a list, special actions are invoked; knowledgeable people who are +careful not to mess up the rest of \TeX\ are able to make \TeX\ do new +things by adding code at the end of the program. For example, there +might be a `\TeX nicolor' extension to specify different colors of ink, +@^extensions to \TeX@> +and the whatsit node might contain the desired parameters. + +The present implementation of \TeX\ treats the features associated with +`\.{\\write}' and `\.{\\special}' as if they were extensions, in order to +illustrate how such routines might be coded. We shall defer further +discussion of extensions until the end of this program. + +@d whatsit_node 8 /*|type| of special extension nodes*/ + +@ A |math_node|, which occurs only in horizontal lists, appears before and +after mathematical formulas. The |subtype| field is |before| before the +formula and |after| after it. There is a |width| field, which represents +the amount of surrounding space inserted by \.{\\mathsurround}. + +@d math_node 9 /*|type| of a math node*/ +@d before 0 /*|subtype| for math node that introduces a formula*/ +@d after 1 /*|subtype| for math node that winds up a formula*/ + +@p static pointer new_math(scaled @!w, small_number @!s) +{@+pointer p; /*the new node*/ +p=get_node(small_node_size);type(p)=math_node; +subtype(p)=s;width(p)=w;return p; +} + +@ \TeX\ makes use of the fact that |hlist_node|, |vlist_node|, +|rule_node|, |ins_node|, |mark_node|, |adjust_node|, |ligature_node|, +|disc_node|, |whatsit_node|, and |math_node| are at the low end of the +type codes, by permitting a break at glue in a list if and only if the +|type| of the previous node is less than |math_node|. Furthermore, a +node is discarded after a break if its type is |math_node| or~more. + +@d precedes_break(A) (type(A) < math_node) +@d non_discardable(A) (type(A) < math_node) + +@ A |glue_node| represents glue in a list. However, it is really only +a pointer to a separate glue specification, since \TeX\ makes use of the +fact that many essentially identical nodes of glue are usually present. +If |p| points to a |glue_node|, |glue_ptr(p)| points to +another packet of words that specify the stretch and shrink components, etc. + +Glue nodes also serve to represent leaders; the |subtype| is used to +distinguish between ordinary glue (which is called |normal|) and the three +kinds of leaders (which are called |a_leaders|, |c_leaders|, and |x_leaders|). +The |leader_ptr| field points to a rule node or to a box node containing the +leaders; it is set to |null| in ordinary glue nodes. + +Many kinds of glue are computed from \TeX's ``skip'' parameters, and +it is helpful to know which parameter has led to a particular glue node. +Therefore the |subtype| is set to indicate the source of glue, whenever +it originated as a parameter. We will be defining symbolic names for the +parameter numbers later (e.g., |line_skip_code==0|, |baseline_skip_code==1|, +etc.); it suffices for now to say that the |subtype| of parametric glue +will be the same as the parameter number, plus~one. + +In math formulas there are two more possibilities for the |subtype| in a +glue node: |mu_glue| denotes an \.{\\mskip} (where the units are scaled \.{mu} +instead of scaled \.{pt}); and |cond_math_glue| denotes the `\.{\\nonscript}' +feature that cancels the glue node immediately following if it appears +in a subscript. + +@d glue_node 10 /*|type| of node that points to a glue specification*/ +@d cond_math_glue 98 /*special |subtype| to suppress glue in the next node*/ +@d mu_glue 99 /*|subtype| for math glue*/ +@d a_leaders 100 /*|subtype| for aligned leaders*/ +@d c_leaders 101 /*|subtype| for centered leaders*/ +@d x_leaders 102 /*|subtype| for expanded leaders*/ +@d glue_ptr(A) llink(A) /*pointer to a glue specification*/ +@d leader_ptr(A) rlink(A) /*pointer to box or rule node for leaders*/ + +@ A glue specification has a halfword reference count in its first word, +@^reference counts@> +representing |null| plus the number of glue nodes that point to it (less one). +Note that the reference count appears in the same position as +the |link| field in list nodes; this is the field that is initialized +to |null| when a node is allocated, and it is also the field that is flagged +by |empty_flag| in empty nodes. + +Glue specifications also contain three |scaled| fields, for the |width|, +|stretch|, and |shrink| dimensions. Finally, there are two one-byte +fields called |stretch_order| and |shrink_order|; these contain the +orders of infinity (|normal|, |fil|, |fill|, or |filll|) +corresponding to the stretch and shrink values. + +@d glue_spec_size 4 /*number of words to allocate for a glue specification*/ +@d glue_ref_count(A) link(A) /*reference count of a glue specification*/ +@d stretch(A) mem[A+2].sc /*the stretchability of this glob of glue*/ +@d shrink(A) mem[A+3].sc /*the shrinkability of this glob of glue*/ +@d stretch_order(A) type(A) /*order of infinity for stretching*/ +@d shrink_order(A) subtype(A) /*order of infinity for shrinking*/ +@d fil 1 /*first-order infinity*/ +@d fill 2 /*second-order infinity*/ +@d filll 3 /*third-order infinity*/ + +@<Types...@>= +typedef int8_t glue_ord; /*infinity to the 0, 1, 2, or 3 power*/ + +@ Here is a function that returns a pointer to a copy of a glue spec. +The reference count in the copy is |null|, because there is assumed +to be exactly one reference to the new specification. + +@p static pointer new_spec(pointer @!p) /*duplicates a glue specification*/ +{@+pointer q; /*the new spec*/ +q=get_node(glue_spec_size);@/ +mem[q]=mem[p];glue_ref_count(q)=null;@/ +width(q)=width(p);stretch(q)=stretch(p);shrink(q)=shrink(p); +return q; +} + +@ And here's a function that creates a glue node for a given parameter +identified by its code number; for example, +|new_param_glue(line_skip_code)| returns a pointer to a glue node for the +current \.{\\lineskip}. + +@p static pointer new_param_glue(small_number @!n) +{@+pointer p; /*the new node*/ +pointer @!q; /*the glue specification*/ +p=get_node(small_node_size);type(p)=glue_node;subtype(p)=n+1; +leader_ptr(p)=null;@/ +q=@<Current |mem| equivalent of glue parameter number |n|@>@t@>; +glue_ptr(p)=q;incr(glue_ref_count(q)); +return p; +} + +@ Glue nodes that are more or less anonymous are created by |new_glue|, +whose argument points to a glue specification. + +@p static pointer new_glue(pointer @!q) +{@+pointer p; /*the new node*/ +p=get_node(small_node_size);type(p)=glue_node;subtype(p)=normal; +leader_ptr(p)=null;glue_ptr(p)=q;incr(glue_ref_count(q)); +return p; +} + +@ Still another subroutine is needed: This one is sort of a combination +of |new_param_glue| and |new_glue|. It creates a glue node for one of +the current glue parameters, but it makes a fresh copy of the glue +specification, since that specification will probably be subject to change, +while the parameter will stay put. The global variable |temp_ptr| is +set to the address of the new spec. + +@p static pointer new_skip_param(small_number @!n) +{@+pointer p; /*the new node*/ +temp_ptr=new_spec(@<Current |mem| equivalent of glue parameter...@>); +p=new_glue(temp_ptr);glue_ref_count(temp_ptr)=null;subtype(p)=n+1; +return p; +} + +@ A |kern_node| has a |width| field to specify a (normally negative) +amount of spacing. This spacing correction appears in horizontal lists +between letters like A and V when the font designer said that it looks +better to move them closer together or further apart. A kern node can +also appear in a vertical list, when its `|width|' denotes additional +spacing in the vertical direction. The |subtype| is either |normal| (for +kerns inserted from font information or math mode calculations) or |explicit| +(for kerns inserted from \.{\\kern} and \.{\\/} commands) or |acc_kern| +(for kerns inserted from non-math accents) or |mu_glue| (for kerns +inserted from \.{\\mkern} specifications in math formulas). + +@d kern_node 11 /*|type| of a kern node*/ +@d explicit 1 /*|subtype| of kern nodes from \.{\\kern} and \.{\\/}*/ +@d acc_kern 2 /*|subtype| of kern nodes from accents*/ + +@ The |new_kern| function creates a kern node having a given width. + +@p static pointer new_kern(scaled @!w) +{@+pointer p; /*the new node*/ +p=get_node(small_node_size);type(p)=kern_node; +subtype(p)=normal; +width(p)=w; +return p; +} + +@ A |penalty_node| specifies the penalty associated with line or page +breaking, in its |penalty| field. This field is a fullword integer, but +the full range of integer values is not used: Any penalty | >= 10000| is +treated as infinity, and no break will be allowed for such high values. +Similarly, any penalty | <= -10000| is treated as negative infinity, and a +break will be forced. + +@d penalty_node 12 /*|type| of a penalty node*/ +@d inf_penalty inf_bad /*``infinite'' penalty value*/ +@d eject_penalty (-inf_penalty) /*``negatively infinite'' penalty value*/ +@d penalty(A) mem[A+1].i /*the added cost of breaking a list here*/ + +@ Anyone who has been reading the last few sections of the program will +be able to guess what comes next. + +@p static pointer new_penalty(int @!m) +{@+pointer p; /*the new node*/ +p=get_node(small_node_size);type(p)=penalty_node; +subtype(p)=0; /*the |subtype| is not used*/ +penalty(p)=m;return p; +} + +@ You might think that we have introduced enough node types by now. Well, +almost, but there is one more: An |unset_node| has nearly the same format +as an |hlist_node| or |vlist_node|; it is used for entries in \.{\\halign} +or \.{\\valign} that are not yet in their final form, since the box +dimensions are their ``natural'' sizes before any glue adjustment has been +made. The |glue_set| word is not present; instead, we have a |glue_stretch| +field, which contains the total stretch of order |glue_order| that is +present in the hlist or vlist being boxed. +Similarly, the |shift_amount| field is replaced by a |glue_shrink| field, +containing the total shrink of order |glue_sign| that is present. +The |subtype| field is called |span_count|; an unset box typically +contains the data for |qo(span_count)+1| columns. +Unset nodes will be changed to box nodes when alignment is completed. + +@d unset_node 13 /*|type| for an unset node*/ +@d glue_stretch(A) mem[A+glue_offset].sc /*total stretch in an unset node*/ +@d glue_shrink(A) shift_amount(A) /*total shrink in an unset node*/ +@d span_count(A) subtype(A) /*indicates the number of spanned columns*/ + +@ In fact, there are still more types coming. When we get to math formula +processing we will see that a |style_node| has |type==14|; and a number +of larger type codes will also be defined, for use in math mode only. + +@ Warning: If any changes are made to these data structure layouts, such as +changing any of the node sizes or even reordering the words of nodes, +the |copy_node_list| procedure and the memory initialization code +below may have to be changed. Such potentially dangerous parts of the +program are listed in the index under `data structure assumptions'. +@!@^data structure assumptions@> +However, other references to the nodes are made symbolically in terms of +the \.{WEB} macro definitions above, so that format changes will leave +\TeX's other algorithms intact. +@^system dependencies@> + +@* Memory layout. +Some areas of |mem| are dedicated to fixed usage, since static allocation is +more efficient than dynamic allocation when we can get away with it. For +example, locations |mem_bot| to |mem_bot+3| are always used to store the +specification for glue that is `\.{0pt plus 0pt minus 0pt}'. The +following macro definitions accomplish the static allocation by giving +symbolic names to the fixed positions. Static variable-size nodes appear +in locations |mem_bot| through |lo_mem_stat_max|, and static single-word nodes +appear in locations |hi_mem_stat_min| through |mem_top|, inclusive. It is +harmless to let |lig_trick| and |garbage| share the same location of |mem|. + +@d zero_glue mem_bot /*specification for \.{0pt plus 0pt minus 0pt}*/ +@d fil_glue zero_glue+glue_spec_size /*\.{0pt plus 1fil minus 0pt}*/ +@d fill_glue fil_glue+glue_spec_size /*\.{0pt plus 1fill minus 0pt}*/ +@d ss_glue fill_glue+glue_spec_size /*\.{0pt plus 1fil minus 1fil}*/ +@d fil_neg_glue ss_glue+glue_spec_size /*\.{0pt plus -1fil minus 0pt}*/ +@d lo_mem_stat_max fil_neg_glue+glue_spec_size-1 /*largest statically + allocated word in the variable-size |mem|*/ +@# +@d page_ins_head mem_top /*list of insertion data for current page*/ +@d contrib_head mem_top-1 /*vlist of items not yet on current page*/ +@d page_head mem_top-2 /*vlist for current page*/ +@d temp_head mem_top-3 /*head of a temporary list of some kind*/ +@d hold_head mem_top-4 /*head of a temporary list of another kind*/ +@d adjust_head mem_top-5 /*head of adjustment list returned by |hpack|*/ +@d active mem_top-7 /*head of active list in |line_break|, needs two words*/ +@d align_head mem_top-8 /*head of preamble list for alignments*/ +@d end_span mem_top-9 /*tail of spanned-width lists*/ +@d omit_template mem_top-10 /*a constant token list*/ +@d null_list mem_top-11 /*permanently empty list*/ +@d lig_trick mem_top-12 /*a ligature masquerading as a |char_node|*/ +@d garbage mem_top-12 /*used for scrap information*/ +@d backup_head mem_top-13 /*head of token list built by |scan_keyword|*/ +@d hi_mem_stat_min mem_top-13 /*smallest statically allocated word in + the one-word |mem|*/ +@d hi_mem_stat_usage 14 /*the number of one-word nodes always present*/ + +@ The following code gets |mem| off to a good start, when \TeX\ is +initializing itself the slow~way. + +@<Local variables for init...@>= +int @!k; /*index into |mem|, |eqtb|, etc.*/ + +@ @<Initialize table entries...@>= +for (k=mem_bot+1; k<=lo_mem_stat_max; k++) mem[k].sc=0; + /*all glue dimensions are zeroed*/ +@^data structure assumptions@> +k=mem_bot;@+while (k <= lo_mem_stat_max) + /*set first words of glue specifications*/ + {@+glue_ref_count(k)=null+1; + stretch_order(k)=normal;shrink_order(k)=normal; + k=k+glue_spec_size; + } +stretch(fil_glue)=unity;stretch_order(fil_glue)=fil;@/ +stretch(fill_glue)=unity;stretch_order(fill_glue)=fill;@/ +stretch(ss_glue)=unity;stretch_order(ss_glue)=fil;@/ +shrink(ss_glue)=unity;shrink_order(ss_glue)=fil;@/ +stretch(fil_neg_glue)=-unity;stretch_order(fil_neg_glue)=fil;@/ +rover=lo_mem_stat_max+1; +link(rover)=empty_flag; /*now initialize the dynamic memory*/ +node_size(rover)=1000; /*which is a 1000-word available node*/ +llink(rover)=rover;rlink(rover)=rover;@/ +lo_mem_max=rover+1000;link(lo_mem_max)=null;info(lo_mem_max)=null;@/ +for (k=hi_mem_stat_min; k<=mem_top; k++) + mem[k]=mem[lo_mem_max]; /*clear list heads*/ +@<Initialize the special list heads and constant nodes@>; +avail=null;mem_end=mem_top; +hi_mem_min=hi_mem_stat_min; /*initialize the one-word memory*/ +var_used=lo_mem_stat_max+1-mem_bot;dyn_used=hi_mem_stat_usage; + /*initialize statistics*/ + +@ If \TeX\ is extended improperly, the |mem| array might get screwed up. +For example, some pointers might be wrong, or some ``dead'' nodes might not +have been freed when the last reference to them disappeared. Procedures +|check_mem| and |search_mem| are available to help diagnose such +problems. These procedures make use of two arrays called |is_free| and +|was_free| that are present only if \TeX's debugging routines have +been included. (You may want to decrease the size of |mem| while you +@^debugging@> +are debugging.) + +@<Glob...@>= +#ifdef @!DEBUG +static bool @!is_free0[mem_max-mem_min+1], + *const @!is_free = @!is_free0-mem_min; /*free cells*/ +@t\hskip10pt@>static bool @!was_free0[mem_max-mem_min+1], + *const @!was_free = @!was_free0-mem_min; + /*previously free cells*/ +@t\hskip10pt@>static pointer @!was_mem_end, @!was_lo_max, @!was_hi_min; + /*previous |mem_end|, |lo_mem_max|, and |hi_mem_min|*/ +@t\hskip10pt@>static bool @!panicking; /*do we want to check memory constantly?*/ +#endif + +@ @<Set initial...@>= +#ifdef @!DEBUG +was_mem_end=mem_min; /*indicate that everything was previously free*/ +was_lo_max=mem_min;was_hi_min=mem_max; +panicking=false; +#endif + +@ Procedure |check_mem| makes sure that the available space lists of +|mem| are well formed, and it optionally prints out all locations +that are reserved now but were free the last time this procedure was called. + +@p +#ifdef @!DEBUG +static void check_mem(bool @!print_locs) +{@+ /*loop exits*/ +int p, @!q; /*current locations of interest in |mem|*/ +bool @!clobbered; /*is something amiss?*/ +for (p=mem_min; p<=lo_mem_max; p++) is_free[p]=false; /*you can probably + do this faster*/ +for (p=hi_mem_min; p<=mem_end; p++) is_free[p]=false; /*ditto*/ +@<Check single-word |avail| list@>; +@<Check variable-size |avail| list@>; +@<Check flags of unavailable nodes@>; +if (print_locs) @<Print newly busy locations@>; +for (p=mem_min; p<=lo_mem_max; p++) was_free[p]=is_free[p]; +for (p=hi_mem_min; p<=mem_end; p++) was_free[p]=is_free[p]; + /*|was_free=is_free| might be faster*/ +was_mem_end=mem_end;was_lo_max=lo_mem_max;was_hi_min=hi_mem_min; +} +#endif + +@ @<Check single-word...@>= +p=avail;q=null;clobbered=false; +while (p!=null) + {@+if ((p > mem_end)||(p < hi_mem_min)) clobbered=true; + else if (is_free[p]) clobbered=true; + if (clobbered) + {@+print_nl("AVAIL list clobbered at "); +@.AVAIL list clobbered...@> + print_int(q);goto done1; + } + is_free[p]=true;q=p;p=link(q); + } +done1: + +@ @<Check variable-size...@>= +p=rover;q=null;clobbered=false; +@/do@+{if ((p >= lo_mem_max)||(p < mem_min)) clobbered=true; + else if ((rlink(p) >= lo_mem_max)||(rlink(p) < mem_min)) clobbered=true; + else if (!(is_empty(p))||(node_size(p) < 2)||@| + (p+node_size(p) > lo_mem_max)||@|(llink(rlink(p))!=p)) clobbered=true; + if (clobbered) + {@+print_nl("Double-AVAIL list clobbered at "); + print_int(q);goto done2; + } +for (q=p; q<=p+node_size(p)-1; q++) /*mark all locations free*/ + {@+if (is_free[q]) + {@+print_nl("Doubly free location at "); +@.Doubly free location...@> + print_int(q);goto done2; + } + is_free[q]=true; + } +q=p;p=rlink(p); +}@+ while (!(p==rover)); +done2: + +@ @<Check flags...@>= +p=mem_min; +while (p <= lo_mem_max) /*node |p| should not be empty*/ + {@+if (is_empty(p)) + {@+print_nl("Bad flag at ");print_int(p); +@.Bad flag...@> + } + while ((p <= lo_mem_max)&&!is_free[p]) incr(p); + while ((p <= lo_mem_max)&&is_free[p]) incr(p); + } + +@ @<Print newly busy...@>= +{@+print_nl("New busy locs:"); +for (p=mem_min; p<=lo_mem_max; p++) + if (!is_free[p]&&((p > was_lo_max)||was_free[p])) + {@+print_char(' ');print_int(p); + } +for (p=hi_mem_min; p<=mem_end; p++) + if (!is_free[p]&& + ((p < was_hi_min)||(p > was_mem_end)||was_free[p])) + {@+print_char(' ');print_int(p); + } +} + +@ The |search_mem| procedure attempts to answer the question ``Who points +to node~|p|?'' In doing so, it fetches |link| and |info| fields of |mem| +that might not be of type |two_halves|. Strictly speaking, this is +@^dirty \PASCAL@> +undefined in \PASCAL, and it can lead to ``false drops'' (words that seem to +point to |p| purely by coincidence). But for debugging purposes, we want +to rule out the places that do {\sl not\/} point to |p|, so a few false +drops are tolerable. + +@p +#ifdef @!DEBUG +static void search_mem(pointer @!p) /*look for pointers to |p|*/ +{@+int q; /*current position being searched*/ +for (q=mem_min; q<=lo_mem_max; q++) + {@+if (link(q)==p) + {@+print_nl("LINK(");print_int(q);print_char(')'); + } + if (info(q)==p) + {@+print_nl("INFO(");print_int(q);print_char(')'); + } + } +for (q=hi_mem_min; q<=mem_end; q++) + {@+if (link(q)==p) + {@+print_nl("LINK(");print_int(q);print_char(')'); + } + if (info(q)==p) + {@+print_nl("INFO(");print_int(q);print_char(')'); + } + } +@<Search |eqtb| for equivalents equal to |p|@>; +@<Search |save_stack| for equivalents that point to |p|@>; +@<Search |hyph_list| for pointers to |p|@>; +} +#endif + +@* Displaying boxes. +We can reinforce our knowledge of the data structures just introduced +by considering two procedures that display a list in symbolic form. +The first of these, called |short_display|, is used in ``overfull box'' +messages to give the top-level description of a list. The other one, +called |show_node_list|, prints a detailed description of exactly what +is in the data structure. + +The philosophy of |short_display| is to ignore the fine points about exactly +what is inside boxes, except that ligatures and discretionary breaks are +expanded. As a result, |short_display| is a recursive procedure, but the +recursion is never more than one level deep. +@^recursion@> + +A global variable |font_in_short_display| keeps track of the font code that +is assumed to be present when |short_display| begins; deviations from this +font will be printed. + +@<Glob...@>= +static int @!font_in_short_display; /*an internal font number*/ + +@ Boxes, rules, inserts, whatsits, marks, and things in general that are +sort of ``complicated'' are indicated only by printing `\.{[]}'. + +@p static void short_display(int @!p) /*prints highlights of list |p|*/ +{@+int n; /*for replacement counts*/ +while (p > mem_min) + {@+if (is_char_node(p)) + {@+if (p <= mem_end) + {@+if (font(p)!=font_in_short_display) + {@+if ((font(p) < font_base)||(font(p) > font_max)) + print_char('*'); +@.*\relax@> + else@<Print the font identifier for |font(p)|@>; + print_char(' ');font_in_short_display=font(p); + } + print_ASCII(qo(character(p))); + } + } + else@<Print a short indication of the contents of node |p|@>; + p=link(p); + } +} + +@ @<Print a short indication of the contents of node |p|@>= +switch (type(p)) { +case hlist_node: case vlist_node: case ins_node: + case whatsit_node: case mark_node: case adjust_node: + case unset_node: print("[]");@+break; +case rule_node: print_char('|');@+break; +case glue_node: if (glue_ptr(p)!=zero_glue) print_char(' ');@+break; +case math_node: print_char('$');@+break; +case ligature_node: short_display(lig_ptr(p));@+break; +case disc_node: {@+short_display(pre_break(p)); + short_display(post_break(p));@/ + n=replace_count(p); + while (n > 0) + {@+if (link(p)!=null) p=link(p); + decr(n); + } + } @+break; +default:do_nothing; +} + +@ The |show_node_list| routine requires some auxiliary subroutines: one to +print a font-and-character combination, one to print a token list without +its reference count, and one to print a rule dimension. + +@p static void print_font_and_char(int @!p) /*prints |char_node| data*/ +{@+if (p > mem_end) print_esc("CLOBBERED."); +else{@+if ((font(p) < font_base)||(font(p) > font_max)) print_char('*'); +@.*\relax@> + else@<Print the font identifier for |font(p)|@>; + print_char(' ');print_ASCII(qo(character(p))); + } +} +@# +static void print_mark(int @!p) /*prints token list data in braces*/ +{@+print_char('{'); +if ((p < hi_mem_min)||(p > mem_end)) print_esc("CLOBBERED."); +else show_token_list(link(p), null, max_print_line-10); +print_char('}'); +} +@# +static void print_rule_dimen(scaled @!d) /*prints dimension in rule node*/ +{@+if (is_running(d)) print_char('*');else print_scaled(d); +@.*\relax@> +} + +@ Then there is a subroutine that prints glue stretch and shrink, possibly +followed by the name of finite units: + +@p static void print_glue(scaled @!d, int @!order, char *@!s) + /*prints a glue component*/ +{@+print_scaled(d); +if ((order < normal)||(order > filll)) print("foul"); +else if (order > normal) + {@+print("fil"); + while (order > fil) + {@+print_char('l');decr(order); + } + } +else if (s!=0) print(s); +} + +@ The next subroutine prints a whole glue specification. + +@p static void print_spec(int @!p, char *@!s) + /*prints a glue specification*/ +{@+if ((p < mem_min)||(p >= lo_mem_max)) print_char('*'); +@.*\relax@> +else{@+print_scaled(width(p)); + if (s!=0) print(s); + if (stretch(p)!=0) + {@+print(" plus ");print_glue(stretch(p), stretch_order(p), s); + } + if (shrink(p)!=0) + {@+print(" minus ");print_glue(shrink(p), shrink_order(p), s); + } + } +} + +@ We also need to declare some procedures that appear later in this +documentation. + +@p @<Declare procedures needed for displaying the elements of mlists@>@; +@<Declare the procedure called |print_skip_param|@>@; + +@ Since boxes can be inside of boxes, |show_node_list| is inherently recursive, +@^recursion@> +up to a given maximum number of levels. The history of nesting is indicated +by the current string, which will be printed at the beginning of each line; +the length of this string, namely |cur_length|, is the depth of nesting. + +Recursive calls on |show_node_list| therefore use the following pattern: + +@d node_list_display(A) + {@+append_char('.');show_node_list(A);flush_char; + } /*|str_room| need not be checked; see |show_box| below*/ + +@ A global variable called |depth_threshold| is used to record the maximum +depth of nesting for which |show_node_list| will show information. If we +have |depth_threshold==0|, for example, only the top level information will +be given and no sublists will be traversed. Another global variable, called +|breadth_max|, tells the maximum number of items to show at each level; +|breadth_max| had better be positive, or you won't see anything. + +@<Glob...@>= +static int @!depth_threshold; /*maximum nesting depth in box displays*/ +static int @!breadth_max; /*maximum number of items shown at the same list level*/ + +@ Now we are ready for |show_node_list| itself. This procedure has been +written to be ``extra robust'' in the sense that it should not crash or get +into a loop even if the data structures have been messed up by bugs in +the rest of the program. You can safely call its parent routine +|show_box(p)| for arbitrary values of |p| when you are debugging \TeX. +However, in the presence of bad data, the procedure may +@^dirty \PASCAL@>@^debugging@> +fetch a |memory_word| whose variant is different from the way it was stored; +for example, it might try to read |mem[p].hh| when |mem[p]| +contains a scaled integer, if |p| is a pointer that has been +clobbered or chosen at random. + +@p static void show_node_list(int @!p) /*prints a node list symbolically*/ +{@+ +int n; /*the number of items already printed at this level*/ +double @!g; /*a glue ratio, as a floating point number*/ +if (cur_length > depth_threshold) + {@+if (p > null) print(" []"); + /*indicate that there's been some truncation*/ + return; + } +n=0; +while (p > mem_min) + {@+print_ln();print_current_string(); /*display the nesting history*/ + if (p > mem_end) /*pointer out of range*/ + {@+print("Bad link, display aborted.");return; +@.Bad link...@> + } + incr(n);if (n > breadth_max) /*time to stop*/ + {@+print("etc.");return; +@.etc@> + } + @<Display node |p|@>; + p=link(p); + } + +} + +@ @<Display node |p|@>= +if (is_char_node(p)) print_font_and_char(p); +else switch (type(p)) { + case hlist_node: case vlist_node: case unset_node: @<Display box |p|@>@;@+break; + case rule_node: @<Display rule |p|@>@;@+break; + case ins_node: @<Display insertion |p|@>@;@+break; + case whatsit_node: @<Display the whatsit node |p|@>@;@+break; + case glue_node: @<Display glue |p|@>@;@+break; + case kern_node: @<Display kern |p|@>@;@+break; + case math_node: @<Display math node |p|@>@;@+break; + case ligature_node: @<Display ligature |p|@>@;@+break; + case penalty_node: @<Display penalty |p|@>@;@+break; + case disc_node: @<Display discretionary |p|@>@;@+break; + case mark_node: @<Display mark |p|@>@;@+break; + case adjust_node: @<Display adjustment |p|@>@;@+break; + @t\4@>@<Cases of |show_node_list| that arise in mlists only@>@; + default:print("Unknown node type!"); + } + +@ @<Display box |p|@>= +{@+if (type(p)==hlist_node) print_esc("h"); +else if (type(p)==vlist_node) print_esc("v"); +else print_esc("unset"); +print("box(");print_scaled(height(p));print_char('+'); +print_scaled(depth(p));print(")x");print_scaled(width(p)); +if (type(p)==unset_node) + @<Display special fields of the unset node |p|@>@; +else{@+@<Display the value of |glue_set(p)|@>; + if (shift_amount(p)!=0) + {@+print(", shifted ");print_scaled(shift_amount(p)); + } + } +node_list_display(list_ptr(p)); /*recursive call*/ +} + +@ @<Display special fields of the unset node |p|@>= +{@+if (span_count(p)!=min_quarterword) + {@+print(" (");print_int(qo(span_count(p))+1); + print(" columns)"); + } +if (glue_stretch(p)!=0) + {@+print(", stretch ");print_glue(glue_stretch(p), glue_order(p), 0); + } +if (glue_shrink(p)!=0) + {@+print(", shrink ");print_glue(glue_shrink(p), glue_sign(p), 0); + } +} + +@ The code will have to change in this place if |glue_ratio| is +a structured type instead of an ordinary |double|. Note that this routine +should avoid arithmetic errors even if the |glue_set| field holds an +arbitrary random value. The following code assumes that a properly +formed nonzero |double| number has absolute value $2^{20}$ or more when +it is regarded as an integer; this precaution was adequate to prevent +floating point underflow on the author's computer. +@^system dependencies@> +@^dirty \PASCAL@> + +@<Display the value of |glue_set(p)|@>= +g=unfix(glue_set(p)); +if ((g!=float_constant(0))&&(glue_sign(p)!=normal)) + {@+print(", glue set "); + if (glue_sign(p)==shrinking) print("- "); + if (abs(mem[p+glue_offset].i) < 04000000) print("?.?"); + else if (abs(g) > float_constant(20000)) + {@+if (g > float_constant(0)) print_char('>'); + else print("< -"); + print_glue(20000*unity, glue_order(p), 0); + } + else print_glue(round(unity*g), glue_order(p), 0); +@^real multiplication@> + } + +@ @<Display rule |p|@>= +{@+print_esc("rule(");print_rule_dimen(height(p));print_char('+'); +print_rule_dimen(depth(p));print(")x");print_rule_dimen(width(p)); +} + +@ @<Display insertion |p|@>= +{@+print_esc("insert");print_int(qo(subtype(p))); +print(", natural size ");print_scaled(height(p)); +print("; split(");print_spec(split_top_ptr(p), 0); +print_char(',');print_scaled(depth(p)); +print("); float cost ");print_int(float_cost(p)); +node_list_display(ins_ptr(p)); /*recursive call*/ +} + +@ @<Display glue |p|@>= +if (subtype(p) >= a_leaders) @<Display leaders |p|@>@; +else{@+print_esc("glue"); + if (subtype(p)!=normal) + {@+print_char('('); + if (subtype(p) < cond_math_glue) + print_skip_param(subtype(p)-1); + else if (subtype(p)==cond_math_glue) print_esc("nonscript"); + else print_esc("mskip"); + print_char(')'); + } + if (subtype(p)!=cond_math_glue) + {@+print_char(' '); + if (subtype(p) < cond_math_glue) print_spec(glue_ptr(p), 0); + else print_spec(glue_ptr(p),"mu"); + } + } + +@ @<Display leaders |p|@>= +{@+print_esc(""); +if (subtype(p)==c_leaders) print_char('c'); +else if (subtype(p)==x_leaders) print_char('x'); +print("leaders ");print_spec(glue_ptr(p), 0); +node_list_display(leader_ptr(p)); /*recursive call*/ +} + +@ An ``explicit'' kern value is indicated implicitly by an explicit space. + +@<Display kern |p|@>= +if (subtype(p)!=mu_glue) + {@+print_esc("kern"); + if (subtype(p)!=normal) print_char(' '); + print_scaled(width(p)); + if (subtype(p)==acc_kern) print(" (for accent)"); +@.for accent@> + } +else{@+print_esc("mkern");print_scaled(width(p));print("mu"); + } + +@ @<Display math node |p|@>= +{@+print_esc("math"); +if (subtype(p)==before) print("on"); +else print("off"); +if (width(p)!=0) + {@+print(", surrounded ");print_scaled(width(p)); + } +} + +@ @<Display ligature |p|@>= +{@+print_font_and_char(lig_char(p));print(" (ligature "); +if (subtype(p) > 1) print_char('|'); +font_in_short_display=font(lig_char(p));short_display(lig_ptr(p)); +if (odd(subtype(p))) print_char('|'); +print_char(')'); +} + +@ @<Display penalty |p|@>= +{@+print_esc("penalty ");print_int(penalty(p)); +} + +@ The |post_break| list of a discretionary node is indicated by a prefixed +`\.{\char'174}' instead of the `\..' before the |pre_break| list. + +@<Display discretionary |p|@>= +{@+print_esc("discretionary"); +if (replace_count(p) > 0) + {@+print(" replacing ");print_int(replace_count(p)); + } +node_list_display(pre_break(p)); /*recursive call*/ +append_char('|');show_node_list(post_break(p));flush_char; /*recursive call*/ +} + +@ @<Display mark |p|@>= +{@+print_esc("mark"); +if (mark_class(p)!=0) + {@+print_char('s');print_int(mark_class(p)); + } +print_mark(mark_ptr(p)); +} + +@ @<Display adjustment |p|@>= +{@+print_esc("vadjust");node_list_display(adjust_ptr(p)); /*recursive call*/ +} + +@ The recursive machinery is started by calling |show_box|. +@^recursion@> + +@p static void show_box(pointer @!p) +{@+@<Assign the values |depth_threshold:=show_box_depth| and |breadth_max:=show_box_breadth|@>; +if (breadth_max <= 0) breadth_max=5; +if (pool_ptr+depth_threshold >= pool_size) + depth_threshold=pool_size-pool_ptr-1; + /*now there's enough room for prefix string*/ +show_node_list(p); /*the show starts at |p|*/ +print_ln(); +} + +@* Destroying boxes. +When we are done with a node list, we are obliged to return it to free +storage, including all of its sublists. The recursive procedure +|flush_node_list| does this for us. + +@ First, however, we shall consider two non-recursive procedures that do +simpler tasks. The first of these, |delete_token_ref|, is called when +a pointer to a token list's reference count is being removed. This means +that the token list should disappear if the reference count was |null|, +otherwise the count should be decreased by one. +@^reference counts@> + +@d token_ref_count(A) info(A) /*reference count preceding a token list*/ + +@p static void delete_token_ref(pointer @!p) /*|p| points to the reference count + of a token list that is losing one reference*/ +{@+if (token_ref_count(p)==null) flush_list(p); +else decr(token_ref_count(p)); +} + +@ Similarly, |delete_glue_ref| is called when a pointer to a glue +specification is being withdrawn. +@^reference counts@> +@d fast_delete_glue_ref(A) @t@>@;@/ + {@+if (glue_ref_count(A)==null) free_node(A, glue_spec_size); + else decr(glue_ref_count(A)); + } + +@p static void delete_glue_ref(pointer @!p) /*|p| points to a glue specification*/ +fast_delete_glue_ref(p) + +@ Now we are ready to delete any node list, recursively. +In practice, the nodes deleted are usually charnodes (about 2/3 of the time), +and they are glue nodes in about half of the remaining cases. +@^recursion@> + +@p static void flush_node_list(pointer @!p) /*erase list of nodes starting at |p|*/ +{@+ /*go here when node |p| has been freed*/ +pointer q; /*successor to node |p|*/ +while (p!=null) +@^inner loop@> + {@+q=link(p); + if (is_char_node(p)) free_avail(p)@; + else{@+switch (type(p)) { + case hlist_node: case vlist_node: + case unset_node: {@+flush_node_list(list_ptr(p)); + free_node(p, box_node_size);goto done; + } + case rule_node: {@+free_node(p, rule_node_size);goto done; + } + case ins_node: {@+flush_node_list(ins_ptr(p)); + delete_glue_ref(split_top_ptr(p)); + free_node(p, ins_node_size);goto done; + } + case whatsit_node: @<Wipe out the whatsit node |p| and |goto done|@>@; + case glue_node: {@+fast_delete_glue_ref(glue_ptr(p)); + if (leader_ptr(p)!=null) flush_node_list(leader_ptr(p)); + } @+break; + case kern_node: case math_node: case penalty_node: do_nothing;@+break; + case ligature_node: flush_node_list(lig_ptr(p));@+break; + case mark_node: delete_token_ref(mark_ptr(p));@+break; + case disc_node: {@+flush_node_list(pre_break(p)); + flush_node_list(post_break(p)); + } @+break; + case adjust_node: flush_node_list(adjust_ptr(p));@+break; + @t\4@>@<Cases of |flush_node_list| that arise in mlists only@>@; + default:confusion("flushing"); +@:this can't happen flushing}{\quad flushing@> + } @/ + free_node(p, small_node_size); + done: ;} + p=q; + } +} + +@* Copying boxes. +Another recursive operation that acts on boxes is sometimes needed: The +procedure |copy_node_list| returns a pointer to another node list that has +the same structure and meaning as the original. Note that since glue +specifications and token lists have reference counts, we need not make +copies of them. Reference counts can never get too large to fit in a +halfword, since each pointer to a node is in a different memory address, +and the total number of memory addresses fits in a halfword. +@^recursion@> +@^reference counts@> + +(Well, there actually are also references from outside |mem|; if the +|save_stack| is made arbitrarily large, it would theoretically be possible +to break \TeX\ by overflowing a reference count. But who would want to do that?) + +@d add_token_ref(A) incr(token_ref_count(A)) /*new reference to a token list*/ +@d add_glue_ref(A) incr(glue_ref_count(A)) /*new reference to a glue spec*/ + +@ The copying procedure copies words en masse without bothering +to look at their individual fields. If the node format changes---for +example, if the size is altered, or if some link field is moved to another +relative position---then this code may need to be changed too. +@^data structure assumptions@> + +@p static pointer copy_node_list(pointer @!p) /*makes a duplicate of the + node list that starts at |p| and returns a pointer to the new list*/ +{@+pointer h; /*temporary head of copied list*/ +pointer @!q; /*previous position in new list*/ +pointer @!r; /*current node being fabricated for new list*/ +int @!words; /*number of words remaining to be copied*/ +h=get_avail();q=h; +while (p!=null) + {@+@<Make a copy of node |p| in node |r|@>; + link(q)=r;q=r;p=link(p); + } +link(q)=null;q=link(h);free_avail(h); +return q; +} + +@ @<Make a copy of node |p|...@>= +words=1; /*this setting occurs in more branches than any other*/ +if (is_char_node(p)) r=get_avail(); +else@<Case statement to copy different types and set |words| to the number +of initial words not yet copied@>; +while (words > 0) + {@+decr(words);mem[r+words]=mem[p+words]; + } + +@ @<Case statement to copy...@>= +switch (type(p)) { +case hlist_node: case vlist_node: case unset_node: {@+r=get_node(box_node_size); + mem[r+6]=mem[p+6];mem[r+5]=mem[p+5]; /*copy the last two words*/ + list_ptr(r)=copy_node_list(list_ptr(p)); /*this affects |mem[r+5]|*/ + words=5; + } @+break; +case rule_node: {@+r=get_node(rule_node_size);words=rule_node_size; + } @+break; +case ins_node: {@+r=get_node(ins_node_size);mem[r+4]=mem[p+4]; + add_glue_ref(split_top_ptr(p)); + ins_ptr(r)=copy_node_list(ins_ptr(p)); /*this affects |mem[r+4]|*/ + words=ins_node_size-1; + } @+break; +case whatsit_node: @<Make a partial copy of the whatsit node |p| and make +|r| point to it; set |words| to the number of initial words not yet copied@>@;@+break; +case glue_node: {@+r=get_node(small_node_size);add_glue_ref(glue_ptr(p)); + glue_ptr(r)=glue_ptr(p);leader_ptr(r)=copy_node_list(leader_ptr(p)); + } @+break; +case kern_node: case math_node: case penalty_node: {@+r=get_node(small_node_size); + words=small_node_size; + } @+break; +case ligature_node: {@+r=get_node(small_node_size); + mem[lig_char(r)]=mem[lig_char(p)]; /*copy |font| and |character|*/ + lig_ptr(r)=copy_node_list(lig_ptr(p)); + } @+break; +case disc_node: {@+r=get_node(small_node_size); + pre_break(r)=copy_node_list(pre_break(p)); + post_break(r)=copy_node_list(post_break(p)); + } @+break; +case mark_node: {@+r=get_node(small_node_size);add_token_ref(mark_ptr(p)); + words=small_node_size; + } @+break; +case adjust_node: {@+r=get_node(small_node_size); + adjust_ptr(r)=copy_node_list(adjust_ptr(p)); + } @+break; /*|words==1==small_node_size-1|*/ +default:confusion("copying"); +@:this can't happen copying}{\quad copying@> +} + +@* The command codes. +Before we can go any further, we need to define symbolic names for the internal +code numbers that represent the various commands obeyed by \TeX. These codes +are somewhat arbitrary, but not completely so. For example, the command +codes for character types are fixed by the language, since a user says, +e.g., `\.{\\catcode \`\\\${} = 3}' to make \.{\char'44} a math delimiter, +and the command code |math_shift| is equal to~3. Some other codes have +been made adjacent so that |case| statements in the program need not consider +cases that are widely spaced, or so that |case| statements can be replaced +by |if| statements. + +At any rate, here is the list, for future reference. First come the +``catcode'' commands, several of which share their numeric codes with +ordinary commands when the catcode cannot emerge from \TeX's scanning routine. + +@d escape 0 /*escape delimiter (called \.\\ in {\sl The \TeX book\/})*/ +@:TeXbook}{\sl The \TeX book@> +@d relax 0 /*do nothing ( \.{\\relax} )*/ +@d left_brace 1 /*beginning of a group ( \.\{ )*/ +@d right_brace 2 /*ending of a group ( \.\} )*/ +@d math_shift 3 /*mathematics shift character ( \.\$ )*/ +@d tab_mark 4 /*alignment delimiter ( \.\&, \.{\\span} )*/ +@d car_ret 5 /*end of line ( |carriage_return|, \.{\\cr}, \.{\\crcr} )*/ +@d out_param 5 /*output a macro parameter*/ +@d mac_param 6 /*macro parameter symbol ( \.\# )*/ +@d sup_mark 7 /*superscript ( \.{\char'136} )*/ +@d sub_mark 8 /*subscript ( \.{\char'137} )*/ +@d ignore 9 /*characters to ignore ( \.{\^\^@@} )*/ +@d endv 9 /*end of \<v_j> list in alignment template*/ +@d spacer 10 /*characters equivalent to blank space ( \.{\ } )*/ +@d letter 11 /*characters regarded as letters ( \.{A..Z}, \.{a..z} )*/ +@d other_char 12 /*none of the special character types*/ +@d active_char 13 /*characters that invoke macros ( \.{\char`\~} )*/ +@d par_end 13 /*end of paragraph ( \.{\\par} )*/ +@d match 13 /*match a macro parameter*/ +@d comment 14 /*characters that introduce comments ( \.\% )*/ +@d end_match 14 /*end of parameters to macro*/ +@d stop 14 /*end of job ( \.{\\end}, \.{\\dump} )*/ +@d invalid_char 15 /*characters that shouldn't appear ( \.{\^\^?} )*/ +@d delim_num 15 /*specify delimiter numerically ( \.{\\delimiter} )*/ +@d max_char_code 15 /*largest catcode for individual characters*/ + +@ Next are the ordinary run-of-the-mill command codes. Codes that are +|min_internal| or more represent internal quantities that might be +expanded by `\.{\\the}'. + +@d char_num 16 /*character specified numerically ( \.{\\char} )*/ +@d math_char_num 17 /*explicit math code ( \.{\\mathchar} )*/ +@d mark 18 /*mark definition ( \.{\\mark} )*/ +@d xray 19 /*peek inside of \TeX\ ( \.{\\show}, \.{\\showbox}, etc.~)*/ +@d make_box 20 /*make a box ( \.{\\box}, \.{\\copy}, \.{\\hbox}, etc.~)*/ +@d hmove 21 /*horizontal motion ( \.{\\moveleft}, \.{\\moveright} )*/ +@d vmove 22 /*vertical motion ( \.{\\raise}, \.{\\lower} )*/ +@d un_hbox 23 /*unglue a box ( \.{\\unhbox}, \.{\\unhcopy} )*/ +@d un_vbox 24 /*unglue a box ( \.{\\unvbox}, \.{\\unvcopy} )*/ + /*( or \.{\\pagediscards}, \.{\\splitdiscards} )*/ +@d remove_item 25 /*nullify last item ( \.{\\unpenalty}, + \.{\\unkern}, \.{\\unskip} )*/ +@d hskip 26 /*horizontal glue ( \.{\\hskip}, \.{\\hfil}, etc.~)*/ +@d vskip 27 /*vertical glue ( \.{\\vskip}, \.{\\vfil}, etc.~)*/ +@d mskip 28 /*math glue ( \.{\\mskip} )*/ +@d kern 29 /*fixed space ( \.{\\kern} )*/ +@d mkern 30 /*math kern ( \.{\\mkern} )*/ +@d leader_ship 31 /*use a box ( \.{\\shipout}, \.{\\leaders}, etc.~)*/ +@d halign 32 /*horizontal table alignment ( \.{\\halign} )*/ +@d valign 33 /*vertical table alignment ( \.{\\valign} )*/ +@d no_align 34 /*temporary escape from alignment ( \.{\\noalign} )*/ +@d vrule 35 /*vertical rule ( \.{\\vrule} )*/ +@d hrule 36 /*horizontal rule ( \.{\\hrule} )*/ +@d insert 37 /*vlist inserted in box ( \.{\\insert} )*/ +@d vadjust 38 /*vlist inserted in enclosing paragraph ( \.{\\vadjust} )*/ +@d ignore_spaces 39 /*gobble |spacer| tokens ( \.{\\ignorespaces} )*/ +@d after_assignment 40 /*save till assignment is done ( \.{\\afterassignment} )*/ +@d after_group 41 /*save till group is done ( \.{\\aftergroup} )*/ +@d break_penalty 42 /*additional badness ( \.{\\penalty} )*/ +@d start_par 43 /*begin paragraph ( \.{\\indent}, \.{\\noindent} )*/ +@d ital_corr 44 /*italic correction ( \.{\\/} )*/ +@d accent 45 /*attach accent in text ( \.{\\accent} )*/ +@d math_accent 46 /*attach accent in math ( \.{\\mathaccent} )*/ +@d discretionary 47 /*discretionary texts ( \.{\\-}, \.{\\discretionary} )*/ +@d eq_no 48 /*equation number ( \.{\\eqno}, \.{\\leqno} )*/ +@d left_right 49 /*variable delimiter ( \.{\\left}, \.{\\right} )*/ + /*( or \.{\\middle} )*/ +@d math_comp 50 /*component of formula ( \.{\\mathbin}, etc.~)*/ +@d limit_switch 51 /*diddle limit conventions ( \.{\\displaylimits}, etc.~)*/ +@d above 52 /*generalized fraction ( \.{\\above}, \.{\\atop}, etc.~)*/ +@d math_style 53 /*style specification ( \.{\\displaystyle}, etc.~)*/ +@d math_choice 54 /*choice specification ( \.{\\mathchoice} )*/ +@d non_script 55 /*conditional math glue ( \.{\\nonscript} )*/ +@d vcenter 56 /*vertically center a vbox ( \.{\\vcenter} )*/ +@d case_shift 57 /*force specific case ( \.{\\lowercase}, \.{\\uppercase}~)*/ +@d message 58 /*send to user ( \.{\\message}, \.{\\errmessage} )*/ +@d extension 59 /*extensions to \TeX\ ( \.{\\write}, \.{\\special}, etc.~)*/ +@d in_stream 60 /*files for reading ( \.{\\openin}, \.{\\closein} )*/ +@d begin_group 61 /*begin local grouping ( \.{\\begingroup} )*/ +@d end_group 62 /*end local grouping ( \.{\\endgroup} )*/ +@d omit 63 /*omit alignment template ( \.{\\omit} )*/ +@d ex_space 64 /*explicit space ( \.{\\\ } )*/ +@d no_boundary 65 /*suppress boundary ligatures ( \.{\\noboundary} )*/ +@d radical 66 /*square root and similar signs ( \.{\\radical} )*/ +@d end_cs_name 67 /*end control sequence ( \.{\\endcsname} )*/ +@d min_internal 68 /*the smallest code that can follow \.{\\the}*/ +@d char_given 68 /*character code defined by \.{\\chardef}*/ +@d math_given 69 /*math code defined by \.{\\mathchardef}*/ +@d last_item 70 /*most recent item ( \.{\\lastpenalty}, + \.{\\lastkern}, \.{\\lastskip} )*/ +@d max_non_prefixed_command 70 /*largest command code that can't be \.{\\global}*/ + +@ The next codes are special; they all relate to mode-independent +assignment of values to \TeX's internal registers or tables. +Codes that are |max_internal| or less represent internal quantities +that might be expanded by `\.{\\the}'. + +@d toks_register 71 /*token list register ( \.{\\toks} )*/ +@d assign_toks 72 /*special token list ( \.{\\output}, \.{\\everypar}, etc.~)*/ +@d assign_int 73 /*user-defined integer ( \.{\\tolerance}, \.{\\day}, etc.~)*/ +@d assign_dimen 74 /*user-defined length ( \.{\\hsize}, etc.~)*/ +@d assign_glue 75 /*user-defined glue ( \.{\\baselineskip}, etc.~)*/ +@d assign_mu_glue 76 /*user-defined muglue ( \.{\\thinmuskip}, etc.~)*/ +@d assign_font_dimen 77 /*user-defined font dimension ( \.{\\fontdimen} )*/ +@d assign_font_int 78 /*user-defined font integer ( \.{\\hyphenchar}, + \.{\\skewchar} )*/ +@d set_aux 79 /*specify state info ( \.{\\spacefactor}, \.{\\prevdepth} )*/ +@d set_prev_graf 80 /*specify state info ( \.{\\prevgraf} )*/ +@d set_page_dimen 81 /*specify state info ( \.{\\pagegoal}, etc.~)*/ +@d set_page_int 82 /*specify state info ( \.{\\deadcycles}, + \.{\\insertpenalties} )*/ + /*( or \.{\\interactionmode} )*/ +@d set_box_dimen 83 /*change dimension of box ( \.{\\wd}, \.{\\ht}, \.{\\dp} )*/ +@d set_shape 84 /*specify fancy paragraph shape ( \.{\\parshape} )*/ + /*(or \.{\\interlinepenalties}, etc.~)*/ +@d def_code 85 /*define a character code ( \.{\\catcode}, etc.~)*/ +@d def_family 86 /*declare math fonts ( \.{\\textfont}, etc.~)*/ +@d set_font 87 /*set current font ( font identifiers )*/ +@d def_font 88 /*define a font file ( \.{\\font} )*/ +@d internal_register 89 /*internal register ( \.{\\count}, \.{\\dimen}, etc.~)*/ +@d max_internal 89 /*the largest code that can follow \.{\\the}*/ +@d advance 90 /*advance a register or parameter ( \.{\\advance} )*/ +@d multiply 91 /*multiply a register or parameter ( \.{\\multiply} )*/ +@d divide 92 /*divide a register or parameter ( \.{\\divide} )*/ +@d prefix 93 /*qualify a definition ( \.{\\global}, \.{\\long}, \.{\\outer} )*/ + /*( or \.{\\protected} )*/ +@d let 94 /*assign a command code ( \.{\\let}, \.{\\futurelet} )*/ +@d shorthand_def 95 /*code definition ( \.{\\chardef}, \.{\\countdef}, etc.~)*/ +@d read_to_cs 96 /*read into a control sequence ( \.{\\read} )*/ + /*( or \.{\\readline} )*/ +@d def 97 /*macro definition ( \.{\\def}, \.{\\gdef}, \.{\\xdef}, \.{\\edef} )*/ +@d set_box 98 /*set a box ( \.{\\setbox} )*/ +@d hyph_data 99 /*hyphenation data ( \.{\\hyphenation}, \.{\\patterns} )*/ +@d set_interaction 100 /*define level of interaction ( \.{\\batchmode}, etc.~)*/ +@d max_command 100 /*the largest command code seen at |big_switch|*/ + +@ The remaining command codes are extra special, since they cannot get through +\TeX's scanner to the main control routine. They have been given values higher +than |max_command| so that their special nature is easily discernible. +The ``expandable'' commands come first. + +@d undefined_cs (max_command+1) /*initial state of most |eq_type| fields*/ +@d expand_after (max_command+2) /*special expansion ( \.{\\expandafter} )*/ +@d no_expand (max_command+3) /*special nonexpansion ( \.{\\noexpand} )*/ +@d input (max_command+4) /*input a source file ( \.{\\input}, \.{\\endinput} )*/ + /*( or \.{\\scantokens} )*/ +@d if_test (max_command+5) /*conditional text ( \.{\\if}, \.{\\ifcase}, etc.~)*/ +@d fi_or_else (max_command+6) /*delimiters for conditionals ( \.{\\else}, etc.~)*/ +@d cs_name (max_command+7) /*make a control sequence from tokens ( \.{\\csname} )*/ +@d convert (max_command+8) /*convert to text ( \.{\\number}, \.{\\string}, etc.~)*/ +@d the (max_command+9) /*expand an internal quantity ( \.{\\the} )*/ + /*( or \.{\\unexpanded}, \.{\\detokenize} )*/ +@d top_bot_mark (max_command+10) /*inserted mark ( \.{\\topmark}, etc.~)*/ +@d call (max_command+11) /*non-long, non-outer control sequence*/ +@d long_call (max_command+12) /*long, non-outer control sequence*/ +@d outer_call (max_command+13) /*non-long, outer control sequence*/ +@d long_outer_call (max_command+14) /*long, outer control sequence*/ +@d end_template (max_command+15) /*end of an alignment template*/ +@d dont_expand (max_command+16) /*the following token was marked by \.{\\noexpand}*/ +@d glue_ref (max_command+17) /*the equivalent points to a glue specification*/ +@d shape_ref (max_command+18) /*the equivalent points to a parshape specification*/ +@d box_ref (max_command+19) /*the equivalent points to a box node, or is |null|*/ +@d data (max_command+20) /*the equivalent is simply a halfword number*/ + +@* The semantic nest. +\TeX\ is typically in the midst of building many lists at once. For example, +when a math formula is being processed, \TeX\ is in math mode and +working on an mlist; this formula has temporarily interrupted \TeX\ from +being in horizontal mode and building the hlist of a paragraph; and this +paragraph has temporarily interrupted \TeX\ from being in vertical mode +and building the vlist for the next page of a document. Similarly, when a +\.{\\vbox} occurs inside of an \.{\\hbox}, \TeX\ is temporarily +interrupted from working in restricted horizontal mode, and it enters +internal vertical mode. The ``semantic nest'' is a stack that +keeps track of what lists and modes are currently suspended. + +At each level of processing we are in one of six modes: + +\yskip\hang|vmode| stands for vertical mode (the page builder); + +\hang|hmode| stands for horizontal mode (the paragraph builder); + +\hang|mmode| stands for displayed formula mode; + +\hang|-vmode| stands for internal vertical mode (e.g., in a \.{\\vbox}); + +\hang|-hmode| stands for restricted horizontal mode (e.g., in an \.{\\hbox}); + +\hang|-mmode| stands for math formula mode (not displayed). + +\yskip\noindent The mode is temporarily set to zero while processing \.{\\write} +texts. + +Numeric values are assigned to |vmode|, |hmode|, and |mmode| so that +\TeX's ``big semantic switch'' can select the appropriate thing to +do by computing the value |abs(mode)+cur_cmd|, where |mode| is the current +mode and |cur_cmd| is the current command code. + +@d vmode 1 /*vertical mode*/ +@d hmode (vmode+max_command+1) /*horizontal mode*/ +@d mmode (hmode+max_command+1) /*math mode*/ + +@p static void print_mode(int @!m) /*prints the mode represented by |m|*/ +{@+if (m > 0) + switch (m/(max_command+1)) { + case 0: print("vertical");@+break; + case 1: print("horizontal");@+break; + case 2: print("display math"); + } +else if (m==0) print("no"); +else switch ((-m)/(max_command+1)) { + case 0: print("internal vertical");@+break; + case 1: print("restricted horizontal");@+break; + case 2: print("math"); + } +print(" mode"); +} + +@ The state of affairs at any semantic level can be represented by +five values: + +\yskip\hang|mode| is the number representing the semantic mode, as +just explained. + +\yskip\hang|head| is a |pointer| to a list head for the list being built; +|link(head)| therefore points to the first element of the list, or +to |null| if the list is empty. + +\yskip\hang|tail| is a |pointer| to the final node of the list being +built; thus, |tail==head| if and only if the list is empty. + +\yskip\hang|prev_graf| is the number of lines of the current paragraph that +have already been put into the present vertical list. + +\yskip\hang|aux| is an auxiliary |memory_word| that gives further information +that is needed to characterize the situation. + +\yskip\noindent +In vertical mode, |aux| is also known as |prev_depth|; it is the scaled +value representing the depth of the previous box, for use in baseline +calculations, or it is | <= -1000|pt if the next box on the vertical list is to +be exempt from baseline calculations. In horizontal mode, |aux| is also +known as |space_factor| and |clang|; it holds the current space factor used in +spacing calculations, and the current language used for hyphenation. +(The value of |clang| is undefined in restricted horizontal mode.) +In math mode, |aux| is also known as |incompleat_noad|; if +not |null|, it points to a record that represents the numerator of a +generalized fraction for which the denominator is currently being formed +in the current list. + +There is also a sixth quantity, |mode_line|, which correlates +the semantic nest with the user's input; |mode_line| contains the source +line number at which the current level of nesting was entered. The negative +of this line number is the |mode_line| at the level of the +user's output routine. + +A seventh quantity, |eTeX_aux|, is used by the extended features \eTeX. +In vertical modes it is known as |LR_save| and holds the LR stack when a +paragraph is interrupted by a displayed formula. In display math mode +it is known as |LR_box| and holds a pointer to a prototype box for the +display. In math mode it is known as |delim_ptr| and points to the most +recent |left_noad| or |middle_noad| of a |math_left_group|. + +In horizontal mode, the |prev_graf| field is used for initial language data. + +The semantic nest is an array called |nest| that holds the |mode|, |head|, +|tail|, |prev_graf|, |aux|, and |mode_line| values for all semantic levels +below the currently active one. Information about the currently active +level is kept in the global quantities |mode|, |head|, |tail|, |prev_graf|, +|aux|, and |mode_line|, which live in a \PASCAL\ record that is ready to +be pushed onto |nest| if necessary. + +@d ignore_depth -65536000 /*|prev_depth| value that is ignored*/ + +@<Types...@>= +typedef struct { int16_t @!mode_field;@+ + pointer @!head_field, @!tail_field; + pointer @!eTeX_aux_field; + int @!pg_field, @!ml_field;@+ + memory_word @!aux_field; + } list_state_record; + +@ @d mode cur_list.mode_field /*current mode*/ +@d head cur_list.head_field /*header node of current list*/ +@d tail cur_list.tail_field /*final node on current list*/ +@d eTeX_aux cur_list.eTeX_aux_field /*auxiliary data for \eTeX*/ +@d LR_save eTeX_aux /*LR stack when a paragraph is interrupted*/ +@d LR_box eTeX_aux /*prototype box for display*/ +@d delim_ptr eTeX_aux /*most recent left or right noad of a math left group*/ +@d prev_graf cur_list.pg_field /*number of paragraph lines accumulated*/ +@d aux cur_list.aux_field /*auxiliary data about the current list*/ +@d prev_depth aux.sc /*the name of |aux| in vertical mode*/ +@d space_factor aux.hh.lh /*part of |aux| in horizontal mode*/ +@d clang aux.hh.rh /*the other part of |aux| in horizontal mode*/ +@d incompleat_noad aux.i /*the name of |aux| in math mode*/ +@d mode_line cur_list.ml_field /*source file line number at beginning of list*/ + +@<Glob...@>= +static list_state_record @!nest[nest_size+1]; +static int @!nest_ptr; /*first unused location of |nest|*/ +static int @!max_nest_stack; /*maximum of |nest_ptr| when pushing*/ +static list_state_record @!cur_list; /*the ``top'' semantic state*/ +static int @!shown_mode; /*most recent mode shown by \.{\\tracingcommands}*/ + +@ Here is a common way to make the current list grow: + +@d tail_append(A) {@+link(tail)=A;tail=link(tail); + } + +@ We will see later that the vertical list at the bottom semantic level is split +into two parts; the ``current page'' runs from |page_head| to |page_tail|, +and the ``contribution list'' runs from |contrib_head| to |tail| of +semantic level zero. The idea is that contributions are first formed in +vertical mode, then ``contributed'' to the current page (during which time +the page-breaking decisions are made). For now, we don't need to know +any more details about the page-building process. + +@<Set init...@>= +nest_ptr=0;max_nest_stack=0; +mode=vmode;head=contrib_head;tail=contrib_head; +eTeX_aux=null; +prev_depth=ignore_depth;mode_line=0; +prev_graf=0;shown_mode=0; +@<Start a new current page@>; + +@ When \TeX's work on one level is interrupted, the state is saved by +calling |push_nest|. This routine changes |head| and |tail| so that +a new (empty) list is begun; it does not change |mode| or |aux|. + +@p static void push_nest(void) /*enter a new semantic level, save the old*/ +{@+if (nest_ptr > max_nest_stack) + {@+max_nest_stack=nest_ptr; + if (nest_ptr==nest_size) overflow("semantic nest size", nest_size); +@:TeX capacity exceeded semantic nest size}{\quad semantic nest size@> + } +nest[nest_ptr]=cur_list; /*stack the record*/ +incr(nest_ptr);head=get_avail();tail=head;prev_graf=0;mode_line=line; +eTeX_aux=null; +} + +@ Conversely, when \TeX\ is finished on the current level, the former +state is restored by calling |pop_nest|. This routine will never be +called at the lowest semantic level, nor will it be called unless |head| +is a node that should be returned to free memory. + +@p static void pop_nest(void) /*leave a semantic level, re-enter the old*/ +{@+free_avail(head);decr(nest_ptr);cur_list=nest[nest_ptr]; +} + +@ Here is a procedure that displays what \TeX\ is working on, at all levels. + +@p static void print_totals(void); +static void show_activities(void) +{@+int p; /*index into |nest|*/ +int @!m; /*mode*/ +memory_word @!a; /*auxiliary*/ +pointer @!q, @!r; /*for showing the current page*/ +int @!t; /*ditto*/ +nest[nest_ptr]=cur_list; /*put the top level into the array*/ +print_nl("");print_ln(); +for (p=nest_ptr; p>=0; p--) + {@+m=nest[p].mode_field;a=nest[p].aux_field; + print_nl("### ");print_mode(m); + print(" entered at line ");print_int(abs(nest[p].ml_field)); + if (m==hmode) if (nest[p].pg_field!=040600000) + {@+print(" (language");print_int(nest[p].pg_field%0200000); + print(":hyphenmin");print_int(nest[p].pg_field/020000000); + print_char(',');print_int((nest[p].pg_field/0200000)%0100); + print_char(')'); + } + if (nest[p].ml_field < 0) print(" (\\output routine)"); + if (p==0) + {@+@<Show the status of the current page@>; + if (link(contrib_head)!=null) + print_nl("### recent contributions:"); + } + show_box(link(nest[p].head_field)); + @<Show the auxiliary field, |a|@>; + } +} + +@ @<Show the auxiliary...@>= +switch (abs(m)/(max_command+1)) { +case 0: {@+print_nl("prevdepth "); + if (a.sc <= ignore_depth) print("ignored"); + else print_scaled(a.sc); + if (nest[p].pg_field!=0) + {@+print(", prevgraf "); + print_int(nest[p].pg_field);print(" line"); + if (nest[p].pg_field!=1) print_char('s'); + } + } @+break; +case 1: {@+print_nl("spacefactor ");print_int(a.hh.lh); + if (m > 0) @+if (a.hh.rh > 0) + {@+print(", current language ");print_int(a.hh.rh);@+ + } + } @+break; +case 2: if (a.i!=null) + {@+print("this will begin denominator of:");show_box(a.i);@+ + } +} /*there are no other cases*/ + +@* The table of equivalents. +Now that we have studied the data structures for \TeX's semantic routines, +we ought to consider the data structures used by its syntactic routines. In +other words, our next concern will be +the tables that \TeX\ looks at when it is scanning +what the user has written. + +The biggest and most important such table is called |eqtb|. It holds the +current ``equivalents'' of things; i.e., it explains what things mean +or what their current values are, for all quantities that are subject to +the nesting structure provided by \TeX's grouping mechanism. There are six +parts to |eqtb|: + +\yskip\hangg 1) |eqtb[active_base dotdot(hash_base-1)]| holds the current +equivalents of single-character control sequences. + +\yskip\hangg 2) |eqtb[hash_base dotdot(glue_base-1)]| holds the current +equivalents of multiletter control sequences. + +\yskip\hangg 3) |eqtb[glue_base dotdot(local_base-1)]| holds the current +equivalents of glue parameters like the current baselineskip. + +\yskip\hangg 4) |eqtb[local_base dotdot(int_base-1)]| holds the current +equivalents of local halfword quantities like the current box registers, +the current ``catcodes,'' the current font, and a pointer to the current +paragraph shape. + +\yskip\hangg 5) |eqtb[int_base dotdot(dimen_base-1)]| holds the current +equivalents of fullword integer parameters like the current hyphenation +penalty. + +\yskip\hangg 6) |eqtb[dimen_base dotdot eqtb_size]| holds the current equivalents +of fullword dimension parameters like the current hsize or amount of +hanging indentation. + +\yskip\noindent Note that, for example, the current amount of +baselineskip glue is determined by the setting of a particular location +in region~3 of |eqtb|, while the current meaning of the control sequence +`\.{\\baselineskip}' (which might have been changed by \.{\\def} or +\.{\\let}) appears in region~2. + +@ Each entry in |eqtb| is a |memory_word|. Most of these words are of type +|two_halves|, and subdivided into three fields: + +\yskip\hangg 1) The |eq_level| (a quarterword) is the level of grouping at +which this equivalent was defined. If the level is |level_zero|, the +equivalent has never been defined; |level_one| refers to the outer level +(outside of all groups), and this level is also used for global +definitions that never go away. Higher levels are for equivalents that +will disappear at the end of their group. @^global definitions@> + +\yskip\hangg 2) The |eq_type| (another quarterword) specifies what kind of +entry this is. There are many types, since each \TeX\ primitive like +\.{\\hbox}, \.{\\def}, etc., has its own special code. The list of +command codes above includes all possible settings of the |eq_type| field. + +\yskip\hangg 3) The |equiv| (a halfword) is the current equivalent value. +This may be a font number, a pointer into |mem|, or a variety of other +things. + +@d eq_level_field(A) A.hh.b1 +@d eq_type_field(A) A.hh.b0 +@d equiv_field(A) A.hh.rh +@d eq_level(A) eq_level_field(eqtb[A]) /*level of definition*/ +@d eq_type(A) eq_type_field(eqtb[A]) /*command code for equivalent*/ +@d equiv(A) equiv_field(eqtb[A]) /*equivalent value*/ +@d level_zero min_quarterword /*level for undefined quantities*/ +@d level_one (level_zero+1) /*outermost level for defined quantities*/ + +@ Many locations in |eqtb| have symbolic names. The purpose of the next +paragraphs is to define these names, and to set up the initial values of the +equivalents. + +In the first region we have 256 equivalents for ``active characters'' that +act as control sequences, followed by 256 equivalents for single-character +control sequences. + +Then comes region~2, which corresponds to the hash table that we will +define later. The maximum address in this region is used for a dummy +control sequence that is perpetually undefined. There also are several +locations for control sequences that are perpetually defined +(since they are used in error recovery). + +@d active_base 1 /*beginning of region 1, for active character equivalents*/ +@d single_base (active_base+256) /*equivalents of one-character control sequences*/ +@d null_cs (single_base+256) /*equivalent of \.{\\csname\\endcsname}*/ +@d hash_base (null_cs+1) /*beginning of region 2, for the hash table*/ +@d frozen_control_sequence (hash_base+hash_size) /*for error recovery*/ +@d frozen_protection frozen_control_sequence /*inaccessible but definable*/ +@d frozen_cr (frozen_control_sequence+1) /*permanent `\.{\\cr}'*/ +@d frozen_end_group (frozen_control_sequence+2) /*permanent `\.{\\endgroup}'*/ +@d frozen_right (frozen_control_sequence+3) /*permanent `\.{\\right}'*/ +@d frozen_fi (frozen_control_sequence+4) /*permanent `\.{\\fi}'*/ +@d frozen_end_template (frozen_control_sequence+5) /*permanent `\.{\\endtemplate}'*/ +@d frozen_endv (frozen_control_sequence+6) /*second permanent `\.{\\endtemplate}'*/ +@d frozen_relax (frozen_control_sequence+7) /*permanent `\.{\\relax}'*/ +@d end_write (frozen_control_sequence+8) /*permanent `\.{\\endwrite}'*/ +@d frozen_dont_expand (frozen_control_sequence+9) + /*permanent `\.{\\notexpanded:}'*/ +@d frozen_primitive (frozen_control_sequence+10) + /*permanent `\.{\\primitive:}'*/ +@d frozen_null_font (frozen_control_sequence+11) + /*permanent `\.{\\nullfont}'*/ +@d font_id_base (frozen_null_font-font_base) + /*begins table of 257 permanent font identifiers*/ +@d undefined_control_sequence (frozen_null_font+257) /*dummy location*/ +@d glue_base (undefined_control_sequence+1) /*beginning of region 3*/ + +@<Initialize table entries...@>= +eq_type(undefined_control_sequence)=undefined_cs; +equiv(undefined_control_sequence)=null; +eq_level(undefined_control_sequence)=level_zero; +for (k=active_base; k<=undefined_control_sequence-1; k++) + eqtb[k]=eqtb[undefined_control_sequence]; + +@ Here is a routine that displays the current meaning of an |eqtb| entry +in region 1 or~2. (Similar routines for the other regions will appear +below.) + +@<Show equivalent |n|, in region 1 or 2@>= +{@+sprint_cs(n);print_char('=');print_cmd_chr(eq_type(n), equiv(n)); +if (eq_type(n) >= call) + {@+print_char(':');show_token_list(link(equiv(n)), null, 32); + } +} + +@ Region 3 of |eqtb| contains the 256 \.{\\skip} registers, as well as the +glue parameters defined here. It is important that the ``muskip'' +parameters have larger numbers than the others. + +@d line_skip_code 0 /*interline glue if |baseline_skip| is infeasible*/ +@d baseline_skip_code 1 /*desired glue between baselines*/ +@d par_skip_code 2 /*extra glue just above a paragraph*/ +@d above_display_skip_code 3 /*extra glue just above displayed math*/ +@d below_display_skip_code 4 /*extra glue just below displayed math*/ +@d above_display_short_skip_code 5 + /*glue above displayed math following short lines*/ +@d below_display_short_skip_code 6 + /*glue below displayed math following short lines*/ +@d left_skip_code 7 /*glue at left of justified lines*/ +@d right_skip_code 8 /*glue at right of justified lines*/ +@d top_skip_code 9 /*glue at top of main pages*/ +@d split_top_skip_code 10 /*glue at top of split pages*/ +@d tab_skip_code 11 /*glue between aligned entries*/ +@d space_skip_code 12 /*glue between words (if not |zero_glue|)*/ +@d xspace_skip_code 13 /*glue after sentences (if not |zero_glue|)*/ +@d par_fill_skip_code 14 /*glue on last line of paragraph*/ +@d thin_mu_skip_code 15 /*thin space in math formula*/ +@d med_mu_skip_code 16 /*medium space in math formula*/ +@d thick_mu_skip_code 17 /*thick space in math formula*/ +@d glue_pars 18 /*total number of glue parameters*/ +@d skip_base (glue_base+glue_pars) /*table of 256 ``skip'' registers*/ +@d mu_skip_base (skip_base+256) /*table of 256 ``muskip'' registers*/ +@d local_base (mu_skip_base+256) /*beginning of region 4*/ +@# +@d skip(A) equiv(skip_base+A) /*|mem| location of glue specification*/ +@d mu_skip(A) equiv(mu_skip_base+A) /*|mem| location of math glue spec*/ +@d glue_par(A) equiv(glue_base+A) /*|mem| location of glue specification*/ +@d line_skip glue_par(line_skip_code) +@d baseline_skip glue_par(baseline_skip_code) +@d par_skip glue_par(par_skip_code) +@d above_display_skip glue_par(above_display_skip_code) +@d below_display_skip glue_par(below_display_skip_code) +@d above_display_short_skip glue_par(above_display_short_skip_code) +@d below_display_short_skip glue_par(below_display_short_skip_code) +@d left_skip glue_par(left_skip_code) +@d right_skip glue_par(right_skip_code) +@d top_skip glue_par(top_skip_code) +@d split_top_skip glue_par(split_top_skip_code) +@d tab_skip glue_par(tab_skip_code) +@d space_skip glue_par(space_skip_code) +@d xspace_skip glue_par(xspace_skip_code) +@d par_fill_skip glue_par(par_fill_skip_code) +@d thin_mu_skip glue_par(thin_mu_skip_code) +@d med_mu_skip glue_par(med_mu_skip_code) +@d thick_mu_skip glue_par(thick_mu_skip_code) + +@<Current |mem| equivalent of glue parameter number |n|@>=glue_par(n) + +@ Sometimes we need to convert \TeX's internal code numbers into symbolic +form. The |print_skip_param| routine gives the symbolic name of a glue +parameter. + +@<Declare the procedure called |print_skip_param|@>= +static void print_skip_param(int @!n) +{@+switch (n) { +case line_skip_code: print_esc("lineskip");@+break; +case baseline_skip_code: print_esc("baselineskip");@+break; +case par_skip_code: print_esc("parskip");@+break; +case above_display_skip_code: print_esc("abovedisplayskip");@+break; +case below_display_skip_code: print_esc("belowdisplayskip");@+break; +case above_display_short_skip_code: print_esc("abovedisplayshortskip");@+break; +case below_display_short_skip_code: print_esc("belowdisplayshortskip");@+break; +case left_skip_code: print_esc("leftskip");@+break; +case right_skip_code: print_esc("rightskip");@+break; +case top_skip_code: print_esc("topskip");@+break; +case split_top_skip_code: print_esc("splittopskip");@+break; +case tab_skip_code: print_esc("tabskip");@+break; +case space_skip_code: print_esc("spaceskip");@+break; +case xspace_skip_code: print_esc("xspaceskip");@+break; +case par_fill_skip_code: print_esc("parfillskip");@+break; +case thin_mu_skip_code: print_esc("thinmuskip");@+break; +case med_mu_skip_code: print_esc("medmuskip");@+break; +case thick_mu_skip_code: print_esc("thickmuskip");@+break; +default:print("[unknown glue parameter!]"); +} +} + +@ The symbolic names for glue parameters are put into \TeX's hash table +by using the routine called |primitive|, defined below. Let us enter them +now, so that we don't have to list all those parameter names anywhere else. + +@<Put each of \TeX's primitives into the hash table@>= +primitive("lineskip", assign_glue, glue_base+line_skip_code);@/ +@!@:line\_skip\_}{\.{\\lineskip} primitive@> +primitive("baselineskip", assign_glue, glue_base+baseline_skip_code);@/ +@!@:baseline\_skip\_}{\.{\\baselineskip} primitive@> +primitive("parskip", assign_glue, glue_base+par_skip_code);@/ +@!@:par\_skip\_}{\.{\\parskip} primitive@> +primitive("abovedisplayskip", assign_glue, glue_base+above_display_skip_code);@/ +@!@:above\_display\_skip\_}{\.{\\abovedisplayskip} primitive@> +primitive("belowdisplayskip", assign_glue, glue_base+below_display_skip_code);@/ +@!@:below\_display\_skip\_}{\.{\\belowdisplayskip} primitive@> +primitive("abovedisplayshortskip", + assign_glue, glue_base+above_display_short_skip_code);@/ +@!@:above\_display\_short\_skip\_}{\.{\\abovedisplayshortskip} primitive@> +primitive("belowdisplayshortskip", + assign_glue, glue_base+below_display_short_skip_code);@/ +@!@:below\_display\_short\_skip\_}{\.{\\belowdisplayshortskip} primitive@> +primitive("leftskip", assign_glue, glue_base+left_skip_code);@/ +@!@:left\_skip\_}{\.{\\leftskip} primitive@> +primitive("rightskip", assign_glue, glue_base+right_skip_code);@/ +@!@:right\_skip\_}{\.{\\rightskip} primitive@> +primitive("topskip", assign_glue, glue_base+top_skip_code);@/ +@!@:top\_skip\_}{\.{\\topskip} primitive@> +primitive("splittopskip", assign_glue, glue_base+split_top_skip_code);@/ +@!@:split\_top\_skip\_}{\.{\\splittopskip} primitive@> +primitive("tabskip", assign_glue, glue_base+tab_skip_code);@/ +@!@:tab\_skip\_}{\.{\\tabskip} primitive@> +primitive("spaceskip", assign_glue, glue_base+space_skip_code);@/ +@!@:space\_skip\_}{\.{\\spaceskip} primitive@> +primitive("xspaceskip", assign_glue, glue_base+xspace_skip_code);@/ +@!@:xspace\_skip\_}{\.{\\xspaceskip} primitive@> +primitive("parfillskip", assign_glue, glue_base+par_fill_skip_code);@/ +@!@:par\_fill\_skip\_}{\.{\\parfillskip} primitive@> +primitive("thinmuskip", assign_mu_glue, glue_base+thin_mu_skip_code);@/ +@!@:thin\_mu\_skip\_}{\.{\\thinmuskip} primitive@> +primitive("medmuskip", assign_mu_glue, glue_base+med_mu_skip_code);@/ +@!@:med\_mu\_skip\_}{\.{\\medmuskip} primitive@> +primitive("thickmuskip", assign_mu_glue, glue_base+thick_mu_skip_code);@/ +@!@:thick\_mu\_skip\_}{\.{\\thickmuskip} primitive@> + +@ @<Cases of |print_cmd_chr| for symbolic printing of primitives@>= +case assign_glue: case assign_mu_glue: if (chr_code < skip_base) + print_skip_param(chr_code-glue_base); + else if (chr_code < mu_skip_base) + {@+print_esc("skip");print_int(chr_code-skip_base); + } + else{@+print_esc("muskip");print_int(chr_code-mu_skip_base); + } @+break; + +@ All glue parameters and registers are initially `\.{0pt plus0pt minus0pt}'. + +@<Initialize table entries...@>= +equiv(glue_base)=zero_glue;eq_level(glue_base)=level_one; +eq_type(glue_base)=glue_ref; +for (k=glue_base+1; k<=local_base-1; k++) eqtb[k]=eqtb[glue_base]; +glue_ref_count(zero_glue)=glue_ref_count(zero_glue)+local_base-glue_base; + +@ @<Show equivalent |n|, in region 3@>= +if (n < skip_base) + {@+print_skip_param(n-glue_base);print_char('='); + if (n < glue_base+thin_mu_skip_code) print_spec(equiv(n),"pt"); + else print_spec(equiv(n),"mu"); + } +else if (n < mu_skip_base) + {@+print_esc("skip");print_int(n-skip_base);print_char('='); + print_spec(equiv(n),"pt"); + } +else{@+print_esc("muskip");print_int(n-mu_skip_base);print_char('='); + print_spec(equiv(n),"mu"); + } + +@ Region 4 of |eqtb| contains the local quantities defined here. The +bulk of this region is taken up by five tables that are indexed by eight-bit +characters; these tables are important to both the syntactic and semantic +portions of \TeX. There are also a bunch of special things like font and +token parameters, as well as the tables of \.{\\toks} and \.{\\box} +registers. + +@d par_shape_loc local_base /*specifies paragraph shape*/ +@d output_routine_loc (local_base+1) /*points to token list for \.{\\output}*/ +@d every_par_loc (local_base+2) /*points to token list for \.{\\everypar}*/ +@d every_math_loc (local_base+3) /*points to token list for \.{\\everymath}*/ +@d every_display_loc (local_base+4) /*points to token list for \.{\\everydisplay}*/ +@d every_hbox_loc (local_base+5) /*points to token list for \.{\\everyhbox}*/ +@d every_vbox_loc (local_base+6) /*points to token list for \.{\\everyvbox}*/ +@d every_job_loc (local_base+7) /*points to token list for \.{\\everyjob}*/ +@d every_cr_loc (local_base+8) /*points to token list for \.{\\everycr}*/ +@d err_help_loc (local_base+9) /*points to token list for \.{\\errhelp}*/ +@d tex_toks (local_base+10) /*end of \TeX's token list parameters*/ +@# +@d etex_toks_base pdf_toks /*base for \eTeX's token list parameters*/ +@d every_eof_loc etex_toks_base /*points to token list for \.{\\everyeof}*/ +@d etex_toks (etex_toks_base+1) /*end of \eTeX's token list parameters*/ +@# +@d toks_base etex_toks /*table of 256 token list registers*/ +@# +@d etex_pen_base (toks_base+256) /*start of table of \eTeX's penalties*/ +@d inter_line_penalties_loc etex_pen_base /*additional penalties between lines*/ +@d club_penalties_loc (etex_pen_base+1) /*penalties for creating club lines*/ +@d widow_penalties_loc (etex_pen_base+2) /*penalties for creating widow lines*/ +@d display_widow_penalties_loc (etex_pen_base+3) /*ditto, just before a display*/ +@d etex_pens (etex_pen_base+4) /*end of table of \eTeX's penalties*/ +@# +@d box_base etex_pens /*table of 256 box registers*/ +@d cur_font_loc (box_base+256) /*internal font number outside math mode*/ +@d math_font_base (cur_font_loc+1) /*table of 48 math font numbers*/ +@d cat_code_base (math_font_base+48) + /*table of 256 command codes (the ``catcodes'')*/ +@d lc_code_base (cat_code_base+256) /*table of 256 lowercase mappings*/ +@d uc_code_base (lc_code_base+256) /*table of 256 uppercase mappings*/ +@d sf_code_base (uc_code_base+256) /*table of 256 spacefactor mappings*/ +@d math_code_base (sf_code_base+256) /*table of 256 math mode mappings*/ +@d int_base (math_code_base+256) /*beginning of region 5*/ +@# +@d par_shape_ptr equiv(par_shape_loc) +@d output_routine equiv(output_routine_loc) +@d every_par equiv(every_par_loc) +@d every_math equiv(every_math_loc) +@d every_display equiv(every_display_loc) +@d every_hbox equiv(every_hbox_loc) +@d every_vbox equiv(every_vbox_loc) +@d every_job equiv(every_job_loc) +@d every_cr equiv(every_cr_loc) +@d err_help equiv(err_help_loc) +@d toks(X) equiv(toks_base+X) +@d box(A) equiv(box_base+A) +@d cur_font equiv(cur_font_loc) +@d fam_fnt(A) equiv(math_font_base+A) +@d cat_code(A) equiv(cat_code_base+A) +@d lc_code(A) equiv(lc_code_base+A) +@d uc_code(A) equiv(uc_code_base+A) +@d sf_code(A) equiv(sf_code_base+A) +@d math_code(A) equiv(math_code_base+A) + /*Note: |math_code(c)| is the true math code plus |min_halfword|*/ + +@<Put each...@>= +primitive("output", assign_toks, output_routine_loc); +@!@:output\_}{\.{\\output} primitive@> +primitive("everypar", assign_toks, every_par_loc); +@!@:every\_par\_}{\.{\\everypar} primitive@> +primitive("everymath", assign_toks, every_math_loc); +@!@:every\_math\_}{\.{\\everymath} primitive@> +primitive("everydisplay", assign_toks, every_display_loc); +@!@:every\_display\_}{\.{\\everydisplay} primitive@> +primitive("everyhbox", assign_toks, every_hbox_loc); +@!@:every\_hbox\_}{\.{\\everyhbox} primitive@> +primitive("everyvbox", assign_toks, every_vbox_loc); +@!@:every\_vbox\_}{\.{\\everyvbox} primitive@> +primitive("everyjob", assign_toks, every_job_loc); +@!@:every\_job\_}{\.{\\everyjob} primitive@> +primitive("everycr", assign_toks, every_cr_loc); +@!@:every\_cr\_}{\.{\\everycr} primitive@> +primitive("errhelp", assign_toks, err_help_loc); +@!@:err\_help\_}{\.{\\errhelp} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case assign_toks: if (chr_code >= toks_base) + {@+print_esc("toks");print_int(chr_code-toks_base); + } +else switch (chr_code) { + case output_routine_loc: print_esc("output");@+break; + case every_par_loc: print_esc("everypar");@+break; + case every_math_loc: print_esc("everymath");@+break; + case every_display_loc: print_esc("everydisplay");@+break; + case every_hbox_loc: print_esc("everyhbox");@+break; + case every_vbox_loc: print_esc("everyvbox");@+break; + case every_job_loc: print_esc("everyjob");@+break; + case every_cr_loc: print_esc("everycr");@+break; + @/@<Cases of |assign_toks| for |print_cmd_chr|@>@/ + default:print_esc("errhelp"); + } @+break; + +@ We initialize most things to null or undefined values. An undefined font +is represented by the internal code |font_base|. + +However, the character code tables are given initial values based on the +conventional interpretation of ASCII code. These initial values should +not be changed when \TeX\ is adapted for use with non-English languages; +all changes to the initialization conventions should be made in format +packages, not in \TeX\ itself, so that global interchange of formats is +possible. + +@d null_font font_base +@d var_code 070000 /*math code meaning ``use the current family''*/ + +@<Initialize table entries...@>= +par_shape_ptr=null;eq_type(par_shape_loc)=shape_ref; +eq_level(par_shape_loc)=level_one;@/ +for (k=etex_pen_base; k<=etex_pens-1; k++) + eqtb[k]=eqtb[par_shape_loc]; +for (k=output_routine_loc; k<=toks_base+255; k++) + eqtb[k]=eqtb[undefined_control_sequence]; +box(0)=null;eq_type(box_base)=box_ref;eq_level(box_base)=level_one; +for (k=box_base+1; k<=box_base+255; k++) eqtb[k]=eqtb[box_base]; +cur_font=null_font;eq_type(cur_font_loc)=data; +eq_level(cur_font_loc)=level_one;@/ +for (k=math_font_base; k<=math_font_base+47; k++) eqtb[k]=eqtb[cur_font_loc]; +equiv(cat_code_base)=0;eq_type(cat_code_base)=data; +eq_level(cat_code_base)=level_one;@/ +for (k=cat_code_base+1; k<=int_base-1; k++) eqtb[k]=eqtb[cat_code_base]; +for (k=0; k<=255; k++) + {@+cat_code(k)=other_char;math_code(k)=hi(k);sf_code(k)=1000; + } +cat_code(carriage_return)=car_ret;cat_code(' ')=spacer; +cat_code('\\')=escape;cat_code('%')=comment; +cat_code(invalid_code)=invalid_char;cat_code(null_code)=ignore; +for (k='0'; k<='9'; k++) math_code(k)=hi(k+var_code); +for (k='A'; k<='Z'; k++) + {@+cat_code(k)=letter;cat_code(k+'a'-'A')=letter;@/ + math_code(k)=hi(k+var_code+0x100); + math_code(k+'a'-'A')=hi(k+'a'-'A'+var_code+0x100);@/ + lc_code(k)=k+'a'-'A';lc_code(k+'a'-'A')=k+'a'-'A';@/ + uc_code(k)=k;uc_code(k+'a'-'A')=k;@/ + sf_code(k)=999; + } + +@ @<Show equivalent |n|, in region 4@>= +if ((n==par_shape_loc)||((n >= etex_pen_base)&&(n < etex_pens))) + {@+print_cmd_chr(set_shape, n);print_char('='); + if (equiv(n)==null) print_char('0'); + else if (n > par_shape_loc) + {@+print_int(penalty(equiv(n)));print_char(' '); + print_int(penalty(equiv(n)+1)); + if (penalty(equiv(n)) > 1) print_esc("ETC."); + } + else print_int(info(par_shape_ptr)); + } +else if (n < toks_base) + {@+print_cmd_chr(assign_toks, n);print_char('='); + if (equiv(n)!=null) show_token_list(link(equiv(n)), null, 32); + } +else if (n < box_base) + {@+print_esc("toks");print_int(n-toks_base);print_char('='); + if (equiv(n)!=null) show_token_list(link(equiv(n)), null, 32); + } +else if (n < cur_font_loc) + {@+print_esc("box");print_int(n-box_base);print_char('='); + if (equiv(n)==null) print("void"); + else{@+depth_threshold=0;breadth_max=1;show_node_list(equiv(n)); + } + } +else if (n < cat_code_base) @<Show the font identifier in |eqtb[n]|@>@; +else@<Show the halfword code in |eqtb[n]|@>@; + +@ @<Show the font identifier in |eqtb[n]|@>= +{@+if (n==cur_font_loc) print("current font"); +else if (n < math_font_base+16) + {@+print_esc("textfont");print_int(n-math_font_base); + } +else if (n < math_font_base+32) + {@+print_esc("scriptfont");print_int(n-math_font_base-16); + } +else{@+print_esc("scriptscriptfont");print_int(n-math_font_base-32); + } +print_char('=');@/ +printn_esc(hash[font_id_base+equiv(n)].rh); + /*that's |font_id_text(equiv(n))|*/ +} + +@ @<Show the halfword code in |eqtb[n]|@>= +if (n < math_code_base) + {@+if (n < lc_code_base) + {@+print_esc("catcode");print_int(n-cat_code_base); + } + else if (n < uc_code_base) + {@+print_esc("lccode");print_int(n-lc_code_base); + } + else if (n < sf_code_base) + {@+print_esc("uccode");print_int(n-uc_code_base); + } + else{@+print_esc("sfcode");print_int(n-sf_code_base); + } + print_char('=');print_int(equiv(n)); + } +else{@+print_esc("mathcode");print_int(n-math_code_base); + print_char('=');print_int(ho(equiv(n))); + } + +@ Region 5 of |eqtb| contains the integer parameters and registers defined +here, as well as the |del_code| table. The latter table differs from the +|cat_code dotdot math_code| tables that precede it, since delimiter codes are +fullword integers while the other kinds of codes occupy at most a +halfword. This is what makes region~5 different from region~4. We will +store the |eq_level| information in an auxiliary array of quarterwords +that will be defined later. + +@d pretolerance_code 0 /*badness tolerance before hyphenation*/ +@d tolerance_code 1 /*badness tolerance after hyphenation*/ +@d line_penalty_code 2 /*added to the badness of every line*/ +@d hyphen_penalty_code 3 /*penalty for break after discretionary hyphen*/ +@d ex_hyphen_penalty_code 4 /*penalty for break after explicit hyphen*/ +@d club_penalty_code 5 /*penalty for creating a club line*/ +@d widow_penalty_code 6 /*penalty for creating a widow line*/ +@d display_widow_penalty_code 7 /*ditto, just before a display*/ +@d broken_penalty_code 8 /*penalty for breaking a page at a broken line*/ +@d bin_op_penalty_code 9 /*penalty for breaking after a binary operation*/ +@d rel_penalty_code 10 /*penalty for breaking after a relation*/ +@d pre_display_penalty_code 11 + /*penalty for breaking just before a displayed formula*/ +@d post_display_penalty_code 12 + /*penalty for breaking just after a displayed formula*/ +@d inter_line_penalty_code 13 /*additional penalty between lines*/ +@d double_hyphen_demerits_code 14 /*demerits for double hyphen break*/ +@d final_hyphen_demerits_code 15 /*demerits for final hyphen break*/ +@d adj_demerits_code 16 /*demerits for adjacent incompatible lines*/ +@d mag_code 17 /*magnification ratio*/ +@d delimiter_factor_code 18 /*ratio for variable-size delimiters*/ +@d looseness_code 19 /*change in number of lines for a paragraph*/ +@d time_code 20 /*current time of day*/ +@d day_code 21 /*current day of the month*/ +@d month_code 22 /*current month of the year*/ +@d year_code 23 /*current year of our Lord*/ +@d show_box_breadth_code 24 /*nodes per level in |show_box|*/ +@d show_box_depth_code 25 /*maximum level in |show_box|*/ +@d hbadness_code 26 /*hboxes exceeding this badness will be shown by |hpack|*/ +@d vbadness_code 27 /*vboxes exceeding this badness will be shown by |vpack|*/ +@d pausing_code 28 /*pause after each line is read from a file*/ +@d tracing_online_code 29 /*show diagnostic output on terminal*/ +@d tracing_macros_code 30 /*show macros as they are being expanded*/ +@d tracing_stats_code 31 /*show memory usage if \TeX\ knows it*/ +@d tracing_paragraphs_code 32 /*show line-break calculations*/ +@d tracing_pages_code 33 /*show page-break calculations*/ +@d tracing_output_code 34 /*show boxes when they are shipped out*/ +@d tracing_lost_chars_code 35 /*show characters that aren't in the font*/ +@d tracing_commands_code 36 /*show command codes at |big_switch|*/ +@d tracing_restores_code 37 /*show equivalents when they are restored*/ +@d uc_hyph_code 38 /*hyphenate words beginning with a capital letter*/ +@d output_penalty_code 39 /*penalty found at current page break*/ +@d max_dead_cycles_code 40 /*bound on consecutive dead cycles of output*/ +@d hang_after_code 41 /*hanging indentation changes after this many lines*/ +@d floating_penalty_code 42 /*penalty for insertions held over after a split*/ +@d global_defs_code 43 /*override \.{\\global} specifications*/ +@d cur_fam_code 44 /*current family*/ +@d escape_char_code 45 /*escape character for token output*/ +@d default_hyphen_char_code 46 /*value of \.{\\hyphenchar} when a font is loaded*/ +@d default_skew_char_code 47 /*value of \.{\\skewchar} when a font is loaded*/ +@d end_line_char_code 48 /*character placed at the right end of the buffer*/ +@d new_line_char_code 49 /*character that prints as |print_ln|*/ +@d language_code 50 /*current hyphenation table*/ +@d left_hyphen_min_code 51 /*minimum left hyphenation fragment size*/ +@d right_hyphen_min_code 52 /*minimum right hyphenation fragment size*/ +@d holding_inserts_code 53 /*do not remove insertion nodes from \.{\\box255}*/ +@d error_context_lines_code 54 /*maximum intermediate line pairs shown*/ +@d tex_int_pars 55 /*total number of \TeX's integer parameters*/ +@# +@d etex_int_base pdf_int_pars /*base for \eTeX's integer parameters*/ +@d tracing_assigns_code etex_int_base /*show assignments*/ +@d tracing_groups_code (etex_int_base+1) /*show save/restore groups*/ +@d tracing_ifs_code (etex_int_base+2) /*show conditionals*/ +@d tracing_scan_tokens_code (etex_int_base+3) /*show pseudo file open and close*/ +@d tracing_nesting_code (etex_int_base+4) /*show incomplete groups and ifs within files*/ +@d saving_vdiscards_code (etex_int_base+5) /*save items discarded from vlists*/ +@d saving_hyph_codes_code (etex_int_base+6) /*save hyphenation codes for languages*/ +@d expand_depth_code (etex_int_base+7) /*maximum depth for expansion---\eTeX*/ +@d eTeX_state_code (etex_int_base+8) /*\eTeX\ state variables*/ +@d etex_int_pars (eTeX_state_code+eTeX_states) /*total number of \eTeX's integer parameters*/ +@# +@d int_pars etex_int_pars /*total number of integer parameters*/ +@d count_base (int_base+int_pars) /*256 user \.{\\count} registers*/ +@d del_code_base (count_base+256) /*256 delimiter code mappings*/ +@d dimen_base (del_code_base+256) /*beginning of region 6*/ +@# +@d del_code(A) eqtb[del_code_base+A].i +@d count(A) eqtb[count_base+A].i +@d int_par(A) eqtb[int_base+A].i /*an integer parameter*/ +@d pretolerance int_par(pretolerance_code) +@d tolerance int_par(tolerance_code) +@d line_penalty int_par(line_penalty_code) +@d hyphen_penalty int_par(hyphen_penalty_code) +@d ex_hyphen_penalty int_par(ex_hyphen_penalty_code) +@d club_penalty int_par(club_penalty_code) +@d widow_penalty int_par(widow_penalty_code) +@d display_widow_penalty int_par(display_widow_penalty_code) +@d broken_penalty int_par(broken_penalty_code) +@d bin_op_penalty int_par(bin_op_penalty_code) +@d rel_penalty int_par(rel_penalty_code) +@d pre_display_penalty int_par(pre_display_penalty_code) +@d post_display_penalty int_par(post_display_penalty_code) +@d inter_line_penalty int_par(inter_line_penalty_code) +@d double_hyphen_demerits int_par(double_hyphen_demerits_code) +@d final_hyphen_demerits int_par(final_hyphen_demerits_code) +@d adj_demerits int_par(adj_demerits_code) +@d mag int_par(mag_code) +@d delimiter_factor int_par(delimiter_factor_code) +@d looseness int_par(looseness_code) +@d time int_par(time_code) +@d day int_par(day_code) +@d month int_par(month_code) +@d year int_par(year_code) +@d show_box_breadth int_par(show_box_breadth_code) +@d show_box_depth int_par(show_box_depth_code) +@d hbadness int_par(hbadness_code) +@d vbadness int_par(vbadness_code) +@d pausing int_par(pausing_code) +@d tracing_online int_par(tracing_online_code) +@d tracing_macros int_par(tracing_macros_code) +@d tracing_stats int_par(tracing_stats_code) +@d tracing_paragraphs int_par(tracing_paragraphs_code) +@d tracing_pages int_par(tracing_pages_code) +@d tracing_output int_par(tracing_output_code) +@d tracing_lost_chars int_par(tracing_lost_chars_code) +@d tracing_commands int_par(tracing_commands_code) +@d tracing_restores int_par(tracing_restores_code) +@d uc_hyph int_par(uc_hyph_code) +@d output_penalty int_par(output_penalty_code) +@d max_dead_cycles int_par(max_dead_cycles_code) +@d hang_after int_par(hang_after_code) +@d floating_penalty int_par(floating_penalty_code) +@d global_defs int_par(global_defs_code) +@d cur_fam int_par(cur_fam_code) +@d escape_char int_par(escape_char_code) +@d default_hyphen_char int_par(default_hyphen_char_code) +@d default_skew_char int_par(default_skew_char_code) +@d end_line_char int_par(end_line_char_code) +@d new_line_char int_par(new_line_char_code) +@d language int_par(language_code) +@d left_hyphen_min int_par(left_hyphen_min_code) +@d right_hyphen_min int_par(right_hyphen_min_code) +@d holding_inserts int_par(holding_inserts_code) +@d error_context_lines int_par(error_context_lines_code) +@# +@d tracing_assigns int_par(tracing_assigns_code) +@d tracing_groups int_par(tracing_groups_code) +@d tracing_ifs int_par(tracing_ifs_code) +@d tracing_scan_tokens int_par(tracing_scan_tokens_code) +@d tracing_nesting int_par(tracing_nesting_code) +@d saving_vdiscards int_par(saving_vdiscards_code) +@d saving_hyph_codes int_par(saving_hyph_codes_code) +@d expand_depth int_par(expand_depth_code) + +@<Assign the values |depth_threshold:=show_box_depth|...@>= +depth_threshold=show_box_depth; +breadth_max=show_box_breadth + +@ We can print the symbolic name of an integer parameter as follows. + +@p static void print_param(int @!n) +{@+switch (n) { +case pretolerance_code: print_esc("pretolerance");@+break; +case tolerance_code: print_esc("tolerance");@+break; +case line_penalty_code: print_esc("linepenalty");@+break; +case hyphen_penalty_code: print_esc("hyphenpenalty");@+break; +case ex_hyphen_penalty_code: print_esc("exhyphenpenalty");@+break; +case club_penalty_code: print_esc("clubpenalty");@+break; +case widow_penalty_code: print_esc("widowpenalty");@+break; +case display_widow_penalty_code: print_esc("displaywidowpenalty");@+break; +case broken_penalty_code: print_esc("brokenpenalty");@+break; +case bin_op_penalty_code: print_esc("binoppenalty");@+break; +case rel_penalty_code: print_esc("relpenalty");@+break; +case pre_display_penalty_code: print_esc("predisplaypenalty");@+break; +case post_display_penalty_code: print_esc("postdisplaypenalty");@+break; +case inter_line_penalty_code: print_esc("interlinepenalty");@+break; +case double_hyphen_demerits_code: print_esc("doublehyphendemerits");@+break; +case final_hyphen_demerits_code: print_esc("finalhyphendemerits");@+break; +case adj_demerits_code: print_esc("adjdemerits");@+break; +case mag_code: print_esc("mag");@+break; +case delimiter_factor_code: print_esc("delimiterfactor");@+break; +case looseness_code: print_esc("looseness");@+break; +case time_code: print_esc("time");@+break; +case day_code: print_esc("day");@+break; +case month_code: print_esc("month");@+break; +case year_code: print_esc("year");@+break; +case show_box_breadth_code: print_esc("showboxbreadth");@+break; +case show_box_depth_code: print_esc("showboxdepth");@+break; +case hbadness_code: print_esc("hbadness");@+break; +case vbadness_code: print_esc("vbadness");@+break; +case pausing_code: print_esc("pausing");@+break; +case tracing_online_code: print_esc("tracingonline");@+break; +case tracing_macros_code: print_esc("tracingmacros");@+break; +case tracing_stats_code: print_esc("tracingstats");@+break; +case tracing_paragraphs_code: print_esc("tracingparagraphs");@+break; +case tracing_pages_code: print_esc("tracingpages");@+break; +case tracing_output_code: print_esc("tracingoutput");@+break; +case tracing_lost_chars_code: print_esc("tracinglostchars");@+break; +case tracing_commands_code: print_esc("tracingcommands");@+break; +case tracing_restores_code: print_esc("tracingrestores");@+break; +case uc_hyph_code: print_esc("uchyph");@+break; +case output_penalty_code: print_esc("outputpenalty");@+break; +case max_dead_cycles_code: print_esc("maxdeadcycles");@+break; +case hang_after_code: print_esc("hangafter");@+break; +case floating_penalty_code: print_esc("floatingpenalty");@+break; +case global_defs_code: print_esc("globaldefs");@+break; +case cur_fam_code: print_esc("fam");@+break; +case escape_char_code: print_esc("escapechar");@+break; +case default_hyphen_char_code: print_esc("defaulthyphenchar");@+break; +case default_skew_char_code: print_esc("defaultskewchar");@+break; +case end_line_char_code: print_esc("endlinechar");@+break; +case new_line_char_code: print_esc("newlinechar");@+break; +case language_code: print_esc("language");@+break; +case left_hyphen_min_code: print_esc("lefthyphenmin");@+break; +case right_hyphen_min_code: print_esc("righthyphenmin");@+break; +case holding_inserts_code: print_esc("holdinginserts");@+break; +case error_context_lines_code: print_esc("errorcontextlines");@+break; +@/@<Cases for |print_param|@>@/ +default:print("[unknown integer parameter!]"); +} +} + +@ The integer parameter names must be entered into the hash table. + +@<Put each...@>= +primitive("pretolerance", assign_int, int_base+pretolerance_code);@/ +@!@:pretolerance\_}{\.{\\pretolerance} primitive@> +primitive("tolerance", assign_int, int_base+tolerance_code);@/ +@!@:tolerance\_}{\.{\\tolerance} primitive@> +primitive("linepenalty", assign_int, int_base+line_penalty_code);@/ +@!@:line\_penalty\_}{\.{\\linepenalty} primitive@> +primitive("hyphenpenalty", assign_int, int_base+hyphen_penalty_code);@/ +@!@:hyphen\_penalty\_}{\.{\\hyphenpenalty} primitive@> +primitive("exhyphenpenalty", assign_int, int_base+ex_hyphen_penalty_code);@/ +@!@:ex\_hyphen\_penalty\_}{\.{\\exhyphenpenalty} primitive@> +primitive("clubpenalty", assign_int, int_base+club_penalty_code);@/ +@!@:club\_penalty\_}{\.{\\clubpenalty} primitive@> +primitive("widowpenalty", assign_int, int_base+widow_penalty_code);@/ +@!@:widow\_penalty\_}{\.{\\widowpenalty} primitive@> +primitive("displaywidowpenalty", + assign_int, int_base+display_widow_penalty_code);@/ +@!@:display\_widow\_penalty\_}{\.{\\displaywidowpenalty} primitive@> +primitive("brokenpenalty", assign_int, int_base+broken_penalty_code);@/ +@!@:broken\_penalty\_}{\.{\\brokenpenalty} primitive@> +primitive("binoppenalty", assign_int, int_base+bin_op_penalty_code);@/ +@!@:bin\_op\_penalty\_}{\.{\\binoppenalty} primitive@> +primitive("relpenalty", assign_int, int_base+rel_penalty_code);@/ +@!@:rel\_penalty\_}{\.{\\relpenalty} primitive@> +primitive("predisplaypenalty", assign_int, int_base+pre_display_penalty_code);@/ +@!@:pre\_display\_penalty\_}{\.{\\predisplaypenalty} primitive@> +primitive("postdisplaypenalty", assign_int, int_base+post_display_penalty_code);@/ +@!@:post\_display\_penalty\_}{\.{\\postdisplaypenalty} primitive@> +primitive("interlinepenalty", assign_int, int_base+inter_line_penalty_code);@/ +@!@:inter\_line\_penalty\_}{\.{\\interlinepenalty} primitive@> +primitive("doublehyphendemerits", + assign_int, int_base+double_hyphen_demerits_code);@/ +@!@:double\_hyphen\_demerits\_}{\.{\\doublehyphendemerits} primitive@> +primitive("finalhyphendemerits", + assign_int, int_base+final_hyphen_demerits_code);@/ +@!@:final\_hyphen\_demerits\_}{\.{\\finalhyphendemerits} primitive@> +primitive("adjdemerits", assign_int, int_base+adj_demerits_code);@/ +@!@:adj\_demerits\_}{\.{\\adjdemerits} primitive@> +primitive("mag", assign_int, int_base+mag_code);@/ +@!@:mag\_}{\.{\\mag} primitive@> +primitive("delimiterfactor", assign_int, int_base+delimiter_factor_code);@/ +@!@:delimiter\_factor\_}{\.{\\delimiterfactor} primitive@> +primitive("looseness", assign_int, int_base+looseness_code);@/ +@!@:looseness\_}{\.{\\looseness} primitive@> +primitive("time", assign_int, int_base+time_code);@/ +@!@:time\_}{\.{\\time} primitive@> +primitive("day", assign_int, int_base+day_code);@/ +@!@:day\_}{\.{\\day} primitive@> +primitive("month", assign_int, int_base+month_code);@/ +@!@:month\_}{\.{\\month} primitive@> +primitive("year", assign_int, int_base+year_code);@/ +@!@:year\_}{\.{\\year} primitive@> +primitive("showboxbreadth", assign_int, int_base+show_box_breadth_code);@/ +@!@:show\_box\_breadth\_}{\.{\\showboxbreadth} primitive@> +primitive("showboxdepth", assign_int, int_base+show_box_depth_code);@/ +@!@:show\_box\_depth\_}{\.{\\showboxdepth} primitive@> +primitive("hbadness", assign_int, int_base+hbadness_code);@/ +@!@:hbadness\_}{\.{\\hbadness} primitive@> +primitive("vbadness", assign_int, int_base+vbadness_code);@/ +@!@:vbadness\_}{\.{\\vbadness} primitive@> +primitive("pausing", assign_int, int_base+pausing_code);@/ +@!@:pausing\_}{\.{\\pausing} primitive@> +primitive("tracingonline", assign_int, int_base+tracing_online_code);@/ +@!@:tracing\_online\_}{\.{\\tracingonline} primitive@> +primitive("tracingmacros", assign_int, int_base+tracing_macros_code);@/ +@!@:tracing\_macros\_}{\.{\\tracingmacros} primitive@> +primitive("tracingstats", assign_int, int_base+tracing_stats_code);@/ +@!@:tracing\_stats\_}{\.{\\tracingstats} primitive@> +primitive("tracingparagraphs", assign_int, int_base+tracing_paragraphs_code);@/ +@!@:tracing\_paragraphs\_}{\.{\\tracingparagraphs} primitive@> +primitive("tracingpages", assign_int, int_base+tracing_pages_code);@/ +@!@:tracing\_pages\_}{\.{\\tracingpages} primitive@> +primitive("tracingoutput", assign_int, int_base+tracing_output_code);@/ +@!@:tracing\_output\_}{\.{\\tracingoutput} primitive@> +primitive("tracinglostchars", assign_int, int_base+tracing_lost_chars_code);@/ +@!@:tracing\_lost\_chars\_}{\.{\\tracinglostchars} primitive@> +primitive("tracingcommands", assign_int, int_base+tracing_commands_code);@/ +@!@:tracing\_commands\_}{\.{\\tracingcommands} primitive@> +primitive("tracingrestores", assign_int, int_base+tracing_restores_code);@/ +@!@:tracing\_restores\_}{\.{\\tracingrestores} primitive@> +primitive("uchyph", assign_int, int_base+uc_hyph_code);@/ +@!@:uc\_hyph\_}{\.{\\uchyph} primitive@> +primitive("outputpenalty", assign_int, int_base+output_penalty_code);@/ +@!@:output\_penalty\_}{\.{\\outputpenalty} primitive@> +primitive("maxdeadcycles", assign_int, int_base+max_dead_cycles_code);@/ +@!@:max\_dead\_cycles\_}{\.{\\maxdeadcycles} primitive@> +primitive("hangafter", assign_int, int_base+hang_after_code);@/ +@!@:hang\_after\_}{\.{\\hangafter} primitive@> +primitive("floatingpenalty", assign_int, int_base+floating_penalty_code);@/ +@!@:floating\_penalty\_}{\.{\\floatingpenalty} primitive@> +primitive("globaldefs", assign_int, int_base+global_defs_code);@/ +@!@:global\_defs\_}{\.{\\globaldefs} primitive@> +primitive("fam", assign_int, int_base+cur_fam_code);@/ +@!@:fam\_}{\.{\\fam} primitive@> +primitive("escapechar", assign_int, int_base+escape_char_code);@/ +@!@:escape\_char\_}{\.{\\escapechar} primitive@> +primitive("defaulthyphenchar", assign_int, int_base+default_hyphen_char_code);@/ +@!@:default\_hyphen\_char\_}{\.{\\defaulthyphenchar} primitive@> +primitive("defaultskewchar", assign_int, int_base+default_skew_char_code);@/ +@!@:default\_skew\_char\_}{\.{\\defaultskewchar} primitive@> +primitive("endlinechar", assign_int, int_base+end_line_char_code);@/ +@!@:end\_line\_char\_}{\.{\\endlinechar} primitive@> +primitive("newlinechar", assign_int, int_base+new_line_char_code);@/ +@!@:new\_line\_char\_}{\.{\\newlinechar} primitive@> +primitive("language", assign_int, int_base+language_code);@/ +@!@:language\_}{\.{\\language} primitive@> +primitive("lefthyphenmin", assign_int, int_base+left_hyphen_min_code);@/ +@!@:left\_hyphen\_min\_}{\.{\\lefthyphenmin} primitive@> +primitive("righthyphenmin", assign_int, int_base+right_hyphen_min_code);@/ +@!@:right\_hyphen\_min\_}{\.{\\righthyphenmin} primitive@> +primitive("holdinginserts", assign_int, int_base+holding_inserts_code);@/ +@!@:holding\_inserts\_}{\.{\\holdinginserts} primitive@> +primitive("errorcontextlines", assign_int, int_base+error_context_lines_code);@/ +@!@:error\_context\_lines\_}{\.{\\errorcontextlines} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case assign_int: if (chr_code < count_base) print_param(chr_code-int_base); + else{@+print_esc("count");print_int(chr_code-count_base); + } @+break; + +@ The integer parameters should really be initialized by a macro package; +the following initialization does the minimum to keep \TeX\ from +complete failure. +@^null delimiter@> + +@<Initialize table entries...@>= +for (k=int_base; k<=del_code_base-1; k++) eqtb[k].i=0; +mag=1000;tolerance=10000;hang_after=1;max_dead_cycles=25; +escape_char='\\';end_line_char=carriage_return; +for (k=0; k<=255; k++) del_code(k)=-1; +del_code('.')=0; /*this null delimiter is used in error recovery*/ + +@ The following procedure, which is called just before \TeX\ initializes its +input and output, establishes the initial values of the date and time. +This does include too, for system integrators, the creation date and +the reference moment for the timer---\Prote\ extensions. If the system +supports environment variables, if |FORCE_SOURCE_DATE| is set to $1$ and +|SOURCE_DATE_EPOCH| is set, the date related values: year, month, day +and time, including creation date, will be taken relative from the value +defined by |SOURCE_DATE_EPOCH|. +@^creation date@> +@^reference time@> +@^system dependencies@> +\TeX\ Live calls |tl_now| to obtain the current time as a |tm| structure. +@p static void fix_date_and_time(void) +{@+ struct tm *t=tl_now(); + time=sys_time= t->tm_hour*60+t->tm_min;/*minutes since midnight*/ + day=sys_day= t->tm_mday;/*day of the month*/ + month=sys_month=t->tm_mon+1;/*month of the year*/ + year=sys_year=t->tm_year+1900;/*Anno Domini*/ +} + +@ @<Show equivalent |n|, in region 5@>= +{@+if (n < count_base) print_param(n-int_base); +else if (n < del_code_base) + {@+print_esc("count");print_int(n-count_base); + } +else{@+print_esc("delcode");print_int(n-del_code_base); + } +print_char('=');print_int(eqtb[n].i); +} + +@ @<Set variable |c| to the current escape character@>=c=escape_char + +@ @<Character |s| is the current new-line character@>=s==new_line_char + +@ \TeX\ is occasionally supposed to print diagnostic information that +goes only into the transcript file, unless |tracing_online| is positive. +Here are two routines that adjust the destination of print commands: + +@p static void begin_diagnostic(void) /*prepare to do some tracing*/ +{@+old_setting=selector; +if ((tracing_online <= 0)&&(selector==term_and_log)) + {@+decr(selector); + if (history==spotless) history=warning_issued; + } +} +@# +static void end_diagnostic(bool @!blank_line) + /*restore proper conditions after tracing*/ +{@+print_nl(""); +if (blank_line) print_ln(); +selector=old_setting; +} + +@ Of course we had better declare a few more global variables, if the previous +routines are going to work. + +@<Glob...@>= +static int @!old_setting; +static int @!sys_time, @!sys_day, @!sys_month, @!sys_year; + /*date and time supplied by external system*/ + +@ The final region of |eqtb| contains the dimension parameters defined +here, and the 256 \.{\\dimen} registers. + +@d par_indent_code 0 /*indentation of paragraphs*/ +@d math_surround_code 1 /*space around math in text*/ +@d line_skip_limit_code 2 /*threshold for |line_skip| instead of |baseline_skip|*/ +@d hsize_code 3 /*line width in horizontal mode*/ +@d vsize_code 4 /*page height in vertical mode*/ +@d max_depth_code 5 /*maximum depth of boxes on main pages*/ +@d split_max_depth_code 6 /*maximum depth of boxes on split pages*/ +@d box_max_depth_code 7 /*maximum depth of explicit vboxes*/ +@d hfuzz_code 8 /*tolerance for overfull hbox messages*/ +@d vfuzz_code 9 /*tolerance for overfull vbox messages*/ +@d delimiter_shortfall_code 10 /*maximum amount uncovered by variable delimiters*/ +@d null_delimiter_space_code 11 /*blank space in null delimiters*/ +@d script_space_code 12 /*extra space after subscript or superscript*/ +@d pre_display_size_code 13 /*length of text preceding a display*/ +@d display_width_code 14 /*length of line for displayed equation*/ +@d display_indent_code 15 /*indentation of line for displayed equation*/ +@d overfull_rule_code 16 /*width of rule that identifies overfull hboxes*/ +@d hang_indent_code 17 /*amount of hanging indentation*/ +@d h_offset_code 18 /*amount of horizontal offset when shipping pages out*/ +@d v_offset_code 19 /*amount of vertical offset when shipping pages out*/ +@d emergency_stretch_code 20 /*reduces badnesses on final pass of line-breaking*/ +@d page_width_code 21 /*current paper page width*/ +@d page_height_code 22 /*current paper page height*/ +@d dimen_pars (pdftex_last_dimen_code+1) /*total number of dimension parameters*/ +@d scaled_base (dimen_base+dimen_pars) + /*table of 256 user-defined \.{\\dimen} registers*/ +@d eqtb_size (scaled_base+255) /*largest subscript of |eqtb|*/ +@# +@d dimen(A) eqtb[scaled_base+A].sc +@d dimen_par(A) eqtb[dimen_base+A].sc /*a scaled quantity*/ +@d par_indent dimen_par(par_indent_code) +@d math_surround dimen_par(math_surround_code) +@d line_skip_limit dimen_par(line_skip_limit_code) +@d hsize dimen_par(hsize_code) +@d vsize dimen_par(vsize_code) +@d max_depth dimen_par(max_depth_code) +@d split_max_depth dimen_par(split_max_depth_code) +@d box_max_depth dimen_par(box_max_depth_code) +@d hfuzz dimen_par(hfuzz_code) +@d vfuzz dimen_par(vfuzz_code) +@d delimiter_shortfall dimen_par(delimiter_shortfall_code) +@d null_delimiter_space dimen_par(null_delimiter_space_code) +@d script_space dimen_par(script_space_code) +@d pre_display_size dimen_par(pre_display_size_code) +@d display_width dimen_par(display_width_code) +@d display_indent dimen_par(display_indent_code) +@d overfull_rule dimen_par(overfull_rule_code) +@d hang_indent dimen_par(hang_indent_code) +@d h_offset dimen_par(h_offset_code) +@d v_offset dimen_par(v_offset_code) +@d emergency_stretch dimen_par(emergency_stretch_code) +@d page_height dimen_par(page_height_code) + +@p static void print_length_param(int @!n) +{@+switch (n) { +case par_indent_code: print_esc("parindent");@+break; +case math_surround_code: print_esc("mathsurround");@+break; +case line_skip_limit_code: print_esc("lineskiplimit");@+break; +case hsize_code: print_esc("hsize");@+break; +case vsize_code: print_esc("vsize");@+break; +case max_depth_code: print_esc("maxdepth");@+break; +case split_max_depth_code: print_esc("splitmaxdepth");@+break; +case box_max_depth_code: print_esc("boxmaxdepth");@+break; +case hfuzz_code: print_esc("hfuzz");@+break; +case vfuzz_code: print_esc("vfuzz");@+break; +case delimiter_shortfall_code: print_esc("delimitershortfall");@+break; +case null_delimiter_space_code: print_esc("nulldelimiterspace");@+break; +case script_space_code: print_esc("scriptspace");@+break; +case pre_display_size_code: print_esc("predisplaysize");@+break; +case display_width_code: print_esc("displaywidth");@+break; +case display_indent_code: print_esc("displayindent");@+break; +case overfull_rule_code: print_esc("overfullrule");@+break; +case hang_indent_code: print_esc("hangindent");@+break; +case h_offset_code: print_esc("hoffset");@+break; +case v_offset_code: print_esc("voffset");@+break; +case emergency_stretch_code: print_esc("emergencystretch");@+break; +case page_width_code: + if (pdf_on) print_esc("pdfpagewidth"); + else print_esc("pagewidth"); + @+break; +case page_height_code: + if (pdf_on) print_esc("pdfpageheight"); + else print_esc("pageheight"); + @+break; +@<Cases for |print_lenght_param|@>@; +default:print("[unknown dimen parameter!]"); +} +} + +@ @<Put each...@>= +primitive("parindent", assign_dimen, dimen_base+par_indent_code);@/ +@!@:par\_indent\_}{\.{\\parindent} primitive@> +primitive("mathsurround", assign_dimen, dimen_base+math_surround_code);@/ +@!@:math\_surround\_}{\.{\\mathsurround} primitive@> +primitive("lineskiplimit", assign_dimen, dimen_base+line_skip_limit_code);@/ +@!@:line\_skip\_limit\_}{\.{\\lineskiplimit} primitive@> +primitive("hsize", assign_dimen, dimen_base+hsize_code);@/ +@!@:hsize\_}{\.{\\hsize} primitive@> +primitive("vsize", assign_dimen, dimen_base+vsize_code);@/ +@!@:vsize\_}{\.{\\vsize} primitive@> +primitive("maxdepth", assign_dimen, dimen_base+max_depth_code);@/ +@!@:max\_depth\_}{\.{\\maxdepth} primitive@> +primitive("splitmaxdepth", assign_dimen, dimen_base+split_max_depth_code);@/ +@!@:split\_max\_depth\_}{\.{\\splitmaxdepth} primitive@> +primitive("boxmaxdepth", assign_dimen, dimen_base+box_max_depth_code);@/ +@!@:box\_max\_depth\_}{\.{\\boxmaxdepth} primitive@> +primitive("hfuzz", assign_dimen, dimen_base+hfuzz_code);@/ +@!@:hfuzz\_}{\.{\\hfuzz} primitive@> +primitive("vfuzz", assign_dimen, dimen_base+vfuzz_code);@/ +@!@:vfuzz\_}{\.{\\vfuzz} primitive@> +primitive("delimitershortfall", + assign_dimen, dimen_base+delimiter_shortfall_code);@/ +@!@:delimiter\_shortfall\_}{\.{\\delimitershortfall} primitive@> +primitive("nulldelimiterspace", + assign_dimen, dimen_base+null_delimiter_space_code);@/ +@!@:null\_delimiter\_space\_}{\.{\\nulldelimiterspace} primitive@> +primitive("scriptspace", assign_dimen, dimen_base+script_space_code);@/ +@!@:script\_space\_}{\.{\\scriptspace} primitive@> +primitive("predisplaysize", assign_dimen, dimen_base+pre_display_size_code);@/ +@!@:pre\_display\_size\_}{\.{\\predisplaysize} primitive@> +primitive("displaywidth", assign_dimen, dimen_base+display_width_code);@/ +@!@:display\_width\_}{\.{\\displaywidth} primitive@> +primitive("displayindent", assign_dimen, dimen_base+display_indent_code);@/ +@!@:display\_indent\_}{\.{\\displayindent} primitive@> +primitive("overfullrule", assign_dimen, dimen_base+overfull_rule_code);@/ +@!@:overfull\_rule\_}{\.{\\overfullrule} primitive@> +primitive("hangindent", assign_dimen, dimen_base+hang_indent_code);@/ +@!@:hang\_indent\_}{\.{\\hangindent} primitive@> +primitive("hoffset", assign_dimen, dimen_base+h_offset_code);@/ +@!@:h\_offset\_}{\.{\\hoffset} primitive@> +primitive("voffset", assign_dimen, dimen_base+v_offset_code);@/ +@!@:v\_offset\_}{\.{\\voffset} primitive@> +primitive("emergencystretch", assign_dimen, dimen_base+emergency_stretch_code);@/ +@!@:emergency\_stretch\_}{\.{\\emergencystretch} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case assign_dimen: if (chr_code < scaled_base) + print_length_param(chr_code-dimen_base); + else{@+print_esc("dimen");print_int(chr_code-scaled_base); + } @+break; + +@ @<Initialize table entries...@>= +for (k=dimen_base; k<=eqtb_size; k++) eqtb[k].sc=0; + +@ @<Show equivalent |n|, in region 6@>= +{@+if (n < scaled_base) print_length_param(n-dimen_base); +else{@+print_esc("dimen");print_int(n-scaled_base); + } +print_char('=');print_scaled(eqtb[n].sc);print("pt"); +} + +@ Here is a procedure that displays the contents of |eqtb[n]| +symbolically. + +@p @t\4@>@<Declare the procedure called |print_cmd_chr|@>@;@/ +#ifdef @!STAT +static void show_eqtb(pointer @!n) +{@+if (n < active_base) print_char('?'); /*this can't happen*/ +else if (n < glue_base) @<Show equivalent |n|, in region 1 or 2@>@; +else if (n < local_base) @<Show equivalent |n|, in region 3@>@; +else if (n < int_base) @<Show equivalent |n|, in region 4@>@; +else if (n < dimen_base) @<Show equivalent |n|, in region 5@>@; +else if (n <= eqtb_size) @<Show equivalent |n|, in region 6@>@; +else print_char('?'); /*this can't happen either*/ +} +#endif + +@ The last two regions of |eqtb| have fullword values instead of the +three fields |eq_level|, |eq_type|, and |equiv|. An |eq_type| is unnecessary, +but \TeX\ needs to store the |eq_level| information in another array +called |xeq_level|. + +@<Glob...@>= +static memory_word @!eqtb0[eqtb_size-active_base+1], + *const @!eqtb = @!eqtb0-active_base; +static quarterword @!xeq_level0[eqtb_size-int_base+1], + *const @!xeq_level = @!xeq_level0-int_base; + +@ @<Set init...@>= +for (k=int_base; k<=eqtb_size; k++) xeq_level[k]=level_one; + +@ When the debugging routine |search_mem| is looking for pointers having a +given value, it is interested only in regions 1 to~3 of~|eqtb|, and in the +first part of region~4. + +@<Search |eqtb| for equivalents equal to |p|@>= +for (q=active_base; q<=box_base+255; q++) + {@+if (equiv(q)==p) + {@+print_nl("EQUIV(");print_int(q);print_char(')'); + } + } + +@* The hash table. +Control sequences are stored and retrieved by means of a fairly standard hash +table algorithm called the method of ``coalescing lists'' (cf.\ Algorithm 6.4C +in {\sl The Art of Computer Programming\/}). Once a control sequence enters the +table, it is never removed, because there are complicated situations +involving \.{\\gdef} where the removal of a control sequence at the end of +a group would be a mistake preventable only by the introduction of a +complicated reference-count mechanism. + +The actual sequence of letters forming a control sequence identifier is +stored in the |str_pool| array together with all the other strings. An +auxiliary array |hash| consists of items with two halfword fields per +word. The first of these, called |next(p)|, points to the next identifier +belonging to the same coalesced list as the identifier corresponding to~|p|; +and the other, called |text(p)|, points to the |str_start| entry for +|p|'s identifier. If position~|p| of the hash table is empty, we have +|text(p)==0|; if position |p| is either empty or the end of a coalesced +hash list, we have |next(p)==0|. An auxiliary pointer variable called +|hash_used| is maintained in such a way that all locations |p >= hash_used| +are nonempty. The global variable |cs_count| tells how many multiletter +control sequences have been defined, if statistics are being kept. + +A global boolean variable called |no_new_control_sequence| is set to +|true| during the time that new hash table entries are forbidden. + +@d next(A) hash[A].lh /*link for coalesced lists*/ +@d text(A) hash[A].rh /*string number for control sequence name*/ +@d hash_is_full (hash_used==hash_base) /*test if all positions are occupied*/ +@d font_id_text(A) text(font_id_base+A) /*a frozen font identifier's name*/ + +@<Glob...@>= +static two_halves @!hash0[undefined_control_sequence-hash_base], + *const @!hash = @!hash0-hash_base; + /*the hash table*/ +static pointer @!hash_used; /*allocation pointer for |hash|*/ +static bool @!no_new_control_sequence; /*are new identifiers legal?*/ +static int @!cs_count; /*total number of known identifiers*/ + +@ @<Set init...@>= +no_new_control_sequence=true; /*new identifiers are usually forbidden*/ +next(hash_base)=0;text(hash_base)=0; +for (k=hash_base+1; k<=undefined_control_sequence-1; k++) hash[k]=hash[hash_base]; + +@ @<Initialize table entries...@>= +hash_used=frozen_control_sequence; /*nothing is used*/ +cs_count=0; +eq_type(frozen_dont_expand)=dont_expand; +text(frozen_dont_expand)=s_no("notexpanded:"); +@.notexpanded:@> + +@ Here is the subroutine that searches the hash table for an identifier +that matches a given string of length |l > 1| appearing in |buffer[j dotdot +(j+l-1)]|. If the identifier is found, the corresponding hash table address +is returned. Otherwise, if the global variable |no_new_control_sequence| +is |true|, the dummy address |undefined_control_sequence| is returned. +Otherwise the identifier is inserted into the hash table and its location +is returned. + +@p static pointer id_lookup(int @!j, int @!l) /*search the hash table*/ +{@+ /*go here if you found it*/ +int h; /*hash code*/ +int @!d; /*number of characters in incomplete current string*/ +pointer @!p; /*index in |hash| array*/ +int @!k; /*index in |buffer| array*/ +@<Compute the hash code |h|@>; +p=h+hash_base; /*we start searching here; note that |0 <= h < hash_prime|*/ +loop@+{@+if (text(p) > 0) if (length(text(p))==l) + if (str_eq_buf(text(p), j)) goto found; + if (next(p)==0) + {@+if (no_new_control_sequence) + p=undefined_control_sequence; + else@<Insert a new control sequence after |p|, then make |p| point to +it@>; + goto found; + } + p=next(p); + } +found: return p; +} + +@ @<Insert a new control...@>= +{@+if (text(p) > 0) + {@+@/do@+{if (hash_is_full) overflow("hash size", hash_size); +@:TeX capacity exceeded hash size}{\quad hash size@> + decr(hash_used); + }@+ while (!(text(hash_used)==0)); /*search for an empty location in |hash|*/ + next(p)=hash_used;p=hash_used; + } +str_room(l);d=cur_length; +while (pool_ptr > str_start[str_ptr]) + {@+decr(pool_ptr);str_pool[pool_ptr+l]=str_pool[pool_ptr]; + } /*move current string up to make room for another*/ +for (k=j; k<=j+l-1; k++) append_char(buffer[k]); +text(p)=make_string();pool_ptr=pool_ptr+d; +#ifdef @!STAT +incr(cs_count); +#endif +@;@/ +} + +@ The value of |hash_prime| should be roughly 85\pct! of |hash_size|, and it +should be a prime number. The theory of hashing tells us to expect fewer +than two table probes, on the average, when the search is successful. +[See J.~S. Vitter, {\sl Journal of the ACM\/ \bf30} (1983), 231--258.] +@^Vitter, Jeffrey Scott@> + +@<Compute the hash code |h|@>= +h=buffer[j]; +for (k=j+1; k<=j+l-1; k++) + {@+h=h+h+buffer[k]; + while (h >= hash_prime) h=h-hash_prime; + } + +@ Single-character control sequences do not need to be looked up in a hash +table, since we can use the character code itself as a direct address. +The procedure |print_cs| prints the name of a control sequence, given +a pointer to its address in |eqtb|. A space is printed after the name +unless it is a single nonletter or an active character. This procedure +might be invoked with invalid data, so it is ``extra robust.'' The +individual characters must be printed one at a time using |print|, since +they may be unprintable. + +@<Basic printing...@>= +static void print_cs(int @!p) /*prints a purported control sequence*/ +{@+if (p < hash_base) /*single character*/ + if (p >= single_base) + if (p==null_cs) + {@+print_esc("csname");print_esc("endcsname");print_char(' '); + } + else{@+printn_esc(p-single_base); + if (cat_code(p-single_base)==letter) print_char(' '); + } + else if (p < active_base) print_esc("IMPOSSIBLE."); +@.IMPOSSIBLE@> + else printn(p-active_base); +else if (p >= undefined_control_sequence) print_esc("IMPOSSIBLE."); +else if ((text(p) < 0)||(text(p) >= str_ptr)) print_esc("NONEXISTENT."); +@.NONEXISTENT@> +else{@+if (p==frozen_primitive) print_esc("primitive"); + printn_esc(text(p));print_char(' '); + } +} + +@ Here is a similar procedure; it avoids the error checks, and it never +prints a space after the control sequence. + +@<Basic printing procedures@>= +static void sprint_cs(pointer @!p) /*prints a control sequence*/ +{@+if (p < hash_base) + if (p < single_base) printn(p-active_base); + else if (p < null_cs) printn_esc(p-single_base); + else{@+print_esc("csname");print_esc("endcsname"); + } +else printn_esc(text(p)); +} + +@ We need to put \TeX's ``primitive'' control sequences into the hash +table, together with their command code (which will be the |eq_type|) +and an operand (which will be the |equiv|). The |primitive| procedure +does this, in a way that no \TeX\ user can. The global value |cur_val| +contains the new |eqtb| pointer after |primitive| has acted. + +@p +#ifdef @!INIT +static void primitive(char *@!str, quarterword @!c, halfword @!o) +{@+str_number s=s_no(str); +int k; /*index into |str_pool|*/ +int @!j; /*index into |buffer|*/ +small_number @!l; /*length of the string*/ +pointer @!p; /*pointer in |ROM|*/ +if (s < 256) cur_val=s+single_base; +else{@+k=str_start[s];l=str_start[s+1]-k; + /*we will move |s| into the (possibly non-empty) |buffer|*/ + if (first+l > buf_size+1) + overflow("buffer size", buf_size); +@:TeX capacity exceeded buffer size}{\quad buffer size@> + for (j=0; j<=l-1; j++) buffer[first+j]=so(str_pool[k+j]); + cur_val=id_lookup(first, l); /*|no_new_control_sequence| is |false|*/ + flush_string;text(cur_val)=s; /*we don't want to have the string twice*/ + } +eq_level(cur_val)=level_one;eq_type(cur_val)=c;equiv(cur_val)=o; +@<Add primitive definition to the |ROM| array@>; +} +#endif + +@ Many of \TeX's primitives need no |equiv|, since they are identifiable +by their |eq_type| alone. These primitives are loaded into the hash table +as follows: + +@<Put each of \TeX's primitives into the hash table@>= +primitive(" ", ex_space, 0);@/ +@!@:Single-character primitives /}{\quad\.{\\\ }@> +primitive("/", ital_corr, 0);@/ +@!@:Single-character primitives /}{\quad\.{\\/}@> +primitive("accent", accent, 0);@/ +@!@:accent\_}{\.{\\accent} primitive@> +primitive("advance", advance, 0);@/ +@!@:advance\_}{\.{\\advance} primitive@> +primitive("afterassignment", after_assignment, 0);@/ +@!@:after\_assignment\_}{\.{\\afterassignment} primitive@> +primitive("aftergroup", after_group, 0);@/ +@!@:after\_group\_}{\.{\\aftergroup} primitive@> +primitive("begingroup", begin_group, 0);@/ +@!@:begin\_group\_}{\.{\\begingroup} primitive@> +primitive("char", char_num, 0);@/ +@!@:char\_}{\.{\\char} primitive@> +primitive("csname", cs_name, 0);@/ +@!@:cs\_name\_}{\.{\\csname} primitive@> +primitive("delimiter", delim_num, 0);@/ +@!@:delimiter\_}{\.{\\delimiter} primitive@> +primitive("divide", divide, 0);@/ +@!@:divide\_}{\.{\\divide} primitive@> +primitive("endcsname", end_cs_name, 0);@/ +@!@:end\_cs\_name\_}{\.{\\endcsname} primitive@> +primitive("endgroup", end_group, 0); +@!@:end\_group\_}{\.{\\endgroup} primitive@> +text(frozen_end_group)=text(cur_val);eqtb[frozen_end_group]=eqtb[cur_val];@/ +primitive("expandafter", expand_after, 0);@/ +@!@:expand\_after\_}{\.{\\expandafter} primitive@> +primitive("font", def_font, 0);@/ +@!@:font\_}{\.{\\font} primitive@> +primitive("fontdimen", assign_font_dimen, 0);@/ +@!@:font\_dimen\_}{\.{\\fontdimen} primitive@> +primitive("halign", halign, 0);@/ +@!@:halign\_}{\.{\\halign} primitive@> +primitive("hrule", hrule, 0);@/ +@!@:hrule\_}{\.{\\hrule} primitive@> +primitive("ignorespaces", ignore_spaces, 0);@/ +@!@:ignore\_spaces\_}{\.{\\ignorespaces} primitive@> +primitive("insert", insert, 0);@/ +@!@:insert\_}{\.{\\insert} primitive@> +primitive("mark", mark, 0);@/ +@!@:mark\_}{\.{\\mark} primitive@> +primitive("mathaccent", math_accent, 0);@/ +@!@:math\_accent\_}{\.{\\mathaccent} primitive@> +primitive("mathchar", math_char_num, 0);@/ +@!@:math\_char\_}{\.{\\mathchar} primitive@> +primitive("mathchoice", math_choice, 0);@/ +@!@:math\_choice\_}{\.{\\mathchoice} primitive@> +primitive("multiply", multiply, 0);@/ +@!@:multiply\_}{\.{\\multiply} primitive@> +primitive("noalign", no_align, 0);@/ +@!@:no\_align\_}{\.{\\noalign} primitive@> +primitive("noboundary", no_boundary, 0);@/ +@!@:no\_boundary\_}{\.{\\noboundary} primitive@> +primitive("noexpand", no_expand, 0);@/ +@!@:no\_expand\_}{\.{\\noexpand} primitive@> +primitive("nonscript", non_script, 0);@/ +@!@:non\_script\_}{\.{\\nonscript} primitive@> +primitive("omit", omit, 0);@/ +@!@:omit\_}{\.{\\omit} primitive@> +primitive("parshape", set_shape, par_shape_loc);@/ +@!@:par\_shape\_}{\.{\\parshape} primitive@> +primitive("penalty", break_penalty, 0);@/ +@!@:penalty\_}{\.{\\penalty} primitive@> +primitive("prevgraf", set_prev_graf, 0);@/ +@!@:prev\_graf\_}{\.{\\prevgraf} primitive@> +primitive("radical", radical, 0);@/ +@!@:radical\_}{\.{\\radical} primitive@> +primitive("read", read_to_cs, 0);@/ +@!@:read\_}{\.{\\read} primitive@> +primitive("relax", relax, 256); /*cf.\ |scan_file_name|*/ +@!@:relax\_}{\.{\\relax} primitive@> +text(frozen_relax)=text(cur_val);eqtb[frozen_relax]=eqtb[cur_val];@/ +primitive("setbox", set_box, 0);@/ +@!@:set\_box\_}{\.{\\setbox} primitive@> +primitive("the", the, 0);@/ +@!@:the\_}{\.{\\the} primitive@> +primitive("toks", toks_register, mem_bot);@/ +@!@:toks\_}{\.{\\toks} primitive@> +primitive("vadjust", vadjust, 0);@/ +@!@:vadjust\_}{\.{\\vadjust} primitive@> +primitive("valign", valign, 0);@/ +@!@:valign\_}{\.{\\valign} primitive@> +primitive("vcenter", vcenter, 0);@/ +@!@:vcenter\_}{\.{\\vcenter} primitive@> +primitive("vrule", vrule, 0);@/ +@!@:vrule\_}{\.{\\vrule} primitive@> + +@ Each primitive has a corresponding inverse, so that it is possible to +display the cryptic numeric contents of |eqtb| in symbolic form. +Every call of |primitive| in this program is therefore accompanied by some +straightforward code that forms part of the |print_cmd_chr| routine +below. + +@<Cases of |print_cmd_chr|...@>= +case accent: print_esc("accent");@+break; +case advance: print_esc("advance");@+break; +case after_assignment: print_esc("afterassignment");@+break; +case after_group: print_esc("aftergroup");@+break; +case assign_font_dimen: print_esc("fontdimen");@+break; +case begin_group: print_esc("begingroup");@+break; +case break_penalty: print_esc("penalty");@+break; +case char_num: print_esc("char");@+break; +case cs_name: print_esc("csname");@+break; +case def_font: print_esc("font");@+break; +case delim_num: print_esc("delimiter");@+break; +case divide: print_esc("divide");@+break; +case end_cs_name: print_esc("endcsname");@+break; +case end_group: print_esc("endgroup");@+break; +case ex_space: print_esc(" ");@+break; +case expand_after: switch (chr_code) { +case 0: print_esc("expandafter");@+break; +@/@<Cases of |expandafter| for |print_cmd_chr|@>@/ +} @+break; /*there are no other cases*/ +case halign: print_esc("halign");@+break; +case hrule: print_esc("hrule");@+break; +case ignore_spaces: print_esc("ignorespaces");@+break; +case insert: print_esc("insert");@+break; +case ital_corr: print_esc("/");@+break; +case mark: {@+print_esc("mark"); + if (chr_code > 0) print_char('s'); + } @+break; +case math_accent: print_esc("mathaccent");@+break; +case math_char_num: print_esc("mathchar");@+break; +case math_choice: print_esc("mathchoice");@+break; +case multiply: print_esc("multiply");@+break; +case no_align: print_esc("noalign");@+break; +case no_boundary: print_esc("noboundary");@+break; +case no_expand: print_esc("noexpand");@+break; +case non_script: print_esc("nonscript");@+break; +case omit: print_esc("omit");@+break; +case radical: print_esc("radical");@+break; +case read_to_cs: if (chr_code==0) print_esc("read") + @<Cases of |read| for |print_cmd_chr|@>;@+break; +case relax: print_esc("relax");@+break; +case set_box: print_esc("setbox");@+break; +case set_prev_graf: print_esc("prevgraf");@+break; +case set_shape: switch (chr_code) { + case par_shape_loc: print_esc("parshape");@+break; + @<Cases of |set_shape| for |print_cmd_chr|@>@;@/ + } @+break; /*there are no other cases*/ +case the: if (chr_code==0) print_esc("the") + @<Cases of |the| for |print_cmd_chr|@>;@+break; +case toks_register: @<Cases of |toks_register| for |print_cmd_chr|@>@;@+break; +case vadjust: print_esc("vadjust");@+break; +case valign: print_esc("valign");@+break; +case vcenter: print_esc("vcenter");@+break; +case vrule: print_esc("vrule");@+break; + +@ We will deal with the other primitives later, at some point in the program +where their |eq_type| and |equiv| values are more meaningful. For example, +the primitives for math mode will be loaded when we consider the routines +that deal with formulas. It is easy to find where each particular +primitive was treated by looking in the index at the end; for example, the +section where |"radical"| entered |eqtb| is listed under `\.{\\radical} +primitive'. (Primitives consisting of a single nonalphabetic character, +@!like `\.{\\/}', are listed under `Single-character primitives'.) +@!@^Single-character primitives@> + +Meanwhile, this is a convenient place to catch up on something we were unable +to do before the hash table was defined: + +@<Print the font identifier for |font(p)|@>= +printn_esc(font_id_text(font(p))) + +@* Saving and restoring equivalents. +The nested structure provided by `$\.{\char'173}\ldots\.{\char'175}$' groups +in \TeX\ means that |eqtb| entries valid in outer groups should be saved +and restored later if they are overridden inside the braces. When a new |eqtb| +value is being assigned, the program therefore checks to see if the previous +entry belongs to an outer level. In such a case, the old value is placed +on the |save_stack| just before the new value enters |eqtb|. At the +end of a grouping level, i.e., when the right brace is sensed, the +|save_stack| is used to restore the outer values, and the inner ones are +destroyed. + +Entries on the |save_stack| are of type |memory_word|. The top item on +this stack is |save_stack[p]|, where |p==save_ptr-1|; it contains three +fields called |save_type|, |save_level|, and |save_index|, and it is +interpreted in one of five ways: + +\yskip\hangg 1) If |save_type(p)==restore_old_value|, then +|save_index(p)| is a location in |eqtb| whose current value should +be destroyed at the end of the current group and replaced by |save_stack[p-1]|. +Furthermore if |save_index(p) >= int_base|, then |save_level(p)| +should replace the corresponding entry in |xeq_level|. + +\yskip\hangg 2) If |save_type(p)==restore_zero|, then |save_index(p)| +is a location in |eqtb| whose current value should be destroyed at the end +of the current group, when it should be +replaced by the value of |eqtb[undefined_control_sequence]|. + +\yskip\hangg 3) If |save_type(p)==insert_token|, then |save_index(p)| +is a token that should be inserted into \TeX's input when the current +group ends. + +\yskip\hangg 4) If |save_type(p)==level_boundary|, then |save_level(p)| +is a code explaining what kind of group we were previously in, and +|save_index(p)| points to the level boundary word at the bottom of +the entries for that group. +Furthermore, in extended \eTeX\ mode, |save_stack[p-1]| contains the +source line number at which the current level of grouping was entered. + +\yskip\hang 5) If |save_type(p)==restore_sa|, then |sa_chain| points to a +chain of sparse array entries to be restored at the end of the current +group. Furthermore |save_index(p)| and |save_level(p)| should replace +the values of |sa_chain| and |sa_level| respectively. + +@d save_type(A) save_stack[A].hh.b0 /*classifies a |save_stack| entry*/ +@d save_level(A) save_stack[A].hh.b1 + /*saved level for regions 5 and 6, or group code*/ +@d save_index(A) save_stack[A].hh.rh + /*|eqtb| location or token or |save_stack| location*/ +@d restore_old_value 0 /*|save_type| when a value should be restored later*/ +@d restore_zero 1 /*|save_type| when an undefined entry should be restored*/ +@d insert_token 2 /*|save_type| when a token is being saved for later use*/ +@d level_boundary 3 /*|save_type| corresponding to beginning of group*/ +@d restore_sa 4 /*|save_type| when sparse array entries should be restored*/ + +@p @t\4@>@<Declare \eTeX\ procedures for tracing and input@>@; + +@ Here are the group codes that are used to discriminate between different +kinds of groups. They allow \TeX\ to decide what special actions, if any, +should be performed when a group ends. +\def\grp{\.{\char'173...\char'175}} + +Some groups are not supposed to be ended by right braces. For example, +the `\.\$' that begins a math formula causes a |math_shift_group| to +be started, and this should be terminated by a matching `\.\$'. Similarly, +a group that starts with \.{\\left} should end with \.{\\right}, and +one that starts with \.{\\begingroup} should end with \.{\\endgroup}. + +@d bottom_level 0 /*group code for the outside world*/ +@d simple_group 1 /*group code for local structure only*/ +@d hbox_group 2 /*code for `\.{\\hbox}\grp'*/ +@d adjusted_hbox_group 3 /*code for `\.{\\hbox}\grp' in vertical mode*/ +@d vbox_group 4 /*code for `\.{\\vbox}\grp'*/ +@d vtop_group 5 /*code for `\.{\\vtop}\grp'*/ +@d align_group 6 /*code for `\.{\\halign}\grp', `\.{\\valign}\grp'*/ +@d no_align_group 7 /*code for `\.{\\noalign}\grp'*/ +@d output_group 8 /*code for output routine*/ +@d math_group 9 /*code for, e.g., `\.{\char'136}\grp'*/ +@d disc_group 10 /*code for `\.{\\discretionary}\grp\grp\grp'*/ +@d insert_group 11 /*code for `\.{\\insert}\grp', `\.{\\vadjust}\grp'*/ +@d vcenter_group 12 /*code for `\.{\\vcenter}\grp'*/ +@d math_choice_group 13 /*code for `\.{\\mathchoice}\grp\grp\grp\grp'*/ +@d semi_simple_group 14 /*code for `\.{\\begingroup...\\endgroup}'*/ +@d math_shift_group 15 /*code for `\.{\$...\$}'*/ +@d math_left_group 16 /*code for `\.{\\left...\\right}'*/ +@d max_group_code 16 + +@<Types...@>= +typedef int8_t group_code; /*|save_level| for a level boundary*/ + +@ The global variable |cur_group| keeps track of what sort of group we are +currently in. Another global variable, |cur_boundary|, points to the +topmost |level_boundary| word. And |cur_level| is the current depth of +nesting. The routines are designed to preserve the condition that no entry +in the |save_stack| or in |eqtb| ever has a level greater than |cur_level|. + +@ @<Glob...@>= +static memory_word @!save_stack[save_size+1]; +static int @!save_ptr; /*first unused entry on |save_stack|*/ +static int @!max_save_stack; /*maximum usage of save stack*/ +static quarterword @!cur_level; /*current nesting level for groups*/ +static group_code @!cur_group; /*current group type*/ +static int @!cur_boundary; /*where the current level begins*/ + +@ At this time it might be a good idea for the reader to review the introduction +to |eqtb| that was given above just before the long lists of parameter names. +Recall that the ``outer level'' of the program is |level_one|, since +undefined control sequences are assumed to be ``defined'' at |level_zero|. + +@<Set init...@>= +save_ptr=0;cur_level=level_one;cur_group=bottom_level;cur_boundary=0; +max_save_stack=0; + +@ The following macro is used to test if there is room for up to seven more +entries on |save_stack|. By making a conservative test like this, we can +get by with testing for overflow in only a few places. + +@d check_full_save_stack if (save_ptr > max_save_stack) + {@+max_save_stack=save_ptr; + if (max_save_stack > save_size-7) overflow("save size", save_size); +@:TeX capacity exceeded save size}{\quad save size@> + } + +@ Procedure |new_save_level| is called when a group begins. The +argument is a group identification code like `|hbox_group|'. After +calling this routine, it is safe to put five more entries on |save_stack|. + +In some cases integer-valued items are placed onto the +|save_stack| just below a |level_boundary| word, because this is a +convenient place to keep information that is supposed to ``pop up'' just +when the group has finished. +For example, when `\.{\\hbox to 100pt}\grp' is being treated, the 100pt +dimension is stored on |save_stack| just before |new_save_level| is +called. + +We use the notation |saved(k)| to stand for an integer item that +appears in location |save_ptr+k| of the save stack. + +@d saved(A) save_stack[save_ptr+A].i + +@p static void new_save_level(group_code @!c) /*begin a new level of grouping*/ +{@+check_full_save_stack; +if (eTeX_ex) + {@+saved(0)=line;incr(save_ptr); + } +save_type(save_ptr)=level_boundary;save_level(save_ptr)=cur_group; +save_index(save_ptr)=cur_boundary; +if (cur_level==max_quarterword) overflow("grouping levels", +@:TeX capacity exceeded grouping levels}{\quad grouping levels@> + max_quarterword-min_quarterword); + /*quit if |(cur_level+1)| is too big to be stored in |eqtb|*/ +cur_boundary=save_ptr;cur_group=c; +#ifdef @!STAT +if (tracing_groups > 0) group_trace(false); +#endif +@;@/ +incr(cur_level);incr(save_ptr); +} + +@ Just before an entry of |eqtb| is changed, the following procedure should +be called to update the other data structures properly. It is important +to keep in mind that reference counts in |mem| include references from +within |save_stack|, so these counts must be handled carefully. +@^reference counts@> + +@p static void eq_destroy(memory_word @!w) /*gets ready to forget |w|*/ +{@+pointer q; /*|equiv| field of |w|*/ +switch (eq_type_field(w)) { +case call: case long_call: case outer_call: + case long_outer_call: delete_token_ref(equiv_field(w));@+break; +case glue_ref: delete_glue_ref(equiv_field(w));@+break; +case shape_ref: {@+q=equiv_field(w); /*we need to free a \.{\\parshape} block*/ + if (q!=null) free_node(q, info(q)+info(q)+1); + } @+break; /*such a block is |2 n+1| words long, where |n==info(q)|*/ +case box_ref: flush_node_list(equiv_field(w));@+break; +@/@<Cases for |eq_destroy|@>@/ +default:do_nothing; +} +} + +@ To save a value of |eqtb[p]| that was established at level |l|, we +can use the following subroutine. + +@p static void eq_save(pointer @!p, quarterword @!l) /*saves |eqtb[p]|*/ +{@+check_full_save_stack; +if (l==level_zero) save_type(save_ptr)=restore_zero; +else{@+save_stack[save_ptr]=eqtb[p];incr(save_ptr); + save_type(save_ptr)=restore_old_value; + } +save_level(save_ptr)=l;save_index(save_ptr)=p;incr(save_ptr); +} + +@ The procedure |eq_define| defines an |eqtb| entry having specified +|eq_type| and |equiv| fields, and saves the former value if appropriate. +This procedure is used only for entries in the first four regions of |eqtb|, +i.e., only for entries that have |eq_type| and |equiv| fields. +After calling this routine, it is safe to put four more entries on +|save_stack|, provided that there was room for four more entries before +the call, since |eq_save| makes the necessary test. + +@p +#ifdef @!STAT +#define assign_trace(A, B) if (tracing_assigns > 0) restore_trace(A, B); +#else +#define assign_trace(A, B) +#endif + +static void eq_define(pointer @!p, quarterword @!t, halfword @!e) + /*new data for |eqtb|*/ +{@+ +if (eTeX_ex&&(eq_type(p)==t)&&(equiv(p)==e)) + {@+assign_trace(p,"reassigning")@;@/ + eq_destroy(eqtb[p]);return; + } +assign_trace(p,"changing")@;@/ +if (eq_level(p)==cur_level) eq_destroy(eqtb[p]); +else if (cur_level > level_one) eq_save(p, eq_level(p)); +eq_level(p)=cur_level;eq_type(p)=t;equiv(p)=e; +assign_trace(p,"into")@;@/ +} + +@ The counterpart of |eq_define| for the remaining (fullword) positions in +|eqtb| is called |eq_word_define|. Since |xeq_level[p] >= level_one| for all +|p|, a `|restore_zero|' will never be used in this case. + +@p static void eq_word_define(pointer @!p, int @!w) +{@+ +if (eTeX_ex&&(eqtb[p].i==w)) + {@+assign_trace(p,"reassigning")@;@/ + return; + } +assign_trace(p,"changing")@;@/ +if (xeq_level[p]!=cur_level) + {@+eq_save(p, xeq_level[p]);xeq_level[p]=cur_level; + } +eqtb[p].i=w; +assign_trace(p,"into")@;@/ +} + +@ The |eq_define| and |eq_word_define| routines take care of local definitions. +@^global definitions@> +Global definitions are done in almost the same way, but there is no need +to save old values, and the new value is associated with |level_one|. + +@p static void geq_define(pointer @!p, quarterword @!t, halfword @!e) + /*global |eq_define|*/ +{@+assign_trace(p,"globally changing")@;@/ +{@+eq_destroy(eqtb[p]); +eq_level(p)=level_one;eq_type(p)=t;equiv(p)=e; +} +assign_trace(p,"into");@/ +} +@# +static void geq_word_define(pointer @!p, int @!w) /*global |eq_word_define|*/ +{@+assign_trace(p,"globally changing")@;@/ +{@+eqtb[p].i=w;xeq_level[p]=level_one; +} +assign_trace(p,"into");@/ +} + +@ Subroutine |save_for_after| puts a token on the stack for save-keeping. + +@p static void save_for_after(halfword @!t) +{@+if (cur_level > level_one) + {@+check_full_save_stack; + save_type(save_ptr)=insert_token;save_level(save_ptr)=level_zero; + save_index(save_ptr)=t;incr(save_ptr); + } +} + +@ The |unsave| routine goes the other way, taking items off of |save_stack|. +This routine takes care of restoration when a level ends; everything +belonging to the topmost group is cleared off of the save stack. + +@p +static void back_input(void); +static void unsave(void) /*pops the top level off the save stack*/ +{@+ +pointer p; /*position to be restored*/ +quarterword @!l; /*saved level, if in fullword regions of |eqtb|*/ +halfword @!t; /*saved value of |cur_tok|*/ +bool @!a; /*have we already processed an \.{\\aftergroup} ?*/ +a=false; +if (cur_level > level_one) + {@+decr(cur_level); + @<Clear off top level from |save_stack|@>; + } +else confusion("curlevel"); /*|unsave| is not used when |cur_group==bottom_level|*/ +@:this can't happen curlevel}{\quad curlevel@> +} + +@ @<Clear off...@>= +loop@+{@+decr(save_ptr); + if (save_type(save_ptr)==level_boundary) goto done; + p=save_index(save_ptr); + if (save_type(save_ptr)==insert_token) + @<Insert token |p| into \TeX's input@>@; + else if (save_type(save_ptr)==restore_sa) + {@+sa_restore();sa_chain=p;sa_level=save_level(save_ptr); + } + else{@+if (save_type(save_ptr)==restore_old_value) + {@+l=save_level(save_ptr);decr(save_ptr); + } + else save_stack[save_ptr]=eqtb[undefined_control_sequence]; + @<Store \(s)|save_stack[save_ptr]| in |eqtb[p]|, unless |eqtb[p]| holds +a global value@>; + } + } +done: +#ifdef @!STAT +if (tracing_groups > 0) group_trace(true); +#endif +@;@/ +if (grp_stack[in_open]==cur_boundary) group_warning(); + /*groups possibly not properly nested with files*/ +cur_group=save_level(save_ptr);cur_boundary=save_index(save_ptr); +if (eTeX_ex) decr(save_ptr) + +@ A global definition, which sets the level to |level_one|, +@^global definitions@> +will not be undone by |unsave|. If at least one global definition of +|eqtb[p]| has been carried out within the group that just ended, the +last such definition will therefore survive. + +@<Store \(s)|save...@>= +if (p < int_base) + if (eq_level(p)==level_one) + {@+eq_destroy(save_stack[save_ptr]); /*destroy the saved value*/ +#ifdef @!STAT + if (tracing_restores > 0) restore_trace(p,"retaining"); +#endif +@;@/ + } + else{@+eq_destroy(eqtb[p]); /*destroy the current value*/ + eqtb[p]=save_stack[save_ptr]; /*restore the saved value*/ +#ifdef @!STAT + if (tracing_restores > 0) restore_trace(p,"restoring"); +#endif +@;@/ + } +else if (xeq_level[p]!=level_one) + {@+eqtb[p]=save_stack[save_ptr];xeq_level[p]=l; +#ifdef @!STAT + if (tracing_restores > 0) restore_trace(p,"restoring"); +#endif +@;@/ + } +else{ +#ifdef @!STAT + if (tracing_restores > 0) restore_trace(p,"retaining"); +#endif +@;@/ + } + +@ @<Declare \eTeX\ procedures for tr...@>= +#ifdef @!STAT +static void restore_trace(pointer @!p, char *@!s) + /*|eqtb[p]| has just been restored or retained*/ +{@+begin_diagnostic();print_char('{');print(s);print_char(' '); +show_eqtb(p);print_char('}'); +end_diagnostic(false); +} +#endif + +@ When looking for possible pointers to a memory location, it is helpful +to look for references from |eqtb| that might be waiting on the +save stack. Of course, we might find spurious pointers too; but this +routine is merely an aid when debugging, and at such times we are +grateful for any scraps of information, even if they prove to be irrelevant. +@^dirty \PASCAL@> + +@<Search |save_stack| for equivalents that point to |p|@>= +if (save_ptr > 0) for (q=0; q<=save_ptr-1; q++) + {@+if (equiv_field(save_stack[q])==p) + {@+print_nl("SAVE(");print_int(q);print_char(')'); + } + } + +@ Most of the parameters kept in |eqtb| can be changed freely, but there's +an exception: The magnification should not be used with two different +values during any \TeX\ job, since a single magnification is applied to an +entire run. The global variable |mag_set| is set to the current magnification +whenever it becomes necessary to ``freeze'' it at a particular value. + +@<Glob...@>= +static int @!mag_set; /*if nonzero, this magnification should be used henceforth*/ + +@ @<Set init...@>= +mag_set=0; + +@ The |prepare_mag| subroutine is called whenever \TeX\ wants to use |mag| +for magnification. + +@p static void prepare_mag(void) +{@+if ((mag_set > 0)&&(mag!=mag_set)) + {@+print_err("Incompatible magnification (");print_int(mag); +@.Incompatible magnification@> + print(");");print_nl(" the previous value will be retained"); + help2("I can handle only one magnification ratio per job. So I've",@/ + "reverted to the magnification you used earlier on this run.");@/ + int_error(mag_set); + geq_word_define(int_base+mag_code, mag_set); /*|mag=mag_set|*/ + } +if ((mag <= 0)||(mag > 32768)) + {@+print_err("Illegal magnification has been changed to 1000");@/ +@.Illegal magnification...@> + help1("The magnification ratio must be between 1 and 32768."); + int_error(mag);geq_word_define(int_base+mag_code, 1000); + } +mag_set=mag; +} + +@* Token lists. +A \TeX\ token is either a character or a control sequence, and it is +@^token@> +represented internally in one of two ways: (1)~A character whose ASCII +code number is |c| and whose command code is |m| is represented as the +number $2^8m+c$; the command code is in the range |1 <= m <= 14|. (2)~A control +sequence whose |eqtb| address is |p| is represented as the number +|cs_token_flag+p|. Here |cs_token_flag==@t$2^{12}-1$@>| is larger than +$2^8m+c$, yet it is small enough that |cs_token_flag+p < max_halfword|; +thus, a token fits comfortably in a halfword. + +A token |t| represents a |left_brace| command if and only if +|t < left_brace_limit|; it represents a |right_brace| command if and only if +we have |left_brace_limit <= t < right_brace_limit|; and it represents a |match| or +|end_match| command if and only if |match_token <= t <= end_match_token|. +The following definitions take care of these token-oriented constants +and a few others. + +@d cs_token_flag 07777 /*amount added to the |eqtb| location in a + token that stands for a control sequence; is a multiple of~256, less~1*/ +@d left_brace_token 00400 /*$2^8\cdot|left_brace|$*/ +@d left_brace_limit 01000 /*$2^8\cdot(|left_brace|+1)$*/ +@d right_brace_token 01000 /*$2^8\cdot|right_brace|$*/ +@d right_brace_limit 01400 /*$2^8\cdot(|right_brace|+1)$*/ +@d math_shift_token 01400 /*$2^8\cdot|math_shift|$*/ +@d tab_token 02000 /*$2^8\cdot|tab_mark|$*/ +@d out_param_token 02400 /*$2^8\cdot|out_param|$*/ +@d space_token 05040 /*$2^8\cdot|spacer|+|' '|$*/ +@d letter_token 05400 /*$2^8\cdot|letter|$*/ +@d other_token 06000 /*$2^8\cdot|other_char|$*/ +@d match_token 06400 /*$2^8\cdot|match|$*/ +@d end_match_token 07000 /*$2^8\cdot|end_match|$*/ +@d protected_token 07001 /*$2^8\cdot|end_match|+1$*/ + +@ @<Check the ``constant''...@>= +if (cs_token_flag+undefined_control_sequence > max_halfword) bad=21; + +@ A token list is a singly linked list of one-word nodes in |mem|, where +each word contains a token and a link. Macro definitions, output-routine +definitions, marks, \.{\\write} texts, and a few other things +are remembered by \TeX\ in the form +of token lists, usually preceded by a node with a reference count in its +|token_ref_count| field. The token stored in location |p| is called +|info(p)|. + +Three special commands appear in the token lists of macro definitions. +When |m==match|, it means that \TeX\ should scan a parameter +for the current macro; when |m==end_match|, it means that parameter +matching should end and \TeX\ should start reading the macro text; and +when |m==out_param|, it means that \TeX\ should insert parameter +number |c| into the text at this point. + +The enclosing \.{\char'173} and \.{\char'175} characters of a macro +definition are omitted, but an output routine +will be enclosed in braces. + +Here is an example macro definition that illustrates these conventions. +After \TeX\ processes the text +$$\.{\\def\\mac a\#1\#2 \\b \{\#1\\-a \#\#1\#2 \#2\}}$$ +the definition of \.{\\mac} is represented as a token list containing +$$\def\,{\hskip2pt} +\vbox{\halign{\hfil#\hfil\cr +(reference count), |letter|\,\.a, |match|\,\#, |match|\,\#, |spacer|\,\.\ , +\.{\\b}, |end_match|,\cr +|out_param|\,1, \.{\\-}, |letter|\,\.a, |spacer|\,\.\ , |mac_param|\,\#, +|other_char|\,\.1,\cr +|out_param|\,2, |spacer|\,\.\ , |out_param|\,2.\cr}}$$ +The procedure |scan_toks| builds such token lists, and |macro_call| +does the parameter matching. +@^reference counts@> + +Examples such as +$$\.{\\def\\m\{\\def\\m\{a\}\ b\}}$$ +explain why reference counts would be needed even if \TeX\ had no \.{\\let} +operation: When the token list for \.{\\m} is being read, the redefinition of +\.{\\m} changes the |eqtb| entry before the token list has been fully +consumed, so we dare not simply destroy a token list when its +control sequence is being redefined. + +If the parameter-matching part of a definition ends with `\.{\#\{}', +the corresponding token list will have `\.\{' just before the `|end_match|' +and also at the very end. The first `\.\{' is used to delimit the parameter; the +second one keeps the first from disappearing. + +@ The procedure |show_token_list|, which prints a symbolic form of +the token list that starts at a given node |p|, illustrates these +conventions. The token list being displayed should not begin with a reference +count. However, the procedure is intended to be robust, so that if the +memory links are awry or if |p| is not really a pointer to a token list, +nothing catastrophic will happen. + +An additional parameter |q| is also given; this parameter is either null +or it points to a node in the token list where a certain magic computation +takes place that will be explained later. (Basically, |q| is non-null when +we are printing the two-line context information at the time of an error +message; |q| marks the place corresponding to where the second line +should begin.) + +For example, if |p| points to the node containing the first \.a in the +token list above, then |show_token_list| will print the string +$$\hbox{`\.{a\#1\#2\ \\b\ ->\#1\\-a\ \#\#1\#2\ \#2}';}$$ +and if |q| points to the node containing the second \.a, +the magic computation will be performed just before the second \.a is printed. + +The generation will stop, and `\.{\\ETC.}' will be printed, if the length +of printing exceeds a given limit~|l|. Anomalous entries are printed in the +form of control sequences that are not followed by a blank space, e.g., +`\.{\\BAD.}'; this cannot be confused with actual control sequences because +a real control sequence named \.{BAD} would come out `\.{\\BAD\ }'. + +@<Declare the procedure called |show_token_list|@>= +static void show_token_list(int @!p, int @!q, int @!l) +{@+ +int m, @!c; /*pieces of a token*/ +ASCII_code @!match_chr; /*character used in a `|match|'*/ +ASCII_code @!n; /*the highest parameter number, as an ASCII digit*/ +match_chr='#';n='0';tally=0; +while ((p!=null)&&(tally < l)) + {@+if (p==q) @<Do magic computation@>; + @<Display token |p|, and |return| if there are problems@>; + p=link(p); + } +if (p!=null) print_esc("ETC."); +@.ETC@> + +} + +@ @<Display token |p|...@>= +if ((p < hi_mem_min)||(p > mem_end)) + {@+print_esc("CLOBBERED.");return; +@.CLOBBERED@> + } +if (info(p) >= cs_token_flag) print_cs(info(p)-cs_token_flag); +else{@+m=info(p)/0400;c=info(p)%0400; + if (info(p) < 0) print_esc("BAD."); +@.BAD@> + else@<Display the token $(|m|,|c|)$@>; + } + +@ The procedure usually ``learns'' the character code used for macro +parameters by seeing one in a |match| command before it runs into any +|out_param| commands. + +@<Display the token...@>= +switch (m) { +case left_brace: case right_brace: case math_shift: + case tab_mark: case sup_mark: case sub_mark: + case spacer: + case letter: case other_char: printn(c);@+break; +case mac_param: {@+printn(c);printn(c); + } @+break; +case out_param: {@+printn(match_chr); + if (c <= 9) print_char(c+'0'); + else{@+print_char('!');return; + } + } @+break; +case match: {@+match_chr=c;printn(c);incr(n);print_char(n); + if (n > '9') return; + } @+break; +case end_match: if (c==0) print("->");@+break; +@.->@> +default:print_esc("BAD."); +@.BAD@> +} + +@ Here's the way we sometimes want to display a token list, given a pointer +to its reference count; the pointer may be null. + +@p static void token_show(pointer @!p) +{@+if (p!=null) show_token_list(link(p), null, 10000000); +} + +@ The |print_meaning| subroutine displays |cur_cmd| and |cur_chr| in +symbolic form, including the expansion of a macro or mark. + +@p static void print_meaning(void) +{@+print_cmd_chr(cur_cmd, cur_chr); +if (cur_cmd >= call) + {@+print_char(':');print_ln();token_show(cur_chr); + } +else if ((cur_cmd==top_bot_mark)&&(cur_chr < marks_code)) + {@+print_char(':');print_ln(); + token_show(cur_mark[cur_chr]); + } +} + +@* Introduction to the syntactic routines. +Let's pause a moment now and try to look at the Big Picture. +The \TeX\ program consists of three main parts: syntactic routines, +semantic routines, and output routines. The chief purpose of the +syntactic routines is to deliver the user's input to the semantic routines, +one token at a time. The semantic routines act as an interpreter +responding to these tokens, which may be regarded as commands. And the +output routines are periodically called on to convert box-and-glue +lists into a compact set of instructions that will be sent +to a typesetter. We have discussed the basic data structures and utility +routines of \TeX, so we are good and ready to plunge into the real activity by +considering the syntactic routines. + +Our current goal is to come to grips with the |get_next| procedure, +which is the keystone of \TeX's input mechanism. Each call of |get_next| +sets the value of three variables |cur_cmd|, |cur_chr|, and |cur_cs|, +representing the next input token. +$$\vbox{\halign{#\hfil\cr + \hbox{|cur_cmd| denotes a command code from the long list of codes + given above;}\cr + \hbox{|cur_chr| denotes a character code or other modifier of the command + code;}\cr + \hbox{|cur_cs| is the |eqtb| location of the current control sequence,}\cr + \hbox{\qquad if the current token was a control sequence, + otherwise it's zero.}\cr}}$$ +Underlying this external behavior of |get_next| is all the machinery +necessary to convert from character files to tokens. At a given time we +may be only partially finished with the reading of several files (for +which \.{\\input} was specified), and partially finished with the expansion +of some user-defined macros and/or some macro parameters, and partially +finished with the generation of some text in a template for \.{\\halign}, +and so on. When reading a character file, special characters must be +classified as math delimiters, etc.; comments and extra blank spaces must +be removed, paragraphs must be recognized, and control sequences must be +found in the hash table. Furthermore there are occasions in which the +scanning routines have looked ahead for a word like `\.{plus}' but only +part of that word was found, hence a few characters must be put back +into the input and scanned again. + +To handle these situations, which might all be present simultaneously, +\TeX\ uses various stacks that hold information about the incomplete +activities, and there is a finite state control for each level of the +input mechanism. These stacks record the current state of an implicitly +recursive process, but the |get_next| procedure is not recursive. +Therefore it will not be difficult to translate these algorithms into +low-level languages that do not support recursion. + +@<Glob...@>= +static eight_bits @!cur_cmd; /*current command set by |get_next|*/ +static halfword @!cur_chr; /*operand of current command*/ +static pointer @!cur_cs; /*control sequence found here, zero if none found*/ +static halfword @!cur_tok; /*packed representative of |cur_cmd| and |cur_chr|*/ + +@ The |print_cmd_chr| routine prints a symbolic interpretation of a +command code and its modifier. This is used in certain `\.{You can\'t}' +error messages, and in the implementation of diagnostic routines like +\.{\\show}. + +The body of |print_cmd_chr| is a rather tedious listing of print +commands, and most of it is essentially an inverse to the |primitive| +routine that enters a \TeX\ primitive into |eqtb|. Therefore much of +this procedure appears elsewhere in the program, +together with the corresponding |primitive| calls. + +@d chr_cmd(A) {@+print(A);print_ASCII(chr_code); + } + +@<Declare the procedure called |print_cmd_chr|@>= +static void print_cmd_chr(quarterword @!cmd, halfword @!chr_code) +{@+int n; /*temp variable*/ +switch (cmd) { +case left_brace: chr_cmd("begin-group character ")@;@+break; +case right_brace: chr_cmd("end-group character ")@;@+break; +case math_shift: chr_cmd("math shift character ")@;@+break; +case mac_param: chr_cmd("macro parameter character ")@;@+break; +case sup_mark: chr_cmd("superscript character ")@;@+break; +case sub_mark: chr_cmd("subscript character ")@;@+break; +case endv: print("end of alignment template");@+break; +case spacer: chr_cmd("blank space ")@;@+break; +case letter: chr_cmd("the letter ")@;@+break; +case other_char: chr_cmd("the character ")@;@+break; +@t\4@>@<Cases of |print_cmd_chr| for symbolic printing of primitives@>@/ +default:print("[unknown command code!]"); +} +} + +@ Here is a procedure that displays the current command. + +@p static void show_cur_cmd_chr(void) +{@+int n; /*level of \.{\\if...\\fi} nesting*/ +int @!l; /*line where \.{\\if} started*/ +pointer @!p; +begin_diagnostic();print_nl("{"); +if (mode!=shown_mode) + {@+print_mode(mode);print(": ");shown_mode=mode; + } +print_cmd_chr(cur_cmd, cur_chr); +if (tracing_ifs > 0) + if (cur_cmd >= if_test) if (cur_cmd <= fi_or_else) + {@+print(": "); + if (cur_cmd==fi_or_else) + {@+print_cmd_chr(if_test, cur_if);print_char(' '); + n=0;l=if_line; + } + else{@+n=1;l=line; + } + p=cond_ptr; + while (p!=null) + {@+incr(n);p=link(p); + } + print("(level ");print_int(n);print_char(')');print_if_line(l); + } +print_char('}'); +end_diagnostic(false); +} + +@* Input stacks and states. +This implementation of +\TeX\ uses two different conventions for representing sequential stacks. +@^stack conventions@>@^conventions for representing stacks@> + +\yskip\hangg 1) If there is frequent access to the top entry, and if the +stack is essentially never empty, then the top entry is kept in a global +variable (even better would be a machine register), and the other entries +appear in the array $\\{stack}[0\to(\\{ptr}-1)]$. For example, the +semantic stack described above is handled this way, and so is the input +stack that we are about to study. + +\yskip\hangg 2) If there is infrequent top access, the entire stack contents +are in the array $\\{stack}[0\to(\\{ptr}-1)]$. For example, the |save_stack| +is treated this way, as we have seen. + +\yskip\noindent +The state of \TeX's input mechanism appears in the input stack, whose +entries are records with six fields, called |state|, |index|, |start|, |loc|, +|limit|, and |name|. This stack is maintained with +convention~(1), so it is declared in the following way: + +@<Types...@>= +typedef struct { + quarterword @!state_field, @!index_field; + halfword @!start_field, @!loc_field, @!limit_field, @!name_field; + halfword @!depth_field; + } in_state_record; + +@ @<Glob...@>= +static in_state_record @!input_stack[stack_size+1]; +static int @!input_ptr; /*first unused location of |input_stack|*/ +static int @!max_in_stack; /*largest value of |input_ptr| when pushing*/ +static in_state_record @!cur_input; + /*the ``top'' input state, according to convention (1)*/ + +@ We've already defined the special variable |loc==cur_input.loc_field| +in our discussion of basic input-output routines. The other components of +|cur_input| are defined in the same way: + +@d state cur_input.state_field /*current scanner state*/ +@d index cur_input.index_field /*reference for buffer information*/ +@d start cur_input.start_field /*starting position in |buffer|*/ +@d limit cur_input.limit_field /*end of current line in |buffer|*/ +@d name cur_input.name_field /*name of the current file*/ +@d cur_depth cur_input.depth_field /* nesting depth of current macro */ + +@ Let's look more closely now at the control variables +(|state|,~|index|,~|start|,~|loc|,~|limit|,~|name|), +assuming that \TeX\ is reading a line of characters that have been input +from some file or from the user's terminal. There is an array called +|buffer| that acts as a stack of all lines of characters that are +currently being read from files, including all lines on subsidiary +levels of the input stack that are not yet completed. \TeX\ will return to +the other lines when it is finished with the present input file. + +(Incidentally, on a machine with byte-oriented addressing, it might be +appropriate to combine |buffer| with the |str_pool| array, +letting the buffer entries grow downward from the top of the string pool +and checking that these two tables don't bump into each other.) + +The line we are currently working on begins in position |start| of the +buffer; the next character we are about to read is |buffer[loc]|; and +|limit| is the location of the last character present. If |loc > limit|, +the line has been completely read. Usually |buffer[limit]| is the +|end_line_char|, denoting the end of a line, but this is not +true if the current line is an insertion that was entered on the user's +terminal in response to an error message. + +The |name| variable is a string number that designates the name of +the current file, if we are reading a text file. It is zero if we +are reading from the terminal; it is |n+1| if we are reading from +input stream |n|, where |0 <= n <= 16|. (Input stream 16 stands for +an invalid stream number; in such cases the input is actually from +the terminal, under control of the procedure |read_toks|.) +Finally |18 <= name <= 19| indicates that we are reading a pseudo file +created by the \.{\\scantokens} command. + +The |state| variable has one of three values, when we are scanning such +files: +$$\baselineskip 15pt\vbox{\halign{#\hfil\cr +1) |state==mid_line| is the normal state.\cr +2) |state==skip_blanks| is like |mid_line|, but blanks are ignored.\cr +3) |state==new_line| is the state at the beginning of a line.\cr}}$$ +These state values are assigned numeric codes so that if we add the state +code to the next character's command code, we get distinct values. For +example, `|mid_line+spacer|' stands for the case that a blank +space character occurs in the middle of a line when it is not being +ignored; after this case is processed, the next value of |state| will +be |skip_blanks|. + +@d mid_line 1 /*|state| code when scanning a line of characters*/ +@d skip_blanks (2+max_char_code) /*|state| code when ignoring blanks*/ +@d new_line (3+max_char_code+max_char_code) /*|state| code at start of line*/ + +@ Additional information about the current line is available via the +|index| variable, which counts how many lines of characters are present +in the buffer below the current level. We have |index==0| when reading +from the terminal and prompting the user for each line; then if the user types, +e.g., `\.{\\input paper}', we will have |index==1| while reading +the file \.{paper.tex}. However, it does not follow that |index| is the +same as the input stack pointer, since many of the levels on the input +stack may come from token lists. For example, the instruction `\.{\\input +paper}' might occur in a token list. + +The global variable |in_open| is equal to the |index| +value of the highest non-token-list level. Thus, the number of partially read +lines in the buffer is |in_open+1|, and we have |in_open==index| +when we are not reading a token list. + +If we are not currently reading from the terminal, or from an input +stream, we are reading from the file variable |input_file[index]|. We use +the notation |terminal_input| as a convenient abbreviation for |name==0|, +and |cur_file| as an abbreviation for |input_file[index]|. + +The global variable |line| contains the line number in the topmost +open file, for use in error messages. If we are not reading from +the terminal, |line_stack[index]| holds the line number for the +enclosing level, so that |line| can be restored when the current +file has been read. Line numbers should never be negative, since the +negative of the current line number is used to identify the user's output +routine in the |mode_line| field of the semantic nest entries. + +If more information about the input state is needed, it can be +included in small arrays like those shown here. For example, +the current page or segment number in the input file might be +put into a variable |@!page|, maintained for enclosing levels in +`\ignorespaces|@!page_stack: array[1 dotdot max_in_open]int|\unskip' +by analogy with |line_stack|. +@^system dependencies@> + +@d terminal_input (name==0) /*are we reading from the terminal?*/ +@d cur_file input_file[index] /*the current |alpha_file| variable*/ + +@<Glob...@>= +static int @!in_open; /*the number of lines in the buffer, less one*/ +static int @!open_parens; /*the number of open text files*/ +static alpha_file @!input_file0[max_in_open], + *const @!input_file = @!input_file0-1; +static int @!line; /*current line number in the current source file*/ +static int @!line_stack0[max_in_open], + *const @!line_stack = @!line_stack0-1; + +@ Users of \TeX\ sometimes forget to balance left and right braces properly, +and one of the ways \TeX\ tries to spot such errors is by considering an +input file as broken into subfiles by control sequences that +are declared to be \.{\\outer}. + +A variable called |scanner_status| tells \TeX\ whether or not to complain +when a subfile ends. This variable has six possible values: + +\yskip\hang|normal|, means that a subfile can safely end here without incident. + +\yskip\hang|skipping|, means that a subfile can safely end here, but not a file, +because we're reading past some conditional text that was not selected. + +\yskip\hang|defining|, means that a subfile shouldn't end now because a +macro is being defined. + +\yskip\hang|matching|, means that a subfile shouldn't end now because a +macro is being used and we are searching for the end of its arguments. + +\yskip\hang|aligning|, means that a subfile shouldn't end now because we are +not finished with the preamble of an \.{\\halign} or \.{\\valign}. + +\yskip\hang|absorbing|, means that a subfile shouldn't end now because we are +reading a balanced token list for \.{\\message}, \.{\\write}, etc. + +\yskip\noindent +If the |scanner_status| is not |normal|, the variable |warning_index| points +to the |eqtb| location for the relevant control sequence name to print +in an error message. + +@d skipping 1 /*|scanner_status| when passing conditional text*/ +@d defining 2 /*|scanner_status| when reading a macro definition*/ +@d matching 3 /*|scanner_status| when reading macro arguments*/ +@d aligning 4 /*|scanner_status| when reading an alignment preamble*/ +@d absorbing 5 /*|scanner_status| when reading a balanced text*/ + +@<Glob...@>= +static int @!scanner_status; /*can a subfile end now?*/ +static pointer @!warning_index; /*identifier relevant to non-|normal| scanner status*/ +static pointer @!def_ref; /*reference count of token list being defined*/ + +@ Here is a procedure that uses |scanner_status| to print a warning message +when a subfile has ended, and at certain other crucial times: + +@<Declare the procedure called |runaway|@>= +static void runaway(void) +{@+pointer p; /*head of runaway list*/ +if (scanner_status > skipping) + {@+print_nl("Runaway "); +@.Runaway...@> + switch (scanner_status) { + case defining: {@+print("definition");p=def_ref; + } @+break; + case matching: {@+print("argument");p=temp_head; + } @+break; + case aligning: {@+print("preamble");p=hold_head; + } @+break; + case absorbing: {@+print("text");p=def_ref; + } + } /*there are no other cases*/ + print_char('?');print_ln();show_token_list(link(p), null, error_line-10); + } +} + +@ However, all this discussion about input state really applies only to the +case that we are inputting from a file. There is another important case, +namely when we are currently getting input from a token list. In this case +|state==token_list|, and the conventions about the other state variables +are different: + +\yskip\hang|loc| is a pointer to the current node in the token list, i.e., +the node that will be read next. If |loc==null|, the token list has been +fully read. + +\yskip\hang|start| points to the first node of the token list; this node +may or may not contain a reference count, depending on the type of token +list involved. + +\yskip\hang|token_type|, which takes the place of |index| in the +discussion above, is a code number that explains what kind of token list +is being scanned. + +\yskip\hang|name| points to the |eqtb| address of the control sequence +being expanded, if the current token list is a macro. + +\yskip\hang|param_start|, which takes the place of |limit|, tells where +the parameters of the current macro begin in the |param_stack|, if the +current token list is a macro. + +\yskip\noindent The |token_type| can take several values, depending on +where the current token list came from: + +\yskip\hang|parameter|, if a parameter is being scanned; + +\hang|u_template|, if the \<u_j> part of an alignment +template is being scanned; + +\hang|v_template|, if the \<v_j> part of an alignment +template is being scanned; + +\hang|backed_up|, if the token list being scanned has been inserted as +`to be read again'; + +\hang|inserted|, if the token list being scanned has been inserted as +the text expansion of a \.{\\count} or similar variable; + +\hang|macro|, if a user-defined control sequence is being scanned; + +\hang|output_text|, if an \.{\\output} routine is being scanned; + +\hang|every_par_text|, if the text of \.{\\everypar} is being scanned; + +\hang|every_math_text|, if the text of \.{\\everymath} is being scanned; + +\hang|every_display_text|, if the text of \.{\\everydisplay} is being scanned; + +\hang|every_hbox_text|, if the text of \.{\\everyhbox} is being scanned; + +\hang|every_vbox_text|, if the text of \.{\\everyvbox} is being scanned; + +\hang|every_job_text|, if the text of \.{\\everyjob} is being scanned; + +\hang|every_cr_text|, if the text of \.{\\everycr} is being scanned; + +\hang|mark_text|, if the text of a \.{\\mark} is being scanned; + +\hang|write_text|, if the text of a \.{\\write} is being scanned. + +\yskip\noindent +The codes for |output_text|, |every_par_text|, etc., are equal to a constant +plus the corresponding codes for token list parameters |output_routine_loc|, +|every_par_loc|, etc. The token list begins with a reference count if and +only if |token_type >= macro|. +@^reference counts@> + +Since \eTeX's additional token list parameters precede |toks_base|, the +corresponding token types must precede |write_text|. + +@d token_list 0 /*|state| code when scanning a token list*/ +@d token_type index /*type of current token list*/ +@d param_start limit /*base of macro parameters in |param_stack|*/ +@d parameter 0 /*|token_type| code for parameter*/ +@d u_template 1 /*|token_type| code for \<u_j> template*/ +@d v_template 2 /*|token_type| code for \<v_j> template*/ +@d backed_up 3 /*|token_type| code for text to be reread*/ +@d inserted 4 /*|token_type| code for inserted texts*/ +@d macro 5 /*|token_type| code for defined control sequences*/ +@d output_text 6 /*|token_type| code for output routines*/ +@d every_par_text 7 /*|token_type| code for \.{\\everypar}*/ +@d every_math_text 8 /*|token_type| code for \.{\\everymath}*/ +@d every_display_text 9 /*|token_type| code for \.{\\everydisplay}*/ +@d every_hbox_text 10 /*|token_type| code for \.{\\everyhbox}*/ +@d every_vbox_text 11 /*|token_type| code for \.{\\everyvbox}*/ +@d every_job_text 12 /*|token_type| code for \.{\\everyjob}*/ +@d every_cr_text 13 /*|token_type| code for \.{\\everycr}*/ +@d mark_text 14 /*|token_type| code for \.{\\topmark}, etc.*/ +@# +@d eTeX_text_offset (output_routine_loc-output_text) +@d every_eof_text (every_eof_loc-eTeX_text_offset) + /*|token_type| code for \.{\\everyeof}*/ +@# +@d write_text (toks_base-eTeX_text_offset) /*|token_type| code for \.{\\write}*/ + +@ The |param_stack| is an auxiliary array used to hold pointers to the token +lists for parameters at the current level and subsidiary levels of input. +This stack is maintained with convention (2), and it grows at a different +rate from the others. + +@<Glob...@>= +static pointer @!param_stack[param_size+1]; + /*token list pointers for parameters*/ +static int @!param_ptr; /*first unused entry in |param_stack|*/ +static int @!max_param_stack; + /*largest value of |param_ptr|, will be | <= param_size+9|*/ + +@ The input routines must also interact with the processing of +\.{\\halign} and \.{\\valign}, since the appearance of tab marks and +\.{\\cr} in certain places is supposed to trigger the beginning of special +\<v_j> template text in the scanner. This magic is accomplished by an +|align_state| variable that is increased by~1 when a `\.{\char'173}' is +scanned and decreased by~1 when a `\.{\char'175}' is scanned. The |align_state| +is nonzero during the \<u_j> template, after which it is set to zero; the +\<v_j> template begins when a tab mark or \.{\\cr} occurs at a time that +|align_state==0|. + +The same principle applies when entering the definition of a +control sequence between \.{\\csname} and \.{\\endcsname}. + +@<Glob...@>= +static int @!align_state; /*group level with respect to current alignment*/ +static int @!incsname_state; /*group level with respect to in csname state*/ + +@ Thus, the ``current input state'' can be very complicated indeed; there +can be many levels and each level can arise in a variety of ways. The +|show_context| procedure, which is used by \TeX's error-reporting routine to +print out the current input state on all levels down to the most recent +line of characters from an input file, illustrates most of these conventions. +The global variable |base_ptr| contains the lowest level that was +displayed by this procedure. + +@<Glob...@>= +static int @!base_ptr; /*shallowest level shown by |show_context|*/ + +@ The status at each level is indicated by printing two lines, where the first +line indicates what was read so far and the second line shows what remains +to be read. The context is cropped, if necessary, so that the first line +contains at most |half_error_line| characters, and the second contains +at most |error_line|. Non-current input levels whose |token_type| is +`|backed_up|' are shown only if they have not been fully read. + +@p static void show_context(void) /*prints where the scanner is*/ +{@+ +int old_setting; /*saved |selector| setting*/ +int @!nn; /*number of contexts shown so far, less one*/ +bool @!bottom_line; /*have we reached the final context to be shown?*/ +@<Local variables for formatting calculations@>@/ +base_ptr=input_ptr;input_stack[base_ptr]=cur_input; + /*store current state*/ +nn=-1;bottom_line=false; +loop@+{@+cur_input=input_stack[base_ptr]; /*enter into the context*/ + if ((state!=token_list)) + if ((name > 19)||(base_ptr==0)) bottom_line=true; + if ((base_ptr==input_ptr)||bottom_line||(nn < error_context_lines)) + @<Display the current context@>@; + else if (nn==error_context_lines) + {@+print_nl("...");incr(nn); /*omitted if |error_context_lines < 0|*/ + } + if (bottom_line) goto done; + decr(base_ptr); + } +done: cur_input=input_stack[input_ptr]; /*restore original state*/ +} + +@ @<Display the current context@>= +{@+if ((base_ptr==input_ptr)||(state!=token_list)|| + (token_type!=backed_up)||(loc!=null)) + /*we omit backed-up token lists that have already been read*/ + {@+tally=0; /*get ready to count characters*/ + old_setting=selector; + if (state!=token_list) + {@+@<Print location of current line@>; + @<Pseudoprint the line@>; + } + else{@+@<Print type of token list@>; + @<Pseudoprint the token list@>; + } + selector=old_setting; /*stop pseudoprinting*/ + @<Print two lines using the tricky pseudoprinted information@>; + incr(nn); + } +} + +@ This routine should be changed, if necessary, to give the best possible +indication of where the current line resides in the input file. +For example, on some systems it is best to print both a page and line number. +@^system dependencies@> + +@<Print location of current line@>= +if (name <= 17) + if (terminal_input) + if (base_ptr==0) print_nl("<*>");else print_nl("<insert> "); + else{@+print_nl("<read "); + if (name==17) print_char('*');@+else print_int(name-1); +@.*\relax@> + print_char('>'); + } +else{@+print_nl("l."); + if (index==in_open) print_int(line); + else print_int(line_stack[index+1]); /*input from a pseudo file*/ + } +print_char(' ') + +@ @<Print type of token list@>= +switch (token_type) { +case parameter: print_nl("<argument> ");@+break; +case u_template: case v_template: print_nl("<template> ");@+break; +case backed_up: if (loc==null) print_nl("<recently read> "); + else print_nl("<to be read again> ");@+break; +case inserted: print_nl("<inserted text> ");@+break; +case macro: {@+print_ln();print_cs(name); + } @+break; +case output_text: print_nl("<output> ");@+break; +case every_par_text: print_nl("<everypar> ");@+break; +case every_math_text: print_nl("<everymath> ");@+break; +case every_display_text: print_nl("<everydisplay> ");@+break; +case every_hbox_text: print_nl("<everyhbox> ");@+break; +case every_vbox_text: print_nl("<everyvbox> ");@+break; +case every_job_text: print_nl("<everyjob> ");@+break; +case every_cr_text: print_nl("<everycr> ");@+break; +case mark_text: print_nl("<mark> ");@+break; +case every_eof_text: print_nl("<everyeof> ");@+break; +case write_text: print_nl("<write> ");@+break; +default:print_nl("?"); /*this should never happen*/ +} + +@ Here it is necessary to explain a little trick. We don't want to store a long +string that corresponds to a token list, because that string might take up +lots of memory; and we are printing during a time when an error message is +being given, so we dare not do anything that might overflow one of \TeX's +tables. So `pseudoprinting' is the answer: We enter a mode of printing +that stores characters into a buffer of length |error_line|, where character +$k+1$ is placed into \hbox{|trick_buf[k%error_line]|} if +|k < trick_count|, otherwise character |k| is dropped. Initially we set +|tally=0| and |trick_count=1000000|; then when we reach the +point where transition from line 1 to line 2 should occur, we +set |first_count=tally| and |trick_count=@tmax@>(error_line, +tally+1+error_line-half_error_line)|. At the end of the +pseudoprinting, the values of |first_count|, |tally|, and +|trick_count| give us all the information we need to print the two lines, +and all of the necessary text is in |trick_buf|. + +Namely, let |l| be the length of the descriptive information that appears +on the first line. The length of the context information gathered for that +line is |k==first_count|, and the length of the context information +gathered for line~2 is $m=\min(|tally|, |trick_count|)-k$. If |l+k <= h|, +where |h==half_error_line|, we print |trick_buf[0 dotdot k-1]| after the +descriptive information on line~1, and set |n=l+k|; here |n| is the +length of line~1. If $l+k>h$, some cropping is necessary, so we set |n=h| +and print `\.{...}' followed by +$$\hbox{|trick_buf[(l+k-h+3)dotdot k-1]|,}$$ +where subscripts of |trick_buf| are circular modulo |error_line|. The +second line consists of |n|~spaces followed by |trick_buf[k dotdot(k+m-1)]|, +unless |n+m > error_line|; in the latter case, further cropping is done. +This is easier to program than to explain. + +@<Local variables for formatting...@>= +int @!i; /*index into |buffer|*/ +int @!j; /*end of current line in |buffer|*/ +int @!l; /*length of descriptive information on line 1*/ +int @!m; /*context information gathered for line 2*/ +int @!n; /*length of line 1*/ +int @!p; /*starting or ending place in |trick_buf|*/ +int @!q; /*temporary index*/ + +@ The following code sets up the print routines so that they will gather +the desired information. + +@d begin_pseudoprint + {@+l=tally;tally=0;selector=pseudo; + trick_count=1000000; + } +@d set_trick_count + {@+first_count=tally; + trick_count=tally+1+error_line-half_error_line; + if (trick_count < error_line) trick_count=error_line; + } + +@ And the following code uses the information after it has been gathered. + +@<Print two lines using the tricky pseudoprinted information@>= +if (trick_count==1000000) set_trick_count; + /*|set_trick_count| must be performed*/ +if (tally < trick_count) m=tally-first_count; +else m=trick_count-first_count; /*context on line 2*/ +if (l+first_count <= half_error_line) + {@+p=0;n=l+first_count; + } +else{@+print("...");p=l+first_count-half_error_line+3; + n=half_error_line; + } +for (q=p; q<=first_count-1; q++) print_char(trick_buf[q%error_line]); +print_ln(); +for (q=1; q<=n; q++) print_char(' '); /*print |n| spaces to begin line~2*/ +if (m+n <= error_line) p=first_count+m;else p=first_count+(error_line-n-3); +for (q=first_count; q<=p-1; q++) print_char(trick_buf[q%error_line]); +if (m+n > error_line) print("...") + +@ But the trick is distracting us from our current goal, which is to +understand the input state. So let's concentrate on the data structures that +are being pseudoprinted as we finish up the |show_context| procedure. + +@<Pseudoprint the line@>= +begin_pseudoprint; +if (buffer[limit]==end_line_char) j=limit; +else j=limit+1; /*determine the effective end of the line*/ +if (j > 0) for (i=start; i<=j-1; i++) + {@+if (i==loc) set_trick_count; + printn(buffer[i]); + } + +@ @<Pseudoprint the token list@>= +begin_pseudoprint; +if (token_type < macro) show_token_list(start, loc, 100000); +else show_token_list(link(start), loc, 100000) /*avoid reference count*/ + +@ Here is the missing piece of |show_token_list| that is activated when the +token beginning line~2 is about to be shown: + +@<Do magic computation@>=set_trick_count + +@* Maintaining the input stacks. +The following subroutines change the input status in commonly needed ways. + +First comes |push_input|, which stores the current state and creates a +new level (having, initially, the same properties as the old). + +@d push_input @t@> /*enter a new input level, save the old*/ + {@+if (input_ptr > max_in_stack) + {@+max_in_stack=input_ptr; + if (input_ptr==stack_size) overflow("input stack size", stack_size); +@:TeX capacity exceeded input stack size}{\quad input stack size@> + } + input_stack[input_ptr]=cur_input; /*stack the record*/ + incr(input_ptr); + } + +@ And of course what goes up must come down. + +@d pop_input @t@> /*leave an input level, re-enter the old*/ + {@+decr(input_ptr);cur_input=input_stack[input_ptr]; + } + +@ Here is a procedure that starts a new level of token-list input, given +a token list |p| and its type |t|. If |t==macro|, the calling routine should +set |name| and |loc|. + +@d back_list(A) begin_token_list(A, backed_up) /*backs up a simple token list*/ +@d ins_list(A) begin_token_list(A, inserted) /*inserts a simple token list*/ + +@p static void begin_token_list(pointer @!p, quarterword @!t) +{@+push_input;state=token_list;start=p;token_type=t; +if (t >= macro) /*the token list starts with a reference count*/ + {@+add_token_ref(p); + if (t==macro) param_start=param_ptr; + else{@+ + @<additional local variables for |begin_token_list|@> + loc=link(p); + if (tracing_macros > 1) + {@+begin_diagnostic();print_nl(""); + switch (t) { + case mark_text: print_esc("mark");@+break; + case write_text: print_esc("write");@+break; + default:print_cmd_chr(assign_toks, t-output_text+output_routine_loc); + } @/ + print("->");token_show(p);end_diagnostic(false); + } + @<update the macro stack@>@; + } + } +else loc=p; +} + +@ When a token list has been fully scanned, the following computations +should be done as we leave that level of input. The |token_type| tends +to be equal to either |backed_up| or |inserted| about 2/3 of the time. +@^inner loop@> + +@p static void end_token_list(void) /*leave a token-list input level*/ +{@+if (token_type >= backed_up) /*token list to be deleted*/ + {@+if (token_type <= inserted) flush_list(start); + else{@+delete_token_ref(start); /*update reference count*/ + if (token_type==macro) /*parameters must be flushed*/ + while (param_ptr > param_start) + {@+decr(param_ptr); + flush_list(param_stack[param_ptr]); + } + } + } +else if (token_type==u_template) + if (align_state > 500000) align_state=0; + else fatal_error("(interwoven alignment preambles are not allowed)"); +@.interwoven alignment preambles...@> +pop_input; +check_interrupt; +} + +@ Sometimes \TeX\ has read too far and wants to ``unscan'' what it has +seen. The |back_input| procedure takes care of this by putting the token +just scanned back into the input stream, ready to be read again. This +procedure can be used only if |cur_tok| represents the token to be +replaced. Some applications of \TeX\ use this procedure a lot, +so it has been slightly optimized for speed. +@^inner loop@> + +We charge the backup token to the current file and line. +@^profiling@> + +@p static void back_input(void) /*undoes one token of input*/ +{@+pointer p; /*a token list of length one*/ +while ((state==token_list)&&(loc==null)&&(token_type!=v_template)) + end_token_list(); /*conserve stack space*/ +p=get_avail();info(p)=cur_tok; fl_mem[p]=prof_file_line; +if (cur_tok < right_brace_limit) + if (cur_tok < left_brace_limit) decr(align_state); + else incr(align_state); +push_input;state=token_list;start=p;token_type=backed_up; +loc=p; /*that was |back_list(p)|, without procedure overhead*/ +} + +@ @<Insert token |p| into \TeX's input@>= +{@+t=cur_tok;cur_tok=p; +if (a) + {@+p=get_avail();info(p)=cur_tok;link(p)=loc;loc=p;start=p; + if (cur_tok < right_brace_limit) + if (cur_tok < left_brace_limit) decr(align_state); + else incr(align_state); + } +else{@+back_input();a=eTeX_ex; + } +cur_tok=t; +} + +@ The |back_error| routine is used when we want to replace an offending token +just before issuing an error message. This routine, like |back_input|, +requires that |cur_tok| has been set. We disable interrupts during the +call of |back_input| so that the help message won't be lost. + +@p static void back_error(void) /*back up one token and call |error|*/ +{@+OK_to_interrupt=false;back_input();OK_to_interrupt=true;error(); +} +@# +static void ins_error(void) /*back up one inserted token and call |error|*/ +{@+OK_to_interrupt=false;back_input();token_type=inserted; +OK_to_interrupt=true;error(); +} + +@ The |begin_file_reading| procedure starts a new level of input for lines +of characters to be read from a file, or as an insertion from the +terminal. It does not take care of opening the file, nor does it set |loc| +or |limit| or |line|. +@^system dependencies@> + +@p static void begin_file_reading(void) +{@+if (in_open==max_in_open) overflow("text input levels", max_in_open); +@:TeX capacity exceeded text input levels}{\quad text input levels@> +if (first==buf_size) overflow("buffer size", buf_size); +@:TeX capacity exceeded buffer size}{\quad buffer size@> +incr(in_open);push_input;index=in_open;@/ +source_filename_stack[index]=NULL; /* \TeX\ Live */ +full_source_filename_stack[index]=NULL; /* \TeX\ Live */ +eof_seen[index]=false; +grp_stack[index]=cur_boundary;if_stack[index]=cond_ptr; +line_stack[index]=line;start=first;state=mid_line; +name=0; /*|terminal_input| is now |true|*/ +cur_file_num=terminal_file; +} + +@ Conversely, the variables must be downdated when such a level of input +is finished: + +@p static void end_file_reading(void) +{@+first=start;line=line_stack[index]; +if ((name==18)||(name==19)) pseudo_close();else +if (name > 17) a_close(&cur_file); /*forget it*/ +if (full_source_filename_stack[in_open]!=NULL) +{ free(full_source_filename_stack[in_open]); + full_source_filename_stack[in_open]=NULL; +} +pop_input;decr(in_open); +} + +@ In order to keep the stack from overflowing during a long sequence of +inserted `\.{\\show}' commands, the following routine removes completed +error-inserted lines from memory. + +@p static void clear_for_error_prompt(void) +{@+while ((state!=token_list)&&terminal_input&&@| + (input_ptr > 0)&&(loc > limit)) end_file_reading(); +print_ln();clear_terminal; +} + +@ To get \TeX's whole input mechanism going, we perform the following +actions. + +@<Initialize the input routines@>= +{@+input_ptr=0;max_in_stack=0; +in_open=0;open_parens=0;max_buf_stack=0; +grp_stack[0]=0;if_stack[0]=null; +param_ptr=0;max_param_stack=0; +first=buf_size;@/do@+{buffer[first]=0;decr(first);}@+ while (!(first==0)); +scanner_status=normal;warning_index=null;first=1; +state=new_line;start=1;index=0;line=0;name=0;cur_depth=0; +force_eof=false; +align_state=1000000;@/ +if (!init_terminal()) exit(0); +limit=last;first=last+1; /*|init_terminal| has set |loc| and |last|*/ +} + +@* Getting the next token. +The heart of \TeX's input mechanism is the |get_next| procedure, which +we shall develop in the next few sections of the program. Perhaps we +shouldn't actually call it the ``heart,'' however, because it really acts +as \TeX's eyes and mouth, reading the source files and gobbling them up. +And it also helps \TeX\ to regurgitate stored token lists that are to be +processed again. +@^eyes and mouth@> + +The main duty of |get_next| is to input one token and to set |cur_cmd| +and |cur_chr| to that token's command code and modifier. Furthermore, if +the input token is a control sequence, the |eqtb| location of that control +sequence is stored in |cur_cs|; otherwise |cur_cs| is set to zero. + +Underlying this simple description is a certain amount of complexity +because of all the cases that need to be handled. +However, the inner loop of |get_next| is reasonably short and fast. + +When |get_next| is asked to get the next token of a \.{\\read} line, +it sets |cur_cmd==cur_chr==cur_cs==0| in the case that no more tokens +appear on that line. (There might not be any tokens at all, if the +|end_line_char| has |ignore| as its catcode.) + +@ The value of |par_loc| is the |eqtb| address of `\.{\\par}'. This quantity +is needed because a blank line of input is supposed to be exactly equivalent +to the appearance of \.{\\par}; we must set |cur_cs:=par_loc| +when detecting a blank line. + +The same is true for the input, for the warning message, since input +is expected by default before every scanning and hence setting of +|cur_cs|. + +@<Glob...@>= +static pointer @!par_loc; /*location of `\.{\\par}' in |eqtb|*/ +static halfword @!par_token; /*token representing `\.{\\par}'*/ +static pointer @!input_loc; /*location of `\.{\\input}' in |eqtb|*/ +static halfword @!input_token; /*token representing `\.{\\input}'*/ + +@ @<Put each...@>= +primitive("par", par_end, 256); /*cf.\ |scan_file_name|*/ +@!@:par\_}{\.{\\par} primitive@> +par_loc=cur_val;par_token=cs_token_flag+par_loc; + +@ @<Cases of |print_cmd_chr|...@>= +case par_end: print_esc("par");@+break; + +@ Before getting into |get_next|, let's consider the subroutine that +is called when an `\.{\\outer}' control sequence has been scanned or +when the end of a file has been reached. These two cases are distinguished +by |cur_cs|, which is zero at the end of a file. + +@p static void check_outer_validity(void) +{@+pointer p; /*points to inserted token list*/ +pointer @!q; /*auxiliary pointer*/ +if (scanner_status!=normal) + {@+deletions_allowed=false; + @<Back up an outer control sequence so that it can be reread@>; + if (scanner_status > skipping) + @<Tell the user what has run away and try to recover@>@; + else{@+print_err("Incomplete ");print_cmd_chr(if_test, cur_if); +@.Incomplete \\if...@> + print("; all text was ignored after line ");print_int(skip_line); + help3("A forbidden control sequence occurred in skipped text.",@/ + "This kind of error happens when you say `\\if...' and forget",@/ + "the matching `\\fi'. I've inserted a `\\fi'; this might work."); + if (cur_cs!=0) cur_cs=0; + else help_line[2]=@| + "The file ended while I was skipping conditional text."; + cur_tok=cs_token_flag+frozen_fi;ins_error(); + } + deletions_allowed=true; + } +} + +@ An outer control sequence that occurs in a \.{\\read} will not be reread, +since the error recovery for \.{\\read} is not very powerful. + +@<Back up an outer control sequence so that it can be reread@>= +if (cur_cs!=0) + {@+if ((state==token_list)||(name < 1)||(name > 17)) + {@+p=get_avail();info(p)=cs_token_flag+cur_cs; + back_list(p); /*prepare to read the control sequence again*/ + } + cur_cmd=spacer;cur_chr=' '; /*replace it by a space*/ + } + +@ @<Tell the user what has run away...@>= +{@+runaway(); /*print a definition, argument, or preamble*/ +if (cur_cs==0) print_err("File ended"); +@.File ended while scanning...@> +else{@+cur_cs=0;print_err("Forbidden control sequence found"); +@.Forbidden control sequence...@> + } +print(" while scanning "); +@<Print either `\.{definition}' or `\.{use}' or `\.{preamble}' or `\.{text}', +and insert tokens that should lead to recovery@>; +print(" of ");sprint_cs(warning_index); +help4("I suspect you have forgotten a `}', causing me",@/ +"to read past where you wanted me to stop.",@/ +"I'll try to recover; but if the error is serious,",@/ +"you'd better type `E' or `X' now and fix your file.");@/ +error(); +} + +@ The recovery procedure can't be fully understood without knowing more +about the \TeX\ routines that should be aborted, but we can sketch the +ideas here: For a runaway definition or a runaway balanced text +we will insert a right brace; for a +runaway preamble, we will insert a special \.{\\cr} token and a right +brace; and for a runaway argument, we will set |long_state| to +|outer_call| and insert \.{\\par}. + +@<Print either `\.{definition}' or...@>= +p=get_avail(); +switch (scanner_status) { +case defining: {@+print("definition");info(p)=right_brace_token+'}'; + } @+break; +case matching: {@+print("use");info(p)=par_token;long_state=outer_call; + } @+break; +case aligning: {@+print("preamble");info(p)=right_brace_token+'}';q=p; + p=get_avail();link(p)=q;info(p)=cs_token_flag+frozen_cr; + align_state=-1000000; + } @+break; +case absorbing: {@+print("text");info(p)=right_brace_token+'}'; + } +} /*there are no other cases*/ +ins_list(p) + +@ We need to mention a procedure here that may be called by |get_next|. + +@p static void firm_up_the_line(void); + +@ Now we're ready to take the plunge into |get_next| itself. Parts of +this routine are executed more often than any other instructions of \TeX. +@^mastication@>@^inner loop@> + +@p static void get_next(void) /*sets |cur_cmd|, |cur_chr|, |cur_cs| to next token*/ +{@+ /*go here to get the next input token*/ + /*go here to eat the next character from a file*/ + /*go here to digest it again*/ + /*go here to start looking for a control sequence*/ + /*go here when a control sequence has been found*/ + /*go here when the next input token has been got*/ +int k; /*an index into |buffer|*/ +halfword @!t; /*a token*/ +int @!cat; /*|cat_code(cur_chr)|, usually*/ +ASCII_code @!c, @!cc; /*constituents of a possible expanded code*/ +int @!d; /*number of excess characters in an expanded code*/ +restart: cur_cs=0; +if (state!=token_list) +@<Input from external file, |goto restart| if no input found@>@; +else@<Input from token list, |goto restart| if end of list or if a parameter +needs to be expanded@>; +@<If an alignment entry has just ended, take appropriate action@>; +} + +@ An alignment entry ends when a tab or \.{\\cr} occurs, provided that the +current level of braces is the same as the level that was present at the +beginning of that alignment entry; i.e., provided that |align_state| has +returned to the value it had after the \<u_j> template for that entry. +@^inner loop@> + +@<If an alignment entry has just ended, take appropriate action@>= +if (cur_cmd <= car_ret) if (cur_cmd >= tab_mark) if (align_state==0) + @<Insert the \(v)\<v_j> template and |goto restart|@>@; + +@ @<Input from external file, |goto restart| if no input found@>= +@^inner loop@> +{@+get_cur_chr: if (loc <= limit) /*current line not yet finished*/ + {@+cur_chr=buffer[loc];incr(loc); + @<Set |cur_file_line| based on the information in |cur_input|@>@; + reswitch: cur_cmd=cat_code(cur_chr); + @<Change state if necessary, and |goto get_cur_chr| if the current character +should be ignored, or |goto reswitch| if the current character changes to +another@>; + } +else{@+state=new_line;@/ + @<Move to next line of file, or |goto restart| if there is no next line, +or |return| if a \.{\\read} line has finished@>; + check_interrupt; + goto get_cur_chr; + } +} + +@ The following 48-way switch accomplishes the scanning quickly, assuming +that a decent \PASCAL\ compiler has translated the code. Note that the numeric +values for |mid_line|, |skip_blanks|, and |new_line| are spaced +apart from each other by |max_char_code+1|, so we can add a character's +command code to the state to get a single number that characterizes both. + +@d any_state_plus(A) case mid_line+A: + case skip_blanks+A: case new_line+A + +@<Change state if necessary...@>= +switch (state+cur_cmd) { +@<Cases where character is ignored@>: goto get_cur_chr; +any_state_plus(escape): @<Scan a control sequence and set |state:=skip_blanks| +or |mid_line|@>@;@+break; +any_state_plus(active_char): @<Process an active-character control sequence +and set |state:=mid_line|@>@;@+break; +any_state_plus(sup_mark): @<If this |sup_mark| starts an expanded character +like~\.{\^\^A} or~\.{\^\^df}, then |goto reswitch|, otherwise set |state:=mid_line|@>@;@+break; +any_state_plus(invalid_char): @<Decry the invalid character and |goto restart|@>@; +@t\4@>@<Handle situations involving spaces, braces, changes of state@>@; +default:do_nothing; +} + +@ @<Cases where character is ignored@>= +any_state_plus(ignore): case skip_blanks+spacer: + case new_line+spacer + +@ We go to |restart| instead of to |get_cur_chr|, because |state| might equal +|token_list| after the error has been dealt with +(cf.\ |clear_for_error_prompt|). + +@<Decry the invalid...@>= +{@+print_err("Text line contains an invalid character"); +@.Text line contains...@> +help2("A funny symbol that I can't read has just been input.",@/ +"Continue, and I'll forget that it ever happened.");@/ +deletions_allowed=false;error();deletions_allowed=true; +goto restart; +} + +@ @d add_delims_to(A) A+math_shift: A+tab_mark: A+mac_param: + A+sub_mark: A+letter: A+other_char + +@<Handle situations involving spaces, braces, changes of state@>= +case mid_line+spacer: @<Enter |skip_blanks| state, emit a space@>@;@+break; +case mid_line+car_ret: @<Finish line, emit a space@>@;@+break; +case skip_blanks+car_ret: any_state_plus(comment): + @<Finish line, |goto switch|@>@; +case new_line+car_ret: @<Finish line, emit a \.{\\par}@>@;@+break; +case mid_line+left_brace: incr(align_state);@+break; +case skip_blanks+left_brace: case new_line+left_brace: {@+ + state=mid_line;incr(align_state); + } @+break; +case mid_line+right_brace: decr(align_state);@+break; +case skip_blanks+right_brace: case new_line+right_brace: {@+ + state=mid_line;decr(align_state); + } @+break; +add_delims_to(case skip_blanks): add_delims_to( + case new_line): state=mid_line;@+break; + +@ When a character of type |spacer| gets through, its character code is +changed to $\.{"\ "}=040$. This means that the ASCII codes for tab and space, +and for the space inserted at the end of a line, will +be treated alike when macro parameters are being matched. We do this +since such characters are indistinguishable on most computer terminal displays. + +@<Finish line, emit a space@>= +{@+loc=limit+1;cur_cmd=spacer;cur_chr=' '; +} + +@ The following code is performed only when |cur_cmd==spacer|. + +@<Enter |skip_blanks| state, emit a space@>= +{@+state=skip_blanks;cur_chr=' '; +} + +@ @<Finish line, |goto switch|@>= +{@+loc=limit+1;goto get_cur_chr; +} + +@ @<Finish line, emit a \.{\\par}@>= +{@+loc=limit+1;cur_cs=par_loc;cur_cmd=eq_type(cur_cs); +cur_chr=equiv(cur_cs); +if (cur_cmd >= outer_call) check_outer_validity(); +} + +@ Notice that a code like \.{\^\^8} becomes \.x if not followed by a hex digit. + +@d is_hex(A) (((A >= '0')&&(A <= '9'))||((A >= 'a')&&(A <= 'f'))) +@d hex_to_cur_chr + if (c <= '9') cur_chr=c-'0';@+else cur_chr=c-'a'+10; + if (cc <= '9') cur_chr=16*cur_chr+cc-'0'; + else cur_chr=16*cur_chr+cc-'a'+10 + +@<If this |sup_mark| starts an expanded character...@>= +{@+if (cur_chr==buffer[loc]) if (loc < limit) + {@+c=buffer[loc+1];@+if (c < 0200) /*yes we have an expanded char*/ + {@+loc=loc+2; + if (is_hex(c)) if (loc <= limit) + {@+cc=buffer[loc];@+if (is_hex(cc)) + {@+incr(loc);hex_to_cur_chr;goto reswitch; + } + } + if (c < 0100) cur_chr=c+0100;@+else cur_chr=c-0100; + goto reswitch; + } + } +state=mid_line; +} + +@ @<Process an active-character...@>= +{@+cur_cs=cur_chr+active_base; +cur_cmd=eq_type(cur_cs);cur_chr=equiv(cur_cs);state=mid_line; +if (cur_cmd >= outer_call) check_outer_validity(); +} + +@ Control sequence names are scanned only when they appear in some line of +a file; once they have been scanned the first time, their |eqtb| location +serves as a unique identification, so \TeX\ doesn't need to refer to the +original name any more except when it prints the equivalent in symbolic form. + +The program that scans a control sequence has been written carefully +in order to avoid the blowups that might otherwise occur if a malicious +user tried something like `\.{\\catcode\'15=0}'. The algorithm might +look at |buffer[limit+1]|, but it never looks at |buffer[limit+2]|. + +If expanded characters like `\.{\^\^A}' or `\.{\^\^df}' +appear in or just following +a control sequence name, they are converted to single characters in the +buffer and the process is repeated, slowly but surely. + +@<Scan a control...@>= +{@+if (loc > limit) cur_cs=null_cs; /*|state| is irrelevant in this case*/ +else{@+start_cs: k=loc;cur_chr=buffer[k];cat=cat_code(cur_chr); + incr(k); + if (cat==letter) state=skip_blanks; + else if (cat==spacer) state=skip_blanks; + else state=mid_line; + if ((cat==letter)&&(k <= limit)) + @<Scan ahead in the buffer until finding a nonletter; if an expanded code +is encountered, reduce it and |goto start_cs|; otherwise if a multiletter +control sequence is found, adjust |cur_cs| and |loc|, and |goto found|@>@; + else@<If an expanded code is present, reduce it and |goto start_cs|@>; + cur_cs=single_base+buffer[loc];incr(loc); + } +found: cur_cmd=eq_type(cur_cs);cur_chr=equiv(cur_cs); +if (cur_cmd >= outer_call) check_outer_validity(); +} + +@ Whenever we reach the following piece of code, we will have +|cur_chr==buffer[k-1]| and |k <= limit+1| and |cat==cat_code(cur_chr)|. If an +expanded code like \.{\^\^A} or \.{\^\^df} appears in |buffer[(k-1)dotdot(k+1)]| +or |buffer[(k-1)dotdot(k+2)]|, we +will store the corresponding code in |buffer[k-1]| and shift the rest of +the buffer left two or three places. + +@<If an expanded...@>= +{@+if (buffer[k]==cur_chr) @+if (cat==sup_mark) @+if (k < limit) + {@+c=buffer[k+1];@+if (c < 0200) /*yes, one is indeed present*/ + {@+d=2; + if (is_hex(c)) @+if (k+2 <= limit) + {@+cc=buffer[k+2];@+if (is_hex(cc)) incr(d); + } + if (d > 2) + {@+hex_to_cur_chr;buffer[k-1]=cur_chr; + } + else if (c < 0100) buffer[k-1]=c+0100; + else buffer[k-1]=c-0100; + limit=limit-d;first=first-d; + while (k <= limit) + {@+buffer[k]=buffer[k+d];incr(k); + } + goto start_cs; + } + } +} + +@ @<Scan ahead in the buffer...@>= +{@+@/do@+{cur_chr=buffer[k];cat=cat_code(cur_chr);incr(k); +}@+ while (!((cat!=letter)||(k > limit))); +@<If an expanded...@>; +if (cat!=letter) decr(k); + /*now |k| points to first nonletter*/ +if (k > loc+1) /*multiletter control sequence has been scanned*/ + {@+cur_cs=id_lookup(loc, k-loc);loc=k;goto found; + } +} + +@ Let's consider now what happens when |get_next| is looking at a token list. +We restore the file and line information. +@^profiling@> + +@<Input from token list, |goto restart| if end of list or if a parameter needs +to be expanded@>= +if (loc!=null) /*list not exhausted*/ +@^inner loop@> + {@+t=info(loc); cur_file_line=fl_mem[loc]; + loc=link(loc); /*move to next*/ + if (t >= cs_token_flag) /*a control sequence token*/ + {@+cur_cs=t-cs_token_flag; + cur_cmd=eq_type(cur_cs);cur_chr=equiv(cur_cs); + if (cur_cmd >= outer_call) + if (cur_cmd==dont_expand) + @<Get the next token, suppressing expansion@>@; + else check_outer_validity(); + } + else{@+cur_cmd=t/0400;cur_chr=t%0400; + switch (cur_cmd) { + case left_brace: incr(align_state);@+break; + case right_brace: decr(align_state);@+break; + case out_param: @<Insert macro parameter and |goto restart|@>@; + default:do_nothing; + } + } + } +else{@+ /*we are done with this token list*/ + end_token_list();goto restart; /*resume previous level*/ + } + +@ The present point in the program is reached only when the |expand| +routine has inserted a special marker into the input. In this special +case, |info(loc)| is known to be a control sequence token, and |link(loc)==null|. + +@d no_expand_flag 257 /*this characterizes a special variant of |relax|*/ + +@<Get the next token, suppressing expansion@>= +{@+cur_cs=info(loc)-cs_token_flag;loc=null;@/ +cur_cmd=eq_type(cur_cs);cur_chr=equiv(cur_cs); +if (cur_cmd > max_command) + {@+cur_cmd=relax;cur_chr=no_expand_flag; + } +} + +@ @<Insert macro parameter...@>= +{@+begin_token_list(param_stack[param_start+cur_chr-1], parameter); +goto restart; +} + +@ All of the easy branches of |get_next| have now been taken care of. +There is one more branch. + +@d end_line_char_inactive (end_line_char < 0)||(end_line_char > 255) + +@<Move to next line of file, or |goto restart|...@>= +if (name > 17) @<Read next line of file into |buffer|, or |goto restart| if +the file has ended@>@; +else{@+if (!terminal_input) /*\.{\\read} line has ended*/ + {@+cur_cmd=0;cur_chr=0; + @<Set |cur_file_line| when a \.{\\read} line ends@>@; + return; + } + if (input_ptr > 0) /*text was inserted during error recovery*/ + {@+end_file_reading();goto restart; /*resume previous level*/ + } + if (selector < log_only) open_log_file(); + if (interaction > nonstop_mode) + {@+if (end_line_char_inactive) incr(limit); + if (limit==start) /*previous line was empty*/ + print_nl("(Please type a command or say `\\end')"); +@.Please type...@> + print_ln();first=start; + prompt_input("*"); /*input on-line into |buffer|*/ +@.*\relax@> + limit=last; + if (end_line_char_inactive) decr(limit); + else buffer[limit]=end_line_char; + first=limit+1; + loc=start; + } + else fatal_error("*** (job aborted, no legal \\end found)"); +@.job aborted@> + /*nonstop mode, which is intended for overnight batch processing, + never waits for on-line input*/ + } + +@ The global variable |force_eof| is normally |false|; it is set |true| +by an \.{\\endinput} command. + +@<Glob...@>= +static bool @!force_eof; /*should the next \.{\\input} be aborted early?*/ + +@ @<Read next line of file into |buffer|, or |goto restart| if the file has +ended@>= +{@+incr(line);first=start; +@<check |line| for overflow@>@; +if (!force_eof) + if (name <= 19) + {@+if (pseudo_input()) /*not end of file*/ + firm_up_the_line(); /*this sets |limit|*/ + else if ((every_eof!=null)&&!eof_seen[index]) + {@+limit=first-1;eof_seen[index]=true; /*fake one empty line*/ + begin_token_list(every_eof, every_eof_text);goto restart; + } + else force_eof=true; + } + else + {@+if (input_ln(&cur_file, true)) /*not end of file*/ + firm_up_the_line(); /*this sets |limit|*/ + else if ((every_eof!=null)&&!eof_seen[index]) + {@+limit=first-1;eof_seen[index]=true; /*fake one empty line*/ + begin_token_list(every_eof, every_eof_text);goto restart; + } + else force_eof=true; + } +if (force_eof) + {@+if (tracing_nesting > 0) + if ((grp_stack[in_open]!=cur_boundary)||@| + (if_stack[in_open]!=cond_ptr)) file_warning(); + /*give warning for some unfinished groups and/or conditionals*/ + if (name >= 19) + {@+print_char(')');decr(open_parens); + update_terminal; /*show user that file has been read*/ + } + force_eof=false; + end_file_reading(); /*resume previous level*/ + check_outer_validity();goto restart; + } +if (end_line_char_inactive) decr(limit); +else buffer[limit]=end_line_char; +first=limit+1;loc=start; /*ready to read*/ +} + +@ If the user has set the |pausing| parameter to some positive value, +and if nonstop mode has not been selected, each line of input is displayed +on the terminal and the transcript file, followed by `\.{=>}'. +\TeX\ waits for a response. If the response is simply |carriage_return|, the +line is accepted as it stands, otherwise the line typed is +used instead of the line in the file. + +@p static void firm_up_the_line(void) +{@+int k; /*an index into |buffer|*/ +limit=last; +if (pausing > 0) if (interaction > nonstop_mode) + {@+wake_up_terminal;print_ln(); + if (start < limit) for (k=start; k<=limit-1; k++) printn(buffer[k]); + first=limit;prompt_input("=>"); /*wait for user response*/ +@.=>@> + if (last > first) + {@+for (k=first; k<=last-1; k++) /*move line down in buffer*/ + buffer[k+start-first]=buffer[k]; + limit=start+last-first; + } + } +} + +@ Since |get_next| is used so frequently in \TeX, it is convenient +to define three related procedures that do a little more: + +\yskip\hang|get_token| not only sets |cur_cmd| and |cur_chr|, it +also sets |cur_tok|, a packed halfword version of the current token. + +\yskip\hang|get_x_token|, meaning ``get an expanded token,'' is like +|get_token|, but if the current token turns out to be a user-defined +control sequence (i.e., a macro call), or a conditional, +or something like \.{\\topmark} or \.{\\expandafter} or \.{\\csname}, +it is eliminated from the input by beginning the expansion of the macro +or the evaluation of the conditional. + +\yskip\hang|x_token| is like |get_x_token| except that it assumes that +|get_next| has already been called. + +\yskip\noindent +In fact, these three procedures account for almost every use of |get_next|. + +@ No new control sequences will be defined except during a call of +|get_token|, or when \.{\\csname} compresses a token list, because +|no_new_control_sequence| is always |true| at other times. + +@p static void get_token(void) /*sets |cur_cmd|, |cur_chr|, |cur_tok|*/ +{@+no_new_control_sequence=false;get_next();no_new_control_sequence=true; +@^inner loop@> +if (cur_cs==0) cur_tok=(cur_cmd*0400)+cur_chr; +else cur_tok=cs_token_flag+cur_cs; +} + +@* Expanding the next token. +Only a dozen or so command codes | > max_command| can possibly be returned by +|get_next|; in increasing order, they are |undefined_cs|, |expand_after|, +|no_expand|, |input|, |if_test|, |fi_or_else|, |cs_name|, |convert|, |the|, +|top_bot_mark|, |call|, |long_call|, |outer_call|, |long_outer_call|, and +|end_template|.{\emergencystretch=40pt\par} + +The |expand| subroutine is used when |cur_cmd > max_command|. It removes a +``call'' or a conditional or one of the other special operations just +listed. It follows that |expand| might invoke itself recursively. In all +cases, |expand| destroys the current token, but it sets things up so that +the next |get_next| will deliver the appropriate next token. The value of +|cur_tok| need not be known when |expand| is called. + +Since several of the basic scanning routines communicate via global variables, +their values are saved as local variables of |expand| so that +recursive calls don't invalidate them. +@^recursion@> + +@p @t\4@>@<Declare the procedure called |macro_call|@>@;@/ +@t\4@>@<Declare the procedure called |insert_relax|@>@;@/ +@t\4@>@<Declare \eTeX\ procedures for expanding@>@;@/ +static void pass_text(void); +static void start_input(void); +static void conditional(void); +static void get_x_token(void); +static void conv_toks(void); +static void ins_the_toks(void); +static void expand(void) +{@+ +halfword t; /*token that is being ``expanded after''*/ +pointer @!p, @!q, @!r; /*for list manipulation*/ +int @!j; /*index into |buffer|*/ +int @!cv_backup; /*to save the global quantity |cur_val|*/ +small_number @!cvl_backup, @!radix_backup, @!co_backup; + /*to save |cur_val_level|, etc.*/ +pointer @!backup_backup; /*to save |link(backup_head)|*/ +small_number @!save_scanner_status; /*temporary storage of |scanner_status|*/ +cv_backup=cur_val;cvl_backup=cur_val_level;radix_backup=radix; +co_backup=cur_order;backup_backup=link(backup_head); +reswitch: +if (cur_cmd < call) @<Expand a nonmacro@>@; +else if (cur_cmd < end_template) macro_call(); +else@<Insert a token containing |frozen_endv|@>; +cur_val=cv_backup;cur_val_level=cvl_backup;radix=radix_backup; +cur_order=co_backup;link(backup_head)=backup_backup; +} + +@ @<Expand a nonmacro@>= +{@+if (tracing_commands > 1) show_cur_cmd_chr(); +switch (cur_cmd) { +case top_bot_mark: @<Insert the \(a)appropriate mark text into the scanner@>@;@+break; +case expand_after: switch (cur_chr) { +case 0: @<Expand the token after the next token@>@;@+break; +case 1: @<Negate a boolean conditional and |goto reswitch|@>@;@+break; +@/@<Cases for |expandafter|@>@/ +} @+break; /*there are no other cases*/ +case no_expand: @<Suppress expansion of the next token@>@;@+break; +case cs_name: @<Manufacture a control sequence name@>@;@+break; +case convert: conv_toks();@+break; /*this procedure is discussed in Part 27 below*/ +case the: ins_the_toks();@+break; /*this procedure is discussed in Part 27 below*/ +case if_test: conditional();@+break; /*this procedure is discussed in Part 28 below*/ +case fi_or_else: @<Terminate the current conditional and skip to \.{\\fi}@>@;@+break; +case input: @<Initiate or terminate input from a file@>;@+break; +default:@<Complain about an undefined macro@>@; +} +} + +@ It takes only a little shuffling to do what \TeX\ calls \.{\\expandafter}. + +@<Expand the token after...@>= +{@+get_token();t=cur_tok;get_token(); +if (cur_cmd > max_command) expand();@+else back_input(); +cur_tok=t;back_input(); +} + +@ The implementation of \.{\\noexpand} is a bit trickier, because it is +necessary to insert a special `|dont_expand|' marker into \TeX's reading +mechanism. This special marker is processed by |get_next|, but it does +not slow down the inner loop. + +Since \.{\\outer} macros might arise here, we must also +clear the |scanner_status| temporarily. + +@<Suppress expansion...@>= +{@+save_scanner_status=scanner_status;scanner_status=normal; +get_token();scanner_status=save_scanner_status;t=cur_tok; +back_input(); /*now |start| and |loc| point to the backed-up token |t|*/ +if (t >= cs_token_flag) + {@+p=get_avail();info(p)=cs_token_flag+frozen_dont_expand; + link(p)=loc;start=p;loc=p; + } +} + +@ @<Complain about an undefined macro@>= +{@+print_err("Undefined control sequence"); +@.Undefined control sequence@> +help5("The control sequence at the end of the top line",@/ +"of your error message was never \\def'ed. If you have",@/ +"misspelled it (e.g., `\\hobx'), type `I' and the correct",@/ +"spelling (e.g., `I\\hbox'). Otherwise just continue,",@/ +"and I'll forget about whatever was undefined."); +error(); +} + +@ The |expand| procedure and some other routines that construct token +lists find it convenient to use the following macros, which are valid only if +the variables |p| and |q| are reserved for token-list building. +Here we add code to store file and line information for each token. +@^profiling@> + +@d store_new_token(A) {@+q=get_avail();link(p)=q;info(q)=A; + fl_mem[q]=cur_file_line; + p=q; /*|link(p)| is |null|*/ + } +@d fast_store_new_token(A) {@+fast_get_avail(q);link(p)=q;info(q)=A; + fl_mem[q]=cur_file_line; + p=q; /*|link(p)| is |null|*/ + } + +@ @<Manufacture a control...@>= +{@+r=get_avail();p=r; /*head of the list of characters*/ +incr(incsname_state); +@/do@+{get_x_token(); +if (cur_cs==0) store_new_token(cur_tok); +}@+ while (!(cur_cs!=0)); +if (cur_cmd!=end_cs_name) @<Complain about missing \.{\\endcsname}@>; +decr(incsname_state); +@<Look up the characters of list |r| in the hash table, and set |cur_cs|@>; +flush_list(r); +if (eq_type(cur_cs)==undefined_cs) + {@+eq_define(cur_cs, relax, 256); /*N.B.: The |save_stack| might change*/ + } /*the control sequence will now match `\.{\\relax}'*/ +cur_tok=cur_cs+cs_token_flag;back_input(); +} + +@ @<Complain about missing \.{\\endcsname}@>= +{@+print_err("Missing ");print_esc("endcsname");print(" inserted"); +@.Missing \\endcsname...@> +help2("The control sequence marked <to be read again> should",@/ + "not appear between \\csname and \\endcsname."); +back_error(); +} + +@ @<Look up the characters of list |r| in the hash table...@>= +j=first;p=link(r); +while (p!=null) + {@+if (j >= max_buf_stack) + {@+max_buf_stack=j+1; + if (max_buf_stack==buf_size) + overflow("buffer size", buf_size); +@:TeX capacity exceeded buffer size}{\quad buffer size@> + } + buffer[j]=info(p)%0400;incr(j);p=link(p); + } +if (j==first) cur_cs=null_cs; /*the list is empty*/ +else if (j > first+1) + {@+no_new_control_sequence=false;cur_cs=id_lookup(first, j-first); + no_new_control_sequence=true; + } +else cur_cs=single_base+buffer[first] /*the list has length one*/ + +@ An |end_template| command is effectively changed to an |endv| command +by the following code. (The reason for this is discussed below; the +|frozen_end_template| at the end of the template has passed the +|check_outer_validity| test, so its mission of error detection has been +accomplished.) + +@<Insert a token containing |frozen_endv|@>= +{@+cur_tok=cs_token_flag+frozen_endv;back_input(); +} + +@ The processing of \.{\\input} involves the |start_input| subroutine, +which will be declared later; the processing of \.{\\endinput} is trivial. + +@<Put each...@>= +primitive("input", input, 0);@/ +@!@:input\_}{\.{\\input} primitive@> +input_loc=cur_val;input_token=cs_token_flag+input_loc; +primitive("endinput", input, 1);@/ +@!@:end\_input\_}{\.{\\endinput} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case input: if (chr_code==0) print_esc("input") + @/@<Cases of |input| for |print_cmd_chr|@>;@/ + else print_esc("endinput");@+break; + +@ @<Initiate or terminate input...@>= +if (cur_chr==1) force_eof=true +@/@<Cases for |input|@>;@/ +else if (name_in_progress) insert_relax(); +else start_input() + +@ Sometimes the expansion looks too far ahead, so we want to insert +a harmless \.{\\relax} into the user's input. + +@<Declare the procedure called |insert_relax|@>= +static void insert_relax(void) +{@+cur_tok=cs_token_flag+cur_cs;back_input(); +cur_tok=cs_token_flag+frozen_relax;back_input();token_type=inserted; +} + +@ Here is a recursive procedure that is \TeX's usual way to get the +next token of input. It has been slightly optimized to take account of +common cases. + +@p static void get_x_token(void) /*sets |cur_cmd|, |cur_chr|, |cur_tok|, + and expands macros*/ +{@+ +restart: get_next(); +@^inner loop@> +if (cur_cmd <= max_command) goto done; +if (cur_cmd >= call) + if (cur_cmd < end_template) macro_call(); + else{@+cur_cs=frozen_endv;cur_cmd=endv; + goto done; /*|cur_chr==null_list|*/ + } +else expand(); +goto restart; +done: if (cur_cs==0) cur_tok=(cur_cmd*0400)+cur_chr; +else cur_tok=cs_token_flag+cur_cs; +} + +@ The |get_x_token| procedure is essentially equivalent to two consecutive +procedure calls: |get_next;x_token|. + +@p static void x_token(void) /*|get_x_token| without the initial |get_next|*/ +{@+while (cur_cmd > max_command) + {@+expand(); + get_next(); + } +if (cur_cs==0) cur_tok=(cur_cmd*0400)+cur_chr; +else cur_tok=cs_token_flag+cur_cs; +} + +@ A control sequence that has been \.{\\def}'ed by the user is expanded by +\TeX's |macro_call| procedure. + +Before we get into the details of |macro_call|, however, let's consider the +treatment of primitives like \.{\\topmark}, since they are essentially +macros without parameters. The token lists for such marks are kept in a +global array of five pointers; we refer to the individual entries of this +array by symbolic names |top_mark|, etc. The value of |top_mark| is either +|null| or a pointer to the reference count of a token list. + +@d marks_code 5 /*add this for \.{\\topmarks} etc.*/ +@# +@d top_mark_code 0 /*the mark in effect at the previous page break*/ +@d first_mark_code 1 /*the first mark between |top_mark| and |bot_mark|*/ +@d bot_mark_code 2 /*the mark in effect at the current page break*/ +@d split_first_mark_code 3 /*the first mark found by \.{\\vsplit}*/ +@d split_bot_mark_code 4 /*the last mark found by \.{\\vsplit}*/ +@d top_mark cur_mark[top_mark_code] +@d first_mark cur_mark[first_mark_code] +@d bot_mark cur_mark[bot_mark_code] +@d split_first_mark cur_mark[split_first_mark_code] +@d split_bot_mark cur_mark[split_bot_mark_code] + +@<Glob...@>= +static pointer @!cur_mark0[split_bot_mark_code-top_mark_code+1], + *const @!cur_mark = @!cur_mark0-top_mark_code; + /*token lists for marks*/ + +@ @<Set init...@>= +top_mark=null;first_mark=null;bot_mark=null; +split_first_mark=null;split_bot_mark=null; + +@ @<Put each...@>= +primitive("topmark", top_bot_mark, top_mark_code); +@!@:top\_mark\_}{\.{\\topmark} primitive@> +primitive("firstmark", top_bot_mark, first_mark_code); +@!@:first\_mark\_}{\.{\\firstmark} primitive@> +primitive("botmark", top_bot_mark, bot_mark_code); +@!@:bot\_mark\_}{\.{\\botmark} primitive@> +primitive("splitfirstmark", top_bot_mark, split_first_mark_code); +@!@:split\_first\_mark\_}{\.{\\splitfirstmark} primitive@> +primitive("splitbotmark", top_bot_mark, split_bot_mark_code); +@!@:split\_bot\_mark\_}{\.{\\splitbotmark} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case top_bot_mark: {@+switch ((chr_code%marks_code)) { + case first_mark_code: print_esc("firstmark");@+break; + case bot_mark_code: print_esc("botmark");@+break; + case split_first_mark_code: print_esc("splitfirstmark");@+break; + case split_bot_mark_code: print_esc("splitbotmark");@+break; + default:print_esc("topmark"); + } + if (chr_code >= marks_code) print_char('s'); + } @+break; + +@ The following code is activated when |cur_cmd==top_bot_mark| and +when |cur_chr| is a code like |top_mark_code|. + +@<Insert the \(a)appropriate mark text into the scanner@>= +{@+t=cur_chr%marks_code; +if (cur_chr >= marks_code) scan_register_num();@+else cur_val=0; +if (cur_val==0) cur_ptr=cur_mark[t]; +else@<Compute the mark pointer for mark type |t| and class |cur_val|@>; +if (cur_ptr!=null) begin_token_list(cur_ptr, mark_text); +} + +@ Now let's consider |macro_call| itself, which is invoked when \TeX\ is +scanning a control sequence whose |cur_cmd| is either |call|, |long_call|, +|outer_call|, or |long_outer_call|. The control sequence definition +appears in the token list whose reference count is in location |cur_chr| +of |mem|. + +The global variable |long_state| will be set to |call| or to |long_call|, +depending on whether or not the control sequence disallows \.{\\par} +in its parameters. The |get_next| routine will set |long_state| to +|outer_call| and emit \.{\\par}, if a file ends or if an \.{\\outer} +control sequence occurs in the midst of an argument. + +@<Glob...@>= +static int @!long_state; /*governs the acceptance of \.{\\par}*/ + +@ The parameters, if any, must be scanned before the macro is expanded. +Parameters are token lists without reference counts. They are placed on +an auxiliary stack called |pstack| while they are being scanned, since +the |param_stack| may be losing entries during the matching process. +(Note that |param_stack| can't be gaining entries, since |macro_call| is +the only routine that puts anything onto |param_stack|, and it +is not recursive.) + +@<Glob...@>= +static pointer @!pstack[9]; /*arguments supplied to a macro*/ + +@ After parameter scanning is complete, the parameters are moved to the +|param_stack|. Then the macro body is fed to the scanner; in other words, +|macro_call| places the defined text of the control sequence at the +top of\/ \TeX's input stack, so that |get_next| will proceed to read it +next. + +The global variable |cur_cs| contains the |eqtb| address of the control sequence +being expanded, when |macro_call| begins. If this control sequence has not been +declared \.{\\long}, i.e., if its command code in the |eq_type| field is +not |long_call| or |long_outer_call|, its parameters are not allowed to contain +the control sequence \.{\\par}. If an illegal \.{\\par} appears, the macro +call is aborted, and the \.{\\par} will be rescanned. + +@<Declare the procedure called |macro_call|@>= +static void macro_call(void) /*invokes a user-defined control sequence*/ +{@+ +pointer r; /*current node in the macro's token list*/ +pointer @!p; /*current node in parameter token list being built*/ +pointer @!q; /*new node being put into the token list*/ +pointer @!s; /*backup pointer for parameter matching*/ +pointer @!t; /*cycle pointer for backup recovery*/ +pointer @!u, @!v; /*auxiliary pointers for backup recovery*/ +pointer @!rbrace_ptr; /*one step before the last |right_brace| token*/ +small_number @!n; /*the number of parameters scanned*/ +halfword @!unbalance; /*unmatched left braces in current parameter*/ +int @!m; /*the number of tokens or groups (usually)*/ +pointer @!ref_count; /*start of the token list*/ +small_number @!save_scanner_status; /*|scanner_status| upon entry*/ +pointer @!save_warning_index; /*|warning_index| upon entry*/ +ASCII_code @!match_chr; /*character used in parameter*/ +@<additional local variables for |macro_call|@>@; +save_scanner_status=scanner_status;save_warning_index=warning_index; +warning_index=cur_cs;ref_count=cur_chr;r=link(ref_count);n=0; +if (tracing_macros > 0) @<Show the text of the macro being expanded@>; +if (info(r)==protected_token) r=link(r); +if (info(r)!=end_match_token) + @<Scan the parameters and make |link(r)| point to the macro body; but |goto end| +if an illegal \.{\\par} is detected@>; +@<Feed the macro body and its parameters to the scanner@>; +end: scanner_status=save_scanner_status;warning_index=save_warning_index; +@<update the macro stack@>@; +} + +@ Before we put a new token list on the input stack, it is wise to clean off +all token lists that have recently been depleted. Then a user macro that ends +with a call to itself will not require unbounded stack space. + +@<Feed the macro body and its parameters to the scanner@>= +while ((state==token_list)&&(loc==null)&&(token_type!=v_template)) + end_token_list(); /*conserve stack space*/ +begin_token_list(ref_count, macro);name=warning_index;loc=link(r); +if (n > 0) + {@+if (param_ptr+n > max_param_stack) + {@+max_param_stack=param_ptr+n; + if (max_param_stack > param_size) + overflow("parameter stack size", param_size); +@:TeX capacity exceeded parameter stack size}{\quad parameter stack size@> + } + for (m=0; m<=n-1; m++) param_stack[param_ptr+m]=pstack[m]; + param_ptr=param_ptr+n; + } + +@ At this point, the reader will find it advisable to review the explanation +of token list format that was presented earlier, since many aspects of that +format are of importance chiefly in the |macro_call| routine. + +The token list might begin with a string of compulsory tokens before the +first |match| or |end_match|. In that case the macro name is supposed to be +followed by those tokens; the following program will set |s==null| to +represent this restriction. Otherwise |s| will be set to the first token of +a string that will delimit the next parameter. + +@<Scan the parameters and make |link(r)| point to the macro body...@>= +{@+scanner_status=matching;unbalance=0; +long_state=eq_type(cur_cs); +if (long_state >= outer_call) long_state=long_state-2; +@/do@+{link(temp_head)=null; +if ((info(r) > match_token+255)||(info(r) < match_token)) s=null; +else{@+match_chr=info(r)-match_token;s=link(r);r=s; + p=temp_head;m=0; + } +@<Scan a parameter until its delimiter string has been found; or, if |s=null|, +simply scan the delimiter string@>;@/ + /*now |info(r)| is a token whose command code is either |match| or |end_match|*/ +}@+ while (!(info(r)==end_match_token)); +} + +@ If |info(r)| is a |match| or |end_match| command, it cannot be equal to +any token found by |get_token|. Therefore an undelimited parameter---i.e., +a |match| that is immediately followed by |match| or |end_match|---will +always fail the test `|cur_tok==info(r)|' in the following algorithm. + +@<Scan a parameter until its delimiter string has been found; or,...@>= +resume: get_token(); /*set |cur_tok| to the next token of input*/ +if (cur_tok==info(r)) + @<Advance \(r)|r|; |goto found| if the parameter delimiter has been fully +matched, otherwise |goto resume|@>; +@<Contribute the recently matched tokens to the current parameter, and |goto +resume| if a partial match is still in effect; but abort if |s=null|@>; +if (cur_tok==par_token) if (long_state!=long_call) + @<Report a runaway argument and abort@>; +if (cur_tok < right_brace_limit) + if (cur_tok < left_brace_limit) + @<Contribute an entire group to the current parameter@>@; + else@<Report an extra right brace and |goto resume|@>@; +else@<Store the current token, but |goto resume| if it is a blank space +that would become an undelimited parameter@>; +incr(m); +if (info(r) > end_match_token) goto resume; +if (info(r) < match_token) goto resume; +found: if (s!=null) @<Tidy up the parameter just scanned, and tuck it away@>@; + +@ @<Store the current token, but |goto resume| if it is...@>= +{@+if (cur_tok==space_token) + if (info(r) <= end_match_token) + if (info(r) >= match_token) goto resume; +store_new_token(cur_tok); +} + +@ A slightly subtle point arises here: When the parameter delimiter ends +with `\.{\#\{}', the token list will have a left brace both before and +after the |end_match|\kern-.4pt. Only one of these should affect the +|align_state|, but both will be scanned, so we must make a correction. + +@<Advance \(r)|r|; |goto found| if the parameter delimiter has been fully...@>= +{@+r=link(r); +if ((info(r) >= match_token)&&(info(r) <= end_match_token)) + {@+if (cur_tok < left_brace_limit) decr(align_state); + goto found; + } +else goto resume; +} + +@ @<Report an extra right brace and |goto resume|@>= +{@+back_input();print_err("Argument of ");sprint_cs(warning_index); +@.Argument of \\x has...@> +print(" has an extra }"); +help6("I've run across a `}' that doesn't seem to match anything.",@/ + "For example, `\\def\\a#1{...}' and `\\a}' would produce",@/ + "this error. If you simply proceed now, the `\\par' that",@/ + "I've just inserted will cause me to report a runaway",@/ + "argument that might be the root of the problem. But if",@/ + "your `}' was spurious, just type `2' and it will go away."); +incr(align_state);long_state=call;cur_tok=par_token;ins_error(); +goto resume; +} /*a white lie; the \.{\\par} won't always trigger a runaway*/ + +@ If |long_state==outer_call|, a runaway argument has already been reported. + +@<Report a runaway argument and abort@>= +{@+if (long_state==call) + {@+runaway();print_err("Paragraph ended before "); +@.Paragraph ended before...@> + sprint_cs(warning_index);print(" was complete"); + help3("I suspect you've forgotten a `}', causing me to apply this",@/ + "control sequence to too much text. How can we recover?",@/ + "My plan is to forget the whole thing and hope for the best."); + back_error(); + } +pstack[n]=link(temp_head);align_state=align_state-unbalance; +for (m=0; m<=n; m++) flush_list(pstack[m]); +goto end; +} + +@ When the following code becomes active, we have matched tokens from |s| to +the predecessor of |r|, and we have found that |cur_tok!=info(r)|. An +interesting situation now presents itself: If the parameter is to be +delimited by a string such as `\.{ab}', and if we have scanned `\.{aa}', +we want to contribute one `\.a' to the current parameter and resume +looking for a `\.b'. The program must account for such partial matches and +for others that can be quite complex. But most of the time we have |s==r| +and nothing needs to be done. + +Incidentally, it is possible for \.{\\par} tokens to sneak in to certain +parameters of non-\.{\\long} macros. For example, consider a case like +`\.{\\def\\a\#1\\par!\{...\}}' where the first \.{\\par} is not followed +by an exclamation point. In such situations it does not seem appropriate +to prohibit the \.{\\par}, so \TeX\ keeps quiet about this bending of +the rules. + +@<Contribute the recently matched tokens to the current parameter...@>= +if (s!=r) + if (s==null) @<Report an improper use of the macro and abort@>@; + else{@+t=s; + @/do@+{store_new_token(info(t));incr(m);u=link(t);v=s; + loop@+{@+if (u==r) + if (cur_tok!=info(v)) goto done; + else{@+r=link(v);goto resume; + } + if (info(u)!=info(v)) goto done; + u=link(u);v=link(v); + } + done: t=link(t); + }@+ while (!(t==r)); + r=s; /*at this point, no tokens are recently matched*/ + } + +@ @<Report an improper use...@>= +{@+print_err("Use of ");sprint_cs(warning_index); +@.Use of x doesn't match...@> +print(" doesn't match its definition"); +help4("If you say, e.g., `\\def\\a1{...}', then you must always",@/ + "put `1' after `\\a', since control sequence names are",@/ + "made up of letters only. The macro here has not been",@/ + "followed by the required stuff, so I'm ignoring it."); +error();goto end; +} + +@ @<Contribute an entire group to the current parameter@>= +{@+unbalance=1; +@^inner loop@> +loop@+{@+fast_store_new_token(cur_tok);get_token(); + if (cur_tok==par_token) if (long_state!=long_call) + @<Report a runaway argument and abort@>; + if (cur_tok < right_brace_limit) + if (cur_tok < left_brace_limit) incr(unbalance); + else{@+decr(unbalance); + if (unbalance==0) goto done1; + } + } +done1: rbrace_ptr=p;store_new_token(cur_tok); +} + +@ If the parameter consists of a single group enclosed in braces, we must +strip off the enclosing braces. That's why |rbrace_ptr| was introduced. + +@<Tidy up the parameter just scanned, and tuck it away@>= +{@+if ((m==1)&&(info(p) < right_brace_limit)) + {@+link(rbrace_ptr)=null;free_avail(p); + p=link(temp_head);pstack[n]=link(p);free_avail(p); + } +else pstack[n]=link(temp_head); +incr(n); +if (tracing_macros > 0) + {@+begin_diagnostic();print_nl("");printn(match_chr);print_int(n); + print("<-");show_token_list(pstack[n-1], null, 1000); + end_diagnostic(false); + } +} + +@ @<Show the text of the macro being expanded@>= +{@+begin_diagnostic();print_ln();print_cs(warning_index); +token_show(ref_count);end_diagnostic(false); +} + +@* Basic scanning subroutines. +Let's turn now to some procedures that \TeX\ calls upon frequently to digest +certain kinds of patterns in the input. Most of these are quite simple; +some are quite elaborate. Almost all of the routines call |get_x_token|, +which can cause them to be invoked recursively. +@^stomach@> +@^recursion@> + +@ The |scan_left_brace| routine is called when a left brace is supposed to be +the next non-blank token. (The term ``left brace'' means, more precisely, +a character whose catcode is |left_brace|.) \TeX\ allows \.{\\relax} to +appear before the |left_brace|. + +@p static void scan_left_brace(void) /*reads a mandatory |left_brace|*/ +{@+@<Get the next non-blank non-relax non-call token@>; +if (cur_cmd!=left_brace) + {@+print_err("Missing { inserted"); +@.Missing \{ inserted@> + help4("A left brace was mandatory here, so I've put one in.",@/ + "You might want to delete and/or insert some corrections",@/ + "so that I will find a matching right brace soon.",@/ + "(If you're confused by all this, try typing `I}' now.)"); + back_error();cur_tok=left_brace_token+'{';cur_cmd=left_brace; + cur_chr='{';incr(align_state); + } +} + +@ @<Get the next non-blank non-relax non-call token@>= +@/do@+{get_x_token(); +}@+ while (!((cur_cmd!=spacer)&&(cur_cmd!=relax))) + +@ The |scan_optional_equals| routine looks for an optional `\.=' sign preceded +by optional spaces; `\.{\\relax}' is not ignored here. + +@p static void scan_optional_equals(void) +{@+@<Get the next non-blank non-call token@>; +if (cur_tok!=other_token+'=') back_input(); +} + +@ @<Get the next non-blank non-call token@>= +@/do@+{get_x_token(); +}@+ while (!(cur_cmd!=spacer)) + +@ In case you are getting bored, here is a slightly less trivial routine: +Given a string of lowercase letters, like `\.{pt}' or `\.{plus}' or +`\.{width}', the |scan_keyword| routine checks to see whether the next +tokens of input match this string. The match must be exact, except that +uppercase letters will match their lowercase counterparts; uppercase +equivalents are determined by subtracting |'a'-'A'|, rather than using the +|uc_code| table, since \TeX\ uses this routine only for its own limited +set of keywords. + +If a match is found, the characters are effectively removed from the input +and |true| is returned. Otherwise |false| is returned, and the input +is left essentially unchanged (except for the fact that some macros +may have been expanded, etc.). +@^inner loop@> + +@p static bool scan_keyword(char *@!s) /*look for a given string*/ +{@+ +pointer p; /*tail of the backup list*/ +pointer @!q; /*new node being added to the token list via |store_new_token|*/ +p=backup_head;link(p)=null; +while (*s!=0) + {@+get_x_token(); /*recursion is possible here*/ +@^recursion@> + if ((cur_cs==0)&&@| + ((cur_chr==so(*s))||(cur_chr==so(*s)-'a'+'A'))) + {@+store_new_token(cur_tok);incr(s); + } + else if ((cur_cmd!=spacer)||(p!=backup_head)) + {@+back_input(); + if (p!=backup_head) back_list(link(backup_head)); + return false; + } + } +flush_list(link(backup_head));return true; +} + +@ Here is a procedure that sounds an alarm when mu and non-mu units +are being switched. + +@p static void mu_error(void) +{@+print_err("Incompatible glue units"); +@.Incompatible glue units@> +help1("I'm going to assume that 1mu=1pt when they're mixed."); +error(); +} + +@ The next routine `|scan_something_internal|' is used to fetch internal +numeric quantities like `\.{\\hsize}', and also to handle the `\.{\\the}' +when expanding constructions like `\.{\\the\\toks0}' and +`\.{\\the\\baselineskip}'. Soon we will be considering the |scan_int| +procedure, which calls |scan_something_internal|; on the other hand, +|scan_something_internal| also calls |scan_int|, for constructions like +`\.{\\catcode\`\\\$}' or `\.{\\fontdimen} \.3 \.{\\ff}'. So we +have to declare |scan_int| as a |forward| procedure. A few other +procedures are also declared at this point. + +@p static void scan_int(void); /*scans an integer value*/ +@t\4\4@>@<Declare procedures that scan restricted classes of integers@>@; +@t\4\4@>@<Declare \eTeX\ procedures for scanning@>@; +@t\4\4@>@<Declare procedures that scan font-related stuff@>@; + +@ \TeX\ doesn't know exactly what to expect when |scan_something_internal| +begins. For example, an integer or dimension or glue value could occur +immediately after `\.{\\hskip}'; and one can even say \.{\\the} with +respect to token lists in constructions like +`\.{\\xdef\\o\{\\the\\output\}}'. On the other hand, only integers are +allowed after a construction like `\.{\\count}'. To handle the various +possibilities, |scan_something_internal| has a |level| parameter, which +tells the ``highest'' kind of quantity that |scan_something_internal| is +allowed to produce. Six levels are distinguished, namely |int_val|, +|dimen_val|, |glue_val|, |mu_val|, |ident_val|, and |tok_val|. + +The output of |scan_something_internal| (and of the other routines +|scan_int|, |scan_dimen|, and |scan_glue| below) is put into the global +variable |cur_val|, and its level is put into |cur_val_level|. The highest +values of |cur_val_level| are special: |mu_val| is used only when +|cur_val| points to something in a ``muskip'' register, or to one of the +three parameters \.{\\thinmuskip}, \.{\\medmuskip}, \.{\\thickmuskip}; +|ident_val| is used only when |cur_val| points to a font identifier; +|tok_val| is used only when |cur_val| points to |null| or to the reference +count of a token list. The last two cases are allowed only when +|scan_something_internal| is called with |level==tok_val|. + +If the output is glue, |cur_val| will point to a glue specification, and +the reference count of that glue will have been updated to reflect this +reference; if the output is a nonempty token list, |cur_val| will point to +its reference count, but in this case the count will not have been updated. +Otherwise |cur_val| will contain the integer or scaled value in question. + +@d int_val 0 /*integer values*/ +@d dimen_val 1 /*dimension values*/ +@d glue_val 2 /*glue specifications*/ +@d mu_val 3 /*math glue specifications*/ +@d ident_val 4 /*font identifier*/ +@d tok_val 5 /*token lists*/ + +@<Glob...@>= +static int @!cur_val; /*value returned by numeric scanners*/ +static int @!cur_val_level; /*the ``level'' of this value*/ + +@ The hash table is initialized with `\.{\\count}', `\.{\\dimen}', `\.{\\skip}', +and `\.{\\muskip}' all having |internal_register| as their command code; they are +distinguished by the |chr_code|, which is either |int_val|, |dimen_val|, +|glue_val|, or |mu_val| more than |mem_bot| (dynamic variable-size nodes +cannot have these values) + +@<Put each...@>= +primitive("count", internal_register, mem_bot+int_val); +@!@:count\_}{\.{\\count} primitive@> +primitive("dimen", internal_register, mem_bot+dimen_val); +@!@:dimen\_}{\.{\\dimen} primitive@> +primitive("skip", internal_register, mem_bot+glue_val); +@!@:skip\_}{\.{\\skip} primitive@> +primitive("muskip", internal_register, mem_bot+mu_val); +@!@:mu\_skip\_}{\.{\\muskip} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case internal_register: @<Cases of |register| for |print_cmd_chr|@>@;@+break; + +@ OK, we're ready for |scan_something_internal| itself. A second parameter, +|negative|, is set |true| if the value that is found should be negated. +It is assumed that |cur_cmd| and |cur_chr| represent the first token of +the internal quantity to be scanned; an error will be signalled if +|cur_cmd < min_internal| or |cur_cmd > max_internal|. + +@d scanned_result(A, B) @+{@+cur_val=A;cur_val_level=B;@+} + +@p static void scan_something_internal(small_number @!level, bool @!negative) + /*fetch an internal parameter*/ +{@+ +halfword m; /*|chr_code| part of the operand token*/ +pointer @!q, @!r; /*general purpose indices*/ +pointer @!tx; /*effective tail node*/ +four_quarters @!i; /*character info*/ +int @!p; /*index into |nest|*/ +m=cur_chr; +switch (cur_cmd) { +case def_code: @<Fetch a character code from some table@>@;@+break; +case toks_register: case assign_toks: + case def_family: case set_font: case def_font: @<Fetch a token list or font +identifier, provided that |level=tok_val|@>@;@+break; +case assign_int: scanned_result(eqtb[m].i, int_val)@;@+break; +case assign_dimen: scanned_result(eqtb[m].sc, dimen_val)@;@+break; +case assign_glue: scanned_result(equiv(m), glue_val)@;@+break; +case assign_mu_glue: scanned_result(equiv(m), mu_val)@;@+break; +case set_aux: @<Fetch the |space_factor| or the |prev_depth|@>@;@+break; +case set_prev_graf: @<Fetch the |prev_graf|@>@;@+break; +case set_page_int: @<Fetch the |dead_cycles| or the |insert_penalties|@>@;@+break; +case set_page_dimen: @<Fetch something on the |page_so_far|@>@;@+break; +case set_shape: @<Fetch the |par_shape| size@>@;@+break; +case set_box_dimen: @<Fetch a box dimension@>@;@+break; +case char_given: case math_given: scanned_result(cur_chr, int_val)@;@+break; +case assign_font_dimen: @<Fetch a font dimension@>@;@+break; +case assign_font_int: @<Fetch a font integer@>@;@+break; +case internal_register: @<Fetch a register@>@;@+break; +case last_item: @<Fetch an item in the current node, if appropriate@>@;@+break; +default:@<Complain that \.{\\the} can't do this; give zero result@>@; +} @/ +while (cur_val_level > level) @<Convert \(c)|cur_val| to a lower level@>; +@<Fix the reference count, if any, and negate |cur_val| if |negative|@>; +} + +@ @<Fetch a character code from some table@>= +{@+scan_char_num(); +if (m==math_code_base) scanned_result(ho(math_code(cur_val)), int_val)@; +else if (m < math_code_base) scanned_result(equiv(m+cur_val), int_val)@; +else scanned_result(eqtb[m+cur_val].i, int_val); +} + +@ @<Fetch a token list...@>= +if (level!=tok_val) + {@+print_err("Missing number, treated as zero"); +@.Missing number...@> + help3("A number should have been here; I inserted `0'.",@/ + "(If you can't figure out why I needed to see a number,",@/ + "look up `weird error' in the index to The TeXbook.)"); +@:TeXbook}{\sl The \TeX book@> + back_error();scanned_result(0, dimen_val); + } +else if (cur_cmd <= assign_toks) + {@+if (cur_cmd < assign_toks) /*|cur_cmd==toks_register|*/ + if (m==mem_bot) + {@+scan_register_num(); + if (cur_val < 256) cur_val=equiv(toks_base+cur_val); + else{@+find_sa_element(tok_val, cur_val, false); + if (cur_ptr==null) cur_val=null; + else cur_val=sa_ptr(cur_ptr); + } + } + else cur_val=sa_ptr(m); + else cur_val=equiv(m); + cur_val_level=tok_val; + } +else{@+back_input();scan_font_ident(); + scanned_result(font_id_base+cur_val, ident_val); + } + +@ Users refer to `\.{\\the\\spacefactor}' only in horizontal +mode, and to `\.{\\the\\prevdepth}' only in vertical mode; so we put the +associated mode in the modifier part of the |set_aux| command. +The |set_page_int| command has modifier 0 or 1, for `\.{\\deadcycles}' and +`\.{\\insertpenalties}', respectively. The |set_box_dimen| command is +modified by either |width_offset|, |height_offset|, or |depth_offset|. +And the |last_item| command is modified by either |int_val|, |dimen_val|, +|glue_val|, |input_line_no_code|, or |badness_code|. +\eTeX\ inserts |last_node_type_code| after |glue_val| and adds +the codes for its extensions: |eTeX_version_code|, \dots\ . + +@d last_node_type_code (glue_val+1) /*code for \.{\\lastnodetype}*/ +@d input_line_no_code (glue_val+2) /*code for \.{\\inputlineno}*/ +@d badness_code (input_line_no_code+1) /*code for \.{\\badness}*/ +@# +@d eTeX_int (pdftex_last_item_codes+1) /*first of \eTeX\ codes for integers*/ +@d eTeX_dim (eTeX_int+8) /*first of \eTeX\ codes for dimensions*/ +@d eTeX_glue (eTeX_dim+9) /*first of \eTeX\ codes for glue*/ +@d eTeX_mu (eTeX_glue+1) /*first of \eTeX\ codes for muglue*/ +@d eTeX_expr (eTeX_mu+1) /*first of \eTeX\ codes for expressions*/ +@d eTeX_last_last_item_cmd_mod (eTeX_expr-int_val+mu_val) /*\.{\\muexpr}*/ + +@<Put each...@>= +primitive("spacefactor", set_aux, hmode); +@!@:space\_factor\_}{\.{\\spacefactor} primitive@> +primitive("prevdepth", set_aux, vmode);@/ +@!@:prev\_depth\_}{\.{\\prevdepth} primitive@> +primitive("deadcycles", set_page_int, 0); +@!@:dead\_cycles\_}{\.{\\deadcycles} primitive@> +primitive("insertpenalties", set_page_int, 1); +@!@:insert\_penalties\_}{\.{\\insertpenalties} primitive@> +primitive("wd", set_box_dimen, width_offset); +@!@:wd\_}{\.{\\wd} primitive@> +primitive("ht", set_box_dimen, height_offset); +@!@:ht\_}{\.{\\ht} primitive@> +primitive("dp", set_box_dimen, depth_offset); +@!@:dp\_}{\.{\\dp} primitive@> +primitive("lastpenalty", last_item, int_val); +@!@:last\_penalty\_}{\.{\\lastpenalty} primitive@> +primitive("lastkern", last_item, dimen_val); +@!@:last\_kern\_}{\.{\\lastkern} primitive@> +primitive("lastskip", last_item, glue_val); +@!@:last\_skip\_}{\.{\\lastskip} primitive@> +primitive("inputlineno", last_item, input_line_no_code); +@!@:input\_line\_no\_}{\.{\\inputlineno} primitive@> +primitive("badness", last_item, badness_code); +@!@:badness\_}{\.{\\badness} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case set_aux: if (chr_code==vmode) print_esc("prevdepth"); +@+else print_esc("spacefactor");@+break; +case set_page_int: if (chr_code==0) print_esc("deadcycles") +@/@<Cases of |set_page_int| for |print_cmd_chr|@>;@/ +@+else print_esc("insertpenalties");@+break; +case set_box_dimen: if (chr_code==width_offset) print_esc("wd"); +else if (chr_code==height_offset) print_esc("ht"); +else print_esc("dp");@+break; +case last_item: switch (chr_code) { + case int_val: print_esc("lastpenalty");@+break; + case dimen_val: print_esc("lastkern");@+break; + case glue_val: print_esc("lastskip");@+break; + case input_line_no_code: print_esc("inputlineno");@+break; + @/@<Cases of |last_item| for |print_cmd_chr|@>@/ + default:print_esc("badness"); + } @+break; + +@ @<Fetch the |space_factor| or the |prev_depth|@>= +if (abs(mode)!=m) + {@+print_err("Improper ");print_cmd_chr(set_aux, m); +@.Improper \\spacefactor@> +@.Improper \\prevdepth@> + help4("You can refer to \\spacefactor only in horizontal mode;",@/ + "you can refer to \\prevdepth only in vertical mode; and",@/ + "neither of these is meaningful inside \\write. So",@/ + "I'm forgetting what you said and using zero instead."); + error(); + if (level!=tok_val) scanned_result(0, dimen_val)@; + else scanned_result(0, int_val); + } +else if (m==vmode) scanned_result(prev_depth, dimen_val)@; +else scanned_result(space_factor, int_val) + +@ @<Fetch the |dead_cycles| or the |insert_penalties|@>= +{@+if (m==0) cur_val=dead_cycles +@/@<Cases for `Fetch the |dead_cycles| or the |insert_penalties|'@>;@/ +else cur_val=insert_penalties; +cur_val_level=int_val; +} + +@ @<Fetch a box dimension@>= +{@+scan_register_num();fetch_box(q); +if (q==null) cur_val=0;@+else cur_val=mem[q+m].sc; +cur_val_level=dimen_val; +} + +@ Inside an \.{\\output} routine, a user may wish to look at the page totals +that were present at the moment when output was triggered. + +@d max_dimen 07777777777 /*$2^{30}-1$*/ + +@<Fetch something on the |page_so_far|@>= +{@+if ((page_contents==empty)&&(!output_active)) + if (m==0) cur_val=max_dimen;@+else cur_val=0; +else cur_val=page_so_far[m]; +cur_val_level=dimen_val; +} + +@ @<Fetch the |prev_graf|@>= +if (mode==0) scanned_result(0, int_val)@; /*|prev_graf==0| within \.{\\write}*/ +else{@+nest[nest_ptr]=cur_list;p=nest_ptr; + while (abs(nest[p].mode_field)!=vmode) decr(p); + scanned_result(nest[p].pg_field, int_val); + } + +@ @<Fetch the |par_shape| size@>= +{@+if (m > par_shape_loc) @<Fetch a penalties array element@>@; +else if (par_shape_ptr==null) cur_val=0; +else cur_val=info(par_shape_ptr); +cur_val_level=int_val; +} + +@ Here is where \.{\\lastpenalty}, \.{\\lastkern}, \.{\\lastskip}, and +\.{\\lastnodetype} are +implemented. The reference count for \.{\\lastskip} will be updated later. + +We also handle \.{\\inputlineno} and \.{\\badness} here, because they are +legal in similar contexts. + +@<Fetch an item in the current node...@>= +if (m > eTeX_last_last_item_cmd_mod) +{@+switch (m) { + @/@<Cases for fetching a \Prote\ int value@>@/ + } /*there are no other cases*/ + cur_val_level=int_val; +} +else if (m >= input_line_no_code) +{if (m >= eTeX_glue) @<Process an expression and |return|@>@; + else if (m >= eTeX_dim) + {@+switch (m) { + @/@<Cases for fetching a dimension value@>@/ + } /*there are no other cases*/ + cur_val_level=dimen_val; + } + else + {@+switch (m) { + case input_line_no_code: cur_val=line;@+break; + case badness_code: cur_val=last_badness;@+break; + @/@<Cases for fetching an integer value@>@/ + } /*there are no other cases*/ + cur_val_level=int_val; + } +} +else{@+if (cur_chr==glue_val) cur_val=zero_glue;@+else cur_val=0; + tx=tail; + if (cur_chr==last_node_type_code) + {@+cur_val_level=int_val; + if ((tx==head)||(mode==0)) cur_val=-1; + } + else cur_val_level=cur_chr; + if (!is_char_node(tx)&&(mode!=0)) + switch (cur_chr) { + case int_val: if (type(tx)==penalty_node) cur_val=penalty(tx);@+break; + case dimen_val: if (type(tx)==kern_node) cur_val=width(tx);@+break; + case glue_val: if (type(tx)==glue_node) + {@+cur_val=glue_ptr(tx); + if (subtype(tx)==mu_glue) cur_val_level=mu_val; + } @+break; + case last_node_type_code: if (type(tx) <= unset_node) cur_val=type(tx)+1; + else cur_val=unset_node+2; + } /*there are no other cases*/ + else if ((mode==vmode)&&(tx==head)) + switch (cur_chr) { + case int_val: cur_val=last_penalty;@+break; + case dimen_val: cur_val=last_kern;@+break; + case glue_val: if (last_glue!=max_halfword) cur_val=last_glue;@+break; + case last_node_type_code: cur_val=last_node_type; + } /*there are no other cases*/ + } + +@ @<Fetch a font dimension@>= +{@+find_font_dimen(false);font_info[fmem_ptr].sc=0; +scanned_result(font_info[cur_val].sc, dimen_val); +} + +@ @<Fetch a font integer@>= +{@+scan_font_ident(); +if (m==0) scanned_result(hyphen_char[cur_val], int_val)@; +else scanned_result(skew_char[cur_val], int_val); +} + +@ @<Fetch a register@>= +{@+if ((m < mem_bot)||(m > lo_mem_stat_max)) + {@+cur_val_level=sa_type(m); + if (cur_val_level < glue_val) cur_val=sa_int(m); + else cur_val=sa_ptr(m); + } +else{@+scan_register_num();cur_val_level=m-mem_bot; + if (cur_val > 255) + {@+find_sa_element(cur_val_level, cur_val, false); + if (cur_ptr==null) + if (cur_val_level < glue_val) cur_val=0; + else cur_val=zero_glue; + else if (cur_val_level < glue_val) cur_val=sa_int(cur_ptr); + else cur_val=sa_ptr(cur_ptr); + } + else + switch (cur_val_level) { +case int_val: cur_val=count(cur_val);@+break; +case dimen_val: cur_val=dimen(cur_val);@+break; +case glue_val: cur_val=skip(cur_val);@+break; +case mu_val: cur_val=mu_skip(cur_val); +} /*there are no other cases*/ + } +} + +@ @<Complain that \.{\\the} can't do this; give zero result@>= +{@+print_err("You can't use `");print_cmd_chr(cur_cmd, cur_chr); +@.You can't use x after ...@> +print("' after ");print_esc("the"); +help1("I'm forgetting what you said and using zero instead."); +error(); +if (level!=tok_val) scanned_result(0, dimen_val)@; +else scanned_result(0, int_val); +} + +@ When a |glue_val| changes to a |dimen_val|, we use the width component +of the glue; there is no need to decrease the reference count, since it +has not yet been increased. When a |dimen_val| changes to an |int_val|, +we use scaled points so that the value doesn't actually change. And when a +|mu_val| changes to a |glue_val|, the value doesn't change either. + +@<Convert \(c)|cur_val| to a lower level@>= +{@+if (cur_val_level==glue_val) cur_val=width(cur_val); +else if (cur_val_level==mu_val) mu_error(); +decr(cur_val_level); +} + +@ If |cur_val| points to a glue specification at this point, the reference +count for the glue does not yet include the reference by |cur_val|. +If |negative| is |true|, |cur_val_level| is known to be | <= mu_val|. + +@<Fix the reference count, if any,...@>= +if (negative) + if (cur_val_level >= glue_val) + {@+cur_val=new_spec(cur_val); + @<Negate all three glue components of |cur_val|@>; + } + else negate(cur_val); +else if ((cur_val_level >= glue_val)&&(cur_val_level <= mu_val)) + add_glue_ref(cur_val) + +@ @<Negate all three...@>= +{@+negate(width(cur_val)); +negate(stretch(cur_val)); +negate(shrink(cur_val)); +} + +@ Our next goal is to write the |scan_int| procedure, which scans anything that +\TeX\ treats as an integer. But first we might as well look at some simple +applications of |scan_int| that have already been made inside of +|scan_something_internal|. + +@ @<Declare procedures that scan restricted classes of integers@>= +static void scan_eight_bit_int(void) +{@+scan_int(); +if ((cur_val < 0)||(cur_val > 255)) + {@+print_err("Bad register code"); +@.Bad register code@> + help2("A register number must be between 0 and 255.",@/ + "I changed this one to zero.");int_error(cur_val);cur_val=0; + } +} + +@ @<Declare procedures that scan restricted classes of integers@>= +static void scan_char_num(void) +{@+scan_int(); +if ((cur_val < 0)||(cur_val > 255)) + {@+print_err("Bad character code"); +@.Bad character code@> + help2("A character number must be between 0 and 255.",@/ + "I changed this one to zero.");int_error(cur_val);cur_val=0; + } +} + +@ While we're at it, we might as well deal with similar routines that +will be needed later. + +@<Declare procedures that scan restricted classes of integers@>= +static void scan_four_bit_int(void) +{@+scan_int(); +if ((cur_val < 0)||(cur_val > 15)) + {@+print_err("Bad number"); +@.Bad number@> + help2("Since I expected to read a number between 0 and 15,",@/ + "I changed this one to zero.");int_error(cur_val);cur_val=0; + } +} + +@ @<Declare procedures that scan restricted classes of integers@>= +static void scan_fifteen_bit_int(void) +{@+scan_int(); +if ((cur_val < 0)||(cur_val > 077777)) + {@+print_err("Bad mathchar"); +@.Bad mathchar@> + help2("A mathchar number must be between 0 and 32767.",@/ + "I changed this one to zero.");int_error(cur_val);cur_val=0; + } +} + +@ @<Declare procedures that scan restricted classes of integers@>= +static void scan_twenty_seven_bit_int(void) +{@+scan_int(); +if ((cur_val < 0)||(cur_val > 0777777777)) + {@+print_err("Bad delimiter code"); +@.Bad delimiter code@> + help2("A numeric delimiter code must be between 0 and 2^{27}-1.",@/ + "I changed this one to zero.");int_error(cur_val);cur_val=0; + } +} + +@ An integer number can be preceded by any number of spaces and `\.+' or +`\.-' signs. Then comes either a decimal constant (i.e., radix 10), an +octal constant (i.e., radix 8, preceded by~\.\'), a hexadecimal constant +(radix 16, preceded by~\."), an alphabetic constant (preceded by~\.\`), or +an internal variable. After scanning is complete, +|cur_val| will contain the answer, which must be at most +$2^{31}-1=2147483647$ in absolute value. The value of |radix| is set to +10, 8, or 16 in the cases of decimal, octal, or hexadecimal constants, +otherwise |radix| is set to zero. An optional space follows a constant. + +@d octal_token (other_token+'\'') /*apostrophe, indicates an octal constant*/ +@d hex_token (other_token+'"') /*double quote, indicates a hex constant*/ +@d alpha_token (other_token+'`') /*reverse apostrophe, precedes alpha constants*/ +@d point_token (other_token+'.') /*decimal point*/ +@d continental_point_token (other_token+',') /*decimal point, Eurostyle*/ + +@<Glob...@>= +static small_number @!radix; /*|scan_int| sets this to 8, 10, 16, or zero*/ + +@ We initialize the following global variables just in case |expand| +comes into action before any of the basic scanning routines has assigned +them a value. + +@<Set init...@>= +cur_val=0;cur_val_level=int_val;radix=0;cur_order=normal; + +@ The |scan_int| routine is used also to scan the integer part of a +fraction; for example, the `\.3' in `\.{3.14159}' will be found by +|scan_int|. The |scan_dimen| routine assumes that |cur_tok==point_token| +after the integer part of such a fraction has been scanned by |scan_int|, +and that the decimal point has been backed up to be scanned again. + +@p static void scan_int(void) /*sets |cur_val| to an integer*/ +{@+ +bool negative; /*should the answer be negated?*/ +int @!m; /*|@t$2^{31}$@>/radix|, the threshold of danger*/ +small_number @!d; /*the digit just scanned*/ +bool @!vacuous; /*have no digits appeared?*/ +bool @!OK_so_far; /*has an error message been issued?*/ +radix=0;OK_so_far=true;@/ +@<Get the next non-blank non-sign token; set |negative| appropriately@>; +if (cur_tok==alpha_token) @<Scan an alphabetic character code into |cur_val|@>@; +else if ((cur_cmd >= min_internal)&&(cur_cmd <= max_internal)) + scan_something_internal(int_val, false); +else@<Scan a numeric constant@>; +if (negative) negate(cur_val); +} + +@ @<Get the next non-blank non-sign token...@>= +negative=false; +@/do@+{@<Get the next non-blank non-call token@>; +if (cur_tok==other_token+'-') + {@+negative=!negative;cur_tok=other_token+'+'; + } +}@+ while (!(cur_tok!=other_token+'+')) + +@ A space is ignored after an alphabetic character constant, so that +such constants behave like numeric ones. + +@<Scan an alphabetic character code into |cur_val|@>= +{@+get_token(); /*suppress macro expansion*/ +if (cur_tok < cs_token_flag) + {@+cur_val=cur_chr; + if (cur_cmd <= right_brace) + if (cur_cmd==right_brace) incr(align_state); + else decr(align_state); + } +else if (cur_tok < cs_token_flag+single_base) + cur_val=cur_tok-cs_token_flag-active_base; +else cur_val=cur_tok-cs_token_flag-single_base; +if (cur_val > 255) + {@+print_err("Improper alphabetic constant"); +@.Improper alphabetic constant@> + help2("A one-character control sequence belongs after a ` mark.",@/ + "So I'm essentially inserting \\0 here."); + cur_val='0';back_error(); + } +else@<Scan an optional space@>; +} + +@ @<Scan an optional space@>= +{@+get_x_token();if (cur_cmd!=spacer) back_input(); +} + +@ @<Scan a numeric constant@>= +{@+radix=10;m=214748364; +if (cur_tok==octal_token) + {@+radix=8;m=02000000000;get_x_token(); + } +else if (cur_tok==hex_token) + {@+radix=16;m=01000000000;get_x_token(); + } +vacuous=true;cur_val=0;@/ +@<Accumulate the constant until |cur_tok| is not a suitable digit@>; +if (vacuous) @<Express astonishment that no number was here@>@; +else if (cur_cmd!=spacer) back_input(); +} + +@ @d infinity 017777777777 /*the largest positive value that \TeX\ knows*/ +@d zero_token (other_token+'0') /*zero, the smallest digit*/ +@d A_token (letter_token+'A') /*the smallest special hex digit*/ +@d other_A_token (other_token+'A') /*special hex digit of type |other_char|*/ + +@<Accumulate the constant...@>= +loop@+{@+if ((cur_tok < zero_token+radix)&&(cur_tok >= zero_token)&& + (cur_tok <= zero_token+9)) d=cur_tok-zero_token; + else if (radix==16) + if ((cur_tok <= A_token+5)&&(cur_tok >= A_token)) d=cur_tok-A_token+10; + else if ((cur_tok <= other_A_token+5)&&(cur_tok >= other_A_token)) + d=cur_tok-other_A_token+10; + else goto done; + else goto done; + vacuous=false; + if ((cur_val >= m)&&((cur_val > m)||(d > 7)||(radix!=10))) + {@+if (OK_so_far) + {@+print_err("Number too big"); +@.Number too big@> + help2("I can only go up to 2147483647='17777777777=\"7FFFFFFF,",@/ + "so I'm using that number instead of yours."); + error();cur_val=infinity;OK_so_far=false; + } + } + else cur_val=cur_val*radix+d; + get_x_token(); + } +done: + +@ @<Express astonishment...@>= +{@+print_err("Missing number, treated as zero"); +@.Missing number...@> +help3("A number should have been here; I inserted `0'.",@/ + "(If you can't figure out why I needed to see a number,",@/ + "look up `weird error' in the index to The TeXbook.)"); +@:TeXbook}{\sl The \TeX book@> +back_error(); +} + +@ The |scan_dimen| routine is similar to |scan_int|, but it sets |cur_val| to +a |scaled| value, i.e., an integral number of sp. One of its main tasks +is therefore to interpret the abbreviations for various kinds of units and +to convert measurements to scaled points. + +There are three parameters: |mu| is |true| if the finite units must be +`\.{mu}', while |mu| is |false| if `\.{mu}' units are disallowed; +|inf| is |true| if the infinite units `\.{fil}', `\.{fill}', `\.{filll}' +are permitted; and |shortcut| is |true| if |cur_val| already contains +an integer and only the units need to be considered. + +The order of infinity that was found in the case of infinite glue is returned +in the global variable |cur_order|. + +@<Glob...@>= +static glue_ord @!cur_order; /*order of infinity found by |scan_dimen|*/ + +@ Constructions like `\.{-\'77 pt}' are legal dimensions, so |scan_dimen| +may begin with |scan_int|. This explains why it is convenient to use +|scan_int| also for the integer part of a decimal fraction. + +Several branches of |scan_dimen| work with |cur_val| as an integer and +with an auxiliary fraction |f|, so that the actual quantity of interest is +$|cur_val|+|f|/2^{16}$. At the end of the routine, this ``unpacked'' +representation is put into the single word |cur_val|, which suddenly +switches significance from |int| to |scaled|. + +@d scan_normal_dimen scan_dimen(false, false, false) + +@p static void scan_dimen(bool @!mu, bool @!inf, bool @!shortcut) + /*sets |cur_val| to a dimension*/ +{@+ +bool negative; /*should the answer be negated?*/ +int @!f; /*numerator of a fraction whose denominator is $2^{16}$*/ +@<Local variables for dimension calculations@>@; +f=0;arith_error=false;cur_order=normal;negative=false; +if (!shortcut) + {@+@<Get the next non-blank non-sign...@>; + if ((cur_cmd >= min_internal)&&(cur_cmd <= max_internal)) + @<Fetch an internal dimension and |goto attach_sign|, or fetch an internal +integer@>@; + else{@+back_input(); + if (cur_tok==continental_point_token) cur_tok=point_token; + if (cur_tok!=point_token) scan_int(); + else{@+radix=10;cur_val=0; + } + if (cur_tok==continental_point_token) cur_tok=point_token; + if ((radix==10)&&(cur_tok==point_token)) @<Scan decimal fraction@>; + } + } +if (cur_val < 0) /*in this case |f==0|*/ + {@+negative=!negative;negate(cur_val); + } +@<Scan units and set |cur_val| to $x\cdot(|cur_val|+f/2^{16})$, where there +are |x| sp per unit; |goto attach_sign| if the units are internal@>; +@<Scan an optional space@>; +attach_sign: if (arith_error||(abs(cur_val) >= 010000000000)) + @<Report that this dimension is out of range@>; +if (negative) negate(cur_val); +} + +@ @<Fetch an internal dimension and |goto attach_sign|...@>= +if (mu) + {@+scan_something_internal(mu_val, false); + @<Coerce glue to a dimension@>; + if (cur_val_level==mu_val) goto attach_sign; + if (cur_val_level!=int_val) mu_error(); + } +else{@+scan_something_internal(dimen_val, false); + if (cur_val_level==dimen_val) goto attach_sign; + } + +@ @<Local variables for dimension calculations@>= +int @!num, @!denom; /*conversion ratio for the scanned units*/ +int @!k, @!kk; /*number of digits in a decimal fraction*/ +pointer @!p, @!q; /*top of decimal digit stack*/ +scaled @!v; /*an internal dimension*/ +int @!save_cur_val; /*temporary storage of |cur_val|*/ + +@ The following code is executed when |scan_something_internal| was +called asking for |mu_val|, when we really wanted a ``mudimen'' instead +of ``muglue.'' + +@<Coerce glue to a dimension@>= +if (cur_val_level >= glue_val) + {@+v=width(cur_val);delete_glue_ref(cur_val);cur_val=v; + } + +@ When the following code is executed, we have |cur_tok==point_token|, but this +token has been backed up using |back_input|; we must first discard it. + +It turns out that a decimal point all by itself is equivalent to `\.{0.0}'. +Let's hope people don't use that fact. + +@<Scan decimal fraction@>= +{@+k=0;p=null;get_token(); /*|point_token| is being re-scanned*/ +loop@+{@+get_x_token(); + if ((cur_tok > zero_token+9)||(cur_tok < zero_token)) goto done1; + if (k < 17) /*digits for |k >= 17| cannot affect the result*/ + {@+q=get_avail();link(q)=p;info(q)=cur_tok-zero_token; + p=q;incr(k); + } + } +done1: for (kk=k; kk>=1; kk--) + {@+dig[kk-1]=info(p);q=p;p=link(p);free_avail(q); + } +f=round_decimals(k); +if (cur_cmd!=spacer) back_input(); +} + +@ Now comes the harder part: At this point in the program, |cur_val| is a +nonnegative integer and $f/2^{16}$ is a nonnegative fraction less than 1; +we want to multiply the sum of these two quantities by the appropriate +factor, based on the specified units, in order to produce a |scaled| +result, and we want to do the calculation with fixed point arithmetic that +does not overflow. + +@<Scan units and set |cur_val| to $x\cdot(|cur_val|+f/2^{16})$...@>= +if (inf) @<Scan for \(f)\.{fil} units; |goto attach_fraction| if found@>; +@<Scan for \(u)units that are internal dimensions; |goto attach_sign| with +|cur_val| set if found@>; +if (mu) @<Scan for \(m)\.{mu} units and |goto attach_fraction|@>; +if (scan_keyword("true")) @<Adjust \(f)for the magnification ratio@>; +@.true@> +if (scan_keyword("pt")) goto attach_fraction; /*the easy case*/ +@.pt@> +@<Scan for \(a)all other units and adjust |cur_val| and |f| accordingly; |goto +done| in the case of scaled points@>; +attach_fraction: if (cur_val >= 040000) arith_error=true; +else cur_val=cur_val*unity+f; +done: + +@ A specification like `\.{filllll}' or `\.{fill L L L}' will lead to two +error messages (one for each additional keyword \.{"l"}). + +@<Scan for \(f)\.{fil} units...@>= +if (scan_keyword("fil")) +@.fil@> + {@+cur_order=fil; + while (scan_keyword("l")) + {@+if (cur_order==filll) + {@+print_err("Illegal unit of measure ("); +@.Illegal unit of measure@> + print("replaced by filll)"); + help1("I dddon't go any higher than filll.");error(); + } + else incr(cur_order); + } + goto attach_fraction; + } + +@ @<Scan for \(u)units that are internal dimensions...@>= +save_cur_val=cur_val; +@<Get the next non-blank non-call...@>; +if ((cur_cmd < min_internal)||(cur_cmd > max_internal)) back_input(); +else{@+if (mu) + {@+scan_something_internal(mu_val, false);@<Coerce glue...@>; + if (cur_val_level!=mu_val) mu_error(); + } + else scan_something_internal(dimen_val, false); + v=cur_val;goto found; + } +if (mu) goto not_found; +if (scan_keyword("em")) v=(@<The em width for |cur_font|@>); +@.em@> +else if (scan_keyword("ex")) v=(@<The x-height for |cur_font|@>); +@.ex@> +else goto not_found; +@<Scan an optional space@>; +found: cur_val=nx_plus_y(save_cur_val, v, xn_over_d(v, f, 0200000)); +goto attach_sign; +not_found: + +@ @<Scan for \(m)\.{mu} units and |goto attach_fraction|@>= +if (scan_keyword("mu")) goto attach_fraction; +@.mu@> +else{@+print_err("Illegal unit of measure (");print("mu inserted)"); +@.Illegal unit of measure@> + help4("The unit of measurement in math glue must be mu.",@/ + "To recover gracefully from this error, it's best to",@/ + "delete the erroneous units; e.g., type `2' to delete",@/ + "two letters. (See Chapter 27 of The TeXbook.)"); +@:TeXbook}{\sl The \TeX book@> + error();goto attach_fraction; + } + +@ @<Adjust \(f)for the magnification ratio@>= +{@+prepare_mag(); +if (mag!=1000) + {@+cur_val=xn_over_d(cur_val, 1000, mag); + f=(1000*f+0200000*rem)/mag; + cur_val=cur_val+(f/0200000);f=f%0200000; + } +} + +@ The necessary conversion factors can all be specified exactly as +fractions whose numerator and denominator sum to 32768 or less. +According to the definitions here, $\rm2660\,dd\approx1000.33297\,mm$; +this agrees well with the value $\rm1000.333\,mm$ cited by Bosshard +@^Bosshard, Hans Rudolf@> +in {\sl Technische Grundlagen zur Satzherstellung\/} (Bern, 1980). + +@d set_conversion(A, B) @+{@+num=A;denom=B;} + +@<Scan for \(a)all other units and adjust |cur_val| and |f|...@>= +if (scan_keyword("in")) set_conversion(7227, 100)@; +@.in@> +else if (scan_keyword("pc")) set_conversion(12, 1)@; +@.pc@> +else if (scan_keyword("cm")) set_conversion(7227, 254)@; +@.cm@> +else if (scan_keyword("mm")) set_conversion(7227, 2540)@; +@.mm@> +else if (scan_keyword("bp")) set_conversion(7227, 7200)@; +@.bp@> +else if (scan_keyword("dd")) set_conversion(1238, 1157)@; +@.dd@> +else if (scan_keyword("cc")) set_conversion(14856, 1157)@; +@.cc@> +else if (scan_keyword("sp")) goto done; +@.sp@> +else@<Complain about unknown unit and |goto done2|@>; +cur_val=xn_over_d(cur_val, num, denom); +f=(num*f+0200000*rem)/denom;@/ +cur_val=cur_val+(f/0200000);f=f%0200000; +done2: + +@ @<Complain about unknown unit...@>= +{@+print_err("Illegal unit of measure (");print("pt inserted)"); +@.Illegal unit of measure@> +help6("Dimensions can be in units of em, ex, in, pt, pc,",@/ + "cm, mm, dd, cc, bp, or sp; but yours is a new one!",@/ + "I'll assume that you meant to say pt, for printer's points.",@/ + "To recover gracefully from this error, it's best to",@/ + "delete the erroneous units; e.g., type `2' to delete",@/ + "two letters. (See Chapter 27 of The TeXbook.)"); +@:TeXbook}{\sl The \TeX book@> +error();goto done2; +} + + +@ @<Report that this dimension is out of range@>= +{@+print_err("Dimension too large"); +@.Dimension too large@> +help2("I can't work with sizes bigger than about 19 feet.",@/ + "Continue and I'll use the largest value I can.");@/ +error();cur_val=max_dimen;arith_error=false; +} + +@ The final member of \TeX's value-scanning trio is |scan_glue|, which +makes |cur_val| point to a glue specification. The reference count of that +glue spec will take account of the fact that |cur_val| is pointing to~it. + +The |level| parameter should be either |glue_val| or |mu_val|. + +Since |scan_dimen| was so much more complex than |scan_int|, we might expect +|scan_glue| to be even worse. But fortunately, it is very simple, since +most of the work has already been done. + +@p static void scan_glue(small_number @!level) + /*sets |cur_val| to a glue spec pointer*/ +{@+ +bool negative; /*should the answer be negated?*/ +pointer @!q; /*new glue specification*/ +bool @!mu; /*does |level==mu_val|?*/ +mu=(level==mu_val);@<Get the next non-blank non-sign...@>; +if ((cur_cmd >= min_internal)&&(cur_cmd <= max_internal)) + {@+scan_something_internal(level, negative); + if (cur_val_level >= glue_val) + {@+if (cur_val_level!=level) mu_error(); + return; + } + if (cur_val_level==int_val) scan_dimen(mu, false, true); + else if (level==mu_val) mu_error(); + } +else{@+back_input();scan_dimen(mu, false, false); + if (negative) negate(cur_val); + } +@<Create a new glue specification whose width is |cur_val|; scan for its stretch +and shrink components@>; +} +@# +@<Declare procedures needed for expressions@>@; + +@ @<Create a new glue specification whose width is |cur_val|...@>= +q=new_spec(zero_glue);width(q)=cur_val; +if (scan_keyword("plus")) +@.plus@> + {@+scan_dimen(mu, true, false); + stretch(q)=cur_val;stretch_order(q)=cur_order; + } +if (scan_keyword("minus")) +@.minus@> + {@+scan_dimen(mu, true, false); + shrink(q)=cur_val;shrink_order(q)=cur_order; + } +cur_val=q + +@ Here's a similar procedure that returns a pointer to a rule node. This +routine is called just after \TeX\ has seen \.{\\hrule} or \.{\\vrule}; +therefore |cur_cmd| will be either |hrule| or |vrule|. The idea is to store +the default rule dimensions in the node, then to override them if +`\.{height}' or `\.{width}' or `\.{depth}' specifications are +found (in any order). + +@d default_rule 26214 /*0.4\thinspace pt*/ + +@p static pointer scan_rule_spec(void) +{@+ +pointer q; /*the rule node being created*/ +q=new_rule(); /*|width|, |depth|, and |height| all equal |null_flag| now*/ +if (cur_cmd==vrule) width(q)=default_rule; +else{@+height(q)=default_rule;depth(q)=0; + } +reswitch: if (scan_keyword("width")) +@.width@> + {@+scan_normal_dimen;width(q)=cur_val;goto reswitch; + } +if (scan_keyword("height")) +@.height@> + {@+scan_normal_dimen;height(q)=cur_val;goto reswitch; + } +if (scan_keyword("depth")) +@.depth@> + {@+scan_normal_dimen;depth(q)=cur_val;goto reswitch; + } +return q; +} + +@* Building token lists. +The token lists for macros and for other things like \.{\\mark} and \.{\\output} +and \.{\\write} are produced by a procedure called |scan_toks|. + +Before we get into the details of |scan_toks|, let's consider a much +simpler task, that of converting the current string into a token list. +The |str_toks| function does this; it classifies spaces as type |spacer| +and everything else as type |other_char|. + +The token list created by |str_toks| begins at |link(temp_head)| and ends +at the value |p| that is returned. (If |p==temp_head|, the list is empty.) + +@p @t\4@>@<Declare \eTeX\ procedures for token lists@>@;@/ +static pointer str_toks(pool_pointer @!b) + /*converts |str_pool[b dotdot pool_ptr-1]| to a token list*/ +{@+pointer p; /*tail of the token list*/ +pointer @!q; /*new node being added to the token list via |store_new_token|*/ +halfword @!t; /*token being appended*/ +pool_pointer @!k; /*index into |str_pool|*/ +str_room(1); +p=temp_head;link(p)=null;k=b; +while (k < pool_ptr) + {@+t=so(str_pool[k]); + if (t==' ') t=space_token; + else t=other_token+t; + fast_store_new_token(t); + incr(k); + } +pool_ptr=b;return p; +} + +@ The main reason for wanting |str_toks| is the next function, +|the_toks|, which has similar input/output characteristics. + +This procedure is supposed to scan something like `\.{\\skip\\count12}', +i.e., whatever can follow `\.{\\the}', and it constructs a token list +containing something like `\.{-3.0pt minus 0.5fill}'. + +@p static pointer the_toks(void) +{@+ +int old_setting; /*holds |selector| setting*/ +pointer @!p, @!q, @!r; /*used for copying a token list*/ +pool_pointer @!b; /*base of temporary string*/ +small_number @!c; /*value of |cur_chr|*/ +@<Handle \.{\\unexpanded} or \.{\\detokenize} and |return|@>;@/ +get_x_token();scan_something_internal(tok_val, false); +if (cur_val_level >= ident_val) @<Copy the token list@>@; +else{@+old_setting=selector;selector=new_string;b=pool_ptr; + switch (cur_val_level) { + case int_val: print_int(cur_val);@+break; + case dimen_val: {@+print_scaled(cur_val);print("pt"); + } @+break; + case glue_val: {@+print_spec(cur_val,"pt");delete_glue_ref(cur_val); + } @+break; + case mu_val: {@+print_spec(cur_val,"mu");delete_glue_ref(cur_val); + } + } /*there are no other cases*/ + selector=old_setting;return str_toks(b); + } +} + +@ @<Copy the token list@>= +{@+p=temp_head;link(p)=null; +if (cur_val_level==ident_val) store_new_token(cs_token_flag+cur_val)@; +else if (cur_val!=null) + {@+r=link(cur_val); /*do not copy the reference count*/ + while (r!=null) + {@+fast_store_new_token(info(r));r=link(r); + } + } +return p; +} + +@ Here's part of the |expand| subroutine that we are now ready to complete: + +@p static void ins_the_toks(void) +{@+link(garbage)=the_toks();ins_list(link(temp_head)); +} + +@ The primitives \.{\\number}, \.{\\romannumeral}, \.{\\string}, \.{\\meaning}, +\.{\\fontname}, and \.{\\jobname} are defined as follows. + +@d number_code 0 /*command code for \.{\\number}*/ +@d roman_numeral_code 1 /*command code for \.{\\romannumeral}*/ +@d string_code 2 /*command code for \.{\\string}*/ +@d meaning_code 3 /*command code for \.{\\meaning}*/ +@d font_name_code 4 /*command code for \.{\\fontname}*/ +@d etex_convert_base 5 /*base for \eTeX's command codes*/ +@d eTeX_revision_code etex_convert_base /*command code for \.{\\eTeXrevision}*/ +@d etex_convert_codes (etex_convert_base+1) /*end of \eTeX's command codes*/ +@d eTeX_last_convert_cmd_mod etex_convert_codes /* prote codes follow */ + + +@# +@d job_name_code pdftex_convert_codes /*command code for \.{\\jobname}*/ + +@<Put each...@>= +primitive("number", convert, number_code);@/ +@!@:number\_}{\.{\\number} primitive@> +primitive("romannumeral", convert, roman_numeral_code);@/ +@!@:roman\_numeral\_}{\.{\\romannumeral} primitive@> +primitive("string", convert, string_code);@/ +@!@:string\_}{\.{\\string} primitive@> +primitive("meaning", convert, meaning_code);@/ +@!@:meaning\_}{\.{\\meaning} primitive@> +primitive("fontname", convert, font_name_code);@/ +@!@:font\_name\_}{\.{\\fontname} primitive@> +primitive("jobname", convert, job_name_code);@/ +@!@:job\_name\_}{\.{\\jobname} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case convert: switch (chr_code) { + case number_code: print_esc("number");@+break; + case roman_numeral_code: print_esc("romannumeral");@+break; + case string_code: print_esc("string");@+break; + case meaning_code: print_esc("meaning");@+break; + case font_name_code: print_esc("fontname");@+break; + case job_name_code: print_esc("jobname");@+break; + case eTeX_revision_code: print_esc("eTeXrevision");@+break; + @/@<Cases of |convert| for |print_cmd_chr|@>@/ + } @+break; + +@ The procedure |conv_toks| uses |str_toks| to insert the token list +for |convert| functions into the scanner; `\.{\\outer}' control sequences +are allowed to follow `\.{\\string}' and `\.{\\meaning}'. + +@p static void scan_pdf_ext_toks(void); +static void conv_toks(void) +{@+int old_setting; /*holds |selector| setting*/ +int @!c; /*desired type of conversion*/ +small_number @!save_scanner_status; /*|scanner_status| upon entry*/ +pool_pointer @!b; /*base of temporary string*/ +int @!i, @!k, @!l; /*general purpose index*/ +pool_pointer @!m, @!n; /*general purpose pool pointer*/ +bool @!r; /*general purpose refraction i.e. changing the way*/ +str_number @!s, @!t; /*general purpose; de dicto*/ +c=cur_chr;@<Scan the argument for command |c|@>; +old_setting=selector;selector=new_string;b=pool_ptr; +@<Print the result of command |c|@>; +selector=old_setting;link(garbage)=str_toks(b);ins_list(link(temp_head)); +} + +@ @<Scan the argument for command |c|@>= +switch (c) { +case number_code: case roman_numeral_code: scan_int();@+break; +case string_code: case meaning_code: {@+save_scanner_status=scanner_status; + scanner_status=normal;get_token();scanner_status=save_scanner_status; + } @+break; +case font_name_code: scan_font_ident();@+break; +case job_name_code: if (job_name==0) open_log_file();@+break; +case eTeX_revision_code: do_nothing;@+break; +@/@<Cases of `Scan the argument for command |c|'@>@/ +} /*there are no other cases*/ + +@ @<Print the result of command |c|@>= +switch (c) { +case number_code: print_int(cur_val);@+break; +case roman_numeral_code: print_roman_int(cur_val);@+break; +case string_code: if (cur_cs!=0) sprint_cs(cur_cs); + else print_char(cur_chr);@+break; +case meaning_code: print_meaning();@+break; +case font_name_code: {@+printn(font_name[cur_val]); + if (font_size[cur_val]!=font_dsize[cur_val]) + {@+print(" at ");print_scaled(font_size[cur_val]); + print("pt"); + } + } @+break; +case eTeX_revision_code: print(eTeX_revision);@+break; +case job_name_code: printn(job_name);@+break; +@/@<Cases of `Print the result of command |c|'@>@/ +} /*there are no other cases*/ + +@ Now we can't postpone the difficulties any longer; we must bravely tackle +|scan_toks|. This function returns a pointer to the tail of a new token +list, and it also makes |def_ref| point to the reference count at the +head of that list. + +There are two boolean parameters, |macro_def| and |xpand|. If |macro_def| +is true, the goal is to create the token list for a macro definition; +otherwise the goal is to create the token list for some other \TeX\ +primitive: \.{\\mark}, \.{\\output}, \.{\\everypar}, \.{\\lowercase}, +\.{\\uppercase}, \.{\\message}, \.{\\errmessage}, \.{\\write}, or +\.{\\special}. In the latter cases a left brace must be scanned next; this +left brace will not be part of the token list, nor will the matching right +brace that comes at the end. If |xpand| is false, the token list will +simply be copied from the input using |get_token|. Otherwise all expandable +tokens will be expanded until unexpandable tokens are left, except that +the results of expanding `\.{\\the}' are not expanded further. +If both |macro_def| and |xpand| are true, the expansion applies +only to the macro body (i.e., to the material following the first +|left_brace| character). + +The value of |cur_cs| when |scan_toks| begins should be the |eqtb| +address of the control sequence to display in ``runaway'' error +messages. + +@p static pointer scan_toks(bool @!macro_def, bool @!xpand) +{@+ +halfword t; /*token representing the highest parameter number*/ +halfword @!s; /*saved token*/ +pointer @!p; /*tail of the token list being built*/ +pointer @!q; /*new node being added to the token list via |store_new_token|*/ +halfword @!unbalance; /*number of unmatched left braces*/ +halfword @!hash_brace; /*possible `\.{\#\{}' token*/ +if (macro_def) scanner_status=defining; +@+else scanner_status=absorbing; +warning_index=cur_cs;def_ref=get_avail();token_ref_count(def_ref)=null; +p=def_ref;hash_brace=0;t=zero_token; +if (macro_def) @<Scan and build the parameter part of the macro definition@>@; +else scan_left_brace(); /*remove the compulsory left brace*/ +@<Scan and build the body of the token list; |goto found| when finished@>; +found: scanner_status=normal; +if (hash_brace!=0) store_new_token(hash_brace); +return p; +} +@t\4@>@<Declare \Prote\ procedures for token lists@>@;@/ + +@ @<Scan and build the parameter part...@>= +{@+loop{@+resume: get_token(); /*set |cur_cmd|, |cur_chr|, |cur_tok|*/ + if (cur_tok < right_brace_limit) goto done1; + if (cur_cmd==mac_param) + @<If the next character is a parameter number, make |cur_tok| a |match| +token; but if it is a left brace, store `|left_brace|, |end_match|', set |hash_brace|, +and |goto done|@>; + store_new_token(cur_tok); + } +done1: store_new_token(end_match_token); +if (cur_cmd==right_brace) + @<Express shock at the missing left brace; |goto found|@>; +done: ;} + +@ @<Express shock...@>= +{@+print_err("Missing { inserted");incr(align_state); +@.Missing \{ inserted@> +help2("Where was the left brace? You said something like `\\def\\a}',",@/ + "which I'm going to interpret as `\\def\\a{}'.");error();goto found; +} + +@ @<If the next character is a parameter number...@>= +{@+s=match_token+cur_chr;get_token(); +if (cur_tok < left_brace_limit) + {@+hash_brace=cur_tok; + store_new_token(cur_tok);store_new_token(end_match_token); + goto done; + } +if (t==zero_token+9) + {@+print_err("You already have nine parameters"); +@.You already have nine...@> + help2("I'm going to ignore the # sign you just used,",@/ + "as well as the token that followed it.");error();goto resume; + } +else{@+incr(t); + if (cur_tok!=t) + {@+print_err("Parameters must be numbered consecutively"); +@.Parameters...consecutively@> + help2("I've inserted the digit you should have used after the #.",@/ + "Type `1' to delete what you did use.");back_error(); + } + cur_tok=s; + } +} + +@ @<Scan and build the body of the token list; |goto found| when finished@>= +unbalance=1; +loop@+{@+if (xpand) @<Expand the next part of the input@>@; + else get_token(); + if (cur_tok < right_brace_limit) + if (cur_cmd < right_brace) incr(unbalance); + else{@+decr(unbalance); + if (unbalance==0) goto found; + } + else if (cur_cmd==mac_param) + if (macro_def) @<Look for parameter number or \.{\#\#}@>; + store_new_token(cur_tok); + } + +@ Here we insert an entire token list created by |the_toks| without +expanding it further. + +@<Expand the next part of the input@>= +{@+loop{@+get_next(); + if (cur_cmd >= call) + if (info(link(cur_chr))==protected_token) + {@+cur_cmd=relax;cur_chr=no_expand_flag; + } + if (cur_cmd <= max_command) goto done2; + if (cur_cmd!=the) expand(); + else{@+q=the_toks(); + if (link(temp_head)!=null) + {@+link(p)=link(temp_head);p=q; + } + } + } +done2: x_token(); +} + +@ @<Look for parameter number...@>= +{@+s=cur_tok; +if (xpand) get_x_token();else get_token(); +if (cur_cmd!=mac_param) + if ((cur_tok <= zero_token)||(cur_tok > t)) + {@+print_err("Illegal parameter number in definition of "); +@.Illegal parameter number...@> + sprint_cs(warning_index); + help3("You meant to type ## instead of #, right?",@/ + "Or maybe a } was forgotten somewhere earlier, and things",@/ + "are all screwed up? I'm going to assume that you meant ##."); + back_error();cur_tok=s; + } + else cur_tok=out_param_token-'0'+cur_chr; +} + +@ Another way to create a token list is via the \.{\\read} command. The +sixteen files potentially usable for reading appear in the following +global variables. The value of |read_open[n]| will be |closed| if +stream number |n| has not been opened or if it has been fully read; +|just_open| if an \.{\\openin} but not a \.{\\read} has been done; +and |normal| if it is open and ready to read the next line. + +@d closed 2 /*not open, or at end of file*/ +@d just_open 1 /*newly opened, first line not yet read*/ + +@<Glob...@>= +static alpha_file @!read_file[16]; /*used for \.{\\read}*/ +static int8_t @!read_open[17]; /*state of |read_file[n]|*/ + +@ @<Set init...@>= +for (k=0; k<=16; k++) read_open[k]=closed; + +@ The |read_toks| procedure constructs a token list like that for any +macro definition, and makes |cur_val| point to it. Parameter |r| points +to the control sequence that will receive this token list. + +@p static void read_toks(int @!n, pointer @!r, halfword @!j) +{@+ +pointer p; /*tail of the token list*/ +pointer @!q; /*new node being added to the token list via |store_new_token|*/ +int @!s; /*saved value of |align_state|*/ +small_number @!m; /*stream number*/ +scanner_status=defining;warning_index=r; +def_ref=get_avail();token_ref_count(def_ref)=null; +p=def_ref; /*the reference count*/ +store_new_token(end_match_token); +if ((n < 0)||(n > 15)) m=16;@+else m=n; +s=align_state;align_state=1000000; /*disable tab marks, etc.*/ +@/do@+{@<Input and store tokens from the next line of the file@>; +}@+ while (!(align_state==1000000)); +cur_val=def_ref;scanner_status=normal;align_state=s; +} + +@ @<Input and store tokens from the next line of the file@>= +begin_file_reading();name=m+1; +if (read_open[m]==closed) @<Input for \.{\\read} from the terminal@>; +else if (read_open[m]==just_open) @<Input the first line of |read_file[m]|@>@; +else@<Input the next line of |read_file[m]|@>; +limit=last; +if (end_line_char_inactive) decr(limit); +else buffer[limit]=end_line_char; +first=limit+1;loc=start;state=new_line;@/ +@<Handle \.{\\readline} and |goto done|@>;@/ +loop@+{@+get_token(); + if (cur_tok==0) goto done; + /*|cur_cmd==cur_chr==0| will occur at the end of the line*/ + if (align_state < 1000000) /*unmatched `\.\}' aborts the line*/ + {@+@/do@+{get_token();}@+ while (!(cur_tok==0)); + align_state=1000000;goto done; + } + store_new_token(cur_tok); + } +done: end_file_reading() + +@ Here we input on-line into the |buffer| array, prompting the user explicitly +if |n >= 0|. The value of |n| is set negative so that additional prompts +will not be given in the case of multi-line input. + +@<Input for \.{\\read} from the terminal@>= +if (interaction > nonstop_mode) + if (n < 0) prompt_input("")@; + else{@+wake_up_terminal; + print_ln();sprint_cs(r);prompt_input("=");n=-1; + } +else fatal_error("*** (cannot \\read from terminal in nonstop modes)") +@.cannot \\read@> + +@ The first line of a file must be treated specially, since |input_ln| +must be told not to start with |get|. +@^system dependencies@> + +@<Input the first line of |read_file[m]|@>= +if (input_ln(&read_file[m], false)) read_open[m]=normal; +else{@+a_close(&read_file[m]);read_open[m]=closed; + } + +@ An empty line is appended at the end of a |read_file|. +@^empty line at end of file@> + +@<Input the next line of |read_file[m]|@>= +{@+if (!input_ln(&read_file[m], true)) + {@+a_close(&read_file[m]);read_open[m]=closed; + if (align_state!=1000000) + {@+runaway(); + print_err("File ended within ");print_esc("read"); +@.File ended within \\read@> + help1("This \\read has unbalanced braces."); + align_state=1000000;limit=0;error(); + } + } +} + +@* Conditional processing. +We consider now the way \TeX\ handles various kinds of \.{\\if} commands. + +@d unless_code 32 /*amount added for `\.{\\unless}' prefix*/ +@# +@d if_char_code 0 /* `\.{\\if}' */ +@d if_cat_code 1 /* `\.{\\ifcat}' */ +@d if_int_code 2 /* `\.{\\ifnum}' */ +@d if_dim_code 3 /* `\.{\\ifdim}' */ +@d if_odd_code 4 /* `\.{\\ifodd}' */ +@d if_vmode_code 5 /* `\.{\\ifvmode}' */ +@d if_hmode_code 6 /* `\.{\\ifhmode}' */ +@d if_mmode_code 7 /* `\.{\\ifmmode}' */ +@d if_inner_code 8 /* `\.{\\ifinner}' */ +@d if_void_code 9 /* `\.{\\ifvoid}' */ +@d if_hbox_code 10 /* `\.{\\ifhbox}' */ +@d if_vbox_code 11 /* `\.{\\ifvbox}' */ +@d ifx_code 12 /* `\.{\\ifx}' */ +@d if_eof_code 13 /* `\.{\\ifeof}' */ +@d if_true_code 14 /* `\.{\\iftrue}' */ +@d if_false_code 15 /* `\.{\\iffalse}' */ +@d if_case_code 16 /* `\.{\\ifcase}' */ + +@<Put each...@>= +primitive("if", if_test, if_char_code); +@!@:if\_char\_}{\.{\\if} primitive@> +primitive("ifcat", if_test, if_cat_code); +@!@:if\_cat\_code\_}{\.{\\ifcat} primitive@> +primitive("ifnum", if_test, if_int_code); +@!@:if\_int\_}{\.{\\ifnum} primitive@> +primitive("ifdim", if_test, if_dim_code); +@!@:if\_dim\_}{\.{\\ifdim} primitive@> +primitive("ifodd", if_test, if_odd_code); +@!@:if\_odd\_}{\.{\\ifodd} primitive@> +primitive("ifvmode", if_test, if_vmode_code); +@!@:if\_vmode\_}{\.{\\ifvmode} primitive@> +primitive("ifhmode", if_test, if_hmode_code); +@!@:if\_hmode\_}{\.{\\ifhmode} primitive@> +primitive("ifmmode", if_test, if_mmode_code); +@!@:if\_mmode\_}{\.{\\ifmmode} primitive@> +primitive("ifinner", if_test, if_inner_code); +@!@:if\_inner\_}{\.{\\ifinner} primitive@> +primitive("ifvoid", if_test, if_void_code); +@!@:if\_void\_}{\.{\\ifvoid} primitive@> +primitive("ifhbox", if_test, if_hbox_code); +@!@:if\_hbox\_}{\.{\\ifhbox} primitive@> +primitive("ifvbox", if_test, if_vbox_code); +@!@:if\_vbox\_}{\.{\\ifvbox} primitive@> +primitive("ifx", if_test, ifx_code); +@!@:ifx\_}{\.{\\ifx} primitive@> +primitive("ifeof", if_test, if_eof_code); +@!@:if\_eof\_}{\.{\\ifeof} primitive@> +primitive("iftrue", if_test, if_true_code); +@!@:if\_true\_}{\.{\\iftrue} primitive@> +primitive("iffalse", if_test, if_false_code); +@!@:if\_false\_}{\.{\\iffalse} primitive@> +primitive("ifcase", if_test, if_case_code); +@!@:if\_case\_}{\.{\\ifcase} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case if_test: {@+if (chr_code >= unless_code) print_esc("unless"); +switch (chr_code%unless_code) { + case if_cat_code: print_esc("ifcat");@+break; + case if_int_code: print_esc("ifnum");@+break; + case if_dim_code: print_esc("ifdim");@+break; + case if_odd_code: print_esc("ifodd");@+break; + case if_vmode_code: print_esc("ifvmode");@+break; + case if_hmode_code: print_esc("ifhmode");@+break; + case if_mmode_code: print_esc("ifmmode");@+break; + case if_inner_code: print_esc("ifinner");@+break; + case if_void_code: print_esc("ifvoid");@+break; + case if_hbox_code: print_esc("ifhbox");@+break; + case if_vbox_code: print_esc("ifvbox");@+break; + case ifx_code: print_esc("ifx");@+break; + case if_eof_code: print_esc("ifeof");@+break; + case if_true_code: print_esc("iftrue");@+break; + case if_false_code: print_esc("iffalse");@+break; + case if_case_code: print_esc("ifcase");@+break; + @/@<Cases of |if_test| for |print_cmd_chr|@>@/ + default:print_esc("if"); + } +} @+break; + +@ Conditions can be inside conditions, and this nesting has a stack +that is independent of the |save_stack|. + +Four global variables represent the top of the condition stack: +|cond_ptr| points to pushed-down entries, if any; |if_limit| specifies +the largest code of a |fi_or_else| command that is syntactically legal; +|cur_if| is the name of the current type of conditional; and |if_line| +is the line number at which it began. + +If no conditions are currently in progress, the condition stack has the +special state |cond_ptr==null|, |if_limit==normal|, |cur_if==0|, |if_line==0|. +Otherwise |cond_ptr| points to a two-word node; the |type|, |subtype|, and +|link| fields of the first word contain |if_limit|, |cur_if|, and +|cond_ptr| at the next level, and the second word contains the +corresponding |if_line|. + +@d if_node_size 2 /*number of words in stack entry for conditionals*/ +@d if_line_field(A) mem[A+1].i +@d if_code 1 /*code for \.{\\if...} being evaluated*/ +@d fi_code 2 /*code for \.{\\fi}*/ +@d else_code 3 /*code for \.{\\else}*/ +@d or_code 4 /*code for \.{\\or}*/ + +@<Glob...@>= +static pointer @!cond_ptr; /*top of the condition stack*/ +static int @!if_limit; /*upper bound on |fi_or_else| codes*/ +static small_number @!cur_if; /*type of conditional being worked on*/ +static int @!if_line; /*line where that conditional began*/ + +@ @<Set init...@>= +cond_ptr=null;if_limit=normal;cur_if=0;if_line=0; + +@ @<Put each...@>= +primitive("fi", fi_or_else, fi_code); +@!@:fi\_}{\.{\\fi} primitive@> +text(frozen_fi)=text(cur_val);eqtb[frozen_fi]=eqtb[cur_val]; +primitive("or", fi_or_else, or_code); +@!@:or\_}{\.{\\or} primitive@> +primitive("else", fi_or_else, else_code); +@!@:else\_}{\.{\\else} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case fi_or_else: if (chr_code==fi_code) print_esc("fi"); + else if (chr_code==or_code) print_esc("or"); + else print_esc("else");@+break; + +@ When we skip conditional text, we keep track of the line number +where skipping began, for use in error messages. + +@<Glob...@>= +static int @!skip_line; /*skipping began here*/ + +@ Here is a procedure that ignores text until coming to an \.{\\or}, +\.{\\else}, or \.{\\fi} at the current level of $\.{\\if}\ldots\.{\\fi}$ +nesting. After it has acted, |cur_chr| will indicate the token that +was found, but |cur_tok| will not be set (because this makes the +procedure run faster). + +@p static void pass_text(void) +{@+ +int l; /*level of $\.{\\if}\ldots\.{\\fi}$ nesting*/ +small_number @!save_scanner_status; /*|scanner_status| upon entry*/ +save_scanner_status=scanner_status;scanner_status=skipping;l=0; +skip_line=line; +loop@+{@+get_next(); + if (cur_cmd==fi_or_else) + {@+if (l==0) goto done; + if (cur_chr==fi_code) decr(l); + } + else if (cur_cmd==if_test) incr(l); + } +done: scanner_status=save_scanner_status; +if (tracing_ifs > 0) show_cur_cmd_chr(); +} + +@ When we begin to process a new \.{\\if}, we set |if_limit=if_code|; then +if\/ \.{\\or} or \.{\\else} or \.{\\fi} occurs before the current \.{\\if} +condition has been evaluated, \.{\\relax} will be inserted. +For example, a sequence of commands like `\.{\\ifvoid1\\else...\\fi}' +would otherwise require something after the `\.1'. + +@<Push the condition stack@>= +{@+p=get_node(if_node_size);link(p)=cond_ptr;type(p)=if_limit; +subtype(p)=cur_if;if_line_field(p)=if_line; +cond_ptr=p;cur_if=cur_chr;if_limit=if_code;if_line=line; +} + +@ @<Pop the condition stack@>= +{@+if (if_stack[in_open]==cond_ptr) if_warning(); + /*conditionals possibly not properly nested with files*/ +p=cond_ptr;if_line=if_line_field(p); +cur_if=subtype(p);if_limit=type(p);cond_ptr=link(p); +free_node(p, if_node_size); +} + +@ Here's a procedure that changes the |if_limit| code corresponding to +a given value of |cond_ptr|. + +@p static void change_if_limit(small_number @!l, pointer @!p) +{@+ +pointer q; +if (p==cond_ptr) if_limit=l; /*that's the easy case*/ +else{@+q=cond_ptr; + loop@+{@+if (q==null) confusion("if"); +@:this can't happen if}{\quad if@> + if (link(q)==p) + {@+type(q)=l;return; + } + q=link(q); + } + } +} + +@ A condition is started when the |expand| procedure encounters +an |if_test| command; in that case |expand| reduces to |conditional|, +which is a recursive procedure. +@^recursion@> + +@p static void conditional(void) +{@+ +bool b; /*is the condition true?*/ +int @!r; /*relation to be evaluated*/ +int @!m, @!n; /*to be tested against the second operand*/ +pointer @!p, @!q; /*for traversing token lists in \.{\\ifx} tests*/ +small_number @!save_scanner_status; /*|scanner_status| upon entry*/ +pointer @!save_cond_ptr; /*|cond_ptr| corresponding to this conditional*/ +small_number @!this_if; /*type of this conditional*/ +bool @!is_unless; /*was this if preceded by `\.{\\unless}' ?*/ +if (tracing_ifs > 0) if (tracing_commands <= 1) show_cur_cmd_chr(); +@<Push the condition stack@>;@+save_cond_ptr=cond_ptr; +is_unless=(cur_chr >= unless_code);this_if=cur_chr%unless_code;@/ +@<Either process \.{\\ifcase} or set |b| to the value of a boolean condition@>; +if (is_unless) b=!b; +if (tracing_commands > 1) @<Display the value of |b|@>; +if (b) + {@+change_if_limit(else_code, save_cond_ptr); + return; /*wait for \.{\\else} or \.{\\fi}*/ + } +@<Skip to \.{\\else} or \.{\\fi}, then |goto common_ending|@>; +common_ending: if (cur_chr==fi_code) @<Pop the condition stack@>@; +else if_limit=fi_code; /*wait for \.{\\fi}*/ +} + +@ In a construction like `\.{\\if\\iftrue abc\\else d\\fi}', the first +\.{\\else} that we come to after learning that the \.{\\if} is false is +not the \.{\\else} we're looking for. Hence the following curious +logic is needed. + +@ @<Skip to \.{\\else} or \.{\\fi}...@>= +loop@+{@+pass_text(); + if (cond_ptr==save_cond_ptr) + {@+if (cur_chr!=or_code) goto common_ending; + print_err("Extra ");print_esc("or"); +@.Extra \\or@> + help1("I'm ignoring this; it doesn't match any \\if."); + error(); + } + else if (cur_chr==fi_code) @<Pop the condition stack@>; + } + +@ @<Either process \.{\\ifcase} or set |b|...@>= +switch (this_if) { +case if_char_code: case if_cat_code: @<Test if two characters match@>@;@+break; +case if_int_code: case if_dim_code: @<Test relation between integers or dimensions@>@;@+break; +case if_odd_code: @<Test if an integer is odd@>@;@+break; +case if_vmode_code: b=(abs(mode)==vmode);@+break; +case if_hmode_code: b=(abs(mode)==hmode);@+break; +case if_mmode_code: b=(abs(mode)==mmode);@+break; +case if_inner_code: b=(mode < 0);@+break; +case if_void_code: case if_hbox_code: + case if_vbox_code: @<Test box register status@>@;@+break; +case ifx_code: @<Test if two tokens match@>@;@+break; +case if_eof_code: {@+scan_four_bit_int();b=(read_open[cur_val]==closed); + } @+break; +case if_true_code: b=true;@+break; +case if_false_code: b=false;@+break; +@/@<Cases for |conditional|@>@/ +case if_case_code: @<Select the appropriate case and |return| or |goto common_ending|@>; +} /*there are no other cases*/ + +@ @<Display the value of |b|@>= +{@+begin_diagnostic(); +if (b) print("{true}");@+else print("{false}"); +end_diagnostic(false); +} + +@ Here we use the fact that |'<'|, |'='|, and |'>'| are consecutive ASCII +codes. +@^ASCII code@> + +@<Test relation between integers or dimensions@>= +{@+if (this_if==if_int_code) scan_int();@+else scan_normal_dimen; +n=cur_val;@<Get the next non-blank non-call...@>; +if ((cur_tok >= other_token+'<')&&(cur_tok <= other_token+'>')) + r=cur_tok-other_token; +else{@+print_err("Missing = inserted for "); +@.Missing = inserted@> + print_cmd_chr(if_test, this_if); + help1("I was expecting to see `<', `=', or `>'. Didn't."); + back_error();r='='; + } +if (this_if==if_int_code) scan_int();@+else scan_normal_dimen; +switch (r) { +case '<': b=(n < cur_val);@+break; +case '=': b=(n==cur_val);@+break; +case '>': b=(n > cur_val); +} +} + +@ @<Test if an integer is odd@>= +{@+scan_int();b=odd(cur_val); +} + +@ @<Test box register status@>= +{@+scan_register_num();fetch_box(p); +if (this_if==if_void_code) b=(p==null); +else if (p==null) b=false; +else if (this_if==if_hbox_code) b=(type(p)==hlist_node); +else b=(type(p)==vlist_node); +} + +@ An active character will be treated as category 13 following +\.{\\if\\noexpand} or following \.{\\ifcat\\noexpand}. We use the fact that +active characters have the smallest tokens, among all control sequences. + +@d get_x_token_or_active_char @t@>@; + {@+get_x_token(); + if (cur_cmd==relax) if (cur_chr==no_expand_flag) + {@+cur_cmd=active_char; + cur_chr=cur_tok-cs_token_flag-active_base; + } + } + +@<Test if two characters match@>= +{@+get_x_token_or_active_char; +if ((cur_cmd > active_char)||(cur_chr > 255)) /*not a character*/ + {@+m=relax;n=256; + } +else{@+m=cur_cmd;n=cur_chr; + } +get_x_token_or_active_char; +if ((cur_cmd > active_char)||(cur_chr > 255)) + {@+cur_cmd=relax;cur_chr=256; + } +if (this_if==if_char_code) b=(n==cur_chr);@+else b=(m==cur_cmd); +} + +@ Note that `\.{\\ifx}' will declare two macros different if one is \\{long} +or \\{outer} and the other isn't, even though the texts of the macros are +the same. + +We need to reset |scanner_status|, since \.{\\outer} control sequences +are allowed, but we might be scanning a macro definition or preamble. + +@<Test if two tokens match@>= +{@+save_scanner_status=scanner_status;scanner_status=normal; +get_next();n=cur_cs;p=cur_cmd;q=cur_chr; +get_next();if (cur_cmd!=p) b=false; +else if (cur_cmd < call) b=(cur_chr==q); +else@<Test if two macro texts match@>; +scanner_status=save_scanner_status; +} + +@ Note also that `\.{\\ifx}' decides that macros \.{\\a} and \.{\\b} are +different in examples like this: +$$\vbox{\halign{\.{#}\hfil&\qquad\.{#}\hfil\cr + {}\\def\\a\{\\c\}& + {}\\def\\c\{\}\cr + {}\\def\\b\{\\d\}& + {}\\def\\d\{\}\cr}}$$ + +@<Test if two macro texts match@>= +{@+p=link(cur_chr);q=link(equiv(n)); /*omit reference counts*/ +if (p==q) b=true; +else{@+while ((p!=null)&&(q!=null)) + if (info(p)!=info(q)) p=null; + else{@+p=link(p);q=link(q); + } + b=((p==null)&&(q==null)); + } +} + +@ @<Select the appropriate case and |return| or |goto common_ending|@>= +{@+scan_int();n=cur_val; /*|n| is the number of cases to pass*/ +if (tracing_commands > 1) + {@+begin_diagnostic();print("{case ");print_int(n);print_char('}'); + end_diagnostic(false); + } +while (n!=0) + {@+pass_text(); + if (cond_ptr==save_cond_ptr) + if (cur_chr==or_code) decr(n); + else goto common_ending; + else if (cur_chr==fi_code) @<Pop the condition stack@>; + } +change_if_limit(or_code, save_cond_ptr); +return; /*wait for \.{\\or}, \.{\\else}, or \.{\\fi}*/ +} + +@ The processing of conditionals is complete except for the following +code, which is actually part of |expand|. It comes into play when +\.{\\or}, \.{\\else}, or \.{\\fi} is scanned. + +@<Terminate the current conditional and skip to \.{\\fi}@>= +{@+if (tracing_ifs > 0) if (tracing_commands <= 1) show_cur_cmd_chr(); +if (cur_chr > if_limit) + if (if_limit==if_code) insert_relax(); /*condition not yet evaluated*/ + else{@+print_err("Extra ");print_cmd_chr(fi_or_else, cur_chr); +@.Extra \\or@> +@.Extra \\else@> +@.Extra \\fi@> + help1("I'm ignoring this; it doesn't match any \\if."); + error(); + } +else{@+while (cur_chr!=fi_code) pass_text(); /*skip to \.{\\fi}*/ + @<Pop the condition stack@>; + } +} + +@* File names. +It's time now to fret about file names. Besides the fact that different +operating systems treat files in different ways, we must cope with the +fact that completely different naming conventions are used by different +groups of people. The following programs show what is required for one +particular operating system; similar routines for other systems are not +difficult to devise. +@^fingers@> +@^system dependencies@> + +\TeX\ assumes that a file name has three parts: the name proper; its +``extension''; and a ``file area'' where it is found in an external file +system. The extension of an input file or a write file is assumed to be +`\.{.tex}' unless otherwise specified; it is `\.{.log}' on the +transcript file that records each run of \TeX; it is `\.{.tfm}' on the font +metric files that describe characters in the fonts \TeX\ uses; it is +`\.{.dvi}' on the output files that specify typesetting information; and it +is `\.{.fmt}' on the format files written by \.{INITEX} to initialize \TeX. +The file area can be arbitrary on input files, but files are usually +output to the user's current area. If an input file cannot be +found on the specified area, \TeX\ will look for it on a special system +area; this special area is intended for commonly used input files like +\.{webmac.tex}. + +Simple uses of \TeX\ refer only to file names that have no explicit +extension or area. For example, a person usually says `\.{\\input} \.{paper}' +or `\.{\\font\\tenrm} \.= \.{helvetica}' instead of `\.{\\input} +\.{paper.new}' or `\.{\\font\\tenrm} \.= \.{<csd.knuth>test}'. Simple file +names are best, because they make the \TeX\ source files portable; +whenever a file name consists entirely of letters and digits, it should be +treated in the same way by all implementations of \TeX. However, users +need the ability to refer to other files in their environment, especially +when responding to error messages concerning unopenable files; therefore +we want to let them use the syntax that appears in their favorite +operating system. + +The following procedures don't allow spaces to be part of +file names; but some users seem to like names that are spaced-out. +System-dependent changes to allow such things should probably +be made with reluctance, and only when an entire file name that +includes spaces is ``quoted'' somehow. + +@ In order to isolate the system-dependent aspects of file names, the +@^system dependencies@> +system-independent parts of \TeX\ are expressed in terms +of three system-dependent +procedures called |begin_name|, |more_name|, and |end_name|. In +essence, if the user-specified characters of the file name are $c_1\ldots c_n$, +the system-independent driver program does the operations +$$|begin_name|;\,|more_name|(c_1);\,\ldots\,;\,|more_name|(c_n); +\,|end_name|.$$ +These three procedures communicate with each other via global variables. +Afterwards the file name will appear in the string pool as three strings +called |cur_name|\penalty10000\hskip-.05em, +|cur_area|, and |cur_ext|; the latter two are null (i.e., +|""|), unless they were explicitly specified by the user. + +Actually the situation is slightly more complicated, because \TeX\ needs +to know when the file name ends. The |more_name| routine is a function +(with side effects) that returns |true| on the calls |more_name|$(c_1)$, +\dots, |more_name|$(c_{n-1})$. The final call |more_name|$(c_n)$ +returns |false|; or, it returns |true| and the token following $c_n$ is +something like `\.{\\hbox}' (i.e., not a character). In other words, +|more_name| is supposed to return |true| unless it is sure that the +file name has been completely scanned; and |end_name| is supposed to be able +to finish the assembly of |cur_name|, |cur_area|, and |cur_ext| regardless of +whether $|more_name|(c_n)$ returned |true| or |false|. + +@<Glob...@>= +static str_number @!cur_name; /*name of file just scanned*/ +static str_number @!cur_area; /*file area just scanned, or \.{""}*/ +static str_number @!cur_ext; /*file extension just scanned, or \.{""}*/ + +@ The file names we shall deal with for illustrative purposes have the +following structure: If the name contains `\.>' or `\.:', the file area +consists of all characters up to and including the final such character; +otherwise the file area is null. If the remaining file name contains +`\..', the file extension consists of all such characters from the first +remaining `\..' to the end, otherwise the file extension is null. +@^system dependencies@> + +We can scan such file names easily by using two global variables that keep track +of the occurrences of area and extension delimiters: + +@<Glob...@>= +static pool_pointer @!area_delimiter; /*the most recent `\.>' or `\.:', if any*/ +static pool_pointer @!ext_delimiter; /*the relevant `\..', if any*/ + +@ Input files that can't be found in the user's area may appear in a standard +system area called |TEX_area|. Font metric files whose areas are not given +explicitly are assumed to appear in a standard system area called +|TEX_font_area|. These system area names will, of course, vary from place +to place. +@^system dependencies@> + +@d TEX_area "TeXinputs/" +@.TeXinputs@> +@d TEX_font_area "TeXfonts/" +@.TeXfonts@> + +@ Here now is the first of the system-dependent routines for file name scanning. +@^system dependencies@> + +@p static bool quoted_filename; +static void begin_name(void) +{@+area_delimiter=0;ext_delimiter=0; quoted_filename=false; +} + +@ And here's the second. The string pool might change as the file name is +being scanned, since a new \.{\\csname} might be entered; therefore we keep +|area_delimiter| and |ext_delimiter| relative to the beginning of the current +string, instead of assigning an absolute address like |pool_ptr| to them. +@^system dependencies@> + +@p static bool more_name(ASCII_code @!c) +{@+if (c==' ' && !quoted_filename) return false; +else if (c=='"') {@+quoted_filename=!quoted_filename; return true; } +else {@+str_room(1);append_char(c); /*contribute |c| to the current string*/ + if (IS_DIR_SEP(c)) {@+area_delimiter=cur_length;ext_delimiter=0; } + else if (c=='.') ext_delimiter=cur_length; + return true; + } +} + +@ The third. +@^system dependencies@> + +@p static void end_name(void) +{@+if (str_ptr+3 > max_strings) + overflow("number of strings", max_strings-init_str_ptr); +@:TeX capacity exceeded number of strings}{\quad number of strings@> +if (area_delimiter==0) cur_area=empty_string; +else{@+cur_area=str_ptr; + str_start[str_ptr+1]=str_start[str_ptr]+area_delimiter;incr(str_ptr); + } +if (ext_delimiter==0) + {@+cur_ext=empty_string;cur_name=make_string(); + } +else{@+cur_name=str_ptr; + str_start[str_ptr+1]=str_start[str_ptr]+ext_delimiter-area_delimiter-1; + incr(str_ptr);cur_ext=make_string(); + } +} + +@ Conversely, here is a routine that takes three strings and prints a file +name that might have produced them. (The routine is system dependent, because +some operating systems put the file area last instead of first.) +@^system dependencies@> + +@<Basic printing...@>= +static void print_file_name(int @!n, int @!a, int @!e) +{@+slow_print(a);slow_print(n);slow_print(e); +} + +@ Another system-dependent routine is needed to convert three internal +\TeX\ strings +into the |name_of_file| value that is used to open files. The present code +allows both lowercase and uppercase letters in the file name. +@^system dependencies@> + +@d append_to_name(A) {@+c=A;incr(k); + if (k <= file_name_size) name_of_file[k]=xchr[c]; + } + +@p static void pack_file_name(str_number @!n, str_number @!a, str_number @!e, char *@!f) +{@+int k; /*number of positions filled in |name_of_file|*/ +ASCII_code @!c; /*character being packed*/ +int @!j; /*index into |str_pool|*/ +k=0; +for (j=str_start[a]; j<=str_start[a+1]-1; j++) append_to_name(so(str_pool[j]))@; +for (j=str_start[n]; j<=str_start[n+1]-1; j++) append_to_name(so(str_pool[j]))@; +if (f==NULL) + for (j=str_start[e]; j<=str_start[e+1]-1; j++) append_to_name(so(str_pool[j]))@; +else + while(*f!=0) append_to_name(so(*f++))@; +if (k <= file_name_size) name_length=k;@+else name_length=file_name_size; +name_of_file[name_length+1]=0; +} + + + +@ \TeX\ Live does not use the global variable |TEX_format_default|. It is no longer needed +to supply the text for default system areas +and extensions related to format files. + +@ Consequently \TeX\ Live does not need the initialization of |TEX_format_default| either. + +@ And \TeX\ Live does not check the length of |TEX_format_default|. + +@ The |format_extension|, however, is needed by \TeX\ Live +to create the format name from the job name. + +@d format_extension ".fmt" + +@ This part of the program +becomes active when a ``virgin'' \TeX\ is trying to get going, just after +the preliminary initialization, or when the user is substituting another +format file by typing `\.\&' after the initial `\.{**}' prompt. The buffer +contains the first line of input in |buffer[loc dotdot(last-1)]|, where +|loc < last| and |buffer[loc]!=' '|. + +\TeX\ Live uses the {\tt kpathsearch} library to implement access to files. +|open_fmt_file| is declared here and the +actual implementation is in the section on \TeX\ Live Integration. + +@<Declare the function called |open_fmt_file|@>= +static bool open_fmt_file(void); + +@ Operating systems often make it possible to determine the exact name (and +possible version number) of a file that has been opened. The following routine, +which simply makes a \TeX\ string from the value of |name_of_file|, should +ideally be changed to deduce the full name of file~|f|, which is the file +most recently opened, if it is possible to do this in a \PASCAL\ program. +@^system dependencies@> + +This routine might be called after string memory has overflowed, hence +we dare not use `|str_room|'. + +@p static str_number make_name_string(void) +{@+int k; /*index into |name_of_file|*/ +if ((pool_ptr+name_length > pool_size)||(str_ptr==max_strings)|| + (cur_length > 0)) + return'?'; +else{@+for (k=1; k<=name_length; k++) append_char(xord[name_of_file[k]]); + return make_string(); + } +} +static str_number a_make_name_string(alpha_file *f) +{@+return make_name_string(); +} +static str_number b_make_name_string(byte_file *f) +{@+return make_name_string(); +} +#ifdef @!INIT +static str_number w_make_name_string(word_file *f) +{@+return make_name_string(); +} +#endif + +@ Now let's consider the ``driver'' +routines by which \TeX\ deals with file names +in a system-independent manner. First comes a procedure that looks for a +file name. +There are two ways to specify the file name: as a general text argument +or as a token (after expansion). +The traditional token delimiter is the space. For a file name, however, +a double quote is used as the token delimiter if the token starts +with a double quote. + +Once the |area_delimiter| and the |ext_delimiter| are defined, +the final processing is shared for all variants. + +When starting, \.{\\relax} is skipped as well as blanks and non-calls. +Then a test for the |left_brace| will branch to the code for scanning +a general text. +% consider the case where a double quote is made an active character +% equivalent to a left brace! + +@p static void scan_file_name(void) +{@+ +pool_pointer @!j, k; /*index into |str_pool|*/ +int @!old_setting; /*holds |selector| setting*/ +name_in_progress=true;begin_name(); +@<Get the next non-blank non-relax...@>; +if (cur_cmd==left_brace) + @<Define a general text file name and |goto done|@>@; +loop@+{@+if ((cur_cmd > other_char)||(cur_chr > 255)) /*not a character*/ + {@+back_input();goto done; + } +#if 0 + /* This is from pdftex-final.ch. I don't know these `some cases', + and I am not sure whether the name should end even if quoting is on.*/ + /*If |cur_chr| is a space and we're not scanning a token list, check + whether we're at the end of the buffer. Otherwise we end up adding + spurious spaces to file names in some cases.*/ + if (cur_chr==' ' && state!=token_list && loc>limit) goto done; +#endif + if (!more_name(cur_chr)) goto done; + get_x_token(); + } +done: end_name();name_in_progress=false; +} + +@ The global variable |name_in_progress| is used to prevent recursive +use of |scan_file_name|, since the |begin_name| and other procedures +communicate via global variables. Recursion would arise only by +devious tricks like `\.{\\input\\input f}'; such attempts at sabotage +must be thwarted. Furthermore, |name_in_progress| prevents \.{\\input} +@^recursion@> +from being initiated when a font size specification is being scanned. + +Another global variable, |job_name|, contains the file name that was first +\.{\\input} by the user. This name is extended by `\.{.log}' and `\.{.dvi}' +and `\.{.fmt}' in the names of \TeX's output files. + +@<Glob...@>= +static bool @!name_in_progress; /*is a file name being scanned?*/ +static str_number @!job_name; /*principal file name*/ +static bool @!log_opened; /*has the transcript file been opened?*/ + +@ Initially |job_name==0|; it becomes nonzero as soon as the true name is known. +We have |job_name==0| if and only if the `\.{log}' file has not been opened, +except of course for a short time just after |job_name| has become nonzero. + +@<Initialize the output...@>= +job_name=0;name_in_progress=false;log_opened=false; + +@ Here is a routine that manufactures the output file names, assuming that +|job_name!=0|. It ignores and changes the current settings of |cur_area| +and |cur_ext|. + +@d pack_cur_name(A) if (cur_ext==empty_string) pack_file_name(cur_name, cur_area, cur_ext,A); + else pack_file_name(cur_name, cur_area, cur_ext,NULL) + +@p static void pack_job_name(char *@!s) /*|s==".log"|, |".dvi"|, or + |format_extension|*/ +{@+cur_area=empty_string;cur_ext=empty_string; +cur_name=job_name;pack_cur_name(s); +} + +@ If some trouble arises when \TeX\ tries to open a file, the following +routine calls upon the user to supply another file name. Parameter~|s| +is used in the error message to identify the type of file; parameter~|e| +is the default extension if none is given. +We handle the specification of a file name with possibly spaces in +double quotes (the last one is optional if this is the end of line +i.e. the end of the buffer). +Upon exit from the routine, +variables |cur_name|, |cur_area|, |cur_ext|, and |name_of_file| are +ready for another attempt at file opening. + +@p static void prompt_file_name(char *@!s, char *@!e) +{@+ +int k; /*index into |buffer|*/ +if (interaction==scroll_mode) wake_up_terminal; +if (strcmp(s,"input file name")==0) print_err("I can't find file `"); +@.I can't find file x@> +else print_err("I can't write on file `"); +@.I can't write on file x@> +print_file_name(cur_name, cur_area, cur_ext);print("'."); +if (strcmp(e,".tex")==0) show_context(); +print_nl("Please type another ");print(s); +@.Please type...@> +if (interaction < scroll_mode) + fatal_error("*** (job aborted, file error in nonstop mode)"); +@.job aborted, file error...@> +clear_terminal;prompt_input(": ");@<Scan file name in the buffer@>; +pack_cur_name(e); +} + +@ @<Scan file name in the buffer@>= +{@+ +begin_name();k=first; +while ((buffer[k]==' ')&&(k < last)) incr(k); +loop@+{@+if (k==last) goto done; + if (!more_name(buffer[k])) goto done; + incr(k); + } +done: end_name(); +} + +@ Here's an example of how these conventions are used. Whenever it is time to +ship out a box of stuff, we shall use the macro |ensure_dvi_open|. + +@d ensure_dvi_open if (output_file_name==0) + {@+if (job_name==0) open_log_file(); + pack_job_name(".dvi"); + while (!b_open_out(&dvi_file)) + prompt_file_name("file name for output",".dvi"); + output_file_name=b_make_name_string(&dvi_file); + } + +@<Glob...@>= +static byte_file @!dvi_file; /*the device-independent output goes here*/ +static str_number @!output_file_name; /*full name of the output file*/ +static str_number @!log_name; /*full name of the log file*/ + +@ @<Initialize the output...@>=output_file_name=0; + +@ The |open_log_file| routine is used to open the transcript file and to help +it catch up to what has previously been printed on the terminal. + +@p static void open_log_file(void) +{@+int old_setting; /*previous |selector| setting*/ +int @!k; /*index into |months| and |buffer|*/ +int @!l; /*end of first input line*/ +char @!months[]=" JANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDEC"; /*abbreviations of month names*/ +old_setting=selector; +if (job_name==0) job_name=s_no(c_job_name?c_job_name:"texput"); /* \TeX\ Live */ +pack_job_name(".fls"); +recorder_change_filename((char *)name_of_file+1); +@.texput@> +pack_job_name(".log"); +while (!a_open_out(&log_file)) @<Try to get a different log file name@>; +log_name=a_make_name_string(&log_file); +selector=log_only;log_opened=true; +@<Print the banner line, including the date and time@>; +input_stack[input_ptr]=cur_input; /*make sure bottom level is in memory*/ +print_nl("**"); +@.**@> +l=input_stack[0].limit_field; /*last position of first line*/ +if (buffer[l]==end_line_char) decr(l); +for (k=1; k<=l; k++) printn(buffer[k]); +print_ln(); /*now the transcript file contains the first line of input*/ +selector=old_setting+2; /*|log_only| or |term_and_log|*/ +} + +@ Sometimes |open_log_file| is called at awkward moments when \TeX\ is +unable to print error messages or even to |show_context|. +The |prompt_file_name| routine can result in a |fatal_error|, but the |error| +routine will not be invoked because |log_opened| will be false. + +The normal idea of |batch_mode| is that nothing at all should be written +on the terminal. However, in the unusual case that +no log file could be opened, we make an exception and allow +an explanatory message to be seen. + +Incidentally, the program always refers to the log file as a `\.{transcript +file}', because some systems cannot use the extension `\.{.log}' for +this file. + +@<Try to get a different log file name@>= +{@+selector=term_only; +prompt_file_name("transcript file name",".log"); +} + +@ @<Print the banner...@>= +{@+wlog("%s",banner); +slow_print(format_ident);print(" "); +print_int(sys_day);print_char(' '); +for (k=3*sys_month-2; k<=3*sys_month; k++) wlog("%c",months[k]); +print_char(' ');print_int(sys_year);print_char(' '); +print_two(sys_time/60);print_char(':');print_two(sys_time%60); +if (eTeX_ex) + {@+;wlog_cr;wlog("entering extended mode"); + } +if (Prote_ex) + {@+;wlog_cr;wlog("entering Prote mode"); + } +} + +@ Let's turn now to the procedure that is used to initiate file reading +when an `\.{\\input}' command is being processed. +Beware: For historic reasons, this code foolishly conserves a tiny bit +of string pool space; but that can confuse the interactive `\.E' option. +@^system dependencies@> + +@p static void start_input(void) /*\TeX\ will \.{\\input} something*/ +{@+ +scan_file_name(); /*set |cur_name| to desired file name*/ +pack_cur_name(""); +loop@+{@+begin_file_reading(); /*set up |cur_file| and new level of input*/ + if (kpse_in_name_ok((char*)name_of_file+1) && a_open_in(&cur_file)) goto done; + end_file_reading(); /*remove the level that didn't work*/ + prompt_file_name("input file name",".tex"); + } +done: name=a_make_name_string(&cur_file);@/ +if (source_filename_stack[in_open]!=NULL) + free(source_filename_stack[in_open]); +source_filename_stack[in_open]=strdup((char *)name_of_file+1); /*\TeX\ Live*/ +if (full_source_filename_stack[in_open]!=NULL) + free(full_source_filename_stack[in_open]); +full_source_filename_stack[in_open]=strdup(full_name_of_file); +@<Set new |cur_file_num|@>@; +/* new entry on the macro stack */ +{ @<additional local variables for |start_input|@> + @<update the macro stack@>@; +} +if (job_name==0) + {@+if (c_job_name==NULL) job_name=cur_name; + else job_name=s_no(c_job_name); open_log_file(); /* \TeX\ Live*/ + } /*|open_log_file| doesn't |show_context|, so |limit| + and |loc| needn't be set to meaningful values yet*/ +if (term_offset+strlen(full_source_filename_stack[in_open]) > max_print_line-2) + print_ln(); +else if ((term_offset > 0)||(file_offset > 0)) print_char(' '); +print_char('(');incr(open_parens); +print(full_source_filename_stack[in_open]);update_terminal; +state=new_line; +if (name==str_ptr-1) /*conserve string pool space (but see note above)*/ + {@+flush_string;name=cur_name; + } +@<Read the first line of the new file@>; +} + +@ Here we have to remember to tell the |input_ln| routine not to +start with a |get|. If the file is empty, it is considered to +contain a single blank line. +@^system dependencies@> +@^empty line at end of file@> + +@<Read the first line...@>= +{@+line=1; +if (input_ln(&cur_file, false)) do_nothing; +firm_up_the_line(); +if (end_line_char_inactive) decr(limit); +else buffer[limit]=end_line_char; +first=limit+1;loc=start; +} + +@* Font metric data. +\TeX\ gets its knowledge about fonts from font metric files, also called +\.{TFM} files; the `\.T' in `\.{TFM}' stands for \TeX, +but other programs know about them too. +@:TFM files}{\.{TFM} files@> +@^font metric files@> + +The information in a \.{TFM} file appears in a sequence of 8-bit bytes. +Since the number of bytes is always a multiple of 4, we could +also regard the file as a sequence of 32-bit words, but \TeX\ uses the +byte interpretation. The format of \.{TFM} files was designed by +Lyle Ramshaw in 1980. The intent is to convey a lot of different kinds +@^Ramshaw, Lyle Harold@> +of information in a compact but useful form. + +@<Glob...@>= +static byte_file @!tfm_file; + +@ The first 24 bytes (6 words) of a \.{TFM} file contain twelve 16-bit +integers that give the lengths of the various subsequent portions +of the file. These twelve integers are, in order: +$$\vbox{\halign{\hfil#&$\null=\null$#\hfil\cr +|lf|&length of the entire file, in words;\cr +|lh|&length of the header data, in words;\cr +|bc|&smallest character code in the font;\cr +|ec|&largest character code in the font;\cr +|nw|&number of words in the width table;\cr +|nh|&number of words in the height table;\cr +|nd|&number of words in the depth table;\cr +|ni|&number of words in the italic correction table;\cr +|nl|&number of words in the lig/kern table;\cr +|nk|&number of words in the kern table;\cr +|ne|&number of words in the extensible character table;\cr +|np|&number of font parameter words.\cr}}$$ +They are all nonnegative and less than $2^{15}$. We must have |bc-1 <= ec <= 255|, +and +$$\hbox{|lf==6+lh+(ec-bc+1)+nw+nh+nd+ni+nl+nk+ne+np|.}$$ +Note that a font may contain as many as 256 characters (if |bc==0| and |ec==255|), +and as few as 0 characters (if |bc==ec+1|). + +Incidentally, when two or more 8-bit bytes are combined to form an integer of +16 or more bits, the most significant bytes appear first in the file. +This is called BigEndian order. +@!@^BigEndian order@> + +@ The rest of the \.{TFM} file may be regarded as a sequence of ten data +arrays having the informal specification +$$\def\arr$[#1]#2${\&{array} $[#1]$ \&{of} #2} +\def\PB#1{\arr#1} +\vbox{\halign{\hfil\\{#}&$\,:\,$#\hfil\cr +header&|[0 dotdot lh-1]@t\\{stuff}@>|\cr +char\_info&|[bc dotdot ec]char_info_word|\cr +width&|[0 dotdot nw-1]fix_word|\cr +height&|[0 dotdot nh-1]fix_word|\cr +depth&|[0 dotdot nd-1]fix_word|\cr +italic&|[0 dotdot ni-1]fix_word|\cr +lig\_kern&|[0 dotdot nl-1]lig_kern_command|\cr +kern&|[0 dotdot nk-1]fix_word|\cr +exten&|[0 dotdot ne-1]extensible_recipe|\cr +param&|[1 dotdot np]fix_word|\cr}}$$ +The most important data type used here is a |@!fix_word|, which is +a 32-bit representation of a binary fraction. A |fix_word| is a signed +quantity, with the two's complement of the entire word used to represent +negation. Of the 32 bits in a |fix_word|, exactly 12 are to the left of the +binary point; thus, the largest |fix_word| value is $2048-2^{-20}$, and +the smallest is $-2048$. We will see below, however, that all but two of +the |fix_word| values must lie between $-16$ and $+16$. + +@ The first data array is a block of header information, which contains +general facts about the font. The header must contain at least two words, +|header[0]| and |header[1]|, whose meaning is explained below. +Additional header information of use to other software routines might +also be included, but \TeX82 does not need to know about such details. +For example, 16 more words of header information are in use at the Xerox +Palo Alto Research Center; the first ten specify the character coding +scheme used (e.g., `\.{XEROX text}' or `\.{TeX math symbols}'), the next five +give the font identifier (e.g., `\.{HELVETICA}' or `\.{CMSY}'), and the +last gives the ``face byte.'' The program that converts \.{DVI} files +to Xerox printing format gets this information by looking at the \.{TFM} +file, which it needs to read anyway because of other information that +is not explicitly repeated in \.{DVI}~format. + +\yskip\hang|header[0]| is a 32-bit check sum that \TeX\ will copy into +the \.{DVI} output file. Later on when the \.{DVI} file is printed, +possibly on another computer, the actual font that gets used is supposed +to have a check sum that agrees with the one in the \.{TFM} file used by +\TeX. In this way, users will be warned about potential incompatibilities. +(However, if the check sum is zero in either the font file or the \.{TFM} +file, no check is made.) The actual relation between this check sum and +the rest of the \.{TFM} file is not important; the check sum is simply an +identification number with the property that incompatible fonts almost +always have distinct check sums. +@^check sum@> + +\yskip\hang|header[1]| is a |fix_word| containing the design size of +the font, in units of \TeX\ points. This number must be at least 1.0; it is +fairly arbitrary, but usually the design size is 10.0 for a ``10 point'' +font, i.e., a font that was designed to look best at a 10-point size, +whatever that really means. When a \TeX\ user asks for a font +`\.{at} $\delta$ \.{pt}', the effect is to override the design size +and replace it by $\delta$, and to multiply the $x$ and~$y$ coordinates +of the points in the font image by a factor of $\delta$ divided by the +design size. {\sl All other dimensions in the\/ \.{TFM} file are +|fix_word|\kern-1pt\ numbers in design-size units}, with the exception of +|param[1]| (which denotes the slant ratio). Thus, for example, the value +of |param[6]|, which defines the \.{em} unit, is often the |fix_word| value +$2^{20}=1.0$, since many fonts have a design size equal to one em. +The other dimensions must be less than 16 design-size units in absolute +value; thus, |header[1]| and |param[1]| are the only |fix_word| +entries in the whole \.{TFM} file whose first byte might be something +besides 0 or 255. + +@ Next comes the |char_info| array, which contains one |@!char_info_word| +per character. Each word in this part of the file contains six fields +packed into four bytes as follows. + +\yskip\hang first byte: |@!width_index| (8 bits)\par +\hang second byte: |@!height_index| (4 bits) times 16, plus |@!depth_index| + (4~bits)\par +\hang third byte: |@!italic_index| (6 bits) times 4, plus |@!tag| + (2~bits)\par +\hang fourth byte: |@!rem| (8 bits)\par +\yskip\noindent +The actual width of a character is \\{width}|[width_index]|, in design-size +units; this is a device for compressing information, since many characters +have the same width. Since it is quite common for many characters +to have the same height, depth, or italic correction, the \.{TFM} format +imposes a limit of 16 different heights, 16 different depths, and +64 different italic corrections. + +@!@^italic correction@> +The italic correction of a character has two different uses. +(a)~In ordinary text, the italic correction is added to the width only if +the \TeX\ user specifies `\.{\\/}' after the character. +(b)~In math formulas, the italic correction is always added to the width, +except with respect to the positioning of subscripts. + +Incidentally, the relation $\\{width}[0]=\\{height}[0]=\\{depth}[0]= +\\{italic}[0]=0$ should always hold, so that an index of zero implies a +value of zero. The |width_index| should never be zero unless the +character does not exist in the font, since a character is valid if and +only if it lies between |bc| and |ec| and has a nonzero |width_index|. + +@ The |tag| field in a |char_info_word| has four values that explain how to +interpret the |rem| field. + +\yskip\hangg|tag==0| (|no_tag|) means that |rem| is unused.\par +\hangg|tag==1| (|lig_tag|) means that this character has a ligature/kerning +program starting at position |rem| in the |lig_kern| array.\par +\hangg|tag==2| (|list_tag|) means that this character is part of a chain of +characters of ascending sizes, and not the largest in the chain. The +|rem| field gives the character code of the next larger character.\par +\hangg|tag==3| (|ext_tag|) means that this character code represents an +extensible character, i.e., a character that is built up of smaller pieces +so that it can be made arbitrarily large. The pieces are specified in +|@!exten[rem]|.\par +\yskip\noindent +Characters with |tag==2| and |tag==3| are treated as characters with |tag==0| +unless they are used in special circumstances in math formulas. For example, +the \.{\\sum} operation looks for a |list_tag|, and the \.{\\left} +operation looks for both |list_tag| and |ext_tag|. + +@d no_tag 0 /*vanilla character*/ +@d lig_tag 1 /*character has a ligature/kerning program*/ +@d list_tag 2 /*character has a successor in a charlist*/ +@d ext_tag 3 /*character is extensible*/ + +@ The |lig_kern| array contains instructions in a simple programming language +that explains what to do for special letter pairs. Each word in this array is a +|@!lig_kern_command| of four bytes. + +\yskip\hang first byte: |skip_byte|, indicates that this is the final program + step if the byte is 128 or more, otherwise the next step is obtained by + skipping this number of intervening steps.\par +\hang second byte: |next_char|, ``if |next_char| follows the current character, + then perform the operation and stop, otherwise continue.''\par +\hang third byte: |op_byte|, indicates a ligature step if less than~128, + a kern step otherwise.\par +\hang fourth byte: |rem|.\par +\yskip\noindent +In a kern step, an +additional space equal to |kern[256*(op_byte-128)+rem]| is inserted +between the current character and |next_char|. This amount is +often negative, so that the characters are brought closer together +by kerning; but it might be positive. + +There are eight kinds of ligature steps, having |op_byte| codes $4a+2b+c$ where +$0\le a\le b+c$ and $0\le b,c\le1$. The character whose code is +|rem| is inserted between the current character and |next_char|; +then the current character is deleted if $b=0$, and |next_char| is +deleted if $c=0$; then we pass over $a$~characters to reach the next +current character (which may have a ligature/kerning program of its own). + +If the very first instruction of the |lig_kern| array has |skip_byte==255|, +the |next_char| byte is the so-called boundary character of this font; +the value of |next_char| need not lie between |bc| and~|ec|. +If the very last instruction of the |lig_kern| array has |skip_byte==255|, +there is a special ligature/kerning program for a boundary character at the +left, beginning at location |256*op_byte+rem|. +The interpretation is that \TeX\ puts implicit boundary characters +before and after each consecutive string of characters from the same font. +These implicit characters do not appear in the output, but they can affect +ligatures and kerning. + +If the very first instruction of a character's |lig_kern| program has +|skip_byte > 128|, the program actually begins in location +|256*op_byte+rem|. This feature allows access to large |lig_kern| +arrays, because the first instruction must otherwise +appear in a location | <= 255|. + +Any instruction with |skip_byte > 128| in the |lig_kern| array must satisfy +the condition +$$\hbox{|256*op_byte+rem < nl|.}$$ +If such an instruction is encountered during +normal program execution, it denotes an unconditional halt; no ligature +or kerning command is performed. + +@d stop_flag qi(128) /*value indicating `\.{STOP}' in a lig/kern program*/ +@d kern_flag qi(128) /*op code for a kern step*/ +@d skip_byte(A) A.b0 +@d next_char(A) A.b1 +@d op_byte(A) A.b2 +@d rem_byte(A) A.b3 + +@ Extensible characters are specified by an |@!extensible_recipe|, which +consists of four bytes called |@!top|, |@!mid|, |@!bot|, and |@!rep| (in this +order). These bytes are the character codes of individual pieces used to +build up a large symbol. If |top|, |mid|, or |bot| are zero, they are not +present in the built-up result. For example, an extensible vertical line is +like an extensible bracket, except that the top and bottom pieces are missing. + +Let $T$, $M$, $B$, and $R$ denote the respective pieces, or an empty box +if the piece isn't present. Then the extensible characters have the form +$TR^kMR^kB$ from top to bottom, for some |k >= 0|, unless $M$ is absent; +in the latter case we can have $TR^kB$ for both even and odd values of~|k|. +The width of the extensible character is the width of $R$; and the +height-plus-depth is the sum of the individual height-plus-depths of the +components used, since the pieces are butted together in a vertical list. + +@d ext_top(A) A.b0 /*|top| piece in a recipe*/ +@d ext_mid(A) A.b1 /*|mid| piece in a recipe*/ +@d ext_bot(A) A.b2 /*|bot| piece in a recipe*/ +@d ext_rep(A) A.b3 /*|rep| piece in a recipe*/ + +@ The final portion of a \.{TFM} file is the |param| array, which is another +sequence of |fix_word| values. + +\yskip\hang|param[1]==slant| is the amount of italic slant, which is used +to help position accents. For example, |slant==.25| means that when you go +up one unit, you also go .25 units to the right. The |slant| is a pure +number; it's the only |fix_word| other than the design size itself that is +not scaled by the design size. + +\hang|param[2]==space| is the normal spacing between words in text. +Note that character |' '| in the font need not have anything to do with +blank spaces. + +\hang|param[3]==space_stretch| is the amount of glue stretching between words. + +\hang|param[4]==space_shrink| is the amount of glue shrinking between words. + +\hang|param[5]==x_height| is the size of one ex in the font; it is also +the height of letters for which accents don't have to be raised or lowered. + +\hang|param[6]==quad| is the size of one em in the font. + +\hang|param[7]==extra_space| is the amount added to |param[2]| at the +ends of sentences. + +\yskip\noindent +If fewer than seven parameters are present, \TeX\ sets the missing parameters +to zero. Fonts used for math symbols are required to have +additional parameter information, which is explained later. + +@d slant_code 1 +@d space_code 2 +@d space_stretch_code 3 +@d space_shrink_code 4 +@d x_height_code 5 +@d quad_code 6 +@d extra_space_code 7 + +@ So that is what \.{TFM} files hold. Since \TeX\ has to absorb such information +about lots of fonts, it stores most of the data in a large array called +|font_info|. Each item of |font_info| is a |memory_word|; the |fix_word| +data gets converted into |scaled| entries, while everything else goes into +words of type |four_quarters|. + +When the user defines \.{\\font\\f}, say, \TeX\ assigns an internal number +to the user's font~\.{\\f}. Adding this number to |font_id_base| gives the +|eqtb| location of a ``frozen'' control sequence that will always select +the font. + +@<Types...@>= +typedef uint8_t internal_font_number; /*|font| in a |char_node|*/ +typedef int32_t font_index; /*index into |font_info|*/ + +@ Here now is the (rather formidable) array of font arrays. + +@d non_char qi(256) /*a |halfword| code that can't match a real character*/ +@d non_address 0 /*a spurious |bchar_label|*/ + +@<Glob...@>= +static memory_word @!font_info[font_mem_size+1]; + /*the big collection of font data*/ +static font_index @!fmem_ptr; /*first unused word of |font_info|*/ +static internal_font_number @!font_ptr; /*largest internal font number in use*/ +static four_quarters @!font_check0[font_max-font_base+1], + *const @!font_check = @!font_check0-font_base; /*check sum*/ +static scaled @!font_size0[font_max-font_base+1], + *const @!font_size = @!font_size0-font_base; /*``at'' size*/ +static scaled @!font_dsize0[font_max-font_base+1], + *const @!font_dsize = @!font_dsize0-font_base; /*``design'' size*/ +static font_index @!font_params0[font_max-font_base+1], + *const @!font_params = @!font_params0-font_base; /*how many font + parameters are present*/ +static str_number @!font_name0[font_max-font_base+1], + *const @!font_name = @!font_name0-font_base; /*name of the font*/ +static str_number @!font_area0[font_max-font_base+1], + *const @!font_area = @!font_area0-font_base; /*area of the font*/ +static eight_bits @!font_bc0[font_max-font_base+1], + *const @!font_bc = @!font_bc0-font_base; + /*beginning (smallest) character code*/ +static eight_bits @!font_ec0[font_max-font_base+1], + *const @!font_ec = @!font_ec0-font_base; + /*ending (largest) character code*/ +static pointer @!font_glue0[font_max-font_base+1], + *const @!font_glue = @!font_glue0-font_base; + /*glue specification for interword space, |null| if not allocated*/ +static bool @!font_used0[font_max-font_base+1], + *const @!font_used = @!font_used0-font_base; + /*has a character from this font actually appeared in the output?*/ +static int @!hyphen_char0[font_max-font_base+1], + *const @!hyphen_char = @!hyphen_char0-font_base; + /*current \.{\\hyphenchar} values*/ +static int @!skew_char0[font_max-font_base+1], + *const @!skew_char = @!skew_char0-font_base; + /*current \.{\\skewchar} values*/ +static font_index @!bchar_label0[font_max-font_base+1], + *const @!bchar_label = @!bchar_label0-font_base; + /*start of |lig_kern| program for left boundary character, + |non_address| if there is none*/ +static int16_t @!font_bchar0[font_max-font_base+1], + *const @!font_bchar = @!font_bchar0-font_base; + /*boundary character, |non_char| if there is none*/ +static int16_t @!font_false_bchar0[font_max-font_base+1], + *const @!font_false_bchar = @!font_false_bchar0-font_base; + /*|font_bchar| if it doesn't exist in the font, otherwise |non_char|*/ + +@ Besides the arrays just enumerated, we have directory arrays that make it +easy to get at the individual entries in |font_info|. For example, the +|char_info| data for character |c| in font |f| will be in +|font_info[char_base[f]+c].qqqq|; and if |w| is the |width_index| +part of this word (the |b0| field), the width of the character is +|font_info[width_base[f]+w].sc|. (These formulas assume that +|min_quarterword| has already been added to |c| and to |w|, since \TeX\ +stores its quarterwords that way.) + +@<Glob...@>= +static int @!char_base0[font_max-font_base+1], + *const @!char_base = @!char_base0-font_base; + /*base addresses for |char_info|*/ +static int @!width_base0[font_max-font_base+1], + *const @!width_base = @!width_base0-font_base; + /*base addresses for widths*/ +static int @!height_base0[font_max-font_base+1], + *const @!height_base = @!height_base0-font_base; + /*base addresses for heights*/ +static int @!depth_base0[font_max-font_base+1], + *const @!depth_base = @!depth_base0-font_base; + /*base addresses for depths*/ +static int @!italic_base0[font_max-font_base+1], + *const @!italic_base = @!italic_base0-font_base; + /*base addresses for italic corrections*/ +static int @!lig_kern_base0[font_max-font_base+1], + *const @!lig_kern_base = @!lig_kern_base0-font_base; + /*base addresses for ligature/kerning programs*/ +static int @!kern_base0[font_max-font_base+1], + *const @!kern_base = @!kern_base0-font_base; + /*base addresses for kerns*/ +static int @!exten_base0[font_max-font_base+1], + *const @!exten_base = @!exten_base0-font_base; + /*base addresses for extensible recipes*/ +static int @!param_base0[font_max-font_base+1], + *const @!param_base = @!param_base0-font_base; + /*base addresses for font parameters*/ + +@ @<Set init...@>= +for (k=font_base; k<=font_max; k++) font_used[k]=false; + +@ \TeX\ always knows at least one font, namely the null font. It has no +characters, and its seven parameters are all equal to zero. + +@<Initialize table...@>= +font_ptr=null_font;fmem_ptr=7; +font_name[null_font]=s_no("nullfont");font_area[null_font]=empty_string; +hyphen_char[null_font]='-';skew_char[null_font]=-1; +bchar_label[null_font]=non_address; +font_bchar[null_font]=non_char;font_false_bchar[null_font]=non_char; +font_bc[null_font]=1;font_ec[null_font]=0; +font_size[null_font]=0;font_dsize[null_font]=0; +char_base[null_font]=0;width_base[null_font]=0; +height_base[null_font]=0;depth_base[null_font]=0; +italic_base[null_font]=0;lig_kern_base[null_font]=0; +kern_base[null_font]=0;exten_base[null_font]=0; +font_glue[null_font]=null;font_params[null_font]=7; +param_base[null_font]=-1; +for (k=0; k<=6; k++) font_info[k].sc=0; + +@ @<Put each...@>= +primitive("nullfont", set_font, null_font); +@!@:null\_font\_}{\.{\\nullfont} primitive@> +text(frozen_null_font)=text(cur_val);eqtb[frozen_null_font]=eqtb[cur_val]; + +@ Of course we want to define macros that suppress the detail of how font +information is actually packed, so that we don't have to write things like +$$\hbox{|font_info[width_base[f]+font_info[char_base[f]+c].qqqq.b0].sc|}$$ +too often. The \.{WEB} definitions here make |char_info(f)(c)| the +|four_quarters| word of font information corresponding to character +|c| of font |f|. If |q| is such a word, |char_width(f)(q)| will be +the character's width; hence the long formula above is at least +abbreviated to +$$\hbox{|char_width(f)(char_info(f)(c))|.}$$ +Usually, of course, we will fetch |q| first and look at several of its +fields at the same time. + +The italic correction of a character will be denoted by +|char_italic(f)(q)|, so it is analogous to |char_width|. But we will get +at the height and depth in a slightly different way, since we usually want +to compute both height and depth if we want either one. The value of +|height_depth(q)| will be the 8-bit quantity +$$b=|height_index|\times16+|depth_index|,$$ and if |b| is such a byte we +will write |char_height(f)(b)| and |char_depth(f)(b)| for the height and +depth of the character |c| for which |q==char_info(f)(c)|. Got that? + +The tag field will be called |char_tag(q)|; the remainder byte will be +called |rem_byte(q)|, using a macro that we have already defined above. + +Access to a character's |width|, |height|, |depth|, and |tag| fields is +part of \TeX's inner loop, so we want these macros to produce code that is +as fast as possible under the circumstances. +@^inner loop@> + +@d char_info(A, B) font_info[char_base[A]+B].qqqq +@d char_width(A, B) font_info[width_base[A]+B.b0].sc +@d char_exists(A) (A.b0 > min_quarterword) +@d char_italic(A, B) font_info[italic_base[A]+(qo(B.b2))/4].sc +@d height_depth(A) qo(A.b1) +@d char_height(A, B) font_info[height_base[A]+(B)/16].sc +@d char_depth(A, B) font_info[depth_base[A]+(B)%16].sc +@d char_tag(A) ((qo(A.b2))%4) + +@ The global variable |null_character| is set up to be a word of +|char_info| for a character that doesn't exist. Such a word provides a +convenient way to deal with erroneous situations. + +@<Glob...@>= +static four_quarters @!null_character; /*nonexistent character information*/ + +@ @<Set init...@>= +null_character.b0=min_quarterword;null_character.b1=min_quarterword; +null_character.b2=min_quarterword;null_character.b3=min_quarterword; + +@ Here are some macros that help process ligatures and kerns. +We write |char_kern(f)(j)| to find the amount of kerning specified by +kerning command~|j| in font~|f|. If |j| is the |char_info| for a character +with a ligature/kern program, the first instruction of that program is either +|i==font_info[lig_kern_start(f)(j)]| or |font_info[lig_kern_restart(f)(i)]|, +depending on whether or not |skip_byte(i) <= stop_flag|. + +The constant |kern_base_offset| should be simplified, for \PASCAL\ compilers +that do not do local optimization. +@^system dependencies@> + +@d char_kern(A, B) font_info[kern_base[A]+256*op_byte(B)+rem_byte(B)].sc +@d kern_base_offset 256*(128+min_quarterword) +@d lig_kern_start(A, B) lig_kern_base[A]+B.b3 /*beginning of lig/kern program*/ +@d lig_kern_restart(A, B) lig_kern_base[A]+256*op_byte(B)+rem_byte(B)+32768-kern_base_offset + +@ Font parameters are referred to as |slant(f)|, |space(f)|, etc. + +@d param_end(A) param_base[A]].sc +@d param(A) font_info[A+param_end +@d slant param(slant_code) /*slant to the right, per unit distance upward*/ +@d space param(space_code) /*normal space between words*/ +@d space_stretch param(space_stretch_code) /*stretch between words*/ +@d space_shrink param(space_shrink_code) /*shrink between words*/ +@d x_height param(x_height_code) /*one ex*/ +@d quad param(quad_code) /*one em*/ +@d extra_space param(extra_space_code) /*additional space at end of sentence*/ + +@<The em width for |cur_font|@>=quad(cur_font) + +@ @<The x-height for |cur_font|@>=x_height(cur_font) + +@ \TeX\ checks the information of a \.{TFM} file for validity as the +file is being read in, so that no further checks will be needed when +typesetting is going on. The somewhat tedious subroutine that does this +is called |read_font_info|. It has four parameters: the user font +identifier~|u|, the file name and area strings |nom| and |aire|, and the +``at'' size~|s|. If |s|~is negative, it's the negative of a scale factor +to be applied to the design size; |s==-1000| is the normal case. +Otherwise |s| will be substituted for the design size; in this +case, |s| must be positive and less than $2048\rm\,pt$ +(i.e., it must be less than $2^{27}$ when considered as an integer). + +The subroutine opens and closes a global file variable called |tfm_file|. +It returns the value of the internal font number that was just loaded. +If an error is detected, an error message is issued and no font +information is stored; |null_font| is returned in this case. + +@d abort goto bad_tfm /*do this when the \.{TFM} data is wrong*/ + +@p static internal_font_number read_font_info(pointer @!u, str_number @!nom, str_number @!aire, + scaled @!s) /*input a \.{TFM} file*/ +{@+ +int k; /*index into |font_info|*/ +bool @!file_opened; /*was |tfm_file| successfully opened?*/ +halfword @!lf, @!lh, @!bc, @!ec, @!nw, @!nh, @!nd, @!ni, @!nl, @!nk, @!ne, @!np; + /*sizes of subfiles*/ +internal_font_number @!f; /*the new font's number*/ +internal_font_number @!g; /*the number to return*/ +eight_bits @!a, @!b, @!c, @!d; /*byte variables*/ +four_quarters @!qw;scaled @!sw; /*accumulators*/ +int @!bch_label; /*left boundary start location, or infinity*/ +int @!bchar; /*boundary character, or 256*/ +scaled @!z; /*the design size or the ``at'' size*/ +int @!alpha;int @!beta; + /*auxiliary quantities used in fixed-point multiplication*/ +g=null_font;@/ +@<Read and check the font data; |abort| if the \.{TFM} file is malformed; +if there's no room for this font, say so and |goto done|; otherwise |incr(font_ptr)| +and |goto done|@>; +bad_tfm: @<Report that the font won't be loaded@>; +done: if (file_opened) b_close(&tfm_file); +return g; +} + +@ There are programs called \.{TFtoPL} and \.{PLtoTF} that convert +between the \.{TFM} format and a symbolic property-list format +that can be easily edited. These programs contain extensive +diagnostic information, so \TeX\ does not have to bother giving +precise details about why it rejects a particular \.{TFM} file. +@.TFtoPL@> @.PLtoTF@> + +@d start_font_error_message print_err("Font ");sprint_cs(u); + print_char('=');print_file_name(nom, aire, empty_string); + if (s >= 0) + {@+print(" at ");print_scaled(s);print("pt"); + } + else if (s!=-1000) + {@+print(" scaled ");print_int(-s); + } + +@<Report that the font won't be loaded@>= +start_font_error_message; +@.Font x=xx not loadable...@> +if (file_opened) print(" not loadable: Bad metric (TFM) file"); +else print(" not loadable: Metric (TFM) file not found"); +help5("I wasn't able to read the size data for this font,",@/ +"so I will ignore the font specification.",@/ +"[Wizards can fix TFM files using TFtoPL/PLtoTF.]",@/ +"You might try inserting a different font spec;",@/ +"e.g., type `I\\font<same font id>=<substitute font name>'."); +error() + +@ @<Read and check...@>= +@<Open |tfm_file| for input@>; +@<Read the {\.{TFM}} size fields@>; +@<Use size fields to allocate font information@>; +@<Read the {\.{TFM}} header@>; +@<Read character data@>; +@<Read box dimensions@>; +@<Read ligature/kern program@>; +@<Read extensible character recipes@>; +@<Read font parameters@>; +@<Make final adjustments and |goto done|@>@; + +@ @<Open |tfm_file| for input@>= +file_opened=false; +pack_file_name(nom, empty_string,empty_string,".tfm"); /* \TeX\ Live */ +if (!b_open_in(&tfm_file)) abort; +file_opened=true + +@ Note: A malformed \.{TFM} file might be shorter than it claims to be; +thus |eof(tfm_file)| might be true when |read_font_info| refers to +|tfm_file.d| or when it says |get(tfm_file)|. If such circumstances +cause system error messages, you will have to defeat them somehow, +for example by defining |fget| to be `\ignorespaces|{@+get(tfm_file);| +|if (eof(tfm_file)) abort;} |\unskip'. +@^system dependencies@> + +@d fget get(tfm_file) +@d fbyte tfm_file.d +@d read_sixteen(A) {@+A=fbyte; + if (A > 127) abort; + fget;A=A*0400+fbyte; + } +@d store_four_quarters(A) {@+fget;a=fbyte;qw.b0=qi(a); + fget;b=fbyte;qw.b1=qi(b); + fget;c=fbyte;qw.b2=qi(c); + fget;d=fbyte;qw.b3=qi(d); + A=qw; + } + +@ @<Read the {\.{TFM}} size fields@>= +{@+read_sixteen(lf); +fget;read_sixteen(lh); +fget;read_sixteen(bc); +fget;read_sixteen(ec); +if ((bc > ec+1)||(ec > 255)) abort; +if (bc > 255) /*|bc==256| and |ec==255|*/ + {@+bc=1;ec=0; + } +fget;read_sixteen(nw); +fget;read_sixteen(nh); +fget;read_sixteen(nd); +fget;read_sixteen(ni); +fget;read_sixteen(nl); +fget;read_sixteen(nk); +fget;read_sixteen(ne); +fget;read_sixteen(np); +if (lf!=6+lh+(ec-bc+1)+nw+nh+nd+ni+nl+nk+ne+np) abort; +if ((nw==0)||(nh==0)||(nd==0)||(ni==0)) abort; +} + +@ The preliminary settings of the index-offset variables |char_base|, +|width_base|, |lig_kern_base|, |kern_base|, and |exten_base| will be +corrected later by subtracting |min_quarterword| from them; and we will +subtract 1 from |param_base| too. It's best to forget about such anomalies +until later. + +@<Use size fields to allocate font information@>= +lf=lf-6-lh; /*|lf| words should be loaded into |font_info|*/ +if (np < 7) lf=lf+7-np; /*at least seven parameters will appear*/ +if ((font_ptr==font_max)||(fmem_ptr+lf > font_mem_size)) + @<Apologize for not loading the font, |goto done|@>; +f=font_ptr+1; +char_base[f]=fmem_ptr-bc; +width_base[f]=char_base[f]+ec+1; +height_base[f]=width_base[f]+nw; +depth_base[f]=height_base[f]+nh; +italic_base[f]=depth_base[f]+nd; +lig_kern_base[f]=italic_base[f]+ni; +kern_base[f]=lig_kern_base[f]+nl-kern_base_offset; +exten_base[f]=kern_base[f]+kern_base_offset+nk; +param_base[f]=exten_base[f]+ne + +@ @<Apologize for not loading...@>= +{@+start_font_error_message; +print(" not loaded: Not enough room left"); +@.Font x=xx not loaded...@> +help4("I'm afraid I won't be able to make use of this font,",@/ +"because my memory for character-size data is too small.",@/ +"If you're really stuck, ask a wizard to enlarge me.",@/ +"Or maybe try `I\\font<same font id>=<name of loaded font>'."); +error();goto done; +} + +@ Only the first two words of the header are needed by \TeX82. + +@<Read the {\.{TFM}} header@>= +{@+if (lh < 2) abort; +store_four_quarters(font_check[f]); +fget;read_sixteen(z); /*this rejects a negative design size*/ +fget;z=z*0400+fbyte;fget;z=(z*020)+(fbyte/020); +if (z < unity) abort; +while (lh > 2) + {@+fget;fget;fget;fget;decr(lh); /*ignore the rest of the header*/ + } +font_dsize[f]=z; +if (s!=-1000) + if (s >= 0) z=s; + else z=xn_over_d(z,-s, 1000); +font_size[f]=z; +} + +@ @<Read character data@>= +for (k=fmem_ptr; k<=width_base[f]-1; k++) + {@+store_four_quarters(font_info[k].qqqq); + if ((a >= nw)||(b/020 >= nh)||(b%020 >= nd)|| + (c/4 >= ni)) abort; + switch (c%4) { + case lig_tag: if (d >= nl) abort;@+break; + case ext_tag: if (d >= ne) abort;@+break; + case list_tag: @<Check for charlist cycle@>@;@+break; + default:do_nothing; /*|no_tag|*/ + } + } + +@ We want to make sure that there is no cycle of characters linked together +by |list_tag| entries, since such a cycle would get \TeX\ into an endless +loop. If such a cycle exists, the routine here detects it when processing +the largest character code in the cycle. + +@d check_byte_range(A) {@+if ((A < bc)||(A > ec)) abort;@+} +@d current_character_being_worked_on k+bc-fmem_ptr + +@<Check for charlist cycle@>= +{@+check_byte_range(d); +while (d < current_character_being_worked_on) + {@+qw=char_info(f, d); + /*N.B.: not |qi(d)|, since |char_base[f]| hasn't been adjusted yet*/ + if (char_tag(qw)!=list_tag) goto not_found; + d=qo(rem_byte(qw)); /*next character on the list*/ + } +if (d==current_character_being_worked_on) abort; /*yes, there's a cycle*/ +not_found: ;} + +@ A |fix_word| whose four bytes are $(a,b,c,d)$ from left to right represents +the number +$$x=\left\{\vcenter{\halign{$#$,\hfil\qquad&if $#$\hfil\cr +b\cdot2^{-4}+c\cdot2^{-12}+d\cdot2^{-20}&a=0;\cr +-16+b\cdot2^{-4}+c\cdot2^{-12}+d\cdot2^{-20}&a=255.\cr}}\right.$$ +(No other choices of |a| are allowed, since the magnitude of a number in +design-size units must be less than 16.) We want to multiply this +quantity by the integer~|z|, which is known to be less than $2^{27}$. +If $|z|<2^{23}$, the individual multiplications $b\cdot z$, +$c\cdot z$, $d\cdot z$ cannot overflow; otherwise we will divide |z| by 2, +4, 8, or 16, to obtain a multiplier less than $2^{23}$, and we can +compensate for this later. If |z| has thereby been replaced by +$|z|^\prime=|z|/2^e$, let $\beta=2^{4-e}$; we shall compute +$$\lfloor(b+c\cdot2^{-8}+d\cdot2^{-16})\,z^\prime/\beta\rfloor$$ +if $a=0$, or the same quantity minus $\alpha=2^{4+e}z^\prime$ if $a=255$. +This calculation must be done exactly, in order to guarantee portability +of \TeX\ between computers. + +@d store_scaled(A) {@+fget;a=fbyte;fget;b=fbyte; + fget;c=fbyte;fget;d=fbyte;@/ + sw=(((((d*z)/0400)+(c*z))/0400)+(b*z))/beta; + if (a==0) A=sw;@+else if (a==255) A=sw-alpha;@+else abort; + } + +@<Read box dimensions@>= +{@+@<Replace |z| by $|z|^\prime$ and compute $\alpha,\beta$@>; +for (k=width_base[f]; k<=lig_kern_base[f]-1; k++) + store_scaled(font_info[k].sc); +if (font_info[width_base[f]].sc!=0) abort; /*\\{width}[0] must be zero*/ +if (font_info[height_base[f]].sc!=0) abort; /*\\{height}[0] must be zero*/ +if (font_info[depth_base[f]].sc!=0) abort; /*\\{depth}[0] must be zero*/ +if (font_info[italic_base[f]].sc!=0) abort; /*\\{italic}[0] must be zero*/ +} + +@ @<Replace |z|...@>= +{@+alpha=16; +while (z >= 040000000) + {@+z=z/2;alpha=alpha+alpha; + } +beta=256/alpha;alpha=alpha*z; +} + +@ @d check_existence(A) @t@>@;@/ + {@+check_byte_range(A); + qw=char_info(f, A); /*N.B.: not |qi(A)|*/ + if (!char_exists(qw)) abort; + } + +@<Read ligature/kern program@>= +bch_label=077777;bchar=256; +if (nl > 0) + {@+for (k=lig_kern_base[f]; k<=kern_base[f]+kern_base_offset-1; k++) + {@+store_four_quarters(font_info[k].qqqq); + if (a > 128) + {@+if (256*c+d >= nl) abort; + if (a==255) if (k==lig_kern_base[f]) bchar=b; + } + else{@+if (b!=bchar) check_existence(b); + if (c < 128) check_existence(d)@; /*check ligature*/ + else if (256*(c-128)+d >= nk) abort; /*check kern*/ + if (a < 128) if (k-lig_kern_base[f]+a+1 >= nl) abort; + } + } + if (a==255) bch_label=256*c+d; + } +for (k=kern_base[f]+kern_base_offset; k<=exten_base[f]-1; k++) + store_scaled(font_info[k].sc); + +@ @<Read extensible character recipes@>= +for (k=exten_base[f]; k<=param_base[f]-1; k++) + {@+store_four_quarters(font_info[k].qqqq); + if (a!=0) check_existence(a); + if (b!=0) check_existence(b); + if (c!=0) check_existence(c); + check_existence(d); + } + +@ We check to see that the \.{TFM} file doesn't end prematurely; but +no error message is given for files having more than |lf| words. + +@<Read font parameters@>= +{@+for (k=1; k<=np; k++) + if (k==1) /*the |slant| parameter is a pure number*/ + {@+fget;sw=fbyte;if (sw > 127) sw=sw-256; + fget;sw=sw*0400+fbyte;fget;sw=sw*0400+fbyte; + fget;font_info[param_base[f]].sc= + (sw*020)+(fbyte/020); + } + else store_scaled(font_info[param_base[f]+k-1].sc); +if (eof(tfm_file)) abort; +for (k=np+1; k<=7; k++) font_info[param_base[f]+k-1].sc=0; +} + +@ Now to wrap it up, we have checked all the necessary things about the \.{TFM} +file, and all we need to do is put the finishing touches on the data for +the new font. + +@d adjust(A) A[f]=qo(A[f]) + /*correct for the excess |min_quarterword| that was added*/ + +@<Make final adjustments...@>= +if (np >= 7) font_params[f]=np;@+else font_params[f]=7; +hyphen_char[f]=default_hyphen_char;skew_char[f]=default_skew_char; +if (bch_label < nl) bchar_label[f]=bch_label+lig_kern_base[f]; +else bchar_label[f]=non_address; +font_bchar[f]=qi(bchar); +font_false_bchar[f]=qi(bchar); +if (bchar <= ec) if (bchar >= bc) + {@+qw=char_info(f, bchar); /*N.B.: not |qi(bchar)|*/ + if (char_exists(qw)) font_false_bchar[f]=non_char; + } +font_name[f]=nom; +font_area[f]=aire; +font_bc[f]=bc;font_ec[f]=ec;font_glue[f]=null; +adjust(char_base);adjust(width_base);adjust(lig_kern_base); +adjust(kern_base);adjust(exten_base); +decr(param_base[f]); +fmem_ptr=fmem_ptr+lf;font_ptr=f;g=f;goto done + +@ Before we forget about the format of these tables, let's deal with two +of \TeX's basic scanning routines related to font information. + +@<Declare procedures that scan font-related stuff@>= +static void scan_font_ident(void) +{@+internal_font_number f; +halfword @!m; +@<Get the next non-blank non-call...@>; +if (cur_cmd==def_font) f=cur_font; +else if (cur_cmd==set_font) f=cur_chr; +else if (cur_cmd==def_family) + {@+m=cur_chr;scan_four_bit_int();f=equiv(m+cur_val); + } +else{@+print_err("Missing font identifier"); +@.Missing font identifier@> + help2("I was looking for a control sequence whose",@/ + "current meaning has been defined by \\font."); + back_error();f=null_font; + } +cur_val=f; +} + +@ The following routine is used to implement `\.{\\fontdimen} |n| |f|'. +The boolean parameter |writing| is set |true| if the calling program +intends to change the parameter value. + +@<Declare procedures that scan font-related stuff@>= +static void find_font_dimen(bool @!writing) + /*sets |cur_val| to |font_info| location*/ +{@+internal_font_number f; +int @!n; /*the parameter number*/ +scan_int();n=cur_val;scan_font_ident();f=cur_val; +if (n <= 0) cur_val=fmem_ptr; +else{@+if (writing&&(n <= space_shrink_code)&&@| + (n >= space_code)&&(font_glue[f]!=null)) + {@+delete_glue_ref(font_glue[f]); + font_glue[f]=null; + } + if (n > font_params[f]) + if (f < font_ptr) cur_val=fmem_ptr; + else@<Increase the number of parameters in the last font@>@; + else cur_val=n+param_base[f]; + } +@<Issue an error message if |cur_val=fmem_ptr|@>; +} + +@ @<Issue an error message if |cur_val=fmem_ptr|@>= +if (cur_val==fmem_ptr) + {@+print_err("Font ");printn_esc(font_id_text(f)); + print(" has only ");print_int(font_params[f]); + print(" fontdimen parameters"); +@.Font x has only...@> + help2("To increase the number of font parameters, you must",@/ + "use \\fontdimen immediately after the \\font is loaded."); + error(); + } + +@ @<Increase the number of parameters...@>= +{@+@/do@+{if (fmem_ptr==font_mem_size) + overflow("font memory", font_mem_size); +@:TeX capacity exceeded font memory}{\quad font memory@> +font_info[fmem_ptr].sc=0;incr(fmem_ptr);incr(font_params[f]); +}@+ while (!(n==font_params[f])); +cur_val=fmem_ptr-1; /*this equals |param_base[f]+font_params[f]|*/ +} + +@ When \TeX\ wants to typeset a character that doesn't exist, the +character node is not created; thus the output routine can assume +that characters exist when it sees them. The following procedure +prints a warning message unless the user has suppressed it. + +@p static void char_warning(internal_font_number @!f, eight_bits @!c) +{@+int old_setting; /*saved value of |tracing_online|*/ +if (tracing_lost_chars > 0) + {@+old_setting=tracing_online; + if (eTeX_ex&&(tracing_lost_chars > 1)) tracing_online=1; + {@+begin_diagnostic(); + print_nl("Missing character: There is no "); +@.Missing character@> + print_ASCII(c);print(" in font "); + slow_print(font_name[f]);print_char('!');end_diagnostic(false); + } + tracing_online=old_setting; + } +} + +@ Here is a function that returns a pointer to a character node for a +given character in a given font. If that character doesn't exist, +|null| is returned instead. + +@p static pointer new_character(internal_font_number @!f, eight_bits @!c) +{@+ +pointer p; /*newly allocated node*/ +if (font_bc[f] <= c) if (font_ec[f] >= c) + if (char_exists(char_info(f, qi(c)))) + {@+p=get_avail();font(p)=f;character(p)=qi(c); + return p; + } +char_warning(f, c); +return null; +} + +@* Device-independent file format. +The most important output produced by a run of \TeX\ is the ``device +independent'' (\.{DVI}) file that specifies where characters and rules +are to appear on printed pages. The form of these files was designed by +David R. Fuchs in 1979. Almost any reasonable typesetting device can be +@^Fuchs, David Raymond@> +@:DVI\_files}{\.{DVI} files@> +driven by a program that takes \.{DVI} files as input, and dozens of such +\.{DVI}-to-whatever programs have been written. Thus, it is possible to +print the output of \TeX\ on many different kinds of equipment, using \TeX\ +as a device-independent ``front end.'' + +A \.{DVI} file is a stream of 8-bit bytes, which may be regarded as a +series of commands in a machine-like language. The first byte of each command +is the operation code, and this code is followed by zero or more bytes +that provide parameters to the command. The parameters themselves may consist +of several consecutive bytes; for example, the `|set_rule|' command has two +parameters, each of which is four bytes long. Parameters are usually +regarded as nonnegative integers; but four-byte-long parameters, +and shorter parameters that denote distances, can be +either positive or negative. Such parameters are given in two's complement +notation. For example, a two-byte-long distance parameter has a value between +$-2^{15}$ and $2^{15}-1$. As in \.{TFM} files, numbers that occupy +more than one byte position appear in BigEndian order. + +A \.{DVI} file consists of a ``preamble,'' followed by a sequence of one +or more ``pages,'' followed by a ``postamble.'' The preamble is simply a +|pre| command, with its parameters that define the dimensions used in the +file; this must come first. Each ``page'' consists of a |bop| command, +followed by any number of other commands that tell where characters are to +be placed on a physical page, followed by an |eop| command. The pages +appear in the order that \TeX\ generated them. If we ignore |nop| commands +and \\{fnt\_def} commands (which are allowed between any two commands in +the file), each |eop| command is immediately followed by a |bop| command, +or by a |post| command; in the latter case, there are no more pages in the +file, and the remaining bytes form the postamble. Further details about +the postamble will be explained later. + +Some parameters in \.{DVI} commands are ``pointers.'' These are four-byte +quantities that give the location number of some other byte in the file; +the first byte is number~0, then comes number~1, and so on. For example, +one of the parameters of a |bop| command points to the previous |bop|; +this makes it feasible to read the pages in backwards order, in case the +results are being directed to a device that stacks its output face up. +Suppose the preamble of a \.{DVI} file occupies bytes 0 to 99. Now if the +first page occupies bytes 100 to 999, say, and if the second +page occupies bytes 1000 to 1999, then the |bop| that starts in byte 1000 +points to 100 and the |bop| that starts in byte 2000 points to 1000. (The +very first |bop|, i.e., the one starting in byte 100, has a pointer of~$-1$.) + +@ The \.{DVI} format is intended to be both compact and easily interpreted +by a machine. Compactness is achieved by making most of the information +implicit instead of explicit. When a \.{DVI}-reading program reads the +commands for a page, it keeps track of several quantities: (a)~The current +font |f| is an integer; this value is changed only +by \\{fnt} and \\{fnt\_num} commands. (b)~The current position on the page +is given by two numbers called the horizontal and vertical coordinates, +|h| and |v|. Both coordinates are zero at the upper left corner of the page; +moving to the right corresponds to increasing the horizontal coordinate, and +moving down corresponds to increasing the vertical coordinate. Thus, the +coordinates are essentially Cartesian, except that vertical directions are +flipped; the Cartesian version of |(h, v)| would be |(h,-v)|. (c)~The +current spacing amounts are given by four numbers |w|, |x|, |y|, and |z|, +where |w| and~|x| are used for horizontal spacing and where |y| and~|z| +are used for vertical spacing. (d)~There is a stack containing +|(h, v, w, x, y, z)| values; the \.{DVI} commands |push| and |pop| are used to +change the current level of operation. Note that the current font~|f| is +not pushed and popped; the stack contains only information about +positioning. + +The values of |h|, |v|, |w|, |x|, |y|, and |z| are signed integers having up +to 32 bits, including the sign. Since they represent physical distances, +there is a small unit of measurement such that increasing |h| by~1 means +moving a certain tiny distance to the right. The actual unit of +measurement is variable, as explained below; \TeX\ sets things up so that +its \.{DVI} output is in sp units, i.e., scaled points, in agreement with +all the |scaled| dimensions in \TeX's data structures. + +@ Here is a list of all the commands that may appear in a \.{DVI} file. Each +command is specified by its symbolic name (e.g., |bop|), its opcode byte +(e.g., 139), and its parameters (if any). The parameters are followed +by a bracketed number telling how many bytes they occupy; for example, +`|p[4]|' means that parameter |p| is four bytes long. + +\yskip\hang|set_char_0| 0. Typeset character number~0 from font~|f| +such that the reference point of the character is at |(h, v)|. Then +increase |h| by the width of that character. Note that a character may +have zero or negative width, so one cannot be sure that |h| will advance +after this command; but |h| usually does increase. + +\yskip\hang\\{set\_char\_1} through \\{set\_char\_127} (opcodes 1 to 127). +Do the operations of |set_char_0|; but use the character whose number +matches the opcode, instead of character~0. + +\yskip\hang|set1| 128 |c[1]|. Same as |set_char_0|, except that character +number~|c| is typeset. \TeX82 uses this command for characters in the +range |128 <= c < 256|. + +\yskip\hang|@!set2| 129 |c[2]|. Same as |set1|, except that |c|~is two +bytes long, so it is in the range |0 <= c < 65536|. \TeX82 never uses this +command, but it should come in handy for extensions of \TeX\ that deal +with oriental languages. +@^oriental characters@>@^Chinese characters@>@^Japanese characters@> + +\yskip\hang|@!set3| 130 |c[3]|. Same as |set1|, except that |c|~is three +bytes long, so it can be as large as $2^{24}-1$. Not even the Chinese +language has this many characters, but this command might prove useful +in some yet unforeseen extension. + +\yskip\hang|@!set4| 131 |c[4]|. Same as |set1|, except that |c|~is four +bytes long. Imagine that. + +\yskip\hang|set_rule| 132 |a[4]| |b[4]|. Typeset a solid black rectangle +of height~|a| and width~|b|, with its bottom left corner at |(h, v)|. Then +set |h=h+b|. If either |a <= 0| or |b <= 0|, nothing should be typeset. Note +that if |b < 0|, the value of |h| will decrease even though nothing else happens. +See below for details about how to typeset rules so that consistency with +\MF\ is guaranteed. + +\yskip\hang|@!put1| 133 |c[1]|. Typeset character number~|c| from font~|f| +such that the reference point of the character is at |(h, v)|. (The `put' +commands are exactly like the `set' commands, except that they simply put out a +character or a rule without moving the reference point afterwards.) + +\yskip\hang|@!put2| 134 |c[2]|. Same as |set2|, except that |h| is not changed. + +\yskip\hang|@!put3| 135 |c[3]|. Same as |set3|, except that |h| is not changed. + +\yskip\hang|@!put4| 136 |c[4]|. Same as |set4|, except that |h| is not changed. + +\yskip\hang|put_rule| 137 |a[4]| |b[4]|. Same as |set_rule|, except that +|h| is not changed. + +\yskip\hang|nop| 138. No operation, do nothing. Any number of |nop|'s +may occur between \.{DVI} commands, but a |nop| cannot be inserted between +a command and its parameters or between two parameters. + +\yskip\hang|bop| 139 $c_0[4]$ $c_1[4]$ $\ldots$ $c_9[4]$ $p[4]$. Beginning +of a page: Set |(h, v, w, x, y, z)=(0, 0, 0, 0, 0, 0)| and set the stack empty. Set +the current font |f| to an undefined value. The ten $c_i$ parameters hold +the values of \.{\\count0} $\ldots$ \.{\\count9} in \TeX\ at the time +\.{\\shipout} was invoked for this page; they can be used to identify +pages, if a user wants to print only part of a \.{DVI} file. The parameter +|p| points to the previous |bop| in the file; the first +|bop| has $p=-1$. + +\yskip\hang|eop| 140. End of page: Print what you have read since the +previous |bop|. At this point the stack should be empty. (The \.{DVI}-reading +programs that drive most output devices will have kept a buffer of the +material that appears on the page that has just ended. This material is +largely, but not entirely, in order by |v| coordinate and (for fixed |v|) by +|h|~coordinate; so it usually needs to be sorted into some order that is +appropriate for the device in question.) + +\yskip\hang|push| 141. Push the current values of |(h, v, w, x, y, z)| onto the +top of the stack; do not change any of these values. Note that |f| is +not pushed. + +\yskip\hang|pop| 142. Pop the top six values off of the stack and assign +them respectively to |(h, v, w, x, y, z)|. The number of pops should never +exceed the number of pushes, since it would be highly embarrassing if the +stack were empty at the time of a |pop| command. + +\yskip\hang|right1| 143 |b[1]|. Set |h=h+b|, i.e., move right |b| units. +The parameter is a signed number in two's complement notation, |-128 <= b < 128|; +if |b < 0|, the reference point moves left. + +\yskip\hang|@!right2| 144 |b[2]|. Same as |right1|, except that |b| is a +two-byte quantity in the range |-32768 <= b < 32768|. + +\yskip\hang|@!right3| 145 |b[3]|. Same as |right1|, except that |b| is a +three-byte quantity in the range |@t$-2^{23}$@> <= b < @t$2^{23}$@>|. + +\yskip\hang|@!right4| 146 |b[4]|. Same as |right1|, except that |b| is a +four-byte quantity in the range |@t$-2^{31}$@> <= b < @t$2^{31}$@>|. + +\yskip\hang|w0| 147. Set |h=h+w|; i.e., move right |w| units. With luck, +this parameterless command will usually suffice, because the same kind of motion +will occur several times in succession; the following commands explain how +|w| gets particular values. + +\yskip\hang|w1| 148 |b[1]|. Set |w=b| and |h=h+b|. The value of |b| is a +signed quantity in two's complement notation, |-128 <= b < 128|. This command +changes the current |w|~spacing and moves right by |b|. + +\yskip\hang|@!w2| 149 |b[2]|. Same as |w1|, but |b| is two bytes long, +|-32768 <= b < 32768|. + +\yskip\hang|@!w3| 150 |b[3]|. Same as |w1|, but |b| is three bytes long, +|@t$-2^{23}$@> <= b < @t$2^{23}$@>|. + +\yskip\hang|@!w4| 151 |b[4]|. Same as |w1|, but |b| is four bytes long, +|@t$-2^{31}$@> <= b < @t$2^{31}$@>|. + +\yskip\hang|x0| 152. Set |h=h+x|; i.e., move right |x| units. The `|x|' +commands are like the `|w|' commands except that they involve |x| instead +of |w|. + +\yskip\hang|x1| 153 |b[1]|. Set |x=b| and |h=h+b|. The value of |b| is a +signed quantity in two's complement notation, |-128 <= b < 128|. This command +changes the current |x|~spacing and moves right by |b|. + +\yskip\hang|@!x2| 154 |b[2]|. Same as |x1|, but |b| is two bytes long, +|-32768 <= b < 32768|. + +\yskip\hang|@!x3| 155 |b[3]|. Same as |x1|, but |b| is three bytes long, +|@t$-2^{23}$@> <= b < @t$2^{23}$@>|. + +\yskip\hang|@!x4| 156 |b[4]|. Same as |x1|, but |b| is four bytes long, +|@t$-2^{31}$@> <= b < @t$2^{31}$@>|. + +\yskip\hang|down1| 157 |a[1]|. Set |v=v+a|, i.e., move down |a| units. +The parameter is a signed number in two's complement notation, |-128 <= a < 128|; +if |a < 0|, the reference point moves up. + +\yskip\hang|@!down2| 158 |a[2]|. Same as |down1|, except that |a| is a +two-byte quantity in the range |-32768 <= a < 32768|. + +\yskip\hang|@!down3| 159 |a[3]|. Same as |down1|, except that |a| is a +three-byte quantity in the range |@t$-2^{23}$@> <= a < @t$2^{23}$@>|. + +\yskip\hang|@!down4| 160 |a[4]|. Same as |down1|, except that |a| is a +four-byte quantity in the range |@t$-2^{31}$@> <= a < @t$2^{31}$@>|. + +\yskip\hang|y0| 161. Set |v=v+y|; i.e., move down |y| units. With luck, +this parameterless command will usually suffice, because the same kind of motion +will occur several times in succession; the following commands explain how +|y| gets particular values. + +\yskip\hang|y1| 162 |a[1]|. Set |y=a| and |v=v+a|. The value of |a| is a +signed quantity in two's complement notation, |-128 <= a < 128|. This command +changes the current |y|~spacing and moves down by |a|. + +\yskip\hang|@!y2| 163 |a[2]|. Same as |y1|, but |a| is two bytes long, +|-32768 <= a < 32768|. + +\yskip\hang|@!y3| 164 |a[3]|. Same as |y1|, but |a| is three bytes long, +|@t$-2^{23}$@> <= a < @t$2^{23}$@>|. + +\yskip\hang|@!y4| 165 |a[4]|. Same as |y1|, but |a| is four bytes long, +|@t$-2^{31}$@> <= a < @t$2^{31}$@>|. + +\yskip\hang|z0| 166. Set |v=v+z|; i.e., move down |z| units. The `|z|' commands +are like the `|y|' commands except that they involve |z| instead of |y|. + +\yskip\hang|z1| 167 |a[1]|. Set |z=a| and |v=v+a|. The value of |a| is a +signed quantity in two's complement notation, |-128 <= a < 128|. This command +changes the current |z|~spacing and moves down by |a|. + +\yskip\hang|@!z2| 168 |a[2]|. Same as |z1|, but |a| is two bytes long, +|-32768 <= a < 32768|. + +\yskip\hang|@!z3| 169 |a[3]|. Same as |z1|, but |a| is three bytes long, +|@t$-2^{23}$@> <= a < @t$2^{23}$@>|. + +\yskip\hang|@!z4| 170 |a[4]|. Same as |z1|, but |a| is four bytes long, +|@t$-2^{31}$@> <= a < @t$2^{31}$@>|. + +\yskip\hang|fnt_num_0| 171. Set |f=0|. Font 0 must previously have been +defined by a \\{fnt\_def} instruction, as explained below. + +\yskip\hang\\{fnt\_num\_1} through \\{fnt\_num\_63} (opcodes 172 to 234). Set +|f=1|, \dots, \hbox{|f=63|}, respectively. + +\yskip\hang|fnt1| 235 |k[1]|. Set |f=k|. \TeX82 uses this command for font +numbers in the range |64 <= k < 256|. + +\yskip\hang|@!fnt2| 236 |k[2]|. Same as |fnt1|, except that |k|~is two +bytes long, so it is in the range |0 <= k < 65536|. \TeX82 never generates this +command, but large font numbers may prove useful for specifications of +color or texture, or they may be used for special fonts that have fixed +numbers in some external coding scheme. + +\yskip\hang|@!fnt3| 237 |k[3]|. Same as |fnt1|, except that |k|~is three +bytes long, so it can be as large as $2^{24}-1$. + +\yskip\hang|@!fnt4| 238 |k[4]|. Same as |fnt1|, except that |k|~is four +bytes long; this is for the really big font numbers (and for the negative ones). + +\yskip\hang|xxx1| 239 |k[1]| |x[k]|. This command is undefined in +general; it functions as a $(k+2)$-byte |nop| unless special \.{DVI}-reading +programs are being used. \TeX82 generates |xxx1| when a short enough +\.{\\special} appears, setting |k| to the number of bytes being sent. It +is recommended that |x| be a string having the form of a keyword followed +by possible parameters relevant to that keyword. + +\yskip\hang|@!xxx2| 240 |k[2]| |x[k]|. Like |xxx1|, but |0 <= k < 65536|. + +\yskip\hang|@!xxx3| 241 |k[3]| |x[k]|. Like |xxx1|, but |0 <= k < @t$2^{24}$@>|. + +\yskip\hang|xxx4| 242 |k[4]| |x[k]|. Like |xxx1|, but |k| can be ridiculously +large. \TeX82 uses |xxx4| when sending a string of length 256 or more. + +\yskip\hang|fnt_def1| 243 |k[1]| |c[4]| |s[4]| |d[4]| |a[1]| |l[1]| |n[a+l]|. +Define font |k|, where |0 <= k < 256|; font definitions will be explained shortly. + +\yskip\hang|@!fnt_def2| 244 |k[2]| |c[4]| |s[4]| |d[4]| |a[1]| |l[1]| |n[a+l]|. +Define font |k|, where |0 <= k < 65536|. + +\yskip\hang|@!fnt_def3| 245 |k[3]| |c[4]| |s[4]| |d[4]| |a[1]| |l[1]| |n[a+l]|. +Define font |k|, where |0 <= k < @t$2^{24}$@>|. + +\yskip\hang|@!fnt_def4| 246 |k[4]| |c[4]| |s[4]| |d[4]| |a[1]| |l[1]| |n[a+l]|. +Define font |k|, where |@t$-2^{31}$@> <= k < @t$2^{31}$@>|. + +\yskip\hang|pre| 247 |i[1]| |num[4]| |den[4]| |mag[4]| |k[1]| |x[k]|. +Beginning of the preamble; this must come at the very beginning of the +file. Parameters |i|, |num|, |den|, |mag|, |k|, and |x| are explained below. + +\yskip\hang|post| 248. Beginning of the postamble, see below. + +\yskip\hang|post_post| 249. Ending of the postamble, see below. + +\yskip\noindent Commands 250--255 are undefined at the present time. + +@ @d set_char_0 0 /*typeset character 0 and move right*/ +@d set1 128 /*typeset a character and move right*/ +@d set_rule 132 /*typeset a rule and move right*/ +@d put_rule 137 /*typeset a rule*/ +@d nop 138 /*no operation*/ +@d bop 139 /*beginning of page*/ +@d eop 140 /*ending of page*/ +@d push 141 /*save the current positions*/ +@d pop 142 /*restore previous positions*/ +@d right1 143 /*move right*/ +@d w0 147 /*move right by |w|*/ +@d w1 148 /*move right and set |w|*/ +@d x0 152 /*move right by |x|*/ +@d x1 153 /*move right and set |x|*/ +@d down1 157 /*move down*/ +@d y0 161 /*move down by |y|*/ +@d y1 162 /*move down and set |y|*/ +@d z0 166 /*move down by |z|*/ +@d z1 167 /*move down and set |z|*/ +@d fnt_num_0 171 /*set current font to 0*/ +@d fnt1 235 /*set current font*/ +@d xxx1 239 /*extension to \.{DVI} primitives*/ +@d xxx4 242 /*potentially long extension to \.{DVI} primitives*/ +@d fnt_def1 243 /*define the meaning of a font number*/ +@d pre 247 /*preamble*/ +@d post 248 /*postamble beginning*/ +@d post_post 249 /*postamble ending*/ + +@ The preamble contains basic information about the file as a whole. As +stated above, there are six parameters: +$$\hbox{|@!i[1]| |@!num[4]| |@!den[4]| |@!mag[4]| |@!k[1]| |@!x[k]|.}$$ +The |i| byte identifies \.{DVI} format; currently this byte is always set +to~2. (The value |i==3| is currently used for an extended format that +allows a mixture of right-to-left and left-to-right typesetting. +Some day we will set |i==4|, when \.{DVI} format makes another +incompatible change---perhaps in the year 2048.) + +The next two parameters, |num| and |den|, are positive integers that define +the units of measurement; they are the numerator and denominator of a +fraction by which all dimensions in the \.{DVI} file could be multiplied +in order to get lengths in units of $10^{-7}$ meters. Since $\rm 7227{pt} = +254{cm}$, and since \TeX\ works with scaled points where there are $2^{16}$ +sp in a point, \TeX\ sets +$|num|/|den|=(254\cdot10^5)/(7227\cdot2^{16})=25400000/473628672$. +@^sp@> + +The |mag| parameter is what \TeX\ calls \.{\\mag}, i.e., 1000 times the +desired magnification. The actual fraction by which dimensions are +multiplied is therefore $|mag|\cdot|num|/1000|den|$. Note that if a \TeX\ +source document does not call for any `\.{true}' dimensions, and if you +change it only by specifying a different \.{\\mag} setting, the \.{DVI} +file that \TeX\ creates will be completely unchanged except for the value +of |mag| in the preamble and postamble. (Fancy \.{DVI}-reading programs allow +users to override the |mag|~setting when a \.{DVI} file is being printed.) + +Finally, |k| and |x| allow the \.{DVI} writer to include a comment, which is not +interpreted further. The length of comment |x| is |k|, where |0 <= k < 256|. + +@d id_byte 2 /*identifies the kind of \.{DVI} files described here*/ + +@ Font definitions for a given font number |k| contain further parameters +$$\hbox{|c[4]| |s[4]| |d[4]| |a[1]| |l[1]| |n[a+l]|.}$$ +The four-byte value |c| is the check sum that \TeX\ found in the \.{TFM} +file for this font; |c| should match the check sum of the font found by +programs that read this \.{DVI} file. +@^check sum@> + +Parameter |s| contains a fixed-point scale factor that is applied to +the character widths in font |k|; font dimensions in \.{TFM} files and +other font files are relative to this quantity, which is called the +``at size'' elsewhere in this documentation. The value of |s| is +always positive and less than $2^{27}$. It is given in the same units +as the other \.{DVI} dimensions, i.e., in sp when \TeX82 has made the +file. Parameter |d| is similar to |s|; it is the ``design size,'' and +(like~|s|) it is given in \.{DVI} units. Thus, font |k| is to be used +at $|mag|\cdot s/1000d$ times its normal size. + +The remaining part of a font definition gives the external name of the font, +which is an ASCII string of length |a+l|. The number |a| is the length +of the ``area'' or directory, and |l| is the length of the font name itself; +the standard local system font area is supposed to be used when |a==0|. +The |n| field contains the area in its first |a| bytes. + +Font definitions must appear before the first use of a particular font number. +Once font |k| is defined, it must not be defined again; however, we +shall see below that font definitions appear in the postamble as well as +in the pages, so in this sense each font number is defined exactly twice, +if at all. Like |nop| commands, font definitions can +appear before the first |bop|, or between an |eop| and a |bop|. + +@ Sometimes it is desirable to make horizontal or vertical rules line up +precisely with certain features in characters of a font. It is possible to +guarantee the correct matching between \.{DVI} output and the characters +generated by \MF\ by adhering to the following principles: (1)~The \MF\ +characters should be positioned so that a bottom edge or left edge that is +supposed to line up with the bottom or left edge of a rule appears at the +reference point, i.e., in row~0 and column~0 of the \MF\ raster. This +ensures that the position of the rule will not be rounded differently when +the pixel size is not a perfect multiple of the units of measurement in +the \.{DVI} file. (2)~A typeset rule of height $a>0$ and width $b>0$ +should be equivalent to a \MF-generated character having black pixels in +precisely those raster positions whose \MF\ coordinates satisfy +|0 <= x < @t$\alpha$@>b| and |0 <= y < @t$\alpha$@>a|, where $\alpha$ is the number +of pixels per \.{DVI} unit. +@:METAFONT}{\MF@> +@^alignment of rules with characters@> +@^rules aligning with characters@> + +@ The last page in a \.{DVI} file is followed by `|post|'; this command +introduces the postamble, which summarizes important facts that \TeX\ has +accumulated about the file, making it possible to print subsets of the data +with reasonable efficiency. The postamble has the form +$$\vbox{\halign{\hbox{#\hfil}\cr + |post| |p[4]| |num[4]| |den[4]| |mag[4]| |l[4]| |u[4]| |s[2]| |t[2]|\cr + $\langle\,$font definitions$\,\rangle$\cr + |post_post| |q[4]| |i[1]| 223's$[{\G}4]$\cr}}$$ +Here |p| is a pointer to the final |bop| in the file. The next three +parameters, |num|, |den|, and |mag|, are duplicates of the quantities that +appeared in the preamble. + +Parameters |l| and |u| give respectively the height-plus-depth of the tallest +page and the width of the widest page, in the same units as other dimensions +of the file. These numbers might be used by a \.{DVI}-reading program to +position individual ``pages'' on large sheets of film or paper; however, +the standard convention for output on normal size paper is to position each +page so that the upper left-hand corner is exactly one inch from the left +and the top. Experience has shown that it is unwise to design \.{DVI}-to-printer +software that attempts cleverly to center the output; a fixed position of +the upper left corner is easiest for users to understand and to work with. +Therefore |l| and~|u| are often ignored. + +Parameter |s| is the maximum stack depth (i.e., the largest excess of +|push| commands over |pop| commands) needed to process this file. Then +comes |t|, the total number of pages (|bop| commands) present. + +The postamble continues with font definitions, which are any number of +\\{fnt\_def} commands as described above, possibly interspersed with |nop| +commands. Each font number that is used in the \.{DVI} file must be defined +exactly twice: Once before it is first selected by a \\{fnt} command, and once +in the postamble. + +@ The last part of the postamble, following the |post_post| byte that +signifies the end of the font definitions, contains |q|, a pointer to the +|post| command that started the postamble. An identification byte, |i|, +comes next; this currently equals~2, as in the preamble. + +The |i| byte is followed by four or more bytes that are all equal to +the decimal number 223 (i.e., 0337 in octal). \TeX\ puts out four to seven of +these trailing bytes, until the total length of the file is a multiple of +four bytes, since this works out best on machines that pack four bytes per +word; but any number of 223's is allowed, as long as there are at least four +of them. In effect, 223 is a sort of signature that is added at the very end. +@^Fuchs, David Raymond@> + +This curious way to finish off a \.{DVI} file makes it feasible for +\.{DVI}-reading programs to find the postamble first, on most computers, +even though \TeX\ wants to write the postamble last. Most operating +systems permit random access to individual words or bytes of a file, so +the \.{DVI} reader can start at the end and skip backwards over the 223's +until finding the identification byte. Then it can back up four bytes, read +|q|, and move to byte |q| of the file. This byte should, of course, +contain the value 248 (|post|); now the postamble can be read, so the +\.{DVI} reader can discover all the information needed for typesetting the +pages. Note that it is also possible to skip through the \.{DVI} file at +reasonably high speed to locate a particular page, if that proves +desirable. This saves a lot of time, since \.{DVI} files used in production +jobs tend to be large. + +Unfortunately, however, standard \PASCAL\ does not include the ability to +@^system dependencies@> +access a random position in a file, or even to determine the length of a file. +Almost all systems nowadays provide the necessary capabilities, so \.{DVI} +format has been designed to work most efficiently with modern operating systems. +But if \.{DVI} files have to be processed under the restrictions of standard +\PASCAL, one can simply read them from front to back, since the necessary +header information is present in the preamble and in the font definitions. +(The |l| and |u| and |s| and |t| parameters, which appear only in the +postamble, are ``frills'' that are handy but not absolutely necessary.) + +@* Shipping pages out. +After considering \TeX's eyes and stomach, we come now to the bowels. +@^bowels@> + +The |ship_out| procedure is given a pointer to a box; its mission is +to describe that box in \.{DVI} form, outputting a ``page'' to |dvi_file|. +The \.{DVI} coordinates $(h,v)=(0,0)$ should correspond to the upper left +corner of the box being shipped. + +Since boxes can be inside of boxes inside of boxes, the main work of +|ship_out| is done by two mutually recursive routines, |hlist_out| +and |vlist_out|, which traverse the hlists and vlists inside of horizontal +and vertical boxes. + +As individual pages are being processed, we need to accumulate +information about the entire set of pages, since such statistics must be +reported in the postamble. The global variables |total_pages|, |max_v|, +|max_h|, |max_push|, and |last_bop| are used to record this information. + +The variable |doing_leaders| is |true| while leaders are being output. +The variable |dead_cycles| contains the number of times an output routine +has been initiated since the last |ship_out|. + +A few additional global variables are also defined here for use in +|vlist_out| and |hlist_out|. They could have been local variables, but +that would waste stack space when boxes are deeply nested, since the +values of these variables are not needed during recursive calls. +@^recursion@> + +@<Glob...@>= +static int @!total_pages; /*the number of pages that have been shipped out*/ +static scaled @!max_v; /*maximum height-plus-depth of pages shipped so far*/ +static scaled @!max_h; /*maximum width of pages shipped so far*/ +static int @!max_push; /*deepest nesting of |push| commands encountered so far*/ +static int @!last_bop; /*location of previous |bop| in the \.{DVI} output*/ +static int @!dead_cycles; /*recent outputs that didn't ship anything out*/ +static bool @!doing_leaders; /*are we inside a leader box?*/ +@# +static quarterword @!c, @!f; /*character and font in current |char_node|*/ +static scaled @!rule_ht, @!rule_dp, @!rule_wd; /*size of current rule being output*/ +static pointer @!g; /*current glue specification*/ +static int @!lq, @!lr; /*quantities used in calculations for leaders*/ + +@ @<Set init...@>= +total_pages=0;max_v=0;max_h=0;max_push=0;last_bop=-1; +doing_leaders=false;dead_cycles=0;cur_s=-1; + +@ The \.{DVI} bytes are output to a buffer instead of being written directly +to the output file. This makes it possible to reduce the overhead of +subroutine calls, thereby measurably speeding up the computation, since +output of \.{DVI} bytes is part of \TeX's inner loop. And it has another +advantage as well, since we can change instructions in the buffer in order to +make the output more compact. For example, a `|down2|' command can be +changed to a `|y2|', thereby making a subsequent `|y0|' command possible, +saving two bytes. + +The output buffer is divided into two parts of equal size; the bytes found +in |dvi_buf[0 dotdot half_buf-1]| constitute the first half, and those in +|dvi_buf[half_buf dotdot dvi_buf_size-1]| constitute the second. The global +variable |dvi_ptr| points to the position that will receive the next +output byte. When |dvi_ptr| reaches |dvi_limit|, which is always equal +to one of the two values |half_buf| or |dvi_buf_size|, the half buffer that +is about to be invaded next is sent to the output and |dvi_limit| is +changed to its other value. Thus, there is always at least a half buffer's +worth of information present, except at the very beginning of the job. + +Bytes of the \.{DVI} file are numbered sequentially starting with 0; +the next byte to be generated will be number |dvi_offset+dvi_ptr|. +A byte is present in the buffer only if its number is | >= dvi_gone|. + +@<Types...@>= +typedef int16_t dvi_index; /*an index into the output buffer*/ + +@ Some systems may find it more efficient to make |dvi_buf| a || +array, since output of four bytes at once may be facilitated. +@^system dependencies@> + +@<Glob...@>= +static eight_bits @!dvi_buf[dvi_buf_size+1]; /*buffer for \.{DVI} output*/ +static dvi_index @!half_buf; /*half of |dvi_buf_size|*/ +static dvi_index @!dvi_limit; /*end of the current half buffer*/ +static dvi_index @!dvi_ptr; /*the next available buffer address*/ +static int @!dvi_offset; /*|dvi_buf_size| times the number of times the + output buffer has been fully emptied*/ +static int @!dvi_gone; /*the number of bytes already output to |dvi_file|*/ + +@ Initially the buffer is all in one piece; we will output half of it only +after it first fills up. + +@<Set init...@>= +half_buf=dvi_buf_size/2;dvi_limit=dvi_buf_size;dvi_ptr=0; +dvi_offset=0;dvi_gone=0; + +@ The actual output of |dvi_buf[a dotdot b]| to |dvi_file| is performed by calling +|write_dvi(a, b)|. For best results, this procedure should be optimized to +run as fast as possible on each particular system, since it is part of +\TeX's inner loop. It is safe to assume that |a| and |b+1| will both be +multiples of 4 when |write_dvi(a, b)| is called; therefore it is possible on +many machines to use efficient methods to pack four bytes per word and to +output an array of words with one system call. +@^system dependencies@> +@^inner loop@> +@^defecation@> + +@p static void write_dvi(dvi_index @!a, dvi_index @!b) +{@+int k; +for (k=a; k<=b; k++) pascal_write(dvi_file, "%c", dvi_buf[k]); +} + +@ To put a byte in the buffer without paying the cost of invoking a procedure +each time, we use the macro |dvi_out|. + +@d dvi_out(A) @+{@+dvi_buf[dvi_ptr]=A;incr(dvi_ptr); + if (dvi_ptr==dvi_limit) dvi_swap(); + } + +@p static void dvi_swap(void) /*outputs half of the buffer*/ +{@+if (dvi_limit==dvi_buf_size) + {@+write_dvi(0, half_buf-1);dvi_limit=half_buf; + dvi_offset=dvi_offset+dvi_buf_size;dvi_ptr=0; + } +else{@+write_dvi(half_buf, dvi_buf_size-1);dvi_limit=dvi_buf_size; + } +dvi_gone=dvi_gone+half_buf; +} + +@ Here is how we clean out the buffer when \TeX\ is all through; |dvi_ptr| +will be a multiple of~4. + +@<Empty the last bytes out of |dvi_buf|@>= +if (dvi_limit==half_buf) write_dvi(half_buf, dvi_buf_size-1); +if (dvi_ptr > 0) write_dvi(0, dvi_ptr-1) + +@ The |dvi_four| procedure outputs four bytes in two's complement notation, +without risking arithmetic overflow. + +@p static void dvi_four(int @!x) +{@+if (x >= 0) dvi_out(x/0100000000)@; +else{@+x=x+010000000000; + x=x+010000000000; + dvi_out((x/0100000000)+128); + } +x=x%0100000000;dvi_out(x/0200000); +x=x%0200000;dvi_out(x/0400); +dvi_out(x%0400); +} + +@ A mild optimization of the output is performed by the |dvi_pop| +routine, which issues a |pop| unless it is possible to cancel a +`|push| |pop|' pair. The parameter to |dvi_pop| is the byte address +following the old |push| that matches the new |pop|. + +@p static void dvi_pop(int @!l) +{@+if ((l==dvi_offset+dvi_ptr)&&(dvi_ptr > 0)) decr(dvi_ptr); +else dvi_out(pop); +} + +@ Here's a procedure that outputs a font definition. Since \TeX82 uses at +most 256 different fonts per job, |fnt_def1| is always used as the command code. + +@p static void dvi_font_def(internal_font_number @!f) +{@+int k; /*index into |str_pool|*/ +dvi_out(fnt_def1); +dvi_out(f-font_base-1);@/ +dvi_out(qo(font_check[f].b0)); +dvi_out(qo(font_check[f].b1)); +dvi_out(qo(font_check[f].b2)); +dvi_out(qo(font_check[f].b3));@/ +dvi_four(font_size[f]); +dvi_four(font_dsize[f]);@/ +dvi_out(length(font_area[f])); +dvi_out(length(font_name[f])); +@<Output the font name whose internal number is |f|@>; +} + +@ @<Output the font name whose internal number is |f|@>= +for (k=str_start[font_area[f]]; k<=str_start[font_area[f]+1]-1; k++) + dvi_out(so(str_pool[k])); +for (k=str_start[font_name[f]]; k<=str_start[font_name[f]+1]-1; k++) + dvi_out(so(str_pool[k])) + +@ Versions of \TeX\ intended for small computers might well choose to omit +the ideas in the next few parts of this program, since it is not really +necessary to optimize the \.{DVI} code by making use of the |w0|, |x0|, +|y0|, and |z0| commands. Furthermore, the algorithm that we are about to +describe does not pretend to give an optimum reduction in the length +of the \.{DVI} code; after all, speed is more important than compactness. +But the method is surprisingly effective, and it takes comparatively little +time. + +We can best understand the basic idea by first considering a simpler problem +that has the same essential characteristics. Given a sequence of digits, +say $3\,1\,4\,1\,5\,9\,2\,6\,5\,3\,5\,8\,9$, we want to assign subscripts +$d$, $y$, or $z$ to each digit so as to maximize the number of ``$y$-hits'' +and ``$z$-hits''; a $y$-hit is an instance of two appearances of the same +digit with the subscript $y$, where no $y$'s intervene between the two +appearances, and a $z$-hit is defined similarly. For example, the sequence +above could be decorated with subscripts as follows: +$$3_z\,1_y\,4_d\,1_y\,5_y\,9_d\,2_d\,6_d\,5_y\,3_z\,5_y\,8_d\,9_d.$$ +There are three $y$-hits ($1_y\ldots1_y$ and $5_y\ldots5_y\ldots5_y$) and +one $z$-hit ($3_z\ldots3_z$); there are no $d$-hits, since the two appearances +of $9_d$ have $d$'s between them, but we don't count $d$-hits so it doesn't +matter how many there are. These subscripts are analogous to the \.{DVI} +commands called \\{down}, $y$, and $z$, and the digits are analogous to +different amounts of vertical motion; a $y$-hit or $z$-hit corresponds to +the opportunity to use the one-byte commands |y0| or |z0| in a \.{DVI} file. + +\TeX's method of assigning subscripts works like this: Append a new digit, +say $\delta$, to the right of the sequence. Now look back through the +sequence until one of the following things happens: (a)~You see +$\delta_y$ or $\delta_z$, and this was the first time you encountered a +$y$ or $z$ subscript, respectively. Then assign $y$ or $z$ to the new +$\delta$; you have scored a hit. (b)~You see $\delta_d$, and no $y$ +subscripts have been encountered so far during this search. Then change +the previous $\delta_d$ to $\delta_y$ (this corresponds to changing a +command in the output buffer), and assign $y$ to the new $\delta$; it's +another hit. (c)~You see $\delta_d$, and a $y$ subscript has been seen +but not a $z$. Change the previous $\delta_d$ to $\delta_z$ and assign +$z$ to the new $\delta$. (d)~You encounter both $y$ and $z$ subscripts +before encountering a suitable $\delta$, or you scan all the way to the +front of the sequence. Assign $d$ to the new $\delta$; this assignment may +be changed later. + +The subscripts $3_z\,1_y\,4_d\ldots\,$ in the example above were, in fact, +produced by this procedure, as the reader can verify. (Go ahead and try it.) + +@ In order to implement such an idea, \TeX\ maintains a stack of pointers +to the \\{down}, $y$, and $z$ commands that have been generated for the +current page. And there is a similar stack for \\{right}, |w|, and |x| +commands. These stacks are called the down stack and right stack, and their +top elements are maintained in the variables |down_ptr| and |right_ptr|. + +Each entry in these stacks contains four fields: The |width| field is +the amount of motion down or to the right; the |location| field is the +byte number of the \.{DVI} command in question (including the appropriate +|dvi_offset|); the |link| field points to the next item below this one +on the stack; and the |info| field encodes the options for possible change +in the \.{DVI} command. + +@d movement_node_size 3 /*number of words per entry in the down and right stacks*/ +@d location(A) mem[A+2].i /*\.{DVI} byte number for a movement command*/ + +@<Glob...@>= +static pointer @!down_ptr, @!right_ptr; /*heads of the down and right stacks*/ + +@ @<Set init...@>= +down_ptr=null;right_ptr=null; + +@ Here is a subroutine that produces a \.{DVI} command for some specified +downward or rightward motion. It has two parameters: |w| is the amount +of motion, and |o| is either |down1| or |right1|. We use the fact that +the command codes have convenient arithmetic properties: |y1-down1==w1-right1| +and |z1-down1==x1-right1|. + +@p static void movement(scaled @!w, eight_bits @!o) +{@+ +small_number mstate; /*have we seen a |y| or |z|?*/ +pointer @!p, @!q; /*current and top nodes on the stack*/ +int @!k; /*index into |dvi_buf|, modulo |dvi_buf_size|*/ +q=get_node(movement_node_size); /*new node for the top of the stack*/ +width(q)=w;location(q)=dvi_offset+dvi_ptr; +if (o==down1) + {@+link(q)=down_ptr;down_ptr=q; + } +else{@+link(q)=right_ptr;right_ptr=q; + } +@<Look at the other stack entries until deciding what sort of \.{DVI} command +to generate; |goto found| if node |p| is a ``hit''@>; +@<Generate a |down| or |right| command for |w| and |return|@>; +found: @<Generate a |y0| or |z0| command in order to reuse a previous appearance +of~|w|@>; +} + +@ The |info| fields in the entries of the down stack or the right stack +have six possible settings: |y_here| or |z_here| mean that the \.{DVI} +command refers to |y| or |z|, respectively (or to |w| or |x|, in the +case of horizontal motion); |yz_OK| means that the \.{DVI} command is +\\{down} (or \\{right}) but can be changed to either |y| or |z| (or +to either |w| or |x|); |y_OK| means that it is \\{down} and can be changed +to |y| but not |z|; |z_OK| is similar; and |d_fixed| means it must stay +\\{down}. + +The four settings |yz_OK|, |y_OK|, |z_OK|, |d_fixed| would not need to +be distinguished from each other if we were simply solving the +digit-subscripting problem mentioned above. But in \TeX's case there is +a complication because of the nested structure of |push| and |pop| +commands. Suppose we add parentheses to the digit-subscripting problem, +redefining hits so that $\delta_y\ldots \delta_y$ is a hit if all $y$'s between +the $\delta$'s are enclosed in properly nested parentheses, and if the +parenthesis level of the right-hand $\delta_y$ is deeper than or equal to +that of the left-hand one. Thus, `(' and `)' correspond to `|push|' +and `|pop|'. Now if we want to assign a subscript to the final 1 in the +sequence +$$2_y\,7_d\,1_d\,(\,8_z\,2_y\,8_z\,)\,1$$ +we cannot change the previous $1_d$ to $1_y$, since that would invalidate +the $2_y\ldots2_y$ hit. But we can change it to $1_z$, scoring a hit +since the intervening $8_z$'s are enclosed in parentheses. + +The program below removes movement nodes that are introduced after a |push|, +before it outputs the corresponding |pop|. + +@d y_here 1 /*|info| when the movement entry points to a |y| command*/ +@d z_here 2 /*|info| when the movement entry points to a |z| command*/ +@d yz_OK 3 /*|info| corresponding to an unconstrained \\{down} command*/ +@d y_OK 4 /*|info| corresponding to a \\{down} that can't become a |z|*/ +@d z_OK 5 /*|info| corresponding to a \\{down} that can't become a |y|*/ +@d d_fixed 6 /*|info| corresponding to a \\{down} that can't change*/ + +@ When the |movement| procedure gets to the label |found|, the value of +|info(p)| will be either |y_here| or |z_here|. If it is, say, |y_here|, +the procedure generates a |y0| command (or a |w0| command), and marks +all |info| fields between |q| and |p| so that |y| is not OK in that range. + +@<Generate a |y0| or |z0| command...@>= +info(q)=info(p); +if (info(q)==y_here) + {@+dvi_out(o+y0-down1); /*|y0| or |w0|*/ + while (link(q)!=p) + {@+q=link(q); + switch (info(q)) { + case yz_OK: info(q)=z_OK;@+break; + case y_OK: info(q)=d_fixed;@+break; + default:do_nothing; + } + } + } +else{@+dvi_out(o+z0-down1); /*|z0| or |x0|*/ + while (link(q)!=p) + {@+q=link(q); + switch (info(q)) { + case yz_OK: info(q)=y_OK;@+break; + case z_OK: info(q)=d_fixed;@+break; + default:do_nothing; + } + } + } + +@ @<Generate a |down| or |right|...@>= +info(q)=yz_OK; +if (abs(w) >= 040000000) + {@+dvi_out(o+3); /*|down4| or |right4|*/ + dvi_four(w);return; + } +if (abs(w) >= 0100000) + {@+dvi_out(o+2); /*|down3| or |right3|*/ + if (w < 0) w=w+0100000000; + dvi_out(w/0200000);w=w%0200000;goto label2; + } +if (abs(w) >= 0200) + {@+dvi_out(o+1); /*|down2| or |right2|*/ + if (w < 0) w=w+0200000; + goto label2; + } +dvi_out(o); /*|down1| or |right1|*/ +if (w < 0) w=w+0400; +goto label1; +label2: dvi_out(w/0400); +label1: dvi_out(w%0400);return + +@ As we search through the stack, we are in one of three states, +|y_seen|, |z_seen|, or |none_seen|, depending on whether we have +encountered |y_here| or |z_here| nodes. These states are encoded as +multiples of 6, so that they can be added to the |info| fields for quick +decision-making. +@^inner loop@> + +@d none_seen 0 /*no |y_here| or |z_here| nodes have been encountered yet*/ +@d y_seen 6 /*we have seen |y_here| but not |z_here|*/ +@d z_seen 12 /*we have seen |z_here| but not |y_here|*/ + +@<Look at the other stack entries until deciding...@>= +p=link(q);mstate=none_seen; +while (p!=null) + {@+if (width(p)==w) @<Consider a node with matching width; |goto found| +if it's a hit@>@; + else switch (mstate+info(p)) { + case none_seen+y_here: mstate=y_seen;@+break; + case none_seen+z_here: mstate=z_seen;@+break; + case y_seen+z_here: case z_seen+y_here: goto not_found; + default:do_nothing; + } + p=link(p); + } +not_found: + +@ We might find a valid hit in a |y| or |z| byte that is already gone +from the buffer. But we can't change bytes that are gone forever; ``the +moving finger writes, $\ldots\,\,$.'' + +@<Consider a node with matching width...@>= +switch (mstate+info(p)) { +case none_seen+yz_OK: case none_seen+y_OK: + case z_seen+yz_OK: case z_seen+y_OK: @t@>@;@/ + if (location(p) < dvi_gone) goto not_found; + else@<Change buffered instruction to |y| or |w| and |goto found|@>@;@+break; +case none_seen+z_OK: case y_seen+yz_OK: + case y_seen+z_OK: @t@>@;@/ + if (location(p) < dvi_gone) goto not_found; + else@<Change buffered instruction to |z| or |x| and |goto found|@>@;@+break; +case none_seen+y_here: case none_seen+z_here: + case y_seen+z_here: case z_seen+y_here: goto found; +default:do_nothing; +} + +@ @<Change buffered instruction to |y| or |w| and |goto found|@>= +{@+k=location(p)-dvi_offset; +if (k < 0) k=k+dvi_buf_size; +dvi_buf[k]=dvi_buf[k]+y1-down1; +info(p)=y_here;goto found; +} + +@ @<Change buffered instruction to |z| or |x| and |goto found|@>= +{@+k=location(p)-dvi_offset; +if (k < 0) k=k+dvi_buf_size; +dvi_buf[k]=dvi_buf[k]+z1-down1; +info(p)=z_here;goto found; +} + +@ In case you are wondering when all the movement nodes are removed from +\TeX's memory, the answer is that they are recycled just before +|hlist_out| and |vlist_out| finish outputting a box. This restores the +down and right stacks to the state they were in before the box was output, +except that some |info|'s may have become more restrictive. + +@p static void prune_movements(int @!l) + /*delete movement nodes with |location >= l|*/ +{@+ +pointer p; /*node being deleted*/ +while (down_ptr!=null) + {@+if (location(down_ptr) < l) goto done; + p=down_ptr;down_ptr=link(p);free_node(p, movement_node_size); + } +done: while (right_ptr!=null) + {@+if (location(right_ptr) < l) return; + p=right_ptr;right_ptr=link(p);free_node(p, movement_node_size); + } +} + +@ The actual distances by which we want to move might be computed as the +sum of several separate movements. For example, there might be several +glue nodes in succession, or we might want to move right by the width of +some box plus some amount of glue. More importantly, the baselineskip +distances are computed in terms of glue together with the depth and +height of adjacent boxes, and we want the \.{DVI} file to lump these +three quantities together into a single motion. + +Therefore, \TeX\ maintains two pairs of global variables: |dvi_h| and |dvi_v| +are the |h| and |v| coordinates corresponding to the commands actually +output to the \.{DVI} file, while |cur_h| and |cur_v| are the coordinates +corresponding to the current state of the output routines. Coordinate +changes will accumulate in |cur_h| and |cur_v| without being reflected +in the output, until such a change becomes necessary or desirable; we +can call the |movement| procedure whenever we want to make |dvi_h==cur_h| +or |dvi_v==cur_v|. + +The current font reflected in the \.{DVI} output is called |dvi_f|; +there is no need for a `\\{cur\_f}' variable. + +The depth of nesting of |hlist_out| and |vlist_out| is called |cur_s|; +this is essentially the depth of |push| commands in the \.{DVI} output. + +@d synch_h if (cur_h!=dvi_h) + {@+movement(cur_h-dvi_h, right1);dvi_h=cur_h; + } +@d synch_v if (cur_v!=dvi_v) + {@+movement(cur_v-dvi_v, down1);dvi_v=cur_v; + } + +@<Glob...@>= +static scaled @!dvi_h, @!dvi_v; /*a \.{DVI} reader program thinks we are here*/ +static scaled @!cur_h, @!cur_v; /*\TeX\ thinks we are here*/ +static internal_font_number @!dvi_f; /*the current font*/ +static int @!cur_s; /*current depth of output box nesting, initially $-1$*/ + +@ @<Initialize variables as |ship_out| begins@>= +dvi_h=0;dvi_v=0;cur_h=h_offset;dvi_f=null_font; +ensure_dvi_open; +if (total_pages==0) + {@+dvi_out(pre);dvi_out(id_byte); /*output the preamble*/ +@^preamble of \.{DVI} file@> + dvi_four(25400000);dvi_four(473628672); /*conversion ratio for sp*/ + prepare_mag();dvi_four(mag); /*magnification factor is frozen*/ + old_setting=selector;selector=new_string; + print(" TeX output ");print_int(year);print_char('.'); + print_two(month);print_char('.');print_two(day); + print_char(':');print_two(time/60); + print_two(time%60); + selector=old_setting;dvi_out(cur_length); + for (s=str_start[str_ptr]; s<=pool_ptr-1; s++) dvi_out(so(str_pool[s])); + pool_ptr=str_start[str_ptr]; /*flush the current string*/ + } + +@ When |hlist_out| is called, its duty is to output the box represented +by the |hlist_node| pointed to by |temp_ptr|. The reference point of that +box has coordinates |(cur_h, cur_v)|. + +Similarly, when |vlist_out| is called, its duty is to output the box represented +by the |vlist_node| pointed to by |temp_ptr|. The reference point of that +box has coordinates |(cur_h, cur_v)|. +@^recursion@> + +@p static void vlist_out(void); /*|hlist_out| and |vlist_out| are mutually + recursive*/ + +@ The recursive procedures |hlist_out| and |vlist_out| each have local variables +|save_h| and |save_v| to hold the values of |dvi_h| and |dvi_v| just before +entering a new level of recursion. In effect, the values of |save_h| and +|save_v| on \TeX's run-time stack correspond to the values of |h| and |v| +that a \.{DVI}-reading program will push onto its coordinate stack. + +@p @t\4@>@<Declare procedures needed in |hlist_out|, |vlist_out|@>@t@>@/ +static void hlist_out(void) /*output an |hlist_node| box*/ +{@+ +scaled base_line; /*the baseline coordinate for this box*/ +scaled @!left_edge; /*the left coordinate for this box*/ +scaled @!save_h, @!save_v; /*what |dvi_h| and |dvi_v| should pop to*/ +pointer @!this_box; /*pointer to containing box*/ +glue_ord @!g_order; /*applicable order of infinity for glue*/ +int @!g_sign; /*selects type of glue*/ +pointer @!p; /*current position in the hlist*/ +int @!save_loc; /*\.{DVI} byte location upon entry*/ +pointer @!leader_box; /*the leader box being replicated*/ +scaled @!leader_wd; /*width of leader box being replicated*/ +scaled @!lx; /*extra space between leader boxes*/ +bool @!outer_doing_leaders; /*were we doing leaders?*/ +scaled @!edge; /*left edge of sub-box, or right edge of leader space*/ +double @!glue_temp; /*glue value before rounding*/ +double @!cur_glue; /*glue seen so far*/ +scaled @!cur_g; /*rounded equivalent of |cur_glue| times the glue ratio*/ +cur_g=0;cur_glue=float_constant(0); +this_box=temp_ptr;g_order=glue_order(this_box); +g_sign=glue_sign(this_box);p=list_ptr(this_box); +incr(cur_s); +if (cur_s > 0) dvi_out(push); +if (cur_s > max_push) max_push=cur_s; +save_loc=dvi_offset+dvi_ptr;base_line=cur_v;left_edge=cur_h; +while (p!=null) @<Output node |p| for |hlist_out| and move to the next node, +maintaining the condition |cur_v=base_line|@>; +prune_movements(save_loc); +if (cur_s > 0) dvi_pop(save_loc); +decr(cur_s); +} + +@ We ought to give special care to the efficiency of one part of |hlist_out|, +since it belongs to \TeX's inner loop. When a |char_node| is encountered, +we save a little time by processing several nodes in succession until +reaching a non-|char_node|. The program uses the fact that |set_char_0==0|. +@^inner loop@> + +@<Output node |p| for |hlist_out|...@>= +reswitch: if (is_char_node(p)) + {@+synch_h;synch_v; + @/do@+{f=font(p);c=character(p); + if (f!=dvi_f) @<Change font |dvi_f| to |f|@>; + if (c >= qi(128)) dvi_out(set1); + dvi_out(qo(c));@/ + cur_h=cur_h+char_width(f, char_info(f, c)); + p=link(p); + }@+ while (!(!is_char_node(p))); + dvi_h=cur_h; + } +else@<Output the non-|char_node| |p| for |hlist_out| and move to the next +node@>@; + +@ @<Change font |dvi_f| to |f|@>= +{@+if (!font_used[f]) + {@+dvi_font_def(f);font_used[f]=true; + } +if (f <= 64+font_base) dvi_out(f-font_base-1+fnt_num_0)@; +else{@+dvi_out(fnt1);dvi_out(f-font_base-1); + } +dvi_f=f; +} + +@ @<Output the non-|char_node| |p| for |hlist_out|...@>= +{@+switch (type(p)) { +case hlist_node: case vlist_node: @<Output a box in an hlist@>@;@+break; +case rule_node: {@+rule_ht=height(p);rule_dp=depth(p);rule_wd=width(p); + goto fin_rule; + } +case whatsit_node: @<Output the whatsit node |p| in an hlist@>;@+break; +case glue_node: @<Move right or output leaders@>@; +case kern_node: case math_node: cur_h=cur_h+width(p);@+break; +case ligature_node: @<Make node |p| look like a |char_node| and |goto reswitch|@>@; +default:do_nothing; +} @/ +goto next_p; +fin_rule: @<Output a rule in an hlist@>; +move_past: cur_h=cur_h+rule_wd; +next_p: p=link(p); +} + +@ @<Output a box in an hlist@>= +if (list_ptr(p)==null) cur_h=cur_h+width(p); +else{@+save_h=dvi_h;save_v=dvi_v; + cur_v=base_line+shift_amount(p); /*shift the box down*/ + temp_ptr=p;edge=cur_h; + if (type(p)==vlist_node) vlist_out();@+else hlist_out(); + dvi_h=save_h;dvi_v=save_v; + cur_h=edge+width(p);cur_v=base_line; + } + +@ @<Output a rule in an hlist@>= +if (is_running(rule_ht)) rule_ht=height(this_box); +if (is_running(rule_dp)) rule_dp=depth(this_box); +rule_ht=rule_ht+rule_dp; /*this is the rule thickness*/ +if ((rule_ht > 0)&&(rule_wd > 0)) /*we don't output empty rules*/ + {@+synch_h;cur_v=base_line+rule_dp;synch_v; + dvi_out(set_rule);dvi_four(rule_ht);dvi_four(rule_wd); + cur_v=base_line;dvi_h=dvi_h+rule_wd; + } + +@ @d billion float_constant(1000000000) +@d vet_glue(A) glue_temp=A; + if (glue_temp > billion) + glue_temp=billion; + else if (glue_temp < -billion) + glue_temp=-billion + +@<Move right or output leaders@>= +{@+g=glue_ptr(p);rule_wd=width(g)-cur_g; +if (g_sign!=normal) + {@+if (g_sign==stretching) + {@+if (stretch_order(g)==g_order) + {@+cur_glue=cur_glue+stretch(g); + vet_glue(unfix(glue_set(this_box))*cur_glue); +@^real multiplication@> + cur_g=round(glue_temp); + } + } + else if (shrink_order(g)==g_order) + {@+cur_glue=cur_glue-shrink(g); + vet_glue(unfix(glue_set(this_box))*cur_glue); + cur_g=round(glue_temp); + } + } +rule_wd=rule_wd+cur_g; +if (subtype(p) >= a_leaders) + @<Output leaders in an hlist, |goto fin_rule| if a rule or to |next_p| if +done@>; +goto move_past; +} + +@ @<Output leaders in an hlist...@>= +{@+leader_box=leader_ptr(p); +if (type(leader_box)==rule_node) + {@+rule_ht=height(leader_box);rule_dp=depth(leader_box); + goto fin_rule; + } +leader_wd=width(leader_box); +if ((leader_wd > 0)&&(rule_wd > 0)) + {@+rule_wd=rule_wd+10; /*compensate for floating-point rounding*/ + edge=cur_h+rule_wd;lx=0; + @<Let |cur_h| be the position of the first box, and set |leader_wd+lx| to +the spacing between corresponding parts of boxes@>; + while (cur_h+leader_wd <= edge) + @<Output a leader box at |cur_h|, then advance |cur_h| by |leader_wd+lx|@>; + cur_h=edge-10;goto next_p; + } +} + +@ The calculations related to leaders require a bit of care. First, in the +case of |a_leaders| (aligned leaders), we want to move |cur_h| to +|left_edge| plus the smallest multiple of |leader_wd| for which the result +is not less than the current value of |cur_h|; i.e., |cur_h| should become +$|left_edge|+|leader_wd|\times\lceil +(|cur_h|-|left_edge|)/|leader_wd|\rceil$. The program here should work in +all cases even though some implementations of \PASCAL\ give nonstandard +results for the |/| operation when |cur_h| is less than |left_edge|. + +In the case of |c_leaders| (centered leaders), we want to increase |cur_h| +by half of the excess space not occupied by the leaders; and in the +case of |x_leaders| (expanded leaders) we increase |cur_h| +by $1/(q+1)$ of this excess space, where $q$ is the number of times the +leader box will be replicated. Slight inaccuracies in the division might +accumulate; half of this rounding error is placed at each end of the leaders. + +@<Let |cur_h| be the position of the first box,...@>= +if (subtype(p)==a_leaders) + {@+save_h=cur_h; + cur_h=left_edge+leader_wd*((cur_h-left_edge)/leader_wd); + if (cur_h < save_h) cur_h=cur_h+leader_wd; + } +else{@+lq=rule_wd/leader_wd; /*the number of box copies*/ + lr=rule_wd%leader_wd; /*the remaining space*/ + if (subtype(p)==c_leaders) cur_h=cur_h+(lr/2); + else{@+lx=lr/(lq+1); + cur_h=cur_h+((lr-(lq-1)*lx)/2); + } + } + +@ The `\\{synch}' operations here are intended to decrease the number of +bytes needed to specify horizontal and vertical motion in the \.{DVI} output. + +@<Output a leader box at |cur_h|,...@>= +{@+cur_v=base_line+shift_amount(leader_box);synch_v;save_v=dvi_v;@/ +synch_h;save_h=dvi_h;temp_ptr=leader_box; +outer_doing_leaders=doing_leaders;doing_leaders=true; +if (type(leader_box)==vlist_node) vlist_out();@+else hlist_out(); +doing_leaders=outer_doing_leaders; +dvi_v=save_v;dvi_h=save_h;cur_v=base_line; +cur_h=save_h+leader_wd+lx; +} + +@ The |vlist_out| routine is similar to |hlist_out|, but a bit simpler. + +@p static void vlist_out(void) /*output a |vlist_node| box*/ +{@+ +scaled left_edge; /*the left coordinate for this box*/ +scaled @!top_edge; /*the top coordinate for this box*/ +scaled @!save_h, @!save_v; /*what |dvi_h| and |dvi_v| should pop to*/ +pointer @!this_box; /*pointer to containing box*/ +glue_ord @!g_order; /*applicable order of infinity for glue*/ +int @!g_sign; /*selects type of glue*/ +pointer @!p; /*current position in the vlist*/ +int @!save_loc; /*\.{DVI} byte location upon entry*/ +pointer @!leader_box; /*the leader box being replicated*/ +scaled @!leader_ht; /*height of leader box being replicated*/ +scaled @!lx; /*extra space between leader boxes*/ +bool @!outer_doing_leaders; /*were we doing leaders?*/ +scaled @!edge; /*bottom boundary of leader space*/ +double @!glue_temp; /*glue value before rounding*/ +double @!cur_glue; /*glue seen so far*/ +scaled @!cur_g; /*rounded equivalent of |cur_glue| times the glue ratio*/ +cur_g=0;cur_glue=float_constant(0); +this_box=temp_ptr;g_order=glue_order(this_box); +g_sign=glue_sign(this_box);p=list_ptr(this_box); +incr(cur_s); +if (cur_s > 0) dvi_out(push); +if (cur_s > max_push) max_push=cur_s; +save_loc=dvi_offset+dvi_ptr;left_edge=cur_h;cur_v=cur_v-height(this_box); +top_edge=cur_v; +while (p!=null) @<Output node |p| for |vlist_out| and move to the next node, +maintaining the condition |cur_h=left_edge|@>; +prune_movements(save_loc); +if (cur_s > 0) dvi_pop(save_loc); +decr(cur_s); +} + +@ @<Output node |p| for |vlist_out|...@>= +{@+if (is_char_node(p)) confusion("vlistout"); +@:this can't happen vlistout}{\quad vlistout@> +else@<Output the non-|char_node| |p| for |vlist_out|@>; +next_p: p=link(p); +} + +@ @<Output the non-|char_node| |p| for |vlist_out|@>= +{@+switch (type(p)) { +case hlist_node: case vlist_node: @<Output a box in a vlist@>@;@+break; +case rule_node: {@+rule_ht=height(p);rule_dp=depth(p);rule_wd=width(p); + goto fin_rule; + } +case whatsit_node: @<Output the whatsit node |p| in a vlist@>;@+break; +case glue_node: @<Move down or output leaders@>@; +case kern_node: cur_v=cur_v+width(p);@+break; +default:do_nothing; +} @/ +goto next_p; +fin_rule: @<Output a rule in a vlist, |goto next_p|@>; +move_past: cur_v=cur_v+rule_ht; +} + +@ The |synch_v| here allows the \.{DVI} output to use one-byte commands +for adjusting |v| in most cases, since the baselineskip distance will +usually be constant. + +@<Output a box in a vlist@>= +if (list_ptr(p)==null) cur_v=cur_v+height(p)+depth(p); +else{@+cur_v=cur_v+height(p);synch_v; + save_h=dvi_h;save_v=dvi_v; + cur_h=left_edge+shift_amount(p); /*shift the box right*/ + temp_ptr=p; + if (type(p)==vlist_node) vlist_out();@+else hlist_out(); + dvi_h=save_h;dvi_v=save_v; + cur_v=save_v+depth(p);cur_h=left_edge; + } + +@ @<Output a rule in a vlist...@>= +if (is_running(rule_wd)) rule_wd=width(this_box); +rule_ht=rule_ht+rule_dp; /*this is the rule thickness*/ +cur_v=cur_v+rule_ht; +if ((rule_ht > 0)&&(rule_wd > 0)) /*we don't output empty rules*/ + {@+synch_h;synch_v; + dvi_out(put_rule);dvi_four(rule_ht);dvi_four(rule_wd); + } +goto next_p + +@ @<Move down or output leaders@>= +{@+g=glue_ptr(p);rule_ht=width(g)-cur_g; +if (g_sign!=normal) + {@+if (g_sign==stretching) + {@+if (stretch_order(g)==g_order) + {@+cur_glue=cur_glue+stretch(g); + vet_glue(unfix(glue_set(this_box))*cur_glue); +@^real multiplication@> + cur_g=round(glue_temp); + } + } + else if (shrink_order(g)==g_order) + {@+cur_glue=cur_glue-shrink(g); + vet_glue(unfix(glue_set(this_box))*cur_glue); + cur_g=round(glue_temp); + } + } +rule_ht=rule_ht+cur_g; +if (subtype(p) >= a_leaders) + @<Output leaders in a vlist, |goto fin_rule| if a rule or to |next_p| if +done@>; +goto move_past; +} + +@ @<Output leaders in a vlist...@>= +{@+leader_box=leader_ptr(p); +if (type(leader_box)==rule_node) + {@+rule_wd=width(leader_box);rule_dp=0; + goto fin_rule; + } +leader_ht=height(leader_box)+depth(leader_box); +if ((leader_ht > 0)&&(rule_ht > 0)) + {@+rule_ht=rule_ht+10; /*compensate for floating-point rounding*/ + edge=cur_v+rule_ht;lx=0; + @<Let |cur_v| be the position of the first box, and set |leader_ht+lx| to +the spacing between corresponding parts of boxes@>; + while (cur_v+leader_ht <= edge) + @<Output a leader box at |cur_v|, then advance |cur_v| by |leader_ht+lx|@>; + cur_v=edge-10;goto next_p; + } +} + +@ @<Let |cur_v| be the position of the first box,...@>= +if (subtype(p)==a_leaders) + {@+save_v=cur_v; + cur_v=top_edge+leader_ht*((cur_v-top_edge)/leader_ht); + if (cur_v < save_v) cur_v=cur_v+leader_ht; + } +else{@+lq=rule_ht/leader_ht; /*the number of box copies*/ + lr=rule_ht%leader_ht; /*the remaining space*/ + if (subtype(p)==c_leaders) cur_v=cur_v+(lr/2); + else{@+lx=lr/(lq+1); + cur_v=cur_v+((lr-(lq-1)*lx)/2); + } + } + +@ When we reach this part of the program, |cur_v| indicates the top of a +leader box, not its baseline. + +@<Output a leader box at |cur_v|,...@>= +{@+cur_h=left_edge+shift_amount(leader_box);synch_h;save_h=dvi_h;@/ +cur_v=cur_v+height(leader_box);synch_v;save_v=dvi_v; +temp_ptr=leader_box; +outer_doing_leaders=doing_leaders;doing_leaders=true; +if (type(leader_box)==vlist_node) vlist_out();@+else hlist_out(); +doing_leaders=outer_doing_leaders; +dvi_v=save_v;dvi_h=save_h;cur_h=left_edge; +cur_v=save_v-height(leader_box)+leader_ht+lx; +} + +@ The |hlist_out| and |vlist_out| procedures are now complete, so we are +ready for the |ship_out| routine that gets them started in the first place. + +@p static void ship_out(pointer @!p) /*output the box |p|*/ +{@+ +int page_loc; /*location of the current |bop|*/ +int @!j, @!k; /*indices to first ten count registers*/ +int @!s; /*index into |str_pool|*/ +int @!old_setting; /*saved |selector| setting*/ +@<Local variables to save the profiling context@>@; +@<Charge the time used here on |ship_out|@>@; +if (tracing_output > 0) + {@+print_nl("");print_ln(); + print("Completed box being shipped out"); +@.Completed box...@> + } +if (term_offset > max_print_line-9) print_ln(); +else if ((term_offset > 0)||(file_offset > 0)) print_char(' '); +print_char('[');j=9; +while ((count(j)==0)&&(j > 0)) decr(j); +for (k=0; k<=j; k++) + {@+print_int(count(k)); + if (k < j) print_char('.'); + } +update_terminal; +if (tracing_output > 0) + {@+print_char(']'); + begin_diagnostic();show_box(p);end_diagnostic(true); + } +@<Ship box |p| out@>; +if (tracing_output <= 0) print_char(']'); +dead_cycles=0; +update_terminal; /*progress report*/ +@<Flush the box from memory, showing statistics if requested@>; +@<restore the previous current file, line, and command@>@; +} + +@ @<Flush the box from memory, showing statistics if requested@>= +#ifdef @!STAT +if (tracing_stats > 1) + {@+print_nl("Memory usage before: "); +@.Memory usage...@> + print_int(var_used);print_char('&'); + print_int(dyn_used);print_char(';'); + } +#endif +flush_node_list(p); +#ifdef @!STAT +if (tracing_stats > 1) + {@+print(" after: "); + print_int(var_used);print_char('&'); + print_int(dyn_used);print("; still untouched: "); + print_int(hi_mem_min-lo_mem_max-1);print_ln(); + } +#endif + +@ @<Ship box |p| out@>= +@<Update the values of |max_h| and |max_v|; but if the page is too large, +|goto done|@>; +@<Initialize variables as |ship_out| begins@>; +page_loc=dvi_offset+dvi_ptr; +dvi_out(bop); +for (k=0; k<=9; k++) dvi_four(count(k)); +dvi_four(last_bop);last_bop=page_loc; +cur_v=height(p)+v_offset;temp_ptr=p; +if (type(p)==vlist_node) vlist_out();@+else hlist_out(); +dvi_out(eop);incr(total_pages);cur_s=-1; +done: + +@ Sometimes the user will generate a huge page because other error messages +are being ignored. Such pages are not output to the \.{dvi} file, since they +may confuse the printing software. + +@<Update the values of |max_h| and |max_v|; but if the page is too large...@>= +if ((height(p) > max_dimen)||@|(depth(p) > max_dimen)||@| + (height(p)+depth(p)+v_offset > max_dimen)||@| + (width(p)+h_offset > max_dimen)) + {@+print_err("Huge page cannot be shipped out"); +@.Huge page...@> + help2("The page just created is more than 18 feet tall or",@/ + "more than 18 feet wide, so I suspect something went wrong."); + error(); + if (tracing_output <= 0) + {@+begin_diagnostic(); + print_nl("The following box has been deleted:"); +@.The following...deleted@> + show_box(p); + end_diagnostic(true); + } + goto done; + } +if (height(p)+depth(p)+v_offset > max_v) max_v=height(p)+depth(p)+v_offset; +if (width(p)+h_offset > max_h) max_h=width(p)+h_offset + +@ At the end of the program, we must finish things off by writing the +post\-amble. If |total_pages==0|, the \.{DVI} file was never opened. +If |total_pages >= 65536|, the \.{DVI} file will lie. And if +|max_push >= 65536|, the user deserves whatever chaos might ensue. + +An integer variable |k| will be declared for use by this routine. + +@<Finish the \.{DVI} file@>= +while (cur_s > -1) + {@+if (cur_s > 0) dvi_out(pop)@; + else{@+dvi_out(eop);incr(total_pages); + } + decr(cur_s); + } +if (total_pages==0) print_nl("No pages of output."); +@.No pages of output@> +else{@+dvi_out(post); /*beginning of the postamble*/ + dvi_four(last_bop);last_bop=dvi_offset+dvi_ptr-5; /*|post| location*/ + dvi_four(25400000);dvi_four(473628672); /*conversion ratio for sp*/ + prepare_mag();dvi_four(mag); /*magnification factor*/ + dvi_four(max_v);dvi_four(max_h);@/ + dvi_out(max_push/256);dvi_out(max_push%256);@/ + dvi_out((total_pages/256)%256);dvi_out(total_pages%256);@/ + @<Output the font definitions for all fonts that were used@>; + dvi_out(post_post);dvi_four(last_bop);dvi_out(id_byte);@/ + k=4+((dvi_buf_size-dvi_ptr)%4); /*the number of 223's*/ + while (k > 0) + {@+dvi_out(223);decr(k); + } + @<Empty the last bytes out of |dvi_buf|@>; + print_nl("Output written on ");slow_print(output_file_name); +@.Output written on x@> + print(" (");print_int(total_pages);print(" page"); + if (total_pages!=1) print_char('s'); + print(", ");print_int(dvi_offset+dvi_ptr);print(" bytes)."); + b_close(&dvi_file); + } + +@ @<Output the font definitions...@>= +while (font_ptr > font_base) + {@+if (font_used[font_ptr]) dvi_font_def(font_ptr); + decr(font_ptr); + } + +@* Packaging. +We're essentially done with the parts of \TeX\ that are concerned with +the input (|get_next|) and the output (|ship_out|). So it's time to +get heavily into the remaining part, which does the real work of typesetting. + +After lists are constructed, \TeX\ wraps them up and puts them into boxes. +Two major subroutines are given the responsibility for this task: |hpack| +applies to horizontal lists (hlists) and |vpack| applies to vertical lists +(vlists). The main duty of |hpack| and |vpack| is to compute the dimensions +of the resulting boxes, and to adjust the glue if one of those dimensions +is pre-specified. The computed sizes normally enclose all of the material +inside the new box; but some items may stick out if negative glue is used, +if the box is overfull, or if a \.{\\vbox} includes other boxes that have +been shifted left. + +The subroutine call |hpack(p, w, m)| returns a pointer to an |hlist_node| +for a box containing the hlist that starts at |p|. Parameter |w| specifies +a width; and parameter |m| is either `|exactly|' or `|additional|'. Thus, +|hpack(p, w, exactly)| produces a box whose width is exactly |w|, while +|hpack(p, w, additional)| yields a box whose width is the natural width plus +|w|. It is convenient to define a macro called `|natural|' to cover the +most common case, so that we can say |hpack(p, natural)| to get a box that +has the natural width of list |p|. + +Similarly, |vpack(p, w, m)| returns a pointer to a |vlist_node| for a +box containing the vlist that starts at |p|. In this case |w| represents +a height instead of a width; the parameter |m| is interpreted as in |hpack|. + +@d exactly 0 /*a box dimension is pre-specified*/ +@d additional 1 /*a box dimension is increased from the natural one*/ +@d natural 0, additional /*shorthand for parameters to |hpack| and |vpack|*/ + +@ The parameters to |hpack| and |vpack| correspond to \TeX's primitives +like `\.{\\hbox} \.{to} \.{300pt}', `\.{\\hbox} \.{spread} \.{10pt}'; note +that `\.{\\hbox}' with no dimension following it is equivalent to +`\.{\\hbox} \.{spread} \.{0pt}'. The |scan_spec| subroutine scans such +constructions in the user's input, including the mandatory left brace that +follows them, and it puts the specification onto |save_stack| so that the +desired box can later be obtained by executing the following code: +$$\vbox{\halign{#\hfil\cr +|save_ptr=save_ptr-2;|\cr +|hpack(p, saved(1), saved(0)).|\cr}}$$ +Special care is necessary to ensure that the special |save_stack| codes +are placed just below the new group code, because scanning can change +|save_stack| when \.{\\csname} appears. + +@p static void scan_spec(group_code @!c, bool @!three_codes) + /*scans a box specification and left brace*/ +{@+ +int @!s; /*temporarily saved value*/ +int @!spec_code; +if (three_codes) s=saved(0); +if (scan_keyword("to")) spec_code=exactly; +@.to@> +else if (scan_keyword("spread")) spec_code=additional; +@.spread@> +else{@+spec_code=additional;cur_val=0; + goto found; + } +scan_normal_dimen; +found: if (three_codes) + {@+saved(0)=s;incr(save_ptr); + } +saved(0)=spec_code;saved(1)=cur_val;save_ptr=save_ptr+2; +new_save_level(c);scan_left_brace(); +} + +@ To figure out the glue setting, |hpack| and |vpack| determine how much +stretchability and shrinkability are present, considering all four orders +of infinity. The highest order of infinity that has a nonzero coefficient +is then used as if no other orders were present. + +For example, suppose that the given list contains six glue nodes with +the respective stretchabilities 3pt, 8fill, 5fil, 6pt, $-3$fil, $-8$fill. +Then the total is essentially 2fil; and if a total additional space of 6pt +is to be achieved by stretching, the actual amounts of stretch will be +0pt, 0pt, 15pt, 0pt, $-9$pt, and 0pt, since only `fil' glue will be +considered. (The `fill' glue is therefore not really stretching infinitely +with respect to `fil'; nobody would actually want that to happen.) + +The arrays |total_stretch| and |total_shrink| are used to determine how much +glue of each kind is present. A global variable |last_badness| is used +to implement \.{\\badness}. + +@<Glob...@>= +static scaled @!total_stretch0[filll-normal+1], + *const @!total_stretch = @!total_stretch0-normal, + @!total_shrink0[filll-normal+1], *const @!total_shrink = @!total_shrink0-normal; + /*glue found by |hpack| or |vpack|*/ +static int @!last_badness; /*badness of the most recently packaged box*/ + +@ If the global variable |adjust_tail| is non-null, the |hpack| routine +also removes all occurrences of |ins_node|, |mark_node|, and |adjust_node| +items and appends the resulting material onto the list that ends at +location |adjust_tail|. + +@<Glob...@>= +static pointer @!adjust_tail; /*tail of adjustment list*/ + +@ @<Set init...@>=adjust_tail=null;last_badness=0; + +@ Here now is |hpack|, which contains few if any surprises. + +@p static pointer hpack(pointer @!p, scaled @!w, small_number @!m) +{@+ +pointer r; /*the box node that will be returned*/ +pointer @!q; /*trails behind |p|*/ +scaled @!h, @!d, @!x; /*height, depth, and natural width*/ +scaled @!s; /*shift amount*/ +pointer @!g; /*points to a glue specification*/ +glue_ord @!o; /*order of infinity*/ +internal_font_number @!f; /*the font in a |char_node|*/ +four_quarters @!i; /*font information about a |char_node|*/ +eight_bits @!hd; /*height and depth indices for a character*/ +last_badness=0;r=get_node(box_node_size);type(r)=hlist_node; +subtype(r)=min_quarterword;shift_amount(r)=0; +q=r+list_offset;link(q)=p;@/ +h=0;@<Clear dimensions to zero@>; +while (p!=null) @<Examine node |p| in the hlist, taking account of its effect +on the dimensions of the new box, or moving it to the adjustment list; then +advance |p| to the next node@>; +if (adjust_tail!=null) link(adjust_tail)=null; +height(r)=h;depth(r)=d;@/ +@<Determine the value of |width(r)| and the appropriate glue setting; then +|return| or |goto common_ending|@>; +common_ending: @<Finish issuing a diagnostic message for an overfull or underfull +hbox@>; +end: return r; +} + +@ @<Clear dimensions to zero@>= +d=0;x=0; +total_stretch[normal]=0;total_shrink[normal]=0; +total_stretch[fil]=0;total_shrink[fil]=0; +total_stretch[fill]=0;total_shrink[fill]=0; +total_stretch[filll]=0;total_shrink[filll]=0 + +@ @<Examine node |p| in the hlist, taking account of its effect...@>= +@^inner loop@> +{@+reswitch: while (is_char_node(p)) + @<Incorporate character dimensions into the dimensions of the hbox that +will contain~it, then move to the next node@>; +if (p!=null) + {@+switch (type(p)) { + case hlist_node: case vlist_node: case rule_node: + case unset_node: + @<Incorporate box dimensions into the dimensions of the hbox that will +contain~it@>@;@+break; + case ins_node: case mark_node: case adjust_node: if (adjust_tail!=null) + @<Transfer node |p| to the adjustment list@>@;@+break; + case whatsit_node: @<Incorporate a whatsit node into an hbox@>;@+break; + case glue_node: @<Incorporate glue into the horizontal totals@>@;@+break; + case kern_node: case math_node: x=x+width(p);@+break; + case ligature_node: @<Make node |p| look like a |char_node| and |goto reswitch|@>@; + default:do_nothing; + } @/ + p=link(p); + } +} + + +@ @<Make node |p| look like a |char_node| and |goto reswitch|@>= +{@+mem[lig_trick]=mem[lig_char(p)];link(lig_trick)=link(p); +p=lig_trick;goto reswitch; +} + +@ The code here implicitly uses the fact that running dimensions are +indicated by |null_flag|, which will be ignored in the calculations +because it is a highly negative number. + +@<Incorporate box dimensions into the dimensions of the hbox...@>= +{@+x=x+width(p); +if (type(p) >= rule_node) s=0;@+else s=shift_amount(p); +if (height(p)-s > h) h=height(p)-s; +if (depth(p)+s > d) d=depth(p)+s; +} + +@ The following code is part of \TeX's inner loop; i.e., adding another +character of text to the user's input will cause each of these instructions +to be exercised one more time. +@^inner loop@> + +@<Incorporate character dimensions into the dimensions of the hbox...@>= +{@+f=font(p);i=char_info(f, character(p));hd=height_depth(i); +x=x+char_width(f, i);@/ +s=char_height(f, hd);@+if (s > h) h=s; +s=char_depth(f, hd);@+if (s > d) d=s; +p=link(p); +} + +@ Although node |q| is not necessarily the immediate predecessor of node |p|, +it always points to some node in the list preceding |p|. Thus, we can delete +nodes by moving |q| when necessary. The algorithm takes linear time, and the +extra computation does not intrude on the inner loop unless it is necessary +to make a deletion. +@^inner loop@> + +@<Transfer node |p| to the adjustment list@>= +{@+while (link(q)!=p) q=link(q); +if (type(p)==adjust_node) + {@+link(adjust_tail)=adjust_ptr(p); + while (link(adjust_tail)!=null) adjust_tail=link(adjust_tail); + p=link(p);free_node(link(q), small_node_size); + } +else{@+link(adjust_tail)=p;adjust_tail=p;p=link(p); + } +link(q)=p;p=q; +} + +@ @<Incorporate glue into the horizontal totals@>= +{@+g=glue_ptr(p);x=x+width(g);@/ +o=stretch_order(g);total_stretch[o]=total_stretch[o]+stretch(g); +o=shrink_order(g);total_shrink[o]=total_shrink[o]+shrink(g); +if (subtype(p) >= a_leaders) + {@+g=leader_ptr(p); + if (height(g) > h) h=height(g); + if (depth(g) > d) d=depth(g); + } +} + +@ When we get to the present part of the program, |x| is the natural width +of the box being packaged. + +@<Determine the value of |width(r)| and the appropriate glue setting...@>= +if (m==additional) w=x+w; +width(r)=w;x=w-x; /*now |x| is the excess to be made up*/ +if (x==0) + {@+glue_sign(r)=normal;glue_order(r)=normal; + set_glue_ratio_zero(glue_set(r)); + goto end; + } +else if (x > 0) @<Determine horizontal glue stretch setting, then |return| +or \hbox{|goto common_ending|}@>@; +else@<Determine horizontal glue shrink setting, then |return| or \hbox{|goto +common_ending|}@>@; + +@ @<Determine horizontal glue stretch setting...@>= +{@+@<Determine the stretch order@>; +glue_order(r)=o;glue_sign(r)=stretching; +if (total_stretch[o]!=0) glue_set(r)=fix(x/(double)total_stretch[o]); +@^real division@> +else{@+glue_sign(r)=normal; + set_glue_ratio_zero(glue_set(r)); /*there's nothing to stretch*/ + } +if (o==normal) if (list_ptr(r)!=null) + @<Report an underfull hbox and |goto common_ending|, if this box is sufficiently +bad@>; +goto end; +} + +@ @<Determine the stretch order@>= +if (total_stretch[filll]!=0) o=filll; +else if (total_stretch[fill]!=0) o=fill; +else if (total_stretch[fil]!=0) o=fil; +else o=normal + +@ @<Report an underfull hbox and |goto common_ending|, if...@>= +{@+last_badness=badness(x, total_stretch[normal]); +if (last_badness > hbadness) + {@+print_ln(); + if (last_badness > 100) print_nl("Underfull");@+else print_nl("Loose"); + print(" \\hbox (badness ");print_int(last_badness); +@.Underfull \\hbox...@> +@.Loose \\hbox...@> + goto common_ending; + } +} + +@ In order to provide a decent indication of where an overfull or underfull +box originated, we use a global variable |pack_begin_line| that is +set nonzero only when |hpack| is being called by the paragraph builder +or the alignment finishing routine. + +@<Glob...@>= +static int @!pack_begin_line; /*source file line where the current paragraph + or alignment began; a negative value denotes alignment*/ + +@ @<Set init...@>= +pack_begin_line=0; + +@ @<Finish issuing a diagnostic message for an overfull or underfull hbox@>= +if (output_active) print(") has occurred while \\output is active"); +else{@+if (pack_begin_line!=0) + {@+if (pack_begin_line > 0) print(") in paragraph at lines "); + else print(") in alignment at lines "); + print_int(abs(pack_begin_line)); + print("--"); + } + else print(") detected at line "); + print_int(line); + } +print_ln();@/ +font_in_short_display=null_font;short_display(list_ptr(r));print_ln();@/ +begin_diagnostic();show_box(r);end_diagnostic(true) + +@ @<Determine horizontal glue shrink setting...@>= +{@+@<Determine the shrink order@>; +glue_order(r)=o;glue_sign(r)=shrinking; +if (total_shrink[o]!=0) glue_set(r)=fix((-x)/(double)total_shrink[o]); +@^real division@> +else{@+glue_sign(r)=normal; + set_glue_ratio_zero(glue_set(r)); /*there's nothing to shrink*/ + } +if ((total_shrink[o] < -x)&&(o==normal)&&(list_ptr(r)!=null)) + {@+last_badness=1000000; + set_glue_ratio_one(glue_set(r)); /*use the maximum shrinkage*/ + @<Report an overfull hbox and |goto common_ending|, if this box is sufficiently +bad@>; + } +else if (o==normal) if (list_ptr(r)!=null) + @<Report a tight hbox and |goto common_ending|, if this box is sufficiently +bad@>; +goto end; +} + +@ @<Determine the shrink order@>= +if (total_shrink[filll]!=0) o=filll; +else if (total_shrink[fill]!=0) o=fill; +else if (total_shrink[fil]!=0) o=fil; +else o=normal + +@ @<Report an overfull hbox and |goto common_ending|, if...@>= +if ((-x-total_shrink[normal] > hfuzz)||(hbadness < 100)) + {@+if ((overfull_rule > 0)&&(-x-total_shrink[normal] > hfuzz)) + {@+while (link(q)!=null) q=link(q); + link(q)=new_rule(); + width(link(q))=overfull_rule; + } + print_ln();print_nl("Overfull \\hbox ("); +@.Overfull \\hbox...@> + print_scaled(-x-total_shrink[normal]);print("pt too wide"); + goto common_ending; + } + +@ @<Report a tight hbox and |goto common_ending|, if...@>= +{@+last_badness=badness(-x, total_shrink[normal]); +if (last_badness > hbadness) + {@+print_ln();print_nl("Tight \\hbox (badness ");print_int(last_badness); +@.Tight \\hbox...@> + goto common_ending; + } +} + +@ The |vpack| subroutine is actually a special case of a slightly more +general routine called |vpackage|, which has four parameters. The fourth +parameter, which is |max_dimen| in the case of |vpack|, specifies the +maximum depth of the page box that is constructed. The depth is first +computed by the normal rules; if it exceeds this limit, the reference +point is simply moved down until the limiting depth is attained. + + +@p +#define vpack(...) @[vpackage(__VA_ARGS__, max_dimen)@] /*special case of unconstrained depth*/ +static pointer vpackage(pointer @!p, scaled @!h, small_number @!m, scaled @!l) +{@+ +pointer r; /*the box node that will be returned*/ +scaled @!w, @!d, @!x; /*width, depth, and natural height*/ +scaled @!s; /*shift amount*/ +pointer @!g; /*points to a glue specification*/ +glue_ord @!o; /*order of infinity*/ +last_badness=0;r=get_node(box_node_size);type(r)=vlist_node; +subtype(r)=min_quarterword;shift_amount(r)=0; +list_ptr(r)=p;@/ +w=0;@<Clear dimensions to zero@>; +while (p!=null) @<Examine node |p| in the vlist, taking account of its effect +on the dimensions of the new box; then advance |p| to the next node@>; +width(r)=w; +if (d > l) + {@+x=x+d-l;depth(r)=l; + } +else depth(r)=d; +@<Determine the value of |height(r)| and the appropriate glue setting; then +|return| or |goto common_ending|@>; +common_ending: @<Finish issuing a diagnostic message for an overfull or underfull +vbox@>; +end: return r; +} + +@ @<Examine node |p| in the vlist, taking account of its effect...@>= +{@+if (is_char_node(p)) confusion("vpack"); +@:this can't happen vpack}{\quad vpack@> +else switch (type(p)) { + case hlist_node: case vlist_node: case rule_node: + case unset_node: + @<Incorporate box dimensions into the dimensions of the vbox that will +contain~it@>@;@+break; + case whatsit_node: @<Incorporate a whatsit node into a vbox@>;@+break; + case glue_node: @<Incorporate glue into the vertical totals@>@;@+break; + case kern_node: {@+x=x+d+width(p);d=0; + } @+break; + default:do_nothing; + } +p=link(p); +} + +@ @<Incorporate box dimensions into the dimensions of the vbox...@>= +{@+x=x+d+height(p);d=depth(p); +if (type(p) >= rule_node) s=0;@+else s=shift_amount(p); +if (width(p)+s > w) w=width(p)+s; +} + +@ @<Incorporate glue into the vertical totals@>= +{@+x=x+d;d=0;@/ +g=glue_ptr(p);x=x+width(g);@/ +o=stretch_order(g);total_stretch[o]=total_stretch[o]+stretch(g); +o=shrink_order(g);total_shrink[o]=total_shrink[o]+shrink(g); +if (subtype(p) >= a_leaders) + {@+g=leader_ptr(p); + if (width(g) > w) w=width(g); + } +} + +@ When we get to the present part of the program, |x| is the natural height +of the box being packaged. + +@<Determine the value of |height(r)| and the appropriate glue setting...@>= +if (m==additional) h=x+h; +height(r)=h;x=h-x; /*now |x| is the excess to be made up*/ +if (x==0) + {@+glue_sign(r)=normal;glue_order(r)=normal; + set_glue_ratio_zero(glue_set(r)); + goto end; + } +else if (x > 0) @<Determine vertical glue stretch setting, then |return| or +\hbox{|goto common_ending|}@>@; +else@<Determine vertical glue shrink setting, then |return| or \hbox{|goto +common_ending|}@>@; + +@ @<Determine vertical glue stretch setting...@>= +{@+@<Determine the stretch order@>; +glue_order(r)=o;glue_sign(r)=stretching; +if (total_stretch[o]!=0) glue_set(r)=fix(x/(double)total_stretch[o]); +@^real division@> +else{@+glue_sign(r)=normal; + set_glue_ratio_zero(glue_set(r)); /*there's nothing to stretch*/ + } +if (o==normal) if (list_ptr(r)!=null) + @<Report an underfull vbox and |goto common_ending|, if this box is sufficiently +bad@>; +goto end; +} + +@ @<Report an underfull vbox and |goto common_ending|, if...@>= +{@+last_badness=badness(x, total_stretch[normal]); +if (last_badness > vbadness) + {@+print_ln(); + if (last_badness > 100) print_nl("Underfull");@+else print_nl("Loose"); + print(" \\vbox (badness ");print_int(last_badness); +@.Underfull \\vbox...@> +@.Loose \\vbox...@> + goto common_ending; + } +} + +@ @<Finish issuing a diagnostic message for an overfull or underfull vbox@>= +if (output_active) print(") has occurred while \\output is active"); +else{@+if (pack_begin_line!=0) /*it's actually negative*/ + {@+print(") in alignment at lines "); + print_int(abs(pack_begin_line)); + print("--"); + } + else print(") detected at line "); + print_int(line); + print_ln();@/ + } +begin_diagnostic();show_box(r);end_diagnostic(true) + +@ @<Determine vertical glue shrink setting...@>= +{@+@<Determine the shrink order@>; +glue_order(r)=o;glue_sign(r)=shrinking; +if (total_shrink[o]!=0) glue_set(r)=fix((-x)/(double)total_shrink[o]); +@^real division@> +else{@+glue_sign(r)=normal; + set_glue_ratio_zero(glue_set(r)); /*there's nothing to shrink*/ + } +if ((total_shrink[o] < -x)&&(o==normal)&&(list_ptr(r)!=null)) + {@+last_badness=1000000; + set_glue_ratio_one(glue_set(r)); /*use the maximum shrinkage*/ + @<Report an overfull vbox and |goto common_ending|, if this box is sufficiently +bad@>; + } +else if (o==normal) if (list_ptr(r)!=null) + @<Report a tight vbox and |goto common_ending|, if this box is sufficiently +bad@>; +goto end; +} + +@ @<Report an overfull vbox and |goto common_ending|, if...@>= +if ((-x-total_shrink[normal] > vfuzz)||(vbadness < 100)) + {@+print_ln();print_nl("Overfull \\vbox ("); +@.Overfull \\vbox...@> + print_scaled(-x-total_shrink[normal]);print("pt too high"); + goto common_ending; + } + +@ @<Report a tight vbox and |goto common_ending|, if...@>= +{@+last_badness=badness(-x, total_shrink[normal]); +if (last_badness > vbadness) + {@+print_ln();print_nl("Tight \\vbox (badness ");print_int(last_badness); +@.Tight \\vbox...@> + goto common_ending; + } +} + +@ When a box is being appended to the current vertical list, the +baselineskip calculation is handled by the |append_to_vlist| routine. + +@p static void append_to_vlist(pointer @!b) +{@+scaled d; /*deficiency of space between baselines*/ +pointer @!p; /*a new glue node*/ +if (prev_depth > ignore_depth) + {@+d=width(baseline_skip)-prev_depth-height(b); + if (d < line_skip_limit) p=new_param_glue(line_skip_code); + else{@+p=new_skip_param(baseline_skip_code); + width(temp_ptr)=d; /*|temp_ptr==glue_ptr(p)|*/ + } + link(tail)=p;tail=p; + } +link(tail)=b;tail=b;prev_depth=depth(b); +} + +@* Data structures for math mode. +When \TeX\ reads a formula that is enclosed between \.\$'s, it constructs an +{\sl mlist}, which is essentially a tree structure representing that +formula. An mlist is a linear sequence of items, but we can regard it as +a tree structure because mlists can appear within mlists. For example, many +of the entries can be subscripted or superscripted, and such ``scripts'' +are mlists in their own right. + +An entire formula is parsed into such a tree before any of the actual +typesetting is done, because the current style of type is usually not +known until the formula has been fully scanned. For example, when the +formula `\.{\$a+b \\over c+d\$}' is being read, there is no way to tell +that `\.{a+b}' will be in script size until `\.{\\over}' has appeared. + +During the scanning process, each element of the mlist being built is +classified as a relation, a binary operator, an open parenthesis, etc., +or as a construct like `\.{\\sqrt}' that must be built up. This classification +appears in the mlist data structure. + +After a formula has been fully scanned, the mlist is converted to an hlist +so that it can be incorporated into the surrounding text. This conversion is +controlled by a recursive procedure that decides all of the appropriate +styles by a ``top-down'' process starting at the outermost level and working +in towards the subformulas. The formula is ultimately pasted together using +combinations of horizontal and vertical boxes, with glue and penalty nodes +inserted as necessary. + +An mlist is represented internally as a linked list consisting chiefly +of ``noads'' (pronounced ``no-adds''), to distinguish them from the somewhat +similar ``nodes'' in hlists and vlists. Certain kinds of ordinary nodes are +allowed to appear in mlists together with the noads; \TeX\ tells the difference +by means of the |type| field, since a noad's |type| is always greater than +that of a node. An mlist does not contain character nodes, hlist nodes, vlist +nodes, math nodes, ligature nodes, +or unset nodes; in particular, each mlist item appears in the +variable-size part of |mem|, so the |type| field is always present. + +@ Each noad is four or more words long. The first word contains the |type| +and |subtype| and |link| fields that are already so familiar to us; the +second, third, and fourth words are called the noad's |nucleus|, |subscr|, +and |supscr| fields. + +Consider, for example, the simple formula `\.{\$x\^2\$}', which would be +parsed into an mlist containing a single element called an |ord_noad|. +The |nucleus| of this noad is a representation of `\.x', the |subscr| is +empty, and the |supscr| is a representation of `\.2'. + +The |nucleus|, |subscr|, and |supscr| fields are further broken into +subfields. If |p| points to a noad, and if |q| is one of its principal +fields (e.g., |q==subscr(p)|), there are several possibilities for the +subfields, depending on the |math_type| of |q|. + +\yskip\hang|math_type(q)==math_char| means that |fam(q)| refers to one of +the sixteen font families, and |character(q)| is the number of a character +within a font of that family, as in a character node. + +\yskip\hang|math_type(q)==math_text_char| is similar, but the character is +unsubscripted and unsuperscripted and it is followed immediately by another +character from the same font. (This |math_type| setting appears only +briefly during the processing; it is used to suppress unwanted italic +corrections.) + +\yskip\hang|math_type(q)==empty| indicates a field with no value (the +corresponding attribute of noad |p| is not present). + +\yskip\hang|math_type(q)==sub_box| means that |info(q)| points to a box +node (either an |hlist_node| or a |vlist_node|) that should be used as the +value of the field. The |shift_amount| in the subsidiary box node is the +amount by which that box will be shifted downward. + +\yskip\hang|math_type(q)==sub_mlist| means that |info(q)| points to +an mlist; the mlist must be converted to an hlist in order to obtain +the value of this field. + +\yskip\noindent In the latter case, we might have |info(q)==null|. This +is not the same as |math_type(q)==empty|; for example, `\.{\$P\_\{\}\$}' +and `\.{\$P\$}' produce different results (the former will not have the +``italic correction'' added to the width of |P|, but the ``script skip'' +will be added). + +The definitions of subfields given here are evidently wasteful of space, +since a halfword is being used for the |math_type| although only three +bits would be needed. However, there are hardly ever many noads present at +once, since they are soon converted to nodes that take up even more space, +so we can afford to represent them in whatever way simplifies the +programming. + +@d noad_size 4 /*number of words in a normal noad*/ +@d nucleus(A) A+1 /*the |nucleus| field of a noad*/ +@d supscr(A) A+2 /*the |supscr| field of a noad*/ +@d subscr(A) A+3 /*the |subscr| field of a noad*/ +@d math_type(A) link(A) /*a |halfword| in |mem|*/ +@d fam font /*a |quarterword| in |mem|*/ +@d math_char 1 /*|math_type| when the attribute is simple*/ +@d sub_box 2 /*|math_type| when the attribute is a box*/ +@d sub_mlist 3 /*|math_type| when the attribute is a formula*/ +@d math_text_char 4 /*|math_type| when italic correction is dubious*/ + +@ Each portion of a formula is classified as Ord, Op, Bin, Rel, Open, +Close, Punct, or Inner, for purposes of spacing and line breaking. An +|ord_noad|, |op_noad|, |bin_noad|, |rel_noad|, |open_noad|, |close_noad|, +|punct_noad|, or |inner_noad| is used to represent portions of the various +types. For example, an `\.=' sign in a formula leads to the creation of a +|rel_noad| whose |nucleus| field is a representation of an equals sign +(usually |fam==0|, |character==075|). A formula preceded by \.{\\mathrel} +also results in a |rel_noad|. When a |rel_noad| is followed by an +|op_noad|, say, and possibly separated by one or more ordinary nodes (not +noads), \TeX\ will insert a penalty node (with the current |rel_penalty|) +just after the formula that corresponds to the |rel_noad|, unless there +already was a penalty immediately following; and a ``thick space'' will be +inserted just before the formula that corresponds to the |op_noad|. + +A noad of type |ord_noad|, |op_noad|, \dots, |inner_noad| usually +has a |subtype==normal|. The only exception is that an |op_noad| might +have |subtype==limits| or |no_limits|, if the normal positioning of +limits has been overridden for this operator. + +@d ord_noad (unset_node+3) /*|type| of a noad classified Ord*/ +@d op_noad (ord_noad+1) /*|type| of a noad classified Op*/ +@d bin_noad (ord_noad+2) /*|type| of a noad classified Bin*/ +@d rel_noad (ord_noad+3) /*|type| of a noad classified Rel*/ +@d open_noad (ord_noad+4) /*|type| of a noad classified Open*/ +@d close_noad (ord_noad+5) /*|type| of a noad classified Close*/ +@d punct_noad (ord_noad+6) /*|type| of a noad classified Punct*/ +@d inner_noad (ord_noad+7) /*|type| of a noad classified Inner*/ +@d limits 1 /*|subtype| of |op_noad| whose scripts are to be above, below*/ +@d no_limits 2 /*|subtype| of |op_noad| whose scripts are to be normal*/ + +@ A |radical_noad| is five words long; the fifth word is the |left_delimiter| +field, which usually represents a square root sign. + +A |fraction_noad| is six words long; it has a |right_delimiter| field +as well as a |left_delimiter|. + +Delimiter fields are of type |four_quarters|, and they have four subfields +called |small_fam|, |small_char|, |large_fam|, |large_char|. These subfields +represent variable-size delimiters by giving the ``small'' and ``large'' +starting characters, as explained in Chapter~17 of {\sl The \TeX book}. +@:TeXbook}{\sl The \TeX book@> + +A |fraction_noad| is actually quite different from all other noads. Not +only does it have six words, it has |thickness|, |denominator|, and +|numerator| fields instead of |nucleus|, |subscr|, and |supscr|. The +|thickness| is a scaled value that tells how thick to make a fraction +rule; however, the special value |default_code| is used to stand for the +|default_rule_thickness| of the current size. The |numerator| and +|denominator| point to mlists that define a fraction; we always have +$$\hbox{|math_type(numerator)==math_type(denominator)==sub_mlist|}.$$ The +|left_delimiter| and |right_delimiter| fields specify delimiters that will +be placed at the left and right of the fraction. In this way, a +|fraction_noad| is able to represent all of \TeX's operators \.{\\over}, +\.{\\atop}, \.{\\above}, \.{\\overwithdelims}, \.{\\atopwithdelims}, and + \.{\\abovewithdelims}. + +@d left_delimiter(A) A+4 /*first delimiter field of a noad*/ +@d right_delimiter(A) A+5 /*second delimiter field of a fraction noad*/ +@d radical_noad (inner_noad+1) /*|type| of a noad for square roots*/ +@d radical_noad_size 5 /*number of |mem| words in a radical noad*/ +@d fraction_noad (radical_noad+1) /*|type| of a noad for generalized fractions*/ +@d fraction_noad_size 6 /*number of |mem| words in a fraction noad*/ +@d small_fam(A) mem[A].qqqq.b0 /*|fam| for ``small'' delimiter*/ +@d small_char(A) mem[A].qqqq.b1 /*|character| for ``small'' delimiter*/ +@d large_fam(A) mem[A].qqqq.b2 /*|fam| for ``large'' delimiter*/ +@d large_char(A) mem[A].qqqq.b3 /*|character| for ``large'' delimiter*/ +@d thickness(A) width(A) /*|thickness| field in a fraction noad*/ +@d default_code 010000000000 /*denotes |default_rule_thickness|*/ +@d numerator(A) supscr(A) /*|numerator| field in a fraction noad*/ +@d denominator(A) subscr(A) /*|denominator| field in a fraction noad*/ + +@ The global variable |empty_field| is set up for initialization of empty +fields in new noads. Similarly, |null_delimiter| is for the initialization +of delimiter fields. + +@<Glob...@>= +static two_halves @!empty_field; +static four_quarters @!null_delimiter; + +@ @<Set init...@>= +empty_field.rh=empty;empty_field.lh=null;@/ +null_delimiter.b0=0;null_delimiter.b1=min_quarterword;@/ +null_delimiter.b2=0;null_delimiter.b3=min_quarterword; + +@ The |new_noad| function creates an |ord_noad| that is completely null. + +@p static pointer new_noad(void) +{@+pointer p; +p=get_node(noad_size); +type(p)=ord_noad;subtype(p)=normal; +mem[nucleus(p)].hh=empty_field; +mem[subscr(p)].hh=empty_field; +mem[supscr(p)].hh=empty_field; +return p; +} + +@ A few more kinds of noads will complete the set: An |under_noad| has its +nucleus underlined; an |over_noad| has it overlined. An |accent_noad| places +an accent over its nucleus; the accent character appears as +|fam(accent_chr(p))| and |character(accent_chr(p))|. A |vcenter_noad| +centers its nucleus vertically with respect to the axis of the formula; +in such noads we always have |math_type(nucleus(p))==sub_box|. + +And finally, we have |left_noad| and |right_noad| types, to implement +\TeX's \.{\\left} and \.{\\right} as well as \eTeX's \.{\\middle}. +The |nucleus| of such noads is +replaced by a |delimiter| field; thus, for example, `\.{\\left(}' produces +a |left_noad| such that |delimiter(p)| holds the family and character +codes for all left parentheses. A |left_noad| never appears in an mlist +except as the first element, and a |right_noad| never appears in an mlist +except as the last element; furthermore, we either have both a |left_noad| +and a |right_noad|, or neither one is present. The |subscr| and |supscr| +fields are always |empty| in a |left_noad| and a |right_noad|. + +@d under_noad (fraction_noad+1) /*|type| of a noad for underlining*/ +@d over_noad (under_noad+1) /*|type| of a noad for overlining*/ +@d accent_noad (over_noad+1) /*|type| of a noad for accented subformulas*/ +@d accent_noad_size 5 /*number of |mem| words in an accent noad*/ +@d accent_chr(A) A+4 /*the |accent_chr| field of an accent noad*/ +@d vcenter_noad (accent_noad+1) /*|type| of a noad for \.{\\vcenter}*/ +@d left_noad (vcenter_noad+1) /*|type| of a noad for \.{\\left}*/ +@d right_noad (left_noad+1) /*|type| of a noad for \.{\\right}*/ +@d delimiter(A) nucleus(A) /*|delimiter| field in left and right noads*/ +@d middle_noad 1 /*|subtype| of right noad representing \.{\\middle}*/ +@d scripts_allowed(A) (type(A) >= ord_noad)&&(type(A) < left_noad) + +@ Math formulas can also contain instructions like \.{\\textstyle} that +override \TeX's normal style rules. A |style_node| is inserted into the +data structure to record such instructions; it is three words long, so it +is considered a node instead of a noad. The |subtype| is either |display_style| +or |text_style| or |script_style| or |script_script_style|. The +second and third words of a |style_node| are not used, but they are +present because a |choice_node| is converted to a |style_node|. + +\TeX\ uses even numbers 0, 2, 4, 6 to encode the basic styles +|display_style|, \dots, |script_script_style|, and adds~1 to get the +``cramped'' versions of these styles. This gives a numerical order that +is backwards from the convention of Appendix~G in {\sl The \TeX book\/}; +i.e., a smaller style has a larger numerical value. +@:TeXbook}{\sl The \TeX book@> + +@d style_node (unset_node+1) /*|type| of a style node*/ +@d style_node_size 3 /*number of words in a style node*/ +@d display_style 0 /*|subtype| for \.{\\displaystyle}*/ +@d text_style 2 /*|subtype| for \.{\\textstyle}*/ +@d script_style 4 /*|subtype| for \.{\\scriptstyle}*/ +@d script_script_style 6 /*|subtype| for \.{\\scriptscriptstyle}*/ +@d cramped 1 /*add this to an uncramped style if you want to cramp it*/ + +@p static pointer new_style(small_number @!s) /*create a style node*/ +{@+pointer p; /*the new node*/ +p=get_node(style_node_size);type(p)=style_node; +subtype(p)=s;width(p)=0;depth(p)=0; /*the |width| and |depth| are not used*/ +return p; +} + +@ Finally, the \.{\\mathchoice} primitive creates a |choice_node|, which +has special subfields |display_mlist|, |text_mlist|, |script_mlist|, +and |script_script_mlist| pointing to the mlists for each style. + +@d choice_node (unset_node+2) /*|type| of a choice node*/ +@d display_mlist(A) info(A+1) /*mlist to be used in display style*/ +@d text_mlist(A) link(A+1) /*mlist to be used in text style*/ +@d script_mlist(A) info(A+2) /*mlist to be used in script style*/ +@d script_script_mlist(A) link(A+2) /*mlist to be used in scriptscript style*/ + +@p static pointer new_choice(void) /*create a choice node*/ +{@+pointer p; /*the new node*/ +p=get_node(style_node_size);type(p)=choice_node; +subtype(p)=0; /*the |subtype| is not used*/ +display_mlist(p)=null;text_mlist(p)=null;script_mlist(p)=null; +script_script_mlist(p)=null; +return p; +} + +@ Let's consider now the previously unwritten part of |show_node_list| +that displays the things that can only be present in mlists; this +program illustrates how to access the data structures just defined. + +In the context of the following program, |p| points to a node or noad that +should be displayed, and the current string contains the ``recursion history'' +that leads to this point. The recursion history consists of a dot for each +outer level in which |p| is subsidiary to some node, or in which |p| is +subsidiary to the |nucleus| field of some noad; the dot is replaced by +`\.\_' or `\.\^' or `\./' or `\.\\' if |p| is descended from the |subscr| +or |supscr| or |denominator| or |numerator| fields of noads. For example, +the current string would be `\.{.\^.\_/}' if |p| points to the |ord_noad| for +|x| in the (ridiculous) formula +`\.{\$\\sqrt\{a\^\{\\mathinner\{b\_\{c\\over x+y\}\}\}\}\$}'. + +@<Cases of |show_node_list| that arise...@>= +case style_node: print_style(subtype(p));@+break; +case choice_node: @<Display choice node |p|@>@;@+break; +case ord_noad: case op_noad: case bin_noad: + case rel_noad: case open_noad: case close_noad: + case punct_noad: case inner_noad: + case radical_noad: case over_noad: case under_noad: + case vcenter_noad: case accent_noad: + case left_noad: case right_noad: @<Display normal noad |p|@>@;@+break; +case fraction_noad: @<Display fraction noad |p|@>@;@+break; + +@ Here are some simple routines used in the display of noads. + +@<Declare procedures needed for displaying the elements of mlists@>= +static void print_fam_and_char(pointer @!p) /*prints family and character*/ +{@+print_esc("fam");print_int(fam(p));print_char(' '); +print_ASCII(qo(character(p))); +} +@# +static void print_delimiter(pointer @!p) /*prints a delimiter as 24-bit hex value*/ +{@+int a; /*accumulator*/ +a=small_fam(p)*256+qo(small_char(p)); +a=a*0x1000+large_fam(p)*256+qo(large_char(p)); +if (a < 0) print_int(a); /*this should never happen*/ +else print_hex(a); +} + +@ The next subroutine will descend to another level of recursion when a +subsidiary mlist needs to be displayed. The parameter |c| indicates what +character is to become part of the recursion history. An empty mlist is +distinguished from a field with |math_type(p)==empty|, because these are +not equivalent (as explained above). +@^recursion@> + +@<Declare procedures needed for displaying...@>= +static void show_info(void); /*|show_node_list(info(temp_ptr))|*/ +static void print_subsidiary_data(pointer @!p, ASCII_code @!c) + /*display a noad field*/ +{@+if (cur_length >= depth_threshold) + {@+if (math_type(p)!=empty) print(" []"); + } +else{@+append_char(c); /*include |c| in the recursion history*/ + temp_ptr=p; /*prepare for |show_info| if recursion is needed*/ + switch (math_type(p)) { + case math_char: {@+print_ln();print_current_string();print_fam_and_char(p); + } @+break; + case sub_box: show_info();@+break; /*recursive call*/ + case sub_mlist: if (info(p)==null) + {@+print_ln();print_current_string();print("{}"); + } + else show_info();@+break; /*recursive call*/ + default:do_nothing; /*|empty|*/ + } @/ + flush_char; /*remove |c| from the recursion history*/ + } +} + +@ The inelegant introduction of |show_info| in the code above seems better +than the alternative of using \PASCAL's strange |forward| declaration for a +procedure with parameters. The \PASCAL\ convention about dropping parameters +from a post-|forward| procedure is, frankly, so intolerable to the author +of \TeX\ that he would rather stoop to communication via a global temporary +variable. (A similar stoopidity occurred with respect to |hlist_out| and +|vlist_out| above, and it will occur with respect to |mlist_to_hlist| below.) +@^Knuth, Donald Ervin@> +@:PASCAL}{\PASCAL@> + +@p static void show_info(void) /*the reader will kindly forgive this*/ +{@+show_node_list(info(temp_ptr)); +} + +@ @<Declare procedures needed for displaying...@>= +static void print_style(int @!c) +{@+switch (c/2) { +case 0: print_esc("displaystyle");@+break; /*|display_style==0|*/ +case 1: print_esc("textstyle");@+break; /*|text_style==2|*/ +case 2: print_esc("scriptstyle");@+break; /*|script_style==4|*/ +case 3: print_esc("scriptscriptstyle");@+break; /*|script_script_style==6|*/ +default:print("Unknown style!"); +} +} + +@ @<Display choice node |p|@>= +{@+print_esc("mathchoice"); +append_char('D');show_node_list(display_mlist(p));flush_char; +append_char('T');show_node_list(text_mlist(p));flush_char; +append_char('S');show_node_list(script_mlist(p));flush_char; +append_char('s');show_node_list(script_script_mlist(p));flush_char; +} + +@ @<Display normal noad |p|@>= +{@+switch (type(p)) { +case ord_noad: print_esc("mathord");@+break; +case op_noad: print_esc("mathop");@+break; +case bin_noad: print_esc("mathbin");@+break; +case rel_noad: print_esc("mathrel");@+break; +case open_noad: print_esc("mathopen");@+break; +case close_noad: print_esc("mathclose");@+break; +case punct_noad: print_esc("mathpunct");@+break; +case inner_noad: print_esc("mathinner");@+break; +case over_noad: print_esc("overline");@+break; +case under_noad: print_esc("underline");@+break; +case vcenter_noad: print_esc("vcenter");@+break; +case radical_noad: {@+print_esc("radical");print_delimiter(left_delimiter(p)); + } @+break; +case accent_noad: {@+print_esc("accent");print_fam_and_char(accent_chr(p)); + } @+break; +case left_noad: {@+print_esc("left");print_delimiter(delimiter(p)); + } @+break; +case right_noad: {@+if (subtype(p)==normal) print_esc("right"); + else print_esc("middle"); + print_delimiter(delimiter(p)); + } +} +if (type(p) < left_noad) + {@+if (subtype(p)!=normal) + if (subtype(p)==limits) print_esc("limits"); + else print_esc("nolimits"); + print_subsidiary_data(nucleus(p),'.'); + } +print_subsidiary_data(supscr(p),'^'); +print_subsidiary_data(subscr(p),'_'); +} + +@ @<Display fraction noad |p|@>= +{@+print_esc("fraction, thickness "); +if (thickness(p)==default_code) print("= default"); +else print_scaled(thickness(p)); +if ((small_fam(left_delimiter(p))!=0)||@+ + (small_char(left_delimiter(p))!=min_quarterword)||@| + (large_fam(left_delimiter(p))!=0)||@| + (large_char(left_delimiter(p))!=min_quarterword)) + {@+print(", left-delimiter ");print_delimiter(left_delimiter(p)); + } +if ((small_fam(right_delimiter(p))!=0)||@| + (small_char(right_delimiter(p))!=min_quarterword)||@| + (large_fam(right_delimiter(p))!=0)||@| + (large_char(right_delimiter(p))!=min_quarterword)) + {@+print(", right-delimiter ");print_delimiter(right_delimiter(p)); + } +print_subsidiary_data(numerator(p),'\\'); +print_subsidiary_data(denominator(p),'/'); +} + +@ That which can be displayed can also be destroyed. + +@<Cases of |flush_node_list| that arise...@>= +case style_node: {@+free_node(p, style_node_size);goto done; + } +case choice_node: {@+flush_node_list(display_mlist(p)); + flush_node_list(text_mlist(p)); + flush_node_list(script_mlist(p)); + flush_node_list(script_script_mlist(p)); + free_node(p, style_node_size);goto done; + } +case ord_noad: case op_noad: case bin_noad: + case rel_noad: case open_noad: case close_noad: + case punct_noad: case inner_noad: + case radical_noad: case over_noad: case under_noad: + case vcenter_noad: case accent_noad: @t@>@;@/ + {@+if (math_type(nucleus(p)) >= sub_box) + flush_node_list(info(nucleus(p))); + if (math_type(supscr(p)) >= sub_box) + flush_node_list(info(supscr(p))); + if (math_type(subscr(p)) >= sub_box) + flush_node_list(info(subscr(p))); + if (type(p)==radical_noad) free_node(p, radical_noad_size); + else if (type(p)==accent_noad) free_node(p, accent_noad_size); + else free_node(p, noad_size); + goto done; + } +case left_noad: case right_noad: {@+free_node(p, noad_size);goto done; + } +case fraction_noad: {@+flush_node_list(info(numerator(p))); + flush_node_list(info(denominator(p))); + free_node(p, fraction_noad_size);goto done; + } + +@* Subroutines for math mode. +In order to convert mlists to hlists, i.e., noads to nodes, we need several +subroutines that are conveniently dealt with now. + +Let us first introduce the macros that make it easy to get at the parameters and +other font information. A size code, which is a multiple of 16, is added to a +family number to get an index into the table of internal font numbers +for each combination of family and size. (Be alert: Size codes get +larger as the type gets smaller.) + +@d text_size 0 /*size code for the largest size in a family*/ +@d script_size 16 /*size code for the medium size in a family*/ +@d script_script_size 32 /*size code for the smallest size in a family*/ + +@<Basic printing procedures@>= +static void print_size(int @!s) +{@+if (s==text_size) print_esc("textfont"); +else if (s==script_size) print_esc("scriptfont"); +else print_esc("scriptscriptfont"); +} + +@ Before an mlist is converted to an hlist, \TeX\ makes sure that +the fonts in family~2 have enough parameters to be math-symbol +fonts, and that the fonts in family~3 have enough parameters to be +math-extension fonts. The math-symbol parameters are referred to by using the +following macros, which take a size code as their parameter; for example, +|num1(cur_size)| gives the value of the |num1| parameter for the current size. +@^parameters for symbols@> +@^font parameters@> + +@d mathsy_end(A) fam_fnt(2+A)]].sc +@d mathsy(A) font_info[A+param_base[mathsy_end +@d math_x_height mathsy(5) /*height of `\.x'*/ +@d math_quad mathsy(6) /*\.{18mu}*/ +@d num1 mathsy(8) /*numerator shift-up in display styles*/ +@d num2 mathsy(9) /*numerator shift-up in non-display, non-\.{\\atop}*/ +@d num3 mathsy(10) /*numerator shift-up in non-display \.{\\atop}*/ +@d denom1 mathsy(11) /*denominator shift-down in display styles*/ +@d denom2 mathsy(12) /*denominator shift-down in non-display styles*/ +@d sup1 mathsy(13) /*superscript shift-up in uncramped display style*/ +@d sup2 mathsy(14) /*superscript shift-up in uncramped non-display*/ +@d sup3 mathsy(15) /*superscript shift-up in cramped styles*/ +@d sub1 mathsy(16) /*subscript shift-down if superscript is absent*/ +@d sub2 mathsy(17) /*subscript shift-down if superscript is present*/ +@d sup_drop mathsy(18) /*superscript baseline below top of large box*/ +@d sub_drop mathsy(19) /*subscript baseline below bottom of large box*/ +@d delim1 mathsy(20) /*size of \.{\\atopwithdelims} delimiters + in display styles*/ +@d delim2 mathsy(21) /*size of \.{\\atopwithdelims} delimiters in non-displays*/ +@d axis_height mathsy(22) /*height of fraction lines above the baseline*/ +@d total_mathsy_params 22 + +@ The math-extension parameters have similar macros, but the size code is +omitted (since it is always |cur_size| when we refer to such parameters). +@^parameters for symbols@> +@^font parameters@> + +@d mathex(A) font_info[A+param_base[fam_fnt(3+cur_size)]].sc +@d default_rule_thickness mathex(8) /*thickness of \.{\\over} bars*/ +@d big_op_spacing1 mathex(9) /*minimum clearance above a displayed op*/ +@d big_op_spacing2 mathex(10) /*minimum clearance below a displayed op*/ +@d big_op_spacing3 mathex(11) /*minimum baselineskip above displayed op*/ +@d big_op_spacing4 mathex(12) /*minimum baselineskip below displayed op*/ +@d big_op_spacing5 mathex(13) /*padding above and below displayed limits*/ +@d total_mathex_params 13 + +@ We also need to compute the change in style between mlists and their +subsidiaries. The following macros define the subsidiary style for +an overlined nucleus (|cramped_style|), for a subscript or a superscript +(|sub_style| or |sup_style|), or for a numerator or denominator (|num_style| +or |denom_style|). + +@d cramped_style(A) 2*(A/2)+cramped /*cramp the style*/ +@d sub_style(A) 2*(A/4)+script_style+cramped /*smaller and cramped*/ +@d sup_style(A) 2*(A/4)+script_style+(A%2) /*smaller*/ +@d num_style(A) A+2-2*(A/6) /*smaller unless already script-script*/ +@d denom_style(A) 2*(A/2)+cramped+2-2*(A/6) /*smaller, cramped*/ + +@ When the style changes, the following piece of program computes associated +information: + +@<Set up the values of |cur_size| and |cur_mu|, based on |cur_style|@>= +{@+if (cur_style < script_style) cur_size=text_size; +else cur_size=16*((cur_style-text_style)/2); +cur_mu=x_over_n(math_quad(cur_size), 18); +} + +@ Here is a function that returns a pointer to a rule node having a given +thickness |t|. The rule will extend horizontally to the boundary of the vlist +that eventually contains it. + +@p static pointer fraction_rule(scaled @!t) + /*construct the bar for a fraction*/ +{@+pointer p; /*the new node*/ +p=new_rule();height(p)=t;depth(p)=0;return p; +} + +@ The |overbar| function returns a pointer to a vlist box that consists of +a given box |b|, above which has been placed a kern of height |k| under a +fraction rule of thickness |t| under additional space of height |t|. + +@p static pointer overbar(pointer @!b, scaled @!k, scaled @!t) +{@+pointer p, @!q; /*nodes being constructed*/ +p=new_kern(k);link(p)=b;q=fraction_rule(t);link(q)=p; +p=new_kern(t);link(p)=q;return vpack(p, natural); +} + +@ The |var_delimiter| function, which finds or constructs a sufficiently +large delimiter, is the most interesting of the auxiliary functions that +currently concern us. Given a pointer |d| to a delimiter field in some noad, +together with a size code |s| and a vertical distance |v|, this function +returns a pointer to a box that contains the smallest variant of |d| whose +height plus depth is |v| or more. (And if no variant is large enough, it +returns the largest available variant.) In particular, this routine will +construct arbitrarily large delimiters from extensible components, if +|d| leads to such characters. + +The value returned is a box whose |shift_amount| has been set so that +the box is vertically centered with respect to the axis in the given size. +If a built-up symbol is returned, the height of the box before shifting +will be the height of its topmost component. + +@p @t\4@>@<Declare subprocedures for |var_delimiter|@>@; +static pointer var_delimiter(pointer @!d, small_number @!s, scaled @!v) +{@+ +pointer b; /*the box that will be constructed*/ +internal_font_number @!f, @!g; /*best-so-far and tentative font codes*/ +quarterword @!c, @!x, @!y; /*best-so-far and tentative character codes*/ +int @!m, @!n; /*the number of extensible pieces*/ +scaled @!u; /*height-plus-depth of a tentative character*/ +scaled @!w; /*largest height-plus-depth so far*/ +four_quarters @!q; /*character info*/ +eight_bits @!hd; /*height-depth byte*/ +four_quarters @!r; /*extensible pieces*/ +small_number @!z; /*runs through font family members*/ +bool @!large_attempt; /*are we trying the ``large'' variant?*/ +f=null_font;w=0;large_attempt=false; +z=small_fam(d);x=small_char(d); +loop@+{@+@<Look at the variants of |(z,x)|; set |f| and |c| whenever a better +character is found; |goto found| as soon as a large enough variant is encountered@>; + if (large_attempt) goto found; /*there were none large enough*/ + large_attempt=true;z=large_fam(d);x=large_char(d); + } +found: if (f!=null_font) + @<Make variable |b| point to a box for |(f,c)|@>; +else{@+b=new_null_box(); + width(b)=null_delimiter_space; /*use this width if no delimiter was found*/ + } +shift_amount(b)=half(height(b)-depth(b))-axis_height(s); +return b; +} + +@ The search process is complicated slightly by the facts that some of the +characters might not be present in some of the fonts, and they might not +be probed in increasing order of height. + +@<Look at the variants of |(z,x)|; set |f| and |c|...@>= +if ((z!=0)||(x!=min_quarterword)) + {@+z=z+s+16; + @/do@+{z=z-16;g=fam_fnt(z); + if (g!=null_font) + @<Look at the list of characters starting with |x| in font |g|; set |f| +and |c| whenever a better character is found; |goto found| as soon as a large +enough variant is encountered@>; + }@+ while (!(z < 16)); + } + +@ @<Look at the list of characters starting with |x|...@>= +{@+y=x; +if ((qo(y) >= font_bc[g])&&(qo(y) <= font_ec[g])) + {@+resume: q=char_info(g, y); + if (char_exists(q)) + {@+if (char_tag(q)==ext_tag) + {@+f=g;c=y;goto found; + } + hd=height_depth(q); + u=char_height(g, hd)+char_depth(g, hd); + if (u > w) + {@+f=g;c=y;w=u; + if (u >= v) goto found; + } + if (char_tag(q)==list_tag) + {@+y=rem_byte(q);goto resume; + } + } + } +} + +@ Here is a subroutine that creates a new box, whose list contains a +single character, and whose width includes the italic correction for +that character. The height or depth of the box will be negative, if +the height or depth of the character is negative; thus, this routine +may deliver a slightly different result than |hpack| would produce. + +@<Declare subprocedures for |var_delimiter|@>= +static pointer char_box(internal_font_number @!f, quarterword @!c) +{@+four_quarters q; +eight_bits @!hd; /*|height_depth| byte*/ +pointer @!b, @!p; /*the new box and its character node*/ +q=char_info(f, c);hd=height_depth(q); +b=new_null_box();width(b)=char_width(f, q)+char_italic(f, q); +height(b)=char_height(f, hd);depth(b)=char_depth(f, hd); +p=get_avail();character(p)=c;font(p)=f;list_ptr(b)=p;return b; +} + +@ When the following code is executed, |char_tag(q)| will be equal to +|ext_tag| if and only if a built-up symbol is supposed to be returned. + +@<Make variable |b| point to a box for |(f,c)|@>= +if (char_tag(q)==ext_tag) + @<Construct an extensible character in a new box |b|, using recipe |rem_byte(q)| +and font |f|@>@; +else b=char_box(f, c) + +@ When we build an extensible character, it's handy to have the +following subroutine, which puts a given character on top +of the characters already in box |b|: + +@<Declare subprocedures for |var_delimiter|@>= +static void stack_into_box(pointer @!b, internal_font_number @!f, + quarterword @!c) +{@+pointer p; /*new node placed into |b|*/ +p=char_box(f, c);link(p)=list_ptr(b);list_ptr(b)=p; +height(b)=height(p); +} + +@ Another handy subroutine computes the height plus depth of +a given character: + +@<Declare subprocedures for |var_delimiter|@>= +static scaled height_plus_depth(internal_font_number @!f, quarterword @!c) +{@+four_quarters q; +eight_bits @!hd; /*|height_depth| byte*/ +q=char_info(f, c);hd=height_depth(q); +return char_height(f, hd)+char_depth(f, hd); +} + +@ @<Construct an extensible...@>= +{@+b=new_null_box(); +type(b)=vlist_node; +r=font_info[exten_base[f]+rem_byte(q)].qqqq;@/ +@<Compute the minimum suitable height, |w|, and the corresponding number of +extension steps, |n|; also set |width(b)|@>; +c=ext_bot(r); +if (c!=min_quarterword) stack_into_box(b, f, c); +c=ext_rep(r); +for (m=1; m<=n; m++) stack_into_box(b, f, c); +c=ext_mid(r); +if (c!=min_quarterword) + {@+stack_into_box(b, f, c);c=ext_rep(r); + for (m=1; m<=n; m++) stack_into_box(b, f, c); + } +c=ext_top(r); +if (c!=min_quarterword) stack_into_box(b, f, c); +depth(b)=w-height(b); +} + +@ The width of an extensible character is the width of the repeatable +module. If this module does not have positive height plus depth, +we don't use any copies of it, otherwise we use as few as possible +(in groups of two if there is a middle part). + +@<Compute the minimum suitable height, |w|, and...@>= +c=ext_rep(r);u=height_plus_depth(f, c); +w=0;q=char_info(f, c);width(b)=char_width(f, q)+char_italic(f, q);@/ +c=ext_bot(r);@+if (c!=min_quarterword) w=w+height_plus_depth(f, c); +c=ext_mid(r);@+if (c!=min_quarterword) w=w+height_plus_depth(f, c); +c=ext_top(r);@+if (c!=min_quarterword) w=w+height_plus_depth(f, c); +n=0; +if (u > 0) while (w < v) + {@+w=w+u;incr(n); + if (ext_mid(r)!=min_quarterword) w=w+u; + } + +@ The next subroutine is much simpler; it is used for numerators and +denominators of fractions as well as for displayed operators and +their limits above and below. It takes a given box~|b| and +changes it so that the new box is centered in a box of width~|w|. +The centering is done by putting \.{\\hss} glue at the left and right +of the list inside |b|, then packaging the new box; thus, the +actual box might not really be centered, if it already contains +infinite glue. + +The given box might contain a single character whose italic correction +has been added to the width of the box; in this case a compensating +kern is inserted. + +@p static pointer rebox(pointer @!b, scaled @!w) +{@+pointer p; /*temporary register for list manipulation*/ +internal_font_number @!f; /*font in a one-character box*/ +scaled @!v; /*width of a character without italic correction*/ +if ((width(b)!=w)&&(list_ptr(b)!=null)) + {@+if (type(b)==vlist_node) b=hpack(b, natural); + p=list_ptr(b); + if ((is_char_node(p))&&(link(p)==null)) + {@+f=font(p);v=char_width(f, char_info(f, character(p))); + if (v!=width(b)) link(p)=new_kern(width(b)-v); + } + free_node(b, box_node_size); + b=new_glue(ss_glue);link(b)=p; + while (link(p)!=null) p=link(p); + link(p)=new_glue(ss_glue); + return hpack(b, w, exactly); + } +else{@+width(b)=w;return b; + } +} + +@ Here is a subroutine that creates a new glue specification from another +one that is expressed in `\.{mu}', given the value of the math unit. + +@d mu_mult(A) nx_plus_y(n, A, xn_over_d(A, f, 0200000)) + +@p static pointer math_glue(pointer @!g, scaled @!m) +{@+pointer p; /*the new glue specification*/ +int @!n; /*integer part of |m|*/ +scaled @!f; /*fraction part of |m|*/ +n=x_over_n(m, 0200000);f=rem;@/ +if (f < 0) + {@+decr(n);f=f+0200000; + } +p=get_node(glue_spec_size); +width(p)=mu_mult(width(g)); /*convert \.{mu} to \.{pt}*/ +stretch_order(p)=stretch_order(g); +if (stretch_order(p)==normal) stretch(p)=mu_mult(stretch(g)); +else stretch(p)=stretch(g); +shrink_order(p)=shrink_order(g); +if (shrink_order(p)==normal) shrink(p)=mu_mult(shrink(g)); +else shrink(p)=shrink(g); +return p; +} + +@ The |math_kern| subroutine removes |mu_glue| from a kern node, given +the value of the math unit. + +@p static void math_kern(pointer @!p, scaled @!m) +{@+int @!n; /*integer part of |m|*/ +scaled @!f; /*fraction part of |m|*/ +if (subtype(p)==mu_glue) + {@+n=x_over_n(m, 0200000);f=rem;@/ + if (f < 0) + {@+decr(n);f=f+0200000; + } + width(p)=mu_mult(width(p));subtype(p)=explicit; + } +} + +@ Sometimes it is necessary to destroy an mlist. The following +subroutine empties the current list, assuming that |abs(mode)==mmode|. + +@p static void flush_math(void) +{@+flush_node_list(link(head));flush_node_list(incompleat_noad); +link(head)=null;tail=head;incompleat_noad=null; +} + +@* Typesetting math formulas. +\TeX's most important routine for dealing with formulas is called +|mlist_to_hlist|. After a formula has been scanned and represented as an +mlist, this routine converts it to an hlist that can be placed into a box +or incorporated into the text of a paragraph. There are three implicit +parameters, passed in global variables: |cur_mlist| points to the first +node or noad in the given mlist (and it might be |null|); |cur_style| is a +style code; and |mlist_penalties| is |true| if penalty nodes for potential +line breaks are to be inserted into the resulting hlist. After +|mlist_to_hlist| has acted, |link(temp_head)| points to the translated hlist. + +Since mlists can be inside mlists, the procedure is recursive. And since this +is not part of \TeX's inner loop, the program has been written in a manner +that stresses compactness over efficiency. +@^recursion@> + +@<Glob...@>= +static pointer @!cur_mlist; /*beginning of mlist to be translated*/ +static small_number @!cur_style; /*style code at current place in the list*/ +static small_number @!cur_size; /*size code corresponding to |cur_style|*/ +static scaled @!cur_mu; /*the math unit width corresponding to |cur_size|*/ +static bool @!mlist_penalties; /*should |mlist_to_hlist| insert penalties?*/ + +@ The recursion in |mlist_to_hlist| is due primarily to a subroutine +called |clean_box| that puts a given noad field into a box using a given +math style; |mlist_to_hlist| can call |clean_box|, which can call +|mlist_to_hlist|. +@^recursion@> + +The box returned by |clean_box| is ``clean'' in the +sense that its |shift_amount| is zero. + +@p static void mlist_to_hlist(void);@/ +static pointer clean_box(pointer @!p, small_number @!s) +{@+ +pointer q; /*beginning of a list to be boxed*/ +small_number @!save_style; /*|cur_style| to be restored*/ +pointer @!x; /*box to be returned*/ +pointer @!r; /*temporary pointer*/ +switch (math_type(p)) { +case math_char: {@+cur_mlist=new_noad();mem[nucleus(cur_mlist)]=mem[p]; + } @+break; +case sub_box: {@+q=info(p);goto found; + } +case sub_mlist: cur_mlist=info(p);@+break; +default:{@+q=new_null_box();goto found; + } +} @/ +save_style=cur_style;cur_style=s;mlist_penalties=false;@/ +mlist_to_hlist();q=link(temp_head); /*recursive call*/ +cur_style=save_style; /*restore the style*/ +@<Set up the values of |cur_size| and |cur_mu|, based on |cur_style|@>; +found: if (is_char_node(q)||(q==null)) x=hpack(q, natural); + else if ((link(q)==null)&&(type(q) <= vlist_node)&&(shift_amount(q)==0)) + x=q; /*it's already clean*/ + else x=hpack(q, natural); +@<Simplify a trivial box@>; +return x; +} + +@ Here we save memory space in a common case. + +@<Simplify a trivial box@>= +q=list_ptr(x); +if (is_char_node(q)) + {@+r=link(q); + if (r!=null) if (link(r)==null) if (!is_char_node(r)) + if (type(r)==kern_node) /*unneeded italic correction*/ + {@+free_node(r, small_node_size);link(q)=null; + } + } + +@ It is convenient to have a procedure that converts a |math_char| +field to an ``unpacked'' form. The |fetch| routine sets |cur_f|, |cur_c|, +and |cur_i| to the font code, character code, and character information bytes of +a given noad field. It also takes care of issuing error messages for +nonexistent characters; in such cases, |char_exists(cur_i)| will be |false| +after |fetch| has acted, and the field will also have been reset to |empty|. + +@p static void fetch(pointer @!a) /*unpack the |math_char| field |a|*/ +{@+cur_c=character(a);cur_f=fam_fnt(fam(a)+cur_size); +if (cur_f==null_font) + @<Complain about an undefined family and set |cur_i| null@>@; +else{@+if ((qo(cur_c) >= font_bc[cur_f])&&(qo(cur_c) <= font_ec[cur_f])) + cur_i=char_info(cur_f, cur_c); + else cur_i=null_character; + if (!(char_exists(cur_i))) + {@+char_warning(cur_f, qo(cur_c)); + math_type(a)=empty;cur_i=null_character; + } + } +} + +@ @<Complain about an undefined family...@>= +{@+print_err("");print_size(cur_size);print_char(' '); +print_int(fam(a));print(" is undefined (character "); +print_ASCII(qo(cur_c));print_char(')'); +help4("Somewhere in the math formula just ended, you used the",@/ +"stated character from an undefined font family. For example,",@/ +"plain TeX doesn't allow \\it or \\sl in subscripts. Proceed,",@/ +"and I'll try to forget that I needed that character."); +error();cur_i=null_character;math_type(a)=empty; +} + +@ The outputs of |fetch| are placed in global variables. + +@<Glob...@>= +static internal_font_number @!cur_f; /*the |font| field of a |math_char|*/ +static quarterword @!cur_c; /*the |character| field of a |math_char|*/ +static four_quarters @!cur_i; /*the |char_info| of a |math_char|, + or a lig/kern instruction*/ + +@ We need to do a lot of different things, so |mlist_to_hlist| makes two +passes over the given mlist. + +The first pass does most of the processing: It removes ``mu'' spacing from +glue, it recursively evaluates all subsidiary mlists so that only the +top-level mlist remains to be handled, it puts fractions and square roots +and such things into boxes, it attaches subscripts and superscripts, and +it computes the overall height and depth of the top-level mlist so that +the size of delimiters for a |left_noad| and a |right_noad| will be known. +The hlist resulting from each noad is recorded in that noad's |new_hlist| +field, an integer field that replaces the |nucleus| or |thickness|. +@^recursion@> + +The second pass eliminates all noads and inserts the correct glue and +penalties between nodes. + +@d new_hlist(A) mem[nucleus(A)].i /*the translation of an mlist*/ + +@ Here is the overall plan of |mlist_to_hlist|, and the list of its +local variables. + +@p @t\4@>@<Declare math construction procedures@>@; +static void mlist_to_hlist(void) +{@+ + +pointer mlist; /*beginning of the given list*/ +bool @!penalties; /*should penalty nodes be inserted?*/ +small_number @!style; /*the given style*/ +small_number @!save_style; /*holds |cur_style| during recursion*/ +pointer @!q; /*runs through the mlist*/ +pointer @!r; /*the most recent noad preceding |q|*/ +small_number @!r_type; /*the |type| of noad |r|, or |op_noad| if |r==null|*/ +small_number @!t; /*the effective |type| of noad |q| during the second pass*/ +pointer @!p, @!x, @!y, @!z; /*temporary registers for list construction*/ +int @!pen; /*a penalty to be inserted*/ +small_number @!s; /*the size of a noad to be deleted*/ +scaled @!max_h, @!max_d; /*maximum height and depth of the list translated so far*/ +scaled @!delta; /*offset between subscript and superscript*/ +mlist=cur_mlist;penalties=mlist_penalties; +style=cur_style; /*tuck global parameters away as local variables*/ +q=mlist;r=null;r_type=op_noad;max_h=0;max_d=0; +@<Set up the values of |cur_size| and |cur_mu|, based on |cur_style|@>; +while (q!=null) @<Process node-or-noad |q| as much as possible in preparation +for the second pass of |mlist_to_hlist|, then move to the next item in the +mlist@>; +@<Convert \(a)a final |bin_noad| to an |ord_noad|@>; +@<Make a second pass over the mlist, removing all noads and inserting the +proper spacing and penalties@>; +} + +@ We use the fact that no character nodes appear in an mlist, hence +the field |type(q)| is always present. + +@<Process node-or-noad...@>= +{@+@<Do first-pass processing based on |type(q)|; |goto done_with_noad| if +a noad has been fully processed, |goto check_dimensions| if it has been translated +into |new_hlist(q)|, or |goto done_with_node| if a node has been fully processed@>; +check_dimensions: z=hpack(new_hlist(q), natural); +if (height(z) > max_h) max_h=height(z); +if (depth(z) > max_d) max_d=depth(z); +free_node(z, box_node_size); +done_with_noad: r=q;r_type=type(r); +if (r_type==right_noad) + {@+r_type=left_noad;cur_style=style;@<Set up the values...@>; + } +done_with_node: q=link(q); +} + +@ One of the things we must do on the first pass is change a |bin_noad| to +an |ord_noad| if the |bin_noad| is not in the context of a binary operator. +The values of |r| and |r_type| make this fairly easy. + +@<Do first-pass processing...@>= +reswitch: delta=0; +switch (type(q)) { +case bin_noad: switch (r_type) { + case bin_noad: case op_noad: case rel_noad: + case open_noad: case punct_noad: case left_noad: + {@+type(q)=ord_noad;goto reswitch; + } + default:do_nothing; + } @+break; +case rel_noad: case close_noad: case punct_noad: + case right_noad: {@+@t@>@;@/ + @<Convert \(a)a final |bin_noad| to an |ord_noad|@>; + if (type(q)==right_noad) goto done_with_noad; + } @+break; +@t\4@>@<Cases for noads that can follow a |bin_noad|@>@; +@t\4@>@<Cases for nodes that can appear in an mlist, after which we |goto +done_with_node|@>@; +default:confusion("mlist1"); +@:this can't happen mlist1}{\quad mlist1@> +} @/ +@<Convert \(n)|nucleus(q)| to an hlist and attach the sub/superscripts@>@; + +@ @<Convert \(a)a final |bin_noad| to an |ord_noad|@>= +if (r_type==bin_noad) type(r)=ord_noad + +@ @<Cases for nodes that can appear in an mlist...@>= +case style_node: {@+cur_style=subtype(q); + @<Set up the values of |cur_size| and |cur_mu|, based on |cur_style|@>; + goto done_with_node; + } +case choice_node: @<Change this node to a style node followed by the correct +choice, then |goto done_with_node|@>@; +case ins_node: case mark_node: case adjust_node: + case whatsit_node: case penalty_node: + case disc_node: goto done_with_node; +case rule_node: {@+if (height(q) > max_h) max_h=height(q); + if (depth(q) > max_d) max_d=depth(q);goto done_with_node; + } +case glue_node: {@+@<Convert \(m)math glue to ordinary glue@>; + goto done_with_node; + } +case kern_node: {@+math_kern(q, cur_mu);goto done_with_node; + } + +@ @d choose_mlist(A) {@+p=A(q);A(q)=null;@+} + +@<Change this node to a style node...@>= +{@+switch (cur_style/2) { +case 0: choose_mlist(display_mlist)@;@+break; /*|display_style==0|*/ +case 1: choose_mlist(text_mlist)@;@+break; /*|text_style==2|*/ +case 2: choose_mlist(script_mlist)@;@+break; /*|script_style==4|*/ +case 3: choose_mlist(script_script_mlist); /*|script_script_style==6|*/ +} /*there are no other cases*/ +flush_node_list(display_mlist(q)); +flush_node_list(text_mlist(q)); +flush_node_list(script_mlist(q)); +flush_node_list(script_script_mlist(q));@/ +type(q)=style_node;subtype(q)=cur_style;width(q)=0;depth(q)=0; +if (p!=null) + {@+z=link(q);link(q)=p; + while (link(p)!=null) p=link(p); + link(p)=z; + } +goto done_with_node; +} + +@ Conditional math glue (`\.{\\nonscript}') results in a |glue_node| +pointing to |zero_glue|, with |subtype(q)==cond_math_glue|; in such a case +the node following will be eliminated if it is a glue or kern node and if the +current size is different from |text_size|. Unconditional math glue +(`\.{\\muskip}') is converted to normal glue by multiplying the dimensions +by |cur_mu|. +@!@:non\_script\_}{\.{\\nonscript} primitive@> + +@<Convert \(m)math glue to ordinary glue@>= +if (subtype(q)==mu_glue) + {@+x=glue_ptr(q); + y=math_glue(x, cur_mu);delete_glue_ref(x);glue_ptr(q)=y; + subtype(q)=normal; + } +else if ((cur_size!=text_size)&&(subtype(q)==cond_math_glue)) + {@+p=link(q); + if (p!=null) if ((type(p)==glue_node)||(type(p)==kern_node)) + {@+link(q)=link(p);link(p)=null;flush_node_list(p); + } + } + +@ @<Cases for noads that can follow a |bin_noad|@>= +case left_noad: goto done_with_noad; +case fraction_noad: {@+make_fraction(q);goto check_dimensions; + } +case op_noad: {@+delta=make_op(q); + if (subtype(q)==limits) goto check_dimensions; + } @+break; +case ord_noad: make_ord(q);@+break; +case open_noad: case inner_noad: do_nothing;@+break; +case radical_noad: make_radical(q);@+break; +case over_noad: make_over(q);@+break; +case under_noad: make_under(q);@+break; +case accent_noad: make_math_accent(q);@+break; +case vcenter_noad: make_vcenter(q);@+break; + +@ Most of the actual construction work of |mlist_to_hlist| is done +by procedures with names +like |make_fraction|, |make_radical|, etc. To illustrate +the general setup of such procedures, let's begin with a couple of +simple ones. + +@<Declare math...@>= +static void make_over(pointer @!q) +{@+info(nucleus(q))=@| + overbar(clean_box(nucleus(q), cramped_style(cur_style)),@| + 3*default_rule_thickness, default_rule_thickness); +math_type(nucleus(q))=sub_box; +} + +@ @<Declare math...@>= +static void make_under(pointer @!q) +{@+pointer p, @!x, @!y; /*temporary registers for box construction*/ +scaled @!delta; /*overall height plus depth*/ +x=clean_box(nucleus(q), cur_style); +p=new_kern(3*default_rule_thickness);link(x)=p; +link(p)=fraction_rule(default_rule_thickness); +y=vpack(x, natural); +delta=height(y)+depth(y)+default_rule_thickness; +height(y)=height(x);depth(y)=delta-height(y); +info(nucleus(q))=y;math_type(nucleus(q))=sub_box; +} + +@ @<Declare math...@>= +static void make_vcenter(pointer @!q) +{@+pointer v; /*the box that should be centered vertically*/ +scaled @!delta; /*its height plus depth*/ +v=info(nucleus(q)); +if (type(v)!=vlist_node) confusion("vcenter"); +@:this can't happen vcenter}{\quad vcenter@> +delta=height(v)+depth(v); +height(v)=axis_height(cur_size)+half(delta); +depth(v)=delta-height(v); +} + +@ According to the rules in the \.{DVI} file specifications, we ensure alignment +@^square roots@> +between a square root sign and the rule above its nucleus by assuming that the +baseline of the square-root symbol is the same as the bottom of the rule. The +height of the square-root symbol will be the thickness of the rule, and the +depth of the square-root symbol should exceed or equal the height-plus-depth +of the nucleus plus a certain minimum clearance~|clr|. The symbol will be +placed so that the actual clearance is |clr| plus half the excess. + +@<Declare math...@>= +static void make_radical(pointer @!q) +{@+pointer x, @!y; /*temporary registers for box construction*/ +scaled @!delta, @!clr; /*dimensions involved in the calculation*/ +x=clean_box(nucleus(q), cramped_style(cur_style)); +if (cur_style < text_style) /*display style*/ + clr=default_rule_thickness+(abs(math_x_height(cur_size))/4); +else{@+clr=default_rule_thickness;clr=clr+(abs(clr)/4); + } +y=var_delimiter(left_delimiter(q), cur_size, height(x)+depth(x)+clr+ + default_rule_thickness); +delta=depth(y)-(height(x)+depth(x)+clr); +if (delta > 0) clr=clr+half(delta); /*increase the actual clearance*/ +shift_amount(y)=-(height(x)+clr); +link(y)=overbar(x, clr, height(y)); +info(nucleus(q))=hpack(y, natural);math_type(nucleus(q))=sub_box; +} + +@ Slants are not considered when placing accents in math mode. The accenter is +centered over the accentee, and the accent width is treated as zero with +respect to the size of the final box. + +@<Declare math...@>= +static void make_math_accent(pointer @!q) +{@+ +pointer p, @!x, @!y; /*temporary registers for box construction*/ +int @!a; /*address of lig/kern instruction*/ +quarterword @!c; /*accent character*/ +internal_font_number @!f; /*its font*/ +four_quarters @!i; /*its |char_info|*/ +scaled @!s; /*amount to skew the accent to the right*/ +scaled @!h; /*height of character being accented*/ +scaled @!delta; /*space to remove between accent and accentee*/ +scaled @!w; /*width of the accentee, not including sub/superscripts*/ +fetch(accent_chr(q)); +if (char_exists(cur_i)) + {@+i=cur_i;c=cur_c;f=cur_f;@/ + @<Compute the amount of skew@>; + x=clean_box(nucleus(q), cramped_style(cur_style));w=width(x);h=height(x); + @<Switch to a larger accent if available and appropriate@>; + if (h < x_height(f)) delta=h;@+else delta=x_height(f); + if ((math_type(supscr(q))!=empty)||(math_type(subscr(q))!=empty)) + if (math_type(nucleus(q))==math_char) + @<Swap the subscript and superscript into box |x|@>; + y=char_box(f, c); + shift_amount(y)=s+half(w-width(y)); + width(y)=0;p=new_kern(-delta);link(p)=x;link(y)=p; + y=vpack(y, natural);width(y)=width(x); + if (height(y) < h) @<Make the height of box |y| equal to |h|@>; + info(nucleus(q))=y; + math_type(nucleus(q))=sub_box; + } +} + +@ @<Make the height of box |y|...@>= +{@+p=new_kern(h-height(y));link(p)=list_ptr(y);list_ptr(y)=p; +height(y)=h; +} + +@ @<Switch to a larger accent if available and appropriate@>= +loop@+{@+if (char_tag(i)!=list_tag) goto done; + y=rem_byte(i); + i=char_info(f, y); + if (!char_exists(i)) goto done; + if (char_width(f, i) > w) goto done; + c=y; + } +done: + +@ @<Compute the amount of skew@>= +s=0; +if (math_type(nucleus(q))==math_char) + {@+fetch(nucleus(q)); + if (char_tag(cur_i)==lig_tag) + {@+a=lig_kern_start(cur_f, cur_i); + cur_i=font_info[a].qqqq; + if (skip_byte(cur_i) > stop_flag) + {@+a=lig_kern_restart(cur_f, cur_i); + cur_i=font_info[a].qqqq; + } + loop@+{@+if (qo(next_char(cur_i))==skew_char[cur_f]) + {@+if (op_byte(cur_i) >= kern_flag) + if (skip_byte(cur_i) <= stop_flag) s=char_kern(cur_f, cur_i); + goto done1; + } + if (skip_byte(cur_i) >= stop_flag) goto done1; + a=a+qo(skip_byte(cur_i))+1; + cur_i=font_info[a].qqqq; + } + } + } +done1: + +@ @<Swap the subscript and superscript into box |x|@>= +{@+flush_node_list(x);x=new_noad(); +mem[nucleus(x)]=mem[nucleus(q)]; +mem[supscr(x)]=mem[supscr(q)]; +mem[subscr(x)]=mem[subscr(q)];@/ +mem[supscr(q)].hh=empty_field; +mem[subscr(q)].hh=empty_field;@/ +math_type(nucleus(q))=sub_mlist;info(nucleus(q))=x; +x=clean_box(nucleus(q), cur_style);delta=delta+height(x)-h;h=height(x); +} + +@ The |make_fraction| procedure is a bit different because it sets +|new_hlist(q)| directly rather than making a sub-box. + +@<Declare math...@>= +static void make_fraction(pointer @!q) +{@+pointer p, @!v, @!x, @!y, @!z; /*temporary registers for box construction*/ +scaled @!delta, @!delta1, @!delta2, @!shift_up, @!shift_down, @!clr; + /*dimensions for box calculations*/ +if (thickness(q)==default_code) thickness(q)=default_rule_thickness; +@<Create equal-width boxes |x| and |z| for the numerator and denominator, +and compute the default amounts |shift_up| and |shift_down| by which they +are displaced from the baseline@>; +if (thickness(q)==0) @<Adjust \(s)|shift_up| and |shift_down| for the case +of no fraction line@>@; +else@<Adjust \(s)|shift_up| and |shift_down| for the case of a fraction line@>; +@<Construct a vlist box for the fraction, according to |shift_up| and |shift_down|@>; +@<Put the \(f)fraction into a box with its delimiters, and make |new_hlist(q)| +point to it@>; +} + +@ @<Create equal-width boxes |x| and |z| for the numerator and denom...@>= +x=clean_box(numerator(q), num_style(cur_style)); +z=clean_box(denominator(q), denom_style(cur_style)); +if (width(x) < width(z)) x=rebox(x, width(z)); +else z=rebox(z, width(x)); +if (cur_style < text_style) /*display style*/ + {@+shift_up=num1(cur_size);shift_down=denom1(cur_size); + } +else{@+shift_down=denom2(cur_size); + if (thickness(q)!=0) shift_up=num2(cur_size); + else shift_up=num3(cur_size); + } + +@ The numerator and denominator must be separated by a certain minimum +clearance, called |clr| in the following program. The difference between +|clr| and the actual clearance is twice |delta|. + +@<Adjust \(s)|shift_up| and |shift_down| for the case of no fraction line@>= +{@+if (cur_style < text_style) clr=7*default_rule_thickness; +else clr=3*default_rule_thickness; +delta=half(clr-((shift_up-depth(x))-(height(z)-shift_down))); +if (delta > 0) + {@+shift_up=shift_up+delta; + shift_down=shift_down+delta; + } +} + +@ In the case of a fraction line, the minimum clearance depends on the actual +thickness of the line. + +@<Adjust \(s)|shift_up| and |shift_down| for the case of a fraction line@>= +{@+if (cur_style < text_style) clr=3*thickness(q); +else clr=thickness(q); +delta=half(thickness(q)); +delta1=clr-((shift_up-depth(x))-(axis_height(cur_size)+delta)); +delta2=clr-((axis_height(cur_size)-delta)-(height(z)-shift_down)); +if (delta1 > 0) shift_up=shift_up+delta1; +if (delta2 > 0) shift_down=shift_down+delta2; +} + +@ @<Construct a vlist box for the fraction...@>= +v=new_null_box();type(v)=vlist_node; +height(v)=shift_up+height(x);depth(v)=depth(z)+shift_down; +width(v)=width(x); /*this also equals |width(z)|*/ +if (thickness(q)==0) + {@+p=new_kern((shift_up-depth(x))-(height(z)-shift_down)); + link(p)=z; + } +else{@+y=fraction_rule(thickness(q));@/ + p=new_kern((axis_height(cur_size)-delta)-@|(height(z)-shift_down));@/ + link(y)=p;link(p)=z;@/ + p=new_kern((shift_up-depth(x))-(axis_height(cur_size)+delta)); + link(p)=y; + } +link(x)=p;list_ptr(v)=x + +@ @<Put the \(f)fraction into a box with its delimiters...@>= +if (cur_style < text_style) delta=delim1(cur_size); +else delta=delim2(cur_size); +x=var_delimiter(left_delimiter(q), cur_size, delta);link(x)=v;@/ +z=var_delimiter(right_delimiter(q), cur_size, delta);link(v)=z;@/ +new_hlist(q)=hpack(x, natural) + +@ If the nucleus of an |op_noad| is a single character, it is to be +centered vertically with respect to the axis, after first being enlarged +(via a character list in the font) if we are in display style. The normal +convention for placing displayed limits is to put them above and below the +operator in display style. + +The italic correction is removed from the character if there is a subscript +and the limits are not being displayed. The |make_op| +routine returns the value that should be used as an offset between +subscript and superscript. + +After |make_op| has acted, |subtype(q)| will be |limits| if and only if +the limits have been set above and below the operator. In that case, +|new_hlist(q)| will already contain the desired final box. + +@<Declare math...@>= +static scaled make_op(pointer @!q) +{@+scaled delta; /*offset between subscript and superscript*/ +pointer @!p, @!v, @!x, @!y, @!z; /*temporary registers for box construction*/ +quarterword @!c;@+four_quarters @!i; /*registers for character examination*/ +scaled @!shift_up, @!shift_down; /*dimensions for box calculation*/ +if ((subtype(q)==normal)&&(cur_style < text_style)) + subtype(q)=limits; +if (math_type(nucleus(q))==math_char) + {@+fetch(nucleus(q)); + if ((cur_style < text_style)&&(char_tag(cur_i)==list_tag)) /*make it larger*/ + {@+c=rem_byte(cur_i);i=char_info(cur_f, c); + if (char_exists(i)) + {@+cur_c=c;cur_i=i;character(nucleus(q))=c; + } + } + delta=char_italic(cur_f, cur_i);x=clean_box(nucleus(q), cur_style); + if ((math_type(subscr(q))!=empty)&&(subtype(q)!=limits)) + width(x)=width(x)-delta; /*remove italic correction*/ + shift_amount(x)=half(height(x)-depth(x))-axis_height(cur_size); + /*center vertically*/ + math_type(nucleus(q))=sub_box;info(nucleus(q))=x; + } +else delta=0; +if (subtype(q)==limits) + @<Construct a box with limits above and below it, skewed by |delta|@>; +return delta; +} + +@ The following program builds a vlist box |v| for displayed limits. The +width of the box is not affected by the fact that the limits may be skewed. + +@<Construct a box with limits above and below it...@>= +{@+x=clean_box(supscr(q), sup_style(cur_style)); +y=clean_box(nucleus(q), cur_style); +z=clean_box(subscr(q), sub_style(cur_style)); +v=new_null_box();type(v)=vlist_node;width(v)=width(y); +if (width(x) > width(v)) width(v)=width(x); +if (width(z) > width(v)) width(v)=width(z); +x=rebox(x, width(v));y=rebox(y, width(v));z=rebox(z, width(v));@/ +shift_amount(x)=half(delta);shift_amount(z)=-shift_amount(x); +height(v)=height(y);depth(v)=depth(y); +@<Attach the limits to |y| and adjust |height(v)|, |depth(v)| to account for +their presence@>; +new_hlist(q)=v; +} + +@ We use |shift_up| and |shift_down| in the following program for the +amount of glue between the displayed operator |y| and its limits |x| and +|z|. The vlist inside box |v| will consist of |x| followed by |y| followed +by |z|, with kern nodes for the spaces between and around them. + +@<Attach the limits to |y| and adjust |height(v)|, |depth(v)|...@>= +if (math_type(supscr(q))==empty) + {@+free_node(x, box_node_size);list_ptr(v)=y; + } +else{@+shift_up=big_op_spacing3-depth(x); + if (shift_up < big_op_spacing1) shift_up=big_op_spacing1; + p=new_kern(shift_up);link(p)=y;link(x)=p;@/ + p=new_kern(big_op_spacing5);link(p)=x;list_ptr(v)=p; + height(v)=height(v)+big_op_spacing5+height(x)+depth(x)+shift_up; + } +if (math_type(subscr(q))==empty) free_node(z, box_node_size); +else{@+shift_down=big_op_spacing4-height(z); + if (shift_down < big_op_spacing2) shift_down=big_op_spacing2; + p=new_kern(shift_down);link(y)=p;link(p)=z;@/ + p=new_kern(big_op_spacing5);link(z)=p; + depth(v)=depth(v)+big_op_spacing5+height(z)+depth(z)+shift_down; + } + +@ A ligature found in a math formula does not create a |ligature_node|, because +there is no question of hyphenation afterwards; the ligature will simply be +stored in an ordinary |char_node|, after residing in an |ord_noad|. + +The |math_type| is converted to |math_text_char| here if we would not want to +apply an italic correction to the current character unless it belongs +to a math font (i.e., a font with |space==0|). + +No boundary characters enter into these ligatures. + +@<Declare math...@>= +static void make_ord(pointer @!q) +{@+ +int a; /*address of lig/kern instruction*/ +pointer @!p, @!r; /*temporary registers for list manipulation*/ +restart: @t@>@;@/ +if (math_type(subscr(q))==empty) if (math_type(supscr(q))==empty) + if (math_type(nucleus(q))==math_char) + {@+p=link(q); + if (p!=null) if ((type(p) >= ord_noad)&&(type(p) <= punct_noad)) + if (math_type(nucleus(p))==math_char) + if (fam(nucleus(p))==fam(nucleus(q))) + {@+math_type(nucleus(q))=math_text_char; + fetch(nucleus(q)); + if (char_tag(cur_i)==lig_tag) + {@+a=lig_kern_start(cur_f, cur_i); + cur_c=character(nucleus(p)); + cur_i=font_info[a].qqqq; + if (skip_byte(cur_i) > stop_flag) + {@+a=lig_kern_restart(cur_f, cur_i); + cur_i=font_info[a].qqqq; + } + loop@+{@+@<If instruction |cur_i| is a kern with |cur_c|, attach the +kern after~|q|; or if it is a ligature with |cur_c|, combine noads |q| and~|p| +appropriately; then |return| if the cursor has moved past a noad, or |goto +restart|@>; + if (skip_byte(cur_i) >= stop_flag) return; + a=a+qo(skip_byte(cur_i))+1; + cur_i=font_info[a].qqqq; + } + } + } + } +} + +@ Note that a ligature between an |ord_noad| and another kind of noad +is replaced by an |ord_noad|, when the two noads collapse into one. +But we could make a parenthesis (say) change shape when it follows +certain letters. Presumably a font designer will define such +ligatures only when this convention makes sense. + +\chardef\@@='174 % vertical line to indicate character retention + +@<If instruction |cur_i| is a kern with |cur_c|,...@>= +if (next_char(cur_i)==cur_c) if (skip_byte(cur_i) <= stop_flag) + if (op_byte(cur_i) >= kern_flag) + {@+p=new_kern(char_kern(cur_f, cur_i)); + link(p)=link(q);link(q)=p;return; + } + else{@+check_interrupt; /*allow a way out of infinite ligature loop*/ + switch (op_byte(cur_i)) { + case qi(1): case qi(5): character(nucleus(q))=rem_byte(cur_i);@+break; /*\.{=:\@@}, \.{=:\@@>}*/ + case qi(2): case qi(6): character(nucleus(p))=rem_byte(cur_i);@+break; /*\.{\@@=:}, \.{\@@=:>}*/ + case qi(3): case qi(7): case qi(11): {@+r=new_noad(); /*\.{\@@=:\@@}, \.{\@@=:\@@>}, \.{\@@=:\@@>>}*/ + character(nucleus(r))=rem_byte(cur_i); + fam(nucleus(r))=fam(nucleus(q));@/ + link(q)=r;link(r)=p; + if (op_byte(cur_i) < qi(11)) math_type(nucleus(r))=math_char; + else math_type(nucleus(r))=math_text_char; /*prevent combination*/ + } @+break; + default:{@+link(q)=link(p); + character(nucleus(q))=rem_byte(cur_i); /*\.{=:}*/ + mem[subscr(q)]=mem[subscr(p)];mem[supscr(q)]=mem[supscr(p)];@/ + free_node(p, noad_size); + } + } + if (op_byte(cur_i) > qi(3)) return; + math_type(nucleus(q))=math_char;goto restart; + } + +@ When we get to the following part of the program, we have ``fallen through'' +from cases that did not lead to |check_dimensions| or |done_with_noad| or +|done_with_node|. Thus, |q|~points to a noad whose nucleus may need to be +converted to an hlist, and whose subscripts and superscripts need to be +appended if they are present. + +If |nucleus(q)| is not a |math_char|, the variable |delta| is the amount +by which a superscript should be moved right with respect to a subscript +when both are present. +@^subscripts@> +@^superscripts@> + +@<Convert \(n)|nucleus(q)| to an hlist and attach the sub/superscripts@>= +switch (math_type(nucleus(q))) { +case math_char: case math_text_char: + @<Create a character node |p| for |nucleus(q)|, possibly followed by a kern +node for the italic correction, and set |delta| to the italic correction if +a subscript is present@>@;@+break; +case empty: p=null;@+break; +case sub_box: p=info(nucleus(q));@+break; +case sub_mlist: {@+cur_mlist=info(nucleus(q));save_style=cur_style; + mlist_penalties=false;mlist_to_hlist(); /*recursive call*/ +@^recursion@> + cur_style=save_style;@<Set up the values...@>; + p=hpack(link(temp_head), natural); + } @+break; +default:confusion("mlist2"); +@:this can't happen mlist2}{\quad mlist2@> +} @/ +new_hlist(q)=p; +if ((math_type(subscr(q))==empty)&&(math_type(supscr(q))==empty)) + goto check_dimensions; +make_scripts(q, delta) + +@ @<Create a character node |p| for |nucleus(q)|...@>= +{@+fetch(nucleus(q)); +if (char_exists(cur_i)) + {@+delta=char_italic(cur_f, cur_i);p=new_character(cur_f, qo(cur_c)); + if ((math_type(nucleus(q))==math_text_char)&&(space(cur_f)!=0)) + delta=0; /*no italic correction in mid-word of text font*/ + if ((math_type(subscr(q))==empty)&&(delta!=0)) + {@+link(p)=new_kern(delta);delta=0; + } + } +else p=null; +} + +@ The purpose of |make_scripts(q, delta)| is to attach the subscript and/or +superscript of noad |q| to the list that starts at |new_hlist(q)|, +given that the subscript and superscript aren't both empty. The superscript +will appear to the right of the subscript by a given distance |delta|. + +We set |shift_down| and |shift_up| to the minimum amounts to shift the +baseline of subscripts and superscripts based on the given nucleus. + +@<Declare math...@>= +static void make_scripts(pointer @!q, scaled @!delta) +{@+pointer p, @!x, @!y, @!z; /*temporary registers for box construction*/ +scaled @!shift_up, @!shift_down, @!clr; /*dimensions in the calculation*/ +small_number @!t; /*subsidiary size code*/ +p=new_hlist(q); +if (is_char_node(p)) + {@+shift_up=0;shift_down=0; + } +else{@+z=hpack(p, natural); + if (cur_style < script_style) t=script_size;@+else t=script_script_size; + shift_up=height(z)-sup_drop(t); + shift_down=depth(z)+sub_drop(t); + free_node(z, box_node_size); + } +if (math_type(supscr(q))==empty) + @<Construct a subscript box |x| when there is no superscript@>@; +else{@+@<Construct a superscript box |x|@>; + if (math_type(subscr(q))==empty) shift_amount(x)=-shift_up; + else@<Construct a sub/superscript combination box |x|, with the superscript +offset by |delta|@>; + } +if (new_hlist(q)==null) new_hlist(q)=x; +else{@+p=new_hlist(q); + while (link(p)!=null) p=link(p); + link(p)=x; + } +} + +@ When there is a subscript without a superscript, the top of the subscript +should not exceed the baseline plus four-fifths of the x-height. + +@<Construct a subscript box |x| when there is no superscript@>= +{@+x=clean_box(subscr(q), sub_style(cur_style)); +width(x)=width(x)+script_space; +if (shift_down < sub1(cur_size)) shift_down=sub1(cur_size); +clr=height(x)-(abs(math_x_height(cur_size)*4)/5); +if (shift_down < clr) shift_down=clr; +shift_amount(x)=shift_down; +} + +@ The bottom of a superscript should never descend below the baseline plus +one-fourth of the x-height. + +@<Construct a superscript box |x|@>= +{@+x=clean_box(supscr(q), sup_style(cur_style)); +width(x)=width(x)+script_space; +if (odd(cur_style)) clr=sup3(cur_size); +else if (cur_style < text_style) clr=sup1(cur_size); +else clr=sup2(cur_size); +if (shift_up < clr) shift_up=clr; +clr=depth(x)+(abs(math_x_height(cur_size))/4); +if (shift_up < clr) shift_up=clr; +} + +@ When both subscript and superscript are present, the subscript must be +separated from the superscript by at least four times |default_rule_thickness|. +If this condition would be violated, the subscript moves down, after which +both subscript and superscript move up so that the bottom of the superscript +is at least as high as the baseline plus four-fifths of the x-height. + +@<Construct a sub/superscript combination box |x|...@>= +{@+y=clean_box(subscr(q), sub_style(cur_style)); +width(y)=width(y)+script_space; +if (shift_down < sub2(cur_size)) shift_down=sub2(cur_size); +clr=4*default_rule_thickness- + ((shift_up-depth(x))-(height(y)-shift_down)); +if (clr > 0) + {@+shift_down=shift_down+clr; + clr=(abs(math_x_height(cur_size)*4)/5)-(shift_up-depth(x)); + if (clr > 0) + {@+shift_up=shift_up+clr; + shift_down=shift_down-clr; + } + } +shift_amount(x)=delta; /*superscript is |delta| to the right of the subscript*/ +p=new_kern((shift_up-depth(x))-(height(y)-shift_down));link(x)=p;link(p)=y; +x=vpack(x, natural);shift_amount(x)=shift_down; +} + +@ We have now tied up all the loose ends of the first pass of |mlist_to_hlist|. +The second pass simply goes through and hooks everything together with the +proper glue and penalties. It also handles the |left_noad| and |right_noad| that +might be present, since |max_h| and |max_d| are now known. Variable |p| points +to a node at the current end of the final hlist. + +@<Make a second pass over the mlist,...@>= +p=temp_head;link(p)=null;q=mlist;r_type=0;cur_style=style; +@<Set up the values of |cur_size| and |cur_mu|, based on |cur_style|@>; +while (q!=null) + {@+@<If node |q| is a style node, change the style and |goto delete_q|; +otherwise if it is not a noad, put it into the hlist, advance |q|, and |goto +done|; otherwise set |s| to the size of noad |q|, set |t| to the associated +type (|ord_noad.. inner_noad|), and set |pen| to the associated penalty@>; + @<Append inter-element spacing based on |r_type| and |t|@>; + @<Append any |new_hlist| entries for |q|, and any appropriate penalties@>; + if (type(q)==right_noad) t=open_noad; + r_type=t; + delete_q: r=q;q=link(q);free_node(r, s); + done: ;} + +@ Just before doing the big |case| switch in the second pass, the program +sets up default values so that most of the branches are short. + +@<If node |q| is a style node, change the style...@>= +t=ord_noad;s=noad_size;pen=inf_penalty; +switch (type(q)) { +case op_noad: case open_noad: case close_noad: + case punct_noad: case inner_noad: t=type(q);@+break; +case bin_noad: {@+t=bin_noad;pen=bin_op_penalty; + } @+break; +case rel_noad: {@+t=rel_noad;pen=rel_penalty; + } @+break; +case ord_noad: case vcenter_noad: case over_noad: + case under_noad: do_nothing;@+break; +case radical_noad: s=radical_noad_size;@+break; +case accent_noad: s=accent_noad_size;@+break; +case fraction_noad: s=fraction_noad_size;@+break; +case left_noad: case right_noad: t=make_left_right(q, style, max_d, max_h);@+break; +case style_node: @<Change the current style and |goto delete_q|@>@; +case whatsit_node: case penalty_node: + case rule_node: case disc_node: case adjust_node: + case ins_node: case mark_node: + case glue_node: case kern_node: @t@>@;@/ + {@+link(p)=q;p=q;q=link(q);link(p)=null;goto done; + } +default:confusion("mlist3"); +@:this can't happen mlist3}{\quad mlist3@> +} + +@ The |make_left_right| function constructs a left or right delimiter of +the required size and returns the value |open_noad| or |close_noad|. The +|right_noad| and |left_noad| will both be based on the original |style|, +so they will have consistent sizes. + +We use the fact that |right_noad-left_noad==close_noad-open_noad|. + +@<Declare math...@>= +static small_number make_left_right(pointer @!q, small_number @!style, + scaled @!max_d, scaled @!max_h) +{@+scaled delta, @!delta1, @!delta2; /*dimensions used in the calculation*/ +cur_style=style;@<Set up the values...@>; +delta2=max_d+axis_height(cur_size); +delta1=max_h+max_d-delta2; +if (delta2 > delta1) delta1=delta2; /*|delta1| is max distance from axis*/ +delta=(delta1/500)*delimiter_factor; +delta2=delta1+delta1-delimiter_shortfall; +if (delta < delta2) delta=delta2; +new_hlist(q)=var_delimiter(delimiter(q), cur_size, delta); +return type(q)-(left_noad-open_noad); /*|open_noad| or |close_noad|*/ +} + +@ @<Change the current style and |goto delete_q|@>= +{@+cur_style=subtype(q);s=style_node_size; +@<Set up the values of |cur_size| and |cur_mu|, based on |cur_style|@>; +goto delete_q; +} + +@ The inter-element spacing in math formulas depends on an $8\times8$ table that +\TeX\ preloads as a 64-digit string. The elements of this string have the +following significance: +$$\vbox{\halign{#\hfil\cr +\.0 means no space;\cr +\.1 means a conditional thin space (\.{\\nonscript\\mskip\\thinmuskip});\cr +\.2 means a thin space (\.{\\mskip\\thinmuskip});\cr +\.3 means a conditional medium space + (\.{\\nonscript\\mskip\\medmuskip});\cr +\.4 means a conditional thick space + (\.{\\nonscript\\mskip\\thickmuskip});\cr +\.* means an impossible case.\cr}}$$ +This is all pretty cryptic, but {\sl The \TeX book\/} explains what is +supposed to happen, and the string makes it happen. +@:TeXbook}{\sl The \TeX book@> + +A global variable |magic_offset| is computed so that if |a| and |b| are +in the range |ord_noad dotdot inner_noad|, then |str_pool[a*8+b+magic_offset]| +is the digit for spacing between noad types |a| and |b|. + +If \PASCAL\ had provided a good way to preload constant arrays, this part of +the program would not have been so strange. +@:PASCAL}{\PASCAL@> + +@d math_spacing @;@/ +@t\hskip-35pt@> +"0234000122*4000133**3**344*0400400*000000234000111*1111112341011" +@t$ \hskip-35pt$@> + +@ @<Glob...@>= +static const int @!magic_offset=-9*ord_noad; /*used to find inter-element spacing*/ + +@ @<Append inter-element spacing based on |r_type| and |t|@>= +if (r_type > 0) /*not the first noad*/ + {@+switch (so(math_spacing[r_type*8+t+magic_offset])) { + case '0': x=0;@+break; + case '1': if (cur_style < script_style) x=thin_mu_skip_code;@+else x=0;@+break; + case '2': x=thin_mu_skip_code;@+break; + case '3': if (cur_style < script_style) x=med_mu_skip_code;@+else x=0;@+break; + case '4': if (cur_style < script_style) x=thick_mu_skip_code;@+else x=0;@+break; + default:confusion("mlist4"); +@:this can't happen mlist4}{\quad mlist4@> + } + if (x!=0) + {@+y=math_glue(glue_par(x), cur_mu); + z=new_glue(y);glue_ref_count(y)=null;link(p)=z;p=z;@/ + subtype(z)=x+1; /*store a symbolic subtype*/ + } + } + +@ We insert a penalty node after the hlist entries of noad |q| if |pen| +is not an ``infinite'' penalty, and if the node immediately following |q| +is not a penalty node or a |rel_noad| or absent entirely. + +@<Append any |new_hlist| entries for |q|, and any appropriate penalties@>= +if (new_hlist(q)!=null) + {@+link(p)=new_hlist(q); + @/do@+{p=link(p); + }@+ while (!(link(p)==null)); + } +if (penalties) if (link(q)!=null) if (pen < inf_penalty) + {@+r_type=type(link(q)); + if (r_type!=penalty_node) if (r_type!=rel_noad) + {@+z=new_penalty(pen);link(p)=z;p=z; + } + } + +@* Alignment. +It's sort of a miracle whenever \.{\\halign} and \.{\\valign} work, because +they cut across so many of the control structures of \TeX. + +Therefore the +present page is probably not the best place for a beginner to start reading +this program; it is better to master everything else first. + +Let us focus our thoughts on an example of what the input might be, in order +to get some idea about how the alignment miracle happens. The example doesn't +do anything useful, but it is sufficiently general to indicate all of the +special cases that must be dealt with; please do not be disturbed by its +apparent complexity and meaninglessness. +$$\vbox{\halign{\.{#}\hfil\cr +{}\\tabskip 2pt plus 3pt\cr +{}\\halign to 300pt\{u1\#v1\&\cr +\hskip 50pt\\tabskip 1pt plus 1fil u2\#v2\&\cr +\hskip 50pt u3\#v3\\cr\cr +\hskip 25pt a1\&\\omit a2\&\\vrule\\cr\cr +\hskip 25pt \\noalign\{\\vskip 3pt\}\cr +\hskip 25pt b1\\span b2\\cr\cr +\hskip 25pt \\omit\&c2\\span\\omit\\cr\}\cr}}$$ +Here's what happens: + +\yskip +(0) When `\.{\\halign to 300pt\{}' is scanned, the |scan_spec| routine +places the 300pt dimension onto the |save_stack|, and an |align_group| +code is placed above it. This will make it possible to complete the alignment +when the matching `\.\}' is found. + +(1) The preamble is scanned next. Macros in the preamble are not expanded, +@^preamble@> +except as part of a tabskip specification. For example, if \.{u2} had been +a macro in the preamble above, it would have been expanded, since \TeX\ +must look for `\.{minus...}' as part of the tabskip glue. A ``preamble list'' +is constructed based on the user's preamble; in our case it contains the +following seven items: +$$\vbox{\halign{\.{#}\hfil\qquad&(#)\hfil\cr +{}\\glue 2pt plus 3pt&the tabskip preceding column 1\cr +{}\\alignrecord, width $-\infty$&preamble info for column 1\cr +{}\\glue 2pt plus 3pt&the tabskip between columns 1 and 2\cr +{}\\alignrecord, width $-\infty$&preamble info for column 2\cr +{}\\glue 1pt plus 1fil&the tabskip between columns 2 and 3\cr +{}\\alignrecord, width $-\infty$&preamble info for column 3\cr +{}\\glue 1pt plus 1fil&the tabskip following column 3\cr}}$$ +These ``alignrecord'' entries have the same size as an |unset_node|, +since they will later be converted into such nodes. However, at the +moment they have no |type| or |subtype| fields; they have |info| fields +instead, and these |info| fields are initially set to the value |end_span|, +for reasons explained below. Furthermore, the alignrecord nodes have no +|height| or |depth| fields; these are renamed |u_part| and |v_part|, +and they point to token lists for the templates of the alignment. +For example, the |u_part| field in the first alignrecord points to the +token list `\.{u1}', i.e., the template preceding the `\.\#' for column~1. + +(2) \TeX\ now looks at what follows the \.{\\cr} that ended the preamble. +It is not `\.{\\noalign}' or `\.{\\omit}', so this input is put back to +be read again, and the template `\.{u1}' is fed to the scanner. Just +before reading `\.{u1}', \TeX\ goes into restricted horizontal mode. +Just after reading `\.{u1}', \TeX\ will see `\.{a1}', and then (when the +{\.\&} is sensed) \TeX\ will see `\.{v1}'. Then \TeX\ scans an |endv| +token, indicating the end of a column. At this point an |unset_node| is +created, containing the contents of the current hlist (i.e., `\.{u1a1v1}'). +The natural width of this unset node replaces the |width| field of the +alignrecord for column~1; in general, the alignrecords will record the +maximum natural width that has occurred so far in a given column. + +(3) Since `\.{\\omit}' follows the `\.\&', the templates for column~2 +are now bypassed. Again \TeX\ goes into restricted horizontal mode and +makes an |unset_node| from the resulting hlist; but this time the +hlist contains simply `\.{a2}'. The natural width of the new unset box +is remembered in the |width| field of the alignrecord for column~2. + +(4) A third |unset_node| is created for column 3, using essentially the +mechanism that worked for column~1; this unset box contains `\.{u3\\vrule +v3}'. The vertical rule in this case has running dimensions that will later +extend to the height and depth of the whole first row, since each |unset_node| +in a row will eventually inherit the height and depth of its enclosing box. + +(5) The first row has now ended; it is made into a single unset box +comprising the following seven items: +$$\vbox{\halign{\hbox to 325pt{\qquad\.{#}\hfil}\cr +{}\\glue 2pt plus 3pt\cr +{}\\unsetbox for 1 column: u1a1v1\cr +{}\\glue 2pt plus 3pt\cr +{}\\unsetbox for 1 column: a2\cr +{}\\glue 1pt plus 1fil\cr +{}\\unsetbox for 1 column: u3\\vrule v3\cr +{}\\glue 1pt plus 1fil\cr}}$$ +The width of this unset row is unimportant, but it has the correct height +and depth, so the correct baselineskip glue will be computed as the row +is inserted into a vertical list. + +(6) Since `\.{\\noalign}' follows the current \.{\\cr}, \TeX\ appends +additional material (in this case \.{\\vskip 3pt}) to the vertical list. +While processing this material, \TeX\ will be in internal vertical +mode, and |no_align_group| will be on |save_stack|. + +(7) The next row produces an unset box that looks like this: +$$\vbox{\halign{\hbox to 325pt{\qquad\.{#}\hfil}\cr +{}\\glue 2pt plus 3pt\cr +{}\\unsetbox for 2 columns: u1b1v1u2b2v2\cr +{}\\glue 1pt plus 1fil\cr +{}\\unsetbox for 1 column: {\rm(empty)}\cr +{}\\glue 1pt plus 1fil\cr}}$$ +The natural width of the unset box that spans columns 1~and~2 is stored +in a ``span node,'' which we will explain later; the |info| field of the +alignrecord for column~1 now points to the new span node, and the |info| +of the span node points to |end_span|. + +(8) The final row produces the unset box +$$\vbox{\halign{\hbox to 325pt{\qquad\.{#}\hfil}\cr +{}\\glue 2pt plus 3pt\cr +{}\\unsetbox for 1 column: {\rm(empty)}\cr +{}\\glue 2pt plus 3pt\cr +{}\\unsetbox for 2 columns: u2c2v2\cr +{}\\glue 1pt plus 1fil\cr}}$$ +A new span node is attached to the alignrecord for column 2. + +(9) The last step is to compute the true column widths and to change all the +unset boxes to hboxes, appending the whole works to the vertical list that +encloses the \.{\\halign}. The rules for deciding on the final widths of +each unset column box will be explained below. + +\yskip\noindent +Note that as \.{\\halign} is being processed, we fearlessly give up control +to the rest of \TeX. At critical junctures, an alignment routine is +called upon to step in and do some little action, but most of the time +these routines just lurk in the background. It's something like +post-hypnotic suggestion. + +@ We have mentioned that alignrecords contain no |height| or |depth| fields. +Their |glue_sign| and |glue_order| are pre-empted as well, since it +is necessary to store information about what to do when a template ends. +This information is called the |extra_info| field. + +@d u_part(A) mem[A+height_offset].i /*pointer to \<u_j> token list*/ +@d v_part(A) mem[A+depth_offset].i /*pointer to \<v_j> token list*/ +@d extra_info(A) info(A+list_offset) /*info to remember during template*/ + +@ Alignments can occur within alignments, so a small stack is used to access +the alignrecord information. At each level we have a |preamble| pointer, +indicating the beginning of the preamble list; a |cur_align| pointer, +indicating the current position in the preamble list; a |cur_span| pointer, +indicating the value of |cur_align| at the beginning of a sequence of +spanned columns; a |cur_loop| pointer, indicating the tabskip glue before +an alignrecord that should be copied next if the current list is extended; +and the |align_state| variable, which indicates the nesting of braces so +that \.{\\cr} and \.{\\span} and tab marks are properly intercepted. +There also are pointers |cur_head| and |cur_tail| to the head and tail +of a list of adjustments being moved out from horizontal mode to +vertical~mode. + +The current values of these seven quantities appear in global variables; +when they have to be pushed down, they are stored in 5-word nodes, and +|align_ptr| points to the topmost such node. + +@d preamble link(align_head) /*the current preamble list*/ +@d align_stack_node_size 5 /*number of |mem| words to save alignment states*/ + +@<Glob...@>= +static pointer @!cur_align; /*current position in preamble list*/ +static pointer @!cur_span; /*start of currently spanned columns in preamble list*/ +static pointer @!cur_loop; /*place to copy when extending a periodic preamble*/ +static pointer @!align_ptr; /*most recently pushed-down alignment stack node*/ +static pointer @!cur_head, @!cur_tail; /*adjustment list pointers*/ + +@ The |align_state| and |preamble| variables are initialized elsewhere. + +@<Set init...@>= +align_ptr=null;cur_align=null;cur_span=null;cur_loop=null; +cur_head=null;cur_tail=null; + +@ Alignment stack maintenance is handled by a pair of trivial routines +called |push_alignment| and |pop_alignment|. + +@p static void push_alignment(void) +{@+pointer p; /*the new alignment stack node*/ +p=get_node(align_stack_node_size); +link(p)=align_ptr;info(p)=cur_align; +llink(p)=preamble;rlink(p)=cur_span; +mem[p+2].i=cur_loop;mem[p+3].i=align_state; +info(p+4)=cur_head;link(p+4)=cur_tail; +align_ptr=p; +cur_head=get_avail(); +} +@# +static void pop_alignment(void) +{@+pointer p; /*the top alignment stack node*/ +free_avail(cur_head); +p=align_ptr; +cur_tail=link(p+4);cur_head=info(p+4); +align_state=mem[p+3].i;cur_loop=mem[p+2].i; +cur_span=rlink(p);preamble=llink(p); +cur_align=info(p);align_ptr=link(p); +free_node(p, align_stack_node_size); +} + +@ \TeX\ has eight procedures that govern alignments: |init_align| and +|fin_align| are used at the very beginning and the very end; |init_row| and +|fin_row| are used at the beginning and end of individual rows; |init_span| +is used at the beginning of a sequence of spanned columns (possibly involving +only one column); |init_col| and |fin_col| are used at the beginning and +end of individual columns; and |align_peek| is used after \.{\\cr} to see +whether the next item is \.{\\noalign}. + +We shall consider these routines in the order they are first used during +the course of a complete \.{\\halign}, namely |init_align|, |align_peek|, +|init_row|, |init_span|, |init_col|, |fin_col|, |fin_row|, |fin_align|. + +@ When \.{\\halign} or \.{\\valign} has been scanned in an appropriate +mode, \TeX\ calls |init_align|, whose task is to get everything off to a +good start. This mostly involves scanning the preamble and putting its +information into the preamble list. +@^preamble@> + +@p @t\4@>@<Declare the procedure called |get_preamble_token|@>@t@>@/ +static void align_peek(void);@/ +static void normal_paragraph(void);@/ +static void init_align(void) +{@+ +pointer save_cs_ptr; /*|warning_index| value for error messages*/ +pointer @!p; /*for short-term temporary use*/ +save_cs_ptr=cur_cs; /*\.{\\halign} or \.{\\valign}, usually*/ +push_alignment();align_state=-1000000; /*enter a new alignment level*/ +@<Check for improper alignment in displayed math@>; +push_nest(); /*enter a new semantic level*/ +@<Change current mode to |-vmode| for \.{\\halign}, |-hmode| for \.{\\valign}@>; +scan_spec(align_group, false);@/ +@<Scan the preamble and record it in the |preamble| list@>; +new_save_level(align_group); +if (every_cr!=null) begin_token_list(every_cr, every_cr_text); +align_peek(); /*look for \.{\\noalign} or \.{\\omit}*/ +} + +@ In vertical modes, |prev_depth| already has the correct value. But +if we are in |mmode| (displayed formula mode), we reach out to the +enclosing vertical mode for the |prev_depth| value that produces the +correct baseline calculations. + +@<Change current mode...@>= +if (mode==mmode) + {@+mode=-vmode;prev_depth=nest[nest_ptr-2].aux_field.sc; + } +else if (mode > 0) negate(mode) + +@ When \.{\\halign} is used as a displayed formula, there should be +no other pieces of mlists present. + +@<Check for improper alignment in displayed math@>= +if ((mode==mmode)&&((tail!=head)||(incompleat_noad!=null))) + {@+print_err("Improper ");print_esc("halign");print(" inside $$'s"); +@.Improper \\halign...@> + help3("Displays can use special alignments (like \\eqalignno)",@/ + "only if nothing but the alignment itself is between $$'s.",@/ + "So I've deleted the formulas that preceded this alignment."); + error();flush_math(); + } + +@ @<Scan the preamble and record it in the |preamble| list@>= +preamble=null;cur_align=align_head;cur_loop=null;scanner_status=aligning; +warning_index=save_cs_ptr;align_state=-1000000; + /*at this point, |cur_cmd==left_brace|*/ +loop@+{@+@<Append the current tabskip glue to the preamble list@>; + if (cur_cmd==car_ret) goto done; /*\.{\\cr} ends the preamble*/ + @<Scan preamble text until |cur_cmd| is |tab_mark| or |car_ret|, looking +for changes in the tabskip glue; append an alignrecord to the preamble list@>; + } +done: scanner_status=normal + +@ @<Append the current tabskip glue to the preamble list@>= +link(cur_align)=new_param_glue(tab_skip_code); +cur_align=link(cur_align) + +@ @<Scan preamble text until |cur_cmd| is |tab_mark| or |car_ret|...@>= +@<Scan the template \<u_j>, putting the resulting token list in |hold_head|@>; +link(cur_align)=new_null_box();cur_align=link(cur_align); /*a new alignrecord*/ +info(cur_align)=end_span;width(cur_align)=null_flag; +u_part(cur_align)=link(hold_head); +@<Scan the template \<v_j>, putting the resulting token list in |hold_head|@>; +v_part(cur_align)=link(hold_head) + +@ We enter `\.{\\span}' into |eqtb| with |tab_mark| as its command code, +and with |span_code| as the command modifier. This makes \TeX\ interpret it +essentially the same as an alignment delimiter like `\.\&', yet it is +recognizably different when we need to distinguish it from a normal delimiter. +It also turns out to be useful to give a special |cr_code| to `\.{\\cr}', +and an even larger |cr_cr_code| to `\.{\\crcr}'. + +The end of a template is represented by two ``frozen'' control sequences +called \.{\\endtemplate}. The first has the command code |end_template|, which +is | > outer_call|, so it will not easily disappear in the presence of errors. +The |get_x_token| routine converts the first into the second, which has |endv| +as its command code. + +@d span_code 256 /*distinct from any character*/ +@d cr_code 257 /*distinct from |span_code| and from any character*/ +@d cr_cr_code (cr_code+1) /*this distinguishes \.{\\crcr} from \.{\\cr}*/ +@d end_template_token cs_token_flag+frozen_end_template + +@<Put each of \TeX's primitives into the hash table@>= +primitive("span", tab_mark, span_code);@/ +@!@:span\_}{\.{\\span} primitive@> +primitive("cr", car_ret, cr_code); +@!@:cr\_}{\.{\\cr} primitive@> +text(frozen_cr)=text(cur_val);eqtb[frozen_cr]=eqtb[cur_val];@/ +primitive("crcr", car_ret, cr_cr_code); +@!@:cr\_cr\_}{\.{\\crcr} primitive@> +text(frozen_end_template)=text(frozen_endv)=s_no("endtemplate"); +@.endtemplate@> +eq_type(frozen_endv)=endv;equiv(frozen_endv)=null_list; +eq_level(frozen_endv)=level_one;@/ +eqtb[frozen_end_template]=eqtb[frozen_endv]; +eq_type(frozen_end_template)=end_template; + +@ @<Cases of |print_cmd_chr|...@>= +case tab_mark: if (chr_code==span_code) print_esc("span"); + else chr_cmd("alignment tab character ")@;@+break; +case car_ret: if (chr_code==cr_code) print_esc("cr"); + else print_esc("crcr");@+break; + +@ The preamble is copied directly, except that \.{\\tabskip} causes a change +to the tabskip glue, thereby possibly expanding macros that immediately +follow it. An appearance of \.{\\span} also causes such an expansion. + +Note that if the preamble contains `\.{\\global\\tabskip}', the `\.{\\global}' +token survives in the preamble and the `\.{\\tabskip}' defines new +tabskip glue (locally). + +@<Declare the procedure called |get_preamble_token|@>= +static void get_preamble_token(void) +{@+ +restart: get_token(); +while ((cur_chr==span_code)&&(cur_cmd==tab_mark)) + {@+get_token(); /*this token will be expanded once*/ + if (cur_cmd > max_command) + {@+expand();get_token(); + } + } +if (cur_cmd==endv) + fatal_error("(interwoven alignment preambles are not allowed)"); +@.interwoven alignment preambles...@> +if ((cur_cmd==assign_glue)&&(cur_chr==glue_base+tab_skip_code)) + {@+scan_optional_equals();scan_glue(glue_val); + if (global_defs > 0) geq_define(glue_base+tab_skip_code, glue_ref, cur_val); + else eq_define(glue_base+tab_skip_code, glue_ref, cur_val); + goto restart; + } +} + +@ Spaces are eliminated from the beginning of a template. + +@<Scan the template \<u_j>...@>= +p=hold_head;link(p)=null; +loop@+{@+get_preamble_token(); + if (cur_cmd==mac_param) goto done1; + if ((cur_cmd <= car_ret)&&(cur_cmd >= tab_mark)&&(align_state==-1000000)) + if ((p==hold_head)&&(cur_loop==null)&&(cur_cmd==tab_mark) + ) cur_loop=cur_align; + else{@+print_err("Missing # inserted in alignment preamble"); +@.Missing \# inserted...@> + help3("There should be exactly one # between &'s, when an",@/ + "\\halign or \\valign is being set up. In this case you had",@/ + "none, so I've put one in; maybe that will work."); + back_error();goto done1; + } + else if ((cur_cmd!=spacer)||(p!=hold_head)) + {@+link(p)=get_avail();p=link(p);info(p)=cur_tok; + } + } +done1: + +@ @<Scan the template \<v_j>...@>= +p=hold_head;link(p)=null; +loop@+{@+resume: get_preamble_token(); + if ((cur_cmd <= car_ret)&&(cur_cmd >= tab_mark)&&(align_state==-1000000)) + goto done2; + if (cur_cmd==mac_param) + {@+print_err("Only one # is allowed per tab"); +@.Only one \# is allowed...@> + help3("There should be exactly one # between &'s, when an",@/ + "\\halign or \\valign is being set up. In this case you had",@/ + "more than one, so I'm ignoring all but the first."); + error();goto resume; + } + link(p)=get_avail();p=link(p);info(p)=cur_tok; + } +done2: link(p)=get_avail();p=link(p); +info(p)=end_template_token /*put \.{\\endtemplate} at the end*/ + +@ The tricky part about alignments is getting the templates into the +scanner at the right time, and recovering control when a row or column +is finished. + +We usually begin a row after each \.{\\cr} has been sensed, unless that +\.{\\cr} is followed by \.{\\noalign} or by the right brace that terminates +the alignment. The |align_peek| routine is used to look ahead and do +the right thing; it either gets a new row started, or gets a \.{\\noalign} +started, or finishes off the alignment. + +@<Declare the procedure called |align_peek|@>= +static void align_peek(void) +{@+ +restart: align_state=1000000; +@/do@+{get_x_or_protected(); +}@+ while (!(cur_cmd!=spacer)); +if (cur_cmd==no_align) + {@+scan_left_brace();new_save_level(no_align_group); + if (mode==-vmode) normal_paragraph(); + } +else if (cur_cmd==right_brace) fin_align(); +else if ((cur_cmd==car_ret)&&(cur_chr==cr_cr_code)) + goto restart; /*ignore \.{\\crcr}*/ +else{@+init_row(); /*start a new row*/ + init_col(); /*start a new column and replace what we peeked at*/ + } +} + +@ To start a row (i.e., a `row' that rhymes with `dough' but not with `bough'), +we enter a new semantic level, copy the first tabskip glue, and change +from internal vertical mode to restricted horizontal mode or vice versa. +The |space_factor| and |prev_depth| are not used on this semantic level, +but we clear them to zero just to be tidy. + +@p @t\4@>@<Declare the procedure called |init_span|@>@t@>@/ +static void init_row(void) +{@+push_nest();mode=(-hmode-vmode)-mode; +if (mode==-hmode) space_factor=0;@+else prev_depth=0; +tail_append(new_glue(glue_ptr(preamble))); +subtype(tail)=tab_skip_code+1;@/ +cur_align=link(preamble);cur_tail=cur_head;init_span(cur_align); +} + +@ The parameter to |init_span| is a pointer to the alignrecord where the +next column or group of columns will begin. A new semantic level is +entered, so that the columns will generate a list for subsequent packaging. + +@<Declare the procedure called |init_span|@>= +static void init_span(pointer @!p) +{@+push_nest(); +if (mode==-hmode) space_factor=1000; +else{@+prev_depth=ignore_depth;normal_paragraph(); + } +cur_span=p; +} + +@ When a column begins, we assume that |cur_cmd| is either |omit| or else +the current token should be put back into the input until the \<u_j> +template has been scanned. (Note that |cur_cmd| might be |tab_mark| or +|car_ret|.) We also assume that |align_state| is approximately 1000000 at +this time. We remain in the same mode, and start the template if it is +called for. + +@p static void init_col(void) +{@+extra_info(cur_align)=cur_cmd; +if (cur_cmd==omit) align_state=0; +else{@+back_input();begin_token_list(u_part(cur_align), u_template); + } /*now |align_state==1000000|*/ +} + +@ The scanner sets |align_state| to zero when the \<u_j> template ends. When +a subsequent \.{\\cr} or \.{\\span} or tab mark occurs with |align_state==0|, +the scanner activates the following code, which fires up the \<v_j> template. +We need to remember the |cur_chr|, which is either |cr_cr_code|, |cr_code|, +|span_code|, or a character code, depending on how the column text has ended. + +This part of the program had better not be activated when the preamble +to another alignment is being scanned, or when no alignment preamble is active. + +@<Insert the \(v)\<v_j>...@>= +{@+if ((scanner_status==aligning)||(cur_align==null)) + fatal_error("(interwoven alignment preambles are not allowed)"); +@.interwoven alignment preambles...@> +cur_cmd=extra_info(cur_align);extra_info(cur_align)=cur_chr; +if (cur_cmd==omit) begin_token_list(omit_template, v_template); +else begin_token_list(v_part(cur_align), v_template); +align_state=1000000;goto restart; +} + +@ The token list |omit_template| just referred to is a constant token +list that contains the special control sequence \.{\\endtemplate} only. + +@<Initialize the special...@>= +info(omit_template)=end_template_token; /*|link(omit_template)==null|*/ + +@ When the |endv| command at the end of a \<v_j> template comes through the +scanner, things really start to happen; and it is the |fin_col| routine +that makes them happen. This routine returns |true| if a row as well as a +column has been finished. + +@p static bool fin_col(void) +{@+ +pointer p; /*the alignrecord after the current one*/ +pointer @!q, @!r; /*temporary pointers for list manipulation*/ +pointer @!s; /*a new span node*/ +pointer @!u; /*a new unset box*/ +scaled @!w; /*natural width*/ +glue_ord @!o; /*order of infinity*/ +halfword @!n; /*span counter*/ +if (cur_align==null) confusion("endv"); +q=link(cur_align);@+if (q==null) confusion("endv"); +@:this can't happen endv}{\quad endv@> +if (align_state < 500000) + fatal_error("(interwoven alignment preambles are not allowed)"); +@.interwoven alignment preambles...@> +p=link(q); +@<If the preamble list has been traversed, check that the row has ended@>; +if (extra_info(cur_align)!=span_code) + {@+unsave();new_save_level(align_group);@/ + @<Package an unset box for the current column and record its width@>; + @<Copy the tabskip glue between columns@>; + if (extra_info(cur_align) >= cr_code) + {@+return true; + } + init_span(p); + } +align_state=1000000; +@/do@+{get_x_or_protected(); +}@+ while (!(cur_cmd!=spacer)); +cur_align=p; +init_col();return false; +} + +@ @<If the preamble list has been traversed, check that the row has ended@>= +if ((p==null)&&(extra_info(cur_align) < cr_code)) + if (cur_loop!=null) @<Lengthen the preamble periodically@>@; + else{@+print_err("Extra alignment tab has been changed to "); +@.Extra alignment tab...@> + print_esc("cr"); + help3("You have given more \\span or & marks than there were",@/ + "in the preamble to the \\halign or \\valign now in progress.",@/ + "So I'll assume that you meant to type \\cr instead."); + extra_info(cur_align)=cr_code;error(); + } + +@ @<Lengthen the preamble...@>= +{@+link(q)=new_null_box();p=link(q); /*a new alignrecord*/ +info(p)=end_span;width(p)=null_flag;cur_loop=link(cur_loop); +@<Copy the templates from node |cur_loop| into node |p|@>; +cur_loop=link(cur_loop); +link(p)=new_glue(glue_ptr(cur_loop)); +subtype(link(p))=tab_skip_code+1; +} + +@ @<Copy the templates from node |cur_loop| into node |p|@>= +q=hold_head;r=u_part(cur_loop); +while (r!=null) + {@+link(q)=get_avail();q=link(q);info(q)=info(r);r=link(r); + } +link(q)=null;u_part(p)=link(hold_head); +q=hold_head;r=v_part(cur_loop); +while (r!=null) + {@+link(q)=get_avail();q=link(q);info(q)=info(r);r=link(r); + } +link(q)=null;v_part(p)=link(hold_head) + +@ @<Copy the tabskip glue...@>= +tail_append(new_glue(glue_ptr(link(cur_align)))); +subtype(tail)=tab_skip_code+1 + +@ @<Package an unset...@>= +{@+if (mode==-hmode) + {@+adjust_tail=cur_tail;u=hpack(link(head), natural);w=width(u); + cur_tail=adjust_tail;adjust_tail=null; + } +else{@+u=vpackage(link(head), natural, 0);w=height(u); + } +n=min_quarterword; /*this represents a span count of 1*/ +if (cur_span!=cur_align) @<Update width entry for spanned columns@>@; +else if (w > width(cur_align)) width(cur_align)=w; +type(u)=unset_node;span_count(u)=n;@/ +@<Determine the stretch order@>; +glue_order(u)=o;glue_stretch(u)=total_stretch[o];@/ +@<Determine the shrink order@>; +glue_sign(u)=o;glue_shrink(u)=total_shrink[o];@/ +pop_nest();link(tail)=u;tail=u; +} + +@ A span node is a 2-word record containing |width|, |info|, and |link| +fields. The |link| field is not really a link, it indicates the number of +spanned columns; the |info| field points to a span node for the same +starting column, having a greater extent of spanning, or to |end_span|, +which has the largest possible |link| field; the |width| field holds the +largest natural width corresponding to a particular set of spanned columns. + +A list of the maximum widths so far, for spanned columns starting at a +given column, begins with the |info| field of the alignrecord for that +column. + +@d span_node_size 2 /*number of |mem| words for a span node*/ + +@<Initialize the special list heads...@>= +link(end_span)=max_quarterword+1;info(end_span)=null; + +@ @<Update width entry for spanned columns@>= +{@+q=cur_span; +@/do@+{incr(n);q=link(link(q)); +}@+ while (!(q==cur_align)); +if (n > max_quarterword) confusion("256 spans"); /*this can happen, but won't*/ +@^system dependencies@> +@:this can't happen 256 spans}{\quad 256 spans@> +q=cur_span;while (link(info(q)) < n) q=info(q); +if (link(info(q)) > n) + {@+s=get_node(span_node_size);info(s)=info(q);link(s)=n; + info(q)=s;width(s)=w; + } +else if (width(info(q)) < w) width(info(q))=w; +} + +@ At the end of a row, we append an unset box to the current vlist (for +\.{\\halign}) or the current hlist (for \.{\\valign}). This unset box +contains the unset boxes for the columns, separated by the tabskip glue. +Everything will be set later. + +@p static void fin_row(void) +{@+pointer p; /*the new unset box*/ +if (mode==-hmode) + {@+p=hpack(link(head), natural); + pop_nest();append_to_vlist(p); + if (cur_head!=cur_tail) + {@+link(tail)=link(cur_head);tail=cur_tail; + } + } +else{@+p=vpack(link(head), natural);pop_nest(); + link(tail)=p;tail=p;space_factor=1000; + } +type(p)=unset_node;glue_stretch(p)=0; +if (every_cr!=null) begin_token_list(every_cr, every_cr_text); +align_peek(); +} /*note that |glue_shrink(p)==0| since |glue_shrink====shift_amount|*/ + +@ Finally, we will reach the end of the alignment, and we can breathe a +sigh of relief that memory hasn't overflowed. All the unset boxes will now be +set so that the columns line up, taking due account of spanned columns. + +@p static void do_assignments(void);@/ +static void resume_after_display(void);@/ +static void build_page(void);@/ +static void fin_align(void) +{@+pointer @!p, @!q, @!r, @!s, @!u, @!v; /*registers for the list operations*/ +scaled @!t, @!w; /*width of column*/ +scaled @!o; /*shift offset for unset boxes*/ +halfword @!n; /*matching span amount*/ +scaled @!rule_save; /*temporary storage for |overfull_rule|*/ +memory_word @!aux_save; /*temporary storage for |aux|*/ +if (cur_group!=align_group) confusion("align1"); +@:this can't happen align}{\quad align@> +unsave(); /*that |align_group| was for individual entries*/ +if (cur_group!=align_group) confusion("align0"); +unsave(); /*that |align_group| was for the whole alignment*/ +if (nest[nest_ptr-1].mode_field==mmode) o=display_indent; + else o=0; +@<Go through the preamble list, determining the column widths and changing +the alignrecords to dummy unset boxes@>; +@<Package the preamble list, to determine the actual tabskip glue amounts, +and let |p| point to this prototype box@>; +@<Set the glue in all the unset boxes of the current list@>; +flush_node_list(p);pop_alignment(); +@<Insert the \(c)current list into its environment@>; +} @/ +@t\4@>@<Declare the procedure called |align_peek|@>@; + +@ It's time now to dismantle the preamble list and to compute the column +widths. Let $w_{ij}$ be the maximum of the natural widths of all entries +that span columns $i$ through $j$, inclusive. The alignrecord for column~$i$ +contains $w_{ii}$ in its |width| field, and there is also a linked list of +the nonzero $w_{ij}$ for increasing $j$, accessible via the |info| field; +these span nodes contain the value $j-i+|min_quarterword|$ in their +|link| fields. The values of $w_{ii}$ were initialized to |null_flag|, which +we regard as $-\infty$. + +The final column widths are defined by the formula +$$w_j=\max_{1\le i\le j}\biggl( w_{ij}-\sum_{i\le k<j}(t_k+w_k)\biggr),$$ +where $t_k$ is the natural width of the tabskip glue between columns +$k$ and~$k+1$. However, if $w_{ij}=-\infty$ for all |i| in the range +|1 <= i <= j| (i.e., if every entry that involved column~|j| also involved +column~|j+1|), we let $w_j=0$, and we zero out the tabskip glue after +column~|j|. + +\TeX\ computes these values by using the following scheme: First $w_1=w_{11}$. +Then replace $w_{2j}$ by $\max(w_{2j},w_{1j}-t_1-w_1)$, for all $j>1$. +Then $w_2=w_{22}$. Then replace $w_{3j}$ by $\max(w_{3j},w_{2j}-t_2-w_2)$ +for all $j>2$; and so on. If any $w_j$ turns out to be $-\infty$, its +value is changed to zero and so is the next tabskip. + +@<Go through the preamble list,...@>= +q=link(preamble); +@/do@+{flush_list(u_part(q));flush_list(v_part(q)); +p=link(link(q)); +if (width(q)==null_flag) + @<Nullify |width(q)| and the tabskip glue following this column@>; +if (info(q)!=end_span) + @<Merge the widths in the span nodes of |q| with those of |p|, destroying +the span nodes of |q|@>; +type(q)=unset_node;span_count(q)=min_quarterword;height(q)=0; +depth(q)=0;glue_order(q)=normal;glue_sign(q)=normal; +glue_stretch(q)=0;glue_shrink(q)=0;q=p; +}@+ while (!(q==null)) + +@ @<Nullify |width(q)| and the tabskip glue following this column@>= +{@+width(q)=0;r=link(q);s=glue_ptr(r); +if (s!=zero_glue) + {@+add_glue_ref(zero_glue);delete_glue_ref(s); + glue_ptr(r)=zero_glue; + } +} + +@ Merging of two span-node lists is a typical exercise in the manipulation of +linearly linked data structures. The essential invariant in the following +|@/do@+{| loop is that we want to dispense with node |r|, in |q|'s list, +and |u| is its successor; all nodes of |p|'s list up to and including |s| +have been processed, and the successor of |s| matches |r| or precedes |r| +or follows |r|, according as |link(r)==n| or |link(r) > n| or |link(r) < n|. + +@<Merge the widths...@>= +{@+t=width(q)+width(glue_ptr(link(q))); +r=info(q);s=end_span;info(s)=p;n=min_quarterword+1; +@/do@+{width(r)=width(r)-t;u=info(r); +while (link(r) > n) + {@+s=info(s);n=link(info(s))+1; + } +if (link(r) < n) + {@+info(r)=info(s);info(s)=r;decr(link(r));s=r; + } +else{@+if (width(r) > width(info(s))) width(info(s))=width(r); + free_node(r, span_node_size); + } +r=u; +}@+ while (!(r==end_span)); +} + +@ Now the preamble list has been converted to a list of alternating unset +boxes and tabskip glue, where the box widths are equal to the final +column sizes. In case of \.{\\valign}, we change the widths to heights, +so that a correct error message will be produced if the alignment is +overfull or underfull. + +@<Package the preamble list...@>= +save_ptr=save_ptr-2;pack_begin_line=-mode_line; +if (mode==-vmode) + {@+rule_save=overfull_rule; + overfull_rule=0; /*prevent rule from being packaged*/ + p=hpack(preamble, saved(1), saved(0));overfull_rule=rule_save; + } +else{@+q=link(preamble); + @/do@+{height(q)=width(q);width(q)=0;q=link(link(q)); + }@+ while (!(q==null)); + p=vpack(preamble, saved(1), saved(0)); + q=link(preamble); + @/do@+{width(q)=height(q);height(q)=0;q=link(link(q)); + }@+ while (!(q==null)); + } +pack_begin_line=0 + +@ @<Set the glue in all the unset...@>= +q=link(head);s=head; +while (q!=null) + {@+if (!is_char_node(q)) + if (type(q)==unset_node) + @<Set the unset box |q| and the unset boxes in it@>@; + else if (type(q)==rule_node) + @<Make the running dimensions in rule |q| extend to the boundaries of +the alignment@>; + s=q;q=link(q); + } + +@ @<Make the running dimensions in rule |q| extend...@>= +{@+if (is_running(width(q))) width(q)=width(p); +if (is_running(height(q))) height(q)=height(p); +if (is_running(depth(q))) depth(q)=depth(p); +if (o!=0) + {@+r=link(q);link(q)=null;q=hpack(q, natural); + shift_amount(q)=o;link(q)=r;link(s)=q; + } +} + +@ The unset box |q| represents a row that contains one or more unset boxes, +depending on how soon \.{\\cr} occurred in that row. + +@<Set the unset box |q| and the unset boxes in it@>= +{@+if (mode==-vmode) + {@+type(q)=hlist_node;width(q)=width(p); + } +else{@+type(q)=vlist_node;height(q)=height(p); + } +glue_order(q)=glue_order(p);glue_sign(q)=glue_sign(p); +glue_set(q)=glue_set(p);shift_amount(q)=o; +r=link(list_ptr(q));s=link(list_ptr(p)); +@/do@+{@<Set the glue in node |r| and change it from an unset node@>; +r=link(link(r));s=link(link(s)); +}@+ while (!(r==null)); +} + +@ A box made from spanned columns will be followed by tabskip glue nodes and +by empty boxes as if there were no spanning. This permits perfect alignment +of subsequent entries, and it prevents values that depend on floating point +arithmetic from entering into the dimensions of any boxes. + +@<Set the glue in node |r|...@>= +n=span_count(r);t=width(s);w=t;u=hold_head; +while (n > min_quarterword) + {@+decr(n); + @<Append tabskip glue and an empty box to list |u|, and update |s| and |t| +as the prototype nodes are passed@>; + } +if (mode==-vmode) + @<Make the unset node |r| into an |hlist_node| of width |w|, setting the +glue as if the width were |t|@>@; +else@<Make the unset node |r| into a |vlist_node| of height |w|, setting the +glue as if the height were |t|@>; +shift_amount(r)=0; +if (u!=hold_head) /*append blank boxes to account for spanned nodes*/ + {@+link(u)=link(r);link(r)=link(hold_head);r=u; + } + +@ @<Append tabskip glue and an empty box to list |u|...@>= +s=link(s);v=glue_ptr(s);link(u)=new_glue(v);u=link(u); +subtype(u)=tab_skip_code+1;t=t+width(v); +if (glue_sign(p)==stretching) + {@+if (stretch_order(v)==glue_order(p)) + t=t+round(unfix(glue_set(p))*stretch(v)); +@^real multiplication@> + } +else if (glue_sign(p)==shrinking) + {@+if (shrink_order(v)==glue_order(p)) + t=t-round(unfix(glue_set(p))*shrink(v)); + } +s=link(s);link(u)=new_null_box();u=link(u);t=t+width(s); +if (mode==-vmode) width(u)=width(s);@+else + {@+type(u)=vlist_node;height(u)=width(s); + } + +@ @<Make the unset node |r| into an |hlist_node| of width |w|...@>= +{@+height(r)=height(q);depth(r)=depth(q); +if (t==width(r)) + {@+glue_sign(r)=normal;glue_order(r)=normal; + set_glue_ratio_zero(glue_set(r)); + } +else if (t > width(r)) + {@+glue_sign(r)=stretching; + if (glue_stretch(r)==0) set_glue_ratio_zero(glue_set(r)); + else glue_set(r)=fix((t-width(r))/(double)glue_stretch(r)); +@^real division@> + } +else{@+glue_order(r)=glue_sign(r);glue_sign(r)=shrinking; + if (glue_shrink(r)==0) set_glue_ratio_zero(glue_set(r)); + else if ((glue_order(r)==normal)&&(width(r)-t > glue_shrink(r))) + set_glue_ratio_one(glue_set(r)); + else glue_set(r)=fix((width(r)-t)/(double)glue_shrink(r)); + } +width(r)=w;type(r)=hlist_node; +} + +@ @<Make the unset node |r| into a |vlist_node| of height |w|...@>= +{@+width(r)=width(q); +if (t==height(r)) + {@+glue_sign(r)=normal;glue_order(r)=normal; + set_glue_ratio_zero(glue_set(r)); + } +else if (t > height(r)) + {@+glue_sign(r)=stretching; + if (glue_stretch(r)==0) set_glue_ratio_zero(glue_set(r)); + else glue_set(r)=fix((t-height(r))/(double)glue_stretch(r)); +@^real division@> + } +else{@+glue_order(r)=glue_sign(r);glue_sign(r)=shrinking; + if (glue_shrink(r)==0) set_glue_ratio_zero(glue_set(r)); + else if ((glue_order(r)==normal)&&(height(r)-t > glue_shrink(r))) + set_glue_ratio_one(glue_set(r)); + else glue_set(r)=fix((height(r)-t)/(double)glue_shrink(r)); + } +height(r)=w;type(r)=vlist_node; +} + +@ We now have a completed alignment, in the list that starts at |head| +and ends at |tail|. This list will be merged with the one that encloses +it. (In case the enclosing mode is |mmode|, for displayed formulas, +we will need to insert glue before and after the display; that part of the +program will be deferred until we're more familiar with such operations.) + +In restricted horizontal mode, the |clang| part of |aux| is undefined; +an over-cautious \PASCAL\ runtime system may complain about this. +@^dirty \PASCAL@> + +@<Insert the \(c)current list into its environment@>= +aux_save=aux;p=link(head);q=tail;pop_nest(); +if (mode==mmode) @<Finish an alignment in a display@>@; +else{@+aux=aux_save;link(tail)=p; + if (p!=null) tail=q; + if (mode==vmode) build_page(); + } + +@* Breaking paragraphs into lines. +We come now to what is probably the most interesting algorithm of \TeX: +the mechanism for choosing the ``best possible'' breakpoints that yield +the individual lines of a paragraph. \TeX's line-breaking algorithm takes +a given horizontal list and converts it to a sequence of boxes that are +appended to the current vertical list. In the course of doing this, it +creates a special data structure containing three kinds of records that are +not used elsewhere in \TeX. Such nodes are created while a paragraph is +being processed, and they are destroyed afterwards; thus, the other parts +of \TeX\ do not need to know anything about how line-breaking is done. + +The method used here is based on an approach devised by Michael F. Plass and +@^Plass, Michael Frederick@> +@^Knuth, Donald Ervin@> +the author in 1977, subsequently generalized and improved by the same two +people in 1980. A detailed discussion appears in {\sl Software---Practice +and Experience \bf11} (1981), 1119--1184, where it is shown that the +line-breaking problem can be regarded as a special case of the problem of +computing the shortest path in an acyclic network. The cited paper includes +numerous examples and describes the history of line breaking as it has been +practiced by printers through the ages. The present implementation adds two +new ideas to the algorithm of 1980: Memory space requirements are considerably +reduced by using smaller records for inactive nodes than for active ones, +and arithmetic overflow is avoided by using ``delta distances'' instead of +keeping track of the total distance from the beginning of the paragraph to the +current point. + +@ The |line_break| procedure should be invoked only in horizontal mode; it +leaves that mode and places its output into the current vlist of the +enclosing vertical mode (or internal vertical mode). +There is one explicit parameter: |final_widow_penalty| is the amount of +additional penalty to be inserted before the final line of the paragraph. + +There are also a number of implicit parameters: The hlist to be broken +starts at |link(head)|, and it is nonempty. The value of |prev_graf| in the +enclosing semantic level tells where the paragraph should begin in the +sequence of line numbers, in case hanging indentation or \.{\\parshape} +is in use; |prev_graf| is zero unless this paragraph is being continued +after a displayed formula. Other implicit parameters, such as the +|par_shape_ptr| and various penalties to use for hyphenation, etc., appear +in |eqtb|. + +After |line_break| has acted, it will have updated the current vlist and the +value of |prev_graf|. Furthermore, the global variable |just_box| will +point to the final box created by |line_break|, so that the width of this +line can be ascertained when it is necessary to decide whether to use +|above_display_skip| or |above_display_short_skip| before a displayed formula. + +@<Glob...@>= +static pointer @!just_box; /*the |hlist_node| for the last line of the new paragraph*/ + +@ Since |line_break| is a rather lengthy procedure---sort of a small world unto +itself---we must build it up little by little, somewhat more cautiously +than we have done with the simpler procedures of \TeX. Here is the +general outline. + +@p @t\4@>@<Declare subprocedures for |line_break|@>@; +static void line_break(int @!final_widow_penalty) +{@+ +@<Local variables for line breaking@>@; +@<Local variables to save the profiling context@>@; +@<Charge the time used here on |line_break|@>@; +pack_begin_line=mode_line; /*this is for over/underfull box messages*/ +@<Get ready to start line breaking@>; +@<Find optimal breakpoints@>; +@<Break the paragraph at the chosen breakpoints, justify the resulting lines +to the correct widths, and append them to the current vertical list@>; +@<Clean up the memory by removing the break nodes@>; +pack_begin_line=0; +@<restore the previous current file, line, and command@>@; +} +@# +@t\4@>@<Declare \eTeX\ procedures for use by |main_control|@>@; + +@ The first task is to move the list from |head| to |temp_head| and go +into the enclosing semantic level. We also append the \.{\\parfillskip} +glue to the end of the paragraph, removing a space (or other glue node) if +it was there, since spaces usually precede blank lines and instances of +`\.{\$\$}'. The |par_fill_skip| is preceded by an infinite penalty, so +it will never be considered as a potential breakpoint. + +This code assumes that a |glue_node| and a |penalty_node| occupy the +same number of |mem|~words. +@^data structure assumptions@> + +@<Get ready to start...@>= +link(temp_head)=link(head); +if (is_char_node(tail)) tail_append(new_penalty(inf_penalty))@; +else if (type(tail)!=glue_node) tail_append(new_penalty(inf_penalty))@; +else{@+type(tail)=penalty_node;delete_glue_ref(glue_ptr(tail)); + flush_node_list(leader_ptr(tail));penalty(tail)=inf_penalty; + } +link(tail)=new_param_glue(par_fill_skip_code); +init_cur_lang=prev_graf%0200000; +init_l_hyf=prev_graf/020000000; +init_r_hyf=(prev_graf/0200000)%0100; +pop_nest(); + +@ When looking for optimal line breaks, \TeX\ creates a ``break node'' for +each break that is {\sl feasible}, in the sense that there is a way to end +a line at the given place without requiring any line to stretch more than +a given tolerance. A break node is characterized by three things: the position +of the break (which is a pointer to a |glue_node|, |math_node|, |penalty_node|, +or |disc_node|); the ordinal number of the line that will follow this +breakpoint; and the fitness classification of the line that has just +ended, i.e., |tight_fit|, |decent_fit|, |loose_fit|, or |very_loose_fit|. + +@d tight_fit 3 /*fitness classification for lines shrinking 0.5 to 1.0 of their + shrinkability*/ +@d loose_fit 1 /*fitness classification for lines stretching 0.5 to 1.0 of their + stretchability*/ +@d very_loose_fit 0 /*fitness classification for lines stretching more than + their stretchability*/ +@d decent_fit 2 /*fitness classification for all other lines*/ + +@ The algorithm essentially determines the best possible way to achieve +each feasible combination of position, line, and fitness. Thus, it answers +questions like, ``What is the best way to break the opening part of the +paragraph so that the fourth line is a tight line ending at such-and-such +a place?'' However, the fact that all lines are to be the same length +after a certain point makes it possible to regard all sufficiently large +line numbers as equivalent, when the looseness parameter is zero, and this +makes it possible for the algorithm to save space and time. + +An ``active node'' and a ``passive node'' are created in |mem| for each +feasible breakpoint that needs to be considered. Active nodes are three +words long and passive nodes are two words long. We need active nodes only +for breakpoints near the place in the paragraph that is currently being +examined, so they are recycled within a comparatively short time after +they are created. + +@ An active node for a given breakpoint contains six fields: + +\yskip\hang|link| points to the next node in the list of active nodes; the +last active node has |link==last_active|. + +\yskip\hang|break_node| points to the passive node associated with this +breakpoint. + +\yskip\hang|line_number| is the number of the line that follows this +breakpoint. + +\yskip\hang|fitness| is the fitness classification of the line ending at this +breakpoint. + +\yskip\hang|type| is either |hyphenated| or |unhyphenated|, depending on +whether this breakpoint is a |disc_node|. + +\yskip\hang|total_demerits| is the minimum possible sum of demerits over all +lines leading from the beginning of the paragraph to this breakpoint. + +\yskip\noindent +The value of |link(active)| points to the first active node on a linked list +of all currently active nodes. This list is in order by |line_number|, +except that nodes with |line_number > easy_line| may be in any order relative +to each other. + +@d active_node_size 3 /*number of words in active nodes*/ +@d fitness(A) subtype(A) /*|very_loose_fit dotdot tight_fit| on final line for this break*/ +@d break_node(A) rlink(A) /*pointer to the corresponding passive node*/ +@d line_number(A) llink(A) /*line that begins at this breakpoint*/ +@d total_demerits(A) mem[A+2].i /*the quantity that \TeX\ minimizes*/ +@d unhyphenated 0 /*the |type| of a normal active break node*/ +@d hyphenated 1 /*the |type| of an active node that breaks at a |disc_node|*/ +@d last_active active /*the active list ends where it begins*/ + +@ @<Initialize the special list heads...@>= +type(last_active)=hyphenated;line_number(last_active)=max_halfword; +subtype(last_active)=0; /*the |subtype| is never examined by the algorithm*/ + +@ The passive node for a given breakpoint contains only four fields: + +\yskip\hang|link| points to the passive node created just before this one, +if any, otherwise it is |null|. + +\yskip\hang|cur_break| points to the position of this breakpoint in the +horizontal list for the paragraph being broken. + +\yskip\hang|prev_break| points to the passive node that should precede this +one in an optimal path to this breakpoint. + +\yskip\hang|serial| is equal to |n| if this passive node is the |n|th +one created during the current pass. (This field is used only when +printing out detailed statistics about the line-breaking calculations.) + +\yskip\noindent +There is a global variable called |passive| that points to the most +recently created passive node. Another global variable, |printed_node|, +is used to help print out the paragraph when detailed information about +the line-breaking computation is being displayed. + +@d passive_node_size 2 /*number of words in passive nodes*/ +@d cur_break(A) rlink(A) /*in passive node, points to position of this breakpoint*/ +@d prev_break(A) llink(A) /*points to passive node that should precede this one*/ +@d serial(A) info(A) /*serial number for symbolic identification*/ + +@<Glob...@>= +static pointer @!passive; /*most recent node on passive list*/ +static pointer @!printed_node; /*most recent node that has been printed*/ +static halfword @!pass_number; /*the number of passive nodes allocated on this pass*/ + +@ The active list also contains ``delta'' nodes that help the algorithm +compute the badness of individual lines. Such nodes appear only between two +active nodes, and they have |type==delta_node|. If |p| and |r| are active nodes +and if |q| is a delta node between them, so that |link(p)==q| and |link(q)==r|, +then |q| tells the space difference between lines in the horizontal list that +start after breakpoint |p| and lines that start after breakpoint |r|. In +other words, if we know the length of the line that starts after |p| and +ends at our current position, then the corresponding length of the line that +starts after |r| is obtained by adding the amounts in node~|q|. A delta node +contains six scaled numbers, since it must record the net change in glue +stretchability with respect to all orders of infinity. The natural width +difference appears in |mem[q+1].sc|; the stretch differences in units of +pt, fil, fill, and filll appear in |mem[q+2 dotdot q+5].sc|; and the shrink difference +appears in |mem[q+6].sc|. The |subtype| field of a delta node is not used. + +@d delta_node_size 7 /*number of words in a delta node*/ +@d delta_node 2 /*|type| field in a delta node*/ + +@ As the algorithm runs, it maintains a set of six delta-like registers +for the length of the line following the first active breakpoint to the +current position in the given hlist. When it makes a pass through the +active list, it also maintains a similar set of six registers for the +length following the active breakpoint of current interest. A third set +holds the length of an empty line (namely, the sum of \.{\\leftskip} and +\.{\\rightskip}); and a fourth set is used to create new delta nodes. + +When we pass a delta node we want to do operations like +$$\hbox{\ignorespaces|for +k=1 to 6 do cur_active_width[k]=cur_active_width[k]+mem[q+k].sc|};$$ and we +want to do this without the overhead of |for| loops. The |do_all_six| +macro makes such six-tuples convenient. + +@d do_all_six(A) A(1);A(2);A(3);A(4);A(5);A(6) + +@<Glob...@>= +static scaled @!active_width0[6], *const @!active_width = @!active_width0-1; + /*distance from first active node to~|cur_p|*/ +static scaled @!cur_active_width0[6], + *const @!cur_active_width = @!cur_active_width0-1; /*distance from current active node*/ +static scaled @!background0[6], *const @!background = @!background0-1; /*length of an ``empty'' line*/ +static scaled @!break_width0[6], *const @!break_width = @!break_width0-1; /*length being computed after current break*/ + +@ Let's state the principles of the delta nodes more precisely and concisely, +so that the following programs will be less obscure. For each legal +breakpoint~|p| in the paragraph, we define two quantities $\alpha(p)$ and +$\beta(p)$ such that the length of material in a line from breakpoint~|p| +to breakpoint~|q| is $\gamma+\beta(q)-\alpha(p)$, for some fixed $\gamma$. +Intuitively, $\alpha(p)$ and $\beta(q)$ are the total length of material from +the beginning of the paragraph to a point ``after'' a break at |p| and to a +point ``before'' a break at |q|; and $\gamma$ is the width of an empty line, +namely the length contributed by \.{\\leftskip} and \.{\\rightskip}. + +Suppose, for example, that the paragraph consists entirely of alternating +boxes and glue skips; let the boxes have widths $x_1\ldots x_n$ and +let the skips have widths $y_1\ldots y_n$, so that the paragraph can be +represented by $x_1y_1\ldots x_ny_n$. Let $p_i$ be the legal breakpoint +at $y_i$; then $\alpha(p_i)=x_1+y_1+\cdots+x_i+y_i$, and $\beta(p_i)= +x_1+y_1+\cdots+x_i$. To check this, note that the length of material from +$p_2$ to $p_5$, say, is $\gamma+x_3+y_3+x_4+y_4+x_5=\gamma+\beta(p_5) +-\alpha(p_2)$. + +The quantities $\alpha$, $\beta$, $\gamma$ involve glue stretchability and +shrinkability as well as a natural width. If we were to compute $\alpha(p)$ +and $\beta(p)$ for each |p|, we would need multiple precision arithmetic, and +the multiprecise numbers would have to be kept in the active nodes. +\TeX\ avoids this problem by working entirely with relative differences +or ``deltas.'' Suppose, for example, that the active list contains +$a_1\,\delta_1\,a_2\,\delta_2\,a_3$, where the |a|'s are active breakpoints +and the $\delta$'s are delta nodes. Then $\delta_1=\alpha(a_1)-\alpha(a_2)$ +and $\delta_2=\alpha(a_2)-\alpha(a_3)$. If the line breaking algorithm is +currently positioned at some other breakpoint |p|, the |active_width| array +contains the value $\gamma+\beta(p)-\alpha(a_1)$. If we are scanning through +the list of active nodes and considering a tentative line that runs from +$a_2$ to~|p|, say, the |cur_active_width| array will contain the value +$\gamma+\beta(p)-\alpha(a_2)$. Thus, when we move from $a_2$ to $a_3$, +we want to add $\alpha(a_2)-\alpha(a_3)$ to |cur_active_width|; and this +is just $\delta_2$, which appears in the active list between $a_2$ and +$a_3$. The |background| array contains $\gamma$. The |break_width| array +will be used to calculate values of new delta nodes when the active +list is being updated. + +@ Glue nodes in a horizontal list that is being paragraphed are not supposed to +include ``infinite'' shrinkability; that is why the algorithm maintains +four registers for stretching but only one for shrinking. If the user tries to +introduce infinite shrinkability, the shrinkability will be reset to finite +and an error message will be issued. A boolean variable |no_shrink_error_yet| +prevents this error message from appearing more than once per paragraph. + +@d check_shrinkage(A) if ((shrink_order(A)!=normal)&&(shrink(A)!=0)) + {@+A=finite_shrink(A); + } + +@<Glob...@>= +static bool @!no_shrink_error_yet; /*have we complained about infinite shrinkage?*/ + +@ @<Declare subprocedures for |line_break|@>= +static pointer finite_shrink(pointer @!p) /*recovers from infinite shrinkage*/ +{@+pointer q; /*new glue specification*/ +if (no_shrink_error_yet) + {@+no_shrink_error_yet=false; +#ifdef @!STAT + if (tracing_paragraphs > 0) end_diagnostic(true); +#endif +@; + print_err("Infinite glue shrinkage found in a paragraph"); +@.Infinite glue shrinkage...@> + help5("The paragraph just ended includes some glue that has",@/ + "infinite shrinkability, e.g., `\\hskip 0pt minus 1fil'.",@/ + "Such glue doesn't belong there---it allows a paragraph",@/ + "of any length to fit on one line. But it's safe to proceed,",@/ + "since the offensive shrinkability has been made finite."); + error(); +#ifdef @!STAT + if (tracing_paragraphs > 0) begin_diagnostic(); +#endif +@; + } +q=new_spec(p);shrink_order(q)=normal; +delete_glue_ref(p);return q; +} + +@ @<Get ready to start...@>= +no_shrink_error_yet=true;@/ +check_shrinkage(left_skip);check_shrinkage(right_skip);@/ +q=left_skip;r=right_skip;background[1]=width(q)+width(r);@/ +background[2]=0;background[3]=0;background[4]=0;background[5]=0;@/ +background[2+stretch_order(q)]=stretch(q);@/ +background[2+stretch_order(r)]=@|background[2+stretch_order(r)]+stretch(r);@/ +background[6]=shrink(q)+shrink(r); + +@ A pointer variable |cur_p| runs through the given horizontal list as we look +for breakpoints. This variable is global, since it is used both by |line_break| +and by its subprocedure |try_break|. + +Another global variable called |threshold| is used to determine the feasibility +of individual lines: Breakpoints are feasible if there is a way to reach +them without creating lines whose badness exceeds |threshold|. (The +badness is compared to |threshold| before penalties are added, so that +penalty values do not affect the feasibility of breakpoints, except that +no break is allowed when the penalty is 10000 or more.) If |threshold| +is 10000 or more, all legal breaks are considered feasible, since the +|badness| function specified above never returns a value greater than~10000. + +Up to three passes might be made through the paragraph in an attempt to find at +least one set of feasible breakpoints. On the first pass, we have +|threshold==pretolerance| and |second_pass==final_pass==false|. +If this pass fails to find a +feasible solution, |threshold| is set to |tolerance|, |second_pass| is set +|true|, and an attempt is made to hyphenate as many words as possible. +If that fails too, we add |emergency_stretch| to the background +stretchability and set |final_pass==true|. + +@<Glob...@>= +static pointer @!cur_p; /*the current breakpoint under consideration*/ +static bool @!second_pass; /*is this our second attempt to break this paragraph?*/ +static bool @!final_pass; /*is this our final attempt to break this paragraph?*/ +static int @!threshold; /*maximum badness on feasible lines*/ + +@ The heart of the line-breaking procedure is `|try_break|', a subroutine +that tests if the current breakpoint |cur_p| is feasible, by running +through the active list to see what lines of text can be made from active +nodes to~|cur_p|. If feasible breaks are possible, new break nodes are +created. If |cur_p| is too far from an active node, that node is +deactivated. + +The parameter |pi| to |try_break| is the penalty associated +with a break at |cur_p|; we have |pi==eject_penalty| if the break is forced, +and |pi==inf_penalty| if the break is illegal. + +The other parameter, |break_type|, is set to |hyphenated| or |unhyphenated|, +depending on whether or not the current break is at a |disc_node|. The +end of a paragraph is also regarded as `|hyphenated|'; this case is +distinguishable by the condition |cur_p==null|. + +@d copy_to_cur_active(A) cur_active_width[A]=active_width[A] +@<Declare subprocedures for |line_break|@>= +static void try_break(int @!pi, small_number @!break_type) +{@+ +pointer r; /*runs through the active list*/ +pointer @!prev_r; /*stays a step behind |r|*/ +halfword @!old_l; /*maximum line number in current equivalence class of lines*/ +bool @!no_break_yet; /*have we found a feasible break at |cur_p|?*/ +@<Other local variables for |try_break|@>@; +@<Make sure that |pi| is in the proper range@>; +no_break_yet=true;prev_r=active;old_l=0; +do_all_six(copy_to_cur_active); +loop@+{@+resume: r=link(prev_r); + @<If node |r| is of type |delta_node|, update |cur_active_width|, set |prev_r| +and |prev_prev_r|, then |goto resume|@>; + @<If a line number class has ended, create new active nodes for the best +feasible breaks in that class; then |return| if |r=last_active|, otherwise +compute the new |line_width|@>; + @<Consider the demerits for a line from |r| to |cur_p|; deactivate node +|r| if it should no longer be active; then |goto resume| if a line from +|r| to |cur_p| is infeasible, otherwise record a new feasible break@>; + } +end: ; +#ifdef @!STAT +@<Update the value of |printed_node| for symbolic displays@>; +#endif +@; +} + +@ @<Other local variables for |try_break|@>= +pointer @!prev_prev_r; /*a step behind |prev_r|, if |type(prev_r)==delta_node|*/ +pointer @!s; /*runs through nodes ahead of |cur_p|*/ +pointer @!q; /*points to a new node being created*/ +pointer @!v; /*points to a glue specification or a node ahead of |cur_p|*/ +int @!t; /*node count, if |cur_p| is a discretionary node*/ +internal_font_number @!f; /*used in character width calculation*/ +halfword @!l; /*line number of current active node*/ +bool @!node_r_stays_active; /*should node |r| remain in the active list?*/ +scaled @!line_width; /*the current line will be justified to this width*/ +int @!fit_class; /*possible fitness class of test line*/ +halfword @!b; /*badness of test line*/ +int @!d; /*demerits of test line*/ +bool @!artificial_demerits; /*has |d| been forced to zero?*/ +#ifdef @!STAT +pointer @!save_link; /*temporarily holds value of |link(cur_p)|*/ +#endif +scaled @!shortfall; /*used in badness calculations*/ + +@ @<Make sure that |pi| is in the proper range@>= +if (abs(pi) >= inf_penalty) + if (pi > 0) goto end; /*this breakpoint is inhibited by infinite penalty*/ + else pi=eject_penalty /*this breakpoint will be forced*/ + +@ The following code uses the fact that |type(last_active)!=delta_node|. + +@d update_width(A) @| + cur_active_width[A]=cur_active_width[A]+mem[r+A].sc + +@<If node |r|...@>= +@^inner loop@> +if (type(r)==delta_node) + {@+do_all_six(update_width); + prev_prev_r=prev_r;prev_r=r;goto resume; + } + +@ As we consider various ways to end a line at |cur_p|, in a given line number +class, we keep track of the best total demerits known, in an array with +one entry for each of the fitness classifications. For example, +|minimal_demerits[tight_fit]| contains the fewest total demerits of feasible +line breaks ending at |cur_p| with a |tight_fit| line; |best_place[tight_fit]| +points to the passive node for the break before~|cur_p| that achieves such +an optimum; and |best_pl_line[tight_fit]| is the |line_number| field in the +active node corresponding to |best_place[tight_fit]|. When no feasible break +sequence is known, the |minimal_demerits| entries will be equal to +|awful_bad|, which is $2^{30}-1$. Another variable, |minimum_demerits|, +keeps track of the smallest value in the |minimal_demerits| array. + +@d awful_bad 07777777777 /*more than a billion demerits*/ + +@<Global...@>= +static int @!minimal_demerits0[tight_fit-very_loose_fit+1], + *const @!minimal_demerits = @!minimal_demerits0-very_loose_fit; /*best total + demerits known for current line class and position, given the fitness*/ +static int @!minimum_demerits; /*best total demerits known for current line class + and position*/ +static pointer @!best_place0[tight_fit-very_loose_fit+1], + *const @!best_place = @!best_place0-very_loose_fit; /*how to achieve + |minimal_demerits|*/ +static halfword @!best_pl_line0[tight_fit-very_loose_fit+1], + *const @!best_pl_line = @!best_pl_line0-very_loose_fit; /*corresponding + line number*/ + +@ @<Get ready to start...@>= +minimum_demerits=awful_bad; +minimal_demerits[tight_fit]=awful_bad; +minimal_demerits[decent_fit]=awful_bad; +minimal_demerits[loose_fit]=awful_bad; +minimal_demerits[very_loose_fit]=awful_bad; + +@ The first part of the following code is part of \TeX's inner loop, so +we don't want to waste any time. The current active node, namely node |r|, +contains the line number that will be considered next. At the end of the +list we have arranged the data structure so that |r==last_active| and +|line_number(last_active) > old_l|. +@^inner loop@> + +@<If a line number class...@>= +{@+l=line_number(r); +if (l > old_l) + {@+ /*now we are no longer in the inner loop*/ + if ((minimum_demerits < awful_bad)&&@| + ((old_l!=easy_line)||(r==last_active))) + @<Create new active nodes for the best feasible breaks just found@>; + if (r==last_active) goto end; + @<Compute the new line width@>; + } +} + +@ It is not necessary to create new active nodes having |minimal_demerits| +greater than +|minimum_demerits+abs(adj_demerits)|, since such active nodes will never +be chosen in the final paragraph breaks. This observation allows us to +omit a substantial number of feasible breakpoints from further consideration. + +@<Create new active nodes...@>= +{@+if (no_break_yet) @<Compute the values of |break_width|@>; +@<Insert a delta node to prepare for breaks at |cur_p|@>; +if (abs(adj_demerits) >= awful_bad-minimum_demerits) + minimum_demerits=awful_bad-1; +else minimum_demerits=minimum_demerits+abs(adj_demerits); +for (fit_class=very_loose_fit; fit_class<=tight_fit; fit_class++) + {@+if (minimal_demerits[fit_class] <= minimum_demerits) + @<Insert a new active node from |best_place[fit_class]| to |cur_p|@>; + minimal_demerits[fit_class]=awful_bad; + } +minimum_demerits=awful_bad; +@<Insert a delta node to prepare for the next active node@>; +} + +@ When we insert a new active node for a break at |cur_p|, suppose this +new node is to be placed just before active node |a|; then we essentially +want to insert `$\delta\,|cur_p|\,\delta^\prime$' before |a|, where +$\delta=\alpha(a)-\alpha(|cur_p|)$ and $\delta^\prime=\alpha(|cur_p|)-\alpha(a)$ +in the notation explained above. The |cur_active_width| array now holds +$\gamma+\beta(|cur_p|)-\alpha(a)$; so $\delta$ can be obtained by +subtracting |cur_active_width| from the quantity $\gamma+\beta(|cur_p|)- +\alpha(|cur_p|)$. The latter quantity can be regarded as the length of a +line ``from |cur_p| to |cur_p|''; we call it the |break_width| at |cur_p|. + +The |break_width| is usually negative, since it consists of the background +(which is normally zero) minus the width of nodes following~|cur_p| that are +eliminated after a break. If, for example, node |cur_p| is a glue node, the +width of this glue is subtracted from the background; and we also look +ahead to eliminate all subsequent glue and penalty and kern and math +nodes, subtracting their widths as well. + +Kern nodes do not disappear at a line break unless they are |explicit|. + +@d set_break_width_to_background(A) break_width[A]=background[A] + +@<Compute the values of |break...@>= +{@+no_break_yet=false;do_all_six(set_break_width_to_background); +s=cur_p; +if (break_type > unhyphenated) if (cur_p!=null) + @<Compute the discretionary |break_width| values@>; +while (s!=null) + {@+if (is_char_node(s)) goto done; + switch (type(s)) { + case glue_node: @<Subtract glue from |break_width|@>@;@+break; + case penalty_node: do_nothing;@+break; + case math_node: break_width[1]=break_width[1]-width(s);@+break; + case kern_node: if (subtype(s)!=explicit) goto done; + else break_width[1]=break_width[1]-width(s);@+break; + default:goto done; + } @/ + s=link(s); + } +done: ;} + +@ @<Subtract glue from |break...@>= +{@+v=glue_ptr(s);break_width[1]=break_width[1]-width(v); +break_width[2+stretch_order(v)]=break_width[2+stretch_order(v)]-stretch(v); +break_width[6]=break_width[6]-shrink(v); +} + +@ When |cur_p| is a discretionary break, the length of a line ``from |cur_p| to +|cur_p|'' has to be defined properly so that the other calculations work out. +Suppose that the pre-break text at |cur_p| has length $l_0$, the post-break +text has length $l_1$, and the replacement text has length |l|. Suppose +also that |q| is the node following the replacement text. Then length of a +line from |cur_p| to |q| will be computed as $\gamma+\beta(q)-\alpha(|cur_p|)$, +where $\beta(q)=\beta(|cur_p|)-l_0+l$. The actual length will be the background +plus $l_1$, so the length from |cur_p| to |cur_p| should be $\gamma+l_0+l_1-l$. +If the post-break text of the discretionary is empty, a break may also +discard~|q|; in that unusual case we subtract the length of~|q| and any +other nodes that will be discarded after the discretionary break. + +The value of $l_0$ need not be computed, since |line_break| will put +it into the global variable |disc_width| before calling |try_break|. + +@<Glob...@>= +static scaled @!disc_width; /*the length of discretionary material preceding a break*/ + +@ @<Compute the discretionary |break...@>= +{@+t=replace_count(cur_p);v=cur_p;s=post_break(cur_p); +while (t > 0) + {@+decr(t);v=link(v); + @<Subtract the width of node |v| from |break_width|@>; + } +while (s!=null) + {@+@<Add the width of node |s| to |break_width|@>; + s=link(s); + } +break_width[1]=break_width[1]+disc_width; +if (post_break(cur_p)==null) s=link(v); + /*nodes may be discardable after the break*/ +} + +@ Replacement texts and discretionary texts are supposed to contain +only character nodes, kern nodes, ligature nodes, and box or rule nodes. + +@<Subtract the width of node |v|...@>= +if (is_char_node(v)) + {@+f=font(v); + break_width[1]=break_width[1]-char_width(f, char_info(f, character(v))); + } +else switch (type(v)) { + case ligature_node: {@+f=font(lig_char(v));@/ + break_width[1]=@|break_width[1]- + char_width(f, char_info(f, character(lig_char(v)))); + } @+break; + case hlist_node: case vlist_node: case rule_node: + case kern_node: + break_width[1]=break_width[1]-width(v);@+break; + default:confusion("disc1"); +@:this can't happen disc1}{\quad disc1@> + } + +@ @<Add the width of node |s| to |b...@>= +if (is_char_node(s)) + {@+f=font(s); + break_width[1]=@|break_width[1]+char_width(f, char_info(f, character(s))); + } +else switch (type(s)) { + case ligature_node: {@+f=font(lig_char(s)); + break_width[1]=break_width[1]+ + char_width(f, char_info(f, character(lig_char(s)))); + } @+break; + case hlist_node: case vlist_node: case rule_node: + case kern_node: + break_width[1]=break_width[1]+width(s);@+break; + default:confusion("disc2"); +@:this can't happen disc2}{\quad disc2@> + } + +@ We use the fact that |type(active)!=delta_node|. + +@d convert_to_break_width(A) @| + mem[prev_r+A].sc=@|@t\hskip10pt@>mem[prev_r+A].sc + -cur_active_width[A]+break_width[A] +@d store_break_width(A) active_width[A]=break_width[A] +@d new_delta_to_break_width(A) @| + mem[q+A].sc=break_width[A]-cur_active_width[A] + +@<Insert a delta node to prepare for breaks at |cur_p|@>= +if (type(prev_r)==delta_node) /*modify an existing delta node*/ + {@+do_all_six(convert_to_break_width); + } +else if (prev_r==active) /*no delta node needed at the beginning*/ + {@+do_all_six(store_break_width); + } +else{@+q=get_node(delta_node_size);link(q)=r;type(q)=delta_node;@/ + subtype(q)=0; /*the |subtype| is not used*/ + do_all_six(new_delta_to_break_width); + link(prev_r)=q;prev_prev_r=prev_r;prev_r=q; + } + +@ When the following code is performed, we will have just inserted at +least one active node before |r|, so |type(prev_r)!=delta_node|. + +@d new_delta_from_break_width(A) @|mem[q+A].sc= + cur_active_width[A]-break_width[A] + +@<Insert a delta node to prepare for the next active node@>= +if (r!=last_active) + {@+q=get_node(delta_node_size);link(q)=r;type(q)=delta_node;@/ + subtype(q)=0; /*the |subtype| is not used*/ + do_all_six(new_delta_from_break_width); + link(prev_r)=q;prev_prev_r=prev_r;prev_r=q; + } + +@ When we create an active node, we also create the corresponding +passive node. + +@<Insert a new active node from |best_place[fit_class]| to |cur_p|@>= +{@+q=get_node(passive_node_size); +link(q)=passive;passive=q;cur_break(q)=cur_p; +#ifdef @!STAT +incr(pass_number);serial(q)=pass_number; +#endif +@;@/ +prev_break(q)=best_place[fit_class];@/ +q=get_node(active_node_size);break_node(q)=passive; +line_number(q)=best_pl_line[fit_class]+1; +fitness(q)=fit_class;type(q)=break_type; +total_demerits(q)=minimal_demerits[fit_class]; +link(q)=r;link(prev_r)=q;prev_r=q; +#ifdef @!STAT +if (tracing_paragraphs > 0) + @<Print a symbolic description of the new break node@>; +#endif +@;@/ +} + +@ @<Print a symbolic description of the new break node@>= +{@+print_nl("@@@@");print_int(serial(passive)); +@.\AT\AT@> +print(": line ");print_int(line_number(q)-1); +print_char('.');print_int(fit_class); +if (break_type==hyphenated) print_char('-'); +print(" t=");print_int(total_demerits(q)); +print(" -> @@@@"); +if (prev_break(passive)==null) print_char('0'); +else print_int(serial(prev_break(passive))); +} + +@ The length of lines depends on whether the user has specified +\.{\\parshape} or \.{\\hangindent}. If |par_shape_ptr| is not null, it +points to a $(2n+1)$-word record in |mem|, where the |info| in the first +word contains the value of |n|, and the other $2n$ words contain the left +margins and line lengths for the first |n| lines of the paragraph; the +specifications for line |n| apply to all subsequent lines. If +|par_shape_ptr==null|, the shape of the paragraph depends on the value of +|n==hang_after|; if |n >= 0|, hanging indentation takes place on lines |n+1|, +|n+2|, \dots, otherwise it takes place on lines 1, \dots, $\vert +n\vert$. When hanging indentation is active, the left margin is +|hang_indent|, if |hang_indent >= 0|, else it is 0; the line length is +$|hsize|-\vert|hang_indent|\vert$. The normal setting is +|par_shape_ptr==null|, |hang_after==1|, and |hang_indent==0|. +Note that if |hang_indent==0|, the value of |hang_after| is irrelevant. +@^length of lines@> @^hanging indentation@> + +@<Glob...@>= +static halfword @!easy_line; /*line numbers | > easy_line| are equivalent in break nodes*/ +static halfword @!last_special_line; /*line numbers | > last_special_line| all have + the same width*/ +static scaled @!first_width; /*the width of all lines | <= last_special_line|, if + no \.{\\parshape} has been specified*/ +static scaled @!second_width; /*the width of all lines | > last_special_line|*/ +static scaled @!first_indent; /*left margin to go with |first_width|*/ +static scaled @!second_indent; /*left margin to go with |second_width|*/ + +@ We compute the values of |easy_line| and the other local variables relating +to line length when the |line_break| procedure is initializing itself. + +@<Get ready to start...@>= +if (par_shape_ptr==null) + if (hang_indent==0) + {@+last_special_line=0;second_width=hsize; + second_indent=0; + } + else@<Set line length parameters in preparation for hanging indentation@>@; +else{@+last_special_line=info(par_shape_ptr)-1; + second_width=mem[par_shape_ptr+2*(last_special_line+1)].sc; + second_indent=mem[par_shape_ptr+2*last_special_line+1].sc; + } +if (looseness==0) easy_line=last_special_line; +else easy_line=max_halfword + +@ @<Set line length parameters in preparation for hanging indentation@>= +{@+last_special_line=abs(hang_after); +if (hang_after < 0) + {@+first_width=hsize-abs(hang_indent); + if (hang_indent >= 0) first_indent=hang_indent; + else first_indent=0; + second_width=hsize;second_indent=0; + } +else{@+first_width=hsize;first_indent=0; + second_width=hsize-abs(hang_indent); + if (hang_indent >= 0) second_indent=hang_indent; + else second_indent=0; + } +} + +@ When we come to the following code, we have just encountered the first +active node~|r| whose |line_number| field contains |l|. Thus we want to +compute the length of the $l\mskip1mu$th line of the current paragraph. Furthermore, +we want to set |old_l| to the last number in the class of line numbers +equivalent to~|l|. + +@<Compute the new line width@>= +if (l > easy_line) + {@+line_width=second_width;old_l=max_halfword-1; + } +else{@+old_l=l; + if (l > last_special_line) line_width=second_width; + else if (par_shape_ptr==null) line_width=first_width; + else line_width=mem[par_shape_ptr+2*l@,].sc; + } + +@ The remaining part of |try_break| deals with the calculation of +demerits for a break from |r| to |cur_p|. + +The first thing to do is calculate the badness, |b|. This value will always +be between zero and |inf_bad+1|; the latter value occurs only in the +case of lines from |r| to |cur_p| that cannot shrink enough to fit the necessary +width. In such cases, node |r| will be deactivated. +We also deactivate node~|r| when a break at~|cur_p| is forced, since future +breaks must go through a forced break. + +@<Consider the demerits for a line from |r| to |cur_p|...@>= +{@+artificial_demerits=false;@/ +@^inner loop@> +shortfall=line_width-cur_active_width[1]; /*we're this much too short*/ +if (shortfall > 0) + @<Set the value of |b| to the badness for stretching the line, and compute +the corresponding |fit_class|@>@; +else@<Set the value of |b| to the badness for shrinking the line, and compute +the corresponding |fit_class|@>; +if ((b > inf_bad)||(pi==eject_penalty)) + @<Prepare to deactivate node~|r|, and |goto deactivate| unless there is +a reason to consider lines of text from |r| to |cur_p|@>@; +else{@+prev_r=r; + if (b > threshold) goto resume; + node_r_stays_active=true; + } +@<Record a new feasible break@>; +if (node_r_stays_active) goto resume; /*|prev_r| has been set to |r|*/ +deactivate: @<Deactivate node |r|@>; +} + +@ When a line must stretch, the available stretchability can be found in the +subarray |cur_active_width[2 dotdot 5]|, in units of points, fil, fill, and filll. + +The present section is part of \TeX's inner loop, and it is most often performed +when the badness is infinite; therefore it is worth while to make a quick +test for large width excess and small stretchability, before calling the +|badness| subroutine. +@^inner loop@> + +@<Set the value of |b| to the badness for stretching...@>= +if ((cur_active_width[3]!=0)||(cur_active_width[4]!=0)||@| + (cur_active_width[5]!=0)) + {@+b=0;fit_class=decent_fit; /*infinite stretch*/ + } +else{@+if (shortfall > 7230584) if (cur_active_width[2] < 1663497) + {@+b=inf_bad;fit_class=very_loose_fit;goto done1; + } + b=badness(shortfall, cur_active_width[2]); + if (b > 12) + if (b > 99) fit_class=very_loose_fit; + else fit_class=loose_fit; + else fit_class=decent_fit; + done1: ; + } + +@ Shrinkability is never infinite in a paragraph; +we can shrink the line from |r| to |cur_p| by at most |cur_active_width[6]|. + +@<Set the value of |b| to the badness for shrinking...@>= +{@+if (-shortfall > cur_active_width[6]) b=inf_bad+1; +else b=badness(-shortfall, cur_active_width[6]); +if (b > 12) fit_class=tight_fit;@+else fit_class=decent_fit; +} + +@ During the final pass, we dare not lose all active nodes, lest we lose +touch with the line breaks already found. The code shown here makes sure +that such a catastrophe does not happen, by permitting overfull boxes as +a last resort. This particular part of \TeX\ was a source of several subtle +bugs before the correct program logic was finally discovered; readers +who seek to ``improve'' \TeX\ should therefore think thrice before daring +to make any changes here. +@^overfull boxes@> + +@<Prepare to deactivate node~|r|, and |goto deactivate| unless...@>= +{@+if (final_pass&&(minimum_demerits==awful_bad)&&@| + (link(r)==last_active)&& + (prev_r==active)) + artificial_demerits=true; /*set demerits zero, this break is forced*/ +else if (b > threshold) goto deactivate; +node_r_stays_active=false; +} + +@ When we get to this part of the code, the line from |r| to |cur_p| is +feasible, its badness is~|b|, and its fitness classification is |fit_class|. +We don't want to make an active node for this break yet, but we will +compute the total demerits and record them in the |minimal_demerits| array, +if such a break is the current champion among all ways to get to |cur_p| +in a given line-number class and fitness class. + +@<Record a new feasible break@>= +if (artificial_demerits) d=0; +else@<Compute the demerits, |d|, from |r| to |cur_p|@>; +#ifdef @!STAT +if (tracing_paragraphs > 0) + @<Print a symbolic description of this feasible break@>; +#endif +@;@/ +d=d+total_demerits(r); /*this is the minimum total demerits + from the beginning to |cur_p| via |r|*/ +if (d <= minimal_demerits[fit_class]) + {@+minimal_demerits[fit_class]=d; + best_place[fit_class]=break_node(r);best_pl_line[fit_class]=l; + if (d < minimum_demerits) minimum_demerits=d; + } + +@ @<Print a symbolic description of this feasible break@>= +{@+if (printed_node!=cur_p) + @<Print the list between |printed_node| and |cur_p|, then set |printed_node:=cur_p|@>; +print_nl("@@"); +@.\AT@> +if (cur_p==null) print_esc("par"); +else if (type(cur_p)!=glue_node) + {@+if (type(cur_p)==penalty_node) print_esc("penalty"); + else if (type(cur_p)==disc_node) print_esc("discretionary"); + else if (type(cur_p)==kern_node) print_esc("kern"); + else print_esc("math"); + } +print(" via @@@@"); +if (break_node(r)==null) print_char('0'); +else print_int(serial(break_node(r))); +print(" b="); +if (b > inf_bad) print_char('*');@+else print_int(b); +@.*\relax@> +print(" p=");print_int(pi);print(" d="); +if (artificial_demerits) print_char('*');@+else print_int(d); +} + +@ @<Print the list between |printed_node| and |cur_p|...@>= +{@+print_nl(""); +if (cur_p==null) short_display(link(printed_node)); +else{@+save_link=link(cur_p); + link(cur_p)=null;print_nl("");short_display(link(printed_node)); + link(cur_p)=save_link; + } +printed_node=cur_p; +} + +@ When the data for a discretionary break is being displayed, we will have +printed the |pre_break| and |post_break| lists; we want to skip over the +third list, so that the discretionary data will not appear twice. The +following code is performed at the very end of |try_break|. + +@<Update the value of |printed_node|...@>= +if (cur_p==printed_node) if (cur_p!=null) if (type(cur_p)==disc_node) + {@+t=replace_count(cur_p); + while (t > 0) + {@+decr(t);printed_node=link(printed_node); + } + } + +@ @<Compute the demerits, |d|, from |r| to |cur_p|@>= +{@+d=line_penalty+b; +if (abs(d) >= 10000) d=100000000;@+else d=d*d; +if (pi!=0) + if (pi > 0) d=d+pi*pi; + else if (pi > eject_penalty) d=d-pi*pi; +if ((break_type==hyphenated)&&(type(r)==hyphenated)) + if (cur_p!=null) d=d+double_hyphen_demerits; + else d=d+final_hyphen_demerits; +if (abs(fit_class-fitness(r)) > 1) d=d+adj_demerits; +} + +@ When an active node disappears, we must delete an adjacent delta node if the +active node was at the beginning or the end of the active list, or if it +was surrounded by delta nodes. We also must preserve the property that +|cur_active_width| represents the length of material from |link(prev_r)| +to~|cur_p|. + +@d combine_two_deltas(A) @|mem[prev_r+A].sc=mem[prev_r+A].sc+mem[r+A].sc +@d downdate_width(A) @|cur_active_width[A]=cur_active_width[A]- + mem[prev_r+A].sc + +@<Deactivate node |r|@>= +link(prev_r)=link(r);free_node(r, active_node_size); +if (prev_r==active) @<Update the active widths, since the first active node +has been deleted@>@; +else if (type(prev_r)==delta_node) + {@+r=link(prev_r); + if (r==last_active) + {@+do_all_six(downdate_width); + link(prev_prev_r)=last_active; + free_node(prev_r, delta_node_size);prev_r=prev_prev_r; + } + else if (type(r)==delta_node) + {@+do_all_six(update_width); + do_all_six(combine_two_deltas); + link(prev_r)=link(r);free_node(r, delta_node_size); + } + } + +@ The following code uses the fact that |type(last_active)!=delta_node|. If the +active list has just become empty, we do not need to update the +|active_width| array, since it will be initialized when an active +node is next inserted. + +@d update_active(A) active_width[A]=active_width[A]+mem[r+A].sc + +@<Update the active widths,...@>= +{@+r=link(active); +if (type(r)==delta_node) + {@+do_all_six(update_active); + do_all_six(copy_to_cur_active); + link(active)=link(r);free_node(r, delta_node_size); + } +} + +@* Breaking paragraphs into lines, continued. +So far we have gotten a little way into the |line_break| routine, having +covered its important |try_break| subroutine. Now let's consider the +rest of the process. + +The main loop of |line_break| traverses the given hlist, +starting at |link(temp_head)|, and calls |try_break| at each legal +breakpoint. A variable called |auto_breaking| is set to true except +within math formulas, since glue nodes are not legal breakpoints when +they appear in formulas. + +The current node of interest in the hlist is pointed to by |cur_p|. Another +variable, |prev_p|, is usually one step behind |cur_p|, but the real +meaning of |prev_p| is this: If |type(cur_p)==glue_node| then |cur_p| is a legal +breakpoint if and only if |auto_breaking| is true and |prev_p| does not +point to a glue node, penalty node, explicit kern node, or math node. + +The following declarations provide for a few other local variables that are +used in special calculations. + +@<Local variables for line breaking@>= +bool @!auto_breaking; /*is node |cur_p| outside a formula?*/ +pointer @!prev_p; /*helps to determine when glue nodes are breakpoints*/ +pointer @!q, @!r, @!s, @!prev_s; /*miscellaneous nodes of temporary interest*/ +internal_font_number @!f; /*used when calculating character widths*/ + +@ The `\ignorespaces|loop|\unskip' in the following code is performed at most +thrice per call of |line_break|, since it is actually a pass over the +entire paragraph. + +@<Find optimal breakpoints@>= +threshold=pretolerance; +if (threshold >= 0) + { +#ifdef @!STAT +if (tracing_paragraphs > 0) + {@+begin_diagnostic();print_nl("@@firstpass");@+} @; +#endif +@;@/ + second_pass=false;final_pass=false; + } +else{@+threshold=tolerance;second_pass=true; + final_pass=(emergency_stretch <= 0); +#ifdef @!STAT + if (tracing_paragraphs > 0) begin_diagnostic(); +#endif +@; + } +loop@+{@+if (threshold > inf_bad) threshold=inf_bad; + if (second_pass) @<Initialize for hyphenating a paragraph@>; + @<Create an active breakpoint representing the beginning of the paragraph@>; + cur_p=link(temp_head);auto_breaking=true;@/ + prev_p=cur_p; /*glue at beginning is not a legal breakpoint*/ + while ((cur_p!=null)&&(link(active)!=last_active)) + @<Call |try_break| if |cur_p| is a legal breakpoint; on the second pass, +also try to hyphenate the next word, if |cur_p| is a glue node; then advance +|cur_p| to the next node of the paragraph that could possibly be a legal breakpoint@>; + if (cur_p==null) + @<Try the final line break at the end of the paragraph, and |goto done| +if the desired breakpoints have been found@>; + @<Clean up the memory by removing the break nodes@>; + if (!second_pass) + { +#ifdef @!STAT +if (tracing_paragraphs > 0) print_nl("@@secondpass");@; +#endif + threshold=tolerance;second_pass=true;final_pass=(emergency_stretch <= 0); + } /*if at first you don't succeed, \dots*/ + else{ +#ifdef @!STAT +if (tracing_paragraphs > 0) + print_nl("@@emergencypass");@; +#endif + background[2]=background[2]+emergency_stretch;final_pass=true; + } + } +done: +#ifdef @!STAT +if (tracing_paragraphs > 0) + {@+end_diagnostic(true);normalize_selector(); + } +#endif + +@ The active node that represents the starting point does not need a +corresponding passive node. + +@d store_background(A) active_width[A]=background[A] + +@<Create an active breakpoint representing the beginning of the paragraph@>= +q=get_node(active_node_size); +type(q)=unhyphenated;fitness(q)=decent_fit; +link(q)=last_active;break_node(q)=null; +line_number(q)=prev_graf+1;total_demerits(q)=0;link(active)=q; +do_all_six(store_background);@/ +passive=null;printed_node=temp_head;pass_number=0; +font_in_short_display=null_font + +@ @<Clean...@>= +q=link(active); +while (q!=last_active) + {@+cur_p=link(q); + if (type(q)==delta_node) free_node(q, delta_node_size); + else free_node(q, active_node_size); + q=cur_p; + } +q=passive; +while (q!=null) + {@+cur_p=link(q); + free_node(q, passive_node_size); + q=cur_p; + } + +@ Here is the main switch in the |line_break| routine, where legal breaks +are determined. As we move through the hlist, we need to keep the |active_width| +array up to date, so that the badness of individual lines is readily calculated +by |try_break|. It is convenient to use the short name |act_width| for +the component of active width that represents real width as opposed to glue. + +@d act_width active_width[1] /*length from first active node to current node*/ +@d kern_break {@+if (!is_char_node(link(cur_p))&&auto_breaking) + if (type(link(cur_p))==glue_node) try_break(0, unhyphenated); + act_width=act_width+width(cur_p); + } + +@<Call |try_break| if |cur_p| is a legal breakpoint...@>= +{@+if (is_char_node(cur_p)) + @<Advance \(c)|cur_p| to the node following the present string of characters@>; +switch (type(cur_p)) { +case hlist_node: case vlist_node: case rule_node: act_width=act_width+width(cur_p);@+break; +case whatsit_node: @<Advance \(p)past a whatsit node in the \(l)|line_break| +loop@>@;@+break; +case glue_node: {@+@<If node |cur_p| is a legal breakpoint, call |try_break|; +then update the active widths by including the glue in |glue_ptr(cur_p)|@>; + if (second_pass&&auto_breaking) + @<Try to hyphenate the following word@>; + } @+break; +case kern_node: if (subtype(cur_p)==explicit) kern_break@; + else act_width=act_width+width(cur_p);@+break; +case ligature_node: {@+f=font(lig_char(cur_p)); + act_width=act_width+char_width(f, char_info(f, character(lig_char(cur_p)))); + } @+break; +case disc_node: @<Try to break after a discretionary fragment, then |goto +done5|@>@; +case math_node: {@+auto_breaking=(subtype(cur_p)==after);kern_break; + } @+break; +case penalty_node: try_break(penalty(cur_p), unhyphenated);@+break; +case mark_node: case ins_node: case adjust_node: do_nothing;@+break; +default:confusion("paragraph"); +@:this can't happen paragraph}{\quad paragraph@> +} @/ +prev_p=cur_p;cur_p=link(cur_p); +done5: ;} + +@ The code that passes over the characters of words in a paragraph is +part of \TeX's inner loop, so it has been streamlined for speed. We use +the fact that `\.{\\parfillskip}' glue appears at the end of each paragraph; +it is therefore unnecessary to check if |link(cur_p)==null| when |cur_p| is a +character node. +@^inner loop@> + +@<Advance \(c)|cur_p| to the node following the present string...@>= +{@+prev_p=cur_p; +@/do@+{f=font(cur_p); +act_width=act_width+char_width(f, char_info(f, character(cur_p))); +cur_p=link(cur_p); +}@+ while (!(!is_char_node(cur_p))); +} + +@ When node |cur_p| is a glue node, we look at |prev_p| to see whether or not +a breakpoint is legal at |cur_p|, as explained above. + +@<If node |cur_p| is a legal breakpoint, call...@>= +if (auto_breaking) + {@+if (is_char_node(prev_p)) try_break(0, unhyphenated); + else if (precedes_break(prev_p)) try_break(0, unhyphenated); + else if ((type(prev_p)==kern_node)&&(subtype(prev_p)!=explicit)) + try_break(0, unhyphenated); + } +check_shrinkage(glue_ptr(cur_p));q=glue_ptr(cur_p); +act_width=act_width+width(q);@| +active_width[2+stretch_order(q)]=@| + active_width[2+stretch_order(q)]+stretch(q);@/ +active_width[6]=active_width[6]+shrink(q) + +@ The following code knows that discretionary texts contain +only character nodes, kern nodes, box nodes, rule nodes, and ligature nodes. + +@<Try to break after a discretionary fragment...@>= +{@+s=pre_break(cur_p);disc_width=0; +if (s==null) try_break(ex_hyphen_penalty, hyphenated); +else{@+@/do@+{@<Add the width of node |s| to |disc_width|@>; + s=link(s); + }@+ while (!(s==null)); + act_width=act_width+disc_width; + try_break(hyphen_penalty, hyphenated); + act_width=act_width-disc_width; + } +r=replace_count(cur_p);s=link(cur_p); +while (r > 0) + {@+@<Add the width of node |s| to |act_width|@>; + decr(r);s=link(s); + } +prev_p=cur_p;cur_p=s;goto done5; +} + +@ @<Add the width of node |s| to |disc_width|@>= +if (is_char_node(s)) + {@+f=font(s); + disc_width=disc_width+char_width(f, char_info(f, character(s))); + } +else switch (type(s)) { + case ligature_node: {@+f=font(lig_char(s)); + disc_width=disc_width+ + char_width(f, char_info(f, character(lig_char(s)))); + } @+break; + case hlist_node: case vlist_node: case rule_node: + case kern_node: + disc_width=disc_width+width(s);@+break; + default:confusion("disc3"); +@:this can't happen disc3}{\quad disc3@> + } + +@ @<Add the width of node |s| to |act_width|@>= +if (is_char_node(s)) + {@+f=font(s); + act_width=act_width+char_width(f, char_info(f, character(s))); + } +else switch (type(s)) { + case ligature_node: {@+f=font(lig_char(s)); + act_width=act_width+ + char_width(f, char_info(f, character(lig_char(s)))); + } @+break; + case hlist_node: case vlist_node: case rule_node: + case kern_node: + act_width=act_width+width(s);@+break; + default:confusion("disc4"); +@:this can't happen disc4}{\quad disc4@> + } + +@ The forced line break at the paragraph's end will reduce the list of +breakpoints so that all active nodes represent breaks at |cur_p==null|. +On the first pass, we insist on finding an active node that has the +correct ``looseness.'' On the final pass, there will be at least one active +node, and we will match the desired looseness as well as we can. + +The global variable |best_bet| will be set to the active node for the best +way to break the paragraph, and a few other variables are used to +help determine what is best. + +@<Glob...@>= +static pointer @!best_bet; /*use this passive node and its predecessors*/ +static int @!fewest_demerits; /*the demerits associated with |best_bet|*/ +static halfword @!best_line; /*line number following the last line of the new paragraph*/ +static int @!actual_looseness; /*the difference between |line_number(best_bet)| + and the optimum |best_line|*/ +static int @!line_diff; /*the difference between the current line number and + the optimum |best_line|*/ + +@ @<Try the final line break at the end of the paragraph...@>= +{@+try_break(eject_penalty, hyphenated); +if (link(active)!=last_active) + {@+@<Find an active node with fewest demerits@>; + if (looseness==0) goto done; + @<Find the best active node for the desired looseness@>; + if ((actual_looseness==looseness)||final_pass) goto done; + } +} + +@ @<Find an active node...@>= +r=link(active);fewest_demerits=awful_bad; +@/do@+{if (type(r)!=delta_node) if (total_demerits(r) < fewest_demerits) + {@+fewest_demerits=total_demerits(r);best_bet=r; + } +r=link(r); +}@+ while (!(r==last_active)); +best_line=line_number(best_bet) + +@ The adjustment for a desired looseness is a slightly more complicated +version of the loop just considered. Note that if a paragraph is broken +into segments by displayed equations, each segment will be subject to the +looseness calculation, independently of the other segments. + +@<Find the best active node...@>= +{@+r=link(active);actual_looseness=0; +@/do@+{if (type(r)!=delta_node) + {@+line_diff=line_number(r)-best_line; + if (((line_diff < actual_looseness)&&(looseness <= line_diff))||@| + ((line_diff > actual_looseness)&&(looseness >= line_diff))) + {@+best_bet=r;actual_looseness=line_diff; + fewest_demerits=total_demerits(r); + } + else if ((line_diff==actual_looseness)&&@| + (total_demerits(r) < fewest_demerits)) + {@+best_bet=r;fewest_demerits=total_demerits(r); + } + } +r=link(r); +}@+ while (!(r==last_active)); +best_line=line_number(best_bet); +} + +@ Once the best sequence of breakpoints has been found (hurray), we call on the +procedure |post_line_break| to finish the remainder of the work. +(By introducing this subprocedure, we are able to keep |line_break| +from getting extremely long.) + +@<Break the paragraph at the chosen...@>= +post_line_break(final_widow_penalty) + +@ The total number of lines that will be set by |post_line_break| +is |best_line-prev_graf-1|. The last breakpoint is specified by +|break_node(best_bet)|, and this passive node points to the other breakpoints +via the |prev_break| links. The finishing-up phase starts by linking the +relevant passive nodes in forward order, changing |prev_break| to +|next_break|. (The |next_break| fields actually reside in the same memory +space as the |prev_break| fields did, but we give them a new name because +of their new significance.) Then the lines are justified, one by one. + +@d next_break prev_break /*new name for |prev_break| after links are reversed*/ + +@<Declare subprocedures for |line_break|@>= +static void post_line_break(int @!final_widow_penalty) +{@+ +pointer q, @!r, @!s; /*temporary registers for list manipulation*/ +bool @!disc_break; /*was the current break at a discretionary node?*/ +bool @!post_disc_break; /*and did it have a nonempty post-break part?*/ +scaled @!cur_width; /*width of line number |cur_line|*/ +scaled @!cur_indent; /*left margin of line number |cur_line|*/ +quarterword @!t; /*used for replacement counts in discretionary nodes*/ +int @!pen; /*use when calculating penalties between lines*/ +halfword @!cur_line; /*the current line number being justified*/ +@<Reverse the links of the relevant passive nodes, setting |cur_p| to the +first breakpoint@>; +cur_line=prev_graf+1; +@/do@+{@<Justify the line ending at breakpoint |cur_p|, and append it to the +current vertical list, together with associated penalties and other insertions@>; +incr(cur_line);cur_p=next_break(cur_p); +if (cur_p!=null) if (!post_disc_break) + @<Prune unwanted nodes at the beginning of the next line@>; +}@+ while (!(cur_p==null)); +if ((cur_line!=best_line)||(link(temp_head)!=null)) + confusion("line breaking"); +@:this can't happen line breaking}{\quad line breaking@> +prev_graf=best_line-1; +} + +@ The job of reversing links in a list is conveniently regarded as the job +of taking items off one stack and putting them on another. In this case we +take them off a stack pointed to by |q| and having |prev_break| fields; +we put them on a stack pointed to by |cur_p| and having |next_break| fields. +Node |r| is the passive node being moved from stack to stack. + +@<Reverse the links of the relevant passive nodes...@>= +q=break_node(best_bet);cur_p=null; +@/do@+{r=q;q=prev_break(q);next_break(r)=cur_p;cur_p=r; +}@+ while (!(q==null)) + +@ Glue and penalty and kern and math nodes are deleted at the beginning of +a line, except in the anomalous case that the node to be deleted is actually +one of the chosen breakpoints. Otherwise +the pruning done here is designed to match +the lookahead computation in |try_break|, where the |break_width| values +are computed for non-discretionary breakpoints. + +@<Prune unwanted nodes at the beginning of the next line@>= +{@+r=temp_head; +loop@+{@+q=link(r); + if (q==cur_break(cur_p)) goto done1; + /*|cur_break(cur_p)| is the next breakpoint*/ + /*now |q| cannot be |null|*/ + if (is_char_node(q)) goto done1; + if (non_discardable(q)) goto done1; + if (type(q)==kern_node) if (subtype(q)!=explicit) goto done1; + r=q; /*now |type(q)==glue_node|, |kern_node|, |math_node|, or |penalty_node|*/ + } +done1: if (r!=temp_head) + {@+link(r)=null;flush_node_list(link(temp_head)); + link(temp_head)=q; + } +} + +@ The current line to be justified appears in a horizontal list starting +at |link(temp_head)| and ending at |cur_break(cur_p)|. If |cur_break(cur_p)| is +a glue node, we reset the glue to equal the |right_skip| glue; otherwise +we append the |right_skip| glue at the right. If |cur_break(cur_p)| is a +discretionary node, we modify the list so that the discretionary break +is compulsory, and we set |disc_break| to |true|. We also append +the |left_skip| glue at the left of the line, unless it is zero. + +@<Justify the line ending at breakpoint |cur_p|, and append it...@>= +@<Modify the end of the line to reflect the nature of the break and to include +\.{\\rightskip}; also set the proper value of |disc_break|@>; +@<Put the \(l)\.{\\leftskip} glue at the left and detach this line@>; +@<Call the packaging subroutine, setting |just_box| to the justified box@>; +@<Append the new box to the current vertical list, followed by the list of +special nodes taken out of the box by the packager@>; +@<Append a penalty node, if a nonzero penalty is appropriate@>@; + +@ At the end of the following code, |q| will point to the final node on the +list about to be justified. + +@<Modify the end of the line...@>= +q=cur_break(cur_p);disc_break=false;post_disc_break=false; +if (q!=null) /*|q| cannot be a |char_node|*/ + if (type(q)==glue_node) + {@+delete_glue_ref(glue_ptr(q)); + glue_ptr(q)=right_skip; + subtype(q)=right_skip_code+1;add_glue_ref(right_skip); + goto done; + } + else{@+if (type(q)==disc_node) + @<Change discretionary to compulsory and set |disc_break:=true|@>@; + else if ((type(q)==math_node)||(type(q)==kern_node)) width(q)=0; + } +else{@+q=temp_head; + while (link(q)!=null) q=link(q); + } +@<Put the \(r)\.{\\rightskip} glue after node |q|@>; +done: + +@ @<Change discretionary to compulsory...@>= +{@+t=replace_count(q); +@<Destroy the |t| nodes following |q|, and make |r| point to the following +node@>; +if (post_break(q)!=null) @<Transplant the post-break list@>; +if (pre_break(q)!=null) @<Transplant the pre-break list@>; +link(q)=r;disc_break=true; +} + +@ @<Destroy the |t| nodes following |q|...@>= +if (t==0) r=link(q); +else{@+r=q; + while (t > 1) + {@+r=link(r);decr(t); + } + s=link(r); + r=link(s);link(s)=null; + flush_node_list(link(q));replace_count(q)=0; + } + +@ We move the post-break list from inside node |q| to the main list by +re\-attaching it just before the present node |r|, then resetting |r|. + +@<Transplant the post-break list@>= +{@+s=post_break(q); +while (link(s)!=null) s=link(s); +link(s)=r;r=post_break(q);post_break(q)=null;post_disc_break=true; +} + +@ We move the pre-break list from inside node |q| to the main list by +re\-attaching it just after the present node |q|, then resetting |q|. + +@<Transplant the pre-break list@>= +{@+s=pre_break(q);link(q)=s; +while (link(s)!=null) s=link(s); +pre_break(q)=null;q=s; +} + +@ @<Put the \(r)\.{\\rightskip} glue after node |q|@>= +r=new_param_glue(right_skip_code);link(r)=link(q);link(q)=r;q=r + +@ The following code begins with |q| at the end of the list to be +justified. It ends with |q| at the beginning of that list, and with +|link(temp_head)| pointing to the remainder of the paragraph, if any. + +@<Put the \(l)\.{\\leftskip} glue at the left...@>= +r=link(q);link(q)=null;q=link(temp_head);link(temp_head)=r; +if (left_skip!=zero_glue) + {@+r=new_param_glue(left_skip_code); + link(r)=q;q=r; + } + +@ @<Append the new box to the current vertical list...@>= +append_to_vlist(just_box); +if (adjust_head!=adjust_tail) + {@+link(tail)=link(adjust_head);tail=adjust_tail; + } +adjust_tail=null + +@ Now |q| points to the hlist that represents the current line of the +paragraph. We need to compute the appropriate line width, pack the +line into a box of this size, and shift the box by the appropriate +amount of indentation. + +@<Call the packaging subroutine...@>= +if (cur_line > last_special_line) + {@+cur_width=second_width;cur_indent=second_indent; + } +else if (par_shape_ptr==null) + {@+cur_width=first_width;cur_indent=first_indent; + } +else{@+cur_width=mem[par_shape_ptr+2*cur_line].sc; + cur_indent=mem[par_shape_ptr+2*cur_line-1].sc; + } +adjust_tail=adjust_head;just_box=hpack(q, cur_width, exactly); +shift_amount(just_box)=cur_indent + +@ Penalties between the lines of a paragraph come from club and widow lines, +from the |inter_line_penalty| parameter, and from lines that end at +discretionary breaks. Breaking between lines of a two-line paragraph gets +both club-line and widow-line penalties. The local variable |pen| will +be set to the sum of all relevant penalties for the current line, except +that the final line is never penalized. + +@<Append a penalty node, if a nonzero penalty is appropriate@>= +if (cur_line+1!=best_line) + {@+pen=inter_line_penalty; + if (cur_line==prev_graf+1) pen=pen+club_penalty; + if (cur_line+2==best_line) pen=pen+final_widow_penalty; + if (disc_break) pen=pen+broken_penalty; + if (pen!=0) + {@+r=new_penalty(pen); + link(tail)=r;tail=r; + } + } + +@* Pre-hyphenation. +When the line-breaking routine is unable to find a feasible sequence of +breakpoints, it makes a second pass over the paragraph, attempting to +hyphenate the hyphenatable words. The goal of hyphenation is to insert +discretionary material into the paragraph so that there are more +potential places to break. + +The general rules for hyphenation are somewhat complex and technical, +because we want to be able to hyphenate words that are preceded or +followed by punctuation marks, and because we want the rules to work +for languages other than English. We also must contend with the fact +that hyphens might radically alter the ligature and kerning structure +of a word. + +A sequence of characters will be considered for hyphenation only if it +belongs to a ``potentially hyphenatable part'' of the current paragraph. +This is a sequence of nodes $p_0p_1\ldots p_m$ where $p_0$ is a glue node, +$p_1\ldots p_{m-1}$ are either character or ligature or whatsit or +implicit kern nodes, and $p_m$ is a glue or penalty or insertion or adjust +or mark or whatsit or explicit kern node. (Therefore hyphenation is +disabled by boxes, math formulas, and discretionary nodes already inserted +by the user.) The ligature nodes among $p_1\ldots p_{m-1}$ are effectively +expanded into the original non-ligature characters; the kern nodes and +whatsits are ignored. Each character |c| is now classified as either a +nonletter (if |lc_code(c)==0|), a lowercase letter (if +|lc_code(c)==c|), or an uppercase letter (otherwise); an uppercase letter +is treated as if it were |lc_code(c)| for purposes of hyphenation. The +characters generated by $p_1\ldots p_{m-1}$ may begin with nonletters; let +$c_1$ be the first letter that is not in the middle of a ligature. Whatsit +nodes preceding $c_1$ are ignored; a whatsit found after $c_1$ will be the +terminating node $p_m$. All characters that do not have the same font as +$c_1$ will be treated as nonletters. The |hyphen_char| for that font +must be between 0 and 255, otherwise hyphenation will not be attempted. +\TeX\ looks ahead for as many consecutive letters $c_1\ldots c_n$ as +possible; however, |n| must be less than 64, so a character that would +otherwise be $c_{64}$ is effectively not a letter. Furthermore $c_n$ must +not be in the middle of a ligature. In this way we obtain a string of +letters $c_1\ldots c_n$ that are generated by nodes $p_a\ldots p_b$, where +|1 <= a <= b+1 <= m|. If |n >= l_hyf+r_hyf|, this string qualifies for hyphenation; +however, |uc_hyph| must be positive, if $c_1$ is uppercase. + +The hyphenation process takes place in three stages. First, the candidate +sequence $c_1\ldots c_n$ is found; then potential positions for hyphens +are determined by referring to hyphenation tables; and finally, the nodes +$p_a\ldots p_b$ are replaced by a new sequence of nodes that includes the +discretionary breaks found. + +Fortunately, we do not have to do all this calculation very often, because +of the way it has been taken out of \TeX's inner loop. For example, when +the second edition of the author's 700-page book {\sl Seminumerical +Algorithms} was typeset by \TeX, only about 1.2 hyphenations needed to be +@^Knuth, Donald Ervin@> +tried per paragraph, since the line breaking algorithm needed to use two +passes on only about 5 per cent of the paragraphs. + +@<Initialize for hyphenating...@>= +{ +#ifdef @!INIT +if (trie_not_ready) init_trie(); +#endif +@;@/ +cur_lang=init_cur_lang;l_hyf=init_l_hyf;r_hyf=init_r_hyf; +set_hyph_index; +} + +@ The letters $c_1\ldots c_n$ that are candidates for hyphenation are placed +into an array called |hc|; the number |n| is placed into |hn|; pointers to +nodes $p_{a-1}$ and~$p_b$ in the description above are placed into variables +|ha| and |hb|; and the font number is placed into |hf|. + +@<Glob...@>= +static int16_t @!hc[66]; /*word to be hyphenated*/ +static int @!hn; /*the number of positions occupied in |hc|; + not always a |small_number|*/ +static pointer @!ha, @!hb; /*nodes |ha dotdot hb| should be replaced by the hyphenated result*/ +static internal_font_number @!hf; /*font number of the letters in |hc|*/ +static int16_t @!hu[64]; /*like |hc|, before conversion to lowercase*/ +static int @!hyf_char; /*hyphen character of the relevant font*/ +static ASCII_code @!cur_lang, @!init_cur_lang; /*current hyphenation table of interest*/ +static int @!l_hyf, @!r_hyf, @!init_l_hyf, @!init_r_hyf; /*limits on fragment sizes*/ +static halfword @!hyf_bchar; /*boundary character after $c_n$*/ + +@ Hyphenation routines need a few more local variables. + +@<Local variables for line...@>= +small_number @!j; /*an index into |hc| or |hu|*/ +int @!c; /*character being considered for hyphenation*/ + +@ When the following code is activated, the |line_break| procedure is in its +second pass, and |cur_p| points to a glue node. + +@<Try to hyphenate...@>= +{@+prev_s=cur_p;s=link(prev_s); +if (s!=null) + {@+@<Skip to node |ha|, or |goto done1| if no hyphenation should be attempted@>; + if (l_hyf+r_hyf > 63) goto done1; + @<Skip to node |hb|, putting letters into |hu| and |hc|@>; + @<Check that the nodes following |hb| permit hyphenation and that at least +|l_hyf+r_hyf| letters have been found, otherwise |goto done1|@>; + hyphenate(); + } +done1: ;} + +@ @<Declare subprocedures for |line_break|@>= +@t\4@>@<Declare the function called |reconstitute|@>@; +static void hyphenate(void) +{@+ +@<Local variables for hyphenation@>@; +@<Find hyphen locations for the word in |hc|, or |return|@>; +@<If no hyphens were found, |return|@>; +@<Replace nodes |ha..hb| by a sequence of nodes that includes the discretionary +hyphens@>; +} + +@ The first thing we need to do is find the node |ha| just before the +first letter. + +@<Skip to node |ha|, or |goto done1|...@>= +loop@+{@+if (is_char_node(s)) + {@+c=qo(character(s));hf=font(s); + } + else if (type(s)==ligature_node) + if (lig_ptr(s)==null) goto resume; + else{@+q=lig_ptr(s);c=qo(character(q));hf=font(q); + } + else if ((type(s)==kern_node)&&(subtype(s)==normal)) goto resume; + else if (type(s)==whatsit_node) + {@+@<Advance \(p)past a whatsit node in the \(p)pre-hyphenation loop@>; + goto resume; + } + else goto done1; + set_lc_code(c); + if (hc[0]!=0) + if ((hc[0]==c)||(uc_hyph > 0)) goto done2; + else goto done1; +resume: prev_s=s;s=link(prev_s); + } +done2: hyf_char=hyphen_char[hf]; +if (hyf_char < 0) goto done1; +if (hyf_char > 255) goto done1; +ha=prev_s + +@ The word to be hyphenated is now moved to the |hu| and |hc| arrays. + +@<Skip to node |hb|, putting letters...@>= +hn=0; +loop@+{@+if (is_char_node(s)) + {@+if (font(s)!=hf) goto done3; + hyf_bchar=character(s);c=qo(hyf_bchar); + set_lc_code(c); + if (hc[0]==0) goto done3; + if (hn==63) goto done3; + hb=s;incr(hn);hu[hn]=c;hc[hn]=hc[0];hyf_bchar=non_char; + } + else if (type(s)==ligature_node) + @<Move the characters of a ligature node to |hu| and |hc|; but |goto done3| +if they are not all letters@>@; + else if ((type(s)==kern_node)&&(subtype(s)==normal)) + {@+hb=s; + hyf_bchar=font_bchar[hf]; + } + else goto done3; + s=link(s); + } +done3: + +@ We let |j| be the index of the character being stored when a ligature node +is being expanded, since we do not want to advance |hn| until we are sure +that the entire ligature consists of letters. Note that it is possible +to get to |done3| with |hn==0| and |hb| not set to any value. + +@<Move the characters of a ligature node to |hu| and |hc|...@>= +{@+if (font(lig_char(s))!=hf) goto done3; +j=hn;q=lig_ptr(s);@+if (q > null) hyf_bchar=character(q); +while (q > null) + {@+c=qo(character(q)); + set_lc_code(c); + if (hc[0]==0) goto done3; + if (j==63) goto done3; + incr(j);hu[j]=c;hc[j]=hc[0];@/ + q=link(q); + } +hb=s;hn=j; +if (odd(subtype(s))) hyf_bchar=font_bchar[hf];@+else hyf_bchar=non_char; +} + +@ @<Check that the nodes following |hb| permit hyphenation...@>= +if (hn < l_hyf+r_hyf) goto done1; /*|l_hyf| and |r_hyf| are | >= 1|*/ +loop@+{@+if (!(is_char_node(s))) + switch (type(s)) { + case ligature_node: do_nothing;@+break; + case kern_node: if (subtype(s)!=normal) goto done4;@+break; + case whatsit_node: case glue_node: + case penalty_node: case ins_node: case adjust_node: + case mark_node: + goto done4; + default:goto done1; + } + s=link(s); + } +done4: + +@* Post-hyphenation. +If a hyphen may be inserted between |hc[j]| and |hc[j+1]|, the hyphenation +procedure will set |hyf[j]| to some small odd number. But before we look +at \TeX's hyphenation procedure, which is independent of the rest of the +line-breaking algorithm, let us consider what we will do with the hyphens +it finds, since it is better to work on this part of the program before +forgetting what |ha| and |hb|, etc., are all about. + +@<Glob...@>= +static int8_t @!hyf[65]; /*odd values indicate discretionary hyphens*/ +static pointer @!init_list; /*list of punctuation characters preceding the word*/ +static bool @!init_lig; /*does |init_list| represent a ligature?*/ +static bool @!init_lft; /*if so, did the ligature involve a left boundary?*/ + +@ @<Local variables for hyphenation@>= +int @!i, @!j, @!l; /*indices into |hc| or |hu|*/ +pointer @!q, @!r, @!s; /*temporary registers for list manipulation*/ +halfword @!bchar; /*boundary character of hyphenated word, or |non_char|*/ + +@ \TeX\ will never insert a hyphen that has fewer than +\.{\\lefthyphenmin} letters before it or fewer than +\.{\\righthyphenmin} after it; hence, a short word has +comparatively little chance of being hyphenated. If no hyphens have +been found, we can save time by not having to make any changes to the +paragraph. + +@<If no hyphens were found, |return|@>= +for (j=l_hyf; j<=hn-r_hyf; j++) if (odd(hyf[j])) goto found1; +return; +found1: + +@ If hyphens are in fact going to be inserted, \TeX\ first deletes the +subsequence of nodes between |ha| and~|hb|. An attempt is made to +preserve the effect that implicit boundary characters and punctuation marks +had on ligatures inside the hyphenated word, by storing a left boundary or +preceding character in |hu[0]| and by storing a possible right boundary +in |bchar|. We set |j=0| if |hu[0]| is to be part of the reconstruction; +otherwise |j=1|. +The variable |s| will point to the tail of the current hlist, and +|q| will point to the node following |hb|, so that +things can be hooked up after we reconstitute the hyphenated word. + +@<Replace nodes |ha..hb| by a sequence of nodes...@>= +q=link(hb);link(hb)=null;r=link(ha);link(ha)=null;bchar=hyf_bchar; +if (is_char_node(ha)) + if (font(ha)!=hf) goto found2; + else{@+init_list=ha;init_lig=false;hu[0]=qo(character(ha)); + } +else if (type(ha)==ligature_node) + if (font(lig_char(ha))!=hf) goto found2; + else{@+init_list=lig_ptr(ha);init_lig=true;init_lft=(subtype(ha) > 1); + hu[0]=qo(character(lig_char(ha))); + if (init_list==null) if (init_lft) + {@+hu[0]=256;init_lig=false; + } /*in this case a ligature will be reconstructed from scratch*/ + free_node(ha, small_node_size); + } +else{@+ /*no punctuation found; look for left boundary*/ + if (!is_char_node(r)) if (type(r)==ligature_node) + if (subtype(r) > 1) goto found2; + j=1;s=ha;init_list=null;goto common_ending; + } +s=cur_p; /*we have |cur_p!=ha| because |type(cur_p)==glue_node|*/ +while (link(s)!=ha) s=link(s); +j=0;goto common_ending; +found2: s=ha;j=0;hu[0]=256;init_lig=false;init_list=null; +common_ending: flush_node_list(r); +@<Reconstitute nodes for the hyphenated word, inserting discretionary hyphens@>; +flush_list(init_list) + +@ We must now face the fact that the battle is not over, even though the +{\def\!{\kern-1pt}% +hyphens have been found: The process of reconstituting a word can be nontrivial +because ligatures might change when a hyphen is present. {\sl The \TeX book\/} +discusses the difficulties of the word ``difficult'', and +the discretionary material surrounding a +hyphen can be considerably more complex than that. Suppose +\.{abcdef} is a word in a font for which the only ligatures are \.{b\!c}, +\.{c\!d}, \.{d\!e}, and \.{e\!f}. If this word permits hyphenation +between \.b and \.c, the two patterns with and without hyphenation are +$\.a\,\.b\,\.-\,\.{c\!d}\,\.{e\!f}$ and $\.a\,\.{b\!c}\,\.{d\!e}\,\.f$. +Thus the insertion of a hyphen might cause effects to ripple arbitrarily +far into the rest of the word. A further complication arises if additional +hyphens appear together with such rippling, e.g., if the word in the +example just given could also be hyphenated between \.c and \.d; \TeX\ +avoids this by simply ignoring the additional hyphens in such weird cases.} + +Still further complications arise in the presence of ligatures that do not +delete the original characters. When punctuation precedes the word being +hyphenated, \TeX's method is not perfect under all possible scenarios, +because punctuation marks and letters can propagate information back and forth. +For example, suppose the original pre-hyphenation pair +\.{*a} changes to \.{*y} via a \.{\@@=:} ligature, which changes to \.{xy} +via a \.{=:\@@} ligature; if $p_{a-1}=\.x$ and $p_a=\.y$, the reconstitution +procedure isn't smart enough to obtain \.{xy} again. In such cases the +font designer should include a ligature that goes from \.{xa} to \.{xy}. + +@ The processing is facilitated by a subroutine called |reconstitute|. Given +a string of characters $x_j\ldots x_n$, there is a smallest index $m\ge j$ +such that the ``translation'' of $x_j\ldots x_n$ by ligatures and kerning +has the form $y_1\ldots y_t$ followed by the translation of $x_{m+1}\ldots x_n$, +where $y_1\ldots y_t$ is some nonempty sequence of character, ligature, and +kern nodes. We call $x_j\ldots x_m$ a ``cut prefix'' of $x_j\ldots x_n$. +For example, if $x_1x_2x_3=\.{fly}$, and if the font contains `fl' as a +ligature and a kern between `fl' and `y', then $m=2$, $t=2$, and $y_1$ will +be a ligature node for `fl' followed by an appropriate kern node~$y_2$. +In the most common case, $x_j$~forms no ligature with $x_{j+1}$ and we +simply have $m=j$, $y_1=x_j$. If $m<n$ we can repeat the procedure on +$x_{m+1}\ldots x_n$ until the entire translation has been found. + +The |reconstitute| function returns the integer $m$ and puts the nodes +$y_1\ldots y_t$ into a linked list starting at |link(hold_head)|, +getting the input $x_j\ldots x_n$ from the |hu| array. If $x_j=256$, +we consider $x_j$ to be an implicit left boundary character; in this +case |j| must be strictly less than~|n|. There is a +parameter |bchar|, which is either 256 or an implicit right boundary character +assumed to be present just following~$x_n$. (The value |hu[n+1]| is never +explicitly examined, but the algorithm imagines that |bchar| is there.) + +If there exists an index |k| in the range $j\le k\le m$ such that |hyf[k]| +is odd and such that the result of |reconstitute| would have been different +if $x_{k+1}$ had been |hchar|, then |reconstitute| sets |hyphen_passed| +to the smallest such~|k|. Otherwise it sets |hyphen_passed| to zero. + +A special convention is used in the case |j==0|: Then we assume that the +translation of |hu[0]| appears in a special list of charnodes starting at +|init_list|; moreover, if |init_lig| is |true|, then |hu[0]| will be +a ligature character, involving a left boundary if |init_lft| is |true|. +This facility is provided for cases when a hyphenated +word is preceded by punctuation (like single or double quotes) that might +affect the translation of the beginning of the word. + +@<Glob...@>= +static small_number @!hyphen_passed; /*first hyphen in a ligature, if any*/ + +@ @<Declare the function called |reconstitute|@>= +static + small_number reconstitute(small_number @!j, small_number @!n, halfword @!bchar, halfword @!hchar) +{@+ +pointer @!p; /*temporary register for list manipulation*/ +pointer @!t; /*a node being appended to*/ +four_quarters @!q; /*character information or a lig/kern instruction*/ +halfword @!cur_rh; /*hyphen character for ligature testing*/ +halfword @!test_char; /*hyphen or other character for ligature testing*/ +scaled @!w; /*amount of kerning*/ +font_index @!k; /*position of current lig/kern instruction*/ +hyphen_passed=0;t=hold_head;w=0;link(hold_head)=null; + /*at this point |ligature_present==lft_hit==rt_hit==false|*/ +@<Set up data structures with the cursor following position |j|@>; +resume: @<If there's a ligature or kern at the cursor position, update the +data structures, possibly advancing~|j|; continue until the cursor moves@>; +@<Append a ligature and/or kern to the translation; |goto resume| if the +stack of inserted ligatures is nonempty@>; +return j; +} + +@ The reconstitution procedure shares many of the global data structures +by which \TeX\ has processed the words before they were hyphenated. +There is an implied ``cursor'' between characters |cur_l| and |cur_r|; +these characters will be tested for possible ligature activity. If +|ligature_present| then |cur_l| is a ligature character formed from the +original characters following |cur_q| in the current translation list. +There is a ``ligature stack'' between the cursor and character |j+1|, +consisting of pseudo-ligature nodes linked together by their |link| fields. +This stack is normally empty unless a ligature command has created a new +character that will need to be processed later. A pseudo-ligature is +a special node having a |character| field that represents a potential +ligature and a |lig_ptr| field that points to a |char_node| or is |null|. +We have +$$|cur_r|=\cases{|character(lig_stack)|,&if |lig_stack > null|;\cr + \hbox{|qi(hu[j+1])|},&if |lig_stack==null| and |j < n|;\cr + bchar,&if |lig_stack==null| and |j==n|.\cr}$$ + +@<Glob...@>= +static halfword @!cur_l, @!cur_r; /*characters before and after the cursor*/ +static pointer @!cur_q; /*where a ligature should be detached*/ +static pointer @!lig_stack; /*unfinished business to the right of the cursor*/ +static bool @!ligature_present; /*should a ligature node be made for |cur_l|?*/ +static bool @!lft_hit, @!rt_hit; /*did we hit a ligature with a boundary character?*/ + +@ @d append_charnode_to_t(A) {@+link(t)=get_avail();t=link(t); + font(t)=hf;character(t)=A; + } +@d set_cur_r {@+if (j < n) cur_r=qi(hu[j+1]);@+else cur_r=bchar; + if (odd(hyf[j])) cur_rh=hchar;@+else cur_rh=non_char; + } + +@<Set up data structures with the cursor following position |j|@>= +cur_l=qi(hu[j]);cur_q=t; +if (j==0) + {@+ligature_present=init_lig;p=init_list; + if (ligature_present) lft_hit=init_lft; + while (p > null) + {@+append_charnode_to_t(character(p));p=link(p); + } + } +else if (cur_l < non_char) append_charnode_to_t(cur_l); +lig_stack=null;set_cur_r + +@ We may want to look at the lig/kern program twice, once for a hyphen +and once for a normal letter. (The hyphen might appear after the letter +in the program, so we'd better not try to look for both at once.) + +@<If there's a ligature or kern at the cursor position, update...@>= +if (cur_l==non_char) + {@+k=bchar_label[hf]; + if (k==non_address) goto done;@+else q=font_info[k].qqqq; + } +else{@+q=char_info(hf, cur_l); + if (char_tag(q)!=lig_tag) goto done; + k=lig_kern_start(hf, q);q=font_info[k].qqqq; + if (skip_byte(q) > stop_flag) + {@+k=lig_kern_restart(hf, q);q=font_info[k].qqqq; + } + } /*now |k| is the starting address of the lig/kern program*/ +if (cur_rh < non_char) test_char=cur_rh;@+else test_char=cur_r; +loop@+{@+if (next_char(q)==test_char) if (skip_byte(q) <= stop_flag) + if (cur_rh < non_char) + {@+hyphen_passed=j;hchar=non_char;cur_rh=non_char; + goto resume; + } + else{@+if (hchar < non_char) if (odd(hyf[j])) + {@+hyphen_passed=j;hchar=non_char; + } + if (op_byte(q) < kern_flag) + @<Carry out a ligature replacement, updating the cursor structure and +possibly advancing~|j|; |goto resume| if the cursor doesn't advance, otherwise +|goto done|@>; + w=char_kern(hf, q);goto done; /*this kern will be inserted below*/ + } + if (skip_byte(q) >= stop_flag) + if (cur_rh==non_char) goto done; + else{@+cur_rh=non_char;goto resume; + } + k=k+qo(skip_byte(q))+1;q=font_info[k].qqqq; + } +done: + +@ @d wrap_lig(A) if (ligature_present) + {@+p=new_ligature(hf, cur_l, link(cur_q)); + if (lft_hit) + {@+subtype(p)=2;lft_hit=false; + } + if (A) if (lig_stack==null) + {@+incr(subtype(p));rt_hit=false; + } + link(cur_q)=p;t=p;ligature_present=false; + } +@d pop_lig_stack {@+if (lig_ptr(lig_stack) > null) + {@+link(t)=lig_ptr(lig_stack); /*this is a charnode for |hu[j+1]|*/ + t=link(t);incr(j); + } + p=lig_stack;lig_stack=link(p);free_node(p, small_node_size); + if (lig_stack==null) set_cur_r@;@+else cur_r=character(lig_stack); + } /*if |lig_stack| isn't |null| we have |cur_rh==non_char|*/ + +@<Append a ligature and/or kern to the translation...@>= +wrap_lig(rt_hit); +if (w!=0) + {@+link(t)=new_kern(w);t=link(t);w=0; + } +if (lig_stack > null) + {@+cur_q=t;cur_l=character(lig_stack);ligature_present=true; + pop_lig_stack;goto resume; + } + +@ @<Carry out a ligature replacement, updating the cursor structure...@>= +{@+if (cur_l==non_char) lft_hit=true; +if (j==n) if (lig_stack==null) rt_hit=true; +check_interrupt; /*allow a way out in case there's an infinite ligature loop*/ +switch (op_byte(q)) { +case qi(1): case qi(5): {@+cur_l=rem_byte(q); /*\.{=:\@@}, \.{=:\@@>}*/ + ligature_present=true; + } @+break; +case qi(2): case qi(6): {@+cur_r=rem_byte(q); /*\.{\@@=:}, \.{\@@=:>}*/ + if (lig_stack > null) character(lig_stack)=cur_r; + else{@+lig_stack=new_lig_item(cur_r); + if (j==n) bchar=non_char; + else{@+p=get_avail();lig_ptr(lig_stack)=p; + character(p)=qi(hu[j+1]);font(p)=hf; + } + } + } @+break; +case qi(3): {@+cur_r=rem_byte(q); /*\.{\@@=:\@@}*/ + p=lig_stack;lig_stack=new_lig_item(cur_r);link(lig_stack)=p; + } @+break; +case qi(7): case qi(11): {@+wrap_lig(false); /*\.{\@@=:\@@>}, \.{\@@=:\@@>>}*/ + cur_q=t;cur_l=rem_byte(q);ligature_present=true; + } @+break; +default:{@+cur_l=rem_byte(q);ligature_present=true; /*\.{=:}*/ + if (lig_stack > null) pop_lig_stack@; + else if (j==n) goto done; + else{@+append_charnode_to_t(cur_r);incr(j);set_cur_r; + } + } +} +if (op_byte(q) > qi(4)) if (op_byte(q)!=qi(7)) goto done; +goto resume; +} + +@ Okay, we're ready to insert the potential hyphenations that were found. +When the following program is executed, we want to append the word +|hu[1 dotdot hn]| after node |ha|, and node |q| should be appended to the result. +During this process, the variable |i| will be a temporary +index into |hu|; the variable |j| will be an index to our current position +in |hu|; the variable |l| will be the counterpart of |j|, in a discretionary +branch; the variable |r| will point to new nodes being created; and +we need a few new local variables: + +@<Local variables for hyph...@>= +pointer @!major_tail, @!minor_tail; /*the end of lists in the main and + discretionary branches being reconstructed*/ +ASCII_code @!c; /*character temporarily replaced by a hyphen*/ +int @!c_loc; /*where that character came from*/ +int @!r_count; /*replacement count for discretionary*/ +pointer @!hyf_node; /*the hyphen, if it exists*/ + +@ When the following code is performed, |hyf[0]| and |hyf[hn]| will be zero. + +@<Reconstitute nodes for the hyphenated word...@>= +@/do@+{l=j;j=reconstitute(j, hn, bchar, qi(hyf_char))+1; +if (hyphen_passed==0) + {@+link(s)=link(hold_head); + while (link(s) > null) s=link(s); + if (odd(hyf[j-1])) + {@+l=j;hyphen_passed=j-1;link(hold_head)=null; + } + } +if (hyphen_passed > 0) + @<Create and append a discretionary node as an alternative to the unhyphenated +word, and continue to develop both branches until they become equivalent@>; +}@+ while (!(j > hn)); +link(s)=q + +@ In this repeat loop we will insert another discretionary if |hyf[j-1]| is +odd, when both branches of the previous discretionary end at position |j-1|. +Strictly speaking, we aren't justified in doing this, because we don't know +that a hyphen after |j-1| is truly independent of those branches. But in almost +all applications we would rather not lose a potentially valuable hyphenation +point. (Consider the word `difficult', where the letter `c' is in position |j|.) + +@d advance_major_tail {@+major_tail=link(major_tail);incr(r_count); + } + +@<Create and append a discretionary node as an alternative...@>= +@/do@+{r=get_node(small_node_size); +link(r)=link(hold_head);type(r)=disc_node; +major_tail=r;r_count=0; +while (link(major_tail) > null) advance_major_tail; +i=hyphen_passed;hyf[i]=0; +@<Put the \(c)characters |hu[l..i]| and a hyphen into |pre_break(r)|@>; +@<Put the \(c)characters |hu[i+1..]| into |post_break(r)|, appending to this +list and to |major_tail| until synchronization has been achieved@>; +@<Move pointer |s| to the end of the current list, and set |replace_count(r)| +appropriately@>; +hyphen_passed=j-1;link(hold_head)=null; +}@+ while (!(!odd(hyf[j-1]))) + +@ The new hyphen might combine with the previous character via ligature +or kern. At this point we have |l-1 <= i < j| and |i < hn|. + +@<Put the \(c)characters |hu[l..i]| and a hyphen into |pre_break(r)|@>= +minor_tail=null;pre_break(r)=null;hyf_node=new_character(hf, hyf_char); +if (hyf_node!=null) + {@+incr(i);c=hu[i];hu[i]=hyf_char;free_avail(hyf_node); + } +while (l <= i) + {@+l=reconstitute(l, i, font_bchar[hf], non_char)+1; + if (link(hold_head) > null) + {@+if (minor_tail==null) pre_break(r)=link(hold_head); + else link(minor_tail)=link(hold_head); + minor_tail=link(hold_head); + while (link(minor_tail) > null) minor_tail=link(minor_tail); + } + } +if (hyf_node!=null) + {@+hu[i]=c; /*restore the character in the hyphen position*/ + l=i;decr(i); + } + +@ The synchronization algorithm begins with |l==i+1 <= j|. + +@<Put the \(c)characters |hu[i+1..]| into |post_break(r)|...@>= +minor_tail=null;post_break(r)=null;c_loc=0; +if (bchar_label[hf]!=non_address) /*put left boundary at beginning of new line*/ + {@+decr(l);c=hu[l];c_loc=l;hu[l]=256; + } +while (l < j) + {@+@/do@+{l=reconstitute(l, hn, bchar, non_char)+1; + if (c_loc > 0) + {@+hu[c_loc]=c;c_loc=0; + } + if (link(hold_head) > null) + {@+if (minor_tail==null) post_break(r)=link(hold_head); + else link(minor_tail)=link(hold_head); + minor_tail=link(hold_head); + while (link(minor_tail) > null) minor_tail=link(minor_tail); + } + }@+ while (!(l >= j)); + while (l > j) + @<Append characters of |hu[j..]| to |major_tail|, advancing~|j|@>; + } + +@ @<Append characters of |hu[j..]|...@>= +{@+j=reconstitute(j, hn, bchar, non_char)+1; +link(major_tail)=link(hold_head); +while (link(major_tail) > null) advance_major_tail; +} + +@ Ligature insertion can cause a word to grow exponentially in size. Therefore +we must test the size of |r_count| here, even though the hyphenated text +was at most 63 characters long. + +@<Move pointer |s| to the end of the current list...@>= +if (r_count > 127) /*we have to forget the discretionary hyphen*/ + {@+link(s)=link(r);link(r)=null;flush_node_list(r); + } +else{@+link(s)=r;replace_count(r)=r_count; + } +s=major_tail + +@* Hyphenation. +When a word |hc[1 dotdot hn]| has been set up to contain a candidate for hyphenation, +\TeX\ first looks to see if it is in the user's exception dictionary. If not, +hyphens are inserted based on patterns that appear within the given word, +using an algorithm due to Frank~M. Liang. +@^Liang, Franklin Mark@> + +Let's consider Liang's method first, since it is much more interesting than the +exception-lookup routine. The algorithm begins by setting |hyf[j]| to zero +for all |j|, and invalid characters are inserted into |hc[0]| +and |hc[hn+1]| to serve as delimiters. Then a reasonably fast method is +used to see which of a given set of patterns occurs in the word +|hc[0 dotdot(hn+1)]|. Each pattern $p_1\ldots p_k$ of length |k| has an associated +sequence of |k+1| numbers $n_0\ldots n_k$; and if the pattern occurs in +|hc[(j+1)dotdot(j+k)]|, \TeX\ will set |hyf[j+i]=@tmax@>(hyf[j+i],@t$n\_i$@>)| for +|0 <= i <= k|. After this has been done for each pattern that occurs, a +discretionary hyphen will be inserted between |hc[j]| and |hc[j+1]| when +|hyf[j]| is odd, as we have already seen. + +The set of patterns $p_1\ldots p_k$ and associated numbers $n_0\ldots n_k$ +depends, of course, on the language whose words are being hyphenated, and +on the degree of hyphenation that is desired. A method for finding +appropriate |p|'s and |n|'s, from a given dictionary of words and acceptable +hyphenations, is discussed in Liang's Ph.D. thesis (Stanford University, +1983); \TeX\ simply starts with the patterns and works from there. + +@ The patterns are stored in a compact table that is also efficient for +retrieval, using a variant of ``trie memory'' [cf.\ {\sl The Art of +Computer Programming \bf3} (1973), 481--505]. We can find each pattern +$p_1\ldots p_k$ by letting $z_0$ be one greater than the relevant language +index and then, for |1 <= i <= k|, +setting |@t$z\_i$@>=trie_link@t$(z\_{i-1})+p\_i$@>|; the pattern will be +identified by the number $z_k$. Since all the pattern information is +packed together into a single |trie_link| array, it is necessary to +prevent confusion between the data from inequivalent patterns, so another +table is provided such that |trie_char@t$(z\_i)=p\_i$@>| for all |i|. There +is also a table |trie_op|$(z_k)$ to identify the numbers $n_0\ldots n_k$ +associated with $p_1\ldots p_k$. + +Comparatively few different number sequences $n_0\ldots n_k$ actually occur, +since most of the |n|'s are generally zero. Therefore the number sequences +are encoded in such a way that |trie_op|$(z_k)$ is only one byte long. +If |trie_op(@t$z\_k$@>)!=min_quarterword|, when $p_1\ldots p_k$ has matched +the letters in |hc[(l-k+1)dotdot l@,]| of language |t|, +we perform all of the required operations +for this pattern by carrying out the following little program: Set +|v=trie_op(@t$z\_k$@>)|. Then set |v=v+op_start[t]|, +|hyf[l-hyf_distance[v]]=@tmax@>(hyf[l-hyf_distance[v]], hyf_num[v])|, +and |v=hyf_next[v]|; repeat, if necessary, until |v==min_quarterword|. + +@<Types...@>= +typedef int32_t trie_pointer; /*an index into |trie|*/ + +@ @d trie_link(A) trie[A].rh /*``downward'' link in a trie*/ +@d trie_char(A) trie[A].b1 /*character matched at this trie location*/ +@d trie_op(A) trie[A].b0 /*program for hyphenation at this trie location*/ + +@<Glob...@>= +static two_halves @!trie[trie_size+1]; /*|trie_link|, |trie_char|, |trie_op|*/ +static small_number @!hyf_distance0[trie_op_size], + *const @!hyf_distance = @!hyf_distance0-1; /*position |k-j| of $n_j$*/ +static small_number @!hyf_num0[trie_op_size], + *const @!hyf_num = @!hyf_num0-1; /*value of $n_j$*/ +static quarterword @!hyf_next0[trie_op_size], + *const @!hyf_next = @!hyf_next0-1; /*continuation code*/ +static uint16_t @!op_start[256]; /*offset for current language*/ + +@ @<Local variables for hyph...@>= +trie_pointer @!z; /*an index into |trie|*/ +int @!v; /*an index into |hyf_distance|, etc.*/ + +@ Assuming that these auxiliary tables have been set up properly, the +hyphenation algorithm is quite short. In the following code we set |hc[hn+2]| +to the impossible value 256, in order to guarantee that |hc[hn+3]| will +never be fetched. + +@<Find hyphen locations for the word in |hc|...@>= +for (j=0; j<=hn; j++) hyf[j]=0; +@<Look for the word |hc[1..hn]| in the exception table, and |goto found| (with +|hyf| containing the hyphens) if an entry is found@>; +if (trie_char(cur_lang+1)!=qi(cur_lang)) return; /*no patterns for |cur_lang|*/ +hc[0]=0;hc[hn+1]=0;hc[hn+2]=256; /*insert delimiters*/ +for (j=0; j<=hn-r_hyf+1; j++) + {@+z=trie_link(cur_lang+1)+hc[j];l=j; + while (hc[l]==qo(trie_char(z))) + {@+if (trie_op(z)!=min_quarterword) + @<Store \(m)maximum values in the |hyf| table@>; + incr(l);z=trie_link(z)+hc[l]; + } + } +found: for (j=0; j<=l_hyf-1; j++) hyf[j]=0; +for (j=0; j<=r_hyf-1; j++) hyf[hn-j]=0 + +@ @<Store \(m)maximum values in the |hyf| table@>= +{@+v=trie_op(z); +@/do@+{v=v+op_start[cur_lang];i=l-hyf_distance[v]; +if (hyf_num[v] > hyf[i]) hyf[i]=hyf_num[v]; +v=hyf_next[v]; +}@+ while (!(v==min_quarterword)); +} + +@ The exception table that is built by \TeX's \.{\\hyphenation} primitive is +organized as an ordered hash table [cf.\ Amble and Knuth, {\sl The Computer +@^Amble, Ole@> @^Knuth, Donald Ervin@> +Journal\/ \bf17} (1974), 135--142] using linear probing. If $\alpha$ and +$\beta$ are words, we will say that $\alpha<\beta$ if $\vert\alpha\vert< +\vert\beta\vert$ or if $\vert\alpha\vert=\vert\beta\vert$ and +$\alpha$ is lexicographically smaller than $\beta$. (The notation $\vert +\alpha\vert$ stands for the length of $\alpha$.) The idea of ordered hashing +is to arrange the table so that a given word $\alpha$ can be sought by computing +a hash address $h=h(\alpha)$ and then looking in table positions |h|, |h-1|, +\dots, until encountering the first word $\le\alpha$. If this word is +different from $\alpha$, we can conclude that $\alpha$ is not in the table. + +The words in the table point to lists in |mem| that specify hyphen positions +in their |info| fields. The list for $c_1\ldots c_n$ contains the number |k| if +the word $c_1\ldots c_n$ has a discretionary hyphen between $c_k$ and +$c_{k+1}$. + +@<Types...@>= +typedef int16_t hyph_pointer; /*an index into the ordered hash table*/ + +@ @<Glob...@>= +static str_number @!hyph_word[hyph_size+1]; /*exception words*/ +static pointer @!hyph_list[hyph_size+1]; /*lists of hyphen positions*/ +static hyph_pointer @!hyph_count; /*the number of words in the exception dictionary*/ + +@ @<Local variables for init...@>= +int @!z; /*runs through the exception dictionary*/ + +@ @<Set init...@>= +for (z=0; z<=hyph_size; z++) + {@+hyph_word[z]=0;hyph_list[z]=null; + } +hyph_count=0; + +@ The algorithm for exception lookup is quite simple, as soon as we have +a few more local variables to work with. + +@<Local variables for hyph...@>= +hyph_pointer @!h; /*an index into |hyph_word| and |hyph_list|*/ +str_number @!k; /*an index into |str_start|*/ +pool_pointer @!u; /*an index into |str_pool|*/ + +@ First we compute the hash code |h|, then we search until we either +find the word or we don't. Words from different languages are kept +separate by appending the language code to the string. + +@<Look for the word |hc[1...@>= +h=hc[1];incr(hn);hc[hn]=cur_lang; +for (j=2; j<=hn; j++) h=(h+h+hc[j])%hyph_size; +loop@+{@+@<If the string |hyph_word[h]| is less than \(hc)|hc[1..hn]|, |goto +not_found|; but if the two strings are equal, set |hyf| to the hyphen positions +and |goto found|@>; + if (h > 0) decr(h);@+else h=hyph_size; + } +not_found: decr(hn) + +@ @<If the string |hyph_word[h]| is less than \(hc)...@>= +k=hyph_word[h];if (k==0) goto not_found; +if (length(k) < hn) goto not_found; +if (length(k)==hn) + {@+j=1;u=str_start[k]; + @/do@+{if (so(str_pool[u]) < hc[j]) goto not_found; + if (so(str_pool[u]) > hc[j]) goto done; + incr(j);incr(u); + }@+ while (!(j > hn)); + @<Insert hyphens as specified in |hyph_list[h]|@>; + decr(hn);goto found; + } +done: + +@ @<Insert hyphens as specified...@>= +s=hyph_list[h]; +while (s!=null) + {@+hyf[info(s)]=1;s=link(s); + } + +@ @<Search |hyph_list| for pointers to |p|@>= +for (q=0; q<=hyph_size; q++) + {@+if (hyph_list[q]==p) + {@+print_nl("HYPH(");print_int(q);print_char(')'); + } + } + +@ We have now completed the hyphenation routine, so the |line_break| procedure +is finished at last. Since the hyphenation exception table is fresh in our +minds, it's a good time to deal with the routine that adds new entries to it. + +When \TeX\ has scanned `\.{\\hyphenation}', it calls on a procedure named +|new_hyph_exceptions| to do the right thing. + +@d set_cur_lang if (language <= 0) cur_lang=0; + else if (language > 255) cur_lang=0; + else cur_lang=language + +@p static void new_hyph_exceptions(void) /*enters new exceptions*/ +{@+ +int n; /*length of current word; not always a |small_number|*/ +int @!j; /*an index into |hc|*/ +hyph_pointer @!h; /*an index into |hyph_word| and |hyph_list|*/ +str_number @!k; /*an index into |str_start|*/ +pointer @!p; /*head of a list of hyphen positions*/ +pointer @!q; /*used when creating a new node for list |p|*/ +str_number @!s, @!t; /*strings being compared or stored*/ +pool_pointer @!u, @!v; /*indices into |str_pool|*/ +scan_left_brace(); /*a left brace must follow \.{\\hyphenation}*/ +set_cur_lang; +#ifdef @!INIT +if (trie_not_ready) + {@+hyph_index=0;goto not_found1; + } +#endif +set_hyph_index; +not_found1: +@<Enter as many hyphenation exceptions as are listed, until coming to a right +brace; then |return|@>; +} + +@ @<Enter as many...@>= +n=0;p=null; +loop@+{@+get_x_token(); + reswitch: switch (cur_cmd) { + case letter: case other_char: case char_given: @<Append a new letter or +hyphen@>@;@+break; + case char_num: {@+scan_char_num();cur_chr=cur_val;cur_cmd=char_given; + goto reswitch; + } + case spacer: case right_brace: {@+if (n > 1) @<Enter a hyphenation exception@>; + if (cur_cmd==right_brace) return; + n=0;p=null; + } @+break; + default:@<Give improper \.{\\hyphenation} error@>@; + } + } + +@ @<Give improper \.{\\hyph...@>= +{@+print_err("Improper ");print_esc("hyphenation"); +@.Improper \\hyphenation...@> + print(" will be flushed"); +help2("Hyphenation exceptions must contain only letters",@/ + "and hyphens. But continue; I'll forgive and forget."); +error(); +} + +@ @<Append a new letter or hyphen@>= +if (cur_chr=='-') @<Append the value |n| to list |p|@>@; +else{@+set_lc_code(cur_chr); + if (hc[0]==0) + {@+print_err("Not a letter"); +@.Not a letter@> + help2("Letters in \\hyphenation words must have \\lccode>0.",@/ + "Proceed; I'll ignore the character I just read."); + error(); + } + else if (n < 63) + {@+incr(n);hc[n]=hc[0]; + } + } + +@ @<Append the value |n| to list |p|@>= +{@+if (n < 63) + {@+q=get_avail();link(q)=p;info(q)=n;p=q; + } +} + +@ @<Enter a hyphenation exception@>= +{@+incr(n);hc[n]=cur_lang;str_room(n);h=0; +for (j=1; j<=n; j++) + {@+h=(h+h+hc[j])%hyph_size; + append_char(hc[j]); + } +s=make_string(); +@<Insert the \(p)pair |(s,p)| into the exception table@>; +} + +@ @<Insert the \(p)pair |(s,p)|...@>= +if (hyph_count==hyph_size) overflow("exception dictionary", hyph_size); +@:TeX capacity exceeded exception dictionary}{\quad exception dictionary@> +incr(hyph_count); +while (hyph_word[h]!=0) + {@+@<If the string |hyph_word[h]| is less than \(or)or equal to |s|, interchange +|(hyph_word[h],hyph_list[h])| with |(s,p)|@>; + if (h > 0) decr(h);@+else h=hyph_size; + } +hyph_word[h]=s;hyph_list[h]=p + +@ @<If the string |hyph_word[h]| is less than \(or)...@>= +k=hyph_word[h]; +if (length(k) < length(s)) goto found; +if (length(k) > length(s)) goto not_found; +u=str_start[k];v=str_start[s]; +@/do@+{if (str_pool[u] < str_pool[v]) goto found; +if (str_pool[u] > str_pool[v]) goto not_found; +incr(u);incr(v); +}@+ while (!(u==str_start[k+1])); +found: q=hyph_list[h];hyph_list[h]=p;p=q;@/ +t=hyph_word[h];hyph_word[h]=s;s=t; +not_found: + +@* Initializing the hyphenation tables. +The trie for \TeX's hyphenation algorithm is built from a sequence of +patterns following a \.{\\patterns} specification. Such a specification +is allowed only in \.{INITEX}, since the extra memory for auxiliary tables +and for the initialization program itself would only clutter up the +production version of \TeX\ with a lot of deadwood. + +The first step is to build a trie that is linked, instead of packed +into sequential storage, so that insertions are readily made. +After all patterns have been processed, \.{INITEX} +compresses the linked trie by identifying common subtries. Finally the +trie is packed into the efficient sequential form that the hyphenation +algorithm actually uses. + +@<Declare subprocedures for |line_break|@>= +#ifdef @!INIT +@<Declare procedures for preprocessing hyphenation patterns@>@; +#endif + +@ Before we discuss trie building in detail, let's consider the simpler +problem of creating the |hyf_distance|, |hyf_num|, and |hyf_next| arrays. + +Suppose, for example, that \TeX\ reads the pattern `\.{ab2cde1}'. This is +a pattern of length 5, with $n_0\ldots n_5=0\,0\,2\,0\,0\,1$ in the +notation above. We want the corresponding |trie_op| code |v| to have +|hyf_distance[v]==3|, |hyf_num[v]==2|, and |hyf_next[v]==@t$v^\prime$@>|, +where the auxiliary |trie_op| code $v^\prime$ has +|hyf_distance[@t$v^\prime$@>]==0|, |hyf_num[@t$v^\prime$@>]==1|, and +|hyf_next[@t$v^\prime$@>]==min_quarterword|. + +\TeX\ computes an appropriate value |v| with the |new_trie_op| subroutine +below, by setting +$$\hbox{|@t$v^\prime$@>=new_trie_op(0, 1, min_quarterword)|,\qquad +|v=new_trie_op(3, 2,@t$v^\prime$@>)|.}$$ +This subroutine looks up its three +parameters in a special hash table, assigning a new value only if these +three have not appeared before for the current language. + +The hash table is called |trie_op_hash|, and the number of entries it contains +is |trie_op_ptr|. + +@<Glob...@>= +#ifdef @!INIT +static uint16_t @!trie_op_hash0[trie_op_size+trie_op_size+1], + *const @!trie_op_hash = @!trie_op_hash0+trie_op_size; + /*trie op codes for quadruples*/ +static quarterword @!trie_used[256]; + /*largest opcode used so far for this language*/ +static ASCII_code @!trie_op_lang0[trie_op_size], + *const @!trie_op_lang = @!trie_op_lang0-1; + /*language part of a hashed quadruple*/ +static quarterword @!trie_op_val0[trie_op_size], + *const @!trie_op_val = @!trie_op_val0-1; + /*opcode corresponding to a hashed quadruple*/ +static int @!trie_op_ptr; /*number of stored ops so far*/ +#endif + +@ It's tempting to remove the |overflow| stops in the following procedure; +|new_trie_op| could return |min_quarterword| (thereby simply ignoring +part of a hyphenation pattern) instead of aborting the job. However, that would +lead to different hyphenation results on different installations of \TeX\ +using the same patterns. The |overflow| stops are necessary for portability +of patterns. + +@<Declare procedures for preprocessing hyph...@>= +static quarterword new_trie_op(small_number @!d, small_number @!n, quarterword @!v) +{@+ +int h; /*trial hash location*/ +quarterword @!u; /*trial op code*/ +int @!l; /*pointer to stored data*/ +h=abs(n+313*d+361*v+1009*cur_lang)%(trie_op_size+trie_op_size) + -trie_op_size; +loop@+{@+l=trie_op_hash[h]; + if (l==0) /*empty position found for a new op*/ + {@+if (trie_op_ptr==trie_op_size) + overflow("pattern memory ops", trie_op_size); + u=trie_used[cur_lang]; + if (u==max_quarterword) + overflow("pattern memory ops per language", + max_quarterword-min_quarterword); + incr(trie_op_ptr);incr(u);trie_used[cur_lang]=u; + hyf_distance[trie_op_ptr]=d; + hyf_num[trie_op_ptr]=n;hyf_next[trie_op_ptr]=v; + trie_op_lang[trie_op_ptr]=cur_lang;trie_op_hash[h]=trie_op_ptr; + trie_op_val[trie_op_ptr]=u;return u; + } + if ((hyf_distance[l]==d)&&(hyf_num[l]==n)&&(hyf_next[l]==v) + &&(trie_op_lang[l]==cur_lang)) + {@+return trie_op_val[l]; + } + if (h > -trie_op_size) decr(h);@+else h=trie_op_size; + } +} + +@ After |new_trie_op| has compressed the necessary opcode information, +plenty of information is available to unscramble the data into the +final form needed by our hyphenation algorithm. + +@<Sort \(t)the hyphenation op tables into proper order@>= +op_start[0]=-min_quarterword; +for (j=1; j<=255; j++) op_start[j]=op_start[j-1]+qo(trie_used[j-1]); +for (j=1; j<=trie_op_ptr; j++) + trie_op_hash[j]=op_start[trie_op_lang[j]]+trie_op_val[j]; /*destination*/ +for (j=1; j<=trie_op_ptr; j++) while (trie_op_hash[j] > j) + {@+k=trie_op_hash[j];@/ + t=hyf_distance[k];hyf_distance[k]=hyf_distance[j];hyf_distance[j]=t;@/ + t=hyf_num[k];hyf_num[k]=hyf_num[j];hyf_num[j]=t;@/ + t=hyf_next[k];hyf_next[k]=hyf_next[j];hyf_next[j]=t;@/ + trie_op_hash[j]=trie_op_hash[k];trie_op_hash[k]=k; + } + +@ Before we forget how to initialize the data structures that have been +mentioned so far, let's write down the code that gets them started. + +@<Initialize table entries...@>= +for (k=-trie_op_size; k<=trie_op_size; k++) trie_op_hash[k]=0; +for (k=0; k<=255; k++) trie_used[k]=min_quarterword; +trie_op_ptr=0; + +@ The linked trie that is used to preprocess hyphenation patterns appears +in several global arrays. Each node represents an instruction of the form +``if you see character |c|, then perform operation |o|, move to the +next character, and go to node |l|; otherwise go to node |r|.'' +The four quantities |c|, |o|, |l|, and |r| are stored in four arrays +|trie_c|, |trie_o|, |trie_l|, and |trie_r|. The root of the trie +is |trie_l[0]|, and the number of nodes is |trie_ptr|. Null trie +pointers are represented by zero. To initialize the trie, we simply +set |trie_l[0]| and |trie_ptr| to zero. We also set |trie_c[0]| to some +arbitrary value, since the algorithm may access it. + +The algorithms maintain the condition +$$\hbox{|trie_c[trie_r[z]] > trie_c[z]|\qquad +whenever |z!=0| and |trie_r[z]!=0|};$$ in other words, sibling nodes are +ordered by their |c| fields. + +@d trie_root trie_l[0] /*root of the linked trie*/ + +@<Glob...@>= +#ifdef @!INIT +static packed_ASCII_code @!trie_c[trie_size+1]; + /*characters to match*/ +@t\hskip10pt@>static quarterword @!trie_o[trie_size+1]; + /*operations to perform*/ +@t\hskip10pt@>static trie_pointer @!trie_l[trie_size+1]; + /*left subtrie links*/ +@t\hskip10pt@>static trie_pointer @!trie_r[trie_size+1]; + /*right subtrie links*/ +@t\hskip10pt@>static trie_pointer @!trie_ptr; /*the number of nodes in the trie*/ +@t\hskip10pt@>static trie_pointer @!trie_hash[trie_size+1]; + /*used to identify equivalent subtries*/ +#endif + +@ Let us suppose that a linked trie has already been constructed. +Experience shows that we can often reduce its size by recognizing common +subtries; therefore another hash table is introduced for this purpose, +somewhat similar to |trie_op_hash|. The new hash table will be +initialized to zero. + +The function |trie_node(p)| returns |p| if |p| is distinct from other nodes +that it has seen, otherwise it returns the number of the first equivalent +node that it has seen. + +Notice that we might make subtries equivalent even if they correspond to +patterns for different languages, in which the trie ops might mean quite +different things. That's perfectly all right. + +@<Declare procedures for preprocessing hyph...@>= +static trie_pointer trie_node(trie_pointer @!p) /*converts + to a canonical form*/ +{@+ +trie_pointer h; /*trial hash location*/ +trie_pointer @!q; /*trial trie node*/ +h=abs(trie_c[p]+1009*trie_o[p]+@| + 2718*trie_l[p]+3142*trie_r[p])%trie_size; +loop@+{@+q=trie_hash[h]; + if (q==0) + {@+trie_hash[h]=p;return p; + } + if ((trie_c[q]==trie_c[p])&&(trie_o[q]==trie_o[p])&&@| + (trie_l[q]==trie_l[p])&&(trie_r[q]==trie_r[p])) + {@+return q; + } + if (h > 0) decr(h);@+else h=trie_size; + } +} + +@ A neat recursive procedure is now able to compress a trie by +traversing it and applying |trie_node| to its nodes in ``bottom up'' +fashion. We will compress the entire trie by clearing |trie_hash| to +zero and then saying `|trie_root=compress_trie(trie_root)|'. +@^recursion@> + +@<Declare procedures for preprocessing hyph...@>= +static trie_pointer compress_trie(trie_pointer @!p) +{@+if (p==0) return 0; +else{@+trie_l[p]=compress_trie(trie_l[p]); + trie_r[p]=compress_trie(trie_r[p]); + return trie_node(p); + } +} + +@ The compressed trie will be packed into the |trie| array using a +``top-down first-fit'' procedure. This is a little tricky, so the reader +should pay close attention: The |trie_hash| array is cleared to zero +again and renamed |trie_ref| for this phase of the operation; later on, +|trie_ref[p]| will be nonzero only if the linked trie node |p| is the +smallest character +in a family and if the characters |c| of that family have been allocated to +locations |trie_ref[p]+c| in the |trie| array. Locations of |trie| that +are in use will have |trie_link==0|, while the unused holes in |trie| +will be doubly linked with |trie_link| pointing to the next larger vacant +location and |trie_back| pointing to the next smaller one. This double +linking will have been carried out only as far as |trie_max|, where +|trie_max| is the largest index of |trie| that will be needed. +To save time at the low end of the trie, we maintain array entries +|trie_min[c]| pointing to the smallest hole that is greater than~|c|. +Another array |trie_taken| tells whether or not a given location is +equal to |trie_ref[p]| for some |p|; this array is used to ensure that +distinct nodes in the compressed trie will have distinct |trie_ref| +entries. + +@d trie_ref trie_hash /*where linked trie families go into |trie|*/ +@d trie_back(A) trie[A].lh /*backward links in |trie| holes*/ + +@<Glob...@>= +#ifdef @!INIT +static bool @!trie_taken0[trie_size], + *const @!trie_taken = @!trie_taken0-1; + /*does a family start here?*/ +@t\hskip10pt@>static trie_pointer @!trie_min[256]; + /*the first possible slot for each character*/ +@t\hskip10pt@>static trie_pointer @!trie_max; /*largest location used in |trie|*/ +@t\hskip10pt@>static bool @!trie_not_ready; /*is the trie still in linked form?*/ +#endif + +@ Each time \.{\\patterns} appears, it contributes further patterns to +the future trie, which will be built only when hyphenation is attempted or +when a format file is dumped. The boolean variable |trie_not_ready| +will change to |false| when the trie is compressed; this will disable +further patterns. + +@<Initialize table entries...@>= +trie_not_ready=true;trie_root=0;trie_c[0]=si(0);trie_ptr=0; + +@ Here is how the trie-compression data structures are initialized. +If storage is tight, it would be possible to overlap |trie_op_hash|, +|trie_op_lang|, and |trie_op_val| with |trie|, |trie_hash|, and |trie_taken|, +because we finish with the former just before we need the latter. + +@<Get ready to compress the trie@>= +@<Sort \(t)the hyphenation...@>; +for (p=0; p<=trie_size; p++) trie_hash[p]=0; +hyph_root=compress_trie(hyph_root); +trie_root=compress_trie(trie_root); /*identify equivalent subtries*/ +for (p=0; p<=trie_ptr; p++) trie_ref[p]=0; +for (p=0; p<=255; p++) trie_min[p]=p+1; +trie_link(0)=1;trie_max=0 + +@ The |first_fit| procedure finds the smallest hole |z| in |trie| such that +a trie family starting at a given node |p| will fit into vacant positions +starting at |z|. If |c==trie_c[p]|, this means that location |z-c| must +not already be taken by some other family, and that |z-c+@t$c^\prime$@>| +must be vacant for all characters $c^\prime$ in the family. The procedure +sets |trie_ref[p]| to |z-c| when the first fit has been found. + +@<Declare procedures for preprocessing hyph...@>= +static void first_fit(trie_pointer @!p) /*packs a family into |trie|*/ +{@+ +trie_pointer h; /*candidate for |trie_ref[p]|*/ +trie_pointer @!z; /*runs through holes*/ +trie_pointer @!q; /*runs through the family starting at |p|*/ +ASCII_code @!c; /*smallest character in the family*/ +trie_pointer @!l, @!r; /*left and right neighbors*/ +int @!ll; /*upper limit of |trie_min| updating*/ +c=so(trie_c[p]); +z=trie_min[c]; /*get the first conceivably good hole*/ +loop@+{@+h=z-c;@/ + @<Ensure that |trie_max>=h+256|@>; + if (trie_taken[h]) goto not_found; + @<If all characters of the family fit relative to |h|, then |goto found|,\30\ +otherwise |goto not_found|@>; + not_found: z=trie_link(z); /*move to the next hole*/ + } +found: @<Pack the family into |trie| relative to |h|@>; +} + +@ By making sure that |trie_max| is at least |h+256|, we can be sure that +|trie_max > z|, since |h==z-c|. It follows that location |trie_max| will +never be occupied in |trie|, and we will have |trie_max >= trie_link(z)|. + +@<Ensure that |trie_max>=h+256|@>= +if (trie_max < h+256) + {@+if (trie_size <= h+256) overflow("pattern memory", trie_size); +@:TeX capacity exceeded pattern memory}{\quad pattern memory@> + @/do@+{incr(trie_max);trie_taken[trie_max]=false; + trie_link(trie_max)=trie_max+1;trie_back(trie_max)=trie_max-1; + }@+ while (!(trie_max==h+256)); + } + +@ @<If all characters of the family fit relative to |h|...@>= +q=trie_r[p]; +while (q > 0) + {@+if (trie_link(h+so(trie_c[q]))==0) goto not_found; + q=trie_r[q]; + } +goto found + +@ @<Pack the family into |trie| relative to |h|@>= +trie_taken[h]=true;trie_ref[p]=h;q=p; +@/do@+{z=h+so(trie_c[q]);l=trie_back(z);r=trie_link(z); +trie_back(r)=l;trie_link(l)=r;trie_link(z)=0; +if (l < 256) + {@+if (z < 256) ll=z;@+else ll=256; + @/do@+{trie_min[l]=r;incr(l); + }@+ while (!(l==ll)); + } +q=trie_r[q]; +}@+ while (!(q==0)) + +@ To pack the entire linked trie, we use the following recursive procedure. +@^recursion@> + +@<Declare procedures for preprocessing hyph...@>= +static void trie_pack(trie_pointer @!p) /*pack subtries of a family*/ +{@+trie_pointer q; /*a local variable that need not be saved on recursive calls*/ +@/do@+{q=trie_l[p]; +if ((q > 0)&&(trie_ref[q]==0)) + {@+first_fit(q);trie_pack(q); + } +p=trie_r[p]; +}@+ while (!(p==0)); +} + +@ When the whole trie has been allocated into the sequential table, we +must go through it once again so that |trie| contains the correct +information. Null pointers in the linked trie will be represented by the +value~0, which properly implements an ``empty'' family. + +@<Move the data into |trie|@>= +h.rh=0;h.b0=min_quarterword;h.b1=min_quarterword; /*|trie_link=0|, + |trie_op=min_quarterword|, |trie_char=qi(0)|*/ +if (trie_max==0) /*no patterns were given*/ + {@+for (r=0; r<=256; r++) trie[r]=h; + trie_max=256; + } +else{@+if (hyph_root > 0) trie_fix(hyph_root); + if (trie_root > 0) trie_fix(trie_root); /*this fixes the non-holes in |trie|*/ + r=0; /*now we will zero out all the holes*/ + @/do@+{s=trie_link(r);trie[r]=h;r=s; + }@+ while (!(r > trie_max)); + } +trie_char(0)=qi('?'); /*make |trie_char(c)!=c| for all |c|*/ + +@ The fixing-up procedure is, of course, recursive. Since the linked trie +usually has overlapping subtries, the same data may be moved several +times; but that causes no harm, and at most as much work is done as it +took to build the uncompressed trie. +@^recursion@> + +@<Declare procedures for preprocessing hyph...@>= +static void trie_fix(trie_pointer @!p) /*moves |p| and its siblings into |trie|*/ +{@+trie_pointer q; /*a local variable that need not be saved on recursive calls*/ +ASCII_code @!c; /*another one that need not be saved*/ +trie_pointer @!z; /*|trie| reference; this local variable must be saved*/ +z=trie_ref[p]; +@/do@+{q=trie_l[p];c=so(trie_c[p]); +trie_link(z+c)=trie_ref[q];trie_char(z+c)=qi(c);trie_op(z+c)=trie_o[p]; +if (q > 0) trie_fix(q); +p=trie_r[p]; +}@+ while (!(p==0)); +} + +@ Now let's go back to the easier problem, of building the linked +trie. When \.{INITEX} has scanned the `\.{\\patterns}' control +sequence, it calls on |new_patterns| to do the right thing. + +@<Declare procedures for preprocessing hyph...@>= +static void new_patterns(void) /*initializes the hyphenation pattern data*/ +{@+ +int k, @!l; /*indices into |hc| and |hyf|; + not always in |small_number| range*/ +bool @!digit_sensed; /*should the next digit be treated as a letter?*/ +quarterword @!v; /*trie op code*/ +trie_pointer @!p, @!q; /*nodes of trie traversed during insertion*/ +bool @!first_child; /*is |p==trie_l[q]|?*/ +int @!c; /*character being inserted*/ +if (trie_not_ready) + {@+set_cur_lang;scan_left_brace(); /*a left brace must follow \.{\\patterns}*/ + @<Enter all of the patterns into a linked trie, until coming to a right +brace@>; + if (saving_hyph_codes > 0) + @<Store hyphenation codes for current language@>; + } +else{@+print_err("Too late for ");print_esc("patterns"); + help1("All patterns must be given before typesetting begins."); + error();link(garbage)=scan_toks(false, false);flush_list(def_ref); + } +} + +@ Novices are not supposed to be using \.{\\patterns}, so the error +messages are terse. (Note that all error messages appear in \TeX's string +pool, even if they are used only by \.{INITEX}.) + +@<Enter all of the patterns into a linked trie...@>= +k=0;hyf[0]=0;digit_sensed=false; +loop@+{@+get_x_token(); + switch (cur_cmd) { + case letter: case other_char: @<Append a new letter or a hyphen level@>@;@+break; + case spacer: case right_brace: {@+if (k > 0) + @<Insert a new pattern into the linked trie@>; + if (cur_cmd==right_brace) goto done; + k=0;hyf[0]=0;digit_sensed=false; + } @+break; + default:{@+print_err("Bad ");print_esc("patterns"); +@.Bad \\patterns@> + help1("(See Appendix H.)");error(); + } + } + } +done: + +@ @<Append a new letter or a hyphen level@>= +if (digit_sensed||(cur_chr < '0')||(cur_chr > '9')) + {@+if (cur_chr=='.') cur_chr=0; /*edge-of-word delimiter*/ + else{@+cur_chr=lc_code(cur_chr); + if (cur_chr==0) + {@+print_err("Nonletter"); +@.Nonletter@> + help1("(See Appendix H.)");error(); + } + } + if (k < 63) + {@+incr(k);hc[k]=cur_chr;hyf[k]=0;digit_sensed=false; + } + } +else if (k < 63) + {@+hyf[k]=cur_chr-'0';digit_sensed=true; + } + +@ When the following code comes into play, the pattern $p_1\ldots p_k$ +appears in |hc[1 dotdot k]|, and the corresponding sequence of numbers $n_0\ldots +n_k$ appears in |hyf[0 dotdot k]|. + +@<Insert a new pattern into the linked trie@>= +{@+@<Compute the trie op code, |v|, and set |l:=0|@>; +q=0;hc[0]=cur_lang; +while (l <= k) + {@+c=hc[l];incr(l);p=trie_l[q];first_child=true; + while ((p > 0)&&(c > so(trie_c[p]))) + {@+q=p;p=trie_r[q];first_child=false; + } + if ((p==0)||(c < so(trie_c[p]))) + @<Insert a new trie node between |q| and |p|, and make |p| point to it@>; + q=p; /*now node |q| represents $p_1\ldots p_{l-1}$*/ + } +if (trie_o[q]!=min_quarterword) + {@+print_err("Duplicate pattern"); +@.Duplicate pattern@> + help1("(See Appendix H.)");error(); + } +trie_o[q]=v; +} + +@ @<Insert a new trie node between |q| and |p|...@>= +{@+if (trie_ptr==trie_size) overflow("pattern memory", trie_size); +@:TeX capacity exceeded pattern memory}{\quad pattern memory@> +incr(trie_ptr);trie_r[trie_ptr]=p;p=trie_ptr;trie_l[p]=0; +if (first_child) trie_l[q]=p;@+else trie_r[q]=p; +trie_c[p]=si(c);trie_o[p]=min_quarterword; +} + +@ @<Compute the trie op code, |v|...@>= +if (hc[1]==0) hyf[0]=0; +if (hc[k]==0) hyf[k]=0; +l=k;v=min_quarterword; +loop@+{@+if (hyf[l]!=0) v=new_trie_op(k-l, hyf[l], v); + if (l > 0) decr(l);@+else goto done1; + } +done1: + +@ Finally we put everything together: Here is how the trie gets to its +final, efficient form. +The following packing routine is rigged so that the root of the linked +tree gets mapped into location 1 of |trie|, as required by the hyphenation +algorithm. This happens because the first call of |first_fit| will +``take'' location~1. + +@<Declare procedures for preprocessing hyphenation patterns@>= +static void init_trie(void) +{@+int @!p; /*pointer for initialization*/ +int @!j, @!k, @!t; /*all-purpose registers for initialization*/ +int @!r, @!s; /*used to clean up the packed |trie|*/ +two_halves @!h; /*template used to zero out |trie|'s holes*/ +@<Local variables to save the profiling context@>@; +@<Charge the time used here on |init_trie|@>@; +@<Get ready to compress the trie@>; +if (trie_root!=0) + {@+first_fit(trie_root);trie_pack(trie_root); + } +if (hyph_root!=0) @<Pack all stored |hyph_codes|@>; +@<Move the data into |trie|@>; +trie_not_ready=false; +@<restore the previous current file, line, and command@>@; +} + +@* Breaking vertical lists into pages. +The |vsplit| procedure, which implements \TeX's \.{\\vsplit} operation, +is considerably simpler than |line_break| because it doesn't have to +worry about hyphenation, and because its mission is to discover a single +break instead of an optimum sequence of breakpoints. But before we get +into the details of |vsplit|, we need to consider a few more basic things. + +@ A subroutine called |prune_page_top| takes a pointer to a vlist and +returns a pointer to a modified vlist in which all glue, kern, and penalty nodes +have been deleted before the first box or rule node. However, the first +box or rule is actually preceded by a newly created glue node designed so that +the topmost baseline will be at distance |split_top_skip| from the top, +whenever this is possible without backspacing. + +When the second argument |s| is |false| the deleted nodes are destroyed, +otherwise they are collected in a list starting at |split_disc|. + +In this routine and those that follow, we make use of the fact that a +vertical list contains no character nodes, hence the |type| field exists +for each node in the list. +@^data structure assumptions@> + +@p static pointer prune_page_top(pointer @!p, bool @!s) + /*adjust top after page break*/ +{@+pointer prev_p; /*lags one step behind |p|*/ +pointer @!q, @!r; /*temporary variables for list manipulation*/ +prev_p=temp_head;link(temp_head)=p; +while (p!=null) + switch (type(p)) { + case hlist_node: case vlist_node: case rule_node: @<Insert glue for |split_top_skip| +and set~|p:=null|@>@;@+break; + case whatsit_node: case mark_node: case ins_node: {@+prev_p=p;p=link(prev_p); + } @+break; + case glue_node: case kern_node: case penalty_node: {@+q=p;p=link(q);link(q)=null; + link(prev_p)=p; + if (s) + {@+if (split_disc==null) split_disc=q;@+else link(r)=q; + r=q; + } + else flush_node_list(q); + } @+break; + default:confusion("pruning"); +@:this can't happen pruning}{\quad pruning@> + } +return link(temp_head); +} + +@ @<Insert glue for |split_top_skip|...@>= +{@+q=new_skip_param(split_top_skip_code);link(prev_p)=q;link(q)=p; + /*now |temp_ptr==glue_ptr(q)|*/ +if (width(temp_ptr) > height(p)) width(temp_ptr)=width(temp_ptr)-height(p); +else width(temp_ptr)=0; +p=null; +} + +@ The next subroutine finds the best place to break a given vertical list +so as to obtain a box of height~|h|, with maximum depth~|d|. +A pointer to the beginning of the vertical list is given, +and a pointer to the optimum breakpoint is returned. The list is effectively +followed by a forced break, i.e., a penalty node with the |eject_penalty|; +if the best break occurs at this artificial node, the value |null| is returned. + +An array of six |scaled| distances is used to keep track of the height +from the beginning of the list to the current place, just as in |line_break|. +In fact, we use one of the same arrays, only changing its name to reflect +its new significance. + +@d active_height active_width /*new name for the six distance variables*/ +@d cur_height active_height[1] /*the natural height*/ +@d set_height_zero(A) active_height[A]=0 /*initialize the height to zero*/ +@# +@p static pointer vert_break(pointer @!p, scaled @!h, scaled @!d) + /*finds optimum page break*/ +{@+ +pointer prev_p; /*if |p| is a glue node, |type(prev_p)| determines + whether |p| is a legal breakpoint*/ +pointer @!q, @!r; /*glue specifications*/ +int @!pi; /*penalty value*/ +int @!b; /*badness at a trial breakpoint*/ +int @!least_cost; /*the smallest badness plus penalties found so far*/ +pointer @!best_place; /*the most recent break that leads to |least_cost|*/ +scaled @!prev_dp; /*depth of previous box in the list*/ +small_number @!t; /*|type| of the node following a kern*/ +prev_p=p; /*an initial glue node is not a legal breakpoint*/ +least_cost=awful_bad;do_all_six(set_height_zero);prev_dp=0; +loop@+{@+@<If node |p| is a legal breakpoint, check if this break is the best +known, and |goto done| if |p| is null or if the page-so-far is already too +full to accept more stuff@>; + prev_p=p;p=link(prev_p); + } +done: return best_place; +} + +@ A global variable |best_height_plus_depth| will be set to the natural size +of the box that corresponds to the optimum breakpoint found by |vert_break|. +(This value is used by the insertion-splitting algorithm of the page builder.) + +@<Glob...@>= +static scaled @!best_height_plus_depth; /*height of the best box, without stretching or + shrinking*/ + +@ A subtle point to be noted here is that the maximum depth~|d| might be +negative, so |cur_height| and |prev_dp| might need to be corrected even +after a glue or kern node. + +@<If node |p| is a legal breakpoint, check...@>= +if (p==null) pi=eject_penalty; +else@<Use node |p| to update the current height and depth measurements; if +this node is not a legal breakpoint, |goto not_found| or |update_heights|, +otherwise set |pi| to the associated penalty at the break@>; +@<Check if node |p| is a new champion breakpoint; then \(go)|goto done| if +|p| is a forced break or if the page-so-far is already too full@>; +if ((type(p) < glue_node)||(type(p) > kern_node)) goto not_found; +update_heights: @<Update the current height and depth measurements with respect +to a glue or kern node~|p|@>; +not_found: if (prev_dp > d) + {@+cur_height=cur_height+prev_dp-d; + prev_dp=d; + } + +@ @<Use node |p| to update the current height and depth measurements...@>= +switch (type(p)) { +case hlist_node: case vlist_node: case rule_node: {@+@t@>@;@/ + cur_height=cur_height+prev_dp+height(p);prev_dp=depth(p); + goto not_found; + } +case whatsit_node: @<Process whatsit |p| in |vert_break| loop, |goto not_found|@>; +case glue_node: if (precedes_break(prev_p)) pi=0; + else goto update_heights;@+break; +case kern_node: {@+if (link(p)==null) t=penalty_node; + else t=type(link(p)); + if (t==glue_node) pi=0;@+else goto update_heights; + } @+break; +case penalty_node: pi=penalty(p);@+break; +case mark_node: case ins_node: goto not_found; +default:confusion("vertbreak"); +@:this can't happen vertbreak}{\quad vertbreak@> +} + +@ @d deplorable 100000 /*more than |inf_bad|, but less than |awful_bad|*/ + +@<Check if node |p| is a new champion breakpoint; then \(go)...@>= +if (pi < inf_penalty) + {@+@<Compute the badness, |b|, using |awful_bad| if the box is too full@>; + if (b < awful_bad) + if (pi <= eject_penalty) b=pi; + else if (b < inf_bad) b=b+pi; + else b=deplorable; + if (b <= least_cost) + {@+best_place=p;least_cost=b; + best_height_plus_depth=cur_height+prev_dp; + } + if ((b==awful_bad)||(pi <= eject_penalty)) goto done; + } + +@ @<Compute the badness, |b|, using |awful_bad| if the box is too full@>= +if (cur_height < h) + if ((active_height[3]!=0)||(active_height[4]!=0)|| + (active_height[5]!=0)) b=0; + else b=badness(h-cur_height, active_height[2]); +else if (cur_height-h > active_height[6]) b=awful_bad; +else b=badness(cur_height-h, active_height[6]) + +@ Vertical lists that are subject to the |vert_break| procedure should not +contain infinite shrinkability, since that would permit any amount of +information to ``fit'' on one page. + +@<Update the current height and depth measurements with...@>= +if (type(p)==kern_node) q=p; +else{@+q=glue_ptr(p); + active_height[2+stretch_order(q)]=@| + active_height[2+stretch_order(q)]+stretch(q);@/ + active_height[6]=active_height[6]+shrink(q); + if ((shrink_order(q)!=normal)&&(shrink(q)!=0)) + {@+@t@>@;@/ + print_err("Infinite glue shrinkage found in box being split");@/ +@.Infinite glue shrinkage...@> + help4("The box you are \\vsplitting contains some infinitely",@/ + "shrinkable glue, e.g., `\\vss' or `\\vskip 0pt minus 1fil'.",@/ + "Such glue doesn't belong there; but you can safely proceed,",@/ + "since the offensive shrinkability has been made finite."); + error();r=new_spec(q);shrink_order(r)=normal;delete_glue_ref(q); + glue_ptr(p)=r;q=r; + } + } +cur_height=cur_height+prev_dp+width(q);prev_dp=0 + +@ Now we are ready to consider |vsplit| itself. Most of +its work is accomplished by the two subroutines that we have just considered. + +Given the number of a vlist box |n|, and given a desired page height |h|, +the |vsplit| function finds the best initial segment of the vlist and +returns a box for a page of height~|h|. The remainder of the vlist, if +any, replaces the original box, after removing glue and penalties and +adjusting for |split_top_skip|. Mark nodes in the split-off box are used to +set the values of |split_first_mark| and |split_bot_mark|; we use the +fact that |split_first_mark==null| if and only if |split_bot_mark==null|. + +The original box becomes ``void'' if and only if it has been entirely +extracted. The extracted box is ``void'' if and only if the original +box was void (or if it was, erroneously, an hlist box). + +@p @t\4@>@<Declare the function called |do_marks|@>@; +static pointer vsplit(halfword @!n, scaled @!h) + /*extracts a page of height |h| from box |n|*/ +{@+ +pointer v; /*the box to be split*/ +pointer p; /*runs through the vlist*/ +pointer q; /*points to where the break occurs*/ +cur_val=n;fetch_box(v); +flush_node_list(split_disc);split_disc=null; +if (sa_mark!=null) + if (do_marks(vsplit_init, 0, sa_mark)) sa_mark=null; +if (split_first_mark!=null) + {@+delete_token_ref(split_first_mark);split_first_mark=null; + delete_token_ref(split_bot_mark);split_bot_mark=null; + } +@<Dispense with trivial cases of void or bad boxes@>; +q=vert_break(list_ptr(v), h, split_max_depth); +@<Look at all the marks in nodes before the break, and set the final link +to |null| at the break@>; +q=prune_page_top(q, saving_vdiscards > 0); +p=list_ptr(v);free_node(v, box_node_size); +if (q!=null) q=vpack(q, natural); +change_box(q); /*the |eq_level| of the box stays the same*/ +return vpackage(p, h, exactly, split_max_depth); +} + +@ @<Dispense with trivial cases of void or bad boxes@>= +if (v==null) + {@+return null; + } +if (type(v)!=vlist_node) + {@+print_err("");print_esc("vsplit");print(" needs a "); + print_esc("vbox"); +@:vsplit\_}{\.{\\vsplit needs a \\vbox}@> + help2("The box you are trying to split is an \\hbox.",@/ + "I can't split such a box, so I'll leave it alone."); + error();return null; + } + +@ It's possible that the box begins with a penalty node that is the +``best'' break, so we must be careful to handle this special case correctly. + +@<Look at all the marks...@>= +p=list_ptr(v); +if (p==q) list_ptr(v)=null; +else loop@+{@+if (type(p)==mark_node) + if (mark_class(p)!=0) @<Update the current marks for |vsplit|@>@; + else if (split_first_mark==null) + {@+split_first_mark=mark_ptr(p); + split_bot_mark=split_first_mark; + token_ref_count(split_first_mark)=@| + token_ref_count(split_first_mark)+2; + } + else{@+delete_token_ref(split_bot_mark); + split_bot_mark=mark_ptr(p); + add_token_ref(split_bot_mark); + } + if (link(p)==q) + {@+link(p)=null;goto done; + } + p=link(p); + } +done: + +@* The page builder. +When \TeX\ appends new material to its main vlist in vertical mode, it uses +a method something like |vsplit| to decide where a page ends, except that +the calculations are done ``on line'' as new items come in. +The main complication in this process is that insertions must be put +into their boxes and removed from the vlist, in a more-or-less optimum manner. + +We shall use the term ``current page'' for that part of the main vlist that +is being considered as a candidate for being broken off and sent to the +user's output routine. The current page starts at |link(page_head)|, and +it ends at |page_tail|. We have |page_head==page_tail| if this list is empty. +@^current page@> + +Utter chaos would reign if the user kept changing page specifications +while a page is being constructed, so the page builder keeps the pertinent +specifications frozen as soon as the page receives its first box or +insertion. The global variable |page_contents| is |empty| when the +current page contains only mark nodes and content-less whatsit nodes; it +is |inserts_only| if the page contains only insertion nodes in addition to +marks and whatsits. Glue nodes, kern nodes, and penalty nodes are +discarded until a box or rule node appears, at which time |page_contents| +changes to |box_there|. As soon as |page_contents| becomes non-|empty|, +the current |vsize| and |max_depth| are squirreled away into |page_goal| +and |page_max_depth|; the latter values will be used until the page has +been forwarded to the user's output routine. The \.{\\topskip} adjustment +is made when |page_contents| changes to |box_there|. + +Although |page_goal| starts out equal to |vsize|, it is decreased by the +scaled natural height-plus-depth of the insertions considered so far, and by +the \.{\\skip} corrections for those insertions. Therefore it represents +the size into which the non-inserted material should fit, assuming that +all insertions in the current page have been made. + +The global variables |best_page_break| and |least_page_cost| correspond +respectively to the local variables |best_place| and |least_cost| in the +|vert_break| routine that we have already studied; i.e., they record the +location and value of the best place currently known for breaking the +current page. The value of |page_goal| at the time of the best break is +stored in |best_size|. + +@d inserts_only 1 + /*|page_contents| when an insert node has been contributed, but no boxes*/ +@d box_there 2 /*|page_contents| when a box or rule has been contributed*/ + +@<Glob...@>= +static pointer @!page_tail; /*the final node on the current page*/ +static int @!page_contents; /*what is on the current page so far?*/ +static scaled @!page_max_depth; /*maximum box depth on page being built*/ +static pointer @!best_page_break; /*break here to get the best page known so far*/ +static int @!least_page_cost; /*the score for this currently best page*/ +static scaled @!best_size; /*its |page_goal|*/ + +@ The page builder has another data structure to keep track of insertions. +This is a list of four-word nodes, starting and ending at |page_ins_head|. +That is, the first element of the list is node |r@t$\_1$@>==link(page_ins_head)|; +node $r_j$ is followed by |r@t$\_{j+1}$@>==link(r@t$\_j$@>)|; and if there are +|n| items we have |r@t$\_{n+1}$@>==page_ins_head|. The |subtype| field of +each node in this list refers to an insertion number; for example, `\.{\\insert +250}' would correspond to a node whose |subtype| is |qi(250)| +(the same as the |subtype| field of the relevant |ins_node|). These |subtype| +fields are in increasing order, and |subtype(page_ins_head)== +qi(255)|, so |page_ins_head| serves as a convenient sentinel +at the end of the list. A record is present for each insertion number that +appears in the current page. + +The |type| field in these nodes distinguishes two possibilities that +might occur as we look ahead before deciding on the optimum page break. +If |type(r)==inserting|, then |height(r)| contains the total of the +height-plus-depth dimensions of the box and all its inserts seen so far. +If |type(r)==split_up|, then no more insertions will be made into this box, +because at least one previous insertion was too big to fit on the current +page; |broken_ptr(r)| points to the node where that insertion will be +split, if \TeX\ decides to split it, |broken_ins(r)| points to the +insertion node that was tentatively split, and |height(r)| includes also the +natural height plus depth of the part that would be split off. + +In both cases, |last_ins_ptr(r)| points to the last |ins_node| +encountered for box |qo(subtype(r))| that would be at least partially +inserted on the next page; and |best_ins_ptr(r)| points to the last +such |ins_node| that should actually be inserted, to get the page with +minimum badness among all page breaks considered so far. We have +|best_ins_ptr(r)==null| if and only if no insertion for this box should +be made to produce this optimum page. + +The data structure definitions here use the fact that the |@!height| field +appears in the fourth word of a box node. +@^data structure assumptions@> + +@d page_ins_node_size 4 /*number of words for a page insertion node*/ +@d inserting 0 /*an insertion class that has not yet overflowed*/ +@d split_up 1 /*an overflowed insertion class*/ +@d broken_ptr(A) link(A+1) + /*an insertion for this class will break here if anywhere*/ +@d broken_ins(A) info(A+1) /*this insertion might break at |broken_ptr|*/ +@d last_ins_ptr(A) link(A+2) /*the most recent insertion for this |subtype|*/ +@d best_ins_ptr(A) info(A+2) /*the optimum most recent insertion*/ + +@<Initialize the special list heads...@>= +subtype(page_ins_head)=qi(255); +type(page_ins_head)=split_up;link(page_ins_head)=page_ins_head; + +@ An array |page_so_far| records the heights and depths of everything +on the current page. This array contains six |scaled| numbers, like the +similar arrays already considered in |line_break| and |vert_break|; and it +also contains |page_goal| and |page_depth|, since these values are +all accessible to the user via |set_page_dimen| commands. The +value of |page_so_far[1]| is also called |page_total|. The stretch +and shrink components of the \.{\\skip} corrections for each insertion are +included in |page_so_far|, but the natural space components of these +corrections are not, since they have been subtracted from |page_goal|. + +The variable |page_depth| records the depth of the current page; it has been +adjusted so that it is at most |page_max_depth|. The variable +|last_glue| points to the glue specification of the most recent node +contributed from the contribution list, if this was a glue node; otherwise +|last_glue==max_halfword|. (If the contribution list is nonempty, +however, the value of |last_glue| is not necessarily accurate.) +The variables |last_penalty|, |last_kern|, and |last_node_type| +are similar. And +finally, |insert_penalties| holds the sum of the penalties associated with +all split and floating insertions. + +@d page_goal page_so_far[0] /*desired height of information on page being built*/ +@d page_total page_so_far[1] /*height of the current page*/ +@d page_shrink page_so_far[6] /*shrinkability of the current page*/ +@d page_depth page_so_far[7] /*depth of the current page*/ + +@<Glob...@>= +static scaled @!page_so_far[8]; /*height and glue of the current page*/ +static pointer @!last_glue; /*used to implement \.{\\lastskip}*/ +static int @!last_penalty; /*used to implement \.{\\lastpenalty}*/ +static scaled @!last_kern; /*used to implement \.{\\lastkern}*/ +static int @!last_node_type; /*used to implement \.{\\lastnodetype}*/ +static int @!insert_penalties; /*sum of the penalties for insertions + that were held over*/ + +@ @<Put each...@>= +primitive("pagegoal", set_page_dimen, 0); +@!@:page\_goal\_}{\.{\\pagegoal} primitive@> +primitive("pagetotal", set_page_dimen, 1); +@!@:page\_total\_}{\.{\\pagetotal} primitive@> +primitive("pagestretch", set_page_dimen, 2); +@!@:page\_stretch\_}{\.{\\pagestretch} primitive@> +primitive("pagefilstretch", set_page_dimen, 3); +@!@:page\_fil\_stretch\_}{\.{\\pagefilstretch} primitive@> +primitive("pagefillstretch", set_page_dimen, 4); +@!@:page\_fill\_stretch\_}{\.{\\pagefillstretch} primitive@> +primitive("pagefilllstretch", set_page_dimen, 5); +@!@:page\_filll\_stretch\_}{\.{\\pagefilllstretch} primitive@> +primitive("pageshrink", set_page_dimen, 6); +@!@:page\_shrink\_}{\.{\\pageshrink} primitive@> +primitive("pagedepth", set_page_dimen, 7); +@!@:page\_depth\_}{\.{\\pagedepth} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case set_page_dimen: switch (chr_code) { +case 0: print_esc("pagegoal");@+break; +case 1: print_esc("pagetotal");@+break; +case 2: print_esc("pagestretch");@+break; +case 3: print_esc("pagefilstretch");@+break; +case 4: print_esc("pagefillstretch");@+break; +case 5: print_esc("pagefilllstretch");@+break; +case 6: print_esc("pageshrink");@+break; +default:print_esc("pagedepth"); +} @+break; + +@ @d print_plus(A, B) if (page_so_far[A]!=0) + {@+print(" plus ");print_scaled(page_so_far[A]);print(B);@+} + +@p static void print_totals(void) +{@+print_scaled(page_total); +print_plus(2,""); +print_plus(3,"fil"); +print_plus(4,"fill"); +print_plus(5,"filll"); +if (page_shrink!=0) + {@+print(" minus ");print_scaled(page_shrink); + } +} + +@ @<Show the status of the current page@>= +if (page_head!=page_tail) + {@+print_nl("### current page:"); + if (output_active) print(" (held over for next output)"); +@.held over for next output@> + show_box(link(page_head)); + if (page_contents > empty) + {@+print_nl("total height ");print_totals(); +@:total\_height}{\.{total height}@> + print_nl(" goal height ");print_scaled(page_goal); +@.goal height@> + r=link(page_ins_head); + while (r!=page_ins_head) + {@+print_ln();print_esc("insert");t=qo(subtype(r)); + print_int(t);print(" adds "); + if (count(t)==1000) t=height(r); + else t=x_over_n(height(r), 1000)*count(t); + print_scaled(t); + if (type(r)==split_up) + {@+q=page_head;t=0; + @/do@+{q=link(q); + if ((type(q)==ins_node)&&(subtype(q)==subtype(r))) incr(t); + }@+ while (!(q==broken_ins(r))); + print(", #");print_int(t);print(" might split"); + } + r=link(r); + } + } + } + +@ Here is a procedure that is called when the |page_contents| is changing +from |empty| to |inserts_only| or |box_there|. + +@d set_page_so_far_zero(A) page_so_far[A]=0 + +@p static void freeze_page_specs(small_number @!s) +{@+page_contents=s; +page_goal=vsize;page_max_depth=max_depth; +page_depth=0;do_all_six(set_page_so_far_zero); +least_page_cost=awful_bad; +#ifdef @!STAT +if (tracing_pages > 0) + {@+begin_diagnostic(); + print_nl("%% goal height=");print_scaled(page_goal); +@.goal height@> + print(", max depth=");print_scaled(page_max_depth); + end_diagnostic(false); + } @; +#endif +@;@/ +} + +@ Pages are built by appending nodes to the current list in \TeX's +vertical mode, which is at the outermost level of the semantic nest. This +vlist is split into two parts; the ``current page'' that we have been +talking so much about already, and the ``contribution list'' that receives +new nodes as they are created. The current page contains everything that +the page builder has accounted for in its data structures, as described +above, while the contribution list contains other things that have been +generated by other parts of \TeX\ but have not yet been +seen by the page builder. +The contribution list starts at |link(contrib_head)|, and it ends at the +current node in \TeX's vertical mode. + +When \TeX\ has appended new material in vertical mode, it calls the procedure +|build_page|, which tries to catch up by moving nodes from the contribution +list to the current page. This procedure will succeed in its goal of +emptying the contribution list, unless a page break is discovered, i.e., +unless the current page has grown to the point where the optimum next +page break has been determined. In the latter case, the nodes after the +optimum break will go back onto the contribution list, and control will +effectively pass to the user's output routine. + +We make |type(page_head)==glue_node|, so that an initial glue node on +the current page will not be considered a valid breakpoint. + +@<Initialize the special list...@>= +type(page_head)=glue_node;subtype(page_head)=normal; + +@ The global variable |output_active| is true during the time the +user's output routine is driving \TeX. + +@<Glob...@>= +static bool @!output_active; /*are we in the midst of an output routine?*/ + +@ @<Set init...@>= +output_active=false;insert_penalties=0; + +@ The page builder is ready to start a fresh page if we initialize +the following state variables. (However, the page insertion list is initialized +elsewhere.) + +@<Start a new current page@>= +page_contents=empty;page_tail=page_head;link(page_head)=null;@/ +last_glue=max_halfword;last_penalty=0;last_kern=0; +last_node_type=-1; +page_depth=0;page_max_depth=0 + +@ At certain times box 255 is supposed to be void (i.e., |null|), +or an insertion box is supposed to be ready to accept a vertical list. +If not, an error message is printed, and the following subroutine +flushes the unwanted contents, reporting them to the user. + +@p static void box_error(eight_bits @!n) +{@+error();begin_diagnostic(); +print_nl("The following box has been deleted:"); +@.The following...deleted@> +show_box(box(n));end_diagnostic(true); +flush_node_list(box(n));box(n)=null; +} + +@ The following procedure guarantees that a given box register +does not contain an \.{\\hbox}. + +@p static void ensure_vbox(eight_bits @!n) +{@+pointer p; /*the box register contents*/ +p=box(n); +if (p!=null) if (type(p)==hlist_node) + {@+print_err("Insertions can only be added to a vbox"); +@.Insertions can only...@> + help3("Tut tut: You're trying to \\insert into a",@/ + "\\box register that now contains an \\hbox.",@/ + "Proceed, and I'll discard its present contents."); + box_error(n); + } +} + +@ \TeX\ is not always in vertical mode at the time |build_page| +is called; the current mode reflects what \TeX\ should return to, after +the contribution list has been emptied. A call on |build_page| should +be immediately followed by `|goto big_switch|', which is \TeX's central +control point. + +@p @t\4@>@<Declare the procedure called |fire_up|@>@;@/ +static void build_page(void) /*append contributions to the current page*/ +{@+ +pointer p; /*the node being appended*/ +pointer @!q, @!r; /*nodes being examined*/ +int @!b, @!c; /*badness and cost of current page*/ +int @!pi; /*penalty to be added to the badness*/ +int @!n; /*insertion box number*/ +scaled @!delta, @!h, @!w; /*sizes used for insertion calculations*/ +@<Local variables to save the profiling context@>@; +if ((link(contrib_head)==null)||output_active) return; +@<Charge the time used here on |build_page|@>@; +@/do@+{resume: p=link(contrib_head);@/ +@<Update the values of |last_glue|, |last_penalty|, and |last_kern|@>; +@<Move node |p| to the current page; if it is time for a page break, put the +nodes following the break back onto the contribution list, and |return| to +the user's output routine if there is one@>; +}@+ while (!(link(contrib_head)==null)); +@<Make the contribution list empty by setting its tail to |contrib_head|@>; +@<restore the previous current file, line, and command@>@; +} + +@ @d contrib_tail nest[0].tail_field /*tail of the contribution list*/ + +@<Make the contribution list empty...@>= +if (nest_ptr==0) tail=contrib_head; /*vertical mode*/ +else contrib_tail=contrib_head /*other modes*/ + +@ @<Update the values of |last_glue|...@>= +if (last_glue!=max_halfword) delete_glue_ref(last_glue); +last_penalty=0;last_kern=0; +last_node_type=type(p)+1; +if (type(p)==glue_node) + {@+last_glue=glue_ptr(p);add_glue_ref(last_glue); + } +else{@+last_glue=max_halfword; + if (type(p)==penalty_node) last_penalty=penalty(p); + else if (type(p)==kern_node) last_kern=width(p); + } + +@ The code here is an example of a many-way switch into routines that +merge together in different places. Some people call this unstructured +programming, but the author doesn't see much wrong with it, as long as +@^Knuth, Donald Ervin@> +the various labels have a well-understood meaning. + +@<Move node |p| to the current page;...@>= +@<If the current page is empty and node |p| is to be deleted, |goto done1|; +otherwise use node |p| to update the state of the current page; if this node +is an insertion, |goto contribute|; otherwise if this node is not a legal +breakpoint, |goto contribute| or |update_heights|; otherwise set |pi| to the +penalty associated with this breakpoint@>; +@<Check if node |p| is a new champion breakpoint; then \(if)if it is time +for a page break, prepare for output, and either fire up the user's output +routine and |return| or ship out the page and |goto done|@>; +if ((type(p) < glue_node)||(type(p) > kern_node)) goto contribute; +update_heights: @<Update the current page measurements with respect to the +glue or kern specified by node~|p|@>; +contribute: @<Make sure that |page_max_depth| is not exceeded@>; +@<Link node |p| into the current page and |goto done|@>; +done1: @<Recycle node |p|@>; +done: + +@ @<Link node |p| into the current page and |goto done|@>= +link(page_tail)=p;page_tail=p; +link(contrib_head)=link(p);link(p)=null;goto done + +@ @<Recycle node |p|@>= +link(contrib_head)=link(p);link(p)=null; +if (saving_vdiscards > 0) + {@+if (page_disc==null) page_disc=p;@+else link(tail_page_disc)=p; + tail_page_disc=p; + } +else flush_node_list(p) + +@ The title of this section is already so long, it seems best to avoid +making it more accurate but still longer, by mentioning the fact that a +kern node at the end of the contribution list will not be contributed until +we know its successor. + +@<If the current page is empty...@>= +switch (type(p)) { +case hlist_node: case vlist_node: case rule_node: if (page_contents < box_there) + @<Initialize the current page, insert the \.{\\topskip} glue ahead of +|p|, and |goto resume|@>@; + else@<Prepare to move a box or rule node to the current page, then |goto +contribute|@>@;@+break; +case whatsit_node: @<Prepare to move whatsit |p| to the current page, then +|goto contribute|@>; +case glue_node: if (page_contents < box_there) goto done1; + else if (precedes_break(page_tail)) pi=0; + else goto update_heights;@+break; +case kern_node: if (page_contents < box_there) goto done1; + else if (link(p)==null) return; + else if (type(link(p))==glue_node) pi=0; + else goto update_heights;@+break; +case penalty_node: if (page_contents < box_there) goto done1;@+else pi=penalty(p);@+break; +case mark_node: goto contribute; +case ins_node: @<Append an insertion to the current page and |goto contribute|@>@; +default:confusion("page"); +@:this can't happen page}{\quad page@> +} + +@ @<Initialize the current page, insert the \.{\\topskip} glue...@>= +{@+if (page_contents==empty) freeze_page_specs(box_there); +else page_contents=box_there; +q=new_skip_param(top_skip_code); /*now |temp_ptr==glue_ptr(q)|*/ +if (width(temp_ptr) > height(p)) width(temp_ptr)=width(temp_ptr)-height(p); +else width(temp_ptr)=0; +link(q)=p;link(contrib_head)=q;goto resume; +} + +@ @<Prepare to move a box or rule node to the current page...@>= +{@+page_total=page_total+page_depth+height(p); +page_depth=depth(p); +goto contribute; +} + +@ @<Make sure that |page_max_depth| is not exceeded@>= +if (page_depth > page_max_depth) + {@+page_total=@| + page_total+page_depth-page_max_depth;@/ + page_depth=page_max_depth; + } + +@ @<Update the current page measurements with respect to the glue...@>= +if (type(p)==kern_node) q=p; +else{@+q=glue_ptr(p); + page_so_far[2+stretch_order(q)]=@| + page_so_far[2+stretch_order(q)]+stretch(q);@/ + page_shrink=page_shrink+shrink(q); + if ((shrink_order(q)!=normal)&&(shrink(q)!=0)) + {@+@t@>@;@/ + print_err("Infinite glue shrinkage found on current page");@/ +@.Infinite glue shrinkage...@> + help4("The page about to be output contains some infinitely",@/ + "shrinkable glue, e.g., `\\vss' or `\\vskip 0pt minus 1fil'.",@/ + "Such glue doesn't belong there; but you can safely proceed,",@/ + "since the offensive shrinkability has been made finite."); + error(); + r=new_spec(q);shrink_order(r)=normal;delete_glue_ref(q); + glue_ptr(p)=r;q=r; + } + } +page_total=page_total+page_depth+width(q);page_depth=0 + +@ @<Check if node |p| is a new champion breakpoint; then \(if)...@>= +if (pi < inf_penalty) + {@+@<Compute the badness, |b|, of the current page, using |awful_bad| if +the box is too full@>; + if (b < awful_bad) + if (pi <= eject_penalty) c=pi; + else if (b < inf_bad) c=b+pi+insert_penalties; + else c=deplorable; + else c=b; + if (insert_penalties >= 10000) c=awful_bad; +#ifdef @!STAT + if (tracing_pages > 0) @<Display the page break cost@>; +#endif +@;@/ + if (c <= least_page_cost) + {@+best_page_break=p;best_size=page_goal; + least_page_cost=c; + r=link(page_ins_head); + while (r!=page_ins_head) + {@+best_ins_ptr(r)=last_ins_ptr(r); + r=link(r); + } + } + if ((c==awful_bad)||(pi <= eject_penalty)) + {@+fire_up(p); /*output the current page at the best place*/ + if (output_active) + { @<restore the previous current file, line, and command@>@; + return; /*user's output routine will act*/ + } + goto done; /*the page has been shipped out by default output routine*/ + } + } + +@ @<Display the page break cost@>= +{@+begin_diagnostic();print_nl("%"); +print(" t=");print_totals();@/ +print(" g=");print_scaled(page_goal);@/ +print(" b="); +if (b==awful_bad) print_char('*');@+else print_int(b); +@.*\relax@> +print(" p=");print_int(pi); +print(" c="); +if (c==awful_bad) print_char('*');@+else print_int(c); +if (c <= least_page_cost) print_char('#'); +end_diagnostic(false); +} + +@ @<Compute the badness, |b|, of the current page...@>= +if (page_total < page_goal) + if ((page_so_far[3]!=0)||(page_so_far[4]!=0)||@| + (page_so_far[5]!=0)) b=0; + else b=badness(page_goal-page_total, page_so_far[2]); +else if (page_total-page_goal > page_shrink) b=awful_bad; +else b=badness(page_total-page_goal, page_shrink) + +@ @<Append an insertion to the current page and |goto contribute|@>= +{@+if (page_contents==empty) freeze_page_specs(inserts_only); +n=subtype(p);r=page_ins_head; +while (n >= subtype(link(r))) r=link(r); +n=qo(n); +if (subtype(r)!=qi(n)) + @<Create a page insertion node with |subtype(r)=qi(n)|, and include the +glue correction for box |n| in the current page state@>; +if (type(r)==split_up) insert_penalties=insert_penalties+float_cost(p); +else{@+last_ins_ptr(r)=p; + delta=page_goal-page_total-page_depth+page_shrink; + /*this much room is left if we shrink the maximum*/ + if (count(n)==1000) h=height(p); + else h=x_over_n(height(p), 1000)*count(n); /*this much room is needed*/ + if (((h <= 0)||(h <= delta))&&(height(p)+height(r) <= dimen(n))) + {@+page_goal=page_goal-h;height(r)=height(r)+height(p); + } + else@<Find the best way to split the insertion, and change |type(r)| to +|split_up|@>; + } +goto contribute; +} + +@ We take note of the value of \.{\\skip} |n| and the height plus depth +of \.{\\box}~|n| only when the first \.{\\insert}~|n| node is +encountered for a new page. A user who changes the contents of \.{\\box}~|n| +after that first \.{\\insert}~|n| had better be either extremely careful +or extremely lucky, or both. + +@<Create a page insertion node...@>= +{@+q=get_node(page_ins_node_size);link(q)=link(r);link(r)=q;r=q; +subtype(r)=qi(n);type(r)=inserting;ensure_vbox(n); +if (box(n)==null) height(r)=0; +else height(r)=height(box(n))+depth(box(n)); +best_ins_ptr(r)=null;@/ +q=skip(n); +if (count(n)==1000) h=height(r); +else h=x_over_n(height(r), 1000)*count(n); +page_goal=page_goal-h-width(q);@/ +page_so_far[2+stretch_order(q)]=@|page_so_far[2+stretch_order(q)]+stretch(q);@/ +page_shrink=page_shrink+shrink(q); +if ((shrink_order(q)!=normal)&&(shrink(q)!=0)) + {@+print_err("Infinite glue shrinkage inserted from ");print_esc("skip"); +@.Infinite glue shrinkage...@> + print_int(n); + help3("The correction glue for page breaking with insertions",@/ + "must have finite shrinkability. But you may proceed,",@/ + "since the offensive shrinkability has been made finite."); + error(); + } +} + +@ Here is the code that will split a long footnote between pages, in an +emergency. The current situation deserves to be recapitulated: Node |p| +is an insertion into box |n|; the insertion will not fit, in its entirety, +either because it would make the total contents of box |n| greater than +\.{\\dimen} |n|, or because it would make the incremental amount of growth +|h| greater than the available space |delta|, or both. (This amount |h| has +been weighted by the insertion scaling factor, i.e., by \.{\\count} |n| +over 1000.) Now we will choose the best way to break the vlist of the +insertion, using the same criteria as in the \.{\\vsplit} operation. + +@<Find the best way to split the insertion...@>= +{@+if (count(n) <= 0) w=max_dimen; +else{@+w=page_goal-page_total-page_depth; + if (count(n)!=1000) w=x_over_n(w, count(n))*1000; + } +if (w > dimen(n)-height(r)) w=dimen(n)-height(r); +q=vert_break(ins_ptr(p), w, depth(p)); +height(r)=height(r)+best_height_plus_depth; +#ifdef @!STAT +if (tracing_pages > 0) @<Display the insertion split cost@>; +#endif +@;@/ +if (count(n)!=1000) + best_height_plus_depth=x_over_n(best_height_plus_depth, 1000)*count(n); +page_goal=page_goal-best_height_plus_depth; +type(r)=split_up;broken_ptr(r)=q;broken_ins(r)=p; +if (q==null) insert_penalties=insert_penalties+eject_penalty; +else if (type(q)==penalty_node) insert_penalties=insert_penalties+penalty(q); +} + +@ @<Display the insertion split cost@>= +{@+begin_diagnostic();print_nl("% split");print_int(n); +@.split@> +print(" to ");print_scaled(w); +print_char(',');print_scaled(best_height_plus_depth);@/ +print(" p="); +if (q==null) print_int(eject_penalty); +else if (type(q)==penalty_node) print_int(penalty(q)); +else print_char('0'); +end_diagnostic(false); +} + +@ When the page builder has looked at as much material as could appear before +the next page break, it makes its decision. The break that gave minimum +badness will be used to put a completed ``page'' into box 255, with insertions +appended to their other boxes. + +We also set the values of |top_mark|, |first_mark|, and |bot_mark|. The +program uses the fact that |bot_mark!=null| implies |first_mark!=null|; +it also knows that |bot_mark==null| implies |top_mark==first_mark==null|. + +The |fire_up| subroutine prepares to output the current page at the best +place; then it fires up the user's output routine, if there is one, +or it simply ships out the page. There is one parameter, |c|, which represents +the node that was being contributed to the page when the decision to +force an output was made. + +@<Declare the procedure called |fire_up|@>= +static void fire_up(pointer @!c) +{@+ +pointer p, @!q, @!r, @!s; /*nodes being examined and/or changed*/ +pointer @!prev_p; /*predecessor of |p|*/ +int @!n; /*insertion box number*/ +bool @!wait; /*should the present insertion be held over?*/ +int @!save_vbadness; /*saved value of |vbadness|*/ +scaled @!save_vfuzz; /*saved value of |vfuzz|*/ +pointer @!save_split_top_skip; /*saved value of |split_top_skip|*/ +@<Set the value of |output_penalty|@>; +if (sa_mark!=null) + if (do_marks(fire_up_init, 0, sa_mark)) sa_mark=null; +if (bot_mark!=null) + {@+if (top_mark!=null) delete_token_ref(top_mark); + top_mark=bot_mark;add_token_ref(top_mark); + delete_token_ref(first_mark);first_mark=null; + } +@<Put the \(o)optimal current page into box 255, update |first_mark| and |bot_mark|, +append insertions to their boxes, and put the remaining nodes back on the +contribution list@>; +if (sa_mark!=null) + if (do_marks(fire_up_done, 0, sa_mark)) sa_mark=null; +if ((top_mark!=null)&&(first_mark==null)) + {@+first_mark=top_mark;add_token_ref(top_mark); + } +if (output_routine!=null) + if (dead_cycles >= max_dead_cycles) + @<Explain that too many dead cycles have occurred in a row@>@; + else@<Fire up the user's output routine and |return|@>; +@<Perform the default output routine@>; +} + +@ @<Set the value of |output_penalty|@>= +if (type(best_page_break)==penalty_node) + {@+geq_word_define(int_base+output_penalty_code, penalty(best_page_break)); + penalty(best_page_break)=inf_penalty; + } +else geq_word_define(int_base+output_penalty_code, inf_penalty) + +@ As the page is finally being prepared for output, +pointer |p| runs through the vlist, with |prev_p| trailing behind; +pointer |q| is the tail of a list of insertions that +are being held over for a subsequent page. + +@<Put the \(o)optimal current page into box 255...@>= +if (c==best_page_break) best_page_break=null; /*|c| not yet linked in*/ +@<Ensure that box 255 is empty before output@>; +insert_penalties=0; /*this will count the number of insertions held over*/ +save_split_top_skip=split_top_skip; +if (holding_inserts <= 0) + @<Prepare all the boxes involved in insertions to act as queues@>; +q=hold_head;link(q)=null;prev_p=page_head;p=link(prev_p); +while (p!=best_page_break) + {@+if (type(p)==ins_node) + {@+if (holding_inserts <= 0) + @<Either insert the material specified by node |p| into the appropriate +box, or hold it for the next page; also delete node |p| from the current page@>; + } + else if (type(p)==mark_node) + if (mark_class(p)!=0) @<Update the current marks for |fire_up|@>@; + else@<Update the values of |first_mark| and |bot_mark|@>; + prev_p=p;p=link(prev_p); + } +split_top_skip=save_split_top_skip; +@<Break the current page at node |p|, put it in box~255, and put the remaining +nodes on the contribution list@>; +@<Delete \(t)the page-insertion nodes@>@; + +@ @<Ensure that box 255 is empty before output@>= +if (box(255)!=null) + {@+print_err("");print_esc("box");print("255 is not void"); +@:box255}{\.{\\box255 is not void}@> + help2("You shouldn't use \\box255 except in \\output routines.",@/ + "Proceed, and I'll discard its present contents."); + box_error(255); + } + +@ @<Update the values of |first_mark| and |bot_mark|@>= +{@+if (first_mark==null) + {@+first_mark=mark_ptr(p); + add_token_ref(first_mark); + } +if (bot_mark!=null) delete_token_ref(bot_mark); +bot_mark=mark_ptr(p);add_token_ref(bot_mark); +} + +@ When the following code is executed, the current page runs from node +|link(page_head)| to node |prev_p|, and the nodes from |p| to |page_tail| +are to be placed back at the front of the contribution list. Furthermore +the heldover insertions appear in a list from |link(hold_head)| to |q|; we +will put them into the current page list for safekeeping while the user's +output routine is active. We might have |q==hold_head|; and |p==null| if +and only if |prev_p==page_tail|. Error messages are suppressed within +|vpackage|, since the box might appear to be overfull or underfull simply +because the stretch and shrink from the \.{\\skip} registers for inserts +are not actually present in the box. + +@<Break the current page at node |p|, put it...@>= +if (p!=null) + {@+if (link(contrib_head)==null) + if (nest_ptr==0) tail=page_tail; + else contrib_tail=page_tail; + link(page_tail)=link(contrib_head); + link(contrib_head)=p; + link(prev_p)=null; + } +save_vbadness=vbadness;vbadness=inf_bad; +save_vfuzz=vfuzz;vfuzz=max_dimen; /*inhibit error messages*/ +box(255)=vpackage(link(page_head), best_size, exactly, page_max_depth); +vbadness=save_vbadness;vfuzz=save_vfuzz; +if (last_glue!=max_halfword) delete_glue_ref(last_glue); +@<Start a new current page@>; /*this sets |last_glue=max_halfword|*/ +if (q!=hold_head) + {@+link(page_head)=link(hold_head);page_tail=q; + } + +@ If many insertions are supposed to go into the same box, we want to know +the position of the last node in that box, so that we don't need to waste time +when linking further information into it. The |last_ins_ptr| fields of the +page insertion nodes are therefore used for this purpose during the +packaging phase. + +@<Prepare all the boxes involved in insertions to act as queues@>= +{@+r=link(page_ins_head); +while (r!=page_ins_head) + {@+if (best_ins_ptr(r)!=null) + {@+n=qo(subtype(r));ensure_vbox(n); + if (box(n)==null) box(n)=new_null_box(); + p=box(n)+list_offset; + while (link(p)!=null) p=link(p); + last_ins_ptr(r)=p; + } + r=link(r); + } +} + +@ @<Delete \(t)the page-insertion nodes@>= +r=link(page_ins_head); +while (r!=page_ins_head) + {@+q=link(r);free_node(r, page_ins_node_size);r=q; + } +link(page_ins_head)=page_ins_head + +@ We will set |best_ins_ptr=null| and package the box corresponding to +insertion node~|r|, just after making the final insertion into that box. +If this final insertion is `|split_up|', the remainder after splitting +and pruning (if any) will be carried over to the next page. + +@<Either insert the material specified by node |p| into...@>= +{@+r=link(page_ins_head); +while (subtype(r)!=subtype(p)) r=link(r); +if (best_ins_ptr(r)==null) wait=true; +else{@+wait=false;s=last_ins_ptr(r);link(s)=ins_ptr(p); + if (best_ins_ptr(r)==p) + @<Wrap up the box specified by node |r|, splitting node |p| if called +for; set |wait:=true| if node |p| holds a remainder after splitting@>@; + else{@+while (link(s)!=null) s=link(s); + last_ins_ptr(r)=s; + } + } +@<Either append the insertion node |p| after node |q|, and remove it from +the current page, or delete |node(p)|@>; +} + +@ @<Wrap up the box specified by node |r|, splitting node |p| if...@>= +{@+if (type(r)==split_up) + if ((broken_ins(r)==p)&&(broken_ptr(r)!=null)) + {@+while (link(s)!=broken_ptr(r)) s=link(s); + link(s)=null; + split_top_skip=split_top_ptr(p); + ins_ptr(p)=prune_page_top(broken_ptr(r), false); + if (ins_ptr(p)!=null) + {@+temp_ptr=vpack(ins_ptr(p), natural); + height(p)=height(temp_ptr)+depth(temp_ptr); + free_node(temp_ptr, box_node_size);wait=true; + } + } +best_ins_ptr(r)=null; +n=qo(subtype(r)); +temp_ptr=list_ptr(box(n)); +free_node(box(n), box_node_size); +box(n)=vpack(temp_ptr, natural); +} + +@ @<Either append the insertion node |p|...@>= +link(prev_p)=link(p);link(p)=null; +if (wait) + {@+link(q)=p;q=p;incr(insert_penalties); + } +else{@+delete_glue_ref(split_top_ptr(p)); + free_node(p, ins_node_size); + } +p=prev_p + +@ The list of heldover insertions, running from |link(page_head)| to +|page_tail|, must be moved to the contribution list when the user has +specified no output routine. + +@<Perform the default output routine@>= +{@+if (link(page_head)!=null) + {@+if (link(contrib_head)==null) + if (nest_ptr==0) tail=page_tail;@+else contrib_tail=page_tail; + else link(page_tail)=link(contrib_head); + link(contrib_head)=link(page_head); + link(page_head)=null;page_tail=page_head; + } +flush_node_list(page_disc);page_disc=null; +ship_out(box(255));box(255)=null; +} + +@ @<Explain that too many dead cycles have occurred in a row@>= +{@+print_err("Output loop---");print_int(dead_cycles); +@.Output loop...@> +print(" consecutive dead cycles"); +help3("I've concluded that your \\output is awry; it never does a",@/ +"\\shipout, so I'm shipping \\box255 out myself. Next time",@/ +"increase \\maxdeadcycles if you want me to be more patient!");error(); +} + +@ @<Fire up the user's output routine and |return|@>= +{@+output_active=true; +incr(dead_cycles); +push_nest();mode=-vmode;prev_depth=ignore_depth;mode_line=-line; +begin_token_list(output_routine, output_text); +new_save_level(output_group);normal_paragraph(); +scan_left_brace(); +return; +} + +@ When the user's output routine finishes, it has constructed a vlist +in internal vertical mode, and \TeX\ will do the following: + +@<Resume the page builder after an output routine has come to an end@>= +{@+if ((loc!=null)|| + ((token_type!=output_text)&&(token_type!=backed_up))) + @<Recover from an unbalanced output routine@>; +end_token_list(); /*conserve stack space in case more outputs are triggered*/ +end_graf();unsave();output_active=false;insert_penalties=0;@/ +@<Ensure that box 255 is empty after output@>; +if (tail!=head) /*current list goes after heldover insertions*/ + {@+link(page_tail)=link(head); + page_tail=tail; + } +if (link(page_head)!=null) /*and both go before heldover contributions*/ + {@+if (link(contrib_head)==null) contrib_tail=page_tail; + link(page_tail)=link(contrib_head); + link(contrib_head)=link(page_head); + link(page_head)=null;page_tail=page_head; + } +flush_node_list(page_disc);page_disc=null; +pop_nest();build_page(); +} + +@ @<Recover from an unbalanced output routine@>= +{@+print_err("Unbalanced output routine"); +@.Unbalanced output routine@> +help2("Your sneaky output routine has problematic {'s and/or }'s.",@/ +"I can't handle that very well; good luck.");error(); +@/do@+{get_token(); +}@+ while (!(loc==null)); +} /*loops forever if reading from a file, since |null==min_halfword <= 0|*/ + +@ @<Ensure that box 255 is empty after output@>= +if (box(255)!=null) + {@+print_err("Output routine didn't use all of "); + print_esc("box");print_int(255); +@.Output routine didn't use...@> + help3("Your \\output commands should empty \\box255,",@/ + "e.g., by saying `\\shipout\\box255'.",@/ + "Proceed; I'll discard its present contents."); + box_error(255); + } + +@* The chief executive. +We come now to the |main_control| routine, which contains the master +switch that causes all the various pieces of \TeX\ to do their things, +in the right order. + +In a sense, this is the grand climax of the program: It applies all the +tools that we have worked so hard to construct. In another sense, this is +the messiest part of the program: It necessarily refers to other pieces +of code all over the place, so that a person can't fully understand what is +going on without paging back and forth to be reminded of conventions that +are defined elsewhere. We are now at the hub of the web, the central nervous +system that touches most of the other parts and ties them together. +@^brain@> + +The structure of |main_control| itself is quite simple. There's a label +called |big_switch|, at which point the next token of input is fetched +using |get_x_token|. Then the program branches at high speed into one of +about 100 possible directions, based on the value of the current +mode and the newly fetched command code; the sum |abs(mode)+cur_cmd| +indicates what to do next. For example, the case `|vmode+letter|' arises +when a letter occurs in vertical mode (or internal vertical mode); this +case leads to instructions that initialize a new paragraph and enter +horizontal mode. + +The big |case| statement that contains this multiway switch has been labeled +|reswitch|, so that the program can |goto reswitch| when the next token +has already been fetched. Most of the cases are quite short; they call +an ``action procedure'' that does the work for that case, and then they +either |goto reswitch| or they ``fall through'' to the end of the |case| +statement, which returns control back to |big_switch|. Thus, |main_control| +is not an extremely large procedure, in spite of the multiplicity of things +it must do; it is small enough to be handled by \PASCAL\ compilers that put +severe restrictions on procedure size. +@!@^action procedure@> + +One case is singled out for special treatment, because it accounts for most +of \TeX's activities in typical applications. The process of reading simple +text and converting it into |char_node| records, while looking for ligatures +and kerns, is part of \TeX's ``inner loop''; the whole program runs +efficiently when its inner loop is fast, so this part has been written +with particular care. + +@ We shall concentrate first on the inner loop of |main_control|, deferring +consideration of the other cases until later. +@^inner loop@> + +@p @t\4@>@<Declare action procedures for use by |main_control|@>@; +@t\4@>@<Declare the procedure called |handle_right_brace|@>@; +static void main_control(void) /*governs \TeX's activities*/ +{@+ +int @!t; /*general-purpose temporary variable*/ +@<Initialize profiling@>@; +if (every_job!=null) begin_token_list(every_job, every_job_text); +big_switch: + @<record timing information@>@; + get_x_token();@/ +big_reswitch: + @<set current file, line, and command for the current time slot@>@; +@<Give diagnostic information, if requested@>; +switch (abs(mode)+cur_cmd) { +case hmode+letter: case hmode+other_char: + case hmode+char_given: goto main_loop; +case hmode+char_num: {@+scan_char_num();cur_chr=cur_val;goto main_loop;@+} +case hmode+no_boundary: {@+get_x_token(); + if ((cur_cmd==letter)||(cur_cmd==other_char)||(cur_cmd==char_given)|| + (cur_cmd==char_num)) cancel_boundary=true; + goto big_reswitch; + } +case hmode+spacer: if (space_factor==1000) goto append_normal_space; + else app_space();@+break; +case hmode+ex_space: case mmode+ex_space: goto append_normal_space; +@t\4@>@<Cases of |main_control| that are not part of the inner loop@>@; +} /*of the big |case| statement*/ +goto big_switch; +main_loop: +@<record timing information@>@; +@<set current file, line, and command for the current time slot@>@; +@<Append character |cur_chr| and the following characters (if~any) +to the current hlist in the current font; |goto big_reswitch| when a non-character +has been fetched@>; +append_normal_space: @<Append a normal inter-word space to the current list, +then |goto big_switch|@>; +} + +@ When a new token has just been fetched at |big_switch|, we have an +ideal place to monitor \TeX's activity. +@^debugging@> + +@<Give diagnostic information, if requested@>= +if (interrupt!=0) if (OK_to_interrupt) + {@+back_input();check_interrupt;goto big_switch; + } +#ifdef @!DEBUG +if (panicking) check_mem(false);@; +#endif +if (tracing_commands > 0) show_cur_cmd_chr() + +@ The following part of the program was first written in a structured +manner, according to the philosophy that ``premature optimization is +the root of all evil.'' Then it was rearranged into pieces of +spaghetti so that the most common actions could proceed with little or +no redundancy. + +The original unoptimized form of this algorithm resembles the +|reconstitute| procedure, which was described earlier in connection with +hyphenation. Again we have an implied ``cursor'' between characters +|cur_l| and |cur_r|. The main difference is that the |lig_stack| can now +contain a charnode as well as pseudo-ligatures; that stack is now +usually nonempty, because the next character of input (if any) has been +appended to it. In |main_control| we have +$$|cur_r|=\cases{|character(lig_stack)|,&if |lig_stack > null|;\cr + |font_bchar[cur_font]|,&otherwise;\cr}$$ +except when |character(lig_stack)==font_false_bchar[cur_font]|. +Several additional global variables are needed. + +@<Glob...@>= +static internal_font_number @!main_f; /*the current font*/ +static four_quarters @!main_i; /*character information bytes for |cur_l|*/ +static four_quarters @!main_j; /*ligature/kern command*/ +static font_index @!main_k; /*index into |font_info|*/ +static pointer @!main_p; /*temporary register for list manipulation*/ +static int @!main_s; /*space factor value*/ +static halfword @!bchar; /*boundary character of current font, or |non_char|*/ +static halfword @!false_bchar; /*nonexistent character matching |bchar|, or |non_char|*/ +static bool @!cancel_boundary; /*should the left boundary be ignored?*/ +static bool @!ins_disc; /*should we insert a discretionary node?*/ + +@ The boolean variables of the main loop are normally false, and always reset +to false before the loop is left. That saves us the extra work of initializing +each time. + +@<Set init...@>= +ligature_present=false;cancel_boundary=false;lft_hit=false;rt_hit=false; +ins_disc=false; + +@ We leave the |space_factor| unchanged if |sf_code(cur_chr)==0|; otherwise we +set it equal to |sf_code(cur_chr)|, except that it should never change +from a value less than 1000 to a value exceeding 1000. The most common +case is |sf_code(cur_chr)==1000|, so we want that case to be fast. + +The overall structure of the main loop is presented here. Some program labels +are inside the individual sections. +@^inner loop@> + +@d adjust_space_factor @t@>@;@/ + main_s=sf_code(cur_chr); + if (main_s==1000) space_factor=1000; + else if (main_s < 1000) + {@+if (main_s > 0) space_factor=main_s; + } + else if (space_factor < 1000) space_factor=1000; + else space_factor=main_s + +@<Append character |cur_chr|...@>= +adjust_space_factor;@/ +main_f=cur_font; +bchar=font_bchar[main_f];false_bchar=font_false_bchar[main_f]; +if (mode > 0) if (language!=clang) fix_language(); +fast_get_avail(lig_stack);font(lig_stack)=main_f;cur_l=qi(cur_chr); +character(lig_stack)=cur_l;@/ +cur_q=tail; +if (cancel_boundary) + {@+cancel_boundary=false;main_k=non_address; + } +else main_k=bchar_label[main_f]; +if (main_k==non_address) goto main_loop_move2; /*no left boundary processing*/ +cur_r=cur_l;cur_l=non_char; +goto main_lig_loop1; /*begin with cursor after left boundary*/ +@# +main_loop_wrapup: @<Make a ligature node, if |ligature_present|; insert a +null discretionary, if appropriate@>; +main_loop_move: @<If the cursor is immediately followed by the right boundary, +|goto big_reswitch|; if it's followed by an invalid character, |goto big_switch|; +otherwise move the cursor one step to the right and |goto main_lig_loop|@>; +main_loop_lookahead: @<Look ahead for another character, or leave |lig_stack| +empty if there's none there@>; +main_lig_loop: @<If there's a ligature/kern command relevant to |cur_l| and +|cur_r|, adjust the text appropriately; exit to |main_loop_wrapup|@>; +main_loop_move_lig: @<Move the cursor past a pseudo-ligature, then |goto main_loop_lookahead| +or |main_lig_loop|@>@; + +@ If |link(cur_q)| is nonnull when |wrapup| is invoked, |cur_q| points to +the list of characters that were consumed while building the ligature +character~|cur_l|. + +A discretionary break is not inserted for an explicit hyphen when we are in +restricted horizontal mode. In particular, this avoids putting discretionary +nodes inside of other discretionaries. +@^inner loop@> + +@d pack_lig(X) /*the parameter is either |rt_hit| or |false|*/ + {@+main_p=new_ligature(main_f, cur_l, link(cur_q)); + if (lft_hit) + {@+subtype(main_p)=2;lft_hit=false; + } + if (X) if (lig_stack==null) + {@+incr(subtype(main_p));rt_hit=false; + } + link(cur_q)=main_p;tail=main_p;ligature_present=false; + } + +@d wrapup(A) if (cur_l < non_char) + {@+if (link(cur_q) > null) + if (character(tail)==qi(hyphen_char[main_f])) ins_disc=true; + if (ligature_present) pack_lig(A); + if (ins_disc) + {@+ins_disc=false; + if (mode > 0) tail_append(new_disc()); + } + } + +@<Make a ligature node, if |ligature_present|;...@>= +wrapup(rt_hit) + +@ @<If the cursor is immediately followed by the right boundary...@>= +@^inner loop@> +if (lig_stack==null) goto big_reswitch; +cur_q=tail;cur_l=character(lig_stack); +main_loop_move1: if (!is_char_node(lig_stack)) goto main_loop_move_lig; +main_loop_move2: if ((cur_chr < font_bc[main_f])||(cur_chr > font_ec[main_f])) + {@+char_warning(main_f, cur_chr);free_avail(lig_stack);goto big_switch; + } +main_i=char_info(main_f, cur_l); +if (!char_exists(main_i)) + {@+char_warning(main_f, cur_chr);free_avail(lig_stack);goto big_switch; + } +link(tail)=lig_stack;tail=lig_stack /*|main_loop_lookahead| is next*/ + +@ Here we are at |main_loop_move_lig|. +When we begin this code we have |cur_q==tail| and |cur_l==character(lig_stack)|. + +@<Move the cursor past a pseudo-ligature...@>= +main_p=lig_ptr(lig_stack); +if (main_p > null) tail_append(main_p); /*append a single character*/ +temp_ptr=lig_stack;lig_stack=link(temp_ptr); +free_node(temp_ptr, small_node_size); +main_i=char_info(main_f, cur_l);ligature_present=true; +if (lig_stack==null) + if (main_p > null) goto main_loop_lookahead; + else cur_r=bchar; +else cur_r=character(lig_stack); +goto main_lig_loop + +@ The result of \.{\\char} can participate in a ligature or kern, so we must +look ahead for it. + +@<Look ahead for another character...@>= +get_next(); /*set only |cur_cmd| and |cur_chr|, for speed*/ +if (cur_cmd==letter) goto main_loop_lookahead1; +if (cur_cmd==other_char) goto main_loop_lookahead1; +if (cur_cmd==char_given) goto main_loop_lookahead1; +x_token(); /*now expand and set |cur_cmd|, |cur_chr|, |cur_tok|*/ +if (cur_cmd==letter) goto main_loop_lookahead1; +if (cur_cmd==other_char) goto main_loop_lookahead1; +if (cur_cmd==char_given) goto main_loop_lookahead1; +if (cur_cmd==char_num) + {@+scan_char_num();cur_chr=cur_val;goto main_loop_lookahead1; + } +if (cur_cmd==no_boundary) bchar=non_char; +cur_r=bchar;lig_stack=null;goto main_lig_loop; +main_loop_lookahead1: adjust_space_factor; +fast_get_avail(lig_stack);font(lig_stack)=main_f; +cur_r=qi(cur_chr);character(lig_stack)=cur_r; +if (cur_r==false_bchar) cur_r=non_char /*this prevents spurious ligatures*/ + +@ Even though comparatively few characters have a lig/kern program, several +of the instructions here count as part of \TeX's inner loop, since a +@^inner loop@> +potentially long sequential search must be performed. For example, tests with +Computer Modern Roman showed that about 40 per cent of all characters +actually encountered in practice had a lig/kern program, and that about four +lig/kern commands were investigated for every such character. + +At the beginning of this code we have |main_i==char_info(main_f, cur_l)|. + +@<If there's a ligature/kern command...@>= +if (char_tag(main_i)!=lig_tag) goto main_loop_wrapup; +if (cur_r==non_char) goto main_loop_wrapup; +main_k=lig_kern_start(main_f, main_i);main_j=font_info[main_k].qqqq; +if (skip_byte(main_j) <= stop_flag) goto main_lig_loop2; +main_k=lig_kern_restart(main_f, main_j); +main_lig_loop1: main_j=font_info[main_k].qqqq; +main_lig_loop2: if (next_char(main_j)==cur_r) + if (skip_byte(main_j) <= stop_flag) + @<Do ligature or kern command, returning to |main_lig_loop| or |main_loop_wrapup| +or |main_loop_move|@>; +if (skip_byte(main_j)==qi(0)) incr(main_k); +else{@+if (skip_byte(main_j) >= stop_flag) goto main_loop_wrapup; + main_k=main_k+qo(skip_byte(main_j))+1; + } +goto main_lig_loop1 + +@ When a ligature or kern instruction matches a character, we know from +|read_font_info| that the character exists in the font, even though we +haven't verified its existence in the normal way. + +This section could be made into a subroutine, if the code inside +|main_control| needs to be shortened. + +\chardef\@@='174 % vertical line to indicate character retention + +@<Do ligature or kern command...@>= +{@+if (op_byte(main_j) >= kern_flag) + {@+wrapup(rt_hit); + tail_append(new_kern(char_kern(main_f, main_j)));goto main_loop_move; + } +if (cur_l==non_char) lft_hit=true; +else if (lig_stack==null) rt_hit=true; +check_interrupt; /*allow a way out in case there's an infinite ligature loop*/ +switch (op_byte(main_j)) { +case qi(1): case qi(5): {@+cur_l=rem_byte(main_j); /*\.{=:\@@}, \.{=:\@@>}*/ + main_i=char_info(main_f, cur_l);ligature_present=true; + } @+break; +case qi(2): case qi(6): {@+cur_r=rem_byte(main_j); /*\.{\@@=:}, \.{\@@=:>}*/ + if (lig_stack==null) /*right boundary character is being consumed*/ + {@+lig_stack=new_lig_item(cur_r);bchar=non_char; + } + else if (is_char_node(lig_stack)) /*|link(lig_stack)==null|*/ + {@+main_p=lig_stack;lig_stack=new_lig_item(cur_r); + lig_ptr(lig_stack)=main_p; + } + else character(lig_stack)=cur_r; + } @+break; +case qi(3): {@+cur_r=rem_byte(main_j); /*\.{\@@=:\@@}*/ + main_p=lig_stack;lig_stack=new_lig_item(cur_r); + link(lig_stack)=main_p; + } @+break; +case qi(7): case qi(11): {@+wrapup(false); /*\.{\@@=:\@@>}, \.{\@@=:\@@>>}*/ + cur_q=tail;cur_l=rem_byte(main_j); + main_i=char_info(main_f, cur_l);ligature_present=true; + } @+break; +default:{@+cur_l=rem_byte(main_j);ligature_present=true; /*\.{=:}*/ + if (lig_stack==null) goto main_loop_wrapup; + else goto main_loop_move1; + } +} +if (op_byte(main_j) > qi(4)) + if (op_byte(main_j)!=qi(7)) goto main_loop_wrapup; +if (cur_l < non_char) goto main_lig_loop; +main_k=bchar_label[main_f];goto main_lig_loop1; +} + +@ The occurrence of blank spaces is almost part of \TeX's inner loop, +@^inner loop@> +since we usually encounter about one space for every five non-blank characters. +Therefore |main_control| gives second-highest priority to ordinary spaces. + +When a glue parameter like \.{\\spaceskip} is set to `\.{0pt}', we will +see to it later that the corresponding glue specification is precisely +|zero_glue|, not merely a pointer to some specification that happens +to be full of zeroes. Therefore it is simple to test whether a glue parameter +is zero or~not. + +@<Append a normal inter-word space...@>= +if (space_skip==zero_glue) + {@+@<Find the glue specification, |main_p|, for text spaces in the current +font@>; + temp_ptr=new_glue(main_p); + } +else temp_ptr=new_param_glue(space_skip_code); +link(tail)=temp_ptr;tail=temp_ptr; +goto big_switch + +@ Having |font_glue| allocated for each text font saves both time and memory. +If any of the three spacing parameters are subsequently changed by the +use of \.{\\fontdimen}, the |find_font_dimen| procedure deallocates the +|font_glue| specification allocated here. + +@<Find the glue specification...@>= +{@+main_p=font_glue[cur_font]; +if (main_p==null) + {@+main_p=new_spec(zero_glue);main_k=param_base[cur_font]+space_code; + width(main_p)=font_info[main_k].sc; /*that's |space(cur_font)|*/ + stretch(main_p)=font_info[main_k+1].sc; /*and |space_stretch(cur_font)|*/ + shrink(main_p)=font_info[main_k+2].sc; /*and |space_shrink(cur_font)|*/ + font_glue[cur_font]=main_p; + } +} + +@ @<Declare act...@>= +static void app_space(void) /*handle spaces when |space_factor!=1000|*/ +{@+pointer @!q; /*glue node*/ +if ((space_factor >= 2000)&&(xspace_skip!=zero_glue)) + q=new_param_glue(xspace_skip_code); +else{@+if (space_skip!=zero_glue) main_p=space_skip; + else@<Find the glue specification...@>; + main_p=new_spec(main_p); + @<Modify the glue specification in |main_p| according to the space factor@>; + q=new_glue(main_p);glue_ref_count(main_p)=null; + } +link(tail)=q;tail=q; +} + +@ @<Modify the glue specification in |main_p| according to the space factor@>= +if (space_factor >= 2000) width(main_p)=width(main_p)+extra_space(cur_font); +stretch(main_p)=xn_over_d(stretch(main_p), space_factor, 1000); +shrink(main_p)=xn_over_d(shrink(main_p), 1000, space_factor) + +@ Whew---that covers the main loop. We can now proceed at a leisurely +pace through the other combinations of possibilities. + +@d any_mode(A) case vmode+A: case hmode+A: + case mmode+A /*for mode-independent commands*/ + +@<Cases of |main_control| that are not part of the inner loop@>= +any_mode(relax): case vmode+spacer: case mmode+spacer: + case mmode+no_boundary: do_nothing;@+break; +any_mode(ignore_spaces): {@+@<Get the next non-blank non-call...@>; + goto big_reswitch; + } +case vmode+stop: + if (its_all_over()) + { @<record the end of \TeX@>@; + return; /*this is the only way out*/ + } + @+break; +@t\4@>@<Forbidden cases detected in |main_control|@>@+@, any_mode(mac_param): + report_illegal_case();@+break; +@<Math-only cases in non-math modes, or vice versa@>: insert_dollar_sign();@+break; +@t\4@>@<Cases of |main_control| that build boxes and lists@>@; +@t\4@>@<Cases of |main_control| that don't depend on |mode|@>@; +@t\4@>@<Cases of |main_control| that are for extensions to \TeX@>@; + +@ Here is a list of cases where the user has probably gotten into or out of math +mode by mistake. \TeX\ will insert a dollar sign and rescan the current token. + +@d non_math(A) case vmode+A: case hmode+A + +@<Math-only cases in non-math modes...@>= +non_math(sup_mark): non_math(sub_mark): non_math(math_char_num): +non_math(math_given): non_math(math_comp): non_math(delim_num): +non_math(left_right): non_math(above): non_math(radical): +non_math(math_style): non_math(math_choice): non_math(vcenter): +non_math(non_script): non_math(mkern): non_math(limit_switch): +non_math(mskip): non_math(math_accent): +case mmode+endv: case mmode+par_end: case mmode+stop: + case mmode+vskip: case mmode+un_vbox: +case mmode+valign: case mmode+hrule + +@ @<Declare action...@>= +static void insert_dollar_sign(void) +{@+back_input();cur_tok=math_shift_token+'$'; +print_err("Missing $ inserted"); +@.Missing \$ inserted@> +help2("I've inserted a begin-math/end-math symbol since I think",@/ +"you left one out. Proceed, with fingers crossed.");ins_error(); +} + +@ When erroneous situations arise, \TeX\ usually issues an error message +specific to the particular error. For example, `\.{\\noalign}' should +not appear in any mode, since it is recognized by the |align_peek| routine +in all of its legitimate appearances; a special error message is given +when `\.{\\noalign}' occurs elsewhere. But sometimes the most appropriate +error message is simply that the user is not allowed to do what he or she +has attempted. For example, `\.{\\moveleft}' is allowed only in vertical mode, +and `\.{\\lower}' only in non-vertical modes. Such cases are enumerated +here and in the other sections referred to under `See also \dots.' + +@<Forbidden cases...@>= +case vmode+vmove: case hmode+hmove: case mmode+hmove: any_mode(last_item): + +@ The `|you_cant|' procedure prints a line saying that the current command +is illegal in the current mode; it identifies these things symbolically. + +@<Declare action...@>= +static void you_cant(void) +{@+print_err("You can't use `"); +@.You can't use x in y mode@> +print_cmd_chr(cur_cmd, cur_chr); +print("' in ");print_mode(mode); +} + +@ @<Declare act...@>= +static void report_illegal_case(void) +{@+you_cant(); +help4("Sorry, but I'm not programmed to handle this case;",@/ +"I'll just pretend that you didn't ask for it.",@/ +"If you're in the wrong mode, you might be able to",@/ +"return to the right one by typing `I}' or `I$' or `I\\par'.");@/ +error(); +} + +@ Some operations are allowed only in privileged modes, i.e., in cases +that |mode > 0|. The |privileged| function is used to detect violations +of this rule; it issues an error message and returns |false| if the +current |mode| is negative. + +@<Declare act...@>= +static bool privileged(void) +{@+if (mode > 0) return true; +else{@+report_illegal_case();return false; + } +} + +@ Either \.{\\dump} or \.{\\end} will cause |main_control| to enter the +endgame, since both of them have `|stop|' as their command code. + +@<Put each...@>= +primitive("end", stop, 0);@/ +@!@:end\_}{\.{\\end} primitive@> +primitive("dump", stop, 1);@/ +@!@:dump\_}{\.{\\dump} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case stop: if (chr_code==1) print_esc("dump");@+else print_esc("end");@+break; + +@ We don't want to leave |main_control| immediately when a |stop| command +is sensed, because it may be necessary to invoke an \.{\\output} routine +several times before things really grind to a halt. (The output routine +might even say `\.{\\gdef\\end\{...\}}', to prolong the life of the job.) +Therefore |its_all_over| is |true| only when the current page +and contribution list are empty, and when the last output was not a +``dead cycle.'' + +@<Declare act...@>= +static bool its_all_over(void) /*do this when \.{\\end} or \.{\\dump} occurs*/ +{@+ +if (privileged()) + {@+if ((page_head==page_tail)&&(head==tail)&&(dead_cycles==0)) + {@+return true; + } + back_input(); /*we will try to end again after ejecting residual material*/ + tail_append(new_null_box()); + width(tail)=hsize; + tail_append(new_glue(fill_glue)); + tail_append(new_penalty(-010000000000));@/ + build_page(); /*append \.{\\hbox to \\hsize\{\}\\vfill\\penalty-'10000000000}*/ + } +return false; +} + +@* Building boxes and lists. +The most important parts of |main_control| are concerned with \TeX's +chief mission of box-making. We need to control the activities that put +entries on vlists and hlists, as well as the activities that convert +those lists into boxes. All of the necessary machinery has already been +developed; it remains for us to ``push the buttons'' at the right times. + +@ As an introduction to these routines, let's consider one of the simplest +cases: What happens when `\.{\\hrule}' occurs in vertical mode, or +`\.{\\vrule}' in horizontal mode or math mode? The code in |main_control| +is short, since the |scan_rule_spec| routine already does most of what is +required; thus, there is no need for a special action procedure. + +Note that baselineskip calculations are disabled after a rule in vertical +mode, by setting |prev_depth=ignore_depth|. + +@<Cases of |main_control| that build...@>= +case vmode+hrule: case hmode+vrule: case mmode+vrule: {@+tail_append(scan_rule_spec()); + if (abs(mode)==vmode) prev_depth=ignore_depth; + else if (abs(mode)==hmode) space_factor=1000; + } @+break; + +@ The processing of things like \.{\\hskip} and \.{\\vskip} is slightly +more complicated. But the code in |main_control| is very short, since +it simply calls on the action routine |append_glue|. Similarly, \.{\\kern} +activates |append_kern|. + +@<Cases of |main_control| that build...@>= +case vmode+vskip: case hmode+hskip: case mmode+hskip: + case mmode+mskip: append_glue();@+break; +any_mode(kern): case mmode+mkern: append_kern();@+break; + +@ The |hskip| and |vskip| command codes are used for control sequences +like \.{\\hss} and \.{\\vfil} as well as for \.{\\hskip} and \.{\\vskip}. +The difference is in the value of |cur_chr|. + +@d fil_code 0 /*identifies \.{\\hfil} and \.{\\vfil}*/ +@d fill_code 1 /*identifies \.{\\hfill} and \.{\\vfill}*/ +@d ss_code 2 /*identifies \.{\\hss} and \.{\\vss}*/ +@d fil_neg_code 3 /*identifies \.{\\hfilneg} and \.{\\vfilneg}*/ +@d skip_code 4 /*identifies \.{\\hskip} and \.{\\vskip}*/ +@d mskip_code 5 /*identifies \.{\\mskip}*/ + +@<Put each...@>= +primitive("hskip", hskip, skip_code);@/ +@!@:hskip\_}{\.{\\hskip} primitive@> +primitive("hfil", hskip, fil_code); +@!@:hfil\_}{\.{\\hfil} primitive@> +primitive("hfill", hskip, fill_code);@/ +@!@:hfill\_}{\.{\\hfill} primitive@> +primitive("hss", hskip, ss_code); +@!@:hss\_}{\.{\\hss} primitive@> +primitive("hfilneg", hskip, fil_neg_code);@/ +@!@:hfil\_neg\_}{\.{\\hfilneg} primitive@> +primitive("vskip", vskip, skip_code);@/ +@!@:vskip\_}{\.{\\vskip} primitive@> +primitive("vfil", vskip, fil_code); +@!@:vfil\_}{\.{\\vfil} primitive@> +primitive("vfill", vskip, fill_code);@/ +@!@:vfill\_}{\.{\\vfill} primitive@> +primitive("vss", vskip, ss_code); +@!@:vss\_}{\.{\\vss} primitive@> +primitive("vfilneg", vskip, fil_neg_code);@/ +@!@:vfil\_neg\_}{\.{\\vfilneg} primitive@> +primitive("mskip", mskip, mskip_code);@/ +@!@:mskip\_}{\.{\\mskip} primitive@> +primitive("kern", kern, explicit); +@!@:kern\_}{\.{\\kern} primitive@> +primitive("mkern", mkern, mu_glue);@/ +@!@:mkern\_}{\.{\\mkern} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case hskip: switch (chr_code) { + case skip_code: print_esc("hskip");@+break; + case fil_code: print_esc("hfil");@+break; + case fill_code: print_esc("hfill");@+break; + case ss_code: print_esc("hss");@+break; + default:print_esc("hfilneg"); + } @+break; +case vskip: switch (chr_code) { + case skip_code: print_esc("vskip");@+break; + case fil_code: print_esc("vfil");@+break; + case fill_code: print_esc("vfill");@+break; + case ss_code: print_esc("vss");@+break; + default:print_esc("vfilneg"); + } @+break; +case mskip: print_esc("mskip");@+break; +case kern: print_esc("kern");@+break; +case mkern: print_esc("mkern");@+break; + +@ All the work relating to glue creation has been relegated to the +following subroutine. It does not call |build_page|, because it is +used in at least one place where that would be a mistake. + +@<Declare action...@>= +static void append_glue(void) +{@+small_number s; /*modifier of skip command*/ +s=cur_chr; +switch (s) { +case fil_code: cur_val=fil_glue;@+break; +case fill_code: cur_val=fill_glue;@+break; +case ss_code: cur_val=ss_glue;@+break; +case fil_neg_code: cur_val=fil_neg_glue;@+break; +case skip_code: scan_glue(glue_val);@+break; +case mskip_code: scan_glue(mu_val); +} /*now |cur_val| points to the glue specification*/ +tail_append(new_glue(cur_val)); +if (s >= skip_code) + {@+decr(glue_ref_count(cur_val)); + if (s > skip_code) subtype(tail)=mu_glue; + } +} + +@ @<Declare act...@>= +static void append_kern(void) +{@+quarterword s; /*|subtype| of the kern node*/ +s=cur_chr;scan_dimen(s==mu_glue, false, false); +tail_append(new_kern(cur_val));subtype(tail)=s; +} + +@ Many of the actions related to box-making are triggered by the appearance +of braces in the input. For example, when the user says `\.{\\hbox} +\.{to} \.{100pt\{$\langle\,\hbox{\rm hlist}\,\rangle$\}}' in vertical mode, +the information about the box size (100pt, |exactly|) is put onto |save_stack| +with a level boundary word just above it, and |cur_group=adjusted_hbox_group|; +\TeX\ enters restricted horizontal mode to process the hlist. The right +brace eventually causes |save_stack| to be restored to its former state, +at which time the information about the box size (100pt, |exactly|) is +available once again; a box is packaged and we leave restricted horizontal +mode, appending the new box to the current list of the enclosing mode +(in this case to the current list of vertical mode), followed by any +vertical adjustments that were removed from the box by |hpack|. + +The next few sections of the program are therefore concerned with the +treatment of left and right curly braces. + +@ If a left brace occurs in the middle of a page or paragraph, it simply +introduces a new level of grouping, and the matching right brace will not have +such a drastic effect. Such grouping affects neither the mode nor the +current list. + +@<Cases of |main_control| that build...@>= +non_math(left_brace): new_save_level(simple_group);@+break; +any_mode(begin_group): new_save_level(semi_simple_group);@+break; +any_mode(end_group): if (cur_group==semi_simple_group) unsave(); + else off_save();@+break; + +@ We have to deal with errors in which braces and such things are not +properly nested. Sometimes the user makes an error of commission by +inserting an extra symbol, but sometimes the user makes an error of omission. +\TeX\ can't always tell one from the other, so it makes a guess and tries +to avoid getting into a loop. + +The |off_save| routine is called when the current group code is wrong. It tries +to insert something into the user's input that will help clean off +the top level. + +@<Declare act...@>= +static void off_save(void) +{@+pointer p; /*inserted token*/ +if (cur_group==bottom_level) + @<Drop current token and complain that it was unmatched@>@; +else{@+back_input();p=get_avail();link(temp_head)=p; + print_err("Missing "); + @<Prepare to insert a token that matches |cur_group|, and print what it +is@>; + print(" inserted");ins_list(link(temp_head)); + help5("I've inserted something that you may have forgotten.",@/ + "(See the <inserted text> above.)",@/ + "With luck, this will get me unwedged. But if you",@/ + "really didn't forget anything, try typing `2' now; then",@/ + "my insertion and my current dilemma will both disappear."); + error(); + } +} + +@ At this point, |link(temp_head)==p|, a pointer to an empty one-word node. + +@<Prepare to insert a token that matches |cur_group|...@>= +switch (cur_group) { +case semi_simple_group: {@+info(p)=cs_token_flag+frozen_end_group; + print_esc("endgroup"); +@.Missing \\endgroup inserted@> + } @+break; +case math_shift_group: {@+info(p)=math_shift_token+'$';print_char('$'); +@.Missing \$ inserted@> + } @+break; +case math_left_group: {@+info(p)=cs_token_flag+frozen_right;link(p)=get_avail(); + p=link(p);info(p)=other_token+'.';print_esc("right."); +@.Missing \\right\hbox{.} inserted@> +@^null delimiter@> + } @+break; +default:{@+info(p)=right_brace_token+'}';print_char('}'); +@.Missing \} inserted@> + } +} + +@ @<Drop current token and complain that it was unmatched@>= +{@+print_err("Extra ");print_cmd_chr(cur_cmd, cur_chr); +@.Extra x@> +help1("Things are pretty mixed up, but I think the worst is over.");@/ +error(); +} + +@ The routine for a |right_brace| character branches into many subcases, +since a variety of things may happen, depending on |cur_group|. Some +types of groups are not supposed to be ended by a right brace; error +messages are given in hopes of pinpointing the problem. Most branches +of this routine will be filled in later, when we are ready to understand +them; meanwhile, we must prepare ourselves to deal with such errors. + +@<Cases of |main_control| that build...@>= +any_mode(right_brace): handle_right_brace();@+break; + +@ @<Declare the procedure called |handle_right_brace|@>= +static void handle_right_brace(void) +{@+pointer p, @!q; /*for short-term use*/ +scaled @!d; /*holds |split_max_depth| in |insert_group|*/ +int @!f; /*holds |floating_penalty| in |insert_group|*/ +switch (cur_group) { +case simple_group: unsave();@+break; +case bottom_level: {@+print_err("Too many }'s"); +@.Too many \}'s@> + help2("You've closed more groups than you opened.",@/ + "Such booboos are generally harmless, so keep going.");error(); + } @+break; +case semi_simple_group: case math_shift_group: + case math_left_group: extra_right_brace();@+break; +@t\4@>@<Cases of |handle_right_brace| where a |right_brace| triggers a delayed +action@>@; +default:confusion("rightbrace"); +@:this can't happen rightbrace}{\quad rightbrace@> +} +} + +@ @<Declare act...@>= +static void extra_right_brace(void) +{@+print_err("Extra }, or forgotten "); +@.Extra \}, or forgotten x@> +switch (cur_group) { +case semi_simple_group: print_esc("endgroup");@+break; +case math_shift_group: print_char('$');@+break; +case math_left_group: print_esc("right"); +} @/ +help5("I've deleted a group-closing symbol because it seems to be",@/ +"spurious, as in `$x}$'. But perhaps the } is legitimate and",@/ +"you forgot something else, as in `\\hbox{$x}'. In such cases",@/ +"the way to recover is to insert both the forgotten and the",@/ +"deleted material, e.g., by typing `I$}'.");error(); +incr(align_state); +} + +@ Here is where we clear the parameters that are supposed to revert to their +default values after every paragraph and when internal vertical mode is entered. + +@<Declare act...@>= +static void normal_paragraph(void) +{@+if (looseness!=0) eq_word_define(int_base+looseness_code, 0); +if (hang_indent!=0) eq_word_define(dimen_base+hang_indent_code, 0); +if (hang_after!=1) eq_word_define(int_base+hang_after_code, 1); +if (par_shape_ptr!=null) eq_define(par_shape_loc, shape_ref, null); +if (inter_line_penalties_ptr!=null) + eq_define(inter_line_penalties_loc, shape_ref, null); +} + +@ Now let's turn to the question of how \.{\\hbox} is treated. We actually +need to consider also a slightly larger context, since constructions like +`\.{\\setbox3=}\penalty0\.{\\hbox...}' and +`\.{\\leaders}\penalty0\.{\\hbox...}' and +`\.{\\lower3.8pt\\hbox...}' +are supposed to invoke quite +different actions after the box has been packaged. Conversely, +constructions like `\.{\\setbox3=}' can be followed by a variety of +different kinds of boxes, and we would like to encode such things in an +efficient way. + +In other words, there are two problems: to represent the context of a box, +and to represent its type. + +The first problem is solved by putting a ``context code'' on the |save_stack|, +just below the two entries that give the dimensions produced by |scan_spec|. +The context code is either a (signed) shift amount, or it is a large +integer | >= box_flag|, where |box_flag==@t$2^{30}$@>|. Codes |box_flag| through +|global_box_flag-1| represent `\.{\\setbox0}' through `\.{\\setbox32767}'; +codes |global_box_flag| through |ship_out_flag-1| represent +`\.{\\global\\setbox0}' through `\.{\\global\\setbox32767}'; +code |ship_out_flag| represents `\.{\\shipout}'; and codes |leader_flag| +through |leader_flag+2| represent `\.{\\leaders}', `\.{\\cleaders}', +and `\.{\\xleaders}'. + +The second problem is solved by giving the command code |make_box| to all +control sequences that produce a box, and by using the following |chr_code| +values to distinguish between them: |box_code|, |copy_code|, |last_box_code|, +|vsplit_code|, |vtop_code|, |vtop_code+vmode|, and |vtop_code+hmode|, where +the latter two are used to denote \.{\\vbox} and \.{\\hbox}, respectively. + +@d box_flag 010000000000 /*context code for `\.{\\setbox0}'*/ +@d global_box_flag 010000100000 /*context code for `\.{\\global\\setbox0}'*/ +@d ship_out_flag 010000200000 /*context code for `\.{\\shipout}'*/ +@d leader_flag 010000200001 /*context code for `\.{\\leaders}'*/ +@d box_code 0 /*|chr_code| for `\.{\\box}'*/ +@d copy_code 1 /*|chr_code| for `\.{\\copy}'*/ +@d last_box_code 2 /*|chr_code| for `\.{\\lastbox}'*/ +@d vsplit_code 3 /*|chr_code| for `\.{\\vsplit}'*/ +@d vtop_code 4 /*|chr_code| for `\.{\\vtop}'*/ + +@<Put each...@>= +primitive("moveleft", hmove, 1); +@!@:move\_left\_}{\.{\\moveleft} primitive@> +primitive("moveright", hmove, 0);@/ +@!@:move\_right\_}{\.{\\moveright} primitive@> +primitive("raise", vmove, 1); +@!@:raise\_}{\.{\\raise} primitive@> +primitive("lower", vmove, 0); +@!@:lower\_}{\.{\\lower} primitive@> +@# +primitive("box", make_box, box_code); +@!@:box\_}{\.{\\box} primitive@> +primitive("copy", make_box, copy_code); +@!@:copy\_}{\.{\\copy} primitive@> +primitive("lastbox", make_box, last_box_code); +@!@:last\_box\_}{\.{\\lastbox} primitive@> +primitive("vsplit", make_box, vsplit_code); +@!@:vsplit\_}{\.{\\vsplit} primitive@> +primitive("vtop", make_box, vtop_code);@/ +@!@:vtop\_}{\.{\\vtop} primitive@> +primitive("vbox", make_box, vtop_code+vmode); +@!@:vbox\_}{\.{\\vbox} primitive@> +primitive("hbox", make_box, vtop_code+hmode);@/ +@!@:hbox\_}{\.{\\hbox} primitive@> +primitive("shipout", leader_ship, a_leaders-1); /*|ship_out_flag==leader_flag-1|*/ +@!@:ship\_out\_}{\.{\\shipout} primitive@> +primitive("leaders", leader_ship, a_leaders); +@!@:leaders\_}{\.{\\leaders} primitive@> +primitive("cleaders", leader_ship, c_leaders); +@!@:c\_leaders\_}{\.{\\cleaders} primitive@> +primitive("xleaders", leader_ship, x_leaders); +@!@:x\_leaders\_}{\.{\\xleaders} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case hmove: if (chr_code==1) print_esc("moveleft");@+else print_esc("moveright");@+break; +case vmove: if (chr_code==1) print_esc("raise");@+else print_esc("lower");@+break; +case make_box: switch (chr_code) { + case box_code: print_esc("box");@+break; + case copy_code: print_esc("copy");@+break; + case last_box_code: print_esc("lastbox");@+break; + case vsplit_code: print_esc("vsplit");@+break; + case vtop_code: print_esc("vtop");@+break; + case vtop_code+vmode: print_esc("vbox");@+break; + default:print_esc("hbox"); + } @+break; +case leader_ship: if (chr_code==a_leaders) print_esc("leaders"); + else if (chr_code==c_leaders) print_esc("cleaders"); + else if (chr_code==x_leaders) print_esc("xleaders"); + else print_esc("shipout");@+break; + +@ Constructions that require a box are started by calling |scan_box| with +a specified context code. The |scan_box| routine verifies +that a |make_box| command comes next and then it calls |begin_box|. + +@<Cases of |main_control| that build...@>= +case vmode+hmove: case hmode+vmove: case mmode+vmove: {@+t=cur_chr; + scan_normal_dimen; + if (t==0) scan_box(cur_val);@+else scan_box(-cur_val); + } @+break; +any_mode(leader_ship): scan_box(leader_flag-a_leaders+cur_chr);@+break; +any_mode(make_box): begin_box(0);@+break; + +@ The global variable |cur_box| will point to a newly made box. If the box +is void, we will have |cur_box==null|. Otherwise we will have +|type(cur_box)==hlist_node| or |vlist_node| or |rule_node|; the |rule_node| +case can occur only with leaders. + +@<Glob...@>= +static pointer @!cur_box; /*box to be placed into its context*/ + +@ The |box_end| procedure does the right thing with |cur_box|, if +|box_context| represents the context as explained above. + +@<Declare act...@>= +static void box_end(int @!box_context) +{@+pointer p; /*|ord_noad| for new box in math mode*/ +small_number @!a; /*global prefix*/ +if (box_context < box_flag) @<Append box |cur_box| to the current list, shifted +by |box_context|@>@; +else if (box_context < ship_out_flag) @<Store \(c)|cur_box| in a box register@>@; +else if (cur_box!=null) + if (box_context > ship_out_flag) @<Append a new leader node that uses |cur_box|@>@; + else ship_out(cur_box); +} + +@ The global variable |adjust_tail| will be non-null if and only if the +current box might include adjustments that should be appended to the +current vertical list. + +@<Append box |cur_box| to the current...@>= +{@+if (cur_box!=null) + {@+shift_amount(cur_box)=box_context; + if (abs(mode)==vmode) + {@+append_to_vlist(cur_box); + if (adjust_tail!=null) + {@+if (adjust_head!=adjust_tail) + {@+link(tail)=link(adjust_head);tail=adjust_tail; + } + adjust_tail=null; + } + if (mode > 0) build_page(); + } + else{@+if (abs(mode)==hmode) space_factor=1000; + else{@+p=new_noad(); + math_type(nucleus(p))=sub_box; + info(nucleus(p))=cur_box;cur_box=p; + } + link(tail)=cur_box;tail=cur_box; + } + } +} + +@ @<Store \(c)|cur_box| in a box register@>= +{@+if (box_context < global_box_flag) + {@+cur_val=box_context-box_flag;a=0; + } +else{@+cur_val=box_context-global_box_flag;a=4; + } +if (cur_val < 256) define(box_base+cur_val, box_ref, cur_box); +else sa_def_box; +} + +@ @<Append a new leader node...@>= +{@+@<Get the next non-blank non-relax...@>; +if (((cur_cmd==hskip)&&(abs(mode)!=vmode))||@| + ((cur_cmd==vskip)&&(abs(mode)==vmode))) + {@+append_glue();subtype(tail)=box_context-(leader_flag-a_leaders); + leader_ptr(tail)=cur_box; + } +else{@+print_err("Leaders not followed by proper glue"); +@.Leaders not followed by...@> + help3("You should say `\\leaders <box or rule><hskip or vskip>'.",@/ + "I found the <box or rule>, but there's no suitable",@/ + "<hskip or vskip>, so I'm ignoring these leaders.");back_error(); + flush_node_list(cur_box); + } +} + +@ Now that we can see what eventually happens to boxes, we can consider +the first steps in their creation. The |begin_box| routine is called when +|box_context| is a context specification, |cur_chr| specifies the type of +box desired, and |cur_cmd==make_box|. + +@<Declare act...@>= +static void begin_box(int @!box_context) +{@+ +pointer @!p, @!q; /*run through the current list*/ +int @!m; /*the length of a replacement list*/ +halfword @!k; /*0 or |vmode| or |hmode|*/ +halfword @!n; /*a box number*/ +switch (cur_chr) { +case box_code: {@+scan_register_num();fetch_box(cur_box); + change_box(null); /*the box becomes void, at the same level*/ + } @+break; +case copy_code: {@+scan_register_num();fetch_box(q);cur_box=copy_node_list(q); + } @+break; +case last_box_code: @<If the current list ends with a box node, delete it +from the list and make |cur_box| point to it; otherwise set |cur_box:=null|@>@;@+break; +case vsplit_code: @<Split off part of a vertical box, make |cur_box| point +to it@>@;@+break; +default:@<Initiate the construction of an hbox or vbox, then |return|@>@; +} @/ +box_end(box_context); /*in simple cases, we use the box immediately*/ +} + +@ Note that the condition |!is_char_node(tail)| implies that |head!=tail|, +since |head| is a one-word node. + +@<If the current list ends with a box node, delete it...@>= +{@+cur_box=null; +if (abs(mode)==mmode) + {@+you_cant();help1("Sorry; this \\lastbox will be void.");error(); + } +else if ((mode==vmode)&&(head==tail)) + {@+you_cant(); + help2("Sorry...I usually can't take things from the current page.",@/ + "This \\lastbox will therefore be void.");error(); + } +else{@+if (!is_char_node(tail)) + if ((type(tail)==hlist_node)||(type(tail)==vlist_node)) + @<Remove the last box, unless it's part of a discretionary@>; + } +} + +@ @<Remove the last box...@>= +{@+q=head; +@/do@+{p=q; +if (!is_char_node(q)) if (type(q)==disc_node) + {@+for (m=1; m<=replace_count(q); m++) p=link(p); + if (p==tail) goto done; + } +q=link(p); +}@+ while (!(q==tail)); +cur_box=tail;shift_amount(cur_box)=0; +tail=p;link(p)=null; +done: ;} + +@ Here we deal with things like `\.{\\vsplit 13 to 100pt}'. + +@<Split off part of a vertical box, make |cur_box| point to it@>= +{@+scan_register_num();n=cur_val; +if (!scan_keyword("to")) +@.to@> + {@+print_err("Missing `to' inserted"); +@.Missing `to' inserted@> + help2("I'm working on `\\vsplit<box number> to <dimen>';",@/ + "will look for the <dimen> next.");error(); + } +scan_normal_dimen; +cur_box=vsplit(n, cur_val); +} + +@ Here is where we enter restricted horizontal mode or internal vertical +mode, in order to make a box. + +@<Initiate the construction of an hbox or vbox, then |return|@>= +{@+k=cur_chr-vtop_code;saved(0)=box_context; +if (k==hmode) + if ((box_context < box_flag)&&(abs(mode)==vmode)) + scan_spec(adjusted_hbox_group, true); + else scan_spec(hbox_group, true); +else{@+if (k==vmode) scan_spec(vbox_group, true); + else{@+scan_spec(vtop_group, true);k=vmode; + } + normal_paragraph(); + } +push_nest();mode=-k; +if (k==vmode) + {@+prev_depth=ignore_depth; + if (every_vbox!=null) begin_token_list(every_vbox, every_vbox_text); + } +else{@+space_factor=1000; + if (every_hbox!=null) begin_token_list(every_hbox, every_hbox_text); + } +return; +} + +@ @<Declare act...@>= +static void scan_box(int @!box_context) + /*the next input should specify a box or perhaps a rule*/ +{@+@<Get the next non-blank non-relax...@>; +if (cur_cmd==make_box) begin_box(box_context); +else if ((box_context >= leader_flag)&&((cur_cmd==hrule)||(cur_cmd==vrule))) + {@+cur_box=scan_rule_spec();box_end(box_context); + } +else{@+@t@>@;@/ + print_err("A <box> was supposed to be here");@/ +@.A <box> was supposed to...@> + help3("I was expecting to see \\hbox or \\vbox or \\copy or \\box or",@/ + "something like that. So you might find something missing in",@/ + "your output. But keep trying; you can fix this later.");back_error(); + } +} + +@ When the right brace occurs at the end of an \.{\\hbox} or \.{\\vbox} or +\.{\\vtop} construction, the |package| routine comes into action. We might +also have to finish a paragraph that hasn't ended. + +@<Cases of |handle...@>= +case hbox_group: package(0);@+break; +case adjusted_hbox_group: {@+adjust_tail=adjust_head;package(0); + } @+break; +case vbox_group: {@+end_graf();package(0); + } @+break; +case vtop_group: {@+end_graf();package(vtop_code); + } @+break; + +@ @<Declare action...@>= +static void package(small_number @!c) +{@+scaled h; /*height of box*/ +pointer @!p; /*first node in a box*/ +scaled @!d; /*max depth*/ +d=box_max_depth;unsave();save_ptr=save_ptr-3; +if (mode==-hmode) cur_box=hpack(link(head), saved(2), saved(1)); +else{@+cur_box=vpackage(link(head), saved(2), saved(1), d); + if (c==vtop_code) @<Readjust the height and depth of |cur_box|, for \.{\\vtop}@>; + } +pop_nest();box_end(saved(0)); +} + +@ The height of a `\.{\\vtop}' box is inherited from the first item on its list, +if that item is an |hlist_node|, |vlist_node|, or |rule_node|; otherwise +the \.{\\vtop} height is zero. + + +@<Readjust the height...@>= +{@+h=0;p=list_ptr(cur_box); +if (p!=null) if (type(p) <= rule_node) h=height(p); +depth(cur_box)=depth(cur_box)-h+height(cur_box);height(cur_box)=h; +} + +@ A paragraph begins when horizontal-mode material occurs in vertical mode, +or when the paragraph is explicitly started by `\.{\\indent}' or +`\.{\\noindent}'. + +@<Put each...@>= +primitive("indent", start_par, 1); +@!@:indent\_}{\.{\\indent} primitive@> +primitive("noindent", start_par, 0); +@!@:no\_indent\_}{\.{\\noindent} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case start_par: if (chr_code==0) print_esc("noindent");@+else print_esc("indent");@+break; + +@ @<Cases of |main_control| that build...@>= +case vmode+start_par: new_graf(cur_chr > 0);@+break; +case vmode+letter: case vmode+other_char: + case vmode+char_num: case vmode+char_given: + case vmode+math_shift: case vmode+un_hbox: + case vmode+vrule: + case vmode+accent: case vmode+discretionary: + case vmode+hskip: case vmode+valign: + case vmode+ex_space: case vmode+no_boundary: @t@>@;@/ + {@+back_input();new_graf(true); + } @+break; + +@ @<Declare act...@>= +static small_number norm_min(int @!h) +{@+if (h <= 0) return 1;@+else if (h >= 63) return 63;@+ +else return h; +} +@# +static void new_graf(bool @!indented) +{@+prev_graf=0; +if ((mode==vmode)||(head!=tail)) + tail_append(new_param_glue(par_skip_code)); +push_nest();mode=hmode;space_factor=1000;set_cur_lang;clang=cur_lang; +prev_graf=(norm_min(left_hyphen_min)*0100+norm_min(right_hyphen_min)) + *0200000+cur_lang; +if (indented) + {@+tail=new_null_box();link(head)=tail;width(tail)=par_indent;@+ + } +if (every_par!=null) begin_token_list(every_par, every_par_text); +if (nest_ptr==1) build_page(); /*put |par_skip| glue on current page*/ +} + +@ @<Cases of |main_control| that build...@>= +case hmode+start_par: case mmode+start_par: indent_in_hmode();@+break; + +@ @<Declare act...@>= +static void indent_in_hmode(void) +{@+pointer p, @!q; +if (cur_chr > 0) /*\.{\\indent}*/ + {@+p=new_null_box();width(p)=par_indent; + if (abs(mode)==hmode) space_factor=1000; + else{@+q=new_noad();math_type(nucleus(q))=sub_box; + info(nucleus(q))=p;p=q; + } + tail_append(p); + } +} + +@ A paragraph ends when a |par_end| command is sensed, or when we are in +horizontal mode when reaching the right brace of vertical-mode routines +like \.{\\vbox}, \.{\\insert}, or \.{\\output}. + +@<Cases of |main_control| that build...@>= +case vmode+par_end: {@+normal_paragraph(); + if (mode > 0) build_page(); + } @+break; +case hmode+par_end: {@+if (align_state < 0) off_save(); /*this tries to + recover from an alignment that didn't end properly*/ + end_graf(); /*this takes us to the enclosing mode, if |mode > 0|*/ + if (mode==vmode) build_page(); + } @+break; +case hmode+stop: case hmode+vskip: case hmode+hrule: + case hmode+un_vbox: case hmode+halign: head_for_vmode();@+break; + +@ @<Declare act...@>= +static void head_for_vmode(void) +{@+if (mode < 0) + if (cur_cmd!=hrule) off_save(); + else{@+print_err("You can't use `"); + print_esc("hrule");print("' here except with leaders"); +@.You can't use \\hrule...@> + help2("To put a horizontal rule in an hbox or an alignment,",@/ + "you should use \\leaders or \\hrulefill (see The TeXbook)."); + error(); + } +else{@+back_input();cur_tok=par_token;back_input();token_type=inserted; + } +} + +@ @<Declare act...@>= +static void end_graf(void) +{@+if (mode==hmode) + {@+if (head==tail) pop_nest(); /*null paragraphs are ignored*/ + else line_break(widow_penalty); + normal_paragraph(); + error_count=0; + } +} + +@ Insertion and adjustment and mark nodes are constructed by the following +pieces of the program. + +@<Cases of |main_control| that build...@>= +any_mode(insert): case hmode+vadjust: + case mmode+vadjust: begin_insert_or_adjust();@+break; +any_mode(mark): make_mark();@+break; + +@ @<Forbidden...@>= +case vmode+vadjust: + +@ @<Declare act...@>= +static void begin_insert_or_adjust(void) +{@+if (cur_cmd==vadjust) cur_val=255; +else{@+scan_eight_bit_int(); + if (cur_val==255) + {@+print_err("You can't ");print_esc("insert");print_int(255); +@.You can't \\insert255@> + help1("I'm changing to \\insert0; box 255 is special."); + error();cur_val=0; + } + } +saved(0)=cur_val;incr(save_ptr); +new_save_level(insert_group);scan_left_brace();normal_paragraph(); +push_nest();mode=-vmode;prev_depth=ignore_depth; +} + +@ @<Cases of |handle...@>= +case insert_group: {@+end_graf();q=split_top_skip;add_glue_ref(q); + d=split_max_depth;f=floating_penalty;unsave();decr(save_ptr); + /*now |saved(0)| is the insertion number, or 255 for |vadjust|*/ + p=vpack(link(head), natural);pop_nest(); + if (saved(0) < 255) + {@+tail_append(get_node(ins_node_size)); + type(tail)=ins_node;subtype(tail)=qi(saved(0)); + height(tail)=height(p)+depth(p);ins_ptr(tail)=list_ptr(p); + split_top_ptr(tail)=q;depth(tail)=d;float_cost(tail)=f; + } + else{@+tail_append(get_node(small_node_size)); + type(tail)=adjust_node;@/ + subtype(tail)=0; /*the |subtype| is not used*/ + adjust_ptr(tail)=list_ptr(p);delete_glue_ref(q); + } + free_node(p, box_node_size); + if (nest_ptr==0) build_page(); + } @+break; +case output_group: @<Resume the page builder...@>@;@+break; + +@ @<Declare act...@>= +static void make_mark(void) +{@+pointer p; /*new node*/ +halfword @!c; /*the mark class*/ +if (cur_chr==0) c=0; +else{@+scan_register_num();c=cur_val; + } +p=scan_toks(false, true);p=get_node(small_node_size); +mark_class(p)=c; +type(p)=mark_node;subtype(p)=0; /*the |subtype| is not used*/ +mark_ptr(p)=def_ref;link(tail)=p;tail=p; +} + +@ Penalty nodes get into a list via the |break_penalty| command. +@^penalties@> + +@<Cases of |main_control| that build...@>= +any_mode(break_penalty): append_penalty();@+break; + +@ @<Declare action...@>= +static void append_penalty(void) +{@+scan_int();tail_append(new_penalty(cur_val)); +if (mode==vmode) build_page(); +} + +@ The |remove_item| command removes a penalty, kern, or glue node if it +appears at the tail of the current list, using a brute-force linear scan. +Like \.{\\lastbox}, this command is not allowed in vertical mode (except +internal vertical mode), since the current list in vertical mode is sent +to the page builder. But if we happen to be able to implement it in +vertical mode, we do. + +@<Cases of |main_control| that build...@>= +any_mode(remove_item): delete_last();@+break; + +@ When |delete_last| is called, |cur_chr| is the |type| of node that +will be deleted, if present. + +@<Declare action...@>= +static void delete_last(void) +{@+ +pointer @!p, @!q; /*run through the current list*/ +int @!m; /*the length of a replacement list*/ +if ((mode==vmode)&&(tail==head)) + @<Apologize for inability to do the operation now, unless \.{\\unskip} follows +non-glue@>@; +else{@+if (!is_char_node(tail)) if (type(tail)==cur_chr) + {@+q=head; + @/do@+{p=q; + if (!is_char_node(q)) if (type(q)==disc_node) + {@+for (m=1; m<=replace_count(q); m++) p=link(p); + if (p==tail) return; + } + q=link(p); + }@+ while (!(q==tail)); + link(p)=null;flush_node_list(tail);tail=p; + } + } +} + +@ @<Apologize for inability to do the operation...@>= +{@+if ((cur_chr!=glue_node)||(last_glue!=max_halfword)) + {@+you_cant(); + help2("Sorry...I usually can't take things from the current page.",@/ + "Try `I\\vskip-\\lastskip' instead."); + if (cur_chr==kern_node) help_line[0]= + ("Try `I\\kern-\\lastkern' instead."); + else if (cur_chr!=glue_node) help_line[0]=@| + ("Perhaps you can make the output routine do it."); + error(); + } +} + +@ @<Put each...@>= +primitive("unpenalty", remove_item, penalty_node);@/ +@!@:un\_penalty\_}{\.{\\unpenalty} primitive@> +primitive("unkern", remove_item, kern_node);@/ +@!@:un\_kern\_}{\.{\\unkern} primitive@> +primitive("unskip", remove_item, glue_node);@/ +@!@:un\_skip\_}{\.{\\unskip} primitive@> +primitive("unhbox", un_hbox, box_code);@/ +@!@:un\_hbox\_}{\.{\\unhbox} primitive@> +primitive("unhcopy", un_hbox, copy_code);@/ +@!@:un\_hcopy\_}{\.{\\unhcopy} primitive@> +primitive("unvbox", un_vbox, box_code);@/ +@!@:un\_vbox\_}{\.{\\unvbox} primitive@> +primitive("unvcopy", un_vbox, copy_code);@/ +@!@:un\_vcopy\_}{\.{\\unvcopy} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case remove_item: if (chr_code==glue_node) print_esc("unskip"); + else if (chr_code==kern_node) print_esc("unkern"); + else print_esc("unpenalty");@+break; +case un_hbox: if (chr_code==copy_code) print_esc("unhcopy"); + else print_esc("unhbox");@+break; +case un_vbox: if (chr_code==copy_code) print_esc("unvcopy") + @<Cases of |un_vbox| for |print_cmd_chr|@>;@/ + else print_esc("unvbox");@+break; + +@ The |un_hbox| and |un_vbox| commands unwrap one of the 256 current boxes. + +@<Cases of |main_control| that build...@>= +case vmode+un_vbox: case hmode+un_hbox: + case mmode+un_hbox: unpackage();@+break; + +@ @<Declare act...@>= +static void unpackage(void) +{@+ +pointer p; /*the box*/ +int @!c; /*should we copy?*/ +if (cur_chr > copy_code) @<Handle saved items and |goto done|@>; +c=cur_chr;scan_register_num();fetch_box(p); +if (p==null) return; +if ((abs(mode)==mmode)||((abs(mode)==vmode)&&(type(p)!=vlist_node))||@| + ((abs(mode)==hmode)&&(type(p)!=hlist_node))) + {@+print_err("Incompatible list can't be unboxed"); +@.Incompatible list...@> + help3("Sorry, Pandora. (You sneaky devil.)",@/ + "I refuse to unbox an \\hbox in vertical mode or vice versa.",@/ + "And I can't open any boxes in math mode.");@/ + error();return; + } +if (c==copy_code) link(tail)=copy_node_list(list_ptr(p)); +else{@+link(tail)=list_ptr(p);change_box(null); + free_node(p, box_node_size); + } +done: +while (link(tail)!=null) tail=link(tail); +} + +@ @<Forbidden...@>=case vmode+ital_corr: + +@ Italic corrections are converted to kern nodes when the |ital_corr| command +follows a character. In math mode the same effect is achieved by appending +a kern of zero here, since italic corrections are supplied later. + +@<Cases of |main_control| that build...@>= +case hmode+ital_corr: append_italic_correction();@+break; +case mmode+ital_corr: tail_append(new_kern(0))@;@+break; + +@ @<Declare act...@>= +static void append_italic_correction(void) +{@+ +pointer p; /*|char_node| at the tail of the current list*/ +internal_font_number @!f; /*the font in the |char_node|*/ +if (tail!=head) + {@+if (is_char_node(tail)) p=tail; + else if (type(tail)==ligature_node) p=lig_char(tail); + else return; + f=font(p); + tail_append(new_kern(char_italic(f, char_info(f, character(p))))); + subtype(tail)=explicit; + } +} + +@ Discretionary nodes are easy in the common case `\.{\\-}', but in the +general case we must process three braces full of items. + +@<Put each...@>= +primitive("-", discretionary, 1); +@!@:Single-character primitives -}{\quad\.{\\-}@> +primitive("discretionary", discretionary, 0); +@!@:discretionary\_}{\.{\\discretionary} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case discretionary: if (chr_code==1) + print_esc("-");@+else print_esc("discretionary");@+break; + +@ @<Cases of |main_control| that build...@>= +case hmode+discretionary: case mmode+discretionary: append_discretionary();@+break; + +@ The space factor does not change when we append a discretionary node, +but it starts out as 1000 in the subsidiary lists. + +@<Declare act...@>= +static void append_discretionary(void) +{@+int c; /*hyphen character*/ +tail_append(new_disc()); +if (cur_chr==1) + {@+c=hyphen_char[cur_font]; + if (c >= 0) if (c < 256) pre_break(tail)=new_character(cur_font, c); + } +else{@+incr(save_ptr);saved(-1)=0;new_save_level(disc_group); + scan_left_brace();push_nest();mode=-hmode;space_factor=1000; + } +} + +@ The three discretionary lists are constructed somewhat as if they were +hboxes. A~subroutine called |build_discretionary| handles the transitions. +(This is sort of fun.) + +@<Cases of |handle...@>= +case disc_group: build_discretionary();@+break; + +@ @<Declare act...@>= +static void build_discretionary(void) +{@+ +pointer p, @!q; /*for link manipulation*/ +int @!n; /*length of discretionary list*/ +unsave(); +@<Prune the current list, if necessary, until it contains only |char_node|, +|kern_node|, |hlist_node|, |vlist_node|, |rule_node|, and |ligature_node| +items; set |n| to the length of the list, and set |q| to the list's tail@>; +p=link(head);pop_nest(); +switch (saved(-1)) { +case 0: pre_break(tail)=p;@+break; +case 1: post_break(tail)=p;@+break; +case 2: @<Attach list |p| to the current list, and record its length; then +finish up and |return|@>; +} /*there are no other cases*/ +incr(saved(-1));new_save_level(disc_group);scan_left_brace(); +push_nest();mode=-hmode;space_factor=1000; +} + +@ @<Attach list |p| to the current...@>= +{@+if ((n > 0)&&(abs(mode)==mmode)) + {@+print_err("Illegal math ");print_esc("discretionary"); +@.Illegal math \\disc...@> + help2("Sorry: The third part of a discretionary break must be",@/ + "empty, in math formulas. I had to delete your third part."); + flush_node_list(p);n=0;error(); + } +else link(tail)=p; +if (n <= max_quarterword) replace_count(tail)=n; +else{@+print_err("Discretionary list is too long"); +@.Discretionary list is too long@> + help2("Wow---I never thought anybody would tweak me here.",@/ + "You can't seriously need such a huge discretionary list?"); + error(); + } +if (n > 0) tail=q; +decr(save_ptr);return; +} + +@ During this loop, |p==link(q)| and there are |n| items preceding |p|. + +@<Prune the current list, if necessary...@>= +q=head;p=link(q);n=0; +while (p!=null) + {@+if (!is_char_node(p)) if (type(p) > rule_node) + if (type(p)!=kern_node) if (type(p)!=ligature_node) + {@+print_err("Improper discretionary list"); +@.Improper discretionary list@> + help1("Discretionary lists must contain only boxes and kerns.");@/ + error(); + begin_diagnostic(); + print_nl("The following discretionary sublist has been deleted:"); +@.The following...deleted@> + show_box(p); + end_diagnostic(true); + flush_node_list(p);link(q)=null;goto done; + } + q=p;p=link(q);incr(n); + } +done: + +@ We need only one more thing to complete the horizontal mode routines, namely +the \.{\\accent} primitive. + +@<Cases of |main_control| that build...@>= +case hmode+accent: make_accent();@+break; + +@ The positioning of accents is straightforward but tedious. Given an accent +of width |a|, designed for characters of height |x| and slant |s|; +and given a character of width |w|, height |h|, and slant |t|: We will shift +the accent down by |x-h|, and we will insert kern nodes that have the effect of +centering the accent over the character and shifting the accent to the +right by $\delta={1\over2}(w-a)+h\cdot t-x\cdot s$. If either character is +absent from the font, we will simply use the other, without shifting. + +@<Declare act...@>= +static void make_accent(void) +{@+double s, @!t; /*amount of slant*/ +pointer @!p, @!q, @!r; /*character, box, and kern nodes*/ +internal_font_number @!f; /*relevant font*/ +scaled @!a, @!h, @!x, @!w, @!delta; /*heights and widths, as explained above*/ +four_quarters @!i; /*character information*/ +scan_char_num();f=cur_font;p=new_character(f, cur_val); +if (p!=null) + {@+x=x_height(f);s=slant(f)/float_constant(65536); +@^real division@> + a=char_width(f, char_info(f, character(p)));@/ + do_assignments();@/ + @<Create a character node |q| for the next character, but set |q:=null| +if problems arise@>; + if (q!=null) @<Append the accent with appropriate kerns, then set |p:=q|@>; + link(tail)=p;tail=p;space_factor=1000; + } +} + +@ @<Create a character node |q| for the next...@>= +q=null;f=cur_font; +if ((cur_cmd==letter)||(cur_cmd==other_char)||(cur_cmd==char_given)) + q=new_character(f, cur_chr); +else if (cur_cmd==char_num) + {@+scan_char_num();q=new_character(f, cur_val); + } +else back_input() + +@ The kern nodes appended here must be distinguished from other kerns, lest +they be wiped away by the hyphenation algorithm or by a previous line break. + +The two kerns are computed with (machine-dependent) |double| arithmetic, but +their sum is machine-independent; the net effect is machine-independent, +because the user cannot remove these nodes nor access them via \.{\\lastkern}. + +@<Append the accent with appropriate kerns...@>= +{@+t=slant(f)/float_constant(65536); +@^real division@> +i=char_info(f, character(q)); +w=char_width(f, i);h=char_height(f, height_depth(i)); +if (h!=x) /*the accent must be shifted up or down*/ + {@+p=hpack(p, natural);shift_amount(p)=x-h; + } +delta=round((w-a)/float_constant(2)+h*t-x*s); +@^real multiplication@> +@^real addition@> +r=new_kern(delta);subtype(r)=acc_kern;link(tail)=r;link(r)=p; +tail=new_kern(-a-delta);subtype(tail)=acc_kern;link(p)=tail;p=q; +} + +@ When `\.{\\cr}' or `\.{\\span}' or a tab mark comes through the scanner +into |main_control|, it might be that the user has foolishly inserted +one of them into something that has nothing to do with alignment. But it is +far more likely that a left brace or right brace has been omitted, since +|get_next| takes actions appropriate to alignment only when `\.{\\cr}' +or `\.{\\span}' or tab marks occur with |align_state==0|. The following +program attempts to make an appropriate recovery. + +@<Cases of |main_control| that build...@>= +any_mode(car_ret): any_mode(tab_mark): align_error();@+break; +any_mode(no_align): no_align_error();@+break; +any_mode(omit): omit_error();@+break; + +@ @<Declare act...@>= +static void align_error(void) +{@+if (abs(align_state) > 2) + @<Express consternation over the fact that no alignment is in progress@>@; +else{@+back_input(); + if (align_state < 0) + {@+print_err("Missing { inserted"); +@.Missing \{ inserted@> + incr(align_state);cur_tok=left_brace_token+'{'; + } + else{@+print_err("Missing } inserted"); +@.Missing \} inserted@> + decr(align_state);cur_tok=right_brace_token+'}'; + } + help3("I've put in what seems to be necessary to fix",@/ + "the current column of the current alignment.",@/ + "Try to go on, since this might almost work.");ins_error(); + } +} + +@ @<Express consternation...@>= +{@+print_err("Misplaced ");print_cmd_chr(cur_cmd, cur_chr); +@.Misplaced \&@> +@.Misplaced \\span@> +@.Misplaced \\cr@> +if (cur_tok==tab_token+'&') + {@+help6("I can't figure out why you would want to use a tab mark",@/ + "here. If you just want an ampersand, the remedy is",@/ + "simple: Just type `I\\&' now. But if some right brace",@/ + "up above has ended a previous alignment prematurely,",@/ + "you're probably due for more error messages, and you",@/ + "might try typing `S' now just to see what is salvageable."); + } +else{@+help5("I can't figure out why you would want to use a tab mark",@/ + "or \\cr or \\span just now. If something like a right brace",@/ + "up above has ended a previous alignment prematurely,",@/ + "you're probably due for more error messages, and you",@/ + "might try typing `S' now just to see what is salvageable."); + } +error(); +} + +@ The help messages here contain a little white lie, since \.{\\noalign} +and \.{\\omit} are allowed also after `\.{\\noalign\{...\}}'. + +@<Declare act...@>= +static void no_align_error(void) +{@+print_err("Misplaced ");print_esc("noalign"); +@.Misplaced \\noalign@> +help2("I expect to see \\noalign only after the \\cr of",@/ + "an alignment. Proceed, and I'll ignore this case.");error(); +} +static void omit_error(void) +{@+print_err("Misplaced ");print_esc("omit"); +@.Misplaced \\omit@> +help2("I expect to see \\omit only after tab marks or the \\cr of",@/ + "an alignment. Proceed, and I'll ignore this case.");error(); +} + +@ We've now covered most of the abuses of \.{\\halign} and \.{\\valign}. +Let's take a look at what happens when they are used correctly. + +@<Cases of |main_control| that build...@>= +case vmode+halign: case hmode+valign: init_align();@+break; +case mmode+halign: if (privileged()) + if (cur_group==math_shift_group) init_align(); + else off_save();@+break; +case vmode+endv: case hmode+endv: do_endv();@+break; + +@ An |align_group| code is supposed to remain on the |save_stack| +during an entire alignment, until |fin_align| removes it. + +A devious user might force an |endv| command to occur just about anywhere; +we must defeat such hacks. + +@<Declare act...@>= +static void do_endv(void) +{@+base_ptr=input_ptr;input_stack[base_ptr]=cur_input; +while ((input_stack[base_ptr].index_field!=v_template)&& + (input_stack[base_ptr].loc_field==null)&& + (input_stack[base_ptr].state_field==token_list)) decr(base_ptr); +if ((input_stack[base_ptr].index_field!=v_template)|| + (input_stack[base_ptr].loc_field!=null)|| + (input_stack[base_ptr].state_field!=token_list)) + fatal_error("(interwoven alignment preambles are not allowed)"); +@.interwoven alignment preambles...@> + if (cur_group==align_group) + {@+end_graf(); + if (fin_col()) fin_row(); + } +else off_save(); +} + +@ @<Cases of |handle_right_brace|...@>= +case align_group: {@+back_input();cur_tok=cs_token_flag+frozen_cr; + print_err("Missing ");print_esc("cr");print(" inserted"); +@.Missing \\cr inserted@> + help1("I'm guessing that you meant to end an alignment here."); + ins_error(); + } @+break; + +@ @<Cases of |handle_right_brace|...@>= +case no_align_group: {@+end_graf();unsave();align_peek(); + } @+break; + +@ Finally, \.{\\endcsname} is not supposed to get through to |main_control|. + +@<Cases of |main_control| that build...@>= +any_mode(end_cs_name): cs_error();@+break; + +@ @<Declare act...@>= +static void cs_error(void) +{@+print_err("Extra ");print_esc("endcsname"); +@.Extra \\endcsname@> +help1("I'm ignoring this, since I wasn't doing a \\csname."); +error(); +} + +@* Building math lists. +The routines that \TeX\ uses to create mlists are similar to those we have +just seen for the generation of hlists and vlists. But it is necessary to +make ``noads'' as well as nodes, so the reader should review the +discussion of math mode data structures before trying to make sense out of +the following program. + +Here is a little routine that needs to be done whenever a subformula +is about to be processed. The parameter is a code like |math_group|. + +@<Declare act...@>= +static void push_math(group_code @!c) +{@+push_nest();mode=-mmode;incompleat_noad=null;new_save_level(c); +} + +@ We get into math mode from horizontal mode when a `\.\$' (i.e., a +|math_shift| character) is scanned. We must check to see whether this +`\.\$' is immediately followed by another, in case display math mode is +called for. + +@<Cases of |main_control| that build...@>= +case hmode+math_shift: init_math();@+break; + +@ @<Declare act...@>= +static void init_math(void) +{@+ +scaled w; /*new or partial |pre_display_size|*/ +scaled @!l; /*new |display_width|*/ +scaled @!s; /*new |display_indent|*/ +pointer @!p; /*current node when calculating |pre_display_size|*/ +pointer @!q; /*glue specification when calculating |pre_display_size|*/ +internal_font_number @!f; /*font in current |char_node|*/ +int @!n; /*scope of paragraph shape specification*/ +scaled @!v; /*|w| plus possible glue amount*/ +scaled @!d; /*increment to |v|*/ +get_token(); /*|get_x_token| would fail on \.{\\ifmmode}\thinspace!*/ +if ((cur_cmd==math_shift)&&(mode > 0)) @<Go into display math mode@>@; +else{@+back_input();@<Go into ordinary math mode@>; + } +} + +@ @<Go into ordinary math mode@>= +{@+push_math(math_shift_group);eq_word_define(int_base+cur_fam_code,-1); +if (every_math!=null) begin_token_list(every_math, every_math_text); +} + +@ We get into ordinary math mode from display math mode when `\.{\\eqno}' or +`\.{\\leqno}' appears. In such cases |cur_chr| will be 0 or~1, respectively; +the value of |cur_chr| is placed onto |save_stack| for safe keeping. + +@<Cases of |main_control| that build...@>= +case mmode+eq_no: if (privileged()) + if (cur_group==math_shift_group) start_eq_no(); + else off_save();@+break; + +@ @<Put each...@>= +primitive("eqno", eq_no, 0); +@!@:eq\_no\_}{\.{\\eqno} primitive@> +primitive("leqno", eq_no, 1); +@!@:leq\_no\_}{\.{\\leqno} primitive@> + +@ When \TeX\ is in display math mode, |cur_group==math_shift_group|, +so it is not necessary for the |start_eq_no| procedure to test for +this condition. + +@<Declare act...@>= +static void start_eq_no(void) +{@+saved(0)=cur_chr;incr(save_ptr); +@<Go into ordinary math mode@>; +} + +@ @<Cases of |print_cmd_chr|...@>= +case eq_no: if (chr_code==1) print_esc("leqno");@+else print_esc("eqno");@+break; + +@ @<Forbidden...@>=non_math(eq_no): + +@ When we enter display math mode, we need to call |line_break| to +process the partial paragraph that has just been interrupted by the +display. Then we can set the proper values of |display_width| and +|display_indent| and |pre_display_size|. + +@<Go into display math mode@>= +{@+if (head==tail) /*`\.{\\noindent\$\$}' or `\.{\$\${ }\$\$}'*/ + {@+pop_nest();w=-max_dimen; + } +else{@+line_break(display_widow_penalty);@/ + @<Calculate the natural width, |w|, by which the characters of the final +line extend to the right of the reference point, plus two ems; or set |w:=max_dimen| +if the non-blank information on that line is affected by stretching or shrinking@>; + } + /*now we are in vertical mode, working on the list that will contain the display*/ +@<Calculate the length, |l|, and the shift amount, |s|, of the display lines@>; +push_math(math_shift_group);mode=mmode; +eq_word_define(int_base+cur_fam_code,-1);@/ +eq_word_define(dimen_base+pre_display_size_code, w); +eq_word_define(dimen_base+display_width_code, l); +eq_word_define(dimen_base+display_indent_code, s); +if (every_display!=null) begin_token_list(every_display, every_display_text); +if (nest_ptr==1) build_page(); +} + +@ @<Calculate the natural width, |w|, by which...@>= +v=shift_amount(just_box)+2*quad(cur_font);w=-max_dimen; +p=list_ptr(just_box); +while (p!=null) + {@+@<Let |d| be the natural width of node |p|; if the node is ``visible,'' +|goto found|; if the node is glue that stretches or shrinks, set |v:=max_dimen|@>; + if (v < max_dimen) v=v+d; + goto not_found; + found: if (v < max_dimen) + {@+v=v+d;w=v; + } + else{@+w=max_dimen;goto done; + } + not_found: p=link(p); + } +done: + +@ @<Let |d| be the natural width of node |p|...@>= +reswitch: if (is_char_node(p)) + {@+f=font(p);d=char_width(f, char_info(f, character(p))); + goto found; + } +switch (type(p)) { +case hlist_node: case vlist_node: case rule_node: {@+d=width(p);goto found; + } +case ligature_node: @<Make node |p| look like a |char_node|...@>@; +case kern_node: case math_node: d=width(p);@+break; +case glue_node: @<Let |d| be the natural width of this glue; if stretching +or shrinking, set |v:=max_dimen|; |goto found| in the case of leaders@>@;@+break; +case whatsit_node: @<Let |d| be the width of the whatsit |p|@>;@+break; +default:d=0; +} + +@ We need to be careful that |w|, |v|, and |d| do not depend on any |glue_set| +values, since such values are subject to system-dependent rounding. +System-dependent numbers are not allowed to infiltrate parameters like +|pre_display_size|, since \TeX82 is supposed to make the same decisions on all +machines. + +@<Let |d| be the natural width of this glue...@>= +{@+q=glue_ptr(p);d=width(q); +if (glue_sign(just_box)==stretching) + {@+if ((glue_order(just_box)==stretch_order(q))&&@| + (stretch(q)!=0)) + v=max_dimen; + } +else if (glue_sign(just_box)==shrinking) + {@+if ((glue_order(just_box)==shrink_order(q))&&@| + (shrink(q)!=0)) + v=max_dimen; + } +if (subtype(p) >= a_leaders) goto found; +} + +@ A displayed equation is considered to be three lines long, so we +calculate the length and offset of line number |prev_graf+2|. + +@<Calculate the length, |l|,...@>= +if (par_shape_ptr==null) + if ((hang_indent!=0)&&@| + (((hang_after >= 0)&&(prev_graf+2 > hang_after))||@| + (prev_graf+1 < -hang_after))) + {@+l=hsize-abs(hang_indent); + if (hang_indent > 0) s=hang_indent;@+else s=0; + } + else{@+l=hsize;s=0; + } +else{@+n=info(par_shape_ptr); + if (prev_graf+2 >= n) p=par_shape_ptr+2*n; + else p=par_shape_ptr+2*(prev_graf+2); + s=mem[p-1].sc;l=mem[p].sc; + } + +@ Subformulas of math formulas cause a new level of math mode to be entered, +on the semantic nest as well as the save stack. These subformulas arise in +several ways: (1)~A left brace by itself indicates the beginning of a +subformula that will be put into a box, thereby freezing its glue and +preventing line breaks. (2)~A subscript or superscript is treated as a +subformula if it is not a single character; the same applies to +the nucleus of things like \.{\\underline}. (3)~The \.{\\left} primitive +initiates a subformula that will be terminated by a matching \.{\\right}. +The group codes placed on |save_stack| in these three cases are +|math_group|, |math_group|, and |math_left_group|, respectively. + +Here is the code that handles case (1); the other cases are not quite as +trivial, so we shall consider them later. + +@<Cases of |main_control| that build...@>= +case mmode+left_brace: {@+tail_append(new_noad()); + back_input();scan_math(nucleus(tail)); + } @+break; + +@ Recall that the |nucleus|, |subscr|, and |supscr| fields in a noad are +broken down into subfields called |math_type| and either |info| or +|(fam, character)|. The job of |scan_math| is to figure out what to place +in one of these principal fields; it looks at the subformula that +comes next in the input, and places an encoding of that subformula +into a given word of |mem|. + +@d fam_in_range ((cur_fam >= 0)&&(cur_fam < 16)) + +@<Declare act...@>= +static void scan_math(pointer @!p) +{@+ +int c; /*math character code*/ +restart: @<Get the next non-blank non-relax...@>; +reswitch: switch (cur_cmd) { +case letter: case other_char: case char_given: {@+c=ho(math_code(cur_chr)); + if (c==0100000) + {@+@<Treat |cur_chr| as an active character@>; + goto restart; + } + } @+break; +case char_num: {@+scan_char_num();cur_chr=cur_val;cur_cmd=char_given; + goto reswitch; + } +case math_char_num: {@+scan_fifteen_bit_int();c=cur_val; + } @+break; +case math_given: c=cur_chr;@+break; +case delim_num: {@+scan_twenty_seven_bit_int();c=cur_val/010000; + } @+break; +default:@<Scan a subformula enclosed in braces and |return|@>@; +} @/ +math_type(p)=math_char;character(p)=qi(c%256); +if ((c >= var_code)&&fam_in_range) fam(p)=cur_fam; +else fam(p)=(c/256)%16; +} + +@ An active character that is an |outer_call| is allowed here. + +@<Treat |cur_chr|...@>= +{@+cur_cs=cur_chr+active_base; +cur_cmd=eq_type(cur_cs);cur_chr=equiv(cur_cs); +x_token();back_input(); +} + +@ The pointer |p| is placed on |save_stack| while a complex subformula +is being scanned. + +@<Scan a subformula...@>= +{@+back_input();scan_left_brace();@/ +saved(0)=p;incr(save_ptr);push_math(math_group);return; +} + +@ The simplest math formula is, of course, `\.{\${ }\$}', when no noads are +generated. The next simplest cases involve a single character, e.g., +`\.{\$x\$}'. Even though such cases may not seem to be very interesting, +the reader can perhaps understand how happy the author was when `\.{\$x\$}' +was first properly typeset by \TeX. The code in this section was used. +@^Knuth, Donald Ervin@> + +@<Cases of |main_control| that build...@>= +case mmode+letter: case mmode+other_char: + case mmode+char_given: + set_math_char(ho(math_code(cur_chr)));@+break; +case mmode+char_num: {@+scan_char_num();cur_chr=cur_val; + set_math_char(ho(math_code(cur_chr))); + } @+break; +case mmode+math_char_num: {@+scan_fifteen_bit_int();set_math_char(cur_val); + } @+break; +case mmode+math_given: set_math_char(cur_chr);@+break; +case mmode+delim_num: {@+scan_twenty_seven_bit_int(); + set_math_char(cur_val/010000); + } @+break; + +@ The |set_math_char| procedure creates a new noad appropriate to a given +math code, and appends it to the current mlist. However, if the math code +is sufficiently large, the |cur_chr| is treated as an active character and +nothing is appended. + +@<Declare act...@>= +static void set_math_char(int @!c) +{@+pointer p; /*the new noad*/ +if (c >= 0100000) + @<Treat |cur_chr|...@>@; +else{@+p=new_noad();math_type(nucleus(p))=math_char; + character(nucleus(p))=qi(c%256); + fam(nucleus(p))=(c/256)%16; + if (c >= var_code) + {@+if (fam_in_range) fam(nucleus(p))=cur_fam; + type(p)=ord_noad; + } + else type(p)=ord_noad+(c/010000); + link(tail)=p;tail=p; + } +} + +@ Primitive math operators like \.{\\mathop} and \.{\\underline} are given +the command code |math_comp|, supplemented by the noad type that they +generate. + +@<Put each...@>= +primitive("mathord", math_comp, ord_noad); +@!@:math\_ord\_}{\.{\\mathord} primitive@> +primitive("mathop", math_comp, op_noad); +@!@:math\_op\_}{\.{\\mathop} primitive@> +primitive("mathbin", math_comp, bin_noad); +@!@:math\_bin\_}{\.{\\mathbin} primitive@> +primitive("mathrel", math_comp, rel_noad); +@!@:math\_rel\_}{\.{\\mathrel} primitive@> +primitive("mathopen", math_comp, open_noad); +@!@:math\_open\_}{\.{\\mathopen} primitive@> +primitive("mathclose", math_comp, close_noad); +@!@:math\_close\_}{\.{\\mathclose} primitive@> +primitive("mathpunct", math_comp, punct_noad); +@!@:math\_punct\_}{\.{\\mathpunct} primitive@> +primitive("mathinner", math_comp, inner_noad); +@!@:math\_inner\_}{\.{\\mathinner} primitive@> +primitive("underline", math_comp, under_noad); +@!@:underline\_}{\.{\\underline} primitive@> +primitive("overline", math_comp, over_noad);@/ +@!@:overline\_}{\.{\\overline} primitive@> +primitive("displaylimits", limit_switch, normal); +@!@:display\_limits\_}{\.{\\displaylimits} primitive@> +primitive("limits", limit_switch, limits); +@!@:limits\_}{\.{\\limits} primitive@> +primitive("nolimits", limit_switch, no_limits); +@!@:no\_limits\_}{\.{\\nolimits} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case math_comp: switch (chr_code) { + case ord_noad: print_esc("mathord");@+break; + case op_noad: print_esc("mathop");@+break; + case bin_noad: print_esc("mathbin");@+break; + case rel_noad: print_esc("mathrel");@+break; + case open_noad: print_esc("mathopen");@+break; + case close_noad: print_esc("mathclose");@+break; + case punct_noad: print_esc("mathpunct");@+break; + case inner_noad: print_esc("mathinner");@+break; + case under_noad: print_esc("underline");@+break; + default:print_esc("overline"); + } @+break; +case limit_switch: if (chr_code==limits) print_esc("limits"); + else if (chr_code==no_limits) print_esc("nolimits"); + else print_esc("displaylimits");@+break; + +@ @<Cases of |main_control| that build...@>= +case mmode+math_comp: {@+tail_append(new_noad()); + type(tail)=cur_chr;scan_math(nucleus(tail)); + } @+break; +case mmode+limit_switch: math_limit_switch();@+break; + +@ @<Declare act...@>= +static void math_limit_switch(void) +{@+ +if (head!=tail) if (type(tail)==op_noad) + {@+subtype(tail)=cur_chr;return; + } +print_err("Limit controls must follow a math operator"); +@.Limit controls must follow...@> +help1("I'm ignoring this misplaced \\limits or \\nolimits command.");error(); +} + +@ Delimiter fields of noads are filled in by the |scan_delimiter| routine. +The first parameter of this procedure is the |mem| address where the +delimiter is to be placed; the second tells if this delimiter follows +\.{\\radical} or not. + +@<Declare act...@>= +static void scan_delimiter(pointer @!p, bool @!r) +{@+if (r) scan_twenty_seven_bit_int(); +else{@+@<Get the next non-blank non-relax...@>; + switch (cur_cmd) { + case letter: case other_char: cur_val=del_code(cur_chr);@+break; + case delim_num: scan_twenty_seven_bit_int();@+break; + default:cur_val=-1; + } + } +if (cur_val < 0) @<Report that an invalid delimiter code is being changed +to null; set~|cur_val:=0|@>; +small_fam(p)=(cur_val/04000000)%16; +small_char(p)=qi((cur_val/010000)%256); +large_fam(p)=(cur_val/256)%16; +large_char(p)=qi(cur_val%256); +} + +@ @<Report that an invalid delimiter...@>= +{@+print_err("Missing delimiter (. inserted)"); +@.Missing delimiter...@> +help6("I was expecting to see something like `(' or `\\{' or",@/ + "`\\}' here. If you typed, e.g., `{' instead of `\\{', you",@/ + "should probably delete the `{' by typing `1' now, so that",@/ + "braces don't get unbalanced. Otherwise just proceed.",@/ + "Acceptable delimiters are characters whose \\delcode is",@/ + "nonnegative, or you can use `\\delimiter <delimiter code>'."); +back_error();cur_val=0; +} + +@ @<Cases of |main_control| that build...@>= +case mmode+radical: math_radical();@+break; + +@ @<Declare act...@>= +static void math_radical(void) +{@+tail_append(get_node(radical_noad_size)); +type(tail)=radical_noad;subtype(tail)=normal; +mem[nucleus(tail)].hh=empty_field; +mem[subscr(tail)].hh=empty_field; +mem[supscr(tail)].hh=empty_field; +scan_delimiter(left_delimiter(tail), true);scan_math(nucleus(tail)); +} + +@ @<Cases of |main_control| that build...@>= +case mmode+accent: case mmode+math_accent: math_ac();@+break; + +@ @<Declare act...@>= +static void math_ac(void) +{@+if (cur_cmd==accent) + @<Complain that the user should have said \.{\\mathaccent}@>; +tail_append(get_node(accent_noad_size)); +type(tail)=accent_noad;subtype(tail)=normal; +mem[nucleus(tail)].hh=empty_field; +mem[subscr(tail)].hh=empty_field; +mem[supscr(tail)].hh=empty_field; +math_type(accent_chr(tail))=math_char; +scan_fifteen_bit_int(); +character(accent_chr(tail))=qi(cur_val%256); +if ((cur_val >= var_code)&&fam_in_range) fam(accent_chr(tail))=cur_fam; +else fam(accent_chr(tail))=(cur_val/256)%16; +scan_math(nucleus(tail)); +} + +@ @<Complain that the user should have said \.{\\mathaccent}@>= +{@+print_err("Please use ");print_esc("mathaccent"); +print(" for accents in math mode"); +@.Please use \\mathaccent...@> +help2("I'm changing \\accent to \\mathaccent here; wish me luck.",@/ + "(Accents are not the same in formulas as they are in text.)"); +error(); +} + +@ @<Cases of |main_control| that build...@>= +case mmode+vcenter: {@+scan_spec(vcenter_group, false);normal_paragraph(); + push_nest();mode=-vmode;prev_depth=ignore_depth; + if (every_vbox!=null) begin_token_list(every_vbox, every_vbox_text); + } @+break; + +@ @<Cases of |handle...@>= +case vcenter_group: {@+end_graf();unsave();save_ptr=save_ptr-2; + p=vpack(link(head), saved(1), saved(0));pop_nest(); + tail_append(new_noad());type(tail)=vcenter_noad; + math_type(nucleus(tail))=sub_box;info(nucleus(tail))=p; + } @+break; + +@ The routine that inserts a |style_node| holds no surprises. + +@<Put each...@>= +primitive("displaystyle", math_style, display_style); +@!@:display\_style\_}{\.{\\displaystyle} primitive@> +primitive("textstyle", math_style, text_style); +@!@:text\_style\_}{\.{\\textstyle} primitive@> +primitive("scriptstyle", math_style, script_style); +@!@:script\_style\_}{\.{\\scriptstyle} primitive@> +primitive("scriptscriptstyle", math_style, script_script_style); +@!@:script\_script\_style\_}{\.{\\scriptscriptstyle} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case math_style: print_style(chr_code);@+break; + +@ @<Cases of |main_control| that build...@>= +case mmode+math_style: tail_append(new_style(cur_chr))@;@+break; +case mmode+non_script: {@+tail_append(new_glue(zero_glue)); + subtype(tail)=cond_math_glue; + } @+break; +case mmode+math_choice: append_choices();@+break; + +@ The routine that scans the four mlists of a \.{\\mathchoice} is very +much like the routine that builds discretionary nodes. + +@<Declare act...@>= +static void append_choices(void) +{@+tail_append(new_choice());incr(save_ptr);saved(-1)=0; +push_math(math_choice_group);scan_left_brace(); +} + +@ @<Cases of |handle_right_brace|...@>= +case math_choice_group: build_choices();@+break; + +@ @<Declare act...@>= +@t\4@>@<Declare the function called |fin_mlist|@>@t@>@;@/ +static void build_choices(void) +{@+ +pointer p; /*the current mlist*/ +unsave();p=fin_mlist(null); +switch (saved(-1)) { +case 0: display_mlist(tail)=p;@+break; +case 1: text_mlist(tail)=p;@+break; +case 2: script_mlist(tail)=p;@+break; +case 3: {@+script_script_mlist(tail)=p;decr(save_ptr);return; + } +} /*there are no other cases*/ +incr(saved(-1));push_math(math_choice_group);scan_left_brace(); +} + +@ Subscripts and superscripts are attached to the previous nucleus by the +@^superscripts@>@^subscripts@> +action procedure called |sub_sup|. We use the facts that |sub_mark==sup_mark+1| +and |subscr(p)==supscr(p)+1|. + +@<Cases of |main_control| that build...@>= +case mmode+sub_mark: case mmode+sup_mark: sub_sup();@+break; + +@ @<Declare act...@>= +static void sub_sup(void) +{@+small_number t; /*type of previous sub/superscript*/ +pointer @!p; /*field to be filled by |scan_math|*/ +t=empty;p=null; +if (tail!=head) if (scripts_allowed(tail)) + {@+p=supscr(tail)+cur_cmd-sup_mark; /*|supscr| or |subscr|*/ + t=math_type(p); + } +if ((p==null)||(t!=empty)) @<Insert a dummy noad to be sub/superscripted@>; +scan_math(p); +} + +@ @<Insert a dummy...@>= +{@+tail_append(new_noad()); +p=supscr(tail)+cur_cmd-sup_mark; /*|supscr| or |subscr|*/ +if (t!=empty) + {@+if (cur_cmd==sup_mark) + {@+print_err("Double superscript"); +@.Double superscript@> + help1("I treat `x^1^2' essentially like `x^1{}^2'."); + } + else{@+print_err("Double subscript"); +@.Double subscript@> + help1("I treat `x_1_2' essentially like `x_1{}_2'."); + } + error(); + } +} + +@ An operation like `\.{\\over}' causes the current mlist to go into a +state of suspended animation: |incompleat_noad| points to a |fraction_noad| +that contains the mlist-so-far as its numerator, while the denominator +is yet to come. Finally when the mlist is finished, the denominator will +go into the incompleat fraction noad, and that noad will become the +whole formula, unless it is surrounded by `\.{\\left}' and `\.{\\right}' +delimiters. + +@d above_code 0 /* `\.{\\above}' */ +@d over_code 1 /* `\.{\\over}' */ +@d atop_code 2 /* `\.{\\atop}' */ +@d delimited_code 3 /* `\.{\\abovewithdelims}', etc.*/ + +@<Put each...@>= +primitive("above", above, above_code);@/ +@!@:above\_}{\.{\\above} primitive@> +primitive("over", above, over_code);@/ +@!@:over\_}{\.{\\over} primitive@> +primitive("atop", above, atop_code);@/ +@!@:atop\_}{\.{\\atop} primitive@> +primitive("abovewithdelims", above, delimited_code+above_code);@/ +@!@:above\_with\_delims\_}{\.{\\abovewithdelims} primitive@> +primitive("overwithdelims", above, delimited_code+over_code);@/ +@!@:over\_with\_delims\_}{\.{\\overwithdelims} primitive@> +primitive("atopwithdelims", above, delimited_code+atop_code); +@!@:atop\_with\_delims\_}{\.{\\atopwithdelims} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case above: switch (chr_code) { + case over_code: print_esc("over");@+break; + case atop_code: print_esc("atop");@+break; + case delimited_code+above_code: print_esc("abovewithdelims");@+break; + case delimited_code+over_code: print_esc("overwithdelims");@+break; + case delimited_code+atop_code: print_esc("atopwithdelims");@+break; + default:print_esc("above"); + } @+break; + +@ @<Cases of |main_control| that build...@>= +case mmode+above: math_fraction();@+break; + +@ @<Declare act...@>= +static void math_fraction(void) +{@+small_number c; /*the type of generalized fraction we are scanning*/ +c=cur_chr; +if (incompleat_noad!=null) + @<Ignore the fraction operation and complain about this ambiguous case@>@; +else{@+incompleat_noad=get_node(fraction_noad_size); + type(incompleat_noad)=fraction_noad; + subtype(incompleat_noad)=normal; + math_type(numerator(incompleat_noad))=sub_mlist; + info(numerator(incompleat_noad))=link(head); + mem[denominator(incompleat_noad)].hh=empty_field; + mem[left_delimiter(incompleat_noad)].qqqq=null_delimiter; + mem[right_delimiter(incompleat_noad)].qqqq=null_delimiter;@/ + link(head)=null;tail=head; + @<Use code |c| to distinguish between generalized fractions@>; + } +} + +@ @<Use code |c|...@>= +if (c >= delimited_code) + {@+scan_delimiter(left_delimiter(incompleat_noad), false); + scan_delimiter(right_delimiter(incompleat_noad), false); + } +switch (c%delimited_code) { +case above_code: {@+scan_normal_dimen; + thickness(incompleat_noad)=cur_val; + } @+break; +case over_code: thickness(incompleat_noad)=default_code;@+break; +case atop_code: thickness(incompleat_noad)=0; +} /*there are no other cases*/ + +@ @<Ignore the fraction...@>= +{@+if (c >= delimited_code) + {@+scan_delimiter(garbage, false);scan_delimiter(garbage, false); + } +if (c%delimited_code==above_code) scan_normal_dimen; +print_err("Ambiguous; you need another { and }"); +@.Ambiguous...@> +help3("I'm ignoring this fraction specification, since I don't",@/ + "know whether a construction like `x \\over y \\over z'",@/ + "means `{x \\over y} \\over z' or `x \\over {y \\over z}'."); +error(); +} + +@ At the end of a math formula or subformula, the |fin_mlist| routine is +called upon to return a pointer to the newly completed mlist, and to +pop the nest back to the enclosing semantic level. The parameter to +|fin_mlist|, if not null, points to a |right_noad| that ends the +current mlist; this |right_noad| has not yet been appended. + +@<Declare the function called |fin_mlist|@>= +static pointer fin_mlist(pointer @!p) +{@+pointer q; /*the mlist to return*/ +if (incompleat_noad!=null) @<Compleat the incompleat noad@>@; +else{@+link(tail)=p;q=link(head); + } +pop_nest();return q; +} + +@ @<Compleat...@>= +{@+math_type(denominator(incompleat_noad))=sub_mlist; +info(denominator(incompleat_noad))=link(head); +if (p==null) q=incompleat_noad; +else{@+q=info(numerator(incompleat_noad)); + if ((type(q)!=left_noad)||(delim_ptr==null)) confusion("right"); +@:this can't happen right}{\quad right@> + info(numerator(incompleat_noad))=link(delim_ptr); + link(delim_ptr)=incompleat_noad;link(incompleat_noad)=p; + } +} + +@ Now at last we're ready to see what happens when a right brace occurs +in a math formula. Two special cases are simplified here: Braces are effectively +removed when they surround a single Ord without sub/superscripts, or when they +surround an accent that is the nucleus of an Ord atom. + +@<Cases of |handle...@>= +case math_group: {@+unsave();decr(save_ptr);@/ + math_type(saved(0))=sub_mlist;p=fin_mlist(null);info(saved(0))=p; + if (p!=null) if (link(p)==null) + if (type(p)==ord_noad) + {@+if (math_type(subscr(p))==empty) + if (math_type(supscr(p))==empty) + {@+mem[saved(0)].hh=mem[nucleus(p)].hh; + free_node(p, noad_size); + } + } + else if (type(p)==accent_noad) if (saved(0)==nucleus(tail)) + if (type(tail)==ord_noad) @<Replace the tail of the list by |p|@>; + } @+break; + +@ @<Replace the tail...@>= +{@+q=head;while (link(q)!=tail) q=link(q); +link(q)=p;free_node(tail, noad_size);tail=p; +} + +@ We have dealt with all constructions of math mode except `\.{\\left}' and +`\.{\\right}', so the picture is completed by the following sections of +the program. + +@<Put each...@>= +primitive("left", left_right, left_noad); +@!@:left\_}{\.{\\left} primitive@> +primitive("right", left_right, right_noad); +@!@:right\_}{\.{\\right} primitive@> +text(frozen_right)=text(cur_val);eqtb[frozen_right]=eqtb[cur_val]; + +@ @<Cases of |print_cmd_chr|...@>= +case left_right: if (chr_code==left_noad) print_esc("left") +@/@<Cases of |left_right| for |print_cmd_chr|@>;@/ +else print_esc("right");@+break; + +@ @<Cases of |main_control| that build...@>= +case mmode+left_right: math_left_right();@+break; + +@ @<Declare act...@>= +static void math_left_right(void) +{@+small_number t; /*|left_noad| or |right_noad|*/ +pointer @!p; /*new noad*/ +pointer @!q; /*resulting mlist*/ +t=cur_chr; +if ((t!=left_noad)&&(cur_group!=math_left_group)) + @<Try to recover from mismatched \.{\\right}@>@; +else{@+p=new_noad();type(p)=t; + scan_delimiter(delimiter(p), false); + if (t==middle_noad) + {@+type(p)=right_noad;subtype(p)=middle_noad; + } + if (t==left_noad) q=p; + else{@+q=fin_mlist(p);unsave(); /*end of |math_left_group|*/ + } + if (t!=right_noad) + {@+push_math(math_left_group);link(head)=q;tail=p; + delim_ptr=p; + } + else{@+ + tail_append(new_noad());type(tail)=inner_noad; + math_type(nucleus(tail))=sub_mlist; + info(nucleus(tail))=q; + } + } +} + +@ @<Try to recover from mismatch...@>= +{@+if (cur_group==math_shift_group) + {@+scan_delimiter(garbage, false); + print_err("Extra "); + if (t==middle_noad) + {@+print_esc("middle"); +@.Extra \\middle.@> + help1("I'm ignoring a \\middle that had no matching \\left."); + } + else{@+print_esc("right"); +@.Extra \\right.@> + help1("I'm ignoring a \\right that had no matching \\left."); + } + error(); + } +else off_save(); +} + +@ Here is the only way out of math mode. + +@<Cases of |main_control| that build...@>= +case mmode+math_shift: if (cur_group==math_shift_group) after_math(); + else off_save();@+break; + +@ @<Declare act...@>= +static void after_math(void) +{@+bool l; /*`\.{\\leqno}' instead of `\.{\\eqno}'*/ +bool @!danger; /*not enough symbol fonts are present*/ +int @!m; /*|mmode| or |-mmode|*/ +pointer @!p; /*the formula*/ +pointer @!a; /*box containing equation number*/ +@<Local variables for finishing a displayed formula@>@; +danger=false; +@<Check that the necessary fonts for math symbols are present; if not, flush +the current math lists and set |danger:=true|@>; +m=mode;l=false;p=fin_mlist(null); /*this pops the nest*/ +if (mode==-m) /*end of equation number*/ + {@+@<Check that another \.\$ follows@>; + cur_mlist=p;cur_style=text_style;mlist_penalties=false; + mlist_to_hlist();a=hpack(link(temp_head), natural); + unsave();decr(save_ptr); /*now |cur_group==math_shift_group|*/ + if (saved(0)==1) l=true; + danger=false; + @<Check that the necessary fonts for math symbols are present; if not, flush +the current math lists and set |danger:=true|@>; + m=mode;p=fin_mlist(null); + } +else a=null; +if (m < 0) @<Finish math in text@>@; +else{@+if (a==null) @<Check that another \.\$ follows@>; + @<Finish displayed math@>; + } +} + +@ @<Check that the necessary fonts...@>= +if ((font_params[fam_fnt(2+text_size)] < total_mathsy_params)||@| + (font_params[fam_fnt(2+script_size)] < total_mathsy_params)||@| + (font_params[fam_fnt(2+script_script_size)] < total_mathsy_params)) + {@+print_err("Math formula deleted: Insufficient symbol fonts");@/ +@.Math formula deleted...@> + help3("Sorry, but I can't typeset math unless \\textfont 2",@/ + "and \\scriptfont 2 and \\scriptscriptfont 2 have all",@/ + "the \\fontdimen values needed in math symbol fonts."); + error();flush_math();danger=true; + } +else if ((font_params[fam_fnt(3+text_size)] < total_mathex_params)||@| + (font_params[fam_fnt(3+script_size)] < total_mathex_params)||@| + (font_params[fam_fnt(3+script_script_size)] < total_mathex_params)) + {@+print_err("Math formula deleted: Insufficient extension fonts");@/ + help3("Sorry, but I can't typeset math unless \\textfont 3",@/ + "and \\scriptfont 3 and \\scriptscriptfont 3 have all",@/ + "the \\fontdimen values needed in math extension fonts."); + error();flush_math();danger=true; + } + +@ The |unsave| is done after everything else here; hence an appearance of +`\.{\\mathsurround}' inside of `\.{\$...\$}' affects the spacing at these +particular \.\$'s. This is consistent with the conventions of +`\.{\$\$...\$\$}', since `\.{\\abovedisplayskip}' inside a display affects the +space above that display. + +@<Finish math in text@>= +{@+tail_append(new_math(math_surround, before)); +cur_mlist=p;cur_style=text_style;mlist_penalties=(mode > 0);mlist_to_hlist(); +link(tail)=link(temp_head); +while (link(tail)!=null) tail=link(tail); +tail_append(new_math(math_surround, after)); +space_factor=1000;unsave(); +} + +@ \TeX\ gets to the following part of the program when the first `\.\$' ending +a display has been scanned. + +@<Check that another \.\$ follows@>= +{@+get_x_token(); +if (cur_cmd!=math_shift) + {@+print_err("Display math should end with $$"); +@.Display math...with \$\$@> + help2("The `$' that I just saw supposedly matches a previous `$$'.",@/ + "So I shall assume that you typed `$$' both times."); + back_error(); + } +} + +@ We have saved the worst for last: The fussiest part of math mode processing +occurs when a displayed formula is being centered and placed with an optional +equation number. + +@<Local variables for finishing...@>= +pointer @!b; /*box containing the equation*/ +scaled @!w; /*width of the equation*/ +scaled @!z; /*width of the line*/ +scaled @!e; /*width of equation number*/ +scaled @!q; /*width of equation number plus space to separate from equation*/ +scaled @!d; /*displacement of equation in the line*/ +scaled @!s; /*move the line right this much*/ +small_number @!g1, @!g2; /*glue parameter codes for before and after*/ +pointer @!r; /*kern node used to position the display*/ +pointer @!t; /*tail of adjustment list*/ + +@ At this time |p| points to the mlist for the formula; |a| is either +|null| or it points to a box containing the equation number; and we are in +vertical mode (or internal vertical mode). + +@<Finish displayed math@>= +cur_mlist=p;cur_style=display_style;mlist_penalties=false; +mlist_to_hlist();p=link(temp_head);@/ +adjust_tail=adjust_head;b=hpack(p, natural);p=list_ptr(b); +t=adjust_tail;adjust_tail=null;@/ +w=width(b);z=display_width;s=display_indent; +if ((a==null)||danger) + {@+e=0;q=0; + } +else{@+e=width(a);q=e+math_quad(text_size); + } +if (w+q > z) + @<Squeeze the equation as much as possible; if there is an equation number +that should go on a separate line by itself, set~|e:=0|@>; +@<Determine the displacement, |d|, of the left edge of the equation, with +respect to the line size |z|, assuming that |l=false|@>; +@<Append the glue or equation number preceding the display@>; +@<Append the display and perhaps also the equation number@>; +@<Append the glue or equation number following the display@>; +resume_after_display() + +@ @<Declare act...@>= +static void resume_after_display(void) +{@+if (cur_group!=math_shift_group) confusion("display"); +@:this can't happen display}{\quad display@> +unsave();prev_graf=prev_graf+3; +push_nest();mode=hmode;space_factor=1000;set_cur_lang;clang=cur_lang; +prev_graf=(norm_min(left_hyphen_min)*0100+norm_min(right_hyphen_min)) + *0200000+cur_lang; +@<Scan an optional space@>; +if (nest_ptr==1) build_page(); +} + +@ The user can force the equation number to go on a separate line +by causing its width to be zero. + +@<Squeeze the equation as much as possible...@>= +{@+if ((e!=0)&&((w-total_shrink[normal]+q <= z)||@| + (total_shrink[fil]!=0)||(total_shrink[fill]!=0)|| + (total_shrink[filll]!=0))) + {@+free_node(b, box_node_size); + b=hpack(p, z-q, exactly); + } +else{@+e=0; + if (w > z) + {@+free_node(b, box_node_size); + b=hpack(p, z, exactly); + } + } +w=width(b); +} + +@ We try first to center the display without regard to the existence of +the equation number. If that would make it too close (where ``too close'' +means that the space between display and equation number is less than the +width of the equation number), we either center it in the remaining space +or move it as far from the equation number as possible. The latter alternative +is taken only if the display begins with glue, since we assume that the +user put glue there to control the spacing precisely. + +@<Determine the displacement, |d|, of the left edge of the equation...@>= +d=half(z-w); +if ((e > 0)&&(d < 2*e)) /*too close*/ + {@+d=half(z-w-e); + if (p!=null) if (!is_char_node(p)) if (type(p)==glue_node) d=0; + } + +@ If the equation number is set on a line by itself, either before or +after the formula, we append an infinite penalty so that no page break will +separate the display from its number; and we use the same size and +displacement for all three potential lines of the display, even though +`\.{\\parshape}' may specify them differently. + +@<Append the glue or equation number preceding the display@>= +tail_append(new_penalty(pre_display_penalty));@/ +if ((d+s <= pre_display_size)||l) /*not enough clearance*/ + {@+g1=above_display_skip_code;g2=below_display_skip_code; + } +else{@+g1=above_display_short_skip_code; + g2=below_display_short_skip_code; + } +if (l&&(e==0)) /*it follows that |type(a)==hlist_node|*/ + {@+shift_amount(a)=s;append_to_vlist(a); + tail_append(new_penalty(inf_penalty)); + } +else tail_append(new_param_glue(g1)) + +@ @<Append the display and perhaps also the equation number@>= +if (e!=0) + {@+r=new_kern(z-w-e-d); + if (l) + {@+link(a)=r;link(r)=b;b=a;d=0; + } + else{@+link(b)=r;link(r)=a; + } + b=hpack(b, natural); + } +shift_amount(b)=s+d;append_to_vlist(b) + +@ @<Append the glue or equation number following the display@>= +if ((a!=null)&&(e==0)&&!l) + {@+tail_append(new_penalty(inf_penalty)); + shift_amount(a)=s+z-width(a); + append_to_vlist(a); + g2=0; + } +if (t!=adjust_head) /*migrating material comes after equation number*/ + {@+link(tail)=link(adjust_head);tail=t; + } +tail_append(new_penalty(post_display_penalty)); +if (g2 > 0) tail_append(new_param_glue(g2)) + +@ When \.{\\halign} appears in a display, the alignment routines operate +essentially as they do in vertical mode. Then the following program is +activated, with |p| and |q| pointing to the beginning and end of the +resulting list, and with |aux_save| holding the |prev_depth| value. + +@<Finish an alignment in a display@>= +{@+do_assignments(); +if (cur_cmd!=math_shift) @<Pontificate about improper alignment in display@>@; +else@<Check that another \.\$ follows@>; +pop_nest(); +tail_append(new_penalty(pre_display_penalty)); +tail_append(new_param_glue(above_display_skip_code)); +link(tail)=p; +if (p!=null) tail=q; +tail_append(new_penalty(post_display_penalty)); +tail_append(new_param_glue(below_display_skip_code)); +prev_depth=aux_save.sc;resume_after_display(); +} + +@ @<Pontificate...@>= +{@+print_err("Missing $$ inserted"); +@.Missing {\$\$} inserted@> +help2("Displays can use special alignments (like \\eqalignno)",@/ + "only if nothing but the alignment itself is between $$'s."); +back_error(); +} + +@* Mode-independent processing. +The long |main_control| procedure has now been fully specified, except for +certain activities that are independent of the current mode. These activities +do not change the current vlist or hlist or mlist; if they change anything, +it is the value of a parameter or the meaning of a control sequence. + +Assignments to values in |eqtb| can be global or local. Furthermore, a +control sequence can be defined to be `\.{\\long}', `\.{\\protected}', +or `\.{\\outer}', and it might or might not be expanded. The prefixes +`\.{\\global}', `\.{\\long}', `\.{\\protected}', +and `\.{\\outer}' can occur in any order. Therefore we assign binary numeric +codes, making it possible to accumulate the union of all specified prefixes +by adding the corresponding codes. (\PASCAL's |set| operations could also +have been used.) + +@<Put each...@>= +primitive("long", prefix, 1); +@!@:long\_}{\.{\\long} primitive@> +primitive("outer", prefix, 2); +@!@:outer\_}{\.{\\outer} primitive@> +primitive("global", prefix, 4); +@!@:global\_}{\.{\\global} primitive@> +primitive("def", def, 0); +@!@:def\_}{\.{\\def} primitive@> +primitive("gdef", def, 1); +@!@:gdef\_}{\.{\\gdef} primitive@> +primitive("edef", def, 2); +@!@:edef\_}{\.{\\edef} primitive@> +primitive("xdef", def, 3); +@!@:xdef\_}{\.{\\xdef} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case prefix: if (chr_code==1) print_esc("long"); + else if (chr_code==2) print_esc("outer") + @/@<Cases of |prefix| for |print_cmd_chr|@>;@/ + else print_esc("global");@+break; +case def: if (chr_code==0) print_esc("def"); + else if (chr_code==1) print_esc("gdef"); + else if (chr_code==2) print_esc("edef"); + else print_esc("xdef");@+break; + +@ Every prefix, and every command code that might or might not be prefixed, +calls the action procedure |prefixed_command|. This routine accumulates +a sequence of prefixes until coming to a non-prefix, then it carries out +the command. + +@<Cases of |main_control| that don't...@>= +any_mode(toks_register): +any_mode(assign_toks): +any_mode(assign_int): +any_mode(assign_dimen): +any_mode(assign_glue): +any_mode(assign_mu_glue): +any_mode(assign_font_dimen): +any_mode(assign_font_int): +any_mode(set_aux): +any_mode(set_prev_graf): +any_mode(set_page_dimen): +any_mode(set_page_int): +any_mode(set_box_dimen): +any_mode(set_shape): +any_mode(def_code): +any_mode(def_family): +any_mode(set_font): +any_mode(def_font): +any_mode(internal_register): +any_mode(advance): +any_mode(multiply): +any_mode(divide): +any_mode(prefix): +any_mode(let): +any_mode(shorthand_def): +any_mode(read_to_cs): +any_mode(def): +any_mode(set_box): +any_mode(hyph_data): +any_mode(set_interaction): prefixed_command();@+break; + +@ If the user says, e.g., `\.{\\global\\global}', the redundancy is +silently accepted. + +@<Declare act...@>= +@t\4@>@<Declare subprocedures for |prefixed_command|@>@t@>@;@/ +static void prefixed_command(void) +{@+ +small_number a; /*accumulated prefix codes so far*/ +internal_font_number @!f; /*identifies a font*/ +int @!j; /*index into a \.{\\parshape} specification*/ +font_index @!k; /*index into |font_info|*/ +pointer @!p, @!q; /*for temporary short-term use*/ +int @!n; /*ditto*/ +bool @!e; /*should a definition be expanded? or was \.{\\let} not done?*/ +a=0; +while (cur_cmd==prefix) + {@+if (!odd(a/cur_chr)) a=a+cur_chr; + @<Get the next non-blank non-relax...@>; + if (cur_cmd <= max_non_prefixed_command) + @<Discard erroneous prefixes and |return|@>; + if (tracing_commands > 2) if (eTeX_ex) show_cur_cmd_chr(); + } +@<Discard the prefixes \.{\\long} and \.{\\outer} if they are irrelevant@>; +@<Adjust \(f)for the setting of \.{\\globaldefs}@>; +switch (cur_cmd) { +@t\4@>@<Assignments@>@; +default:confusion("prefix"); +@:this can't happen prefix}{\quad prefix@> +} +done: @<Insert a token saved by \.{\\afterassignment}, if any@>; +} + +@ @<Discard erroneous...@>= +{@+print_err("You can't use a prefix with `"); +@.You can't use a prefix with x@> +print_cmd_chr(cur_cmd, cur_chr);print_char('\''); +help1("I'll pretend you didn't say \\long or \\outer or \\global."); +if (eTeX_ex) help_line[0]=@| + "I'll pretend you didn't say \\long or \\outer or \\global or \\protected."; +back_error();return; +} + +@ @<Discard the prefixes...@>= +if (a >= 8) + {@+j=protected_token;a=a-8; + } +else j=0; +if ((cur_cmd!=def)&&((a%4!=0)||(j!=0))) + {@+print_err("You can't use `");print_esc("long");print("' or `"); + print_esc("outer"); + help1("I'll pretend you didn't say \\long or \\outer here."); + if (eTeX_ex) + {@+help_line[0]=@| + "I'll pretend you didn't say \\long or \\outer or \\protected here."; + print("' or `");print_esc("protected"); + } + print("' with `"); +@.You can't use \\long...@> + print_cmd_chr(cur_cmd, cur_chr);print_char('\''); + error(); + } + +@ The previous routine does not have to adjust |a| so that |a%4==0|, +since the following routines test for the \.{\\global} prefix as follows. + +@d global (a >= 4) +@d define(A, B, C) if (global) geq_define(A, B, C);@+else eq_define(A, B, C) +@d word_define(A, B) if (global) geq_word_define(A, B);@+else eq_word_define(A, B) + +@<Adjust \(f)for the setting of \.{\\globaldefs}@>= +if (global_defs!=0) + if (global_defs < 0) + {@+if (global) a=a-4; + } + else{@+if (!global) a=a+4; + } + +@ When a control sequence is to be defined, by \.{\\def} or \.{\\let} or +something similar, the |get_r_token| routine will substitute a special +control sequence for a token that is not redefinable. + +@<Declare subprocedures for |prefixed_command|@>= +static void get_r_token(void) +{@+ +restart: @/do@+{get_token(); +}@+ while (!(cur_tok!=space_token)); +if ((cur_cs==0)||(cur_cs > frozen_control_sequence)) + {@+print_err("Missing control sequence inserted"); +@.Missing control...@> + help5("Please don't say `\\def cs{...}', say `\\def\\cs{...}'.",@/ + "I've inserted an inaccessible control sequence so that your",@/ + "definition will be completed without mixing me up too badly.",@/ + "You can recover graciously from this error, if you're",@/ + "careful; see exercise 27.2 in The TeXbook."); +@:TeXbook}{\sl The \TeX book@> + if (cur_cs==0) back_input(); + cur_tok=cs_token_flag+frozen_protection;ins_error();goto restart; + } +} + +@ @<Initialize table entries...@>= +text(frozen_protection)=s_no("inaccessible"); +@.inaccessible@> + +@ Here's an example of the way many of the following routines operate. +(Unfortunately, they aren't all as simple as this.) + +@<Assignments@>= +case set_font: define(cur_font_loc, data, cur_chr);@+break; + +@ When a |def| command has been scanned, +|cur_chr| is odd if the definition is supposed to be global, and +|cur_chr >= 2| if the definition is supposed to be expanded. + +@<Assignments@>= +case def: {@+uint32_t def_fl; + if (odd(cur_chr)&&!global&&(global_defs >= 0)) a=a+4; + e=(cur_chr >= 2);get_r_token();p=cur_cs; def_fl=cur_file_line; + q=scan_toks(true, e); + if (j!=0) + {@+q=get_avail();info(q)=j;link(q)=link(def_ref); + link(def_ref)=q; + } + define(p, call+(a%4), def_ref); + fl_mem[def_ref]=def_fl; + } @+break; + +@ Both \.{\\let} and \.{\\futurelet} share the command code |let|. + +@<Put each...@>= +primitive("let", let, normal);@/ +@!@:let\_}{\.{\\let} primitive@> +primitive("futurelet", let, normal+1);@/ +@!@:future\_let\_}{\.{\\futurelet} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case let: if (chr_code!=normal) print_esc("futurelet");@+else print_esc("let");@+break; + +@ @<Assignments@>= +case let: {@+n=cur_chr; + get_r_token();p=cur_cs; + if (n==normal) + {@+@/do@+{get_token(); + }@+ while (!(cur_cmd!=spacer)); + if (cur_tok==other_token+'=') + {@+get_token(); + if (cur_cmd==spacer) get_token(); + } + } + else{@+get_token();q=cur_tok;get_token();back_input(); + cur_tok=q;back_input(); /*look ahead, then back up*/ + } /*note that |back_input| doesn't affect |cur_cmd|, |cur_chr|*/ + if (cur_cmd >= call) add_token_ref(cur_chr); + else if ((cur_cmd==internal_register)||(cur_cmd==toks_register)) + if ((cur_chr < mem_bot)||(cur_chr > lo_mem_stat_max)) + add_sa_ref(cur_chr); + define(p, cur_cmd, cur_chr); + } @+break; + +@ A \.{\\chardef} creates a control sequence whose |cmd| is |char_given|; +a \.{\\mathchardef} creates a control sequence whose |cmd| is |math_given|; +and the corresponding |chr| is the character code or math code. A \.{\\countdef} +or \.{\\dimendef} or \.{\\skipdef} or \.{\\muskipdef} creates a control +sequence whose |cmd| is |assign_int| or \dots\ or |assign_mu_glue|, and the +corresponding |chr| is the |eqtb| location of the internal register in question. + +@d char_def_code 0 /*|shorthand_def| for \.{\\chardef}*/ +@d math_char_def_code 1 /*|shorthand_def| for \.{\\mathchardef}*/ +@d count_def_code 2 /*|shorthand_def| for \.{\\countdef}*/ +@d dimen_def_code 3 /*|shorthand_def| for \.{\\dimendef}*/ +@d skip_def_code 4 /*|shorthand_def| for \.{\\skipdef}*/ +@d mu_skip_def_code 5 /*|shorthand_def| for \.{\\muskipdef}*/ +@d toks_def_code 6 /*|shorthand_def| for \.{\\toksdef}*/ + +@<Put each...@>= +primitive("chardef", shorthand_def, char_def_code);@/ +@!@:char\_def\_}{\.{\\chardef} primitive@> +primitive("mathchardef", shorthand_def, math_char_def_code);@/ +@!@:math\_char\_def\_}{\.{\\mathchardef} primitive@> +primitive("countdef", shorthand_def, count_def_code);@/ +@!@:count\_def\_}{\.{\\countdef} primitive@> +primitive("dimendef", shorthand_def, dimen_def_code);@/ +@!@:dimen\_def\_}{\.{\\dimendef} primitive@> +primitive("skipdef", shorthand_def, skip_def_code);@/ +@!@:skip\_def\_}{\.{\\skipdef} primitive@> +primitive("muskipdef", shorthand_def, mu_skip_def_code);@/ +@!@:mu\_skip\_def\_}{\.{\\muskipdef} primitive@> +primitive("toksdef", shorthand_def, toks_def_code);@/ +@!@:toks\_def\_}{\.{\\toksdef} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case shorthand_def: switch (chr_code) { + case char_def_code: print_esc("chardef");@+break; + case math_char_def_code: print_esc("mathchardef");@+break; + case count_def_code: print_esc("countdef");@+break; + case dimen_def_code: print_esc("dimendef");@+break; + case skip_def_code: print_esc("skipdef");@+break; + case mu_skip_def_code: print_esc("muskipdef");@+break; + default:print_esc("toksdef"); + } @+break; +case char_given: {@+print_esc("char");print_hex(chr_code); + } @+break; +case math_given: {@+print_esc("mathchar");print_hex(chr_code); + } @+break; + +@ We temporarily define |p| to be |relax|, so that an occurrence of |p| +while scanning the definition will simply stop the scanning instead of +producing an ``undefined control sequence'' error or expanding the +previous meaning. This allows, for instance, `\.{\\chardef\\foo=123\\foo}'. + +@<Assignments@>= +case shorthand_def: {@+n=cur_chr;get_r_token();p=cur_cs;define(p, relax, 256); + scan_optional_equals(); + switch (n) { + case char_def_code: {@+scan_char_num();define(p, char_given, cur_val); + } @+break; + case math_char_def_code: {@+scan_fifteen_bit_int();define(p, math_given, cur_val); + } @+break; + default:{@+scan_register_num(); + if (cur_val > 255) + {@+j=n-count_def_code; /*|int_val dotdot box_val|*/ + if (j > mu_val) j=tok_val; /*|int_val dotdot mu_val| or |tok_val|*/ + find_sa_element(j, cur_val, true);add_sa_ref(cur_ptr); + if (j==tok_val) j=toks_register;@+else j=internal_register; + define(p, j, cur_ptr); + } + else + switch (n) { + case count_def_code: define(p, assign_int, count_base+cur_val);@+break; + case dimen_def_code: define(p, assign_dimen, scaled_base+cur_val);@+break; + case skip_def_code: define(p, assign_glue, skip_base+cur_val);@+break; + case mu_skip_def_code: define(p, assign_mu_glue, mu_skip_base+cur_val);@+break; + case toks_def_code: define(p, assign_toks, toks_base+cur_val); + } /*there are no other cases*/ + } + } + } @+break; + +@ @<Assignments@>= +case read_to_cs: {@+j=cur_chr;scan_int();n=cur_val; + if (!scan_keyword("to")) +@.to@> + {@+print_err("Missing `to' inserted"); +@.Missing `to'...@> + help2("You should have said `\\read<number> to \\cs'.",@/ + "I'm going to look for the \\cs now.");error(); + } + get_r_token(); + p=cur_cs;read_toks(n, p, j);define(p, call, cur_val); + } @+break; + +@ The token-list parameters, \.{\\output} and \.{\\everypar}, etc., receive +their values in the following way. (For safety's sake, we place an +enclosing pair of braces around an \.{\\output} list.) + +@<Assignments@>= +case toks_register: case assign_toks: {@+uint32_t def_fl=cur_file_line; q=cur_cs; + e=false; /*just in case, will be set |true| for sparse array elements*/ + if (cur_cmd==toks_register) + if (cur_chr==mem_bot) + {@+scan_register_num(); + if (cur_val > 255) + {@+find_sa_element(tok_val, cur_val, true); + cur_chr=cur_ptr;e=true; + } + else cur_chr=toks_base+cur_val; + } + else e=true; + p=cur_chr; /*|p==every_par_loc| or |output_routine_loc| or \dots*/ + scan_optional_equals(); + @<Get the next non-blank non-relax non-call token@>; + if (cur_cmd!=left_brace) @<If the right-hand side is a token parameter or +token register, finish the assignment and |goto done|@>; + back_input();cur_cs=q;q=scan_toks(false, false); + if (link(def_ref)==null) /*empty list: revert to the default*/ + {@+sa_define(p, null, p, undefined_cs, null);free_avail(def_ref); + } + else{@+if ((p==output_routine_loc)&&!e) /*enclose in curlies*/ + {@+link(q)=get_avail();q=link(q); + info(q)=right_brace_token+'}'; + fl_mem[q]=FILE_LINE(system_file, system_insert); + q=get_avail();info(q)=left_brace_token+'{'; + fl_mem[q]=FILE_LINE(system_file, system_insert); + link(q)=link(def_ref);link(def_ref)=q; + } + sa_define(p, def_ref, p, call, def_ref); + fl_mem[def_ref]=def_fl; + } + } @+break; + +@ @<If the right-hand side is a token parameter...@>= +if ((cur_cmd==toks_register)||(cur_cmd==assign_toks)) + {@+if (cur_cmd==toks_register) + if (cur_chr==mem_bot) + {@+scan_register_num(); + if (cur_val < 256) q=equiv(toks_base+cur_val); + else{@+find_sa_element(tok_val, cur_val, false); + if (cur_ptr==null) q=null; + else q=sa_ptr(cur_ptr); + } + } + else q=sa_ptr(cur_chr); + else q=equiv(cur_chr); + if (q==null) sa_define(p, null, p, undefined_cs, null); + else{@+add_token_ref(q);sa_define(p, q, p, call, q); + } + goto done; + } + +@ Similar routines are used to assign values to the numeric parameters. + +@<Assignments@>= +case assign_int: {@+p=cur_chr;scan_optional_equals();scan_int(); + word_define(p, cur_val); + } @+break; +case assign_dimen: {@+p=cur_chr;scan_optional_equals(); + scan_normal_dimen;word_define(p, cur_val); + } @+break; +case assign_glue: case assign_mu_glue: {@+p=cur_chr;n=cur_cmd;scan_optional_equals(); + if (n==assign_mu_glue) scan_glue(mu_val);@+else scan_glue(glue_val); + trap_zero_glue(); + define(p, glue_ref, cur_val); + } @+break; + +@ When a glue register or parameter becomes zero, it will always point to +|zero_glue| because of the following procedure. (Exception: The tabskip +glue isn't trapped while preambles are being scanned.) + +@<Declare subprocedures for |prefixed_command|@>= +static void trap_zero_glue(void) +{@+if ((width(cur_val)==0)&&(stretch(cur_val)==0)&&(shrink(cur_val)==0)) + {@+add_glue_ref(zero_glue); + delete_glue_ref(cur_val);cur_val=zero_glue; + } +} + +@ The various character code tables are changed by the |def_code| commands, +and the font families are declared by |def_family|. + +@<Put each...@>= +primitive("catcode", def_code, cat_code_base); +@!@:cat\_code\_}{\.{\\catcode} primitive@> +primitive("mathcode", def_code, math_code_base); +@!@:math\_code\_}{\.{\\mathcode} primitive@> +primitive("lccode", def_code, lc_code_base); +@!@:lc\_code\_}{\.{\\lccode} primitive@> +primitive("uccode", def_code, uc_code_base); +@!@:uc\_code\_}{\.{\\uccode} primitive@> +primitive("sfcode", def_code, sf_code_base); +@!@:sf\_code\_}{\.{\\sfcode} primitive@> +primitive("delcode", def_code, del_code_base); +@!@:del\_code\_}{\.{\\delcode} primitive@> +primitive("textfont", def_family, math_font_base); +@!@:text\_font\_}{\.{\\textfont} primitive@> +primitive("scriptfont", def_family, math_font_base+script_size); +@!@:script\_font\_}{\.{\\scriptfont} primitive@> +primitive("scriptscriptfont", def_family, math_font_base+script_script_size); +@!@:script\_script\_font\_}{\.{\\scriptscriptfont} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case def_code: if (chr_code==cat_code_base) print_esc("catcode"); + else if (chr_code==math_code_base) print_esc("mathcode"); + else if (chr_code==lc_code_base) print_esc("lccode"); + else if (chr_code==uc_code_base) print_esc("uccode"); + else if (chr_code==sf_code_base) print_esc("sfcode"); + else print_esc("delcode");@+break; +case def_family: print_size(chr_code-math_font_base);@+break; + +@ The different types of code values have different legal ranges; the +following program is careful to check each case properly. + +@<Assignments@>= +case def_code: {@+@<Let |n| be the largest legal code value, based on |cur_chr|@>; + p=cur_chr;scan_char_num();p=p+cur_val;scan_optional_equals(); + scan_int(); + if (((cur_val < 0)&&(p < del_code_base))||(cur_val > n)) + {@+print_err("Invalid code (");print_int(cur_val); +@.Invalid code@> + if (p < del_code_base) print("), should be in the range 0.."); + else print("), should be at most "); + print_int(n); + help1("I'm going to use 0 instead of that illegal code value.");@/ + error();cur_val=0; + } + if (p < math_code_base) define(p, data, cur_val); + else if (p < del_code_base) define(p, data, hi(cur_val)); + else word_define(p, cur_val); + } @+break; + +@ @<Let |n| be the largest...@>= +if (cur_chr==cat_code_base) n=max_char_code; +else if (cur_chr==math_code_base) n=0100000; +else if (cur_chr==sf_code_base) n=077777; +else if (cur_chr==del_code_base) n=077777777; +else n=255 + +@ @<Assignments@>= +case def_family: {@+p=cur_chr;scan_four_bit_int();p=p+cur_val; + scan_optional_equals();scan_font_ident();define(p, data, cur_val); + } @+break; + +@ Next we consider changes to \TeX's numeric registers. + +@<Assignments@>= +case internal_register: case advance: + case multiply: case divide: do_register_command(a);@+break; + +@ We use the fact that |internal_register < advance < multiply < divide|. + +@<Declare subprocedures for |prefixed_command|@>= +static void do_register_command(small_number @!a) +{@+ +pointer l, @!q, @!r, @!s; /*for list manipulation*/ +int @!p; /*type of register involved*/ +bool @!e; /*does |l| refer to a sparse array element?*/ +int @!w; /*integer or dimen value of |l|*/ +q=cur_cmd; +e=false; /*just in case, will be set |true| for sparse array elements*/ +@<Compute the register location |l| and its type |p|; but |return| if invalid@>; +if (q==internal_register) scan_optional_equals(); +else if (scan_keyword("by")) do_nothing; /*optional `\.{by}'*/ +@.by@> +arith_error=false; +if (q < multiply) @<Compute result of |register| or |advance|, put it in |cur_val|@>@; +else@<Compute result of |multiply| or |divide|, put it in |cur_val|@>; +if (arith_error) + {@+print_err("Arithmetic overflow"); +@.Arithmetic overflow@> + help2("I can't carry out that multiplication or division,",@/ + "since the result is out of range."); + if (p >= glue_val) delete_glue_ref(cur_val); + error();return; + } +if (p < glue_val) sa_word_define(l, cur_val); +else{@+trap_zero_glue();sa_define(l, cur_val, l, glue_ref, cur_val); + } +} + +@ Here we use the fact that the consecutive codes |int_val dotdot mu_val| and +|assign_int dotdot assign_mu_glue| correspond to each other nicely. + +@<Compute the register location |l| and its type |p|...@>= +{@+if (q!=internal_register) + {@+get_x_token(); + if ((cur_cmd >= assign_int)&&(cur_cmd <= assign_mu_glue)) + {@+l=cur_chr;p=cur_cmd-assign_int;goto found; + } + if (cur_cmd!=internal_register) + {@+print_err("You can't use `");print_cmd_chr(cur_cmd, cur_chr); +@.You can't use x after ...@> + print("' after ");print_cmd_chr(q, 0); + help1("I'm forgetting what you said and not changing anything."); + error();return; + } + } +if ((cur_chr < mem_bot)||(cur_chr > lo_mem_stat_max)) + {@+l=cur_chr;p=sa_type(l);e=true; + } +else{@+p=cur_chr-mem_bot;scan_register_num(); + if (cur_val > 255) + {@+find_sa_element(p, cur_val, true);l=cur_ptr;e=true; + } + else +switch (p) { +case int_val: l=cur_val+count_base;@+break; +case dimen_val: l=cur_val+scaled_base;@+break; +case glue_val: l=cur_val+skip_base;@+break; +case mu_val: l=cur_val+mu_skip_base; +} /*there are no other cases*/ + } +} +found: if (p < glue_val) @+if (e) w=sa_int(l);@+else w=eqtb[l].i; +else if (e) s=sa_ptr(l);@+else s=equiv(l) + +@ @<Compute result of |register| or |advance|...@>= +if (p < glue_val) + {@+if (p==int_val) scan_int();@+else scan_normal_dimen; + if (q==advance) cur_val=cur_val+w; + } +else{@+scan_glue(p); + if (q==advance) @<Compute the sum of two glue specs@>; + } + +@ @<Compute the sum of two glue specs@>= +{@+q=new_spec(cur_val);r=s; +delete_glue_ref(cur_val); +width(q)=width(q)+width(r); +if (stretch(q)==0) stretch_order(q)=normal; +if (stretch_order(q)==stretch_order(r)) stretch(q)=stretch(q)+stretch(r); +else if ((stretch_order(q) < stretch_order(r))&&(stretch(r)!=0)) + {@+stretch(q)=stretch(r);stretch_order(q)=stretch_order(r); + } +if (shrink(q)==0) shrink_order(q)=normal; +if (shrink_order(q)==shrink_order(r)) shrink(q)=shrink(q)+shrink(r); +else if ((shrink_order(q) < shrink_order(r))&&(shrink(r)!=0)) + {@+shrink(q)=shrink(r);shrink_order(q)=shrink_order(r); + } +cur_val=q; +} + +@ @<Compute result of |multiply| or |divide|...@>= +{@+scan_int(); +if (p < glue_val) + if (q==multiply) + if (p==int_val) cur_val=mult_integers(w, cur_val); + else cur_val=nx_plus_y(w, cur_val, 0); + else cur_val=x_over_n(w, cur_val); +else{@+r=new_spec(s); + if (q==multiply) + {@+width(r)=nx_plus_y(width(s), cur_val, 0); + stretch(r)=nx_plus_y(stretch(s), cur_val, 0); + shrink(r)=nx_plus_y(shrink(s), cur_val, 0); + } + else{@+width(r)=x_over_n(width(s), cur_val); + stretch(r)=x_over_n(stretch(s), cur_val); + shrink(r)=x_over_n(shrink(s), cur_val); + } + cur_val=r; + } +} + +@ The processing of boxes is somewhat different, because we may need +to scan and create an entire box before we actually change the value of the old +one. + +@<Assignments@>= +case set_box: {@+scan_register_num(); + if (global) n=global_box_flag+cur_val;@+else n=box_flag+cur_val; + scan_optional_equals(); + if (set_box_allowed) scan_box(n); + else{@+print_err("Improper ");print_esc("setbox"); +@.Improper \\setbox@> + help2("Sorry, \\setbox is not allowed after \\halign in a display,",@/ + "or between \\accent and an accented character.");error(); + } + } @+break; + +@ The |space_factor| or |prev_depth| settings are changed when a |set_aux| +command is sensed. Similarly, |prev_graf| is changed in the presence of +|set_prev_graf|, and |dead_cycles| or |insert_penalties| in the presence of +|set_page_int|. These definitions are always global. + +When some dimension of a box register is changed, the change isn't exactly +global; but \TeX\ does not look at the \.{\\global} switch. + +@<Assignments@>= +case set_aux: alter_aux();@+break; +case set_prev_graf: alter_prev_graf();@+break; +case set_page_dimen: alter_page_so_far();@+break; +case set_page_int: alter_integer();@+break; +case set_box_dimen: alter_box_dimen();@+break; + +@ @<Declare subprocedures for |prefixed_command|@>= +static void alter_aux(void) +{@+halfword c; /*|hmode| or |vmode|*/ +if (cur_chr!=abs(mode)) report_illegal_case(); +else{@+c=cur_chr;scan_optional_equals(); + if (c==vmode) + {@+scan_normal_dimen;prev_depth=cur_val; + } + else{@+scan_int(); + if ((cur_val <= 0)||(cur_val > 32767)) + {@+print_err("Bad space factor"); +@.Bad space factor@> + help1("I allow only values in the range 1..32767 here."); + int_error(cur_val); + } + else space_factor=cur_val; + } + } +} + +@ @<Declare subprocedures for |prefixed_command|@>= +static void alter_prev_graf(void) +{@+int p; /*index into |nest|*/ +nest[nest_ptr]=cur_list;p=nest_ptr; +while (abs(nest[p].mode_field)!=vmode) decr(p); +scan_optional_equals();scan_int(); +if (cur_val < 0) + {@+print_err("Bad ");print_esc("prevgraf"); +@.Bad \\prevgraf@> + help1("I allow only nonnegative values here."); + int_error(cur_val); + } +else{@+nest[p].pg_field=cur_val;cur_list=nest[nest_ptr]; + } +} + +@ @<Declare subprocedures for |prefixed_command|@>= +static void alter_page_so_far(void) +{@+int c; /*index into |page_so_far|*/ +c=cur_chr;scan_optional_equals();scan_normal_dimen; +page_so_far[c]=cur_val; +} + +@ @<Declare subprocedures for |prefixed_command|@>= +static void alter_integer(void) +{@+small_number c; + /*0 for \.{\\deadcycles}, 1 for \.{\\insertpenalties}, etc.*/ +c=cur_chr;scan_optional_equals();scan_int(); +if (c==0) dead_cycles=cur_val +@/@<Cases for |alter_integer|@>@;@/ +else insert_penalties=cur_val; +} + +@ @<Declare subprocedures for |prefixed_command|@>= +static void alter_box_dimen(void) +{@+small_number c; /*|width_offset| or |height_offset| or |depth_offset|*/ +pointer @!b; /*box register*/ +c=cur_chr;scan_register_num();fetch_box(b);scan_optional_equals(); +scan_normal_dimen; +if (b!=null) mem[b+c].sc=cur_val; +} + +@ Paragraph shapes are set up in the obvious way. + +@<Assignments@>= +case set_shape: {@+q=cur_chr;scan_optional_equals();scan_int();n=cur_val; + if (n <= 0) p=null; + else if (q > par_shape_loc) + {@+n=(cur_val/2)+1;p=get_node(2*n+1);info(p)=n; + n=cur_val;mem[p+1].i=n; /*number of penalties*/ + for (j=p+2; j<=p+n+1; j++) + {@+scan_int();mem[j].i=cur_val; /*penalty values*/ + } + if (!odd(n)) mem[p+n+2].i=0; /*unused*/ + } + else{@+p=get_node(2*n+1);info(p)=n; + for (j=1; j<=n; j++) + {@+scan_normal_dimen; + mem[p+2*j-1].sc=cur_val; /*indentation*/ + scan_normal_dimen; + mem[p+2*j].sc=cur_val; /*width*/ + } + } + define(q, shape_ref, p); + } @+break; + +@ Here's something that isn't quite so obvious. It guarantees that +|info(par_shape_ptr)| can hold any positive~|n| for which |get_node(2*n+1)| +doesn't overflow the memory capacity. + +@<Check the ``constant''...@>= +if (2*max_halfword < mem_top-mem_min) bad=41; + +@ New hyphenation data is loaded by the |hyph_data| command. + +@<Put each...@>= +primitive("hyphenation", hyph_data, 0); +@!@:hyphenation\_}{\.{\\hyphenation} primitive@> +primitive("patterns", hyph_data, 1); +@!@:patterns\_}{\.{\\patterns} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case hyph_data: if (chr_code==1) print_esc("patterns"); + else print_esc("hyphenation");@+break; + +@ @<Assignments@>= +case hyph_data: if (cur_chr==1) + { +#ifdef @!INIT +new_patterns();goto done;@; +#endif + print_err("Patterns can be loaded only by INITEX"); +@.Patterns can be...@> + help0;error(); + @/do@+{get_token();}@+ while (!(cur_cmd==right_brace)); /*flush the patterns*/ + return; + } + else{@+new_hyph_exceptions();goto done; + } @+break; + +@ All of \TeX's parameters are kept in |eqtb| except the font information, +the interaction mode, and the hyphenation tables; these are strictly global. + +@<Assignments@>= +case assign_font_dimen: {@+find_font_dimen(true);k=cur_val; + scan_optional_equals();scan_normal_dimen;font_info[k].sc=cur_val; + } @+break; +case assign_font_int: {@+n=cur_chr;scan_font_ident();f=cur_val; + scan_optional_equals();scan_int(); + if (n==0) hyphen_char[f]=cur_val;@+else skew_char[f]=cur_val; + } @+break; + +@ @<Put each...@>= +primitive("hyphenchar", assign_font_int, 0); +@!@:hyphen\_char\_}{\.{\\hyphenchar} primitive@> +primitive("skewchar", assign_font_int, 1); +@!@:skew\_char\_}{\.{\\skewchar} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case assign_font_int: if (chr_code==0) print_esc("hyphenchar"); + else print_esc("skewchar");@+break; + +@ Here is where the information for a new font gets loaded. + +@<Assignments@>= +case def_font: new_font(a);@+break; + +@ @<Declare subprocedures for |prefixed_command|@>= +static void new_font(small_number @!a) +{@+ +pointer u; /*user's font identifier*/ +scaled @!s; /*stated ``at'' size, or negative of scaled magnification*/ +int @!f; /*runs through existing fonts*/ +str_number @!t; /*name for the frozen font identifier*/ +int @!old_setting; /*holds |selector| setting*/ +str_number @!flushable_string; /*string not yet referenced*/ +if (job_name==0) open_log_file(); + /*avoid confusing \.{texput} with the font name*/ +@.texput@> +get_r_token();u=cur_cs; +if (u >= hash_base) t=text(u); +else if (u >= single_base) + if (u==null_cs) t=s_no("FONT");@+else t=u-single_base; +else{@+old_setting=selector;selector=new_string; + print("FONT");printn(u-active_base);selector=old_setting; +@.FONTx@> + str_room(1);t=make_string(); + } +define(u, set_font, null_font);scan_optional_equals();scan_file_name(); +@<Scan the font size specification@>; +@<If this font has already been loaded, set |f| to the internal font number +and |goto common_ending|@>; +f=read_font_info(u, cur_name, cur_area, s); +common_ending: define(u, set_font, f);eqtb[font_id_base+f]=eqtb[u];font_id_text(f)=t; +} + +@ @<Scan the font size specification@>= +name_in_progress=true; /*this keeps |cur_name| from being changed*/ +if (scan_keyword("at")) @<Put the \(p)(positive) `at' size into |s|@>@; +@.at@> +else if (scan_keyword("scaled")) +@.scaled@> + {@+scan_int();s=-cur_val; + if ((cur_val <= 0)||(cur_val > 32768)) + {@+print_err("Illegal magnification has been changed to 1000");@/ +@.Illegal magnification...@> + help1("The magnification ratio must be between 1 and 32768."); + int_error(cur_val);s=-1000; + } + } +else s=-1000; +name_in_progress=false + +@ @<Put the \(p)(positive) `at' size into |s|@>= +{@+scan_normal_dimen;s=cur_val; +if ((s <= 0)||(s >= 01000000000)) + {@+print_err("Improper `at' size ("); + print_scaled(s);print("pt), replaced by 10pt"); +@.Improper `at' size...@> + help2("I can only handle fonts at positive sizes that are",@/ + "less than 2048pt, so I've changed what you said to 10pt."); + error();s=10*unity; + } +} + +@ When the user gives a new identifier to a font that was previously loaded, +the new name becomes the font identifier of record. Font names `\.{xyz}' and +`\.{XYZ}' are considered to be different. + +@<If this font has already been loaded...@>= +flushable_string=str_ptr-1; +for (f=font_base+1; f<=font_ptr; f++) + if (str_eq_str(font_name[f], cur_name)&&str_eq_str(font_area[f], cur_area)) + {@+if (cur_name==flushable_string) + {@+flush_string;cur_name=font_name[f]; + } + if (s > 0) + {@+if (s==font_size[f]) goto common_ending; + } + else if (font_size[f]==xn_over_d(font_dsize[f],-s, 1000)) + goto common_ending; + } + +@ @<Cases of |print_cmd_chr|...@>= +case set_font: {@+print("select font ");slow_print(font_name[chr_code]); + if (font_size[chr_code]!=font_dsize[chr_code]) + {@+print(" at ");print_scaled(font_size[chr_code]); + print("pt"); + } + } @+break; + +@ @<Put each...@>= +primitive("batchmode", set_interaction, batch_mode); +@!@:batch\_mode\_}{\.{\\batchmode} primitive@> +primitive("nonstopmode", set_interaction, nonstop_mode); +@!@:nonstop\_mode\_}{\.{\\nonstopmode} primitive@> +primitive("scrollmode", set_interaction, scroll_mode); +@!@:scroll\_mode\_}{\.{\\scrollmode} primitive@> +primitive("errorstopmode", set_interaction, error_stop_mode); +@!@:error\_stop\_mode\_}{\.{\\errorstopmode} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case set_interaction: switch (chr_code) { + case batch_mode: print_esc("batchmode");@+break; + case nonstop_mode: print_esc("nonstopmode");@+break; + case scroll_mode: print_esc("scrollmode");@+break; + default:print_esc("errorstopmode"); + } @+break; + +@ @<Assignments@>= +case set_interaction: new_interaction();@+break; + +@ @<Declare subprocedures for |prefixed_command|@>= +static void new_interaction(void) +{@+print_ln(); +interaction=cur_chr; +@<Initialize the print |selector| based on |interaction|@>; +if (log_opened) selector=selector+2; +} + +@ The \.{\\afterassignment} command puts a token into the global +variable |after_token|. This global variable is examined just after +every assignment has been performed. + +@<Glob...@>= +static halfword @!after_token; /*zero, or a saved token*/ + +@ @<Set init...@>= +after_token=0; + +@ @<Cases of |main_control| that don't...@>= +any_mode(after_assignment): {@+get_token();after_token=cur_tok; + } @+break; + +@ @<Insert a token saved by \.{\\afterassignment}, if any@>= +if (after_token!=0) + {@+cur_tok=after_token;back_input();after_token=0; + } + +@ Here is a procedure that might be called `Get the next non-blank non-relax +non-call non-assignment token'. + +@<Declare act...@>= +static void do_assignments(void) +{@+ +loop{@+@<Get the next non-blank non-relax...@>; + if (cur_cmd <= max_non_prefixed_command) return; + set_box_allowed=false;prefixed_command();set_box_allowed=true; + } +} + +@ @<Cases of |main_control| that don't...@>= +any_mode(after_group): {@+get_token();save_for_after(cur_tok); + } @+break; + +@ Files for \.{\\read} are opened and closed by the |in_stream| command. + +@<Put each...@>= +primitive("openin", in_stream, 1); +@!@:open\_in\_}{\.{\\openin} primitive@> +primitive("closein", in_stream, 0); +@!@:close\_in\_}{\.{\\closein} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case in_stream: if (chr_code==0) print_esc("closein"); + else print_esc("openin");@+break; + +@ @<Cases of |main_control| that don't...@>= +any_mode(in_stream): open_or_close_in();@+break; + +@ @<Declare act...@>= +static void open_or_close_in(void) +{@+int c; /*1 for \.{\\openin}, 0 for \.{\\closein}*/ +int @!n; /*stream number*/ +c=cur_chr;scan_four_bit_int();n=cur_val; +if (read_open[n]!=closed) + {@+a_close(&read_file[n]);read_open[n]=closed; + } +if (c!=0) + {@+scan_optional_equals();scan_file_name(); + pack_cur_name(".tex"); + if (a_open_in(&read_file[n])) + { read_open[n]=just_open; + @<Set new |read_file_num[n]|@>@; + } + } +} + +@ The user can issue messages to the terminal, regardless of the +current mode. + +@<Cases of |main_control| that don't...@>= +any_mode(message): issue_message();@+break; + +@ @<Put each...@>= +primitive("message", message, 0); +@!@:message\_}{\.{\\message} primitive@> +primitive("errmessage", message, 1); +@!@:err\_message\_}{\.{\\errmessage} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case message: if (chr_code==0) print_esc("message"); + else print_esc("errmessage");@+break; + +@ @<Declare act...@>= +static void issue_message(void) +{@+int old_setting; /*holds |selector| setting*/ +int @!c; /*identifies \.{\\message} and \.{\\errmessage}*/ +str_number @!s; /*the message*/ +c=cur_chr;link(garbage)=scan_toks(false, true); +old_setting=selector;selector=new_string; +token_show(def_ref);selector=old_setting; +flush_list(def_ref); +str_room(1);s=make_string(); +if (c==0) @<Print string |s| on the terminal@>@; +else@<Print string |s| as an error message@>; +flush_string; +} + +@ @<Print string |s| on the terminal@>= +{@+if (term_offset+length(s) > max_print_line-2) print_ln(); +else if ((term_offset > 0)||(file_offset > 0)) print_char(' '); +slow_print(s);update_terminal; +} + +@ If \.{\\errmessage} occurs often in |scroll_mode|, without user-defined +\.{\\errhelp}, we don't want to give a long help message each time. So we +give a verbose explanation only once. + +@<Glob...@>= +static bool @!long_help_seen; /*has the long \.{\\errmessage} help been used?*/ + +@ @<Set init...@>=long_help_seen=false; + +@ @<Print string |s| as an error message@>= +{@+print_err("");slow_print(s); +if (err_help!=null) use_err_help=true; +else if (long_help_seen) help1("(That was another \\errmessage.)")@; +else{@+if (interaction < error_stop_mode) long_help_seen=true; + help4("This error message was generated by an \\errmessage",@/ + "command, so I can't give any explicit help.",@/ + "Pretend that you're Hercule Poirot: Examine all clues,",@/ +@^Poirot, Hercule@> + "and deduce the truth by order and method."); + } +error();use_err_help=false; +} + +@ The |error| routine calls on |give_err_help| if help is requested from +the |err_help| parameter. + +@p static void give_err_help(void) +{@+token_show(err_help); +} + +@ The \.{\\uppercase} and \.{\\lowercase} commands are implemented by +building a token list and then changing the cases of the letters in it. + +@<Cases of |main_control| that don't...@>= +any_mode(case_shift): shift_case();@+break; + +@ @<Put each...@>= +primitive("lowercase", case_shift, lc_code_base); +@!@:lowercase\_}{\.{\\lowercase} primitive@> +primitive("uppercase", case_shift, uc_code_base); +@!@:uppercase\_}{\.{\\uppercase} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case case_shift: if (chr_code==lc_code_base) print_esc("lowercase"); + else print_esc("uppercase");@+break; + +@ @<Declare act...@>= +static void shift_case(void) +{@+pointer b; /*|lc_code_base| or |uc_code_base|*/ +pointer @!p; /*runs through the token list*/ +halfword @!t; /*token*/ +eight_bits @!c; /*character code*/ +b=cur_chr;p=scan_toks(false, false);p=link(def_ref); +while (p!=null) + {@+@<Change the case of the token in |p|, if a change is appropriate@>; + p=link(p); + } +back_list(link(def_ref));free_avail(def_ref); /*omit reference count*/ +} + +@ When the case of a |chr_code| changes, we don't change the |cmd|. +We also change active characters, using the fact that +|cs_token_flag+active_base| is a multiple of~256. +@^data structure assumptions@> + +@<Change the case of the token in |p|, if a change is appropriate@>= +t=info(p); +if (t < cs_token_flag+single_base) + {@+c=t%256; + if (equiv(b+c)!=0) info(p)=t-c+equiv(b+c); + } + +@ We come finally to the last pieces missing from |main_control|, namely the +`\.{\\show}' commands that are useful when debugging. + +@<Cases of |main_control| that don't...@>= +any_mode(xray): show_whatever();@+break; + +@ @d show_code 0 /* \.{\\show} */ +@d show_box_code 1 /* \.{\\showbox} */ +@d show_the_code 2 /* \.{\\showthe} */ +@d show_lists_code 3 /* \.{\\showlists} */ + +@<Put each...@>= +primitive("show", xray, show_code); +@!@:show\_}{\.{\\show} primitive@> +primitive("showbox", xray, show_box_code); +@!@:show\_box\_}{\.{\\showbox} primitive@> +primitive("showthe", xray, show_the_code); +@!@:show\_the\_}{\.{\\showthe} primitive@> +primitive("showlists", xray, show_lists_code); +@!@:show\_lists\_code\_}{\.{\\showlists} primitive@> + +@ @<Cases of |print_cmd_chr|...@>= +case xray: switch (chr_code) { + case show_box_code: print_esc("showbox");@+break; + case show_the_code: print_esc("showthe");@+break; + case show_lists_code: print_esc("showlists");@+break; + @<Cases of |xray| for |print_cmd_chr|@>@;@/ + default:print_esc("show"); + } @+break; + +@ @<Declare act...@>= +static void show_whatever(void) +{@+ +pointer p; /*tail of a token list to show*/ +small_number @!t; /*type of conditional being shown*/ +int @!m; /*upper bound on |fi_or_else| codes*/ +int @!l; /*line where that conditional began*/ +int @!n; /*level of \.{\\if...\\fi} nesting*/ +switch (cur_chr) { +case show_lists_code: {@+begin_diagnostic();show_activities(); + } @+break; +case show_box_code: @<Show the current contents of a box@>@;@+break; +case show_code: @<Show the current meaning of a token, then |goto common_ending|@>@; +@<Cases for |show_whatever|@>@;@/ +default:@<Show the current value of some parameter or register, then |goto +common_ending|@>@; +} @/ +@<Complete a potentially long \.{\\show} command@>; +common_ending: if (interaction < error_stop_mode) + {@+help0;decr(error_count); + } +else if (tracing_online > 0) + {@+@t@>@;@/ + help3("This isn't an error message; I'm just \\showing something.",@/ + "Type `I\\show...' to show more (e.g., \\show\\cs,",@/ + "\\showthe\\count10, \\showbox255, \\showlists)."); + } +else{@+@t@>@;@/ + help5("This isn't an error message; I'm just \\showing something.",@/ + "Type `I\\show...' to show more (e.g., \\show\\cs,",@/ + "\\showthe\\count10, \\showbox255, \\showlists).",@/ + "And type `I\\tracingonline=1\\show...' to show boxes and",@/ + "lists on your terminal as well as in the transcript file."); + } +error(); +} + +@ @<Show the current meaning of a token...@>= +{@+get_token(); +if (interaction==error_stop_mode) wake_up_terminal; +print_nl("> "); +if (cur_cs!=0) + {@+sprint_cs(cur_cs);print_char('='); + } +print_meaning();goto common_ending; +} + +@ @<Cases of |print_cmd_chr|...@>= +case undefined_cs: print("undefined");@+break; +case call: case long_call: case outer_call: + case long_outer_call: {@+n=cmd-call; + if (info(link(chr_code))==protected_token) n=n+4; + if (odd(n/4)) print_esc("protected"); + if (odd(n)) print_esc("long"); + if (odd(n/2)) print_esc("outer"); + if (n > 0) print_char(' '); + print("macro"); + } @+break; +case end_template: print_esc("outer endtemplate");@+break; + +@ @<Show the current contents of a box@>= +{@+scan_register_num();fetch_box(p);begin_diagnostic(); +print_nl("> \\box");print_int(cur_val);print_char('='); +if (p==null) print("void");@+else show_box(p); +} + +@ @<Show the current value of some parameter...@>= +{@+the_toks(); +if (interaction==error_stop_mode) wake_up_terminal; +print_nl("> ");token_show(temp_head); +flush_list(link(temp_head));goto common_ending; +} + +@ @<Complete a potentially long \.{\\show} command@>= +end_diagnostic(true);print_err("OK"); +@.OK@> +if (selector==term_and_log) if (tracing_online <= 0) + {@+selector=term_only;print(" (see the transcript file)"); + selector=term_and_log; + } + +@* Dumping and undumping the tables. +After \.{INITEX} has seen a collection of fonts and macros, it +can write all the necessary information on an auxiliary file so +that production versions of \TeX\ are able to initialize their +memory at high speed. The present section of the program takes +care of such output and input. We shall consider simultaneously +the processes of storing and restoring, +so that the inverse relation between them is clear. +@.INITEX@> + +The global variable |format_ident| is a string that is printed right +after the |banner| line when \TeX\ is ready to start. For \.{INITEX} this +string says simply `\.{ (INITEX)}'; for other versions of \TeX\ it says, +for example, `\.{ (preloaded format=plain 1982.11.19)}', showing the year, +month, and day that the format file was created. We have |format_ident==0| +before \TeX's tables are loaded. + +@<Glob...@>= +static str_number @!format_ident, frozen_format_ident; + +@ @<Set init...@>= +format_ident=frozen_format_ident=0; + +@ We keep a copy of the initial value, be able to test for it later. + +@<Initialize table entries...@>= +format_ident=frozen_format_ident=s_no(" (INITEX)"); + +@ @<Declare act...@>= +#ifdef @!INIT +static void store_fmt_file(void) +{@+ +int j, @!k, @!l; /*all-purpose indices*/ +int @!p, @!q; /*all-purpose pointers*/ +int @!x; /*something to dump*/ +four_quarters @!w; /*four ASCII codes*/ +@<If dumping is not allowed, abort@>; +@<Create the |format_ident|, open the format file, and inform the user that +dumping has begun@>; +@<Dump constants for consistency check@>; +@<Dump the string pool@>; +@<Dump the dynamic memory@>; +@<Dump the table of equivalents@>; +@<Dump the font information@>; +@<Dump the hyphenation tables@>; +@<Dump the full file names@>; +@<Dump the file and line information@>; +@<Dump a couple more things and the closing check word@>; +@<Close the format file@>; +} +#endif + +@ Corresponding to the procedure that dumps a format file, we have a function +that reads one in. The function returns |false| if the dumped format is +incompatible with the present \TeX\ table sizes, etc. + +@d too_small(X) {@+wake_up_terminal; + wterm_ln("---! Must increase the %s", X); +@.Must increase the x@> + goto bad_fmt; + } + +@p @t\4@>@<Declare the function called |open_fmt_file|@>@; +static bool load_fmt_file(void) +{@+ +int j, @!k; /*all-purpose indices*/ +int @!p, @!q; /*all-purpose pointers*/ +int @!x; /*something undumped*/ +four_quarters @!w; /*four ASCII codes*/ +@<Undump constants for consistency check@>; +@<Undump the string pool@>; +@<Undump the dynamic memory@>; +@<Undump the table of equivalents@>; +@<Undump the font information@>; +@<Undump the hyphenation tables@>; +@<Undump the full file names@>; +@<Undump the file and line information@>; +@<Undump a couple more things and the closing check word@>; +return true; /*it worked!*/ +bad_fmt: wake_up_terminal; + wterm_ln("(Fatal format file error; I'm stymied)"); +@.Fatal format file error@> +return false; +} + +@ The user is not allowed to dump a format file unless |save_ptr==0|. +This condition implies that |cur_level==level_one|, hence +the |xeq_level| array is constant and it need not be dumped. + +@<If dumping is not allowed, abort@>= +if (save_ptr!=0) + {@+print_err("You can't dump inside a group"); +@.You can't dump...@> + help1("`{...\\dump}' is a no-no.");succumb; + } + +@ Format files consist of |memory_word| items, and we use the following +macros to dump words of different types: + +@d dump_wd(A) {@+fmt_file.d=A;put(fmt_file);@+} +@d dump_int(A) {@+fmt_file.d.i=A;put(fmt_file);@+} +@d dump_hh(A) {@+fmt_file.d.hh=A;put(fmt_file);@+} +@d dump_qqqq(A) {@+fmt_file.d.qqqq=A;put(fmt_file);@+} + +@<Glob...@>= +static word_file @!fmt_file; /*for input or output of format information*/ + +@ The inverse macros are slightly more complicated, since we need to check +the range of the values we are reading in. We say `|undump(a)(b)(x)|' to +read an integer value |x| that is supposed to be in the range |a <= x <= b|. +System error messages should be suppressed when undumping. +@^system dependencies@> + +@d undump_wd(A) {@+get(fmt_file);A=fmt_file.d;@+} +@d undump_int(A) {@+get(fmt_file);A=fmt_file.d.i;@+} +@d undump_hh(A) {@+get(fmt_file);A=fmt_file.d.hh;@+} +@d undump_qqqq(A) {@+get(fmt_file);A=fmt_file.d.qqqq;@+} +@d undump(A, B, C) {@+undump_int(x);if ((x < A)||(x > B)) goto bad_fmt;@+else C=x;@+} +@d undump_size(A, B, C, D) {@+undump_int(x); + if (x < A) goto bad_fmt;if (x > B) too_small(C)@;@+else D=x;@+} + +@ The next few sections of the program should make it clear how we use the +dump/undump macros. + +@<Dump constants for consistency check@>= +dump_int(0);@/ +@<Dump the \eTeX\ state@>@/ +@<Dump the \Prote\ state@>@/ +@<Dump the |ROM| array@>@/ +dump_int(mem_bot);@/ +dump_int(mem_top);@/ +dump_int(eqtb_size);@/ +dump_int(hash_prime);@/ +dump_int(hyph_size) + +@ Sections of a \.{WEB} program that are ``commented out'' still contribute +strings to the string pool; therefore \.{INITEX} and \TeX\ will have +the same strings. (And it is, of course, a good thing that they do.) +@.WEB@> +@^string pool@> + +@<Undump constants for consistency check@>= +x=fmt_file.d.i; +if (x!=0) goto bad_fmt; /*check that strings are the same*/ +@/@<Undump the \eTeX\ state@>@/ +@/@<Undump the \Prote\ state@>@/ +@/@<Undump the |ROM| array@>@/ +undump_int(x); +if (x!=mem_bot) goto bad_fmt; +undump_int(x); +if (x!=mem_top) goto bad_fmt; +undump_int(x); +if (x!=eqtb_size) goto bad_fmt; +undump_int(x); +if (x!=hash_prime) goto bad_fmt; +undump_int(x); +if (x!=hyph_size) goto bad_fmt + +@ @d dump_four_ASCII + w.b0=qi(so(str_pool[k]));w.b1=qi(so(str_pool[k+1])); + w.b2=qi(so(str_pool[k+2]));w.b3=qi(so(str_pool[k+3])); + dump_qqqq(w) + +@<Dump the string pool@>= +dump_int(pool_ptr); +dump_int(str_ptr); +for (k=0; k<=str_ptr; k++) dump_int(str_start[k]); +k=0; +while (k+4 < pool_ptr) + {@+dump_four_ASCII;k=k+4; + } +k=pool_ptr-4;dump_four_ASCII; +print_ln();print_int(str_ptr);print(" strings of total length "); +print_int(pool_ptr) + +@ @d undump_four_ASCII + undump_qqqq(w); + str_pool[k]=si(qo(w.b0));str_pool[k+1]=si(qo(w.b1)); + str_pool[k+2]=si(qo(w.b2));str_pool[k+3]=si(qo(w.b3)) + +@<Undump the string pool@>= +undump_size(0, pool_size,"string pool size", pool_ptr); +undump_size(0, max_strings,"max strings", str_ptr); +for (k=0; k<=str_ptr; k++) undump(0, pool_ptr, str_start[k]); +k=0; +while (k+4 < pool_ptr) + {@+undump_four_ASCII;k=k+4; + } +k=pool_ptr-4;undump_four_ASCII; +init_str_ptr=str_ptr;init_pool_ptr=pool_ptr + +@ By sorting the list of available spaces in the variable-size portion of +|mem|, we are usually able to get by without having to dump very much +of the dynamic memory. + +We recompute |var_used| and |dyn_used|, so that \.{INITEX} dumps valid +information even when it has not been gathering statistics. + +@<Dump the dynamic memory@>= +sort_avail();var_used=0; +dump_int(lo_mem_max);dump_int(rover); +if (eTeX_ex) for (k=int_val; k<=tok_val; k++) dump_int(sa_root[k]); +p=mem_bot;q=rover;x=0; +@/do@+{for (k=p; k<=q+1; k++) dump_wd(mem[k]); +x=x+q+2-p;var_used=var_used+q-p; +p=q+node_size(q);q=rlink(q); +}@+ while (!(q==rover)); +var_used=var_used+lo_mem_max-p;dyn_used=mem_end+1-hi_mem_min;@/ +for (k=p; k<=lo_mem_max; k++) dump_wd(mem[k]); +x=x+lo_mem_max+1-p; +dump_int(hi_mem_min);dump_int(avail); +for (k=hi_mem_min; k<=mem_end; k++) dump_wd(mem[k]); +p=avail; +while (p!=null) +{@+fl_mem[p]=0; /*clear unallocated |fl_mem|*/ + decr(dyn_used);p=link(p); +} +dump_int(var_used);dump_int(dyn_used); +print_ln();print_int(x);print_char('&');print_int(mem_end+1-hi_mem_min); +print(" memory locations dumped; current usage is "); +print_int(var_used);print_char('&');print_int(dyn_used) + +@ @<Undump the dynamic memory@>= +undump(lo_mem_stat_max+1000, hi_mem_stat_min-1, lo_mem_max); +undump(lo_mem_stat_max+1, lo_mem_max, rover); +if (eTeX_ex) for (k=int_val; k<=tok_val; k++) + undump(null, lo_mem_max, sa_root[k]); +p=mem_bot;q=rover; +@/do@+{for (k=p; k<=q+1; k++) undump_wd(mem[k]); +p=q+node_size(q); +if ((p > lo_mem_max)||((q >= rlink(q))&&(rlink(q)!=rover))) goto bad_fmt; +q=rlink(q); +}@+ while (!(q==rover)); +for (k=p; k<=lo_mem_max; k++) undump_wd(mem[k]); +if (mem_min < mem_bot-2) /*make more low memory available*/ + {@+p=llink(rover);q=mem_min+1; + link(mem_min)=null;info(mem_min)=null; /*we don't use the bottom word*/ + rlink(p)=q;llink(rover)=q;@/ + rlink(q)=rover;llink(q)=p;link(q)=empty_flag; + node_size(q)=mem_bot-q; + } +undump(lo_mem_max+1, hi_mem_stat_min, hi_mem_min); +undump(null, mem_top, avail);mem_end=mem_top; +for (k=hi_mem_min; k<=mem_end; k++) undump_wd(mem[k]); +undump_int(var_used);undump_int(dyn_used) + +@ @<Dump the table of equivalents@>= +@<Dump regions 1 to 4 of |eqtb|@>; +@<Dump regions 5 and 6 of |eqtb|@>; +dump_int(par_loc);dump_int(write_loc);@/ +dump_int(input_loc);@/ +@<Dump the hash table@>@; + +@ @<Undump the table of equivalents@>= +@<Undump regions 1 to 6 of |eqtb|@>; +undump(hash_base, frozen_control_sequence, par_loc); +par_token=cs_token_flag+par_loc;@/ +undump(hash_base, frozen_control_sequence, write_loc);@/ +undump(hash_base, frozen_control_sequence, input_loc); +input_token=cs_token_flag+input_loc;@/ +@<Undump the hash table@>@; + +@ The table of equivalents usually contains repeated information, so we dump it +in compressed form: The sequence of $n+2$ values $(n,x_1,\ldots,x_n,m)$ in the +format file represents $n+m$ consecutive entries of |eqtb|, with |m| extra +copies of $x_n$, namely $(x_1,\ldots,x_n,x_n,\ldots,x_n)$. + +@<Dump regions 1 to 4 of |eqtb|@>= +k=active_base; +@/do@+{j=k; +while (j < int_base-1) + {@+if ((equiv(j)==equiv(j+1))&&(eq_type(j)==eq_type(j+1))&&@| + (eq_level(j)==eq_level(j+1))) goto found1; + incr(j); + } +l=int_base;goto done1; /*|j==int_base-1|*/ +found1: incr(j);l=j; +while (j < int_base-1) + {@+if ((equiv(j)!=equiv(j+1))||(eq_type(j)!=eq_type(j+1))||@| + (eq_level(j)!=eq_level(j+1))) goto done1; + incr(j); + } +done1: dump_int(l-k); +while (k < l) + {@+dump_wd(eqtb[k]);incr(k); + } +k=j+1;dump_int(k-l); +}@+ while (!(k==int_base)) + +@ @<Dump regions 5 and 6 of |eqtb|@>= +@/do@+{j=k; +while (j < eqtb_size) + {@+if (eqtb[j].i==eqtb[j+1].i) goto found2; + incr(j); + } +l=eqtb_size+1;goto done2; /*|j==eqtb_size|*/ +found2: incr(j);l=j; +while (j < eqtb_size) + {@+if (eqtb[j].i!=eqtb[j+1].i) goto done2; + incr(j); + } +done2: dump_int(l-k); +while (k < l) + {@+dump_wd(eqtb[k]);incr(k); + } +k=j+1;dump_int(k-l); +}@+ while (!(k > eqtb_size)) + +@ @<Undump regions 1 to 6 of |eqtb|@>= +k=active_base; +@/do@+{undump_int(x); +if ((x < 1)||(k+x > eqtb_size+1)) goto bad_fmt; +for (j=k; j<=k+x-1; j++) undump_wd(eqtb[j]); +k=k+x; +undump_int(x); +if ((x < 0)||(k+x > eqtb_size+1)) goto bad_fmt; +for (j=k; j<=k+x-1; j++) eqtb[j]=eqtb[k-1]; +k=k+x; +}@+ while (!(k > eqtb_size)) + +@ A different scheme is used to compress the hash table, since its lower +region is usually sparse. When |text(p)!=0| for |p <= hash_used|, we output +two words, |p| and |hash[p]|. The hash table is, of course, densely packed +for |p >= hash_used|, so the remaining entries are output in a~block. + +@<Dump the hash table@>= +dump_int(hash_used);cs_count=frozen_control_sequence-1-hash_used; +for (p=hash_base; p<=hash_used; p++) if (text(p)!=0) + {@+dump_int(p);dump_hh(hash[p]);incr(cs_count); + } +for (p=hash_used+1; p<=undefined_control_sequence-1; p++) dump_hh(hash[p]); +dump_int(cs_count);@/ +print_ln();print_int(cs_count);print(" multiletter control sequences") + +@ @<Undump the hash table@>= +undump(hash_base, frozen_control_sequence, hash_used);p=hash_base-1; +@/do@+{undump(p+1, hash_used, p);undump_hh(hash[p]); +}@+ while (!(p==hash_used)); +for (p=hash_used+1; p<=undefined_control_sequence-1; p++) undump_hh(hash[p]); +undump_int(cs_count) + +@ @<Dump the font information@>= +dump_int(fmem_ptr); +for (k=0; k<=fmem_ptr-1; k++) dump_wd(font_info[k]); +dump_int(font_ptr); +for (k=null_font; k<=font_ptr; k++) + @<Dump the array info for internal font number |k|@>; +print_ln();print_int(fmem_ptr-7);print(" words of font info for "); +print_int(font_ptr-font_base);print(" preloaded font"); +if (font_ptr!=font_base+1) print_char('s') + +@ @<Undump the font information@>= +undump_size(7, font_mem_size,"font mem size", fmem_ptr); +for (k=0; k<=fmem_ptr-1; k++) undump_wd(font_info[k]); +undump_size(font_base, font_max,"font max", font_ptr); +for (k=null_font; k<=font_ptr; k++) + @<Undump the array info for internal font number |k|@>@; + +@ @<Dump the array info for internal font number |k|@>= +{@+dump_qqqq(font_check[k]); +dump_int(font_size[k]); +dump_int(font_dsize[k]); +dump_int(font_params[k]);@/ +dump_int(hyphen_char[k]); +dump_int(skew_char[k]);@/ +dump_int(font_name[k]); +dump_int(font_area[k]);@/ +dump_int(font_bc[k]); +dump_int(font_ec[k]);@/ +dump_int(char_base[k]); +dump_int(width_base[k]); +dump_int(height_base[k]);@/ +dump_int(depth_base[k]); +dump_int(italic_base[k]); +dump_int(lig_kern_base[k]);@/ +dump_int(kern_base[k]); +dump_int(exten_base[k]); +dump_int(param_base[k]);@/ +dump_int(font_glue[k]);@/ +dump_int(bchar_label[k]); +dump_int(font_bchar[k]); +dump_int(font_false_bchar[k]);@/ +print_nl("\\font");printn_esc(font_id_text(k));print_char('='); +print_file_name(font_name[k], font_area[k],empty_string); +if (font_size[k]!=font_dsize[k]) + {@+print(" at ");print_scaled(font_size[k]);print("pt"); + } +} + +@ @<Undump the array info for internal font number |k|@>= +{@+undump_qqqq(font_check[k]);@/ +undump_int(font_size[k]); +undump_int(font_dsize[k]); +undump(min_halfword, max_halfword, font_params[k]);@/ +undump_int(hyphen_char[k]); +undump_int(skew_char[k]);@/ +undump(0, str_ptr, font_name[k]); +undump(0, str_ptr, font_area[k]);@/ +undump(0, 255, font_bc[k]); +undump(0, 255, font_ec[k]);@/ +undump_int(char_base[k]); +undump_int(width_base[k]); +undump_int(height_base[k]);@/ +undump_int(depth_base[k]); +undump_int(italic_base[k]); +undump_int(lig_kern_base[k]);@/ +undump_int(kern_base[k]); +undump_int(exten_base[k]); +undump_int(param_base[k]);@/ +undump(min_halfword, lo_mem_max, font_glue[k]);@/ +undump(0, fmem_ptr-1, bchar_label[k]); +undump(min_quarterword, non_char, font_bchar[k]); +undump(min_quarterword, non_char, font_false_bchar[k]); +} + +@ @<Dump the hyphenation tables@>= +dump_int(hyph_count); +for (k=0; k<=hyph_size; k++) if (hyph_word[k]!=0) + {@+dump_int(k);dump_int(hyph_word[k]);dump_int(hyph_list[k]); + } +print_ln();print_int(hyph_count);print(" hyphenation exception"); +if (hyph_count!=1) print_char('s'); +if (trie_not_ready) init_trie(); +dump_int(trie_max); +dump_int(hyph_start); +for (k=0; k<=trie_max; k++) dump_hh(trie[k]); +dump_int(trie_op_ptr); +for (k=1; k<=trie_op_ptr; k++) + {@+dump_int(hyf_distance[k]); + dump_int(hyf_num[k]); + dump_int(hyf_next[k]); + } +print_nl("Hyphenation trie of length ");print_int(trie_max); +@.Hyphenation trie...@> +print(" has ");print_int(trie_op_ptr);print(" op"); +if (trie_op_ptr!=1) print_char('s'); +print(" out of ");print_int(trie_op_size); +for (k=255; k>=0; k--) if (trie_used[k] > min_quarterword) + {@+print_nl(" ");print_int(qo(trie_used[k])); + print(" for language ");print_int(k); + dump_int(k);dump_int(qo(trie_used[k])); + } + +@ Only ``nonempty'' parts of |op_start| need to be restored. + +@<Undump the hyphenation tables@>= +undump(0, hyph_size, hyph_count); +for (k=1; k<=hyph_count; k++) + {@+undump(0, hyph_size, j); + undump(0, str_ptr, hyph_word[j]); + undump(min_halfword, max_halfword, hyph_list[j]); + } +undump_size(0, trie_size,"trie size", j); +#ifdef @!INIT +trie_max=j; +#endif +undump(0, j, hyph_start); +for (k=0; k<=j; k++) undump_hh(trie[k]); +undump_size(0, trie_op_size,"trie op size", j); +#ifdef @!INIT +trie_op_ptr=j; +#endif +for (k=1; k<=j; k++) + {@+undump(0, 63, hyf_distance[k]); /*a |small_number|*/ + undump(0, 63, hyf_num[k]); + undump(min_quarterword, max_quarterword, hyf_next[k]); + } +#ifdef @!INIT +for (k=0; k<=255; k++) trie_used[k]=min_quarterword; +#endif +@;@/ +k=256; +while (j > 0) + {@+undump(0, k-1, k);undump(1, j, x); +#ifdef @!INIT +trie_used[k]=qi(x); +#endif +@;@/ + j=j-x;op_start[k]=qo(j); + } +#ifdef @!INIT +trie_not_ready=false +#endif + +@ We have already printed a lot of statistics, so we set |tracing_stats=0| +to prevent them from appearing again. + +@<Dump a couple more things and the closing check word@>= +dump_int(interaction);dump_int(format_ident);dump_int(69069); +tracing_stats=0 + +@ @<Undump a couple more things and the closing check word@>= +undump(batch_mode, error_stop_mode, interaction); +if (interaction_option>=0) interaction=interaction_option; /* \TeX\ Live */ +undump(0, str_ptr, format_ident); +undump_int(x); +if ((x!=69069)||eof(fmt_file)) goto bad_fmt + +@ @<Create the |format_ident|...@>= +selector=new_string; +print(" (preloaded format=");printn(job_name);print_char(' '); +print_int(year);print_char('.'); +print_int(month);print_char('.');print_int(day);print_char(')'); +if (interaction==batch_mode) selector=log_only; +else selector=term_and_log; +str_room(1); +format_ident=make_string(); +pack_job_name(format_extension); +while (!w_open_out(&fmt_file)) + prompt_file_name("format file name", format_extension); +print_nl("Beginning to dump on file "); +@.Beginning to dump...@> +slow_print(w_make_name_string(&fmt_file));flush_string; +print_nl("");slow_print(format_ident) + +@ @<Close the format file@>= +w_close(&fmt_file) + +@* The main program. +This is it: the part of \TeX\ that executes all those procedures we have +written. + +Well---almost. Let's leave space for a few more routines that we may +have forgotten. + +@p @<Last-minute procedures@>@; + +@ We have noted that there are two versions of \TeX82. One, called \.{INITEX}, +@.INITEX@> +has to be run first; it initializes everything from scratch, without +reading a format file, and it has the capability of dumping a format file. +The other one is called `\.{VIRTEX}'; it is a ``virgin'' program that needs +@.VIRTEX@> +to input a format file in order to get started. \.{VIRTEX} typically has +more memory capacity than \.{INITEX}, because it does not need the space +consumed by the auxiliary hyphenation tables and the numerous calls on +|primitive|, etc. + +The \.{VIRTEX} program cannot read a format file instantaneously, of course; +the best implementations therefore allow for production versions of \TeX\ that +not only avoid the loading routine for \PASCAL\ object code, they also have +a format file pre-loaded. This is impossible to do if we stick to standard +\PASCAL; but there is a simple way to fool many systems into avoiding the +initialization, as follows:\quad(1)~We declare a global integer variable +called |ready_already|. The probability is negligible that this +variable holds any particular value like 314159 when \.{VIRTEX} is first +loaded.\quad(2)~After we have read in a format file and initialized +everything, we set |ready_already=314159|.\quad(3)~Soon \.{VIRTEX} +will print `\.*', waiting for more input; and at this point we +interrupt the program and save its core image in some form that the +operating system can reload speedily.\quad(4)~When that core image is +activated, the program starts again at the beginning; but now +|ready_already==314159| and all the other global variables have +their initial values too. The former chastity has vanished! + +In other words, if we allow ourselves to test the condition +|ready_already==314159|, before |ready_already| has been +assigned a value, we can avoid the lengthy initialization. Dirty tricks +rarely pay off so handsomely. +@^dirty \PASCAL@> +@^system dependencies@> + +On systems that allow such preloading, the standard program called \.{TeX} +should be the one that has \.{plain} format preloaded, since that agrees +with {\sl The \TeX book}. Other versions, e.g., \.{AmSTeX}, should also +@:TeXbook}{\sl The \TeX book@> +@.AmSTeX@> +@.plain@> +be provided for commonly used formats. + +@<Glob...@>= +static int @!ready_already; /*a sacrifice of purity for economy*/ + +@ Now this is really it: \TeX\ starts and ends here. + +The initial test involving |ready_already| should be deleted if the +\PASCAL\ runtime system is smart enough to detect such a ``mistake.'' +@^system dependencies@> + +@p +int main(int argc, char *argv[]) {@! /*|start_here|*/ + main_init(argc, argv); /* \TeX\ Live */ +history=fatal_error_stop; /*in case we quit during initialization*/ +t_open_out; /*open the terminal for output*/ +if (ready_already==314159) goto start_of_TEX; +@<Check the ``constant'' values...@>@; +if (bad > 0) + {@+wterm_ln("Ouch---my internal constants have been clobbered!" + "---case %d", bad); +@.Ouch...clobbered@> + exit(0); + } +get_strings_started(); +initialize(); /*set global variables to their starting values*/ +#ifdef @!INIT +if (iniversion) /* \TeX\ Live */ +{ init_prim(); /*call |primitive| for each primitive*/ + init_str_ptr=str_ptr;init_pool_ptr=pool_ptr;fix_date_and_time(); } +#endif +ready_already=314159; +start_of_TEX: @<Initialize the output routines@>; +@<Get the first line of input and prepare to start@>; +history=spotless; /*ready to go!*/ +main_control(); /*come to life*/ +final_cleanup(); /*prepare for death*/ +close_files_and_terminate(); +ready_already=0; +return 0; } + +@ Here we do whatever is needed to complete \TeX's job gracefully on the +local operating system. The code here might come into play after a fatal +error; it must therefore consist entirely of ``safe'' operations that +cannot produce error messages. For example, it would be a mistake to call +|str_room| or |make_string| at this time, because a call on |overflow| +might lead to an infinite loop. +@^system dependencies@> +(Actually there's one way to get error messages, via |prepare_mag|; +but that can't cause infinite recursion.) +@^recursion@> + +If |final_cleanup| is bypassed, this program doesn't bother to close +the input files that may still be open. + +@<Last-minute...@>= +static void close_files_and_terminate(void) +{@+int k; /*all-purpose index*/ +@<Finish the extensions@>;new_line_char=-1; +#ifdef @!STAT +if (tracing_stats > 0) @<Output statistics about this job@>;@; +#endif +wake_up_terminal;@<Finish the \.{DVI} file@>; +if (log_opened) + {@+wlog_cr;a_close(&log_file);selector=selector-2; + if (selector==term_only) + {@+print_nl("Transcript written on "); +@.Transcript written...@> + slow_print(log_name);print_char('.');print_nl(""); + } + } +} + +@ The present section goes directly to the log file instead of using +|print| commands, because there's no need for these strings to take +up |str_pool| memory when a non-{\bf stat} version of \TeX\ is being used. + +@<Output statistics...@>= +if (log_opened) + {@+wlog_ln(" "); + wlog_ln("Here is how much of TeX's memory you used:"); +@.Here is how much...@> + wlog(" %d string", str_ptr-init_str_ptr); + if (str_ptr!=init_str_ptr+1) wlog( "s" ); + wlog_ln( " out of %d", max_strings-init_str_ptr);@/ + wlog_ln( " %d string characters out of %d", pool_ptr-init_pool_ptr, + pool_size-init_pool_ptr);@/ + wlog_ln(" %d words of memory out of %d", lo_mem_max-mem_min+mem_end-hi_mem_min+2,@| + mem_end+1-mem_min);@/ + wlog_ln(" %d multiletter control sequences out of %d", cs_count, hash_size);@/ + wlog(" %d words of font info for %d font", fmem_ptr, font_ptr-font_base); + if (font_ptr!=font_base+1) wlog("s"); + wlog_ln( ", out of %d for %d", font_mem_size, font_max-font_base);@/ + wlog(" %d hyphenation exception", hyph_count); + if (hyph_count!=1) wlog("s"); + wlog_ln( " out of %d", hyph_size);@/ + wlog_ln(" %di,%dn,%dp,%db,%ds stack positions out of %di,%dn,%dp,%db,%ds", + max_in_stack, max_nest_stack,@| + max_param_stack,@| + max_buf_stack+1,@| + max_save_stack+6,@| + stack_size, + nest_size, + param_size, + buf_size, + save_size ); + } + +@ We get to the |final_cleanup| routine when \.{\\end} or \.{\\dump} has +been scanned and |its_all_over|\kern-2pt. + +@<Last-minute...@>= +static void final_cleanup(void) +{@+ +int c; /*0 for \.{\\end}, 1 for \.{\\dump}*/ +c=cur_chr;if (c!=1) new_line_char=-1; +if (job_name==0) open_log_file(); +while (input_ptr > 0) + if (state==token_list) end_token_list();@+else end_file_reading(); +while (open_parens > 0) + {@+print(" )");decr(open_parens); + } +if (cur_level > level_one) + {@+print_nl("(");print_esc("end occurred "); + print("inside a group at level "); +@:end\_}{\.{(\\end occurred...)}@> + print_int(cur_level-level_one);print_char(')'); + if (eTeX_ex) show_save_groups(); + } +while (cond_ptr!=null) + {@+print_nl("(");print_esc("end occurred "); + print("when ");print_cmd_chr(if_test, cur_if); + if (if_line!=0) + {@+print(" on line ");print_int(if_line); + } + print(" was incomplete)"); + if_line=if_line_field(cond_ptr); + cur_if=subtype(cond_ptr);temp_ptr=cond_ptr; + cond_ptr=link(cond_ptr);free_node(temp_ptr, if_node_size); + } +if (history!=spotless) + if (((history==warning_issued)||(interaction < error_stop_mode))) + if (selector==term_and_log) + {@+selector=term_only; + print_nl("(see the transcript file for additional information)"); +@.see the transcript file...@> + selector=term_and_log; + } +if (c==1) + { +#ifdef @!INIT +for (c=top_mark_code; c<=split_bot_mark_code; c++) + if (cur_mark[c]!=null) delete_token_ref(cur_mark[c]); + if (sa_mark!=null) + if (do_marks(destroy_marks, 0, sa_mark)) sa_mark=null; + for (c=last_box_code; c<=vsplit_code; c++) flush_node_list(disc_ptr[c]); + if (last_glue!=max_halfword) delete_glue_ref(last_glue); + store_fmt_file();return; +#endif + print_nl("(\\dump is performed only by INITEX)");return; +@:dump\_}{\.{\\dump...only by INITEX}@> + } +} + +@ @<Last-minute...@>= +#ifdef @!INIT +static void init_prim(void) /*initialize all the primitives*/ +{@+no_new_control_sequence=false; +first=0; +@<Put each...@>; +no_new_control_sequence=true; +} +#endif + +@ When we begin the following code, \TeX's tables may still contain garbage; +the strings might not even be present. Thus we must proceed cautiously to get +bootstrapped in. + +But when we finish this part of the program, \TeX\ is ready to call on the +|main_control| routine to do its work. + +@<Get the first line...@>= +{@+@<Initialize the input routines@>; +@<Enable \eTeX\ and furthermore Prote, if requested@>@;@/ +if ((format_ident==0)||(buffer[loc]=='&')) + {@+if (format_ident!=0) initialize(); /*erase preloaded format*/ + if (!open_fmt_file()) exit(0); + if (!load_fmt_file()) + {@+w_close(&fmt_file);exit(0); + } + w_close(&fmt_file); + while ((loc < limit)&&(buffer[loc]==' ')) incr(loc); + } +if (eTeX_ex) wterm_ln("entering extended mode"); +if (Prote_ex) {@+Prote_initialize(); + } +if (end_line_char_inactive) decr(limit); +else buffer[limit]=end_line_char; +fix_date_and_time();@/ +@<Initialize the print |selector|...@>; +if ((loc < limit)&&(cat_code(buffer[loc])!=escape)) start_input(); + /*\.{\\input} assumed*/ +} + +@* Debugging. +Once \TeX\ is working, you should be able to diagnose most errors with +the \.{\\show} commands and other diagnostic features. But for the initial +stages of debugging, and for the revelation of really deep mysteries, you +can compile \TeX\ with a few more aids, including the \PASCAL\ runtime +checks and its debugger. An additional routine called |debug_help| +will also come into play when you type `\.D' after an error message; +|debug_help| also occurs just before a fatal error causes \TeX\ to succumb. +@^debugging@> +@^system dependencies@> + +The interface to |debug_help| is primitive, but it is good enough when used +with a \PASCAL\ debugger that allows you to set breakpoints and to read +variables and change their values. After getting the prompt `\.{debug \#}', you +type either a negative number (this exits |debug_help|), or zero (this +goes to a location where you can set a breakpoint, thereby entering into +dialog with the \PASCAL\ debugger), or a positive number |m| followed by +an argument |n|. The meaning of |m| and |n| will be clear from the +program below. (If |m==13|, there is an additional argument, |l|.) +@.debug \#@> + +@<Last-minute...@>= +#ifdef @!DEBUG +static void debug_help(void) /*routine to display various things*/ +{@+ +int k, @!l, @!m, @!n; +clear_terminal; + loop{@+wake_up_terminal; + print_nl("debug # (-1 to exit):");update_terminal; +@.debug \#@> + if (fscanf(term_in.f," %d",&m)<1 || + m < 0) return; + else if (m==0) + {@+goto breakpoint;@/ /*go to every declared label at least once*/ + breakpoint: m=0; /*'BREAKPOINT'*/@/ + } + else{@+fscanf(term_in.f," %d",&n); + switch (m) { + @t\4@>@<Numbered cases for |debug_help|@>@; + default:print("?"); + } + } + } +} +#endif + +@ @<Numbered cases...@>= +case 1: print_word(mem[n]);@+break; /*display |mem[n]| in all forms*/ +case 2: print_int(info(n));@+break; +case 3: print_int(link(n));@+break; +case 4: print_word(eqtb[n]);@+break; +case 5: print_word(font_info[n]);@+break; +case 6: print_word(save_stack[n]);@+break; +case 7: show_box(n);@+break; + /*show a box, abbreviated by |show_box_depth| and |show_box_breadth|*/ +case 8: {@+breadth_max=10000;depth_threshold=pool_size-pool_ptr-10; + show_node_list(n); /*show a box in its entirety*/ + } @+break; +case 9: show_token_list(n, null, 1000);@+break; +case 10: slow_print(n);@+break; +case 11: check_mem(n > 0);@+break; /*check wellformedness; print new busy locations if |n > 0|*/ +case 12: search_mem(n);@+break; /*look for pointers to |n|*/ +case 13: {@+fscanf(term_in.f," %d",&l);print_cmd_chr(n, l); + } @+break; +case 14: for (k=0; k<=n; k++) printn(buffer[k]);@+break; +case 15: {@+font_in_short_display=null_font;short_display(n); + } @+break; +case 16: panicking=!panicking;@+break; + +@* Extensions. +The program above includes a bunch of ``hooks'' that allow further +capabilities to be added without upsetting \TeX's basic structure. +Most of these hooks are concerned with ``whatsit'' nodes, which are +intended to be used for special purposes; whenever a new extension to +\TeX\ involves a new kind of whatsit node, a corresponding change needs +to be made to the routines below that deal with such nodes, +but it will usually be unnecessary to make many changes to the +other parts of this program. + +In order to demonstrate how extensions can be made, we shall treat +`\.{\\write}', `\.{\\openout}', `\.{\\closeout}', `\.{\\immediate}', +`\.{\\special}', and `\.{\\setlanguage}' as if they were extensions. +These commands are actually primitives of \TeX, and they should +appear in all implementations of the system; but let's try to imagine +that they aren't. Then the program below illustrates how a person +could add them. + +Sometimes, of course, an extension will require changes to \TeX\ itself; +no system of hooks could be complete enough for all conceivable extensions. +The features associated with `\.{\\write}' are almost all confined to the +following paragraphs, but there are small parts of the |print_ln| and +|print_char| procedures that were introduced specifically to \.{\\write} +characters. Furthermore one of the token lists recognized by the scanner +is a |write_text|; and there are a few other miscellaneous places where we +have already provided for some aspect of \.{\\write}. The goal of a \TeX\ +extender should be to minimize alterations to the standard parts of the +program, and to avoid them completely if possible. He or she should also +be quite sure that there's no easy way to accomplish the desired goals +with the standard features that \TeX\ already has. ``Think thrice before +extending,'' because that may save a lot of work, and it will also keep +incompatible extensions of \TeX\ from proliferating. +@^system dependencies@> +@^extensions to \TeX@> + +@ First let's consider the format of whatsit nodes that are used to represent +the data associated with \.{\\write} and its relatives. Recall that a whatsit +has |type==whatsit_node|, and the |subtype| is supposed to distinguish +different kinds of whatsits. Each node occupies two or more words; the +exact number is immaterial, as long as it is readily determined from the +|subtype| or other data. + +We shall introduce five |subtype| values here, corresponding to the +control sequences \.{\\openout}, \.{\\write}, \.{\\closeout}, \.{\\special}, and +\.{\\setlanguage}. The second word of I/O whatsits has a |write_stream| field +that identifies the write-stream number (0 to 15, or 16 for out-of-range and +positive, or 17 for out-of-range and negative). +In the case of \.{\\write} and \.{\\special}, there is also a field that +points to the reference count of a token list that should be sent. In the +case of \.{\\openout}, we need three words and three auxiliary subfields +to hold the string numbers for name, area, and extension. + +@d write_node_size 2 /*number of words in a write/whatsit node*/ +@d open_node_size 3 /*number of words in an open/whatsit node*/ +@d open_node 0 /*|subtype| in whatsits that represent files to \.{\\openout}*/ +@d write_node 1 /*|subtype| in whatsits that represent things to \.{\\write}*/ +@d close_node 2 /*|subtype| in whatsits that represent streams to \.{\\closeout}*/ +@d special_node 3 /*|subtype| in whatsits that represent \.{\\special} things*/ +@d language_node 4 /*|subtype| in whatsits that change the current language*/ +@d what_lang(A) link(A+1) /*language number, in the range |0 dotdot 255|*/ +@d what_lhm(A) type(A+1) /*minimum left fragment, in the range |1 dotdot 63|*/ +@d what_rhm(A) subtype(A+1) /*minimum right fragment, in the range |1 dotdot 63|*/ +@d write_tokens(A) link(A+1) /*reference count of token list to write*/ +@d write_stream(A) info(A+1) /*stream number (0 to 17)*/ +@d open_name(A) link(A+1) /*string number of file name to open*/ +@d open_area(A) info(A+2) /*string number of file area for |open_name|*/ +@d open_ext(A) link(A+2) /*string number of file extension for |open_name|*/ + +@ The sixteen possible \.{\\write} streams are represented by the |write_file| +array. The |j|th file is open if and only if |write_open[j]==true|. The last +two streams are special; |write_open[16]| represents a stream number +greater than 15, while |write_open[17]| represents a negative stream number, +and both of these variables are always |false|. + +@<Glob...@>= +static alpha_file @!write_file[16]; +static bool @!write_open[18]; + +@ @<Set init...@>= +for (k=0; k<=17; k++) write_open[k]=false; + +@ Extensions might introduce new command codes; but it's best to use +|extension| with a modifier, whenever possible, so that |main_control| +stays the same. + +@d immediate_code 4 /*command modifier for \.{\\immediate}*/ +@d latex_first_extension_code 5 +@d latespecial_node (latex_first_extension_code+0) /*|subtype| in whatsits that represent \.{\\special} things expanded during output*/ +@d set_language_code (latex_first_extension_code+1) /*command modifier for \.{\\setlanguage}*/ +@d TeX_last_extension_cmd_mod set_language_code + +@<Put each...@>= +primitive("openout", extension, open_node);@/ +@!@:open\_out\_}{\.{\\openout} primitive@> +primitive("write", extension, write_node);write_loc=cur_val;@/ +@!@:write\_}{\.{\\write} primitive@> +primitive("closeout", extension, close_node);@/ +@!@:close\_out\_}{\.{\\closeout} primitive@> +primitive("special", extension, special_node);@/ +@!@:special\_}{\.{\\special} primitive@> +primitive("immediate", extension, immediate_code);@/ +@!@:immediate\_}{\.{\\immediate} primitive@> +primitive("setlanguage", extension, set_language_code);@/ +@!@:set\_language\_}{\.{\\setlanguage} primitive@> + +@ The variable |write_loc| just introduced is used to provide an +appropriate error message in case of ``runaway'' write texts. + +@<Glob...@>= +static pointer @!write_loc; /*|eqtb| address of \.{\\write}*/ + +@ @<Cases of |print_cmd_chr|...@>= +case extension: switch (chr_code) { + case open_node: print_esc("openout");@+break; + case write_node: print_esc("write");@+break; + case close_node: print_esc("closeout");@+break; + case special_node: print_esc("special");@+break; + case immediate_code: print_esc("immediate");@+break; + case set_language_code: print_esc("setlanguage");@+break; + @/@<Cases of |extension| for |print_cmd_chr|@>@/ + default:print("[unknown extension!]"); + } @+break; + + + +@ When an |extension| command occurs in |main_control|, in any mode, +the |do_extension| routine is called. + +@<Cases of |main_control| that are for extensions...@>= +any_mode(extension): do_extension(); + +@ @<Declare act...@>= +@t\4@>@<Declare procedures needed in |do_extension|@>@; +static void do_extension(void) +{@+int @!k; /*all-purpose integer*/ +pointer @!p; /*all-purpose pointer*/ +switch (cur_chr) { +case open_node: @<Implement \.{\\openout}@>@;@+break; +case write_node: @<Implement \.{\\write}@>@;@+break; +case close_node: @<Implement \.{\\closeout}@>@;@+break; +case special_node: @<Implement \.{\\special}@>@;@+break; +case immediate_code: @<Implement \.{\\immediate}@>@;@+break; +case set_language_code: @<Implement \.{\\setlanguage}@>@;@+break; +@/@<Cases for |do_extension|@>@/ +default:confusion("ext1"); +@:this can't happen ext1}{\quad ext1@> +} +} + +@ Here is a subroutine that creates a whatsit node having a given |subtype| +and a given number of words. It initializes only the first word of the whatsit, +and appends it to the current list. + +@<Declare procedures needed in |do_extension|@>= +static void new_whatsit(small_number @!s, small_number @!w) +{@+pointer p; /*the new node*/ +p=get_node(w);type(p)=whatsit_node;subtype(p)=s; +link(tail)=p;tail=p; +} + +@ The next subroutine uses |cur_chr| to decide what sort of whatsit is +involved, and also inserts a |write_stream| number. + +@<Declare procedures needed in |do_ext...@>= +static void new_write_whatsit(small_number @!w) +{@+new_whatsit(cur_chr, w); +if (w!=write_node_size) scan_four_bit_int(); +else{@+scan_int(); + if (cur_val < 0) cur_val=17; + else if (cur_val > 15) cur_val=16; + } +write_stream(tail)=cur_val; +} + +@ @<Implement \.{\\openout}@>= +{@+new_write_whatsit(open_node_size); +scan_optional_equals();scan_file_name();@/ +open_name(tail)=cur_name;open_area(tail)=cur_area;open_ext(tail)=cur_ext; +} + +@ When `\.{\\write 12\{...\}}' appears, we scan the token list `\.{\{...\}}' +without expanding its macros; the macros will be expanded later when this +token list is rescanned. + +@<Implement \.{\\write}@>= +{@+k=cur_cs;new_write_whatsit(write_node_size);@/ +cur_cs=k;p=scan_toks(false, false);write_tokens(tail)=def_ref; +} + +@ @<Implement \.{\\closeout}@>= +{@+new_write_whatsit(write_node_size);write_tokens(tail)=null; +} + +@ When `\.{\\special\{...\}}' appears, we expand the macros in the token +list as in \.{\\xdef} and \.{\\mark}. When marked with \.{shipout}, we keep +tokens unexpanded for now. + +@<Implement \.{\\special}@>= +{@+if (scan_keyword("shipout")) +{@+new_whatsit(latespecial_node, write_node_size);write_stream(tail)=null; +p=scan_toks(false, false);write_tokens(tail)=def_ref; +} else +{@+new_whatsit(special_node, write_node_size);write_stream(tail)=null; +p=scan_toks(false, true);write_tokens(tail)=def_ref; +} } + +@ Each new type of node that appears in our data structure must be capable +of being displayed, copied, destroyed, and so on. The routines that we +need for write-oriented whatsits are somewhat like those for mark nodes; +other extensions might, of course, involve more subtlety here. + +@<Basic printing...@>= +static void print_write_whatsit(char *@!s, pointer @!p) +{@+print_esc(s); +if (write_stream(p) < 16) print_int(write_stream(p)); +else if (write_stream(p)==16) print_char('*'); +@.*\relax@> +else print_char('-'); +} + +@ @<Display the whatsit...@>= +switch (subtype(p)) { +case open_node: {@+print_write_whatsit("openout", p); + print_char('=');print_file_name(open_name(p), open_area(p), open_ext(p)); + } @+break; +case write_node: {@+print_write_whatsit("write", p); + print_mark(write_tokens(p)); + } @+break; +case close_node: print_write_whatsit("closeout", p);@+break; +case latespecial_node: {@+print_esc("special");print(" shipout"); + print_mark(write_tokens(p)); + } @+break; +case special_node: {@+print_esc("special"); + print_mark(write_tokens(p)); + } @+break; +case language_node: {@+print_esc("setlanguage"); + print_int(what_lang(p));print(" (hyphenmin "); + print_int(what_lhm(p));print_char(','); + print_int(what_rhm(p));print_char(')'); + } @+break; +@/@<Cases for displaying the |whatsit| node@>@/ +default:print("whatsit?"); +} + +@ @<Make a partial copy of the whatsit...@>= +switch (subtype(p)) { +case open_node: {@+r=get_node(open_node_size);words=open_node_size; + } @+break; +case write_node: case special_node: case latespecial_node: {@+r=get_node(write_node_size); + add_token_ref(write_tokens(p));words=write_node_size; + } @+break; +case close_node: case language_node: {@+r=get_node(small_node_size); + words=small_node_size; + } @+break; +@/@<Cases for making a partial copy of the whatsit node@>@/ +default:confusion("ext2"); +@:this can't happen ext2}{\quad ext2@> +} + +@ @<Wipe out the whatsit...@>= +{@+switch (subtype(p)) { +case open_node: free_node(p, open_node_size);@+break; +case write_node: case special_node: case latespecial_node: {@+delete_token_ref(write_tokens(p)); + free_node(p, write_node_size);goto done; + } +case close_node: case language_node: free_node(p, small_node_size);@+break; +@/@<Cases for wiping out the whatsit node@>@/ +default:confusion("ext3"); +@:this can't happen ext3}{\quad ext3@> +} @/ +goto done; +} + +@ @<Incorporate a whatsit node into a vbox@>=do_nothing + +@ @<Incorporate a whatsit node into an hbox@>=do_nothing + +@ @<Let |d| be the width of the whatsit |p|@>=d=0 + +@ @d adv_past(A) @+if (subtype(A)==language_node) + {@+cur_lang=what_lang(A);l_hyf=what_lhm(A);r_hyf=what_rhm(A); + set_hyph_index; + } + +@<Advance \(p)past a whatsit node in the \(l)|line_break| loop@>=@+ +adv_past(cur_p) + +@ @<Advance \(p)past a whatsit node in the \(p)pre-hyphenation loop@>=@+ +adv_past(s) + +@ @<Prepare to move whatsit |p| to the current page, then |goto contribute|@>= +goto contribute + +@ @<Process whatsit |p| in |vert_break| loop, |goto not_found|@>= +goto not_found + +@ @<Output the whatsit node |p| in a vlist@>= +out_what(p) + +@ @<Output the whatsit node |p| in an hlist@>= +out_what(p) + +@ After all this preliminary shuffling, we come finally to the routines +that actually send out the requested data. Let's do \.{\\special} first +(it's easier). + +@<Declare procedures needed in |hlist_out|, |vlist_out|@>= +static void special_out(pointer @!p) +{@+pointer @!q, @!r; /*temporary variables for list manipulation*/ +int @!old_mode; /*saved |mode|*/ + +if (subtype(p)==latespecial_node) + {@+@<Expand macros in the token list and make |link(def_ref)| point to the +result@>; + write_tokens(p)=def_ref; + } +} + +@ To write a token list, we must run it through \TeX's scanner, expanding +macros and \.{\\the} and \.{\\number}, etc. This might cause runaways, +if a delimited macro parameter isn't matched, and runaways would be +extremely confusing since we are calling on \TeX's scanner in the middle +of a \.{\\shipout} command. Therefore we will put a dummy control sequence as +a ``stopper,'' right after the token list. This control sequence is +artificially defined to be \.{\\outer}. +@:end\_write\_}{\.{\\endwrite}@> + +@<Initialize table...@>= +text(end_write)=s_no("endwrite");eq_level(end_write)=level_one; +eq_type(end_write)=outer_call;equiv(end_write)=null; + +@ @<Declare procedures needed in |hlist_out|, |vlist_out|@>= +static void write_out(pointer @!p) +{@+int old_setting; /*holds print |selector|*/ +int @!old_mode; /*saved |mode|*/ +small_number @!j; /*write stream number*/ +pointer @!q, @!r; /*temporary variables for list manipulation*/ +@<Expand macros in the token list and make |link(def_ref)| point to the result@>; +old_setting=selector;j=write_stream(p); +if (write_open[j]) selector=j; +else{@+ /*write to the terminal if file isn't open*/ + if ((j==17)&&(selector==term_and_log)) selector=log_only; + print_nl(""); + } +token_show(def_ref);print_ln(); +flush_list(def_ref);selector=old_setting; +} + +@ The final line of this routine is slightly subtle; at least, the author +didn't think about it until getting burnt! There is a used-up token list +@^Knuth, Donald Ervin@> +on the stack, namely the one that contained |end_write_token|. (We +insert this artificial `\.{\\endwrite}' to prevent runaways, as explained +above.) If it were not removed, and if there were numerous writes on a +single page, the stack would overflow. + +@d end_write_token cs_token_flag+end_write + +@<Expand macros in the token list and...@>= +q=get_avail();info(q)=right_brace_token+'}';@/ +fl_mem[q]=FILE_LINE(system_file,system_insert); +r=get_avail();link(q)=r;info(r)=end_write_token;ins_list(q);@/ +fl_mem[r]=FILE_LINE(system_file,system_insert); +begin_token_list(write_tokens(p), write_text);@/ +q=get_avail();info(q)=left_brace_token+'{';ins_list(q); +fl_mem[q]=FILE_LINE(system_file,system_insert); + + /*now we're ready to scan + `\.\{$\langle\,$token list$\,\rangle$\.{\} \\endwrite}'*/ +old_mode=mode;mode=0; + /*disable \.{\\prevdepth}, \.{\\spacefactor}, \.{\\lastskip}, \.{\\prevgraf}*/ +cur_cs=write_loc;q=scan_toks(false, true); /*expand macros, etc.*/ +get_token();@+if (cur_tok!=end_write_token) + @<Recover from an unbalanced write command@>; +mode=old_mode; +end_token_list() /*conserve stack space*/ + +@ @<Recover from an unbalanced write command@>= +{@+print_err("Unbalanced write command"); +@.Unbalanced write...@> +help2("On this page there's a \\write with fewer real {'s than }'s.",@/ +"I can't handle that very well; good luck.");error(); +@/do@+{get_token(); +}@+ while (!(cur_tok==end_write_token)); +} + +@ The |out_what| procedure takes care of outputting whatsit nodes for +|vlist_out| and |hlist_out|\kern-.3pt. + +@<Declare procedures needed in |hlist_out|, |vlist_out|@>= +@t\4@>@<Declare procedures needed in |out_what|@>@; +static void out_what(pointer @!p) +{@+small_number j; /*write stream number*/ +switch (subtype(p)) { +case open_node: case write_node: case close_node: @<Do some work that has +been queued up for \.{\\write}@>@;@+break; +case special_node: special_out(p);@+break; +case language_node: do_nothing;@+break; +@/@<Cases for |out_what|@>@/ +default:confusion("ext4"); +@:this can't happen ext4}{\quad ext4@> +} +} + +@ We don't implement \.{\\write} inside of leaders. (The reason is that +the number of times a leader box appears might be different in different +implementations, due to machine-dependent rounding in the glue calculations.) +@^leaders@> + +@<Do some work that has been queued up...@>= +if (!doing_leaders) + {@+j=write_stream(p); + if (subtype(p)==write_node) write_out(p); + else{@+if (write_open[j]) a_close(&write_file[j]); + if (subtype(p)==close_node) write_open[j]=false; + else if (j < 16) + {@+cur_name=open_name(p);cur_area=open_area(p); + cur_ext=open_ext(p); + pack_cur_name(".tex"); + while (!a_open_out(&write_file[j])) + prompt_file_name("output file name",".tex"); + write_open[j]=true; + } + } + } + +@ The presence of `\.{\\immediate}' causes the |do_extension| procedure +to descend to one level of recursion. Nothing happens unless \.{\\immediate} +is followed by `\.{\\openout}', `\.{\\write}', or `\.{\\closeout}'. +@^recursion@> + +@<Implement \.{\\immediate}@>= +{@+get_x_token(); +if ((cur_cmd==extension)&&(cur_chr <= close_node)) + {@+p=tail;do_extension(); /*append a whatsit node*/ + out_what(tail); /*do the action immediately*/ + flush_node_list(tail);tail=p;link(p)=null; + } +else back_input(); +} + +@ The \.{\\language} extension is somewhat different. +We need a subroutine that comes into play when a character of +a non-|clang| language is being appended to the current paragraph. + +@<Declare action...@>= +static void fix_language(void) +{@+ASCII_code @!l; /*the new current language*/ +if (language <= 0) l=0; +else if (language > 255) l=0; +else l=language; +if (l!=clang) + {@+new_whatsit(language_node, small_node_size); + what_lang(tail)=l;clang=l;@/ + what_lhm(tail)=norm_min(left_hyphen_min); + what_rhm(tail)=norm_min(right_hyphen_min); + } +} + +@ @<Implement \.{\\setlanguage}@>= +if (abs(mode)!=hmode) report_illegal_case(); +else{@+new_whatsit(language_node, small_node_size); + scan_int(); + if (cur_val <= 0) clang=0; + else if (cur_val > 255) clang=0; + else clang=cur_val; + what_lang(tail)=clang; + what_lhm(tail)=norm_min(left_hyphen_min); + what_rhm(tail)=norm_min(right_hyphen_min); + } + +@ @<Finish the extensions@>= +for (k=0; k<=15; k++) if (write_open[k]) a_close(&write_file[k]); + +@* The extended features of \eTeX. +The program has three modes of operation: (1)~In \TeX\ compatibility mode +it fully deserves the name \TeX\ and there are neither extended features +nor additional primitive commands. There are, however, a few +modifications that would be legitimate in any implementation of \TeX\ +such as, e.g., preventing inadequate results of the glue to \.{DVI} +unit conversion during |ship_out|. (2)~In extended mode there are +additional primitive commands and the extended features of \eTeX\ are +available. (3)~In \Prote\ mode there are supplementary primitive +commands that will be discussed in the section below. + +The distinction between these three modes of operation initially takes +place when a `virgin' \.{eINITEX} starts without reading a format file. +Later on the values of all \eTeX\ state variables are inherited when +\.{eVIRTEX} (or \.{eINITEX}) reads a format file. + +The code below is designed to work for cases where `$|@t\#\&{ifdef} \.{INIT}@>|\ldots|@t\#\&{endif}@>|$' +is a run-time switch. + +@<Enable \eTeX\ and furthermore Prote, if requested@>= +#ifdef @!INIT +if (iniversion && (buffer[loc]=='*'||etexp)) /* \TeX\ Live */ + {@+no_new_control_sequence=false; + @<Generate all \eTeX\ primitives@>@; + if (buffer[loc]=='*') incr(loc); /* \TeX\ Live */ + eTeX_mode=1; /*enter extended mode*/ + @<Initialize variables for \eTeX\ extended mode@>@; + if (buffer[loc]=='*'||ltxp) {@+ + @<Check \Prote\ ``constant'' values for consistency@>@; + @<Generate all \Prote\ primitives@>@; + if (buffer[loc]=='*')incr(loc); + Prote_mode=1; /*enter \Prote\ mode*/ + } + } +#endif +@;@/ +if (!no_new_control_sequence) /*just entered extended mode ?*/ + no_new_control_sequence=true;@+else + +@ The \eTeX\ features available in extended mode are grouped into two +categories: (1)~Some of them are permanently enabled and have no +semantic effect as long as none of the additional primitives are +executed. (2)~The remaining \eTeX\ features are optional and can be +individually enabled and disabled. For each optional feature there is +an \eTeX\ state variable named \.{\\...state}; the feature is enabled, +resp.\ disabled by assigning a positive, resp.\ non-positive value to +that integer. + +@d eTeX_state_base (int_base+eTeX_state_code) +@d eTeX_state(A) eqtb[eTeX_state_base+A].i /*an \eTeX\ state variable*/ +@# +@d eTeX_version_code eTeX_int /*code for \.{\\eTeXversion}*/ + +@<Generate all \eTeX...@>= +primitive("lastnodetype", last_item, last_node_type_code); +@!@:last\_node\_type\_}{\.{\\lastnodetype} primitive@> +primitive("eTeXversion", last_item, eTeX_version_code); +@!@:eTeX\_version\_}{\.{\\eTeXversion} primitive@> +primitive("eTeXrevision", convert, eTeX_revision_code);@/ +@!@:eTeX\_revision\_}{\.{\\eTeXrevision} primitive@> + +@ @<Cases of |last_item| for |print_cmd_chr|@>= +case last_node_type_code: print_esc("lastnodetype");@+break; +case eTeX_version_code: print_esc("eTeXversion");@+break; + +@ @<Cases for fetching an integer value@>= +case eTeX_version_code: cur_val=eTeX_version;@+break; + +@ @d eTeX_ex (eTeX_mode==1) /*is this extended mode?*/ + +@<Glob...@>= +static int @!eTeX_mode; /*identifies compatibility and extended mode*/ + +@ @<Initialize table entries...@>= +eTeX_mode=0; /*initially we are in compatibility mode*/ +@<Initialize variables for \eTeX\ compatibility mode@>@; + +@ @<Dump the \eTeX\ state@>= +dump_int(eTeX_mode); +for (j=0; j<=eTeX_states-1; j++) eTeX_state(j)=0; /*disable all enhancements*/ + +@ @<Undump the \eTeX\ state@>= +undump(0, 1, eTeX_mode); +if (eTeX_ex) + {@+@<Initialize variables for \eTeX\ extended mode@>; + } +else{@+@<Initialize variables for \eTeX\ compatibility mode@>; + } + +@ The |eTeX_enabled| function simply returns its first argument as +result. This argument is |true| if an optional \eTeX\ feature is +currently enabled; otherwise, if the argument is |false|, the function +gives an error message. + +@<Declare \eTeX\ procedures for use...@>= +static bool eTeX_enabled(bool @!b, quarterword @!j, halfword @!k) +{@+if (!b) + {@+print_err("Improper ");print_cmd_chr(j, k); + help1("Sorry, this optional e-TeX feature has been disabled.");error(); + } +return b; +} + +@ First we implement the additional \eTeX\ parameters in the table of +equivalents. + +@<Generate all \eTeX...@>= +primitive("everyeof", assign_toks, every_eof_loc); +@!@:every\_eof\_}{\.{\\everyeof} primitive@> +primitive("tracingassigns", assign_int, int_base+tracing_assigns_code);@/ +@!@:tracing\_assigns\_}{\.{\\tracingassigns} primitive@> +primitive("tracinggroups", assign_int, int_base+tracing_groups_code);@/ +@!@:tracing\_groups\_}{\.{\\tracinggroups} primitive@> +primitive("tracingifs", assign_int, int_base+tracing_ifs_code);@/ +@!@:tracing\_ifs\_}{\.{\\tracingifs} primitive@> +primitive("tracingscantokens", assign_int, int_base+tracing_scan_tokens_code);@/ +@!@:tracing\_scan\_tokens\_}{\.{\\tracingscantokens} primitive@> +primitive("tracingnesting", assign_int, int_base+tracing_nesting_code);@/ +@!@:tracing\_nesting\_}{\.{\\tracingnesting} primitive@> +primitive("savingvdiscards", assign_int, int_base+saving_vdiscards_code);@/ +@!@:saving\_vdiscards\_}{\.{\\savingvdiscards} primitive@> +primitive("savinghyphcodes", assign_int, int_base+saving_hyph_codes_code);@/ +@!@:saving\_hyph\_codes\_}{\.{\\savinghyphcodes} primitive@> + +@ @d every_eof equiv(every_eof_loc) + +@<Cases of |assign_toks| for |print_cmd_chr|@>= +case every_eof_loc: print_esc("everyeof");@+break; + +@ @<Cases for |print_param|@>= +case tracing_assigns_code: print_esc("tracingassigns");@+break; +case tracing_groups_code: print_esc("tracinggroups");@+break; +case tracing_ifs_code: print_esc("tracingifs");@+break; +case tracing_scan_tokens_code: print_esc("tracingscantokens");@+break; +case tracing_nesting_code: print_esc("tracingnesting");@+break; +case saving_vdiscards_code: print_esc("savingvdiscards");@+break; +case saving_hyph_codes_code: print_esc("savinghyphcodes");@+break; + +@ In order to handle \.{\\everyeof} we need an array |eof_seen| of +boolean variables. + +@<Glob...@>= +static bool @!eof_seen0[max_in_open], + *const @!eof_seen = @!eof_seen0-1; /*has eof been seen?*/ + +@ The |print_group| procedure prints the current level of grouping and +the name corresponding to |cur_group|. + +@<Declare \eTeX\ procedures for tr...@>= +static void print_group(bool @!e) +{@+ +switch (cur_group) { + case bottom_level: {@+print("bottom level");return; + } + case simple_group: case semi_simple_group: + {@+if (cur_group==semi_simple_group) print("semi "); + print("simple"); + } @+break; + case hbox_group: case adjusted_hbox_group: + {@+if (cur_group==adjusted_hbox_group) print("adjusted "); + print("hbox"); + } @+break; + case vbox_group: print("vbox");@+break; + case vtop_group: print("vtop");@+break; + case align_group: case no_align_group: + {@+if (cur_group==no_align_group) print("no "); + print("align"); + } @+break; + case output_group: print("output");@+break; + case disc_group: print("disc");@+break; + case insert_group: print("insert");@+break; + case vcenter_group: print("vcenter");@+break; + case math_group: case math_choice_group: + case math_shift_group: case math_left_group: + {@+print("math"); + if (cur_group==math_choice_group) print(" choice"); + else if (cur_group==math_shift_group) print(" shift"); + else if (cur_group==math_left_group) print(" left"); + } + } /*there are no other cases*/ +print(" group (level ");print_int(qo(cur_level));print_char(')'); +if (saved(-1)!=0) + {@+if (e) print(" entered at line ");else print(" at line "); + print_int(saved(-1)); + } +} + +@ The |group_trace| procedure is called when a new level of grouping +begins (|e==false|) or ends (|e==true|) with |saved(-1)| containing the +line number. + +@<Declare \eTeX\ procedures for tr...@>= +#ifdef @!STAT +static void group_trace(bool @!e) +{@+begin_diagnostic();print_char('{'); +if (e) print("leaving ");else print("entering "); +print_group(e);print_char('}');end_diagnostic(false); +} +#endif + +@ The \.{\\currentgrouplevel} and \.{\\currentgrouptype} commands return +the current level of grouping and the type of the current group +respectively. + +@d current_group_level_code (eTeX_int+1) /*code for \.{\\currentgrouplevel}*/ +@d current_group_type_code (eTeX_int+2) /*code for \.{\\currentgrouptype}*/ + +@<Generate all \eTeX...@>= +primitive("currentgrouplevel", last_item, current_group_level_code); +@!@:current\_group\_level\_}{\.{\\currentgrouplevel} primitive@> +primitive("currentgrouptype", last_item, current_group_type_code); +@!@:current\_group\_type\_}{\.{\\currentgrouptype} primitive@> + +@ @<Cases of |last_item| for |print_cmd_chr|@>= +case current_group_level_code: print_esc("currentgrouplevel");@+break; +case current_group_type_code: print_esc("currentgrouptype");@+break; + +@ @<Cases for fetching an integer value@>= +case current_group_level_code: cur_val=cur_level-level_one;@+break; +case current_group_type_code: cur_val=cur_group;@+break; + +@ The \.{\\currentiflevel}, \.{\\currentiftype}, and +\.{\\currentifbranch} commands return the current level of conditionals +and the type and branch of the current conditional. + +@d current_if_level_code (eTeX_int+3) /*code for \.{\\currentiflevel}*/ +@d current_if_type_code (eTeX_int+4) /*code for \.{\\currentiftype}*/ +@d current_if_branch_code (eTeX_int+5) /*code for \.{\\currentifbranch}*/ + +@<Generate all \eTeX...@>= +primitive("currentiflevel", last_item, current_if_level_code); +@!@:current\_if\_level\_}{\.{\\currentiflevel} primitive@> +primitive("currentiftype", last_item, current_if_type_code); +@!@:current\_if\_type\_}{\.{\\currentiftype} primitive@> +primitive("currentifbranch", last_item, current_if_branch_code); +@!@:current\_if\_branch\_}{\.{\\currentifbranch} primitive@> + +@ @<Cases of |last_item| for |print_cmd_chr|@>= +case current_if_level_code: print_esc("currentiflevel");@+break; +case current_if_type_code: print_esc("currentiftype");@+break; +case current_if_branch_code: print_esc("currentifbranch");@+break; + +@ @<Cases for fetching an integer value@>= +case current_if_level_code: {@+q=cond_ptr;cur_val=0; + while (q!=null) + {@+incr(cur_val);q=link(q); + } + } @+break; +case current_if_type_code: if (cond_ptr==null) cur_val=0; + else if (cur_if < unless_code) cur_val=cur_if+1; + else cur_val=-(cur_if-unless_code+1);@+break; +case current_if_branch_code: + if ((if_limit==or_code)||(if_limit==else_code)) cur_val=1; + else if (if_limit==fi_code) cur_val=-1; + else cur_val=0;@+break; + +@ The \.{\\fontcharwd}, \.{\\fontcharht}, \.{\\fontchardp}, and +\.{\\fontcharic} commands return information about a character in a +font. + +@d font_char_wd_code eTeX_dim /*code for \.{\\fontcharwd}*/ +@d font_char_ht_code (eTeX_dim+1) /*code for \.{\\fontcharht}*/ +@d font_char_dp_code (eTeX_dim+2) /*code for \.{\\fontchardp}*/ +@d font_char_ic_code (eTeX_dim+3) /*code for \.{\\fontcharic}*/ + +@<Generate all \eTeX...@>= +primitive("fontcharwd", last_item, font_char_wd_code); +@!@:font\_char\_wd\_}{\.{\\fontcharwd} primitive@> +primitive("fontcharht", last_item, font_char_ht_code); +@!@:font\_char\_ht\_}{\.{\\fontcharht} primitive@> +primitive("fontchardp", last_item, font_char_dp_code); +@!@:font\_char\_dp\_}{\.{\\fontchardp} primitive@> +primitive("fontcharic", last_item, font_char_ic_code); +@!@:font\_char\_ic\_}{\.{\\fontcharic} primitive@> + +@ @<Cases of |last_item| for |print_cmd_chr|@>= +case font_char_wd_code: print_esc("fontcharwd");@+break; +case font_char_ht_code: print_esc("fontcharht");@+break; +case font_char_dp_code: print_esc("fontchardp");@+break; +case font_char_ic_code: print_esc("fontcharic");@+break; + +@ @<Cases for fetching a dimension value@>= +case font_char_wd_code: +case font_char_ht_code: +case font_char_dp_code: +case font_char_ic_code: {@+scan_font_ident();q=cur_val;scan_char_num(); + if ((font_bc[q] <= cur_val)&&(font_ec[q] >= cur_val)) + {@+i=char_info(q, qi(cur_val)); + switch (m) { + case font_char_wd_code: cur_val=char_width(q, i);@+break; + case font_char_ht_code: cur_val=char_height(q, height_depth(i));@+break; + case font_char_dp_code: cur_val=char_depth(q, height_depth(i));@+break; + case font_char_ic_code: cur_val=char_italic(q, i); + } /*there are no other cases*/ + } + else cur_val=0; + } @+break; + +@ The \.{\\parshapedimen}, \.{\\parshapeindent}, and \.{\\parshapelength} +commands return the indent and length parameters of the current +\.{\\parshape} specification. + +@d par_shape_length_code (eTeX_dim+4) /*code for \.{\\parshapelength}*/ +@d par_shape_indent_code (eTeX_dim+5) /*code for \.{\\parshapeindent}*/ +@d par_shape_dimen_code (eTeX_dim+6) /*code for \.{\\parshapedimen}*/ + +@<Generate all \eTeX...@>= +primitive("parshapelength", last_item, par_shape_length_code); +@!@:par\_shape\_length\_}{\.{\\parshapelength} primitive@> +primitive("parshapeindent", last_item, par_shape_indent_code); +@!@:par\_shape\_indent\_}{\.{\\parshapeindent} primitive@> +primitive("parshapedimen", last_item, par_shape_dimen_code); +@!@:par\_shape\_dimen\_}{\.{\\parshapedimen} primitive@> + +@ @<Cases of |last_item| for |print_cmd_chr|@>= +case par_shape_length_code: print_esc("parshapelength");@+break; +case par_shape_indent_code: print_esc("parshapeindent");@+break; +case par_shape_dimen_code: print_esc("parshapedimen");@+break; + +@ @<Cases for fetching a dimension value@>= +case par_shape_length_code: +case par_shape_indent_code: +case par_shape_dimen_code: {@+q=cur_chr-par_shape_length_code;scan_int(); + if ((par_shape_ptr==null)||(cur_val <= 0)) cur_val=0; + else{@+if (q==2) + {@+q=cur_val%2;cur_val=(cur_val+q)/2; + } + if (cur_val > info(par_shape_ptr)) cur_val=info(par_shape_ptr); + cur_val=mem[par_shape_ptr+2*cur_val-q].sc; + } + cur_val_level=dimen_val; + } @+break; + +@ The \.{\\showgroups} command displays all currently active grouping +levels. + +@d show_groups 4 /* \.{\\showgroups} */ + +@<Generate all \eTeX...@>= +primitive("showgroups", xray, show_groups); +@!@:show\_groups\_}{\.{\\showgroups} primitive@> + +@ @<Cases of |xray| for |print_cmd_chr|@>= +case show_groups: print_esc("showgroups");@+break; + +@ @<Cases for |show_whatever|@>= +case show_groups: {@+begin_diagnostic();show_save_groups(); + } @+break; + +@ @<Types...@>= +typedef int32_t save_pointer; /*index into |save_stack|*/ + +@ The modifications of \TeX\ required for the display produced by the +|show_save_groups| procedure were first discussed by Donald~E. Knuth in +{\sl TUGboat\/} {\bf 11}, 165--170 and 499--511, 1990. +@^Knuth, Donald Ervin@> + +In order to understand a group type we also have to know its mode. +Since unrestricted horizontal modes are not associated with grouping, +they are skipped when traversing the semantic nest. + +@<Declare \eTeX\ procedures for use...@>= +static void show_save_groups(void) +{@+ +int p; /*index into |nest|*/ +int @!m; /*mode*/ +save_pointer @!v; /*saved value of |save_ptr|*/ +quarterword @!l; /*saved value of |cur_level|*/ +group_code @!c; /*saved value of |cur_group|*/ +int @!a; /*to keep track of alignments*/ +int @!i; +quarterword @!j; +char *@!s; +p=nest_ptr;nest[p]=cur_list; /*put the top level into the array*/ +v=save_ptr;l=cur_level;c=cur_group; +save_ptr=cur_boundary;decr(cur_level);@/ +a=1; +print_nl("");print_ln(); +loop@+{@+print_nl("### ");print_group(true); + if (cur_group==bottom_level) goto done; + @/do@+{m=nest[p].mode_field; + if (p > 0) decr(p);else m=vmode; + }@+ while (!(m!=hmode)); + print(" ("); + switch (cur_group) { + case simple_group: {@+incr(p);goto found2; + } + case hbox_group: case adjusted_hbox_group: s="hbox";@+break; + case vbox_group: s="vbox";@+break; + case vtop_group: s="vtop";@+break; + case align_group: if (a==0) + {@+if (m==-vmode) s="halign";else s="valign"; + a=1;goto found1; + } + else{@+if (a==1) print("align entry");else print_esc("cr"); + if (p >= a) p=p-a; + a=0;goto found; + } @+break; + case no_align_group: + {@+incr(p);a=-1;print_esc("noalign");goto found2; + } + case output_group: + {@+print_esc("output");goto found; + } + case math_group: goto found2; + case disc_group: case math_choice_group: + {@+if (cur_group==disc_group) print_esc("discretionary"); + else print_esc("mathchoice"); + for (i=1; i<=3; i++) if (i <= saved(-2)) print("{}"); + goto found2; + } + case insert_group: + {@+if (saved(-2)==255) print_esc("vadjust"); + else{@+print_esc("insert");print_int(saved(-2)); + } + goto found2; + } + case vcenter_group: {@+s="vcenter";goto found1; + } + case semi_simple_group: {@+incr(p);print_esc("begingroup");goto found; + } + case math_shift_group: + {@+if (m==mmode) print_char('$'); + else if (nest[p].mode_field==mmode) + {@+print_cmd_chr(eq_no, saved(-2));goto found; + } + print_char('$');goto found; + } + case math_left_group: + {@+if (type(nest[p+1].eTeX_aux_field)==left_noad) print_esc("left"); + else print_esc("middle"); + goto found; + } + } /*there are no other cases*/ + @<Show the box context@>; + found1: print_esc(s);@<Show the box packaging info@>; + found2: print_char('{'); + found: print_char(')');decr(cur_level); + cur_group=save_level(save_ptr);save_ptr=save_index(save_ptr); + } +done: save_ptr=v;cur_level=l;cur_group=c; +} + +@ @<Show the box packaging info@>= +if (saved(-2)!=0) + {@+print_char(' '); + if (saved(-3)==exactly) print("to");else print("spread"); + print_scaled(saved(-2));print("pt"); + } + +@ @<Show the box context@>= +i=saved(-4); +if (i!=0) + if (i < box_flag) + {@+if (abs(nest[p].mode_field)==vmode) j=hmove;else j=vmove; + if (i > 0) print_cmd_chr(j, 0);else print_cmd_chr(j, 1); + print_scaled(abs(i));print("pt"); + } + else if (i < ship_out_flag) + {@+if (i >= global_box_flag) + {@+print_esc("global");i=i-(global_box_flag-box_flag); + } + print_esc("setbox");print_int(i-box_flag);print_char('='); + } + else print_cmd_chr(leader_ship, i-(leader_flag-a_leaders)) + +@ The |scan_general_text| procedure is much like |scan_toks(false, false)|, +but will be invoked via |expand|, i.e., recursively. +@^recursion@> + +@<Declare \eTeX\ procedures for sc...@>= +static void scan_general_text(void); + +@ The token list (balanced text) created by |scan_general_text| begins +at |link(temp_head)| and ends at |cur_val|. (If |cur_val==temp_head|, +the list is empty.) + +@<Declare \eTeX\ procedures for tok...@>= +static void scan_general_text(void) +{@+ +int s; /*to save |scanner_status|*/ +pointer @!w; /*to save |warning_index|*/ +pointer @!d; /*to save |def_ref|*/ +pointer @!p; /*tail of the token list being built*/ +pointer @!q; /*new node being added to the token list via |store_new_token|*/ +halfword @!unbalance; /*number of unmatched left braces*/ +s=scanner_status;w=warning_index;d=def_ref; +scanner_status=absorbing;warning_index=cur_cs; +def_ref=get_avail();token_ref_count(def_ref)=null;p=def_ref; +scan_left_brace(); /*remove the compulsory left brace*/ +unbalance=1; +loop@+{@+get_token(); + if (cur_tok < right_brace_limit) + if (cur_cmd < right_brace) incr(unbalance); + else{@+decr(unbalance); + if (unbalance==0) goto found; + } + store_new_token(cur_tok); + } +found: q=link(def_ref);free_avail(def_ref); /*discard reference count*/ +if (q==null) cur_val=temp_head;@+else cur_val=p; +link(temp_head)=q; +scanner_status=s;warning_index=w;def_ref=d; +} + +@ The \.{\\showtokens} command displays a token list. + +@d show_tokens 5 /* \.{\\showtokens} , must be odd! */ + +@<Generate all \eTeX...@>= +primitive("showtokens", xray, show_tokens); +@!@:show\_tokens\_}{\.{\\showtokens} primitive@> + +@ @<Cases of |xray| for |print_cmd_chr|@>= +case show_tokens: print_esc("showtokens");@+break; + +@ The \.{\\unexpanded} primitive prevents expansion of tokens much as +the result from \.{\\the} applied to a token variable. The +\.{\\detokenize} primitive converts a token list into a list of +character tokens much as if the token list were written to a file. We +use the fact that the command modifiers for \.{\\unexpanded} and +\.{\\detokenize} are odd whereas those for \.{\\the} and \.{\\showthe} +are even. + +@<Generate all \eTeX...@>= +primitive("unexpanded", the, 1);@/ +@!@:unexpanded\_}{\.{\\unexpanded} primitive@> +primitive("detokenize", the, show_tokens);@/ +@!@:detokenize\_}{\.{\\detokenize} primitive@> + +@ @<Cases of |the| for |print_cmd_chr|@>=; +else if (chr_code==1) print_esc("unexpanded"); +else print_esc("detokenize") + +@ @<Handle \.{\\unexpanded} or \.{\\detokenize} and |return|@>= +if (odd(cur_chr)) + {@+c=cur_chr;scan_general_text(); + if (c==1) return cur_val; + else{@+old_setting=selector;selector=new_string;b=pool_ptr; + p=get_avail();link(p)=link(temp_head); + token_show(p);flush_list(p); + selector=old_setting;return str_toks(b); + } + + } + +@ The \.{\\showifs} command displays all currently active conditionals. + +@d show_ifs 6 /* \.{\\showifs} */ + +@<Generate all \eTeX...@>= +primitive("showifs", xray, show_ifs); +@!@:show\_ifs\_}{\.{\\showifs} primitive@> + +@ @<Cases of |xray| for |print_cmd_chr|@>= +case show_ifs: print_esc("showifs");@+break; + +@ @d print_if_line(A) if (A!=0) + {@+print(" entered on line ");print_int(A); + } + +@<Cases for |show_whatever|@>= +case show_ifs: {@+begin_diagnostic();print_nl("");print_ln(); + if (cond_ptr==null) + {@+print_nl("### ");print("no active conditionals"); + } + else{@+p=cond_ptr;n=0; + @/do@+{incr(n);p=link(p);@+}@+ while (!(p==null)); + p=cond_ptr;t=cur_if;l=if_line;m=if_limit; + @/do@+{print_nl("### level ");print_int(n);print(": "); + print_cmd_chr(if_test, t); + if (m==fi_code) print_esc("else"); + print_if_line(l); + decr(n);t=subtype(p);l=if_line_field(p);m=type(p);p=link(p); + }@+ while (!(p==null)); + } + } @+break; + +@ The \.{\\interactionmode} primitive allows to query and set the +interaction mode. + +@<Generate all \eTeX...@>= +primitive("interactionmode", set_page_int, 2); +@!@:interaction\_mode\_}{\.{\\interactionmode} primitive@> + +@ @<Cases of |set_page_int| for |print_cmd_chr|@>=; +else if (chr_code==2) print_esc("interactionmode") + +@ @<Cases for `Fetch the |dead_cycles| or the |insert_penalties|'@>=; +else if (m==2) cur_val=interaction + +@ @<Declare \eTeX\ procedures for use...@>= +static void new_interaction(void); + +@ @<Cases for |alter_integer|@>=; +else if (c==2) + {@+if ((cur_val < batch_mode)||(cur_val > error_stop_mode)) + {@+print_err("Bad interaction mode"); +@.Bad interaction mode@> + help2("Modes are 0=batch, 1=nonstop, 2=scroll, and",@/ + "3=errorstop. Proceed, and I'll ignore this case."); + int_error(cur_val); + } + else{@+cur_chr=cur_val;new_interaction(); + } + } + +@ The |middle| feature of \eTeX\ allows one ore several \.{\\middle} +delimiters to appear between \.{\\left} and \.{\\right}. + +@<Generate all \eTeX...@>= +primitive("middle", left_right, middle_noad); +@!@:middle\_}{\.{\\middle} primitive@> + +@ @<Cases of |left_right| for |print_cmd_chr|@>=; +else if (chr_code==middle_noad) print_esc("middle") + +@ The |scan_tokens| feature of \eTeX\ defines the \.{\\scantokens} +primitive. + +@<Generate all \eTeX...@>= +primitive("scantokens", input, 2); +@!@:scan\_tokens\_}{\.{\\scantokens} primitive@> + +@ @<Cases of |input| for |print_cmd_chr|@>=; +else if (chr_code==2) print_esc("scantokens") + +@ @<Cases for |input|@>=; +else if (cur_chr==2) pseudo_start() + +@ The global variable |pseudo_files| is used to maintain a stack of +pseudo files. The |info| field of each pseudo file points to a linked +list of variable size nodes representing lines not yet processed: the +|info| field of the first word contains the size of this node, all the +following words contain ASCII codes. + +@<Glob...@>= +static pointer @!pseudo_files; /*stack of pseudo files*/ + +@ @<Set init...@>= +pseudo_files=null; + +@ The |pseudo_start| procedure initiates reading from a pseudo file. + +@<Declare \eTeX\ procedures for ex...@>= +static void pseudo_start(void); + +@ @<Declare \eTeX\ procedures for tok...@>= +static void pseudo_start(void) +{@+int old_setting; /*holds |selector| setting*/ +str_number @!s; /*string to be converted into a pseudo file*/ +pool_pointer @!l, @!m; /*indices into |str_pool|*/ +pointer @!p, @!q, @!r; /*for list construction*/ +four_quarters @!w; /*four ASCII codes*/ +int @!nl, @!sz; +scan_general_text(); +old_setting=selector;selector=new_string; +token_show(temp_head);selector=old_setting; +flush_list(link(temp_head)); +str_room(1);s=make_string(); +@<Convert string |s| into a new pseudo file@>; +flush_string; +@<Initiate input from new pseudo file@>; +} + +@ @<Convert string |s| into a new pseudo file@>= +str_pool[pool_ptr]=si(' ');l=str_start[s]; +nl=si(new_line_char); +p=get_avail();q=p; +while (l < pool_ptr) + {@+m=l; + while ((l < pool_ptr)&&(str_pool[l]!=nl)) incr(l); + sz=(l-m+7)/4; + if (sz==1) sz=2; + r=get_node(sz);link(q)=r;q=r;info(q)=hi(sz); + while (sz > 2) + {@+decr(sz);incr(r); + w.b0=qi(so(str_pool[m]));w.b1=qi(so(str_pool[m+1])); + w.b2=qi(so(str_pool[m+2]));w.b3=qi(so(str_pool[m+3])); + mem[r].qqqq=w;m=m+4; + } + w.b0=qi(' ');w.b1=qi(' ');w.b2=qi(' ');w.b3=qi(' '); + if (l > m) + {@+w.b0=qi(so(str_pool[m])); + if (l > m+1) + {@+w.b1=qi(so(str_pool[m+1])); + if (l > m+2) + {@+w.b2=qi(so(str_pool[m+2])); + if (l > m+3) w.b3=qi(so(str_pool[m+3])); + } + } + } + mem[r+1].qqqq=w; + if (str_pool[l]==nl) incr(l); + } +info(p)=link(p);link(p)=pseudo_files;pseudo_files=p + +@ @<Initiate input from new pseudo file@>= +begin_file_reading(); /*set up |cur_file| and new level of input*/ +line=0;limit=start;loc=limit+1; /*force line read*/ +if (tracing_scan_tokens > 0) + {@+if (term_offset > max_print_line-3) print_ln(); + else if ((term_offset > 0)||(file_offset > 0)) print_char(' '); + name=19;print("( ");incr(open_parens);update_terminal; + } +else name=18 + +@ Here we read a line from the current pseudo file into |buffer|. + +@<Declare \eTeX\ procedures for tr...@>= +static bool pseudo_input(void) /*inputs the next line or returns |false|*/ +{@+pointer p; /*current line from pseudo file*/ +int @!sz; /*size of node |p|*/ +four_quarters @!w; /*four ASCII codes*/ +int @!r; /*loop index*/ +last=first; /*cf.\ Matthew 19\thinspace:\thinspace30*/ +p=info(pseudo_files); +if (p==null) return false; +else{@+info(pseudo_files)=link(p);sz=ho(info(p)); + if (4*sz-3 >= buf_size-last) + @<Report overflow of the input buffer, and abort@>; + last=first; + for (r=p+1; r<=p+sz-1; r++) + {@+w=mem[r].qqqq; + buffer[last]=w.b0;buffer[last+1]=w.b1; + buffer[last+2]=w.b2;buffer[last+3]=w.b3; + last=last+4; + } + if (last >= max_buf_stack) max_buf_stack=last+1; + while ((last > first)&&(buffer[last-1]==' ')) decr(last); + free_node(p, sz); + return true; + } +} + +@ When we are done with a pseudo file we `close' it. + +@<Declare \eTeX\ procedures for tr...@>= +static void pseudo_close(void) /*close the top level pseudo file*/ +{@+pointer p, @!q; +p=link(pseudo_files);q=info(pseudo_files); +free_avail(pseudo_files);pseudo_files=p; +while (q!=null) + {@+p=q;q=link(p);free_node(p, ho(info(p))); + } +} + +@ @<Dump the \eTeX\ state@>= +while (pseudo_files!=null) pseudo_close(); /*flush pseudo files*/ + +@ @<Generate all \eTeX...@>= +primitive("readline", read_to_cs, 1);@/ +@!@:read\_line\_}{\.{\\readline} primitive@> + +@ @<Cases of |read| for |print_cmd_chr|@>=; +else print_esc("readline") + +@ @<Handle \.{\\readline} and |goto done|@>= +if (j==1) + {@+while (loc <= limit) /*current line not yet finished*/ + {@+cur_chr=buffer[loc];incr(loc); + if (cur_chr==' ') cur_tok=space_token; + @+else cur_tok=cur_chr+other_token; + store_new_token(cur_tok); + } + goto done; + } + +@ Here we define the additional conditionals of \eTeX\ as well as the +\.{\\unless} prefix. + +@d if_def_code 17 /* `\.{\\ifdefined}' */ +@d if_cs_code 18 /* `\.{\\ifcsname}' */ +@d if_font_char_code 19 /* `\.{\\iffontchar}' */ +@d eTeX_last_if_test_cmd_mod if_font_char_code +@d eTeX_last_expand_after_cmd_mod 1 + +@<Generate all \eTeX...@>= +primitive("unless", expand_after, 1);@/ +@!@:unless\_}{\.{\\unless} primitive@> +primitive("ifdefined", if_test, if_def_code); +@!@:if\_defined\_}{\.{\\ifdefined} primitive@> +primitive("ifcsname", if_test, if_cs_code); +@!@:if\_cs\_name\_}{\.{\\ifcsname} primitive@> +primitive("iffontchar", if_test, if_font_char_code); +@!@:if\_font\_char\_}{\.{\\iffontchar} primitive@> + +@ @<Cases of |expandafter| for |print_cmd_chr|@>= +case 1: print_esc("unless");@+break; + +@ @<Cases of |if_test| for |print_cmd_chr|@>= +case if_def_code: print_esc("ifdefined");@+break; +case if_cs_code: print_esc("ifcsname");@+break; +case if_font_char_code: print_esc("iffontchar");@+break; + +@ The result of a boolean condition is reversed when the conditional is +preceded by \.{\\unless}. + +@<Negate a boolean conditional and |goto reswitch|@>= +{@+get_token(); +if ((cur_cmd==if_test)&&(cur_chr!=if_case_code)) + {@+cur_chr=cur_chr+unless_code;goto reswitch; + } +print_err("You can't use `");print_esc("unless");print("' before `"); +@.You can't use \\unless...@> +print_cmd_chr(cur_cmd, cur_chr);print_char('\''); +help1("Continue, and I'll forget that it ever happened."); +back_error(); +} + +@ The conditional \.{\\ifdefined} tests if a control sequence is +defined. + +We need to reset |scanner_status|, since \.{\\outer} control sequences +are allowed, but we might be scanning a macro definition or preamble. + +@<Cases for |conditional|@>= +case if_def_code: {@+save_scanner_status=scanner_status; + scanner_status=normal; + get_next();b=(cur_cmd!=undefined_cs); + scanner_status=save_scanner_status; + } @+break; + +@ The conditional \.{\\ifcsname} is equivalent to \.{\{\\expandafter} +\.{\}\\expandafter} \.{\\ifdefined} \.{\\csname}, except that no new +control sequence will be entered into the hash table (once all tokens +preceding the mandatory \.{\\endcsname} have been expanded). + +@<Cases for |conditional|@>= +case if_cs_code: {@+n=get_avail();p=n; /*head of the list of characters*/ + @/do@+{get_x_token(); + if (cur_cs==0) store_new_token(cur_tok); + }@+ while (!(cur_cs!=0)); + if (cur_cmd!=end_cs_name) @<Complain about missing \.{\\endcsname}@>; + @<Look up the characters of list |n| in the hash table, and set |cur_cs|@>; + flush_list(n); + b=(eq_type(cur_cs)!=undefined_cs); + } @+break; + +@ @<Look up the characters of list |n| in the hash table...@>= +m=first;p=link(n); +while (p!=null) + {@+if (m >= max_buf_stack) + {@+max_buf_stack=m+1; + if (max_buf_stack==buf_size) + overflow("buffer size", buf_size); +@:TeX capacity exceeded buffer size}{\quad buffer size@> + } + buffer[m]=info(p)%0400;incr(m);p=link(p); + } +if (m==first) cur_cs=null_cs; /*the list is empty*/ +else if (m > first+1) + cur_cs=id_lookup(first, m-first); /*|no_new_control_sequence| is |true|*/ +else cur_cs=single_base+buffer[first] /*the list has length one*/ + +@ The conditional \.{\\iffontchar} tests the existence of a character in +a font. + +@<Cases for |conditional|@>= +case if_font_char_code: {@+scan_font_ident();n=cur_val;scan_char_num(); + if ((font_bc[n] <= cur_val)&&(font_ec[n] >= cur_val)) + b=char_exists(char_info(n, qi(cur_val))); + else b=false; + } @+break; + +@ The \.{protected} feature of \eTeX\ defines the \.{\\protected} prefix +command for macro definitions. Such macros are protected against +expansions when lists of expanded tokens are built, e.g., for \.{\\edef} +or during \.{\\write}. + +@<Generate all \eTeX...@>= +primitive("protected", prefix, 8); +@!@:protected\_}{\.{\\protected} primitive@> + +@ @<Cases of |prefix| for |print_cmd_chr|@>=; +else if (chr_code==8) print_esc("protected") + +@ The |get_x_or_protected| procedure is like |get_x_token| except that +protected macros are not expanded. + +@<Declare \eTeX\ procedures for sc...@>= +static void get_x_or_protected(void) /*sets |cur_cmd|, |cur_chr|, |cur_tok|, + and expands non-protected macros*/ +{@+ +loop@+{@+get_token(); + if (cur_cmd <= max_command) return; + if ((cur_cmd >= call)&&(cur_cmd < end_template)) + if (info(link(cur_chr))==protected_token) return; + expand(); + } +} + +@ A group entered (or a conditional started) in one file may end in a +different file. Such slight anomalies, although perfectly legitimate, +may cause errors that are difficult to locate. In order to be able to +give a warning message when such anomalies occur, \eTeX\ uses the +|grp_stack| and |if_stack| arrays to record the initial |cur_boundary| +and |cond_ptr| values for each input file. + +@<Glob...@>= +static save_pointer @!grp_stack[max_in_open+1]; /*initial |cur_boundary|*/ +static pointer @!if_stack[max_in_open+1]; /*initial |cond_ptr|*/ + +@ When a group ends that was apparently entered in a different input +file, the |group_warning| procedure is invoked in order to update the +|grp_stack|. If moreover \.{\\tracingnesting} is positive we want to +give a warning message. The situation is, however, somewhat complicated +by two facts: (1)~There may be |grp_stack| elements without a +corresponding \.{\\input} file or \.{\\scantokens} pseudo file (e.g., +error insertions from the terminal); and (2)~the relevant information is +recorded in the |name_field| of the |input_stack| only loosely +synchronized with the |in_open| variable indexing |grp_stack|. + +@<Declare \eTeX\ procedures for tr...@>= +static void group_warning(void) +{@+int i; /*index into |grp_stack|*/ +bool @!w; /*do we need a warning?*/ +base_ptr=input_ptr;input_stack[base_ptr]=cur_input; + /*store current state*/ +i=in_open;w=false; +while ((grp_stack[i]==cur_boundary)&&(i > 0)) + {@+@<Set variable |w| to indicate if this case should be reported@>; + grp_stack[i]=save_index(save_ptr);decr(i); + } +if (w) + {@+print_nl("Warning: end of ");print_group(true); +@.Warning: end of...@> + print(" of a different file");print_ln(); + if (tracing_nesting > 1) show_context(); + if (history==spotless) history=warning_issued; + } +} + +@ This code scans the input stack in order to determine the type of the +current input file. + +@<Set variable |w| to...@>= +if (tracing_nesting > 0) + {@+while ((input_stack[base_ptr].state_field==token_list)||@| + (input_stack[base_ptr].index_field > i)) decr(base_ptr); + if (input_stack[base_ptr].name_field > 17) w=true; + } + +@ When a conditional ends that was apparently started in a different +input file, the |if_warning| procedure is invoked in order to update the +|if_stack|. If moreover \.{\\tracingnesting} is positive we want to +give a warning message (with the same complications as above). + +@<Declare \eTeX\ procedures for tr...@>= +static void if_warning(void) +{@+int i; /*index into |if_stack|*/ +bool @!w; /*do we need a warning?*/ +base_ptr=input_ptr;input_stack[base_ptr]=cur_input; + /*store current state*/ +i=in_open;w=false; +while (if_stack[i]==cond_ptr) + {@+@<Set variable |w| to...@>; + if_stack[i]=link(cond_ptr);decr(i); + } +if (w) + {@+print_nl("Warning: end of ");print_cmd_chr(if_test, cur_if); +@.Warning: end of...@> + print_if_line(if_line);print(" of a different file");print_ln(); + if (tracing_nesting > 1) show_context(); + if (history==spotless) history=warning_issued; + } +} + +@ Conversely, the |file_warning| procedure is invoked when a file ends +and some groups entered or conditionals started while reading from that +file are still incomplete. + +@<Declare \eTeX\ procedures for tr...@>= +static void file_warning(void) +{@+pointer p; /*saved value of |save_ptr| or |cond_ptr|*/ +quarterword @!l; /*saved value of |cur_level| or |if_limit|*/ +quarterword @!c; /*saved value of |cur_group| or |cur_if|*/ +int @!i; /*saved value of |if_line|*/ +p=save_ptr;l=cur_level;c=cur_group;save_ptr=cur_boundary; +while (grp_stack[in_open]!=save_ptr) + {@+decr(cur_level); + print_nl("Warning: end of file when "); +@.Warning: end of file when...@> + print_group(true);print(" is incomplete");@/ + cur_group=save_level(save_ptr);save_ptr=save_index(save_ptr); + } +save_ptr=p;cur_level=l;cur_group=c; /*restore old values*/ +p=cond_ptr;l=if_limit;c=cur_if;i=if_line; +while (if_stack[in_open]!=cond_ptr) + {@+print_nl("Warning: end of file when "); +@.Warning: end of file when...@> + print_cmd_chr(if_test, cur_if); + if (if_limit==fi_code) print_esc("else"); + print_if_line(if_line);print(" is incomplete");@/ + if_line=if_line_field(cond_ptr);cur_if=subtype(cond_ptr); + if_limit=type(cond_ptr);cond_ptr=link(cond_ptr); + } +cond_ptr=p;if_limit=l;cur_if=c;if_line=i; /*restore old values*/ +print_ln(); +if (tracing_nesting > 1) show_context(); +if (history==spotless) history=warning_issued; +} + +@ Here are the additional \eTeX\ primitives for expressions. + +@<Generate all \eTeX...@>= +primitive("numexpr", last_item, eTeX_expr-int_val+int_val); +@!@:num\_expr\_}{\.{\\numexpr} primitive@> +primitive("dimexpr", last_item, eTeX_expr-int_val+dimen_val); +@!@:dim\_expr\_}{\.{\\dimexpr} primitive@> +primitive("glueexpr", last_item, eTeX_expr-int_val+glue_val); +@!@:glue\_expr\_}{\.{\\glueexpr} primitive@> +primitive("muexpr", last_item, eTeX_expr-int_val+mu_val); +@!@:mu\_expr\_}{\.{\\muexpr} primitive@> + +@ @<Cases of |last_item| for |print_cmd_chr|@>= +case eTeX_expr-int_val+int_val: print_esc("numexpr");@+break; +case eTeX_expr-int_val+dimen_val: print_esc("dimexpr");@+break; +case eTeX_expr-int_val+glue_val: print_esc("glueexpr");@+break; +case eTeX_expr-int_val+mu_val: print_esc("muexpr");@+break; + +@ This code for reducing |cur_val_level| and\slash or negating the +result is similar to the one for all the other cases of +|scan_something_internal|, with the difference that |scan_expr| has +already increased the reference count of a glue specification. + +@<Process an expression and |return|@>= +{@+if (m < eTeX_mu) + {@+switch (m) { + @/@<Cases for fetching a glue value@>@/ + } /*there are no other cases*/ + cur_val_level=glue_val; + } +else if (m < eTeX_expr) + {@+switch (m) { + @/@<Cases for fetching a mu value@>@/ + } /*there are no other cases*/ + cur_val_level=mu_val; + } +else{@+cur_val_level=m-eTeX_expr+int_val;scan_expr(); + } +while (cur_val_level > level) + {@+if (cur_val_level==glue_val) + {@+m=cur_val;cur_val=width(m);delete_glue_ref(m); + } + else if (cur_val_level==mu_val) mu_error(); + decr(cur_val_level); + } +if (negative) + if (cur_val_level >= glue_val) + {@+m=cur_val;cur_val=new_spec(m);delete_glue_ref(m); + @<Negate all three glue components of |cur_val|@>; + } + else negate(cur_val); +return; +} + +@ @<Declare \eTeX\ procedures for sc...@>= +static void scan_expr(void); + +@ The |scan_expr| procedure scans and evaluates an expression. + +@<Declare procedures needed for expressions@>= +@t\4@>@<Declare subprocedures for |scan_expr|@>@; +static void scan_expr(void) /*scans and evaluates an expression*/ +{@+ +bool a, @!b; /*saved values of |arith_error|*/ +small_number @!l; /*type of expression*/ +small_number @!r; /*state of expression so far*/ +small_number @!s; /*state of term so far*/ +small_number @!o; /*next operation or type of next factor*/ +int @!e; /*expression so far*/ +int @!t; /*term so far*/ +int @!f; /*current factor*/ +int @!n; /*numerator of combined multiplication and division*/ +pointer @!p; /*top of expression stack*/ +pointer @!q; /*for stack manipulations*/ +l=cur_val_level;a=arith_error;b=false;p=null; +@<Scan and evaluate an expression |e| of type |l|@>; +if (b) + {@+print_err("Arithmetic overflow"); +@.Arithmetic overflow@> + help2("I can't evaluate this expression,",@/ + "since the result is out of range."); + error(); + if (l >= glue_val) + {@+delete_glue_ref(e);e=zero_glue;add_glue_ref(e); + } + else e=0; + } +arith_error=a;cur_val=e;cur_val_level=l; +} + +@ Evaluating an expression is a recursive process: When the left +parenthesis of a subexpression is scanned we descend to the next level +of recursion; the previous level is resumed with the matching right +parenthesis. + +@d expr_none 0 /*\.( seen, or \.( $\langle\it expr\rangle$ \.) seen*/ +@d expr_add 1 /*\.( $\langle\it expr\rangle$ \.+ seen*/ +@d expr_sub 2 /*\.( $\langle\it expr\rangle$ \.- seen*/ +@d expr_mult 3 /*$\langle\it term\rangle$ \.* seen*/ +@d expr_div 4 /*$\langle\it term\rangle$ \./ seen*/ +@d expr_scale 5 /*$\langle\it term\rangle$ \.* + $\langle\it factor\rangle$ \./ seen*/ + +@<Scan and eval...@>= +restart: r=expr_none;e=0;s=expr_none;t=0;n=0; +resume: if (s==expr_none) o=l;@+else o=int_val; +@<Scan a factor |f| of type |o| or start a subexpression@>; +found: @<Scan the next operator and set |o|@>; +arith_error=b; +@<Make sure that |f| is in the proper range@>; +switch (s) {@<Cases for evaluation of the current term@>@; +} /*there are no other cases*/ +if (o > expr_sub) s=o;@+else@<Evaluate the current expression@>; +b=arith_error; +if (o!=expr_none) goto resume; +if (p!=null) @<Pop the expression stack and |goto found|@>@; + +@ @<Scan the next op...@>= +@<Get the next non-blank non-call token@>; +if (cur_tok==other_token+'+') o=expr_add; +else if (cur_tok==other_token+'-') o=expr_sub; +else if (cur_tok==other_token+'*') o=expr_mult; +else if (cur_tok==other_token+'/') o=expr_div; +else{@+o=expr_none; + if (p==null) + {@+if (cur_cmd!=relax) back_input(); + } + else if (cur_tok!=other_token+')') + {@+print_err("Missing ) inserted for expression"); +@.Missing ) inserted@> + help1("I was expecting to see `+', `-', `*', `/', or `)'. Didn't."); + back_error(); + } + } + +@ @<Scan a factor...@>= +@<Get the next non-blank non-call token@>; +if (cur_tok==other_token+'(') + @<Push the expression stack and |goto restart|@>; +back_input(); +if (o==int_val) scan_int(); +else if (o==dimen_val) scan_normal_dimen; +else if (o==glue_val) scan_normal_glue(); +else scan_mu_glue(); +f=cur_val + +@ @<Declare \eTeX\ procedures for sc...@>= +static void scan_normal_glue(void);@/ +static void scan_mu_glue(void); + +@ Here we declare two trivial procedures in order to avoid mutually +recursive procedures with parameters. + +@<Declare procedures needed for expressions@>= +static void scan_normal_glue(void) +{@+scan_glue(glue_val); +} +@# +static void scan_mu_glue(void) +{@+scan_glue(mu_val); +} + +@ Parenthesized subexpressions can be inside expressions, and this +nesting has a stack. Seven local variables represent the top of the +expression stack: |p| points to pushed-down entries, if any; |l| +specifies the type of expression currently beeing evaluated; |e| is the +expression so far and |r| is the state of its evaluation; |t| is the +term so far and |s| is the state of its evaluation; finally |n| is the +numerator for a combined multiplication and division, if any. + +@d expr_node_size 4 /*number of words in stack entry for subexpressions*/ +@d expr_e_field(A) mem[A+1].i /*saved expression so far*/ +@d expr_t_field(A) mem[A+2].i /*saved term so far*/ +@d expr_n_field(A) mem[A+3].i /*saved numerator*/ + +@<Push the expression...@>= +{@+q=get_node(expr_node_size);link(q)=p;type(q)=l; +subtype(q)=4*s+r; +expr_e_field(q)=e;expr_t_field(q)=t;expr_n_field(q)=n; +p=q;l=o;goto restart; +} + +@ @<Pop the expression...@>= +{@+f=e;q=p; +e=expr_e_field(q);t=expr_t_field(q);n=expr_n_field(q); +s=subtype(q)/4;r=subtype(q)%4; +l=type(q);p=link(q);free_node(q, expr_node_size); +goto found; +} + +@ We want to make sure that each term and (intermediate) result is in +the proper range. Integer values must not exceed |infinity| +($2^{31}-1$) in absolute value, dimensions must not exceed |max_dimen| +($2^{30}-1$). We avoid the absolute value of an integer, because this +might fail for the value $-2^{31}$ using 32-bit arithmetic. + +@d num_error(A) /*clear a number or dimension and set |arith_error|*/ + {@+arith_error=true;A=0; + } +@d glue_error(A) /*clear a glue spec and set |arith_error|*/ + {@+arith_error=true;delete_glue_ref(A);A=new_spec(zero_glue); + } + +@<Make sure that |f|...@>= +if ((l==int_val)||(s > expr_sub)) + {@+if ((f > infinity)||(f < -infinity)) num_error(f); + } +else if (l==dimen_val) + {@+if (abs(f) > max_dimen) num_error(f); + } +else{@+if ((abs(width(f)) > max_dimen)||@| + (abs(stretch(f)) > max_dimen)||@| + (abs(shrink(f)) > max_dimen)) glue_error(f); + } + +@ Applying the factor |f| to the partial term |t| (with the operator +|s|) is delayed until the next operator |o| has been scanned. Here we +handle the first factor of a partial term. A glue spec has to be copied +unless the next operator is a right parenthesis; this allows us later on +to simply modify the glue components. + +@d normalize_glue(A) + if (stretch(A)==0) stretch_order(A)=normal; + if (shrink(A)==0) shrink_order(A)=normal + +@<Cases for evaluation of the current term@>= +case expr_none: if ((l >= glue_val)&&(o!=expr_none)) + {@+t=new_spec(f);delete_glue_ref(f);normalize_glue(t); + } + else t=f;@+break; + +@ When a term |t| has been completed it is copied to, added to, or +subtracted from the expression |e|. + +@d expr_add_sub(A, B, C) add_or_sub(A, B, C, r==expr_sub) +@d expr_a(A, B) expr_add_sub(A, B, max_dimen) + +@<Evaluate the current expression@>= +{@+s=expr_none; +if (r==expr_none) e=t; +else if (l==int_val) e=expr_add_sub(e, t, infinity); +else if (l==dimen_val) e=expr_a(e, t); +else@<Compute the sum or difference of two glue specs@>; +r=o; +} + +@ The function |add_or_sub(x, y, max_answer, negative)| computes the sum +(for |negative==false|) or difference (for |negative==true|) of |x| and +|y|, provided the absolute value of the result does not exceed +|max_answer|. + +@<Declare subprocedures for |scan_expr|@>= +static int add_or_sub(int @!x, int @!y, int @!max_answer, bool @!negative) +{@+int a; /*the answer*/ +if (negative) negate(y); +if (x >= 0) + if (y <= max_answer-x) a=x+y;@+else num_error(a)@; +else if (y >= -max_answer-x) a=x+y;@+else num_error(a); +return a; +} + +@ We know that |stretch_order(e) > normal| implies |stretch(e)!=0| and +|shrink_order(e) > normal| implies |shrink(e)!=0|. + +@<Compute the sum or diff...@>= +{@+width(e)=expr_a(width(e), width(t)); +if (stretch_order(e)==stretch_order(t)) + stretch(e)=expr_a(stretch(e), stretch(t)); +else if ((stretch_order(e) < stretch_order(t))&&(stretch(t)!=0)) + {@+stretch(e)=stretch(t);stretch_order(e)=stretch_order(t); + } +if (shrink_order(e)==shrink_order(t)) + shrink(e)=expr_a(shrink(e), shrink(t)); +else if ((shrink_order(e) < shrink_order(t))&&(shrink(t)!=0)) + {@+shrink(e)=shrink(t);shrink_order(e)=shrink_order(t); + } +delete_glue_ref(t);normalize_glue(e); +} + +@ If a multiplication is followed by a division, the two operations are +combined into a `scaling' operation. Otherwise the term |t| is +multiplied by the factor |f|. + +@d expr_m(A) A=nx_plus_y(A, f, 0) + +@<Cases for evaluation of the current term@>= +case expr_mult: if (o==expr_div) + {@+n=f;o=expr_scale; + } + else if (l==int_val) t=mult_integers(t, f); + else if (l==dimen_val) expr_m(t); + else{@+expr_m(width(t));expr_m(stretch(t));expr_m(shrink(t)); + } @+break; + +@ Here we divide the term |t| by the factor |f|. + +@d expr_d(A) A=quotient(A, f) + +@<Cases for evaluation of the current term@>= +case expr_div: if (l < glue_val) expr_d(t); + else{@+expr_d(width(t));expr_d(stretch(t));expr_d(shrink(t)); + } @+break; + +@ The function |quotient(n, d)| computes the rounded quotient +$q=\lfloor n/d+{1\over2}\rfloor$, when $n$ and $d$ are positive. + +@<Declare subprocedures for |scan_expr|@>= +static int quotient(int @!n, int @!d) +{@+bool negative; /*should the answer be negated?*/ +int @!a; /*the answer*/ +if (d==0) num_error(a)@; +else{@+if (d > 0) negative=false; + else{@+negate(d);negative=true; + } + if (n < 0) + {@+negate(n);negative=!negative; + } + a=n/d;n=n-a*d;d=n-d; /*avoid certain compiler optimizations!*/ + if (d+n >= 0) incr(a); + if (negative) negate(a); + } +return a; +} + +@ Here the term |t| is multiplied by the quotient $n/f$. + +@d expr_s(A) A=fract(A, n, f, max_dimen) + +@<Cases for evaluation of the current term@>= +case expr_scale: if (l==int_val) t=fract(t, n, f, infinity); + else if (l==dimen_val) expr_s(t); + else{@+expr_s(width(t));expr_s(stretch(t));expr_s(shrink(t)); + } + +@ Finally, the function |fract(x, n, d, max_answer)| computes the integer +$q=\lfloor xn/d+{1\over2}\rfloor$, when $x$, $n$, and $d$ are positive +and the result does not exceed |max_answer|. We can't use floating +point arithmetic since the routine must produce identical results in all +cases; and it would be too dangerous to multiply by~|n| and then divide +by~|d|, in separate operations, since overflow might well occur. Hence +this subroutine simulates double precision arithmetic, somewhat +analogous to \MF's |make_fraction| and |take_fraction| routines. + +@<Declare subprocedures for |scan_expr|@>= +static int fract(int @!x, int @!n, int @!d, int @!max_answer) +{@+ +bool negative; /*should the answer be negated?*/ +int @!a; /*the answer*/ +int @!f; /*a proper fraction*/ +int @!h; /*smallest integer such that |2*h >= d|*/ +int @!r; /*intermediate remainder*/ +int @!t; /*temp variable*/ +if (d==0) goto too_big; +a=0; +if (d > 0) negative=false; +else{@+negate(d);negative=true; + } +if (x < 0) + {@+negate(x);negative=!negative; + } +else if (x==0) goto done; +if (n < 0) + {@+negate(n);negative=!negative; + } +t=n/d; +if (t > max_answer/x) goto too_big; +a=t*x;n=n-t*d; +if (n==0) goto found; +t=x/d; +if (t > (max_answer-a)/n) goto too_big; +a=a+t*n;x=x-t*d; +if (x==0) goto found; +if (x < n) + {@+t=x;x=n;n=t; + } /*now |0 < n <= x < d|*/ +@<Compute \(f)$f=\lfloor xn/d+{1\over2}\rfloor$@>@; +if (f > (max_answer-a)) goto too_big; +a=a+f; +found: if (negative) negate(a); +goto done; +too_big: num_error(a); +done: return a; +} + +@ The loop here preserves the following invariant relations +between |f|, |x|, |n|, and~|r|: +(i)~$f+\lfloor(xn+(r+d))/d\rfloor=\lfloor x_0n_0/d+{1\over2}\rfloor$; +(ii)~|-d <= r < 0 < n <= x < d|, where $x_0$, $n_0$ are the original values of~$x$ +and $n$. + +Notice that the computation specifies |(x-d)+x| instead of |(x+x)-d|, +because the latter could overflow. + +@<Compute \(f)$f=\lfloor xn/d+{1\over2}\rfloor$@>= +f=0;r=(d/2)-d;h=-r; +loop@+{@+if (odd(n)) + {@+r=r+x; + if (r >= 0) + {@+r=r-d;incr(f); + } + } + n=n/2; + if (n==0) goto found1; + if (x < h) x=x+x; + else{@+t=x-d;x=t+x;f=f+n; + if (x < n) + {@+if (x==0) goto found1; + t=x;x=n;n=t; + } + } + } +found1: + +@ The \.{\\gluestretch}, \.{\\glueshrink}, \.{\\gluestretchorder}, and +\.{\\glueshrinkorder} commands return the stretch and shrink components +and their orders of ``infinity'' of a glue specification. + +@d glue_stretch_order_code (eTeX_int+6) /*code for \.{\\gluestretchorder}*/ +@d glue_shrink_order_code (eTeX_int+7) /*code for \.{\\glueshrinkorder}*/ +@d glue_stretch_code (eTeX_dim+7) /*code for \.{\\gluestretch}*/ +@d glue_shrink_code (eTeX_dim+8) /*code for \.{\\glueshrink}*/ + +@<Generate all \eTeX...@>= +primitive("gluestretchorder", last_item, glue_stretch_order_code); +@!@:glue\_stretch\_order\_}{\.{\\gluestretchorder} primitive@> +primitive("glueshrinkorder", last_item, glue_shrink_order_code); +@!@:glue\_shrink\_order\_}{\.{\\glueshrinkorder} primitive@> +primitive("gluestretch", last_item, glue_stretch_code); +@!@:glue\_stretch\_}{\.{\\gluestretch} primitive@> +primitive("glueshrink", last_item, glue_shrink_code); +@!@:glue\_shrink\_}{\.{\\glueshrink} primitive@> + +@ @<Cases of |last_item| for |print_cmd_chr|@>= +case glue_stretch_order_code: print_esc("gluestretchorder");@+break; +case glue_shrink_order_code: print_esc("glueshrinkorder");@+break; +case glue_stretch_code: print_esc("gluestretch");@+break; +case glue_shrink_code: print_esc("glueshrink");@+break; + +@ @<Cases for fetching an integer value@>= +case glue_stretch_order_code: case glue_shrink_order_code: + {@+scan_normal_glue();q=cur_val; + if (m==glue_stretch_order_code) cur_val=stretch_order(q); + else cur_val=shrink_order(q); + delete_glue_ref(q); + } + +@ @<Cases for fetching a dimension value@>= +case glue_stretch_code: case glue_shrink_code: + {@+scan_normal_glue();q=cur_val; + if (m==glue_stretch_code) cur_val=stretch(q); + else cur_val=shrink(q); + delete_glue_ref(q); + } + +@ The \.{\\mutoglue} and \.{\\gluetomu} commands convert ``math'' glue +into normal glue and vice versa; they allow to manipulate math glue with +\.{\\gluestretch} etc. + +@d mu_to_glue_code eTeX_glue /*code for \.{\\mutoglue}*/ +@d glue_to_mu_code eTeX_mu /*code for \.{\\gluetomu}*/ + +@<Generate all \eTeX...@>= +primitive("mutoglue", last_item, mu_to_glue_code); +@!@:mu\_to\_glue\_}{\.{\\mutoglue} primitive@> +primitive("gluetomu", last_item, glue_to_mu_code); +@!@:glue\_to\_mu\_}{\.{\\gluetomu} primitive@> + +@ @<Cases of |last_item| for |print_cmd_chr|@>= +case mu_to_glue_code: print_esc("mutoglue");@+break; +case glue_to_mu_code: print_esc("gluetomu");@+break; + +@ @<Cases for fetching a glue value@>= +case mu_to_glue_code: scan_mu_glue(); + +@ @<Cases for fetching a mu value@>= +case glue_to_mu_code: scan_normal_glue(); + +@ \eTeX\ (in extended mode) supports 32768 (i.e., $2^{15}$) count, +dimen, skip, muskip, box, and token registers. As in \TeX\ the first +256 registers of each kind are realized as arrays in the table of +equivalents; the additional registers are realized as tree structures +built from variable-size nodes with individual registers existing only +when needed. Default values are used for nonexistent registers: zero +for count and dimen values, |zero_glue| for glue (skip and muskip) +values, void for boxes, and |null| for token lists (and current marks +discussed below). + +Similarly there are 32768 mark classes; the command \.{\\marks}|n| +creates a mark node for a given mark class |0 <= n <= 32767| (where +\.{\\marks0} is synonymous to \.{\\mark}). The page builder (actually +the |fire_up| routine) and the |vsplit| routine maintain the current +values of |top_mark|, |first_mark|, |bot_mark|, |split_first_mark|, and +|split_bot_mark| for each mark class. They are accessed as +\.{\\topmarks}|n| etc., and \.{\\topmarks0} is again synonymous to +\.{\\topmark}. As in \TeX\ the five current marks for mark class zero +are realized as |cur_mark| array. The additional current marks are +again realized as tree structure with individual mark classes existing +only when needed. + +@<Generate all \eTeX...@>= +primitive("marks", mark, marks_code); +@!@:marks\_}{\.{\\marks} primitive@> +primitive("topmarks", top_bot_mark, top_mark_code+marks_code); +@!@:top\_marks\_}{\.{\\topmarks} primitive@> +primitive("firstmarks", top_bot_mark, first_mark_code+marks_code); +@!@:first\_marks\_}{\.{\\firstmarks} primitive@> +primitive("botmarks", top_bot_mark, bot_mark_code+marks_code); +@!@:bot\_marks\_}{\.{\\botmarks} primitive@> +primitive("splitfirstmarks", top_bot_mark, split_first_mark_code+marks_code); +@!@:split\_first\_marks\_}{\.{\\splitfirstmarks} primitive@> +primitive("splitbotmarks", top_bot_mark, split_bot_mark_code+marks_code); +@!@:split\_bot\_marks\_}{\.{\\splitbotmarks} primitive@> + +@ The |scan_register_num| procedure scans a register number that must +not exceed 255 in compatibility mode resp.\ 32767 in extended mode. + +@<Declare \eTeX\ procedures for ex...@>= +static void scan_register_num(void); + +@ @<Declare procedures that scan restricted classes of integers@>= +static void scan_register_num(void) +{@+scan_int(); +if ((cur_val < 0)||(cur_val > max_reg_num)) + {@+print_err("Bad register code"); +@.Bad register code@> + help2(max_reg_help_line,"I changed this one to zero."); + int_error(cur_val);cur_val=0; + } +} + +@ @<Initialize variables for \eTeX\ comp...@>= +max_reg_num=255; +max_reg_help_line="A register number must be between 0 and 255."; + +@ @<Initialize variables for \eTeX\ ext...@>= +max_reg_num=32767; +max_reg_help_line="A register number must be between 0 and 32767."; + +@ @<Glob...@>= +static halfword @!max_reg_num; /*largest allowed register number*/ +static char *@!max_reg_help_line; /*first line of help message*/ + +@ There are seven almost identical doubly linked trees, one for the +sparse array of the up to 32512 additional registers of each kind and +one for the sparse array of the up to 32767 additional mark classes. +The root of each such tree, if it exists, is an index node containing 16 +pointers to subtrees for 4096 consecutive array elements. Similar index +nodes are the starting points for all nonempty subtrees for 4096, 256, +and 16 consecutive array elements. These four levels of index nodes are +followed by a fifth level with nodes for the individual array elements. + +Each index node is nine words long. The pointers to the 16 possible +subtrees or are kept in the |info| and |link| fields of the last eight +words. (It would be both elegant and efficient to declare them as +array, unfortunately \PASCAL\ doesn't allow this.) + +The fields in the first word of each index node and in the nodes for the +array elements are closely related. The |link| field points to the next +lower index node and the |sa_index| field contains four bits (one +hexadecimal digit) of the register number or mark class. For the lowest +index node the |link| field is |null| and the |sa_index| field indicates +the type of quantity (|int_val|, |dimen_val|, |glue_val|, |mu_val|, +|box_val|, |tok_val|, or |mark_val|). The |sa_used| field in the index +nodes counts how many of the 16 pointers are non-null. + +The |sa_index| field in the nodes for array elements contains the four +bits plus 16 times the type. Therefore such a node represents a count +or dimen register if and only if |sa_index < dimen_val_limit|; it +represents a skip or muskip register if and only if +|dimen_val_limit <= sa_index < mu_val_limit|; it represents a box register +if and only if |mu_val_limit <= sa_index < box_val_limit|; it represents a +token list register if and only if +|box_val_limit <= sa_index < tok_val_limit|; finally it represents a mark +class if and only if |tok_val_limit <= sa_index|. + +The |new_index| procedure creates an index node (returned in |cur_ptr|) +having given contents of the |sa_index| and |link| fields. + +@d box_val 4 /*the additional box registers*/ +@d mark_val 6 /*the additional mark classes*/ +@# +@d dimen_val_limit 0x20 /*$2^4\cdot(|dimen_val|+1)$*/ +@d mu_val_limit 0x40 /*$2^4\cdot(|mu_val|+1)$*/ +@d box_val_limit 0x50 /*$2^4\cdot(|box_val|+1)$*/ +@d tok_val_limit 0x60 /*$2^4\cdot(|tok_val|+1)$*/ +@# +@d index_node_size 9 /*size of an index node*/ +@d sa_index(A) type(A) /*a four-bit address or a type or both*/ +@d sa_used(A) subtype(A) /*count of non-null pointers*/ + +@<Declare \eTeX\ procedures for ex...@>= +static void new_index(quarterword @!i, pointer @!q) +{@+int k; /*loop index*/ +cur_ptr=get_node(index_node_size);sa_index(cur_ptr)=i; +sa_used(cur_ptr)=0;link(cur_ptr)=q; +for (k=1; k<=index_node_size-1; k++) /*clear all 16 pointers*/ + mem[cur_ptr+k]=sa_null; +} + +@ The roots of the seven trees for the additional registers and mark +classes are kept in the |sa_root| array. The first six locations must +be dumped and undumped; the last one is also known as |sa_mark|. + +@d sa_mark sa_root[mark_val] /*root for mark classes*/ + +@<Glob...@>= +static pointer @!sa_root0[mark_val-int_val+1], + *const @!sa_root = @!sa_root0-int_val; /*roots of sparse arrays*/ +static pointer @!cur_ptr; /*value returned by |new_index| and |find_sa_element|*/ +static memory_word @!sa_null; /*two |null| pointers*/ + +@ @<Set init...@>= +sa_mark=null;sa_null.hh.lh=null;sa_null.hh.rh=null; + +@ @<Initialize table...@>= +for (i=int_val; i<=tok_val; i++) sa_root[i]=null; + +@ Given a type |t| and a sixteen-bit number |n|, the |find_sa_element| +procedure returns (in |cur_ptr|) a pointer to the node for the +corresponding array element, or |null| when no such element exists. The +third parameter |w| is set |true| if the element must exist, e.g., +because it is about to be modified. The procedure has two main +branches: one follows the existing tree structure, the other (only used +when |w| is |true|) creates the missing nodes. + +We use macros to extract the four-bit pieces from a sixteen-bit register +number or mark class and to fetch or store one of the 16 pointers from +an index node. + +@d if_cur_ptr_is_null_then_return_or_goto(A) /*some tree element is missing*/ + {@+if (cur_ptr==null) + if (w) goto A;@+else return; + } +@# +@d hex_dig1(A) A/4096 /*the fourth lowest hexadecimal digit*/ +@d hex_dig2(A) (A/256)%16 /*the third lowest hexadecimal digit*/ +@d hex_dig3(A) (A/16)%16 /*the second lowest hexadecimal digit*/ +@d hex_dig4(A) A%16 /*the lowest hexadecimal digit*/ +@# +@d get_sa_ptr if (odd(i)) cur_ptr=link(q+(i/2)+1); + else cur_ptr=info(q+(i/2)+1) + /*set |cur_ptr| to the pointer indexed by |i| from index node |q|*/ +@d put_sa_ptr(A) if (odd(i)) link(q+(i/2)+1)=A; + else info(q+(i/2)+1)=A + /*store the pointer indexed by |i| in index node |q|*/ +@d add_sa_ptr {@+put_sa_ptr(cur_ptr);incr(sa_used(q)); + } /*add |cur_ptr| as the pointer indexed by |i| in index node |q|*/ +@d delete_sa_ptr {@+put_sa_ptr(null);decr(sa_used(q)); + } /*delete the pointer indexed by |i| in index node |q|*/ + +@<Declare \eTeX\ procedures for ex...@>= +static void find_sa_element(small_number @!t, halfword @!n, bool @!w) + /*sets |cur_val| to sparse array element location or |null|*/ +{@+ +pointer q; /*for list manipulations*/ +small_number @!i; /*a four bit index*/ +cur_ptr=sa_root[t]; +if_cur_ptr_is_null_then_return_or_goto(not_found);@/ +q=cur_ptr;i=hex_dig1(n);get_sa_ptr; +if_cur_ptr_is_null_then_return_or_goto(not_found1);@/ +q=cur_ptr;i=hex_dig2(n);get_sa_ptr; +if_cur_ptr_is_null_then_return_or_goto(not_found2);@/ +q=cur_ptr;i=hex_dig3(n);get_sa_ptr; +if_cur_ptr_is_null_then_return_or_goto(not_found3);@/ +q=cur_ptr;i=hex_dig4(n);get_sa_ptr; +if ((cur_ptr==null)&&w) goto not_found4; +return; +not_found: new_index(t, null); /*create first level index node*/ +sa_root[t]=cur_ptr;q=cur_ptr;i=hex_dig1(n); +not_found1: new_index(i, q); /*create second level index node*/ +add_sa_ptr;q=cur_ptr;i=hex_dig2(n); +not_found2: new_index(i, q); /*create third level index node*/ +add_sa_ptr;q=cur_ptr;i=hex_dig3(n); +not_found3: new_index(i, q); /*create fourth level index node*/ +add_sa_ptr;q=cur_ptr;i=hex_dig4(n); +not_found4: @<Create a new array element of type |t| with index |i|@>; +link(cur_ptr)=q;add_sa_ptr; +} + +@ The array elements for registers are subject to grouping and have an +|sa_lev| field (quite analogous to |eq_level|) instead of |sa_used|. +Since saved values as well as shorthand definitions (created by e.g., +\.{\\countdef}) refer to the location of the respective array element, +we need a reference count that is kept in the |sa_ref| field. An array +element can be deleted (together with all references to it) when its +|sa_ref| value is |null| and its value is the default value. +@^reference counts@> + +Skip, muskip, box, and token registers use two word nodes, their values +are stored in the |sa_ptr| field. +Count and dimen registers use three word nodes, their +values are stored in the |sa_int| resp.\ |sa_dim| field in the third +word; the |sa_ptr| field is used under the name |sa_num| to store +the register number. Mark classes use four word nodes. The last three +words contain the five types of current marks + +@d sa_lev sa_used /*grouping level for the current value*/ +@d pointer_node_size 2 /*size of an element with a pointer value*/ +@d sa_type(A) (sa_index(A)/16) /*type part of combined type/index*/ +@d sa_ref(A) info(A+1) /*reference count of a sparse array element*/ +@d sa_ptr(A) link(A+1) /*a pointer value*/ +@# +@d word_node_size 3 /*size of an element with a word value*/ +@d sa_num(A) sa_ptr(A) /*the register number*/ +@d sa_int(A) mem[A+2].i /*an integer*/ +@d sa_dim(A) mem[A+2].sc /*a dimension (a somewhat esotheric distinction)*/ +@# +@d mark_class_node_size 4 /*size of an element for a mark class*/ +@# +@d fetch_box(A) /*fetch |box(cur_val)|*/ + if (cur_val < 256) A=box(cur_val); + else{@+find_sa_element(box_val, cur_val, false); + if (cur_ptr==null) A=null;@+else A=sa_ptr(cur_ptr); + } + +@<Create a new array element...@>= +if (t==mark_val) /*a mark class*/ + {@+cur_ptr=get_node(mark_class_node_size); + mem[cur_ptr+1]=sa_null;mem[cur_ptr+2]=sa_null;mem[cur_ptr+3]=sa_null; + } +else{@+if (t <= dimen_val) /*a count or dimen register*/ + {@+cur_ptr=get_node(word_node_size);sa_int(cur_ptr)=0; + sa_num(cur_ptr)=n; + } + else{@+cur_ptr=get_node(pointer_node_size); + if (t <= mu_val) /*a skip or muskip register*/ + {@+sa_ptr(cur_ptr)=zero_glue;add_glue_ref(zero_glue); + } + else sa_ptr(cur_ptr)=null; /*a box or token list register*/ + } + sa_ref(cur_ptr)=null; /*all registers have a reference count*/ + } +sa_index(cur_ptr)=16*t+i;sa_lev(cur_ptr)=level_one + +@ The |delete_sa_ref| procedure is called when a pointer to an array +element representing a register is being removed; this means that the +reference count should be decreased by one. If the reduced reference +count is |null| and the register has been (globally) assigned its +default value the array element should disappear, possibly together with +some index nodes. This procedure will never be used for mark class +nodes. +@^reference counts@> + +@d add_sa_ref(A) incr(sa_ref(A)) /*increase reference count*/ +@# +@d change_box(A) /*change |box(cur_val)|, the |eq_level| stays the same*/ + if (cur_val < 256) box(cur_val)=A;@+else set_sa_box(A) +@# +@d set_sa_box(X) {@+find_sa_element(box_val, cur_val, false); + if (cur_ptr!=null) + {@+sa_ptr(cur_ptr)=X;add_sa_ref(cur_ptr);delete_sa_ref(cur_ptr); + } + } + +@<Declare \eTeX\ procedures for tr...@>= +static void delete_sa_ref(pointer @!q) /*reduce reference count*/ +{@+ +pointer p; /*for list manipulations*/ +small_number @!i; /*a four bit index*/ +small_number @!s; /*size of a node*/ +decr(sa_ref(q)); +if (sa_ref(q)!=null) return; +if (sa_index(q) < dimen_val_limit) + if (sa_int(q)==0) s=word_node_size; + else return; +else{@+if (sa_index(q) < mu_val_limit) + if (sa_ptr(q)==zero_glue) delete_glue_ref(zero_glue); + else return; + else if (sa_ptr(q)!=null) return; + s=pointer_node_size; + } +@/do@+{i=hex_dig4(sa_index(q));p=q;q=link(p);free_node(p, s); +if (q==null) /*the whole tree has been freed*/ + {@+sa_root[i]=null;return; + } +delete_sa_ptr;s=index_node_size; /*node |q| is an index node*/ +}@+ while (!(sa_used(q) > 0)); +} + +@ The |print_sa_num| procedure prints the register number corresponding +to an array element. + +@<Basic print...@>= +static void print_sa_num(pointer @!q) /*print register number*/ +{@+halfword @!n; /*the register number*/ +if (sa_index(q) < dimen_val_limit) n=sa_num(q); /*the easy case*/ +else{@+n=hex_dig4(sa_index(q));q=link(q);n=n+16*sa_index(q); + q=link(q);n=n+256*(sa_index(q)+16*sa_index(link(q))); + } +print_int(n); +} + +@ Here is a procedure that displays the contents of an array element +symbolically. It is used under similar circumstances as is +|restore_trace| (together with |show_eqtb|) for the quantities kept in +the |eqtb| array. + +@<Declare \eTeX\ procedures for tr...@>= +#ifdef @!STAT +static void show_sa(pointer @!p, char *@!s) +{@+small_number t; /*the type of element*/ +begin_diagnostic();print_char('{');print(s);print_char(' '); +if (p==null) print_char('?'); /*this can't happen*/ +else{@+t=sa_type(p); + if (t < box_val) print_cmd_chr(internal_register, p); + else if (t==box_val) + {@+print_esc("box");print_sa_num(p); + } + else if (t==tok_val) print_cmd_chr(toks_register, p); + else print_char('?'); /*this can't happen either*/ + print_char('='); + if (t==int_val) print_int(sa_int(p)); + else if (t==dimen_val) + {@+print_scaled(sa_dim(p));print("pt"); + } + else{@+p=sa_ptr(p); + if (t==glue_val) print_spec(p,"pt"); + else if (t==mu_val) print_spec(p,"mu"); + else if (t==box_val) + if (p==null) print("void"); + else{@+depth_threshold=0;breadth_max=1;show_node_list(p); + } + else if (t==tok_val) + {@+if (p!=null) show_token_list(link(p), null, 32); + } + else print_char('?'); /*this can't happen either*/ + } + } +print_char('}');end_diagnostic(false); +} +#endif + +@ Here we compute the pointer to the current mark of type |t| and mark +class |cur_val|. + +@<Compute the mark pointer...@>= +{@+find_sa_element(mark_val, cur_val, false); +if (cur_ptr!=null) + if (odd(t)) cur_ptr=link(cur_ptr+(t/2)+1); + else cur_ptr=info(cur_ptr+(t/2)+1); +} + +@ The current marks for all mark classes are maintained by the |vsplit| +and |fire_up| routines and are finally destroyed (for \.{INITEX} only) +@.INITEX@> +by the |final_cleanup| routine. Apart from updating the current marks +when mark nodes are encountered, these routines perform certain actions +on all existing mark classes. The recursive |do_marks| procedure walks +through the whole tree or a subtree of existing mark class nodes and +preforms certain actions indicted by its first parameter |a|, the action +code. The second parameter |l| indicates the level of recursion (at +most four); the third parameter points to a nonempty tree or subtree. +The result is |true| if the complete tree or subtree has been deleted. + +@d vsplit_init 0 /*action code for |vsplit| initialization*/ +@d fire_up_init 1 /*action code for |fire_up| initialization*/ +@d fire_up_done 2 /*action code for |fire_up| completion*/ +@d destroy_marks 3 /*action code for |final_cleanup|*/ +@# +@d sa_top_mark(A) info(A+1) /*\.{\\topmarks}|n|*/ +@d sa_first_mark(A) link(A+1) /*\.{\\firstmarks}|n|*/ +@d sa_bot_mark(A) info(A+2) /*\.{\\botmarks}|n|*/ +@d sa_split_first_mark(A) link(A+2) /*\.{\\splitfirstmarks}|n|*/ +@d sa_split_bot_mark(A) info(A+3) /*\.{\\splitbotmarks}|n|*/ + +@<Declare the function called |do_marks|@>= +static bool do_marks(small_number @!a, small_number @!l, pointer @!q) +{@+int i; /*a four bit index*/ +if (l < 4) /*|q| is an index node*/ + {@+for (i=0; i<=15; i++) + {@+get_sa_ptr; + if (cur_ptr!=null) if (do_marks(a, l+1, cur_ptr)) delete_sa_ptr; + } + if (sa_used(q)==0) + {@+free_node(q, index_node_size);q=null; + } + } +else /*|q| is the node for a mark class*/ + {@+switch (a) { + @<Cases for |do_marks|@>@; + } /*there are no other cases*/ + if (sa_bot_mark(q)==null) if (sa_split_bot_mark(q)==null) + {@+free_node(q, mark_class_node_size);q=null; + } + } +return(q==null); +} + +@ At the start of the |vsplit| routine the existing |split_fist_mark| +and |split_bot_mark| are discarded. + +@<Cases for |do_marks|@>= +case vsplit_init: if (sa_split_first_mark(q)!=null) + {@+delete_token_ref(sa_split_first_mark(q));sa_split_first_mark(q)=null; + delete_token_ref(sa_split_bot_mark(q));sa_split_bot_mark(q)=null; + } @+break; + +@ We use again the fact that |split_first_mark==null| if and only if +|split_bot_mark==null|. + +@<Update the current marks for |vsplit|@>= +{@+find_sa_element(mark_val, mark_class(p), true); +if (sa_split_first_mark(cur_ptr)==null) + {@+sa_split_first_mark(cur_ptr)=mark_ptr(p); + add_token_ref(mark_ptr(p)); + } +else delete_token_ref(sa_split_bot_mark(cur_ptr)); +sa_split_bot_mark(cur_ptr)=mark_ptr(p); +add_token_ref(mark_ptr(p)); +} + +@ At the start of the |fire_up| routine the old |top_mark| and +|first_mark| are discarded, whereas the old |bot_mark| becomes the new +|top_mark|. An empty new |top_mark| token list is, however, discarded +as well in order that mark class nodes can eventually be released. We +use again the fact that |bot_mark!=null| implies |first_mark!=null|; it +also knows that |bot_mark==null| implies |top_mark==first_mark==null|. + +@<Cases for |do_marks|@>= +case fire_up_init: if (sa_bot_mark(q)!=null) + {@+if (sa_top_mark(q)!=null) delete_token_ref(sa_top_mark(q)); + delete_token_ref(sa_first_mark(q));sa_first_mark(q)=null; + if (link(sa_bot_mark(q))==null) /*an empty token list*/ + {@+delete_token_ref(sa_bot_mark(q));sa_bot_mark(q)=null; + } + else add_token_ref(sa_bot_mark(q)); + sa_top_mark(q)=sa_bot_mark(q); + } @+break; + +@ @<Cases for |do_marks|@>= +case fire_up_done: if ((sa_top_mark(q)!=null)&&(sa_first_mark(q)==null)) + {@+sa_first_mark(q)=sa_top_mark(q);add_token_ref(sa_top_mark(q)); + } @+break; + +@ @<Update the current marks for |fire_up|@>= +{@+find_sa_element(mark_val, mark_class(p), true); +if (sa_first_mark(cur_ptr)==null) + {@+sa_first_mark(cur_ptr)=mark_ptr(p); + add_token_ref(mark_ptr(p)); + } +if (sa_bot_mark(cur_ptr)!=null) delete_token_ref(sa_bot_mark(cur_ptr)); +sa_bot_mark(cur_ptr)=mark_ptr(p);add_token_ref(mark_ptr(p)); +} + +@ Here we use the fact that the five current mark pointers in a mark +class node occupy the same locations as the the first five pointers of +an index node. For systems using a run-time switch to distinguish +between \.{VIRTEX} and \.{INITEX}, the codewords `$|@t\#\&{ifdef} \.{INIT}@>|\ldots|@t\#\&{endif}@>|$' +surrounding the following piece of code should be removed. +@.INITEX@> +@^system dependencies@> + +@<Cases for |do_marks|@>= +#ifdef @!INIT +case destroy_marks: for (i=top_mark_code; i<=split_bot_mark_code; i++) + {@+get_sa_ptr; + if (cur_ptr!=null) + {@+delete_token_ref(cur_ptr);put_sa_ptr(null); + } + } +#endif + +@ The command code |internal_register| is used for `\.{\\count}', `\.{\\dimen}', +etc., as well as for references to sparse array elements defined by +`\.{\\countdef}', etc. + +@<Cases of |register| for |print_cmd_chr|@>= +{@+if ((chr_code < mem_bot)||(chr_code > lo_mem_stat_max)) + cmd=sa_type(chr_code); +else{@+cmd=chr_code-mem_bot;chr_code=null; + } +if (cmd==int_val) print_esc("count"); +else if (cmd==dimen_val) print_esc("dimen"); +else if (cmd==glue_val) print_esc("skip"); +else print_esc("muskip"); +if (chr_code!=null) print_sa_num(chr_code); +} + +@ Similarly the command code |toks_register| is used for `\.{\\toks}' as +well as for references to sparse array elements defined by +`\.{\\toksdef}'. + +@<Cases of |toks_register| for |print_cmd_chr|@>= +{@+print_esc("toks"); +if (chr_code!=mem_bot) print_sa_num(chr_code); +} + +@ When a shorthand definition for an element of one of the sparse arrays +is destroyed, we must reduce the reference count. + +@<Cases for |eq_destroy|@>= +case toks_register: case internal_register: + if ((equiv_field(w) < mem_bot)||(equiv_field(w) > lo_mem_stat_max)) + delete_sa_ref(equiv_field(w));@+break; + +@ The task to maintain (change, save, and restore) register values is +essentially the same when the register is realized as sparse array +element or entry in |eqtb|. The global variable |sa_chain| is the head +of a linked list of entries saved at the topmost level |sa_level|; the +lists for lowel levels are kept in special save stack entries. + +@<Glob...@>= +static pointer @!sa_chain; /*chain of saved sparse array entries*/ +static quarterword @!sa_level; /*group level for |sa_chain|*/ + +@ @<Set init...@>= +sa_chain=null;sa_level=level_zero; + +@ The individual saved items are kept in pointer or word nodes similar +to those used for the array elements: a word node with value zero is, +however, saved as pointer node with the otherwise impossible |sa_index| +value |tok_val_limit|. + +@d sa_loc(A) sa_ref(A) /*location of saved item*/ + +@<Declare \eTeX\ procedures for tr...@>= +static void sa_save(pointer @!p) /*saves value of |p|*/ +{@+pointer q; /*the new save node*/ +quarterword @!i; /*index field of node*/ +if (cur_level!=sa_level) + {@+check_full_save_stack;save_type(save_ptr)=restore_sa; + save_level(save_ptr)=sa_level;save_index(save_ptr)=sa_chain; + incr(save_ptr);sa_chain=null;sa_level=cur_level; + } +i=sa_index(p); +if (i < dimen_val_limit) + {@+if (sa_int(p)==0) + {@+q=get_node(pointer_node_size);i=tok_val_limit; + } + else{@+q=get_node(word_node_size);sa_int(q)=sa_int(p); + } + sa_ptr(q)=null; + } +else{@+q=get_node(pointer_node_size);sa_ptr(q)=sa_ptr(p); + } +sa_loc(q)=p;sa_index(q)=i;sa_lev(q)=sa_lev(p); +link(q)=sa_chain;sa_chain=q;add_sa_ref(p); +} + +@ @<Declare \eTeX\ procedures for tr...@>= +static void sa_destroy(pointer @!p) /*destroy value of |p|*/ +{@+if (sa_index(p) < mu_val_limit) delete_glue_ref(sa_ptr(p)); +else if (sa_ptr(p)!=null) + if (sa_index(p) < box_val_limit) flush_node_list(sa_ptr(p)); + else delete_token_ref(sa_ptr(p)); +} + +@ The procedure |sa_def| assigns a new value to sparse array elements, +and saves the former value if appropriate. This procedure is used only +for skip, muskip, box, and token list registers. The counterpart of +|sa_def| for count and dimen registers is called |sa_w_def|. + +@d sa_define(A, B, C, D, E) if (e) + if (global) gsa_def(A, B);@+else sa_def(A, B); + else if (global) geq_define(C, D, E);@+else eq_define(C, D, E) +@# +@d sa_def_box /*assign |cur_box| to |box(cur_val)|*/ + {@+find_sa_element(box_val, cur_val, true); + if (global) gsa_def(cur_ptr, cur_box);@+else sa_def(cur_ptr, cur_box); + } +@# +@d sa_word_define(A, B) if (e) + if (global) gsa_w_def(A, B);@+else sa_w_def(A, B); + else word_define(A, B) + +@<Declare \eTeX\ procedures for tr...@>= +static void sa_def(pointer @!p, halfword @!e) + /*new data for sparse array elements*/ +{@+add_sa_ref(p); +if (sa_ptr(p)==e) + { +#ifdef @!STAT +if (tracing_assigns > 0) show_sa(p,"reassigning"); +#endif +@;@/ + sa_destroy(p); + } +else{ +#ifdef @!STAT +if (tracing_assigns > 0) show_sa(p,"changing"); +#endif +@;@/ + if (sa_lev(p)==cur_level) sa_destroy(p);@+else sa_save(p); + sa_lev(p)=cur_level;sa_ptr(p)=e; +#ifdef @!STAT + if (tracing_assigns > 0) show_sa(p,"into"); +#endif +@;@/ + } +delete_sa_ref(p); +} +@# +static void sa_w_def(pointer @!p, int @!w) +{@+add_sa_ref(p); +if (sa_int(p)==w) + { +#ifdef @!STAT +if (tracing_assigns > 0) show_sa(p,"reassigning"); +#endif +@;@/ + } +else{ +#ifdef @!STAT +if (tracing_assigns > 0) show_sa(p,"changing"); +#endif +@;@/ + if (sa_lev(p)!=cur_level) sa_save(p); + sa_lev(p)=cur_level;sa_int(p)=w; +#ifdef @!STAT + if (tracing_assigns > 0) show_sa(p,"into"); +#endif +@;@/ + } +delete_sa_ref(p); +} + +@ The |sa_def| and |sa_w_def| routines take care of local definitions. +@^global definitions@> +Global definitions are done in almost the same way, but there is no need +to save old values, and the new value is associated with |level_one|. + +@<Declare \eTeX\ procedures for tr...@>= +static void gsa_def(pointer @!p, halfword @!e) /*global |sa_def|*/ +{@+add_sa_ref(p); +#ifdef @!STAT +if (tracing_assigns > 0) show_sa(p,"globally changing"); +#endif +@;@/ +sa_destroy(p);sa_lev(p)=level_one;sa_ptr(p)=e; +#ifdef @!STAT +if (tracing_assigns > 0) show_sa(p,"into"); +#endif +@;@/ +delete_sa_ref(p); +} +@# +static void gsa_w_def(pointer @!p, int @!w) /*global |sa_w_def|*/ +{@+add_sa_ref(p); +#ifdef @!STAT +if (tracing_assigns > 0) show_sa(p,"globally changing"); +#endif +@;@/ +sa_lev(p)=level_one;sa_int(p)=w; +#ifdef @!STAT +if (tracing_assigns > 0) show_sa(p,"into"); +#endif +@;@/ +delete_sa_ref(p); +} + +@ The |sa_restore| procedure restores the sparse array entries pointed +at by |sa_chain| + +@<Declare \eTeX\ procedures for tr...@>= +static void sa_restore(void) +{@+pointer p; /*sparse array element*/ +@/do@+{p=sa_loc(sa_chain); +if (sa_lev(p)==level_one) + {@+if (sa_index(p) >= dimen_val_limit) sa_destroy(sa_chain); +#ifdef @!STAT + if (tracing_restores > 0) show_sa(p,"retaining"); +#endif +@;@/ + } +else{@+if (sa_index(p) < dimen_val_limit) + if (sa_index(sa_chain) < dimen_val_limit) sa_int(p)=sa_int(sa_chain); + else sa_int(p)=0; + else{@+sa_destroy(p);sa_ptr(p)=sa_ptr(sa_chain); + } + sa_lev(p)=sa_lev(sa_chain); +#ifdef @!STAT + if (tracing_restores > 0) show_sa(p,"restoring"); +#endif +@;@/ + } +delete_sa_ref(p); +p=sa_chain;sa_chain=link(p); +if (sa_index(p) < dimen_val_limit) free_node(p, word_node_size); +else free_node(p, pointer_node_size); +}@+ while (!(sa_chain==null)); +} + +@ When reading \.{\\patterns} while \.{\\savinghyphcodes} is positive +the current |lc_code| values are stored together with the hyphenation +patterns for the current language. They will later be used instead of +the |lc_code| values for hyphenation purposes. + +The |lc_code| values are stored in the linked trie analogous to patterns +$p_1$ of length~1, with |hyph_root==trie_r[0]| replacing |trie_root| and +|lc_code(p_1)| replacing the |trie_op| code. This allows to compress +and pack them together with the patterns with minimal changes to the +existing code. + +@d hyph_root trie_r[0] /*root of the linked trie for |hyph_codes|*/ + +@<Initialize table entries...@>= +hyph_root=0;hyph_start=0; + +@ @<Store hyphenation codes for current language@>= +{@+c=cur_lang;first_child=false;p=0; +@/do@+{q=p;p=trie_r[q]; +}@+ while (!((p==0)||(c <= so(trie_c[p])))); +if ((p==0)||(c < so(trie_c[p]))) + @<Insert a new trie node between |q| and |p|, and make |p| point to it@>; +q=p; /*now node |q| represents |cur_lang|*/ +@<Store all current |lc_code| values@>; +} + +@ We store all nonzero |lc_code| values, overwriting any previously +stored values (and possibly wasting a few trie nodes that were used +previously and are not needed now). We always store at least one +|lc_code| value such that |hyph_index| (defined below) will not be zero. + +@<Store all current |lc_code| values@>= +p=trie_l[q];first_child=true; +for (c=0; c<=255; c++) + if ((lc_code(c) > 0)||((c==255)&&first_child)) + {@+if (p==0) + @<Insert a new trie node between |q| and |p|, and make |p| point to +it@>@; + else trie_c[p]=si(c); + trie_o[p]=qi(lc_code(c)); + q=p;p=trie_r[q];first_child=false; + } +if (first_child) trie_l[q]=0;@+else trie_r[q]=0 + +@ We must avoid to ``take'' location~1, in order to distinguish between +|lc_code| values and patterns. + +@<Pack all stored |hyph_codes|@>= +{@+if (trie_root==0) for (p=0; p<=255; p++) trie_min[p]=p+2; +first_fit(hyph_root);trie_pack(hyph_root); +hyph_start=trie_ref[hyph_root]; +} + +@ The global variable |hyph_index| will point to the hyphenation codes +for the current language. + +@d set_hyph_index /*set |hyph_index| for current language*/ + if (trie_char(hyph_start+cur_lang)!=qi(cur_lang) + ) hyph_index=0; /*no hyphenation codes for |cur_lang|*/ + else hyph_index=trie_link(hyph_start+cur_lang) +@# +@d set_lc_code(A) /*set |hc[0]| to hyphenation or lc code for |A|*/ + if (hyph_index==0) hc[0]=lc_code(A); + else if (trie_char(hyph_index+A)!=qi(A)) hc[0]=0; + else hc[0]=qo(trie_op(hyph_index+A)) + +@<Glob...@>= +static trie_pointer @!hyph_start; /*root of the packed trie for |hyph_codes|*/ +static trie_pointer @!hyph_index; /*pointer to hyphenation codes for |cur_lang|*/ + +@ When |saving_vdiscards| is positive then the glue, kern, and penalty +nodes removed by the page builder or by \.{\\vsplit} from the top of a +vertical list are saved in special lists instead of being discarded. + +@d tail_page_disc disc_ptr[copy_code] /*last item removed by page builder*/ +@d page_disc disc_ptr[last_box_code] /*first item removed by page builder*/ +@d split_disc disc_ptr[vsplit_code] /*first item removed by \.{\\vsplit}*/ + +@<Glob...@>= +static pointer @!disc_ptr0[vsplit_code-copy_code+1], + *const @!disc_ptr = @!disc_ptr0-copy_code; /*list pointers*/ + +@ @<Set init...@>= +page_disc=null;split_disc=null; + +@ The \.{\\pagediscards} and \.{\\splitdiscards} commands share the +command code |un_vbox| with \.{\\unvbox} and \.{\\unvcopy}, they are +distinguished by their |chr_code| values |last_box_code| and +|vsplit_code|. These |chr_code| values are larger than |box_code| and +|copy_code|. + +@<Generate all \eTeX...@>= +primitive("pagediscards", un_vbox, last_box_code);@/ +@!@:page\_discards\_}{\.{\\pagediscards} primitive@> +primitive("splitdiscards", un_vbox, vsplit_code);@/ +@!@:split\_discards\_}{\.{\\splitdiscards} primitive@> + +@ @<Cases of |un_vbox| for |print_cmd_chr|@>=; +else if (chr_code==last_box_code) print_esc("pagediscards"); +else if (chr_code==vsplit_code) print_esc("splitdiscards") + +@ @<Handle saved items and |goto done|@>= +{@+link(tail)=disc_ptr[cur_chr];disc_ptr[cur_chr]=null; +goto done; +} + +@ The \.{\\interlinepenalties}, \.{\\clubpenalties}, \.{\\widowpenalties}, +and \.{\\displaywidowpenalties} commands allow to define arrays of +penalty values to be used instead of the corresponding single values. + +@d inter_line_penalties_ptr equiv(inter_line_penalties_loc) +@<Generate all \eTeX...@>= +primitive("interlinepenalties", set_shape, inter_line_penalties_loc);@/ +@!@:inter\_line\_penalties\_}{\.{\\interlinepenalties} primitive@> +primitive("clubpenalties", set_shape, club_penalties_loc);@/ +@!@:club\_penalties\_}{\.{\\clubpenalties} primitive@> +primitive("widowpenalties", set_shape, widow_penalties_loc);@/ +@!@:widow\_penalties\_}{\.{\\widowpenalties} primitive@> +primitive("displaywidowpenalties", set_shape, display_widow_penalties_loc);@/ +@!@:display\_widow\_penalties\_}{\.{\\displaywidowpenalties} primitive@> + +@ @<Cases of |set_shape| for |print_cmd_chr|@>= +case inter_line_penalties_loc: print_esc("interlinepenalties");@+break; +case club_penalties_loc: print_esc("clubpenalties");@+break; +case widow_penalties_loc: print_esc("widowpenalties");@+break; +case display_widow_penalties_loc: print_esc("displaywidowpenalties"); + +@ @<Fetch a penalties array element@>= +{@+scan_int(); +if ((equiv(m)==null)||(cur_val < 0)) cur_val=0; +else{@+if (cur_val > penalty(equiv(m))) cur_val=penalty(equiv(m)); + cur_val=penalty(equiv(m)+cur_val); + } +} + +@ |expand_depth| and |expand_depth_count| are used in the \eTeX\ code +above, but not defined. So we correct this in the following modules, +|expand_depth| having been defined by us as an integer paramater (hence +there is a new primitive to create in \eTeX\ mode), and +|expand_depth_count| needing to be a global. Both have to be defined to +some sensible value. + +@<Glob...@>= +static int @!expand_depth_count; /*current expansion depth*/ + +@ @<Generate all \eTeX...@>= +primitive("expanddepth", assign_int, int_base+expand_depth_code);@/ +@!@:expand\_depth\_}{\.{\\expanddepth} primitive@> + +@ @<Cases for |print_param|@>= +case expand_depth_code: print_esc("expanddepth");@+break; + +@ @<Initialize variables for \eTeX\ extended mode@>= +expand_depth=10000; /*value taken for compatibility with Web2C*/ +expand_depth_count=0; + +@* The extended features of \Prote. +\Prote\ extends furthermore \eTeX\ i.e. \eTeX\ is thus required +before adding \Prote\ own extensions. But if \eTeX\ mode has not +be enabled, the engine is still compatible with \TeX with no added +primitive commands and with a modification of code---from +\eTeX\ exclusively for now---that is sufficiently minor so that +the engine still deserves the name \TeX. + +@d Prote_ex (Prote_mode==1) /*is this prote mode?*/ + +@<Glob...@>= +static int @!Prote_mode; /*to be or not to be; but an int to dump*/ + +@ We begin in \TeX\ compatibility mode. The state |Prote_mode| will be +set to $1$ only if activated by the supplementary `*' added to the one +activating the \eTeX\ extensions (in fact, this means for the user two +initial `*' in a row). + +@<Initialize table entries...@>= +Prote_mode=0; /*initially we are in compatibility mode*/ + +@ @<Dump the \Prote\ state@>= +dump_int(Prote_mode); + +@ @<Undump the \Prote\ state@>= +undump(0, 1, Prote_mode); + +@ In order to not clobber the global scope with variables that are +locally used, the initializations for \Prote, if the mode is +activated, are done in a dedicated procedure. These are not part of +what is dumped. + +@<Last-minute procedures@>= +static void Prote_initialize(void) +{@+int k; /*all-purpose index*/ +@<\Prote\ initializations@>; +} + +@ There are commands and command modifiers, these command modifiers +maybe encoding too a type. So we must not step on each other toes. + +@ When we are adding primitives that deal intimately with the variables +of \TeX, in the |eqtb| regions (in our case regions 5 for integers, and +6 for dimensions), the command modifier to the various +\.{assign\_*} classes is simply the address. So we have interpolated +our added variables above since this is done by the way of WEB +pre-processing. + +@ For the conditional primitives, the way is straightforward. + +@d if_incsname_code (eTeX_last_if_test_cmd_mod+1) /* `\.{\\ifincsname}' */ +@d if_primitive_code (eTeX_last_if_test_cmd_mod+2) /* `\.{\\ifprimitive}' */ +@ The |last_item| class is for secondary internal values, that can be +dereferenced by \.{\\the} but are read-only and are mainly related to +the value of a current state or are such values but their assignation +shall trigger an action, and we shall not hook in the \.{assign\_*} +processing. + +The command modifiers for the |last_item| class were, originally, +encoding too the type of the item (see m.410). But \eTeX\ has added its +extensions and we won't try to be smart: the type |cur_val_level| will +be set by switching between contiguous ranges of values of the same +type. + +And we will define here all the instances of |last_item| that we add +in order to keep our number assignations gathered. + +@d Prote_version_code (eTeX_last_last_item_cmd_mod+1) + /*code for \.{\\Proteversion}*/ +@d random_seed_code (eTeX_last_last_item_cmd_mod+2) /* \.{\\randomseed} */ +@d elapsed_time_code (eTeX_last_last_item_cmd_mod+3) /* \.{\\elapsedtime} */ +@d shell_escape_code (eTeX_last_last_item_cmd_mod+4) /* \.{\\shellescape} */ +@d last_xpos_code (eTeX_last_last_item_cmd_mod+5) /* \.{\\lastxpos} */ +@d last_ypos_code (eTeX_last_last_item_cmd_mod+6) /* \.{\\lastypos} */ + +@ The \.{convert} class is for conversion of some external stuff to put +it, as a token list, into the scanner. It is not an internal value that +could be dereferenced by \.{\\the} and it is obviously not settable: it +expands to the token list. + +@d Prote_revision_code (eTeX_last_convert_cmd_mod+1) /* \.{\\Proterevision}*/ +@d strcmp_code (eTeX_last_convert_cmd_mod+2) /* \.{\\strcmp} */ +@d set_random_seed_code (eTeX_last_convert_cmd_mod+3) /* \.{\\setrandomseed} */ +@d normal_deviate_code (eTeX_last_convert_cmd_mod+4) /* \.{\\normaldeviate} */ +@d uniform_deviate_code (eTeX_last_convert_cmd_mod+5) /* \.{\\uniformdeviate} */ +@d creation_date_code (eTeX_last_convert_cmd_mod+6) /* \.{\\creationdate} */ +@d file_size_code (eTeX_last_convert_cmd_mod+7) /* \.{\\filesize} */ +@d file_mod_date_code (eTeX_last_convert_cmd_mod+8) /* \.{\\filemodedate} */ +@d file_dump_code (eTeX_last_convert_cmd_mod+9) /* \.{\\filedump} */ +@d mdfive_sum_code (eTeX_last_convert_cmd_mod+10) /* \.{\\mdfivesum} */ +@d Prote_last_convert_code mdfive_sum_code + +@ When modifying the meaning of something---in this case, for now, +switching to the primitive meaning if it exists---or modifying the +way expansion is done, it seems that it can be thought as a special +case of expansion, hence a variant of |expand_after|. + +@d primitive_code (eTeX_last_expand_after_cmd_mod+1) /* `\.{\\primitive}' */ +@d expanded_code (eTeX_last_expand_after_cmd_mod+2) /* `\.{\\expanded}' */ +@ When the primitive manipulate something really external, whether +trying to insert something in the output format---\.{DVI} for +us---or dealing with the system, it doesn't fit in any cmd group and +could be called an exception. So it will be a variant of the |extension| +cmd group. + +\eTeX\ didn't add new primitives to the extension command group, so we +add a related macro, equal to |TeX_last_extension_cmd_mod|, simply so +that it is locally obvious. + +@d eTeX_last_extension_cmd_mod TeX_last_extension_cmd_mod /*none added*/ +@d reset_timer_code (eTeX_last_extension_cmd_mod+1) /* `\.{\\resettimer}' */ +@d save_pos_code (eTeX_last_extension_cmd_mod+2) /* `\.{\\savepos}' */ + +@*1 Identifying \Prote. + +We will start by giving a mean to test that \Prote\ is activated and +to identify the version. + +@<Generate all \Prote\ primitives@>= +if (!pdf_on) { +primitive("Proteversion", last_item, Prote_version_code); +@!@:Prote\_version\_}{\.{\\Proteversion} primitive@> +primitive("Proterevision", convert, Prote_revision_code);@/ +@!@:Prote\_revision\_}{\.{\\Proterevision} primitive@> +} +@ We use the different hooks added to insert our cases. + +@<Cases of |last_item| for |print_cmd_chr|@>= +case Prote_version_code: print_esc("Proteversion");@+break; + +@ @<Cases for fetching a \Prote\ int value@>= +case Prote_version_code: cur_val=Prote_version;@+break; + +@ @<Cases of |convert| for |print_cmd_chr|@>= +case Prote_revision_code: print_esc("Proterevision");@+break; + +@ @<Cases of `Scan the argument for command |c|'@>= +case Prote_revision_code: do_nothing;@+break; + +@ @<Cases of `Print the result of command |c|'@>= +case Prote_revision_code: print(Prote_revision);@+break; + +@*1 \Prote\ added token lists routines. + +We will, more than once, convert a general normally expanded text +to a string. Due to the unfelicity of \PASCAL\ about forward +declarations of functions, we declare procedures that do their task +by defining global variables. In this case, |garbage| is used. + +|link(garbage)| will hold the pointer to the head of the token list, +|info(garbage)| to the tail. If the two are equals, then the list is +empty. The routine making a string will take |link(garbage)| and +put the number in |info(garbage)|. + +@ The first procedure scan a general text (normally) expanded. The +head of the reference count is returned in |link(garbage)|, the +tail in |info(garbage)| and if the two are equals, the list is empty. +User must keep in mind that this has to be flushed when done with! + +@<Forward declarations@>= +static void scan_general_x_text(void); + +@ @<Declare \Prote\ procedures for token lists@>= +static void scan_general_x_text(void) +{@+pointer d; /*to save |def_ref|*/ +d=def_ref;info(garbage)=scan_toks(false, true); +link(garbage)=def_ref; +def_ref=d; /*restore whatever*/ +} + +@ The second procedure takes a token list defined in |link(garbage)| +and converts it to a string number that is returned in |info(garbage)|. +Neither the token list nor the string (obviously) are flushed. + +@<Forward declarations@>= +static void toks_to_str(void); + +@ Here we are using |token_show| that has to take a reference count. + +@<Declare \Prote\ procedures for token lists@>= +static void toks_to_str(void) +{@+int old_setting; /*holds |selector| setting*/ +old_setting=selector;selector=new_string; + token_show(link(garbage));selector=old_setting; + str_room(1); /*flirting with the limit means probably truncation*/ + info(garbage)=make_string(); +} + +@*1 \Prote\ added strings routines. + +The next procedure sets |name_of_file| from the string given as an +argument, mimicking the |input| primitive by adding an |.tex| extension +if there is none. It silently truncates if the length of the string +exceeds the size of the name buffer and doesn't use |cur_area| and +|cur_ext|, but |name_length| is set to the real name length (without +truncating) so a test about |k <= file_name_size| allows to detect the +impossibility of opening the file without having to call external code. +The string is not flushed: it is the responsability of the code calling +the procedure to flush it if wanted. + +@<Declare \Prote\ procedures for strings@>= +static void str_to_name(str_number @!s) +{@+int k; /*number of positions filled in |name_of_file|*/ +ASCII_code @!c; /*character being packed*/ +int @!j; /*index into |str_pool|*/ +k=0;for (j=str_start[s]; j<=str_start[s+1]-1; j++) {@+ + c=so(str_pool[j]);incr(k); + if (k <= file_name_size) name_of_file[k]=xchr[c]; + } +name_length=k; +name_of_file[name_length+1]=0; +} + +@*1 Exchanging data with external routines. + +In order to try to sever external handling from our core, we +introduce an all purpose exchange buffer |xchg_buffer|, that will +be an array of bytes (these can be interpreted as \.{text\_char} +or \.{ASCII\_char} or \.{eight\_bits}). + +The data to be used starts at index $1$ and ends at index +|xchg_buffer_length|. + +For the moment, this buffer must accommodate a numerical MD5 +hash value, i.e. $16$ bytes long; will also be used to exchange $64$ +bytes chunks to feed MD5 hash generation, and will have to accommodate +too the maximal size of the date returned by \.{\\creationdate} or +\.{\\filemoddate} that is $23$ \.{text\_char}. So at least $64$ for now. + +@<Global...@>= +static eight_bits @!xchg_buffer0[xchg_buffer_size], + *const @!xchg_buffer = @!xchg_buffer0-1; + /*exchange buffer for interaction with system routines*/ +static int @!xchg_buffer_length; /*last valid index in this buf; 0 means no data*/ +@ @<Check \Prote\ ``constant'' values for consistency@>= +if (xchg_buffer_size < 64) bad=51; + +@ When there is data in the exchange buffer, the length of the data has +to be set. When an external routine has consumed the data, it shall +reset the length to $0$. + +@<\Prote\ initializations@>= +xchg_buffer_length=0; + +@*1 \Prote\ states. + +\.{\\shellescape} depends on a pdf\TeX\ feature, namely the ability to +escape to shell. There is no such thing in \Prote. So it expands to $0$. +Note: this a status primitive; it does not allow to set the status but +simply expands to a read-only integer reflecting it. In \Prote, it is +always $0$. + +@<Generate all \Prote\ primitives@>= +if (pdf_on) { +primitive("pdfshellescape", last_item, shell_escape_code); +@!@:pdfshellescape\_}{\.{\\pdfshellescape} primitive@> +} else { primitive("shellescape", last_item, shell_escape_code); +@!@:shellescape\_}{\.{\\shellescape} primitive@> +} + +@ @<Cases of |last_item| for |print_cmd_chr|@>= +case shell_escape_code: + if (pdf_on) print_esc("pdfshellescape"); + else print_esc("shellescape"); + @+break; + +@ @<Cases for fetching a \Prote\ int value@>= +case shell_escape_code: cur_val=0;@+break; + +@*1 \Prote\ conditionals. + +We add the following conditionals, that are susceptible of the same +expansion rules as the other |if_test| ones. + +@<Generate all \Prote\ primitives@>= +primitive("ifincsname", if_test, if_incsname_code); +@!@:if\_incsname\_}{\.{\\if} primitive@> +if (pdf_on) +primitive("ifpdfprimitive", if_test, if_primitive_code); +@!@:if\_pdfprimitive\_}{\.{\\if} pdfprimitive@> +else primitive("ifprimitive", if_test, if_primitive_code); +@!@:if\_primitive\_}{\.{\\if} primitive@> + + +@ @<Cases of |if_test| for |print_cmd_chr|@>= +case if_incsname_code: print_esc("ifincsname");@+break; +case if_primitive_code: + if (pdf_on) print_esc("ifpdfprimitive"); + else print_esc("ifprimitive"); + @+break; + +@ The conditional \.{\\ifincsname} is simple since we increment a global +variable |incsname_state| when we enter the \.{\\csname} command and +decrement it when we have reached and passed the \.{\\endcsname}---a +scope depth index. + +@<\Prote\ initializations@>= +incsname_state=0; + +@ @<Cases for |conditional|@>= +case if_incsname_code: b=(incsname_state > 0);@+break; + +@ The conditional \.{\\ifprimitive} is true when the following control +sequence is a primitive; false otherwise. |id_lookup| can return +|undefined_control_sequence| (for a control sequence not entered in the +hash since |no_new_control_sequence| is |true|), but since it has the +\.{eq\_type} set to |undefined_cs|, the test of this latter works as +for a control sequence entered but never defined. + +@ @<Cases for |conditional|@>= +case if_primitive_code: {@+@/do@+{get_token();}@+ while (!(cur_tok!=space_token)); +if ((cur_cs!=0)&&(cur_cmd!=undefined_cs)&&(cur_cmd < call)) b=true;else b=false; +} @+break; + +@*1 \Prote\ primitives changing definition or expansion. + +The next primitives, here, are more involved since they are whether +changing the definition of a control sequence, or modifying how the +tokens will be treated. + +@ Since a user level control sequence can give a new definition to a +primitive, the \.{primitive}... primitive, if the argument is a control +sequence whose name is the name of a primitive, will make this primitive +meaning the meaning of the control sequence {\it hic et nunc}. If there +was no primitive meaning, no error is raised and nothing is changed. +It can be seen as a kind of \.{expand\_after} command since it is in the +external handling of the token list creation. + +Since we need to redefine the token and hence give a valid control +sequence in the |eqtb|, we have defined |frozen_primitive|. This +``frozen'' is, actually, not quite frozen by itself since we will +redefine its values according to the primitive definition we have +to restablish momentarily. But it is indeed ``permanent'' since +it only refers to the permanently defined meanings. Hence, the +initialization of the |frozen_primitive| address is just to document +the code: these values will be overwritten on each actual call. + +@<Generate all \Prote\ primitives@>= +if (pdf_on) +primitive("pdfprimitive", expand_after, primitive_code); +@!@:pdfprimitive\_}{\.{\\pdfprimitive} primitive@> +else +primitive("primitive", expand_after, primitive_code); +@!@:primitive\_}{\.{\\primitive} primitive@> +text(frozen_primitive)=text(cur_val);eqtb[frozen_primitive]=eqtb[cur_val]; + +@ @<Cases of |expandafter| for |print_cmd_chr|@>= +case primitive_code: + if (pdf_on) print_esc("pdfprimitive"); + else print_esc("primitive"); + @+break; + +@ The problem is that the primitives are added at |level_one| and that a +redefinition as a macro at this same level by a user simply overwrites +the definition. We need then to keep these definitions. + +Primitives are only added by \.{INITEX}. So we can consider what we will +call a |ROM|, since it can be only ``flashed'' by \.{INITEX} and is +read-only afterwards, a kind of BIOS table holding initial system calls +(primitives). + +Since primitives are not macros (they don't need to expand or to +evaluate parameters since their definition is directly in the code), +the definition of a primitive is a couple: the command class (|cur_cmd|) +and the modifier (|cur_chr|) to distinguish between the cases---the +instances. But since, at the user level, a primitive is identified by +its name, and that a redefinition is, mandatorily, a homonym, the +location of the macro shadowing the primitive is at the same address as +was the primitive in the |eqtb|. So in order to speed-up the check, we +should organize things so that the address in the |eqtb| of a control +sequence (one character or multiletter) can be readily +converted in an address in the |ROM| array. + +This array will be an array of memory word, of type |two_halves|, in +order to re-use the macro definitions set for the table of equivalents. + +The one character primitives are added by direct addressing relative to +|single_base|. The multiletter primitives are added starting at +|frozen_control_sequence-1|, downwards; but there are only, at the +moment, $322$ multileter primitives defined by \TeX, $78$ such +primitives defined by \eTeX, and we are adding $24$ more. It is clear +that, looking at primitives, region 2 of |eqtb| is really a sparse array +and that, when |hash_size| is increased for format needs, there will be +a fair amount of space wasted if we simply copy, in fact, second part +of region 1 and region 2 in the |ROM|. + +Yes, but it is simpler as a first approach---premature optimization is +the root of all evil. So a simple translation scheme will be enough. + +The index in |ROM| will start at $1$ and will go up to $256 + 1 + +hash\_size$, that is a simple translation from |single_base| to +|ROM_base|, but only for addresses of interest, the other pointing to +an |ROM_undefined_primitive| that will allow an easy test. + +@d ROM_base 1 +@d ROM_size (256+1+hash_size) /*256 oc, undefined and ml*/ +@d ROM_undefined_primitive 257 +@d ROM_type_field(A) A.hh.b0 +@d ROM_equiv_field(X) X.hh.rh +@d ROM_type(A) ROM_type_field(ROM[A]) /*command code for equivalent*/ +@d set_ROM_p_from_cs(A) if ((A >= single_base) + &&(A < frozen_control_sequence)) + p=A-single_base+ROM_base; + else p=ROM_undefined_primitive + +@<Global...@>= +static memory_word @!ROM0[ROM_size-ROM_base+1], + *const @!ROM = @!ROM0-ROM_base; + +@ Even if it will be unused in \TeX\ or \eTeX\ modes, we will initialize +it since we add code to the |primitive| procedure and we need \TeX\ +and \eTeX\ ones to be registered as well, whether \.{INITEX} switches to +\Prote\ mode later or not. + +@<Initialize table entries...@>= +ROM[ROM_undefined_primitive]=eqtb[undefined_control_sequence]; +for (k=ROM_base; k<=256; k++) ROM[k]=ROM[ROM_undefined_primitive]; +for (k=ROM_undefined_primitive+1; k<=ROM_size; k++) + ROM[k]=ROM[ROM_undefined_primitive]; + +@ When a primitive is added---and this only happens in \.{INITEX}---we +have to define the corresponding address in the \.{ROM}. + +@ |cur_val| has the pointer in second part of region 1 or in region 2 +of |eqtb|. + +@<Add primitive definition to the |ROM| array@>= +set_ROM_p_from_cs(cur_val); +ROM[p]=eqtb[cur_val]; + +@ This array has to be dumped since it is only defined by \.{INITEX}. It +is always dumped even if it is unused unless in \Prote\ mode. + +@<Dump the |ROM| array@>= +for (k=ROM_base; k<=ROM_size; k++) dump_wd(ROM[k]); + +@ And what has been dumped shall be undumped. + +@<Undump the |ROM| array@>= +for (k=ROM_base; k<=ROM_size; k++) undump_wd(ROM[k]); + +@ Once all this is done, the processing of \.{\\primitive} is simple: +we read the next token that has to be a control sequence. If this +control sequence belongs to region 1 or 2 and is defined in |ROM|, we +redefine the token to be the |frozen_primitive| control sequence, +redefining its codes from the |ROM| and setting the text associated for +printing purposes. If not, the token is unchanged. Then we put back the +token so that it will be processed again, maybe redefined. + +@<Cases for |expandafter|@>= +case primitive_code: {@+get_token(); +set_ROM_p_from_cs(cur_cs); +if ((p!=ROM_undefined_primitive)&&(ROM_type(p)!=undefined_cs)) {@+ + eqtb[frozen_primitive]=ROM[p]; + text(frozen_primitive)=text(cur_cs); + cur_tok=cs_token_flag+frozen_primitive; + } +back_input(); +} @+break; + +@ The next primitive changes the expansion of its argument that is like +a general text expanded, except that protected macros (an \eTeX\ +extension) are not extanded. + +@ @<Generate all \Prote\ primitives@>= +primitive("expanded", expand_after, expanded_code);@/ +@!@:expanded\_}{\.{\\expanded} primitive@> + +@ @<Cases of |expandafter| for |print_cmd_chr|@>= +case expanded_code: print_esc("expanded"); + +@ This intervenes in |expand| and we must substitute a token list to our +current token, putting it back for further reprocessing. + +@<Cases for |expandafter|@>= +case expanded_code: {@+scan_general_x_text(); + back_list(link(link(garbage))); + free_avail(link(garbage)); /*drop reference count*/ + } + +@*1 \Prote\ strings related primitives. + +The primitive \.{\\strcmp} text two parameters that are general text +without expansion. The two token lists created are converted to strings +and this couple of strings is then compared, character by character. If +the first string is lexicographically sorted before the second, the +expansion is $-1$; if the two strings are equal, the expansion is $0$; +if the first string is lexicographically sorted after the second, the +expansion is $1$. + +@<Generate all \Prote\ primitives@>= +if (pdf_on) +primitive("pdfstrcmp", convert, strcmp_code);@/ +@!@:pdf\_strcmp\_}{\.{\\pdfstrcmp} primitive@> +else +primitive("strcmp", convert, strcmp_code); +@!@:strcmp\_}{\.{\\strcmp} primitive@> + + +@ @<Cases of |convert| for |print_cmd_chr|@>= +case strcmp_code: + if (pdf_on) print_esc("pdfstrcmp"); + else print_esc("strcmp"); + @+break; + +@ It should be noted that the strings comparison is \TeX\ strings +comparison: the arguments are subject to the manipulation done when +scanning a general text (squeezing non escaped blanks), and the +characters are converted according to the |xord| array. Thus it is +an |ASCII_code|---in the \TeX\ sense explained at the very beginning +of the web file, part 2---comparison and the result is the same, +as long as relative characters are mapped to the same value, whatever +the system. Nul strings are valid. + +@<Cases of `Scan the argument for command |c|'@>= +case strcmp_code: @<Scan the argument for |strcmp_code|@>@;@+break; + +@ @<Scan the argument for |strcmp_code|@>= +{@+scan_general_x_text();toks_to_str(); + s=info(garbage);flush_list(link(garbage)); + scan_general_x_text();toks_to_str(); + t=info(garbage);flush_list(link(garbage)); + if ((length(s)==0)&&(length(t)==0)) cur_val=0; + else if (length(s)==0) cur_val=-1; + else if (length(t)==0) cur_val=1; + else{@+m=str_start[s];n=str_start[t];r=false; + while ((!r)&&(m < str_start[s+1])&&(n < str_start[t+1])) {@+ + cur_val=str_pool[m]-str_pool[n];if (cur_val!=0) r=true; + incr(m);incr(n); + } + if (cur_val==0) {@+if (length(s)!=length(t)) + if (m!=str_start[s+1]) cur_val=1;else cur_val=-1; + } + else cur_val=cur_val/(double)abs(cur_val); + } + flush_string;flush_string; + } + +@ @<Cases of `Print the result of command |c|'@>= +case strcmp_code: print_int(cur_val);@+break; + +@*1 \Prote\ date and time related primitives. + +The following primitives are related to the time elapsed since a +defined moment in time. The creation date is fixed at the moment when +|fix_date_and_time| has been called and stays fixed afterwards. This +moment is also, by default, the reference moment for computing the time +elapsed. + +@ The creation date is retrieved by the \.{\\creationdate} primitive. As +explained above, the date corresponds to the moment when +|fix_date_and_time| was called taking into account |FORCE_SOURCE_DATE| +and |SOURCE_DATE_EPOCH| (see above, m.241). If the creation date is +forced, the string will be UTC related. + +The format of the string is |D: YYYYMMDDHHmmSSOHH"mm"|, `O' being the +relationship of local time to UT, that is `-' (minus), `+' or `Z'; +HH followed by a single quote being the absolute value of the offset +from UT in hours (00--23), mm followed by a single quote being the +absolute value of the offset from UT in minutes (00--59). All fields +after the year are optional and default to zero values. + +@ @<Generate all \Prote\ primitives@>= +if (!pdf_on) +primitive("pdfcreationdate", convert, creation_date_code);@/ +@!@:pdf\_creation\_date\_}{\.{\\pdfcreationdate} primitive@> +else +primitive("creationdate", convert, creation_date_code);@/ +@!@:creationdate\_}{\.{\\creationdate} primitive@> + + +@ @<Cases of |convert| for |print_cmd_chr|@>= +case creation_date_code: + if (pdf_on) print_esc("pdfcreationdate"); + else print_esc("creationdate"); + @+break; + +@ |get_creation_date| has to be provided by the system. +@^system dependencies@> + +@<Cases of `Scan the argument for command |c|'@>= +case creation_date_code: get_creation_date();@+break; + +@ The date is in the |time_str| so we have simply to convert the +characters. + +@<Cases of `Print the result of command |c|'@>= +case creation_date_code: for (k=0; time_str[k]!='\0'; k++) + print_char(time_str[k]);@+break; + +@ The time elapsed is a scaled integer the unit being scaled seconds, +i.e. $1/65536$ of a second. Since our scaled integers have a +defined range, the value can not reach or pass, in plain seconds, +$32767$. + +The elapsed time returned is relative to some defined moment. At +start, the reference moment is the time the date was set for +|fix_date_and_time|. This requires system support and the default +implementation here will then fix this moment at noon on 4 July 1776 +and what would be returned by the function is here simply defined by +a macro: with this reference time and this basic code, |infinity| is +the permanent answer. +@^system dependencies@> + +@d get_elapsed_time infinity /*a function should be implemented*/ + +@ @<Generate all \Prote\ primitives@>= +if (pdf_on) { +primitive("pdfresettimer", extension, reset_timer_code);@/ +@!@:reset\_timer\_}{\.{\\pdfresettimer} primitive@> +primitive("pdfelapsedtime", last_item, elapsed_time_code); +@!@:elapsed\_time\_}{\.{\\pdfelapsedtime} primitive@> +} else { +primitive("resettimer", extension, reset_timer_code);@/ +@!@:resettimer\_}{\.{\\resettimer} primitive@> +primitive("elapsedtime", last_item, elapsed_time_code);@/ +@!@:elapsedtime\_}{\.{\\elapsedtime} primitive@> +} + +@ @<Cases of |last_item| for |print_cmd_chr|@>= +case elapsed_time_code: + if (pdf_on) print_esc("pdfelapsedtime"); + else print_esc("elapsedtime"); + @+break; + +@ @<Cases of |extension| for |print_cmd_chr|@>= +case reset_timer_code: + if (pdf_on) print_esc("pdfresettimer"); + else print_esc("resettimer"); + @+break; + +@ @<Cases for fetching a \Prote\ int value@>= +case elapsed_time_code: + { double t=(start_sec*1.0+start_nsec/1000000000.0-reset_timer)*0x10000; + if (t>=infinity) cur_val=infinity; + else cur_val=(scaled)t; + @+break; + } + +@ The reference moment can be reset by a call to the primitive +\.{\\resettimer}. It simply resets the reference moment to the moment +the primitive was called. The counter is not regularily incremented. +When asked about the time elapsed what is returned is the difference, in +scaled seconds, from the moment of the call to the moment of reference. +So there is no persistent variable neither a kind of clock implemented. +@^system dependencies@> + +Since we maintain the time anyway, we implement the timing function. +@<Glob...@>= +static double reset_timer=0.0; /*time of the last reset in seconds*/ + + +@ Since to reset the timer a simple call to the routine is necessary, +we simply add it to \.{main\_control} by adding it to the cases handled +by \.{do\_extension}. It contributes nothing to the token list: it is a +``fire and forget'', so no need to handle the special \.{subtype} in the +other hooks. + +@<Cases for |do_extension|@>= +case reset_timer_code: reset_timer=start_sec*1.0+start_nsec/1000000000.0;@+break; + +@*1 \Prote\ file related primitives. + +The presence of the following primitives in the engine can be +questioned. Since they are very external, and their implementation, for +example in C, requires things that are not in the C standard (the +date of modification of the file, for example). So these should not be +multiplied. + +@ The \.{\\filesize} primitive expands to the size, in bytes, of the +file. + +@<Generate all \Prote\ primitives@>= +if (pdf_on) +primitive("pdffilesize", convert, file_size_code);@/ +@!@:pdf\_file\_size\_}{\.{\\pdffilesize} primitive@> +else +primitive("filesize", convert, file_size_code); +@!@:filesize\_}{\.{\\filesize} primitive@> + + +@ @<Cases of |convert| for |print_cmd_chr|@>= +case file_size_code: + if (pdf_on) print_esc("pdffilesize"); + else print_esc("filesize"); + @+break; + +@ In order to be able to treat the problem when trying to open the file, +we open here and pass the file pointer, if success, to a dedicated +function in order to get its size. In case of problem, nothing is +returned. +@^system dependencies@> + +@<Cases of `Scan the argument for command |c|'@>= +case file_size_code: @<Scan the argument for |file_size_code|@>@;@+break; + +@ @<Scan the argument for |file_size_code|@>= +{@+scan_general_x_text();toks_to_str(); + s=info(garbage);flush_list(link(garbage));str_to_name(s); + cur_val=-1; /*invalid value if error*/ + cur_val=get_file_size(); + flush_string; +} + +@ @<Cases of `Print the result of command |c|'@>= +case file_size_code: if (cur_val!=-1) print_int(cur_val);@+break; + +@ The \.{\\filemoddate} expands to a date with the same format as the +creation date (see \.{\\creationdate}). + +@<Generate all \Prote\ primitives@>= +if (pdf_on) +primitive("pdffilemoddate", convert, file_mod_date_code);@/ +@!@:pdf\_file\_mod\_date\_}{\.{\\pdffilemoddate} primitive@> +else +primitive("filemoddate", convert, file_mod_date_code); +@!@:filemoddate\_}{\.{\\filemoddate} primitive@> + + +@ @<Cases of |convert| for |print_cmd_chr|@>= +case file_mod_date_code: + if (pdf_on) print_esc("pdffilemoddate"); + else print_esc("filemoddate"); + @+break; + +@ For getting the argument, the treatment resembles that of +\.{\\filesize} obviously, since it is only the type of information +returned that changes. The availability of this information in system +dependent. The information shall be set in |xchg_buffer|. +@^system dependencies@> + +In this basic implementation, we set the string to the empty one by +simply setting |xchg_buffer_length| to $0$. + +@d get_file_mtime xchg_buffer_length=0 + +@<Cases of `Scan the argument for command |c|'@>= +case file_mod_date_code: @<Scan the argument for |file_mod_date_code|@>@;@+break; + +@ @<Scan the argument for |file_mod_date_code|@>= +{@+scan_general_x_text();toks_to_str(); + s=info(garbage);flush_list(link(garbage));str_to_name(s); + get_file_mod_date(); + flush_string; +} @+break; + +@ Printing the result consists simply in printing every +|text_char| in |time_str|. +If the length is $0$, nothing is printed. + +@<Cases of `Print the result of command |c|'@>= +case file_mod_date_code: for (k=0; time_str[k]!='\0'; k++) + print_char(time_str[k]);@+break; + +@ The primitive \.{\\filedump} expands to the dump of the first + \.{length} bytes of the file, starting from \.{offset}. Offset and +length are optional integers given, in that order, introduced resp. +by the keywords ``offset'' and ``length''. If not specified, they +default to $0$. A length of $0$ expands to nothing (it is not an error). +The file name is given as a |general text|. + +@<Generate all \Prote\ primitives@>= +if (pdf_on) +primitive("pdffiledump", convert, file_dump_code);@/ +@!@:pdf\_file\_dump\_}{\.{\\pdffiledump} primitive@> +else +primitive("filedump", convert, file_dump_code); +@!@:filedump\_}{\.{\\filedump} primitive@> + + +@ @<Cases of |convert| for |print_cmd_chr|@>= +case file_dump_code: + if (pdf_on) print_esc("pdffiledump"); + else print_esc("filedump"); + @+break; + +@ The scanning of the arguments is obvious from the syntax above. + +Since ``offset'' and ``length'' may be given in that order, we assign +the variables \.{k} and \.{l}, in alphabetical order. These have to be +positive or nul values. + +Contrary to other blocks, and for optimization purposes (in order not to +clobber the string pool with data that we can read, when necessary, one +byte at a time), \.{k}, \.{l} and \.{f} will be defined here and used +when printing. + +@<Cases of `Scan the argument for command |c|'@>= +case file_dump_code: @<Scan the argument for |file_dump_code|@>@;@+break; + +@ @<Scan the argument for |file_dump_code|@>= +{@+k=0;l=0; /*defaults*/ + if (scan_keyword("offset")) {@+scan_int(); + if (cur_val < 0) {@+print_err("Bad ");print_esc("filedump"); +@.Bad \\filedump@> + help2("I allow only nonnegative values here.",@/ + "I changed this one to zero.");int_error(cur_val); + } + else k=cur_val; + } + if (scan_keyword("length")) {@+scan_int(); + if (cur_val < 0) {@+print_err("Bad ");print_esc("filedump"); +@.Bad \\filedump@> + help2("I allow only nonnegative values here.",@/ + "I changed this one to zero.");int_error(cur_val); + } + else l=cur_val; + } + scan_general_x_text();toks_to_str();s=info(garbage); + flush_list(link(garbage));str_to_name(s); + flush_string; /*this one was the filename argument*/ + } + +@ The variables have been set, and the file name has been defined. We +simply print the uppercase hexadecimal transcription of every byte +requested before closing the file. Here we deal with bytes +(\.{eight\_bits} values) so there is no transcription. + +@<Cases of `Print the result of command |c|'@>= +case file_dump_code: + { FILE *f=fopen((char*)name_of_file0,"rb"); + if (f!=NULL) {@+ + fseek(f,k,SEEK_SET); + do@+{i=fgetc(f); if (i==EOF) break; + dig[0]=i%16;dig[1]=i/16; + print_the_digs(2);decr(l); + }@+ while (!(feof(f)||(l==0))); + fclose(f); + } + } @+break; + +@ The \.{\\mdfivesum} is obviously a variant of the \.{convert} class since +it takes values from external and put them as a token list in the +stream. + +@<Generate all \Prote\ primitives@>= +if (pdf_on) +primitive("pdfmdfivesum", convert, mdfive_sum_code);@/ +@!@:pdf\_mdfive\_sum\_}{\.{\\pdfmdfivesum} primitive@> +else +primitive("mdfivesum", convert, mdfive_sum_code); +@!@:mdfivesum\_}{\.{\\mdfivesum} primitive@> + + +@ @<Cases of |convert| for |print_cmd_chr|@>= +case mdfive_sum_code: + if (pdf_on) print_esc("pdfmdfivesum"); + else print_esc("mdfivesum"); + @+break; + +@ There is an optional keyword "file" that will tell us if the | < general +text > | is to be taken as a filename or just as the string to hash. The +| < balanced text > | is expanded in both cases. + +Once this is done, we ask to init the MD5 state; then fill the exchange +buffer with chunks of data and update the MD5 hash with every chunk +until source is exhausted and ask for the final ($16$ bytes numerical +value) result that will be put in the |xchg_buffer|. + +Since we are looking for a ``general text'', that must be enclosed (at +least: ended; the opening brace can be implicit) by a |right_brace|, +an error will be caught with runaways. + +The general text is converted to a string. It is legal to have an empty +string if the argument is not a file. + +@<Cases of `Scan the argument for command |c|'@>= +case mdfive_sum_code: @<Scan the argument for |mdfive_sum_code|@>@; @+break; + +@ @<Scan the argument for |mdfive_sum_code|@>= +{@+r=scan_keyword("file");scan_general_x_text(); +toks_to_str();s=info(garbage);flush_list(link(garbage)); +l=get_md5_sum(s,r); +flush_string; /*done with the filename or string to hash*/ +} + +@ As a result, there is $16$ bytes in the |md5_digest| representing the +MD5 hash. We simply print, byte by byte, the uppercase hexadecimal +representation of this hash. + +@<Cases of `Print the result of command |c|'@>= +case mdfive_sum_code: for (k=0; k<l; k++) +{@+dig[0]=md5_digest[k]%16;@+dig[1]=md5_digest[k]/16;print_the_digs(2); +} @+break; + +@*1 Pseudo-random number generation. + +These routines come from John Hobby's \MP\ and generate pseudo-random +numbers with the additive scheme recommended in Section 3.6 of +{\sl The Art of Computer Programming}; however, the results are +random fractions between 0 and |mpfract_one-1|, inclusive. + +\MP\ uses 28~significant bits of precision and we have kept this in +order for the routines to behave the same way as in \MP. So the name +|mpfract| will be used instead of |scaled|, while the two are integers, +in the range defined by \TeX. + +@d double(A) A=A+A /*multiply a variable by two*/ +@d halfp(A) (A)/2 /*when quantity is known to be positive or zero*/ + +@ The subroutines for logarithm and exponential involve two tables. +The first is simple: |two_to_the[k]| equals $2^k$. The second involves +a bit more calculation, which the author claims to have done correctly: +|spec_log[k]| is $2^{27}$ times $\ln\bigl(1/(1-2^{-k})\bigr)= +2^{-k}+{1\over2}2^{-2k}+{1\over3}2^{-3k}+\cdots\,$, rounded to the +nearest integer. + +@<Glob...@>= +static int @!two_to_the[31]; /*powers of two*/ +static int @!spec_log0[28], *const @!spec_log = @!spec_log0-1; /*special logarithms*/ + +@ @<\Prote\ initializations@>= +two_to_the[0]=1; +for (k=1; k<=30; k++) two_to_the[k]=2*two_to_the[k-1]; +spec_log[1]=93032640; +spec_log[2]=38612034; +spec_log[3]=17922280; +spec_log[4]=8662214; +spec_log[5]=4261238; +spec_log[6]=2113709; +spec_log[7]=1052693; +spec_log[8]=525315; +spec_log[9]=262400; +spec_log[10]=131136; +spec_log[11]=65552; +spec_log[12]=32772; +spec_log[13]=16385; +for (k=14; k<=27; k++) spec_log[k]=two_to_the[27-k]; +spec_log[28]=1; + +@ Here is the routine that calculates $2^8$ times the natural logarithm +of a |scaled| quantity; it is an integer approximation to $2^{24}\ln(x/2^{16})$, +when |x| is a given positive integer. + +The method is based on exercise 1.2.2--25 in {\sl The Art of Computer +Programming\/}: During the main iteration we have $1\L 2^{-30}x<1/(1-2^{1-k})$, +and the logarithm of $2^{30}x$ remains to be added to an accumulator +register called~$y$. Three auxiliary bits of accuracy are retained in~$y$ +during the calculation, and sixteen auxiliary bits to extend |y| are +kept in~|z| during the initial argument reduction. (We add +$100\cdot2^{16}=6553600$ to~|z| and subtract 100 from~|y| so that |z| will +not become negative; also, the actual amount subtracted from~|y| is~96, +not~100, because we want to add~4 for rounding before the final division by~8.) + +@<Declare \Prote\ arithmetic routines@>= +static scaled m_log(scaled @!x) +{@+int @!y, @!z; /*auxiliary registers*/ +int @!k; /*iteration counter*/ +if (x <= 0) @<Handle non-positive logarithm@>@; +else{@+y=1302456956+4-100; /*$14\times2^{27}\ln2\approx1302456956.421063$*/ + z=27595+6553600; /*and $2^{16}\times .421063\approx 27595$*/ + while (x < mpfract_four) + {@+double(x);y=y-93032639;z=z-48782; + } /*$2^{27}\ln2\approx 93032639.74436163$ + and $2^{16}\times.74436163\approx 48782$*/ + y=y+(z/unity);k=2; + while (x > mpfract_four+4) + @<Increase |k| until |x| can be multiplied by a factor of $2^{-k}$, and +adjust $y$ accordingly@>; + return y/8; + } +} + +@ @<Increase |k| until |x| can...@>= +{@+z=((x-1)/two_to_the[k])+1; /*$z=\lceil x/2^k\rceil$*/ +while (x < mpfract_four+z) + {@+z=halfp(z+1);k=k+1; + } +y=y+spec_log[k];x=x-z; +} + +@ @<Handle non-positive logarithm@>= +{@+print_err("Logarithm of "); +@.Logarithm...replaced by 0@> +print_scaled(x);print(" has been replaced by 0"); +help2("Since I don't take logs of non-positive numbers,",@/ + "I'm zeroing this one. Proceed, with fingers crossed."); +error();return 0; +} + +@ Here is introduced the special 28bits significand |mpfract|. + +@d el_gordo 017777777777 /*$2^{31}-1$, the largest value that \TeX\ likes*/ +@d mpfract_half 01000000000 /*$2^{27}$, represents 0.50000000*/ +@d mpfract_one 02000000000 /*$2^{28}$, represents 1.00000000*/ +@d mpfract_four 010000000000 /*$2^{30}$, represents 4.00000000*/ + +@<Types...@>= +typedef int mpfract; /*this type is used for pseudo-random numbers*/ + +@ The |make_mpfract| routine produces the |mpfract| equivalent of +|p/(double)q|, given integers |p| and~|q|; it computes the integer +$f=\lfloor2^{28}p/q+{1\over2}\rfloor$, when $p$ and $q$ are +positive. If |p| and |q| are both of the same scaled type |t|, +the ``type relation'' |make_mpfract(t, t)==mpfract| is valid; +and it's also possible to use the subroutine ``backwards,'' using +the relation |make_mpfract(t, mpfract)==t| between scaled types. + +If the result would have magnitude $2^{31}$ or more, |make_mpfract| +sets |arith_error=true|. Most of \TeX's internal computations have +been designed to avoid this sort of error. + +If this subroutine were programmed in assembly language on a typical +machine, we could simply compute |(@t$2^{28}$@>*p)/q|, since a +double-precision product can often be input to a fixed-point division +instruction. But when we are restricted to \PASCAL\ arithmetic it +is necessary either to resort to multiple-precision maneuvering +or to use a simple but slow iteration. The multiple-precision technique +would be about three times faster than the code adopted here, but it +would be comparatively long and tricky, involving about sixteen +additional multiplications and divisions. + +The present implementation is highly portable, but slow; it avoids +multiplication and division except in the initial stage. But since it is +not part of \TeX\ inner loop, it doesn't matter. + +@<Declare \Prote\ arithmetic routines@>= +static mpfract make_mpfract(int @!p, int @!q) +{@+int @!f; /*the fraction bits, with a leading 1 bit*/ +int @!n; /*the integer part of $\vert p/q\vert$*/ +bool @!negative; /*should the result be negated?*/ +int @!be_careful; /*disables certain compiler optimizations*/ +if (p >= 0) negative=false; +else{@+negate(p);negative=true; + } +if (q <= 0) + { +#ifdef @!DEBUG +if (q==0) confusion("/");@; +#endif +@;@/ +@:this can't happen /}{\quad \./@> + negate(q);negative=!negative; + } +n=p/q;p=p%q; +if (n >= 8) + {@+arith_error=true; + if (negative) return-el_gordo;@+else return el_gordo; + } +else{@+n=(n-1)*mpfract_one; + @<Compute $f=\lfloor 2^{28}(1+p/q)+{1\over2}\rfloor$@>; + if (negative) return-(f+n);@+else return f+n; + } +} + +@ The |@/do@+{| loop here preserves the following invariant relations +between |f|, |p|, and~|q|: +(i)~|0 <= p < q|; (ii)~$fq+p=2^k(q+p_0)$, where $k$ is an integer and +$p_0$ is the original value of~$p$. + +Notice that the computation specifies +|(p-q)+p| instead of |(p+p)-q|, because the latter could overflow. +Let us hope that optimizing compilers do not miss this point; a +special variable |be_careful| is used to emphasize the necessary +order of computation. Optimizing compilers should keep |be_careful| +in a register, not store it in memory. +@^inner loop@> + +@<Compute $f=\lfloor 2^{28}(1+p/q)+{1\over2}\rfloor$@>= +f=1; +@/do@+{be_careful=p-q;p=be_careful+p; +if (p >= 0) f=f+f+1; +else{@+double(f);p=p+q; + } +}@+ while (!(f >= mpfract_one)); +be_careful=p-q; +if (be_careful+p >= 0) incr(f) + +@ The dual of |make_mpfract| is |take_mpfract|, which multiplies a +given integer~|q| by a fraction~|f|. When the operands are positive, it +computes $p=\lfloor qf/2^{28}+{1\over2}\rfloor$, a symmetric function +of |q| and~|f|. + +@<Declare \Prote\ arithmetic routines@>= +static int take_mpfract(int @!q, mpfract @!f) +{@+int @!p; /*the fraction so far*/ +bool @!negative; /*should the result be negated?*/ +int @!n; /*additional multiple of $q$*/ +int @!be_careful; /*disables certain compiler optimizations*/ +@<Reduce to the case that |f>=0| and |q>0|@>; +if (f < mpfract_one) n=0; +else{@+n=f/mpfract_one;f=f%mpfract_one; + if (q <= el_gordo/n) n=n*q; + else{@+arith_error=true;n=el_gordo; + } + } +f=f+mpfract_one; +@<Compute $p=\lfloor qf/2^{28}+{1\over2}\rfloor-q$@>; +be_careful=n-el_gordo; +if (be_careful+p > 0) + {@+arith_error=true;n=el_gordo-p; + } +if (negative) return-(n+p); +else return n+p; +} + +@ @<Reduce to the case that |f>=0| and |q>0|@>= +if (f >= 0) negative=false; +else{@+negate(f);negative=true; + } +if (q < 0) + {@+negate(q);negative=!negative; + } + +@ The invariant relations in this case are (i)~$\lfloor(qf+p)/2^k\rfloor +=\lfloor qf_0/2^{28}+{1\over2}\rfloor$, where $k$ is an integer and +$f_0$ is the original value of~$f$; (ii)~$2^k\L f<2^{k+1}$. +@^inner loop@> + +@<Compute $p=\lfloor qf/2^{28}+{1\over2}\rfloor-q$@>= +p=mpfract_half; /*that's $2^{27}$; the invariants hold now with $k=28$*/ +if (q < mpfract_four) + @/do@+{if (odd(f)) p=halfp(p+q);@+else p=halfp(p); + f=halfp(f); + }@+ while (!(f==1)); +else@/do@+{if (odd(f)) p=p+halfp(q-p);@+else p=halfp(p); + f=halfp(f); + }@+ while (!(f==1)) + +@ There's an auxiliary array |randoms| that contains 55 pseudo-random +fractions. Using the recurrence $x_n=(x_{n-55}-x_{n-31})\bmod 2^{28}$, +we generate batches of 55 new $x_n$'s at a time by calling |new_randoms|. +The global variable |j_random| tells which element has most recently +been consumed. + +@<Glob...@>= +static mpfract @!randoms[55]; /*the last 55 random values generated*/ +static int @!j_random; /*the number of unused |randoms|*/ + +@ This array of pseudo-random numbers is set starting from a seed value, +that is kept in the global integer |random_seed|. + +@<Global...@>= +static int @!random_seed; /*seed for pseudo-random number generation*/ + +@ @<Generate all \Prote\ primitives@>= +if (pdf_on) +primitive("pdfrandomseed", last_item, random_seed_code); +@!@:random\_seed\_}{\.{\\pdfrandomseed} primitive@> +else +primitive("randomseed", last_item, random_seed_code);@/ +@!@:randomseed\_}{\.{\\randomseed} primitive@> + + +@ @<Cases of |last_item| for |print_cmd_chr|@>= +case random_seed_code: + if (pdf_on) print_esc("pdfrandomseed"); + else print_esc("randomseed"); + @+break; + +@ @<Cases for fetching a \Prote\ int value@>= +case random_seed_code: cur_val=random_seed;@+break; + +@ We set the initial value from the system time. System integrators +could provide a better source of pseudo-randomness. + +Every time a new seed value is assigned, the array has to be +regenerated for consumption by routines explained a little later. + +@<\Prote\ initializations@>= +random_seed=sys_time; +init_randoms(); + +@ Since changing the value must trigger the redefinition of the array, +a dedicated primitive is defined to take the new seed and call +|init_randoms|. + +@<Generate all \Prote\ primitives@>= +if (pdf_on) +primitive("pdfsetrandomseed", convert, set_random_seed_code);@/ +@!@:set\_random\_seed\_code}{\.{\\pdfsetrandomseed} primitive@> +else +primitive("setrandomseed", convert, set_random_seed_code);@/ +@!@:setrandomseed\_}{\.{\\setrandomseed} primitive@> + + +@ @<Cases of |convert| for |print_cmd_chr|@>= +case set_random_seed_code: + if (pdf_on) print_esc("pdfsetrandomseed"); + else print_esc("setrandomseed"); + @+break; + +@ Once we have retrieved and redefined |random_seed|, we must regenerate +the |randoms| array. + +@<Cases of `Scan the argument for command |c|'@>= +case set_random_seed_code: {@+scan_int();random_seed=cur_val; + init_randoms(); + } @+break; + +@ @<Cases of `Print the result of command |c|'@>= +case set_random_seed_code: print_int(random_seed);@+break; + +@ To consume a random fraction, the program below will say `|next_random|' +and then it will fetch |randoms[j_random]|. + +@d next_random if (j_random==0) new_randoms(); + else decr(j_random) + +@<Declare \Prote\ arithmetic routines@>= +static void new_randoms(void) +{@+int @!k; /*index into |randoms|*/ +int @!x; /*accumulator*/ +for (k=0; k<=23; k++) + {@+x=randoms[k]-randoms[k+31]; + if (x < 0) x=x+mpfract_one; + randoms[k]=x; + } +for (k=24; k<=54; k++) + {@+x=randoms[k]-randoms[k-24]; + if (x < 0) x=x+mpfract_one; + randoms[k]=x; + } +j_random=54; +} + +@ To initialize the |randoms| table, we call the following routine. + +@<Declare \Prote\ arithmetic routines@>= +static void init_randoms(void) +{@+mpfract @!j, @!jj, @!k; /*more or less random integers*/ +int @!i; /*index into |randoms|*/ +j=abs(random_seed); +while (j >= mpfract_one) j=halfp(j); +k=1; +for (i=0; i<=54; i++) + {@+jj=k;k=j-k;j=jj; + if (k < 0) k=k+mpfract_one; + randoms[(i*21)%55]=j; + } +new_randoms();new_randoms();new_randoms(); /*``warm up'' the array*/ +} + +@ To produce a uniform random number in the range |0 <= u < x| or |0 >= u > x| +or |0==u==x|, given a |scaled| value~|x|, we proceed as shown here. + +Note that the call of |mult_integers| will produce the values 0 and~|x| +with about half the probability that it will produce any other particular +values between 0 and~|x|, because it rounds its answers. + +@<Declare \Prote\ arithmetic routines@>= +static scaled unif_rand(scaled @!x) +{@+scaled @!y; /*trial value*/ +next_random;y=take_mpfract(abs(x), randoms[j_random]); +if (y==abs(x)) return 0; +else if (x > 0) return y; +else return-y; +} + +@ This can be used by calling the following primitive. + +@<Generate all \Prote\ primitives@>= +if (pdf_on) +primitive("pdfuniformdeviate", convert, uniform_deviate_code);@/ +@!@:uniform\_deviate\_}{\.{\\pdfuniformdeviate} primitive@> +else +primitive("uniformdeviate", convert, uniform_deviate_code);@/ +@!@:uniformdeviate\_}{\.{\\uniformdeviate} primitive@> + + +@ @<Cases of |convert| for |print_cmd_chr|@>= +case uniform_deviate_code: + if (pdf_on) print_esc("pdfuniformdeviate"); + else print_esc("uniformdeviate"); + @+break; + +@ It takes one integer argument obviously that will be the argument +to the function. + +@<Cases of `Scan the argument for command |c|'@>= +case uniform_deviate_code: {@+scan_int(); + cur_val=unif_rand(cur_val); + } @+break; + +@ @<Cases of `Print the result of command |c|'@>= +case uniform_deviate_code: print_int(cur_val);@+break; + +@ The following somewhat different subroutine tests rigorously if $ab$ is +greater than, equal to, or less than~$cd$, +given integers $(a,b,c,d)$. In most cases a quick decision is reached. +The result is $+1$, 0, or~$-1$ in the three respective cases. + +@d return_sign(A) {@+return A; + } + +@<Declare \Prote\ arithmetic routines@>= +static int ab_vs_cd(int @!a, int b, int c, int d) +{@+ +int @!q, @!r; /*temporary registers*/ +@<Reduce to the case that |a,c>=0|, |b,d>0|@>; +loop@+{@+q=a/d;r=c/b; + if (q!=r) + if (q > r) return_sign(1)@;@+else return_sign(-1); + q=a%d;r=c%b; + if (r==0) + if (q==0) return_sign(0)@;@+else return_sign(1); + if (q==0) return_sign(-1); + a=b;b=q;c=d;d=r; + } /*now |a > d > 0| and |c > b > 0|*/ +} + +@ @<Reduce to the case that |a...@>= +if (a < 0) + {@+negate(a);negate(b); + } +if (c < 0) + {@+negate(c);negate(d); + } +if (d <= 0) + {@+if (b >= 0) + if (((a==0)||(b==0))&&((c==0)||(d==0))) return_sign(0)@; + else return_sign(1); + if (d==0) + if (a==0) return_sign(0)@;@+else return_sign(-1); + q=a;a=c;c=q;q=-b;b=-d;d=q; + } +else if (b <= 0) + {@+if (b < 0) if (a > 0) return_sign(-1); + if (c==0) return_sign(0)@;else return_sign(-1); + } + +@ Finally, a normal deviate with mean zero and unit standard deviation +can readily be obtained with the ratio method (Algorithm 3.4.1R in +{\sl The Art of Computer Programming\/}). + +@<Declare \Prote\ arithmetic routines@>= +static scaled norm_rand(void) +{@+int @!x, @!u, @!l; /*what the book would call $2^{16}X$, $2^{28}U$, + and $-2^{24}\ln U$*/ +@/do@+{ + @/do@+{next_random; + x=take_mpfract(112429, randoms[j_random]-mpfract_half); + /*$2^{16}\sqrt{8/e}\approx 112428.82793$*/ + next_random;u=randoms[j_random]; + }@+ while (!(abs(x) < u)); +x=make_mpfract(x, u); +l=139548960-m_log(u); /*$2^{24}\cdot12\ln2\approx139548959.6165$*/ +}@+ while (!(ab_vs_cd(1024, l, x, x) >= 0)); +return x; +} + +@ This can be used by calling the following primitive. + +@<Generate all \Prote\ primitives@>= +if (pdf_on) +primitive("pdfnormaldeviate", convert, normal_deviate_code);@/ +@!@:normal\_deviate\_}{\.{\\pdfnormaldeviate} primitive@> +else +primitive("normaldeviate", convert, normal_deviate_code);@/ +@!@:normaldeviate\_}{\.{\\normaldeviate} primitive@> + + +@ @<Cases of |convert| for |print_cmd_chr|@>= +case normal_deviate_code: + if (pdf_on) print_esc("pdfnormaldeviate"); + else print_esc("normaldeviate"); + @+break; + + +@ @<Cases of `Scan the argument for command |c|'@>= +case normal_deviate_code: cur_val=norm_rand();@+break; + +@ @<Cases of `Print the result of command |c|'@>= +case normal_deviate_code: print_int(cur_val);@+break; + +@*1 DVI related primitives. + +These primitives are related to positions in the DVI output. + +The \TeX\ and DVI system coordinates relate to an origin that is at the +upper left corner. The \TeX\ coordinates are computed relative to an +origin that has $(0,0)$ coordinates. Coordinates grow then rightward and +downward. This is the {\sl page} coordinates relative to what is +typeset (what \TeX\ is dealing with). + +But this typesetting material has to be put on what we will call {\sl +paper}. The material put into shape by \TeX\ is put on the paper. On +this paper, where will be put the \TeX\ origin? It is considered to be +$1in$ at the right and $1in$ down from the upper left corner of the +paper (see m.590, alinea 2). + +@d DVI_std_x_offset 4736286 /*1 inch in sp*/ +@d DVI_std_y_offset 4736286 /*1 inch in sp*/ + +@ But the paper size is not specified in the DVI file and is not being +dealt with by \TeX. + +In order to have a common reference point, and since the \.{\\lastxpos} +and \.{\\lastypos} primitives originated in pdf\TeX, these two +primitives give positions, in scaled points, relative to the lower left +corner of the paper. + +Hence the need, for these primitive, to define the paper size, with the +(misnamed) \.{\\pagewidth} and \.{\\pageheight}. + +\.{\\pagewidth} and \.{\\pageheight} are dimension parameters, +initialized to $0$ by the generic \TeX\ code. + +@<Generate all \Prote\ primitives@>= +if (!pdf_on) { +primitive("pdfpagewidth", assign_dimen, dimen_base+page_width_code);@/ +@!@:pdf\_page\_width\_}{\.{\\pdfpagewidth} primitive@> +primitive("pdfpageheight", assign_dimen, dimen_base+page_height_code);@/ +@!@:pdf\_page\_height\_}{\.{\\pdfpageheight} primitive@> +} else { +primitive("pagewidth", assign_dimen, dimen_base+page_width_code);@/ +@!@:pagewidth\_}{\.{\\pagewidth} primitive@> +primitive("pageheight", assign_dimen, dimen_base+page_height_code);@/ +@!@:pageheight\_}{\.{\\pageheight} primitive@> +} + + + +@ When instructed to, the \.{h} and \.{v} last values are transformed, +in the coordinates system defined above and saved in the global +variables |last_saved_xpos| and |last_saved_ypos|. They are +initialized to $0$ and we do not make any verification that a +call to the \.{\\savepos} primitive---to come---has been made before +retrieving their values. + +@<Global...@>= +static scaled @!last_saved_xpos, last_saved_ypos; /*last (x,y) DVI pos saved*/ + +@ @<\Prote\ initializations@>= +last_saved_xpos=0;last_saved_ypos=0; + +@ @<Set |last_saved_xpos| and |last_saved_ypos| with transformed coordinates@>= +last_saved_xpos=cur_h+DVI_std_x_offset; +last_saved_ypos=page_height-(cur_v+DVI_std_y_offset); + +@ @<Generate all \Prote\ primitives@>= +if (!pdf_on) { +primitive("pdflastxpos", last_item, last_xpos_code);@/ +@!@:pdflastxpos\_}{\.{\\pdflastxpos} primitive@> +primitive("lastypos", last_item, last_ypos_code);@/ +@!@:pdflastypos\_}{\.{\\pdflastypos} primitive@> +} else { +primitive("lastxpos", last_item, last_xpos_code);@/ +@!@:lastxpos\_}{\.{\\lastxpos} primitive@> +primitive("lastypos", last_item, last_ypos_code);@/ +@!@:lastypos\_}{\.{\\lastypos} primitive@> +} + +@ @<Cases of |last_item| for |print_cmd_chr|@>= +case last_xpos_code: + if (pdf_on) print_esc("pdflastxpos"); + else print_esc("lastxpos"); + @+break; +case last_ypos_code: + if (pdf_on) print_esc("pdflastypos"); + else print_esc("lastypos"); + @+break; + +@ @<Cases for fetching a \Prote\ int value@>= +case last_xpos_code: cur_val=last_saved_xpos;@+break; +case last_ypos_code: cur_val=last_saved_ypos; + +@ |last_saved_xpos| and |last_saved_ypos| are only defined when +instructed to by the call the the \.{\\savepos} primitive. Since the +real work has to be done at \.{shipout} time, it is a case to be treated +like the \.{\\special} primitive, that is it belongs to the +\.{extension} class. + +We will add something more in the handling of the primitive: it will +insert a \.{whatsit} in the DVI file so that one, using the program +|dvitype|, could retrieve more than one {\it hic}. So there is a counter +incremented whenever the primitive is called. + +@<Global...@>= +static int last_save_pos_number; /*identifying the order of the call*/ + +@ @<\Prote\ initializations@>= +last_save_pos_number=0; /*i.e. none*/ + +@ @<Generate all \Prote\ primitives@>= +if (pdf_on) +primitive("pdfsavepos", extension, save_pos_code);@/ +@!@:pdf\_save\_pos\_}{\.{\\pdfsavepos} primitive@> +else +primitive("savepos", extension, save_pos_code);@/ +@!@:savepos\_}{\.{\\savepos} primitive@> + + +@ @<Cases of |extension| for |print_cmd_chr|@>= +case save_pos_code: + if (pdf_on) print_esc("pdfsavepos"); + else print_esc("savepos"); + @+break; +@ @<Cases for |do_extension|@>= +case save_pos_code: @<Implement \.{\\savepos}@>@;@+break; + +@ We need the basic two words node, since we don't pass any parameter +and it is just an instruction to do something. So the \.{whatsit} node +is just the call. + +@<Implement \.{\\savepos}@>= +{@+new_whatsit(save_pos_code, small_node_size);write_stream(tail)=null; + write_tokens(tail)=null; + } + +@ @<Cases for displaying the |whatsit| node@>= +case save_pos_code: + if (pdf_on) print_esc("pdfsavepos"); + else print_esc("savepos"); + @+break; +@ @<Cases for making a partial copy of the whatsit node@>= +case save_pos_code: {@+r=get_node(small_node_size); + words=small_node_size; + } @+break; + +@ @<Cases for wiping out the whatsit node@>= +case save_pos_code: free_node(p, small_node_size);@+break; + +@ So, after these trivial initializations, what will we effectively do? +When the following procedure will be called, we define |last_saved_xpos|, +|last_saved_ypos|, increment |last_save_pos_number|, and a |warning| +followed by three +|key==value| space separated definitions as a \.{\\special}, the first +being prefixed by the string |__PROTE_| (shall be considered a reserved +prefix) and the string |SAVEPOS_|, equal to the index of the call, and +the |XPOS| and |YPOS| definitions. + +This is obviously, from the previous description, a variation around +|special_out|. + +@<Declare procedures needed in |out_what|@>= +static void save_pos_out(pointer @!p) +{@+int old_setting; /*holds print |selector|*/ +int @!k; /*index into |str_pool|*/ +synch_h;synch_v;incr(last_save_pos_number); +@<Set |last_saved_xpos| and |last_saved_ypos|...@>@; +old_setting=selector;selector=new_string; +print("warning __PROTE_");print("SAVEPOS");print_char('='); +print_int(last_save_pos_number);print_char(' '); +print("XPOS");print("=");print_int(last_saved_xpos);print_char(' '); +print("YPOS");print("=");print_int(last_saved_ypos); +selector=old_setting; +str_room(1); /*abort if probably overflowed and truncated*/ +dvi_out(xxx1);dvi_out(cur_length); /*it's less than 256*/ +for (k=str_start[str_ptr]; k<=pool_ptr-1; k++) dvi_out(so(str_pool[k])); +pool_ptr=str_start[str_ptr]; /*forget the not commited tentative string*/ +} + +@ @<Cases for |out_what|@>= +case save_pos_code: save_pos_out(p);@+break; + +@* System-dependent changes. +This section should be replaced, if necessary, by any special +modifications of the program +that are necessary to make \TeX\ work at a particular installation. +It is usually best to design your change file so that all changes to +previous sections preserve the section numbering; then everybody's version +will be consistent with the published program. More extensive changes, +which introduce new sections, can be inserted here; then only the index +itself will get a new section number. +@^system dependencies@> + +@* \TeX\ Live Integration. +A \TeX\ engine that aspires +to become a member of the \TeX\ Live family of programs +must + +$-$ respect the \TeX\ Live conventions for command line parameters,\par +$-$ find its input files using the \.{kpathsearch} library, and\par +$-$ implement \TeX\ primitives to support +\LaTeX. + +\noindent Naturally, the functions that follow here are taken, with small +modifications, from the \TeX\ Live sources. What is +added here, or rather subtracted here, are the parts that are specific +to some of the \TeX\ engines included in \TeX\ Live. New is also +that the code is presented in literate programming style. + +The code that follows is organized in three parts. +Some code for \TeX\ Live must come before +the definition of \TeX's macros because +it uses include files containing identifiers that are in conflict +with \TeX's macros or modify these macros. For example +\TeX's |banner| is modified by adding the \TeX\ Live version. + +@<Header files and function declarations@>= +#ifdef WEB2CVERSION +#define TL_VERSION "(TeX Live "WEB2CVERSION")" +#else +#define TL_VERSION +#endif + +@ The remaining two parts are first auxiliary variables and functions and then +those functions that are called from the ``classic'' \TeX\ code. + +@p @<\TeX\ Live auxiliary variables@>@; + @<\TeX\ Live auxiliary functions@>@; + @<\TeX\ Live functions@>@; + +@ +Most of the code that we present next comes together in the +function |main_init| +which is the first function called in the main program of a \TeX\ engine +belonging to \TeX\ Live. Before doing so, we make copies of +argument count and argument vector putting them in global variables. +@<Global...@>= +static char **argv; +static int argc; + +@ @<\TeX\ Live functions@>= +static void main_init(int ac, char *av[]) +{@+ + char* main_input_file; + argc = ac; + argv = av; + interaction = error_stop_mode; + kpse_record_input = recorder_record_input; + kpse_record_output = recorder_record_output; + + @<parse options@>@; + @<set the program and engine name@>@; + @<activate configuration lines@>@; + @<set the input file name@>@; + @<set defaults from the {\tt texmf.cfg} file@>@; + @<set the format name@>@; + @<enable the generation of input files@>@; +} + +@ @<Forward declarations@>= +static void main_init(int ac, char *av[]); + + +@*1 Command Line. + Let's begin with the beginning: the command line. +To see how a command line is structured, we first look at the +help text that is displayed if the user asks for it (or if \TeX\ +decides that the user needs it). The help text is produced by the +function |usage_help|. +\def\SP{ }% disable visible spaces in strings. + +@<\TeX\ Live auxiliary functions@>= +static void usage_help(void) +{@+@<explain the command line@>@; + fprintf(stdout,"Options:\n"@,@[@<explain the options@>@]); + fprintf(stdout,"\nFor further information and reporting bugs see https://hint.userweb.mwn.de/\n"); + exit(0); +} + +@ The command line comes in three slightly different versions: + +@<explain the command line@>= + fprintf(stdout,@/ + "Usage: %s [OPTION]... [TEXNAME[.tex]] [COMMANDS]\n"@/ + " or: %s [OPTION]... \\FIRST-LINE\n"@/ + " or: %s [OPTION]... &FMT ARGS\n\n",@/ + argv[0],argv[0],argv[0]);@/ + fprintf(stdout,@/ + " Run TeX on TEXNAME, creating TEXNAME.dvi.\n"@/ + " Any remaining COMMANDS are processed\n"@/ + " as TeX input after TEXNAME is read.\n"@/ + " If the first line of TEXNAME starts with %%&FMT, and FMT is\n"@/ + " an existing .fmt file, use it. Else use `NAME.fmt', where\n"@/ + " NAME is the program invocation name.\n"@/ + "\n"@/ + " Alternatively, if the first non-option argument begins\n"@/ + " with a backslash, interpret all non-option arguments as\n"@/ + " a line of TeX input.\n"@/ + "\n"@/ + " Alternatively, if the first non-option argument begins\n"@/ + " with a &, the next word is taken as the FMT to read,\n"@/ + " overriding all else. Any remaining arguments are\n"@/ + " processed as above.\n"@/ + "\n"@/ + " If no arguments or options are specified, prompt for input.\n"@/ + "\n"); + + +@*1 Options. +Here is the list of possible options and their explanation: + +@<explain the options@>= + " -help "@/ + @t\qquad@>"\t display this help and exit\n"@/ + " -version "@/ + @t\qquad@>"\t output version information and exit\n"@/ + " -etex "@/ + @t\qquad@>"\t enable e-TeX extensions\n"@/ + " -ltx "@/ + @t\qquad@>"\t enable LaTeX extensions, implies -etex\n"@/ + " -ini "@/ + @t\qquad@>"\t be initex for dumping formats; this is\n"@/ + @t\qquad@>"\t\t\t also true if the program name is `kinitex'\n"@/ + " -progname=STRING "@/ + @t\qquad@>"\t set program (and fmt) name to STRING\n"@/ + " -fmt=FMTNAME "@/ + @t\qquad@>"\t use FMTNAME instead of program name or a %%& line\n"@/ + " -output-directory=DIR "@/ + @t\qquad@>"\t use existing DIR as the directory to write files to\n"@/ + " -jobname=STRING "@/ + @t\qquad@>"\t set the TeX \\jobname to STRING\n"@/ + " [-no]-mktex=FMT "@/ + @t\qquad@>"\t disable/enable mktexFMT generation (FMT=tex/tfm/fmt)\n"@/ + " -interaction=STRING "@/ + @t\qquad@>"\t set interaction mode (STRING=batchmode/\n"@/ + @t\qquad@>"\t\t\t nonstopmode/scrollmode/errorstopmode)\n"@/ + " -kpathsea-debug=NUMBER"@/ + @t\qquad@>"\t set path searching debugging flags according\n"@/ + @t\qquad@>"\t\t\t to the bits of NUMBER\n"@/ + " -recorder"@/ + @t\qquad@>"\t\t enable filename recorder\n"@/ + " [-no]-parse-first-line"@/ + @t\qquad@>"\t disable/enable parsing of the first line of\n"@/ + @t\qquad@>"\t\t\t the input file\n"@/ + " [-no]-file-line-error"@/ + @t\qquad@>"\t disable/enable file:line:error style\n"@/ + " -cnf-line=STRING"@/ + @t\qquad@>"\t process STRING like a line in texmf.cnf\n"@/ + + +@ The processing of command line options is controlled by the |long_options| +\def\SP{{\tt\char`\ }}% restore the visible space in a string +array. Each entry in this array contains first the name of the option, +then a flag that tells whether the option takes an argument or not. +If next the (optional) address of a flag variable is given, +it is followed by the value to store in the flag variable. +In this case, setting the flag variable is handled by +the |getopt_long_only| function. + +Besides the flag variables that occur in the table, +a few string variables may be set using the options. +The following is a complete list of these variables. +Variables are initialized with |-1| to indicate an undefined value; +string variables are initialized with |NULL|. + +@<Global variables@>= +static int iniversion=false, etexp=false, ltxp=false, recorder_enabled=false; +static int parsefirstlinep=-1, filelineerrorstylep=-1, interaction_option=-1; +static const char *user_progname=NULL, *output_directory=NULL, *c_job_name=NULL, + *dump_name=NULL;@# + +@ @<\TeX\ Live auxiliary variables@>= +static struct option long_options[] = {@/ + { "help", 0, 0, 0 },@/ + { "version", 0, 0, 0 },@/ + { "interaction", 1, 0, 0 },@/ + { "mktex", 1, 0, 0 },@/ + { "no-mktex", 1, 0, 0 },@/ + { "kpathsea-debug", 1, 0, 0 },@/ + { "progname", 1, 0, 0 },@/ + { "fmt", 1, 0, 0 },@/ + { "output-directory", 1, 0, 0 },@/ + { "jobname", 1, 0, 0 },@/ + { "cnf-line", 1, 0, 0 },@/ + { "ini", 0, &iniversion, 1 },@/ + { "etex", 0, &etexp, 1 },@/ + { "ltx", 0, <xp, 1 },@/ + { "recorder", 0, &recorder_enabled, 1 },@/ + { "parse-first-line", 0, &parsefirstlinep, 1 },@/ + { "no-parse-first-line", 0, &parsefirstlinep, 0 },@/ + { "file-line-error", 0, &filelineerrorstylep, 1 },@/ + { "no-file-line-error", 0, &filelineerrorstylep, 0 },@/ + @<more options@>@/ + { 0, 0, 0, 0 }@+}@+; + + +@ Parsing the command line options is accomplished with the +|parse_options| function which in turn uses the |getopt_long_only| +function from the \CEE/ library. This function returns 0 and sets the +|option_index| parameter to the option found, or it returns $-1$ if +the end of all options is reached. +@<\TeX\ Live functions@>= +static void parse_options (int argc, char *argv[]) +{@+ while (true) { + int option_index; + int g = getopt_long_only (argc, argv, "+", long_options, &option_index); + if (g==0) + { @<handle the options@>@;@+ } + else if (g == '?') + { fprintf(stderr,"Try '%s --help' for more information\n",argv[0]); + exit(1); + } + else if (g == -1) break; + } + @<Check the environment for extra settings@>@; +} + +@ @<Forward declarations@>= +static void parse_options (int argc, char *argv[]); + +@ Before we can call the |parse_options| function, +we might need some special preparations for Windows. + +@<parse options@>= +#if defined(WIN32) +{@+ char* enc; + kpse_set_program_name (argv[0], NULL); + enc = kpse_var_value("command_line_encoding"); + get_command_line_args_utf8(enc, &argc, &argv);@/ + parse_options (argc, argv); + @<record {\tt texmf.cnf}@>@; +} +#else + parse_options (ac, av); +#endif + + +@ To handle the options, we compare the name at the given |option_index| with +the different option names. This is not a very efficient method, but the +impact is low and it's simple to write. + +Comparing the name of the argument with the |name| field in the |option| +structure is done in the auxiliary function |argument_is|. +Unfortunately the |name| field is in conflict with the |name| macro +defined by \TeX. To avoid the conflict, the |argument_is| function +goes just after the \.{kpathsea.h} header file that defines +the option structure. + + +@<Header files and function declarations@>= +#include <kpathsea/kpathsea.h> +static int argument_is(struct option *opt, char * s) +{@+ return STREQ(opt->name, s); @+} +#define ARGUMENT_IS(S) argument_is(long_options+option_index,S) + +@ Now we can handle the first two options: + +@<handle the options@>= +if (ARGUMENT_IS("help")) usage_help(); +else if (ARGUMENT_IS("version")){@+ + printf(TeX_banner@, "\n"@/ + "Prote version "@, Prote_version_string@, "\n"); + exit(0);@+ +} + + +@ The ``interaction'' option sets the |interaction_option| variable +based on its string argument contained in the |optarg| variable. +If defined, the |interaction_option| will be used to set \TeX's +|interaction| variable in the |initialize| and the |undump| functions. + +@<handle the options@>= +else @+if (ARGUMENT_IS ("interaction"))@t\2@> { + if (STREQ (optarg, "batchmode")) interaction_option = batch_mode; + else if (STREQ (optarg, "nonstopmode")) interaction_option = nonstop_mode; + else if (STREQ (optarg, "scrollmode")) interaction_option = scroll_mode; + else if (STREQ (optarg, "errorstopmode")) interaction_option = error_stop_mode; + else WARNING1 ("Ignoring unknown argument `%s' to --interaction", optarg); + } + +@ The next two options pass the string argument to the +\.{kpathsearch} library. + +@<handle the options@>= +else @+if (ARGUMENT_IS ("mktex")) @t\2@> kpse_maketex_option (optarg, true); +else if (ARGUMENT_IS ("no-mktex")) kpse_maketex_option (optarg, false); + + +@ To debug the searching done by the \.{kpathsearch} library, +the following option can be used. +The argument value 3 is a good choice to start with. + +@<handle the options@>= +else @+if (ARGUMENT_IS ("kpathsea-debug")) @t\2@> + kpathsea_debug |= atoi (optarg); + + + +@ The next set of options take a string argument +and assign it to the corresponding string variable. + +@<handle the options@>= +else @+if (ARGUMENT_IS ("progname"))@t\2@> + user_progname = normalize_quotes(optarg,"program name"); +else if (ARGUMENT_IS ("fmt")) + dump_name = normalize_quotes(optarg,"format name"); +else if (ARGUMENT_IS ("output-directory")) + output_directory = normalize_quotes(optarg,"output directory"); +else if (ARGUMENT_IS ("jobname")) + c_job_name = normalize_quotes (optarg, "job name"); + +@ When string arguments specify files or directories, +special care is needed if arguments are quoted and/or contain spaces. +The function |normalize_quotes| makes sure that arguments containing +spaces get quotes around them and it checks for unbalanced quotes. + + +@<\TeX\ Live auxiliary functions@>= +static char *normalize_quotes (const char *nom, const char *mesg) +{@+ int quoted = false; + int must_quote = (strchr(nom, ' ') != NULL); + char *ret = xmalloc(strlen(nom)+3);/*room for two quotes and NUL*/ + char *p=ret; + const char *q; + + if (must_quote) + *p++ = '"'; + for (q = nom; *q; q++) + if (*q == '"') + quoted = !quoted;@+ + else + *p++ = *q; + + if (must_quote) + *p++ = '"'; + *p = '\0'; + if (quoted) { + fprintf(stderr, "! Unbalanced quotes in %s %s\n", mesg, nom); + exit(1); + } + return ret; +} + +@ If the output directory was specified on the command line, +we save it in an environment variable so that subbrocesses can +get the value. If on the other hand the environment specifies +a directory and the command line does not, save the value from +the environment to the global variable so that it is used in the +rest of the code. + +@<Check the environment for extra settings@>= +if (output_directory) + xputenv ("TEXMF_OUTPUT_DIRECTORY", output_directory); +else if (getenv ("TEXMF_OUTPUT_DIRECTORY")) + output_directory = getenv ("TEXMF_OUTPUT_DIRECTORY"); + +@*1 Passing a file name as a general text argument. + +|scan_file_name| uses the following code to parse a file name given +as a general text argument. Such an argument can be any token list +starting with a left brace and ending with a right brace. +This token list is then expanded (without the leading and trailing braces) +and printed into the string pool without making it yet an official string. +After removing all double quotes, because this is current practice +for \TeX\ engines that are part of \TeX\ Live, +and setting the area and extension delimiters, +all temporary garbage used so far is freed. + +Due to the expansion of the token list, this code and hence the +|scan_file_name| procedure is recursive. +One can provide the name of a file as the content of an other file. + + +% Thierry Laronde +@<Define a general text file name and |goto done|@>= +{@+back_input();name_in_progress=false; /*this version is recursive...*/ + cur_cs=input_loc; /*|scan_toks| will set |warning_index| from it*/ + scan_general_x_text(); + old_setting=selector;selector=new_string; + token_show(link(garbage));selector=old_setting; + @<Suppress double quotes in braced input file name@>@; + j=pool_ptr-1;while ((j >= str_start[str_ptr])&&(area_delimiter==0)) + {@+ + if ((str_pool[j]=='/')) area_delimiter=j-str_start[str_ptr]; + if ((ext_delimiter==0)&&(str_pool[j]=='.')) + ext_delimiter=j-str_start[str_ptr]; + decr(j); + } + flush_list(link(garbage)); + goto done; +} + +@ A simple loop removes the double quotes and adjusts the |pool_ptr|. + +@<Suppress double quotes in braced input file name@>= +for (k=j=str_start[str_ptr]; k < pool_ptr; k++) {@+ + if (str_pool[k]!='"') {@+str_pool[j]=str_pool[k];incr(j);} +} +pool_ptr=j; + +@*1 The {\tt -recorder} Option. +The recorder option can be used to enable the file name recorder. +It is crucial for getting a reliable list of files used in a given run. +Many post-processors use it, and it is used in \TeX\ Live for +checking the format building infrastructure. + +When we start the file name recorder, +we would like to use mkstemp, but it is not portable, +and doing the autoconfiscation (and providing fallbacks) is more +than we want to cope with. So we have to be content with using a +default name. We throw in the pid so at least parallel builds might +work. Windows, however, seems to have no |pid_t|, so instead of storing the +value returned by |getpid|, we immediately consume it. + +@<\TeX\ Live auxiliary functions@>= +static char *recorder_name=NULL; +static FILE *recorder_file=NULL; +static void +recorder_start(void) +{ char *cwd; + char pid_str[MAX_INT_LENGTH]; + sprintf (pid_str, "%ld", (long) getpid()); + recorder_name = concat3(kpse_program_name, pid_str, ".fls"); + if (output_directory) { + char *temp = concat3(output_directory, DIR_SEP_STRING, recorder_name); + free(recorder_name); + recorder_name = temp; + } + recorder_file = xfopen(recorder_name, FOPEN_W_MODE); + cwd = xgetcwd(); + fprintf(recorder_file, "PWD %s\n", cwd); + free(cwd); +} + +@ After we know the log file name, we have used |recorder_change_filename| +to change the name of the recorder file to the usual thing. +@<Forward declarations@>= +static void recorder_change_filename (const char *new_name); + +@ Now its time to define this function. +Unfortunately, we have to explicitly take +the output directory into account, since the new name we are +called with does not; it is just the log file name with {\tt .log} +replaced by {\tt .fls}. + +@ @<\TeX\ Live auxiliary functions@>= +static void +recorder_change_filename (const char *new_name) +{ char *temp = NULL; + if (!recorder_file) + return; +#if defined(_WIN32) + fclose (recorder_file); /* An open file cannot be renamed. */ +#endif /* |_WIN32| */ + if (output_directory) { + temp = concat3(output_directory, DIR_SEP_STRING, new_name); + new_name = temp; + } + +#if defined(_WIN32) + remove (new_name); /* A file with the |new_name| must not exist. */ +#endif /* |_WIN32| */ + rename(recorder_name, new_name); + free(recorder_name); + recorder_name = xstrdup(new_name); +#if defined(_WIN32) + recorder_file = xfopen (recorder_name, FOPEN_A_MODE); /* A closed file must be opened. */ +#endif /* |_WIN32| */ + if (temp) + free (temp); +} + +@ Now we are ready to record file names. The prefix INPUT is added +to an input file and the prefix OUTPUT to an output file. +But both functions for recording a file name use the same +function otherwise, which on first use will start the recorder. + +@<\TeX\ Live auxiliary functions@>= +static void +recorder_record_name (const char *pfx, const char *fname) +{ @+if (recorder_enabled) { + if (!recorder_file) + recorder_start(); + fprintf(recorder_file, "%s %s\n", pfx, fname); + fflush(recorder_file); + } +} + + +static void +recorder_record_input (const char *fname) +{ recorder_record_name ("INPUT", fname); +} + +static void +recorder_record_output (const char * fname) +{ recorder_record_name ("OUTPUT", fname); +} + +@ Because input files are also recorded when writing the optional sections, +we need the following declaration. + +@<Forward declarations@>= +static void recorder_record_input (const char *fname); + +@ In WIN32, texmf.cnf is not recorded in +the case of {\tt -recorder}, because |parse_options| is executed +after the start of kpathsea due to special initializations. +Therefore we record {\tt texmf.cnf} with the following code: + +@<record {\tt texmf.cnf}@>= +if (recorder_enabled) { + char **p = kpse_find_file_generic ("texmf.cnf", kpse_cnf_format, 0, 1); + if (p && *p) { + char **pp = p; + while (*p) { + recorder_record_input (*p); + free (*p); + p++; + } + free (pp); + } +} + + + + +@*1 The {\tt -cnf-line} Option. +With the \.{-cnf-line} option it is possible to specify +a line of text as if this line were part of \TeX's configuration +file---even taking precedence over conflicting lines in the configuration +file. For example it is possible to change \TeX's +\.{TEXINPUTS} variable by saying \.{--cnf-line=TEXINPUTS=/foo}. +The configuration lines are temporarily stored in the variable +|cnf_lines| and counted in |cnf_count| because we can send them +to the \.{kpathsearch} library only after the library has been +initialized sufficiently. + +@<Global...@>= +static char **cnf_lines=NULL; +static int cnf_count=0; + +@ @<handle the options@>= +else @+if (ARGUMENT_IS ("cnf-line")) + add_cnf_line(optarg); + +@ The function |add_cnf_line| stores the +given command line argument in the variable |cnf_lines|. + +@<\TeX\ Live auxiliary functions@>= +static void add_cnf_line(char *arg) +{@+ cnf_count++; + cnf_lines=xrealloc(cnf_lines,sizeof(char*)*cnf_count); + cnf_lines[cnf_count-1]=arg; +} + +@ To activate the configuration lines they are passed to the + \.{kpathsearch} library. + +@<activate configuration lines@>= +#if 1 /* this function does not exists always */ +{@+ int i; + for (i=0;i<cnf_count;i++) + kpathsea_cnf_line_env_progname (kpse_def, cnf_lines[i]); + free(cnf_lines); +} +#endif + + +@*1 The Input File. +After we are done with the options, +we inform the \.{kpathsearch} library about the program name. +This is an important piece of information for the library +because the library serves quite different programs +and its behavior can be customized for each program +using configuration files. +After the program and engine name is set, +the library is ready to use. +@<set the program and engine name@>= +if (!user_progname) + user_progname = dump_name; +#if defined(WIN32) + if (user_progname) + kpse_reset_program_name (user_progname); +#else + kpse_set_program_name (argv[0], user_progname); +#endif + xputenv ("engine", "texprof");@/ + + +@ After the options, the command line usually continues with the name of the input +file. Getting a hold of the input file name can be quite complicated, +but the \.{kpathsearch} library will help us to do the job. + +We start by looking at the first argument after the options: +If it does not start with an +``\.{\AM}'' and neither with a ``\.{\BS}'', it's a simple file name. +Under Windows, however, filenames might start with a drive letter +followed by a colon and a ``\.{\BS}'' which is used to separate +directory names. Finally, if the filename is a quoted string, we need +to remove the quotes before we use the \.{kpathsearch} library to find it +and reattach the quotes afterward. + +@<\TeX\ Live auxiliary functions@>= +#ifdef WIN32 +static void clean_windows_filename(char *filename) +{@+if (strlen (filename) > 2 && isalpha (filename[0]) && + filename[1] == ':' && filename[2] == '\\') + { char *pp; + for (pp = filename; *pp; pp++) + if (*pp == '\\') + *pp = '/'; + } +} +#endif + +static char *find_file(char *fname, kpse_file_format_type t, int mx) +{@+char *filename; + int final_quote=(int)strlen(fname)-1; + int quoted = final_quote>1 && fname[0] == '"' && fname[final_quote]=='"'; + if (quoted) { + /* Overwrite last quote and skip first quote. */ + fname[final_quote] = '\0'; + fname++; + } + filename = kpse_find_file(fname, t, mx); + if (full_name_of_file!=NULL) + { free(full_name_of_file); full_name_of_file=NULL;} + if (filename!=NULL) + full_name_of_file=strdup(filename); + if (quoted) { + /* Undo modifications */ + fname--; + fname[final_quote] = '"'; + } + return filename; +} + +static char *get_input_file_name (void) +{@+ + char *input_file_name = NULL; + + if (argv[optind] && argv[optind][0] != '&' && argv[optind][0] != '\\') + { +#ifdef WIN32 + clean_windows_filename(argv[optind]); +#endif + argv[optind] = normalize_quotes(argv[optind], "input file"); + input_file_name=find_file(argv[optind],kpse_tex_format, false); + } + return input_file_name; +} + + +@ After we called |get_input_file_name|, we might need to look at |argv[argc-1]| +in case we run under Windows. + +@<set the input file name@>= + main_input_file = get_input_file_name (); + +#ifdef WIN32 + /* Were we given a simple filename? */ + if (main_input_file == NULL) { + char *file_name=argv[argc-1]; + if (file_name && file_name[0] != '-' && file_name[0] != '&' && file_name[0] != '\\') { + clean_windows_filename(file_name); + file_name = normalize_quotes(file_name, "argument"); + main_input_file=find_file(file_name,kpse_tex_format, false); + argv[argc-1] = file_name; + } + } +#endif + + +@ After we have an input file, we make an attempt at filling in options +from the {\tt texmf.cfg} file. + +@<set defaults from the {\tt texmf.cfg} file@>= + if (filelineerrorstylep < 0) + filelineerrorstylep = texmf_yesno ("file_line_error_style"); + if (parsefirstlinep < 0) + parsefirstlinep = texmf_yesno ("parse_first_line");@/@t~@> + +@ We needed: +@<\TeX\ Live auxiliary functions@>= +static int texmf_yesno(const char *var) +{@+ + char *value = kpse_var_value (var); + return value && (*value == 't' || *value == 'y' || *value == '1'); +} + +@ We need a stack, matching the |line_stack| that +contains the source file names. For the full source filenames we use +poiters to |char| because these names are just used for output. + +@<Global...@>= +static char * @!source_filename_stack0[max_in_open]={NULL}, **const @!source_filename_stack = @!source_filename_stack0-1; +static char * @!full_source_filename_stack0[max_in_open]={NULL}, **const @!full_source_filename_stack = @!full_source_filename_stack0-1; +static char *full_name_of_file=NULL; + +@ The function |print_file_line| +prints ``file:line:error'' style messages using +the |source_filename_stack|. If it fails to find the file name, it +falls back to the ``non-file:line:error'' style. + +@<Basic printing...@>= +static void print_file_line(void) +{@+int level=in_open; + while (level>0 && full_source_filename_stack[level]==NULL) level--; + if (level==0) print_nl("! "); + else + { print_nl(""); print(full_source_filename_stack[level]); print_char(':'); + if (level==in_open) print_int(line); + else print_int(line_stack[level]); + print(": "); + } +} + +@*1 The Format File. +Most of the time \TeX\ is not running as \.{initex} +but it runs with a format file preloaded. +To set the format name, we first check if the format name was given on the +command line with an ``\.{\AM}'' prefix, +second we might check the first line of the input file, +and last, we check if the program is an initex program. + +If we still don't have a format, the program +name is our best guess. +There is no need to check for an extension, because the +\.{kpathsearch} library will take care of that. +We store the format file name in |dump_name| which is +used in the function |w_open_in| below. + +@<set the format name@>= +if (parsefirstlinep && !dump_name) + parse_first_line (main_input_file); +if (!main_input_file && argv[1] && argv[1][0] == '&') + dump_name = argv[1] + 1; +if (strcmp(kpse_program_name, "initexprof")==0) iniversion = true; +if (!dump_name) + dump_name = kpse_program_name; +if (!dump_name) +{ fprintf(stderr,"Unable to determine format name\n"); + exit(1); +} +if (ltxp) etexp=1; +if (etexp && !iniversion) +{ fprintf(stderr,"-etex and -ltx require -ini\n"); + exit(1); +} + +@ Here is the function |parse_first_line |. It searches the first line of +the file for a \TeX\ comment of the form ``\%\AM format''\footnote{${}^1$}{The idea of using this format came from Wlodzimierz Bzyl.}. +If found, we will use the format given there. + +@<\TeX\ Live auxiliary functions@>= +static void parse_first_line(char*filename) +{@+ FILE *f=NULL; + if (filename==NULL) return; + f = open_in(filename,kpse_tex_format,"r"); + if (f!=NULL) + { char *r,*s,*t=read_line (f); + xfclose (f, filename); + if (t==NULL) return; + s=t; + if (s[0] == '%' && s[1] == '&') { + s = s+2; + while ( ISBLANK(*s)) ++s; + r=s; + while (*s!=0 && *s!=' ' && *s!='\r' && *s!='\n') s++; + *s=0; + if (dump_name==NULL) { + char *f_name = concat (r, format_extension); + char *d_name = kpse_find_file (f_name,kpse_fmt_format, false); + if (d_name && kpse_readable_file (d_name)) { + dump_name = xstrdup (r); + kpse_reset_program_name (dump_name); + } + free (f_name); + } + } + free (t); + } +} + +@*1 Commands. +In the old days, \TeX\ was a \PASCAL\ program, and standard \PASCAL\ +did say nothing about a command line. So \TeX\ would open the terminal +file for input and read all the information from the terminal. +If you don't give \TeX\ command line arguments, this is still true today. +In our present time, people got so much used to control the behavior +of a program using command line arguments---especially when writing +scripts---that \TeX\ Live allows the specification of commands on +the command line which \TeX\ would normally expect on +the first line of its terminal input. + +So our next task is +writing a function to add the remainder of the +command line to \TeX's input buffer. +The main job is done by the |input_add_str| function +which duplicates part of the |input_ln| function. +Further it skips initial spaces and replaces trailing spaces +and line endings by a single space. + +@<\TeX\ Live auxiliary functions@>= +static void input_add_char(unsigned int c) +{@+ if (last >= max_buf_stack) + {@+max_buf_stack=last+1; + if (max_buf_stack==buf_size) + @<Report overflow of the input buffer, and abort@>; + } + buffer[last]=xord[c];incr(last); +} + +static void input_add_str(const char *str) +{@+ int prev_last; + while (*str==' ') str++; + prev_last=last; + while (*str!=0) + +input_add_char(*str++); + for (--last; last >= first ; --last) + { char c =buffer[last]; + if ((c) != ' ' && (c) != '\r' && (c) != '\n') break; + } + last++; + if (last>prev_last) input_add_char(' '); +} + +static int input_command_line(void) +{@+ +last=first; +while (optind < argc) input_add_str(argv[optind++]); +loc=first; +return (loc < last); +@+ } + +@ @<Forward declarations@>= +static int input_command_line(void); + + +@*1 Opening Files. +When we open an output file, there is usually no searching necessary. +In the best case, we have an absolute path and can open it. +If the path is relative, we try in this order: +the |file_name| prefixed by the |output_directory|, +the |file_name| as is, and +the |file_name| prefixed with the environment variable |TEXMFOUTPUT|. + +If we were successful with one of the modified names, we update +|name_of_file|. + +@<\TeX\ Live functions@>= +static FILE *open_out(const char *file_name, const char *file_mode) +{@+ FILE *f=NULL; + char *new_name=NULL; + int absolute = kpse_absolute_p(file_name, false); + if (absolute) + { f=fopen(file_name,file_mode); + if (f!=NULL) recorder_record_output (file_name); + return f; + } + if (output_directory) + { new_name = concat3(output_directory, DIR_SEP_STRING, file_name); + f = fopen(new_name,file_mode); + if (f==NULL) {@+ free(new_name); new_name=NULL;@+} + } + if (f==NULL) + f = fopen(file_name,file_mode); + if (f==NULL) + { const char *texmfoutput = kpse_var_value("TEXMFOUTPUT"); + if (texmfoutput!=NULL && texmfoutput[0]!=0) + { new_name = concat3(texmfoutput, DIR_SEP_STRING, file_name);@/ + f = fopen(new_name,file_mode); + if (f==NULL) {@+ free(new_name); new_name=NULL; @+} + } + } + if (f!=NULL && new_name!=NULL) + update_name_of_file(new_name,(int)strlen(new_name)); + if (f!=NULL) recorder_record_output ((char*)name_of_file+1); + if (new_name!=NULL) free(new_name); + return f; +} + +static bool a_open_out(alpha_file *f) /*open a text file for output*/ +{@+f->f=open_out((char*)name_of_file+1,"w"); + return f->f!=NULL && ferror(f->f)==0;@+ +} + +static bool b_open_out(byte_file *f) /*open a binary file for output*/ +{@+f->f=open_out((char *)name_of_file+1,"wb"); +return f->f!=NULL && ferror(f->f)==0;@+ +} + +#ifdef @!INIT +static bool w_open_out(word_file *f) /*open a word file for output*/ +{@+f->f=open_out((char *)name_of_file+1,"wb"); + return f->f!=NULL && ferror(f->f)==0;@+ +} +#endif + + +@ Format file names must be scanned +before \TeX's string mechanism has been initialized. +The function |update_name_of_file| will set |name_of_file| from +a \CEE/ string. + +We dare not give error messages here, since \TeX\ calls this routine before +the |error| routine is ready to roll. Instead, we simply drop excess characters, +since the error will be detected in another way when a strange file name +isn't found. +@^system dependencies@> + +@<\TeX\ Live auxiliary functions@>= +static void update_name_of_file(const char *@!s, int @!k) +{@+ int j; + if (k <= file_name_size) name_length=k;@+ + else name_length=file_name_size; + for (j=0; j<name_length;j++) name_of_file[j+1]=xchr[(int)s[j]]; + name_of_file[name_length+1]=0; +} + +@ In standard \TeX, the |reset| macro is used to open input files. +The \.{kpathsearch} library uses different search paths for +different types of files and therefore different functions are needed to +open these files. The common code is in the function |open_in|. + +@<\TeX\ Live auxiliary functions@>= +static FILE*open_in(char*filename,kpse_file_format_type t,const char*rwb) +{@+ char *fname=NULL; + FILE*f= NULL; + fname= find_file(filename,t,true); + if(fname!=NULL) + {@+ + f= fopen(fname,rwb); + if (f!=NULL) recorder_record_input(fname); + if (full_name_of_file!=NULL) free(full_name_of_file); + full_name_of_file=fname;@+ + } + return f; +} + +static bool a_open_in(alpha_file *f) /*open a text file for input*/ +{@+f->f= open_in((char *)name_of_file+1,kpse_tex_format,"r"); + if (f->f!=NULL) get(*f); + return f->f!=NULL && ferror(f->f)==0; +} + +static bool b_open_in(byte_file *f) /*open a binary file for input*/ +{@+f->f= open_in((char *)name_of_file+1,kpse_tfm_format,"rb"); + if (f->f!=NULL) get(*f); + return f->f!=NULL && ferror(f->f)==0; +} + +static bool w_open_in(word_file *f) /*open a word file for input*/ +{@+ + f->f=NULL; + if (name_of_file[1]!=0) + f->f= open_in((char*)name_of_file+1,kpse_fmt_format,"rb"); + if (f->f!=NULL) get(*f); + return f->f!=NULL && ferror(f->f)==0; +} + +@ \TeX's |open_fmt_file| function will call the following function +either with the name of a format file as given with an ``\.{\AM}'' +prefix in the input or with |NULL| if no such name was specified. +The function will try |dump_name| as a last resort before returning |NULL|. + + + +@<\TeX\ Live functions@>= +static bool open_fmt_file(void) +{@+int j=loc; + if (buffer[loc]=='&') + {@+incr(loc);j=loc;buffer[last]=' '; + while (buffer[j]!=' ') incr(j); + update_name_of_file((char *)buffer+loc,j-loc); + if (w_open_in(&fmt_file)) goto found; + } + update_name_of_file(dump_name,(int)strlen(dump_name)); + if (w_open_in(&fmt_file)) goto found; + name_of_file[1]=0; + wake_up_terminal; + wterm_ln("I can't find a format file!"); + return false; +found: loc=j;return true; +} + + +@ The \TeX\ Live infrastructure is able to generate format files, +font metric files, +and even some tex files, if required. + +@<enable the generation of input files@>= + kpse_set_program_enabled (kpse_tfm_format, MAKE_TEX_TFM_BY_DEFAULT, + kpse_src_compile);@/ + kpse_set_program_enabled (kpse_tex_format, MAKE_TEX_TEX_BY_DEFAULT, + kpse_src_compile);@/ + kpse_set_program_enabled (kpse_fmt_format, MAKE_TEX_FMT_BY_DEFAULT, + kpse_src_compile);@/ + + + +@*1 Date and Time. +We conclude this chapter using \.{time.h} to provide a function +that is used to initialize +\TeX's date and time information. Because |time| is one of \TeX's +macros, we add the function |tl_now| before including \TeX's macros +to wrap the call to the |time| function. +It sets the variable |start_time| and returns a pointer to a |tm| structure +to be used later in |fix_date_and_time|. + +To support reproducible output, the environment variable |SOURCE_DATE_EPOCH| +needs to be checked. If it is set, it is an ASCII representation of +a UNIX timestamp, defined as the number +of seconds, excluding leap seconds, since 01 Jan 1970 00:00:00 UTC. +Its value is then used to initialize the |start_time| variable. + +The \TeX\ Live conventions further require that setting the +|FORCE_SOURCE_DATE| environment variable to $1$ will cause also \TeX's primitives +\.{\\year}, \.{\\month}, \.{\\day}, and \.{\\time} to use this value +as the current time. Looking at the \TeX\ Live code also reveals that +these primitives use the local time instead of the GMT if this variable is +not set to~1. + +@<Header files and function declarations@>= +#include <time.h> +static time_t start_time = ((time_t)-1); +static char *source_date_epoch,*force_source_date; + +#if defined(_MSC_VER) && _MSC_VER < 1800 +#define strtoull _strtoui64 +#endif + +static struct tm *tl_now(void) +{@+struct tm *tp; + time_t t; + source_date_epoch= getenv("SOURCE_DATE_EPOCH"); + force_source_date= getenv("FORCE_SOURCE_DATE"); + if (force_source_date!=NULL && + (force_source_date[0]!='1' || force_source_date[1]!=0)) + force_source_date=NULL; + + if (source_date_epoch!=NULL) + { start_time= (time_t)strtoull(source_date_epoch, NULL, 10); + if (force_source_date!=NULL) + t=start_time; + else + t=time(NULL); + } + else + t=start_time=time(NULL); + if (force_source_date) + tp=gmtime(&t); + else + tp=localtime(&t); + return tp; +} + +@*1 Retrieving File Properties. +To support \LaTeX, a few more time related functions are needed. +@<Header files and function declarations@>= +#define TIME_STR_SIZE 30 +static char time_str[TIME_STR_SIZE]; +static void get_creation_date(void); +static void get_file_mod_date(void); +static int get_file_size(void); + +#include <md5.h> +#define DIGEST_SIZE 16 +#define FILE_BUF_SIZE 1024 +static md5_byte_t md5_digest[DIGEST_SIZE]; + +static int get_md5_sum(int s, int file); + +@ The code that follows was taken from the \.{texmfmp.c} file of +the \TeX\ Live distribution and slightly modified. + + +@<\TeX\ Live auxiliary functions@>= + +static void +make_time_str(time_t t, bool utc) +{ + struct tm lt, gmt; + size_t size; + int off, off_hours, off_mins; + + /* get the time */ + if (utc) { + lt = *gmtime(&t); + } + else { + lt = *localtime(&t); + } + size = strftime(time_str, TIME_STR_SIZE, "D:%Y%m%d%H%M%S", <); + /* expected format: |"D:YYYYmmddHHMMSS"| */ + if (size == 0) { + /* unexpected, contents of |time_str| is undefined */ + time_str[0] = '\0'; + return; + } + + /* correction for seconds: S can be in range 00 to 61, + the PDF reference expects 00 to59, + therefore we map |"60"| and |"61"| to |"59"| */ + if (time_str[14] == '6') { + time_str[14] = '5'; + time_str[15] = '9'; + time_str[16] = '\0'; /* for safety */ + } + + /* get the time zone offset */ + gmt = *gmtime(&t); + + /* this calculation method was found in exim's tod.c */ + off = 60 * (lt.tm_hour - gmt.tm_hour) + lt.tm_min - gmt.tm_min; + if (lt.tm_year != gmt.tm_year) { + off += (lt.tm_year > gmt.tm_year) ? 1440 : -1440; + } else if (lt.tm_yday != gmt.tm_yday) { + off += (lt.tm_yday > gmt.tm_yday) ? 1440 : -1440; + } + + if (off == 0) { + time_str[size++] = 'Z'; + time_str[size] = 0; + } else { + off_hours = off / 60; + off_mins = abs(off - off_hours * 60); + snprintf(&time_str[size], TIME_STR_SIZE-size, "%+03d'%02d'", off_hours, off_mins); + } +} + +static void get_creation_date(void) +{ make_time_str(start_time,source_date_epoch!=NULL); +} + +/* static structure for file status set by |find_input_file| */ +#ifdef WIN32 +static struct _stat file_stat; +#define GET_FILE_STAT _stat(fname,&file_stat) +#else +static struct stat file_stat; +#define GET_FILE_STAT stat(fname,&file_stat) +#endif + + +static char* find_input_file(void) +{ char *fname; + int r; + if (output_directory&&!kpse_absolute_p((char*)name_of_file0, false)) + { int r=-1; + fname = concat3(output_directory, DIR_SEP_STRING, (char*)name_of_file0); + r=GET_FILE_STAT; + if (r==0) + return fname; + free(fname); + } + fname = kpse_find_tex((char*)name_of_file0); + if (fname!=NULL) + { r=GET_FILE_STAT; + if (r==0) + return fname; + free(fname); + } + fname=(char*)name_of_file0; + r=GET_FILE_STAT; + if (r==0) + return strdup(fname); + return NULL; +} + + +static void get_file_mod_date(void) +{ char *fname=NULL; + fname= find_input_file(); + time_str[0]=0; + if(fname!=NULL) + { make_time_str(file_stat.st_mtime,source_date_epoch!=NULL && force_source_date!=NULL); + free(fname);@+ + } +} + +static int get_file_size(void) +{ int s=-1; + char *fname=NULL; + fname= find_input_file(); + if(fname!=NULL) + {s=file_stat.st_size; + free(fname);@+ + } + return s; +} + + +static int get_md5_sum(int s, int file) +{ md5_state_t st; + memset(md5_digest,0,DIGEST_SIZE); + if (file) + { char *fname; + pack_file_name(s,empty_string,empty_string,NULL); + fname= find_input_file(); + if(fname!=NULL) + { FILE *f; + f = fopen(fname, "rb"); + if (f != NULL) + { int r; + char file_buf[FILE_BUF_SIZE]; + recorder_record_input(fname); + md5_init(&st); + while ((r = fread(&file_buf, 1, FILE_BUF_SIZE, f)) > 0) + md5_append(&st, (const md5_byte_t *) file_buf, r); + md5_finish(&st, md5_digest); + fclose(f); + } + free(fname); + } + else + return 0; + } + else + { md5_init(&st); + md5_append(&st,(md5_byte_t *)&str_pool[str_start[s]], + str_start[s + 1] - str_start[s]); + md5_finish(&st, md5_digest); + } + return DIGEST_SIZE; +} + +@* Profiling. +If we want to find out where and how \TeX\ spends its time, we need +a profiler. The common profilers, like {\tt gprof}, +examine the executable code of \TeX, then take some measurments at run time, +and map this information to the functions or source lines of \TeX's code. + +But \TeX\ is a programming language by itself, and when we program +in \TeX, we want to map the timing information gathered at run time +to the macros and source lines of \TeX's input files. +The profiler implemented in the follwing code serves this purpose. + +By default, profiling is initialy disabled. +To enable profiling, you can use the {\tt -prof} option on the +command line. + +@<explain the options@>= + " -prof "@/ + @t\qquad@>"\t enable profiling\n"@/ + +@ This option will set the |profile_on| variable, defined below, to true. + +@<more options@>= + { "prof", 0, &profile_on, 1 }, + +@ @<Global variables@>= +static int @!profile_on=false; + +@ To restrict profiling to selected parts of \TeX's input, +we define two primitives for switching profiling on and off. + +@d profile_on_code (eTeX_last_extension_cmd_mod+3) /* `\.{\\profileon}' */ +@d profile_off_code (eTeX_last_extension_cmd_mod+4) /* `\.{\\profileoff}' */ +@d pdftex_first_extension_code profile_off_code+1 + +@<Put each...@>= +primitive("profileon", extension, profile_on_code); +@!@:profileon\_}{\.{\\profileon} primitive@> +primitive("profileoff", extension, profile_off_code); +@!@:profileoff\_}{\.{\\profileoff} primitive@> + +@ @<Cases of |extension| for |print_cmd_chr|@>= +case profile_on_code: print_esc("profileon");@+break; +case profile_off_code: print_esc("profileoff");@+break; + +@ @<Cases for |do_extension|@>= +case profile_on_code: +if (!profile_on) +{ profile_on=true; + @<record profiling on@>@; +} +break; +case profile_off_code: +if (profile_on) +{ @<record profiling off@>@; + profile_on=false; +} +break; + +@*1 Files and Lines. +The ``instructions'' that drive the \TeX\ interpreter are called ``tokens'' +and we want to keep track of the files and the lines +where the tokens come from. +If a token comes from an external file, then \TeX's variable |line| will +contain the correct line number, and |cur_file| contains the current file. +|cur_file| is an abbreviation for |input_file[index]| with +|index| beeing a short hand for |cur_input.index_field|. +We can not use the |index| number to identify input files, +because \TeX\ will reuse these numbers, possibly many times, after a file +has been closed. Instead we make a new array |input_file_num| that +runs in parallel to |input_file| and contains a unique current file number. +Further we make a new |read_file_num| array that runs +in parallel to |read_file|. + +@d cur_file_num input_file_num[index] /*the current unique |alpha_file| number*/ + +@<Glob...@>= +static uint8_t @!input_file_num0[max_in_open], + *const @!input_file_num = @!input_file_num0-1; +static uint8_t @! read_file_num[20]; + +@ To implement the association between unique file numbers and full +file names, we use the array |file_num_name|. We will store file +numbers with 8 bits and line numbers with 16 bits in a single 32 bit +number. We do this because we will need to store this information +together with the tokens in a token list. This representation will +keep the most significant byte zero, so that we can later use it for +the ``command'' value. + +@<Global...@>= +#define FILE_NUM_BITS 8 +#define MAX_FILE_NUM ((1<<FILE_NUM_BITS)-1) +#define LINE_BITS 16 +#define MAX_LINE ((1<<LINE_BITS)-1) +#define FILE_LINE(F,L) (((F)<<(LINE_BITS))|(L)) +#define FL_FILE(FL) ((FL)>>LINE_BITS) +#define FL_LINE(FL) ((FL)&MAX_LINE) +static char * @!file_num_name[MAX_FILE_NUM+1]; +static int file_from_cmd [MAX_FILE_NUM+1]; /* first command from the file */ +static int file_to_cmd [MAX_FILE_NUM+1]; /* last command from the file */ +static int file_num; /* the the last |file_num_name| allocated */ +static uint32_t cur_file_line=0; /* the file and line for |cur_tok| */ + +@ @<check |line| for overflow@>= +if (line>=MAX_LINE) overflow("too many input lines", MAX_LINE); + +@ Whenever we have a new |full_name_of_file|, we allocate +a new unique file number. + +@<Allocate a file number@>= +if (file_num>=MAX_FILE_NUM) overflow("file number",file_num); +else file_num++; +file_num_name[file_num]=strdup(full_name_of_file); +file_from_cmd[file_num]=cmd_count; + +@ Whenever \TeX\ sets |cur_file| to a new value, we need to +set |cur_file_num| as well. + +@<Set new |cur_file_num|@>= +@<Allocate a file number@>@; +cur_file_num=file_num; + +@ Whenever \TeX\ opens |read_file[n]| it needs to set the file count. +@<Set new |read_file_num[n]|@>= +@<Allocate a file number@>@; +read_file_num[n]=file_num; + +@ A few file numbers are predefined. Some tokens, for instance those +that are loaded from a format file, have an unknown origin and are +classified as comming from an |unknown_file|. +We use |system_file| to assign time intervals to +the system and use the command field to distinguish between different +system events. There might also be tokens from the terminal, either +typed in interactively (which will messup your timing values) +or from the command line. + +For the commands from the |system_file|, we use +special line numbers to distinguish various cases. + +@d unknown_file 0 /*tokens with unknown origin, usualy from a format file*/ +@d system_file 1 /*tokens generated by the system*/ +@d terminal_file 2 /*tokens read from the terminal*/ +@d system_unknown 0 /*should not happen*/ +@d system_start 1 /*startup of \TeX*/ +@d system_end 2 /*end of \TeX*/ +@d system_ship_out 3 /*time spent in |ship_out()|*/ +@d system_line_break 4 /*time spent in |line_break()|*/ +@d system_init_trie 5 /*time spent in |line_break()|*/ +@d system_build_page 6 /*time spent in |line_break()|*/ +@d system_input_ln 7 /*time spent in |line_break()|*/ +@d system_insert 8 /*time spent on tokens inserted by \TeX*/ + + +@<Set init...@>= +file_num_name[unknown_file]="unknown"; +file_num_name[system_file]="system"; +file_num_name[terminal_file]="terminal"; +file_num=terminal_file; + +@ When \TeX\ reads a token from an external file, it has to set +|cur_file_line| based on the information in |cur_input|. +This code is parallel to the code that is used to read the next line: + +@<Set |cur_file_line| based on the information in |cur_input|@>= +if (terminal_input) + cur_file_line=FILE_LINE(terminal_file,0); +else if (name<=19) + cur_file_line=FILE_LINE(read_file_num[name-1],0); /* do I need the line? */ +else + cur_file_line=FILE_LINE(cur_file_num,line); + +@ When we end a \.{\\read} line, we set the current file and line. +@<Set |cur_file_line| when a \.{\\read} line ends@>= + cur_file_line=FILE_LINE(read_file_num[name-1],0); + + +@ As described above, we store file and line numbers as 32 bit integers. +When reading input from external files, we know the file and the line; +but for token lists we need to store this information together +with the tokens, when we create the token list. +As a simple solution, we allocate a 32 bit integer for all pointers. + +Whenever in \TeX's code a new token is generated, we know what file and +line is responsible for what is going on. The newly generated token +will then point to the same file and line. + +@<Glob...@>= +static uint32_t @!fl_mem0[mem_max-mem_min+1], + *const @!fl_mem = @!fl_mem0-mem_min; /*the big dynamic file/line storage*/ + +@*1 Timing. +When the interpreter of \TeX\ executes a command, we need to measure the +time needed to execute it and record that information in a file. +We call such a measurement a ``time stamp'' or ``stamp'' +for short. +This process should be quick, in order not to disturb the measurements +too much by the time needed for the measurement itself and its recording. +So we keep the data in a large array, and postpone writing the output file +until \TeX\ terminates. + +Now let us consider the measurement of such a time stamp. +As a general rule, the start of a new time interval is the end +of the previous time interval. There is only a single look up +of the current time for both. So all time intervals will add up +to the total run time. + +We keep the start time in two variables |start_sec| and |start_nsec|; +the first counts the seconds, the other (roughly) the nano seconds. +When we measure the end time, we should know the previous start time, +and which command was executed and from which file and line this command +was taken. The measured end time is the start time for the next command. + + +@<Global variables@>= +static long start_nsec, start_sec, diff_nsec; +struct timespec ts; +static int time_error; + +@ To get timing information, we use the POSIX function |clock_gettime|. +Depending on the operating system there are many different variations. +The timer used for timing can be selected by defining |GETTIME| at +compile time. If |GETTIME| is not set, we try to find a good default. +Currently we use |timespec_get| under Windows and |clock_gettime| +with a tread specific clock otherwise. + +@<get current time@>= +#ifdef GETTIME +#if GETTIME==0 + time_error=clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts); +#elif GETTIME==1 + time_error=clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &ts); +#elif GETTIME==2 + time_error=clock_gettime(CLOCK_MONOTONIC_RAW, &ts); +#elif GETTIME==3 + time_error=clock_gettime(CLOCK_MONOTONIC, &ts); +#else + time_error=clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts); +#endif +#else +/* guess a default */ +#ifdef _WIN32 + time_error=timespec_get(&ts, TIME_UTC); +#else + time_error=clock_gettime(CLOCK_THREAD_CPUTIME_ID, &ts); +#endif +#endif + + +@ To record the timing information, we compute the time difference in +nano seconds, assuming that it fits into unsigned 32 bit which means +the difference should be less than about 4 seconds. + +@<compute elapsed time@>= + diff_nsec= (ts.tv_sec-start_sec)*1000000000+ (ts.tv_nsec-start_nsec); +#if 0 + printf("time: %ld %ld %ld\n", diff_nsec, (ts.tv_sec), (ts.tv_nsec)); +#endif + + start_nsec=ts.tv_nsec; + start_sec=ts.tv_sec; + +@*1 Commands. +The fourth piece of information that we store with file, line, and time +is the command that \TeX\ is executing. +The elapsed time will fit into an four byte unsigned integer, and +luckily also the command, the file and the line will do as well. +When starting a new time interval, often we will not yet know the +next command, its file, and its line. +We keep the command, the file, the line, in a set of variables starting with +|prof_|. These variables my change within a time interval, and the final +values are written when the end time is known. +There are also variables related to macro calls which are explainded later +but are already defined here because we will initialize them together +with the other variables. + +@<Global variables@>= +#define MAX_STAMPS 80000000 +#define MAX_MACRO_STACK 40000 +#define POP_BIT 0x80 + +static uint32_t stamp[MAX_STAMPS]; /*one chunk of profiling information*/ +static uint32_t st_count=0; /*the next available entry in the array above*/ +static uint32_t cmd_count=0; /*the number of time stamps in the array above*/ +static int prof_cmd=0; /*the command to be written */ +static uint32_t prof_file_line=0; /*the file and line to be written */ + +@ The code below initializes the variables. Note that we use the special +command value |system_cmd|. The ``real'' command values +are those that occur in the |big_switch| ranging from 0 (|escape|) +to 100 (|max_command|), the values that are used when entering +the |main_loop|(|letter|, |other_char|, |char_given|, and |char_num|) +are a subset of these. +The pseudo command |system_cmd| is just outside of this range. +A few more pseudo commands are needed below and we define them here. + +@d system_cmd (max_command+1) /*pseudo command value*/ +@d system_profile_on (system_cmd+1) +@d system_profile_off (system_cmd+2) +@d system_macro_push (system_cmd+3) +@d system_macro_pop (system_cmd+4) +@d system_macro_pop_small (system_cmd+5) +@d system_macro_pop_0 (system_cmd+6) + + +@<Initialize profiling@>= + @<Initialize the macro call stack@>@; + prof_cmd=system_cmd; + prof_file_line=FILE_LINE(system_file,system_start); + @<record macro call information if necessary@>@; +#if 0 + clock_getres(CLOCK_MONOTONIC, &ts); + printf("CLOCK_MONOTONIC: %ld %ld\n",ts.tv_sec,ts.tv_nsec); + + clock_getres(CLOCK_MONOTONIC_RAW, &ts); + printf("CLOCK_MONOTONIC_RAW: %ld %ld\n",ts.tv_sec,ts.tv_nsec); + + clock_getres(CLOCK_PROCESS_CPUTIME_ID, &ts); + printf("CLOCK_PROCESS_CPUTIME_ID: %ld %ld\n",ts.tv_sec,ts.tv_nsec); + + clock_getres(CLOCK_THREAD_CPUTIME_ID, &ts); + printf("CLOCK_THREAD_CPUTIME_ID: %ld %ld\n",ts.tv_sec,ts.tv_nsec); +#endif + @<get current time@>@; + diff_nsec=0; + start_nsec=ts.tv_nsec; + start_sec=ts.tv_sec; + +@ At the end of \TeX\ we check |last_depth| and clean the remaining +macro stack if necessary. We end the record always with recording +timing information. + +@<pop the macro call stack at the end of \TeX@>= +prof_cmd=cur_cmd; /* the stop command */ +prof_file_line=cur_file_line; +prof_depth=0; +profile_on=true; +@<get current time@>@; /* advance the time */ +@<compute elapsed time@>@; +@<record timing information@>@; /* pop to |prof_depth| */ + + +@ When we record the timing information, +we first store command, file, and line, and then store +the elapsed time. + +@d SHOW_RECORD_TIMING 0 + +@<record timing information@>= +if (profile_on) +{ if (st_count+3>MAX_STAMPS) + overflow("profile data",MAX_STAMPS); + @<record poping the macro stack if necessary@>@; + stamp[st_count++]= (prof_cmd<<24) | prof_file_line; + prof_cmd=prof_cmd&~POP_BIT; /*remove a possible |POP_BIT|*/ +#if SHOW_RECORD_TIMING + print_char('<');print_int(cmd_count); + print_char(':'); + if (prof_cmd&POP_BIT) print_char('-'); + print_int(prof_cmd&~POP_BIT); + print_char(':');print_int(prof_depth); + print_char('>');print_ln(); +#endif + cmd_count++; + @<get current time@>@; + @<compute elapsed time@>@; + stamp[st_count++]=diff_nsec; +} + + +@ To mark the execution of starting and ending profiling +we use the system commands for the start and the end of profiling. + +After switching profiling off, no more data is written to the output +file. So we have to record the macro call and timing information +explicitly before switching the profiling off. + +@<record profiling off@>= + prof_file_line=cur_file_line; + prof_cmd=system_profile_off; + prof_depth=cur_depth; + @<record macro call information if necessary@>@; + @<record timing information@>@; + +@ When switching profiling on, we have to syncronize the start time +with the current time and prepare everything for the recording +of the timing before entering the main loop again. +Setting the command, file and line information is simple. +Since we can not assume that the macro call stack is unchanged, +we record the necessary changes. + +@<record profiling on@>= + @<get current time@>@; + diff_nsec=0; + start_nsec=ts.tv_nsec; + start_sec=ts.tv_sec; + prof_file_line=cur_file_line; + prof_cmd=system_profile_on; + prof_depth=cur_depth; + @<record macro call information if necessary@>@; + +@ At the end of \TeX\ we record the timing for the |stop| command +and pop the macro call stack. + +@<record the end of \TeX@>= +@<pop the macro call stack at the end of \TeX@>@; + +@ There are two places where we regularly record the next command. +The first one is when \TeX\ enters the big switch. Here +we record the timing information before reading the next expanded token +and set the current file, line, and command after reading the +next expanded token. +The other place is at the start of the main loop. Here both +actions are done one after the other. Whenever we assiciate +a command with the current time slot by setting |prof_cmd| and +the profile data associated with it, we need to make sure that +changes of entries in the macro call are reported to the profiler. + +@<set current file, line, and command for the current time slot@>= +if (profile_on) +{ prof_cmd=cur_cmd; + prof_depth=cur_depth; + prof_file_line=cur_file_line; + @<record macro call information if necessary@>@; +} + +@ Some time expensive routines, |line_break| and |ship_out|, consume +time that depends entirely on the output generated by \TeX\ but +not on how that output is generated. So we charge the time spent in these +routines on the system. + +@<Local variables to save the profiling context@>= +int tmp_cmd; +int tmp_file_line; +int tmp_depth; + +@ @<Charge the time used here on |line_break|@>= +if (profile_on) +{ @<record timing information@>@; + tmp_file_line=prof_file_line; + tmp_cmd=prof_cmd; + tmp_depth=prof_depth; + prof_file_line=FILE_LINE(system_file,system_line_break); + prof_cmd=system_cmd; +} + + +@ @<restore the previous current file, line, and command@>= +if (profile_on) +{ @<record timing information@>@; + prof_file_line=tmp_file_line; + prof_cmd=tmp_cmd; + prof_depth=tmp_depth; +} + + + +@ @<Charge the time used here on |init_trie|@>= +if (profile_on) +{ @<record timing information@>@; + tmp_file_line=prof_file_line; + tmp_cmd=prof_cmd; + tmp_depth=prof_depth; + prof_file_line=FILE_LINE(system_file,system_init_trie); + prof_cmd=system_cmd; +} + + +@ @<Charge the time used here on |build_page|@>= +if (profile_on) +{ @<record timing information@>@; + tmp_file_line=prof_file_line; + tmp_cmd=prof_cmd; + tmp_depth=prof_depth; + prof_file_line=FILE_LINE(system_file,system_build_page); + prof_cmd=system_cmd; +} + + + +@ @<Charge the time used here on |ship_out|@>= +if (profile_on) +{ @<record timing information@>@; + tmp_file_line=prof_file_line; + tmp_cmd=prof_cmd; + tmp_depth=prof_depth; + prof_file_line=FILE_LINE(system_file,system_ship_out); + prof_cmd=system_cmd; +} + + +@*1 Macro Calls. +Let's talk about collecting information about macro calls. +Macro calls come in various flavours: +There are active characters and single letter control sequences; +both have their own region in the |eqtb| table of equivalents. +Then there is an empty control sequence, and last there +are lots of (currently up to 45000) multiletter control sequences. +The plain format defines about 1000 and the \LaTeX\ format about 23000 +of them. When |get_next| finds a control sequence, it sets |cur_cs| +to the index in the table of equivalents. +It will further set |cur_cmd=eq_type(cur_cs)|, |cur_chr=equiv(cur_cs)|, +and |cur_tok=cs_token_flag+cur_cs|. + +The |get_x_token| or |expand| procedure will then notice the macro call +and invoke |macro_call|. +|macro_call| will inspect the call site and the parameter section +of the macro and put the actual macro parameters on the parameter +stack before pushing the macro body on the input stack. + +But wait! |macro_call| will apply a technique called last call optimization +before doing any of the above: It will remove all entries from +the input stack that have no more tokens left for processing. +This allows tail recursive macro calls in constant stack space and +makes long recursive loops possible. +For example building the \LaTeX\ format uses a loop to read the +definition of UTF8 codes. +This loop has more than 35000 iterations and a nesting depth +of the same size. With last call optimization, the loop uses less than 3000 +entries on the input stack. + +Popping the stack early makes it slightly more difficult +to track who is calling whom---an information that we need if we want +to give cumulative timing for a macro call. Cumulative timing is the time spent +during that macro call including all the calls to sub-macros. + +The timing information that we collected in the previous section +assigned the time caused by the execution of \TeX's commands to the +specific line and file that caused the execution of that command. +As a consequnce, the time used for the expansion of a macro call +is assigned to the file and line that contains the call site of the macro. +The time that is spent on executing the commands in the macros body +are assigned to the file and line containing the macro definition. +But there is no information on the call graph that allows us to +classify one command as comming from a lower level of expansion than +the other. + +In this section, we want to assign the time used for the execution +of commands to a macro definition, with its name and the file and line +that contains the definition of the macro. +While the name of a macro is an important information, it is not +sufficient to relate the time to the macros name, because +the same name can be used for several different macros at various times. + +So we collect for a macro call the following data: + +\yskip\textindent{1)}The index |cur_cs| into the table of equivalents +|eqtb|. Using |cur_cs| it is possible to access the macros name. For +active characters and single letter control sequences, we obtain the +character by subtracting |active_base| or |single_base| from |cur_cs|. +For multi-letter control sequences, we find the index to |str_start| +for the macro name in |text(cur_cs)|, the text field of the corresponding +hash table entry. The association between |cur_cs| and the macro name +is stored in a separate section of the profilers output file. + +\yskip\textindent{2)}The line and file of the macro definition. +We store this information in the |fl_mem| array using |equiv(cur_cs)|, +the pointer to the reference count token of the macro. + +\yskip\textindent{3)}The ``unoptimized'' nesting depth of the macro call. + +We store this information in a 64 bit integer and define macros +to assemble and disassemble this integer. +From this information it is possible to reconstruct the call graph +and compute cumulative timing information for macro calls. +We keep the information for the whole ``unoptimized'' macro stack +in the |macro_stack|. +The varable |prof_depth| tells us the nesting depth of |prof_cmd|. +The variable |last_depth| tells us the nesting depth +of the last recorded time stamp and the variable |unchanged_depth| +tells us which part of the macro stack is unchanged since then. + + +@d CALL_DEPTH(A) ((A)>>48) +@d CALL_EQTB(A) (((A)>>32)&0xFFFF) +@d CALL_FILE(A) (((A)>>16)&0xFF) +@d CALL_LINE(A) ((A)&0xFFFF) +@d CALL_DE(A) ((A)>>32) +@d CALL_CFL(A) ((A)&0xFFFFFFFF) +@d CALL_INFO(D,C,FL) (((uint64_t)(D)<<48)|((uint64_t)(C)<<32)| + (system_macro_push<<24)|FL) + +@<Global variables@>= +static uint64_t macro_stack[MAX_MACRO_STACK]={0}; /* the macro calls */ +static int prof_depth; /* the nesting depth of macros */ +static int last_depth; /* the nesting depth last report1ed*/ +static int unchanged_depth; /* up to here no change on |macro_stack|*/ +static int prof_max_depth; + +@ @<Initialize the macro call stack@>= +{ int macro_depth=-1, macro_cs=0; + uint32_t macro_fl=FILE_LINE(terminal_file,0); + @<update the macro stack@>@; + cmd_count++; + stamp[st_count++]=CALL_CFL(macro_stack[0]); + stamp[st_count++]=CALL_DE(macro_stack[0]); + last_depth=unchanged_depth=prof_depth=0; +} + +@ We maintain the macro stack in the |macro_call| procedure +by adding local variables that capture the information of +the call token that cause the invocation of |macro_call|. + +@<additional local variables for |macro_call|@>= +uint32_t macro_fl=fl_mem[cur_chr]; +int macro_cs=cur_cs; +int macro_depth=cur_depth; + +@ At the end of |macro_call|, we use this information to +update the |macro_stack| and related variables. + +@<update the macro stack@>= +macro_depth++; +cur_depth=macro_depth; +if (macro_depth>=MAX_MACRO_STACK) + overflow("macro stack size", macro_depth); +macro_stack[macro_depth]=CALL_INFO(macro_depth,macro_cs,macro_fl); +if (macro_depth<=unchanged_depth) + unchanged_depth=macro_depth-1; + +@ We add files as part of the macro stack using the following code: +@<additional local variables for |start_input|@>= +uint32_t macro_fl=FILE_LINE(cur_file_num,0); +int macro_cs=0; +int macro_depth=cur_depth; + +@ We add calls to the output routine and hook macros like \.{\\everypar}, \.{\\everymath}, etc. to the macro stack using tis code: +@<additional local variables for |begin_token_list|@>= +uint32_t macro_fl=fl_mem[p]; +int macro_cs=undefined_control_sequence+t; +/*|undefined_control_sequence| is the last pointer in the hash table*/ +int macro_depth=cur_depth; + + +@ As we have seen above, recording timing information consists +of two steps: +In the first step we set global variables like |prof_cmd| and |prof_depth| +based on the current command. Then we wait until the command is executed, +and in the second step we compute the elapsed time and store the +information from the first step together with the time in the |stamp| +array. +Now we augment this process and store macro call related information. + +The key value that guides this process is |prof_depth|: +the macro nesting depth associated with |prof_cmd|. +Using it we can get from the |macro_stack| information about +all currently active macros at lower nesting levels. +Two more variables |last_depth| and |unchanged_depth| are related to it: +After recording macro call information for a command, +we set |last_depth=unchanged_depth=prof_depth|. +The next time we need to record macro call information, +|unchanged_depth| and |prof_depth| may have changed, but +|last_depth| should be unchanged. Because |unchanged_depth| +can only decrease, we know that $|unchanged_depth|\le|last_depth|$. +On the other hand, |prof_depth| can increase as well as decrease. +This gives us the following cases: + +\yskip\textindent{$|unchanged_depth|<|prof_depth|$} +Record the new stack entries from $|unchanged_depth|+1$ up to |prof_depth|. + +\yskip\textindent{$|prof_depth|=|unchanged_depth|=|last_depth|$:} +No information on macro calls is necessary. + +\yskip\textindent{$|prof_depth|<|unchanged_depth|=|last_depth|$:} +Record that the stack was popped from |last_depth| down to |prof_depth|. + +\yskip\textindent{$|prof_depth|\le|unchanged_depth|<|last_depth|$:} +Record that the stack was popped from |last_depth| down to |prof_depth|. + + +The common case that $|prof_dept|=|last_dept|-1$ asks for a more +compact representation and we use the most significant bit of the +command value to encode this case. +Note that we count this as a separate command. + +It would be nice if we could wait with recording the stack changes until +the command is completely executed. The command however might read +parameters which causes pops and pushes on the macro stack. So by the +time the command has finished, the stack might have changed considerably. +There is a further complication: the execusion of some commands does +not end with a jump to |big_switch| but with a jump to |big_reswitch|. +This will set a new value for |prof_cmd| and so will invalidate all our +preparations. +For this reason we need to make the recording of macro call information +idempotent. Recording several pops and pushes explicitly does not harm +(except for extra output) but setting the pop bit asks for trouble. +Therefore we postpone the recording of poping the macro stack. + + +@<record macro call information if necessary@>= +if (unchanged_depth<prof_depth) + @<record the new stack entries@>@; + + +@ @<record poping the macro stack if necessary@>= +if (last_depth>prof_depth) +{ if (last_depth==prof_depth+1) + prof_cmd=prof_cmd|POP_BIT; + else + stamp[st_count++]=(system_macro_pop<<24)| (last_depth-prof_depth); +#if SHOW_RECORD_TIMING + print_char('{');print_int(cmd_count); + print_char(':');print_int(system_macro_pop); + print_char(':');print_int(last_depth); + print_char('>');print_int(prof_depth); + print_char('}');print_ln(); +#endif + cmd_count++; + last_depth=unchanged_depth=prof_depth; +} + + +@ The information about new stack entries are taken from the |macro_stack|. + +@<record the new stack entries@>= +{ int i; + if (last_depth>unchanged_depth) + { +#if SHOW_RECORD_TIMING + print_char('{');print_int(cmd_count); + print_char(':');print_int(system_macro_pop); + print_char(':');print_int(last_depth); + print_char('>');print_int(unchanged_depth); + print_char('}');print_ln(); +#endif + cmd_count++; + } + if (st_count+2*(prof_depth-unchanged_depth)>MAX_STAMPS) + overflow("profile data",MAX_STAMPS); + for (i=unchanged_depth+1;i<=prof_depth;i++) + { +#if SHOW_RECORD_TIMING + print_char('[');print_int(cmd_count); + print_char(':');print_int(i-1); + print_char('<');print_int(CALL_DEPTH(macro_stack[i])); + print_char(':'); print_cs(CALL_EQTB(macro_stack[i])); + print_char(']');print_ln(); +#endif + cmd_count++; + stamp[st_count++]=CALL_CFL(macro_stack[i]); + stamp[st_count++]=CALL_DE(macro_stack[i]); + } + last_depth=unchanged_depth=prof_depth; + if (prof_depth>prof_max_depth) prof_max_depth=prof_depth; +} + + +@*1 Output the profile data. +Here is the code that outputs the results. +The format tries to be simple but flexible. +The output file has four parts: size data, file names, macro names, +and time stamps. To enable some error checking, the three file +parts start and end with an output marker. + +% we have typically from 1000 to 5000, in exteme cases up to 30000, +% file/line entries +% cut -d : -f 2,3 tmon.out | fgrep -v '.' | sort |uniq | wc -l + +@<Finish the extensions@>= +{ FILE *prof; + pack_job_name(".tprof"); + prof=fopen((char*)name_of_file0,"wb"); + if (prof==NULL) print_err("Unable to write the profile data\n"); + else { + int i; + prof_file_line=cur_file_line; + @<output marker@>@; + @<output size data@>@; + @<output marker@>@; + @<output file names@>@; + @<output marker@>@; + @<output macro names@>@; + @<output marker@>@; + @<output timing data@>@> + @<output marker@>@; + fclose(prof); + } +} + +@ The output marker consists of eight byte: the ASCII codes of ``TEX PROF''. + +@<output marker@>= + fputs("TEX PROF",prof); + + +@ The information necessary to process the file comes after the first +marker. Here and in the following all numbers are written out in +``big-endian byte order''. We provide the following information: + +The number of files (2 byte), +the number of byte used for filenames +including the zero bytes (2 byte), +the number of time stamps (4 byte). +The number of macro names (2 byte), +the number of bytes used for macro names (4 byte), +again including the zero bytes, +and the maximum nesting depth used on the |macro_stack|. + +We start with the macros to write multibyte integers in bigendian order. + +@d PUT1(N) fputc((N)&0xFF,prof) +@d PUT2(N) PUT1((N)>>8),PUT1(N) +@d PUT4(N) PUT2((N)>>16),PUT2(N) + + +@<output size data@>= + PUT2(file_num+1); /* the number of files */ +{ int n, m; + m=0; + for (i=0; i<=file_num; i++) + { n=strlen(file_num_name[i]); + m+=n+1; + } + PUT2(m); /* the number of byte used for file names */ +} + PUT4(cmd_count); /* the number of commands */ +{ int k, m; + m=k=0; + for (i=hash_base; i<undefined_control_sequence; i++) + if (text(i)!=0) + { k++; + m+=(str_start[text(i)+1]-str_start[text(i)])+1; + } + PUT2(k); /* the number of macro names */ + PUT4(m); /* the number of byte for the macro names */ + PUT2(prof_max_depth); /*the maximum macro nesting depth*/ +} + + +@ Writing the file names is simple. + +@<output file names@>= +for (i=0; i<=file_num; i++) + { fputs(file_num_name[i], prof); + PUT1(0); + } + +@ Here is the code to write the macro names to the output file. +It traverses the |hash_table| from |hash_base| up to +|undefined_control_sequence|. Each macro name is preceeded by +its index in the hash table stored in two byte. + +@<output macro names@>= +for (i=hash_base; i<undefined_control_sequence; i++) + if (text(i)!=0) + { int k; + PUT2(i); + for (k=str_start[text(i)];k<str_start[text(i)+1];k++) + PUT1(str_pool[k]); + PUT1(0); + } + + +@ Next we output the time stamps. We use a variable format +depending on the command value which is always in the top byte +of the stamp. We optimize the output size slightly: +For macro calls the |stamp| array contains the depth values. +It is of course more efficient to write the relative changes +into the output instead of the absolute values. +A most common case is poping the stack by one. This is recorded +in the |stamp| array by setting the |POP_BIT| in the command value +and we simply keep this bit. Small relative values $n$ in the range +$0 \le n \le 10$ are encoded using the command value +$|system_macro_pop_0|+n$. Values in the range $11 \le n \le 255$ +encoded as single byte values following the commmand code +|system_macro_pop_small|. All other values are encoded using +two byte following the command code |system_macro_pop|. +Encoding the pops separate from the calls, we need no longer +store the depth values with the calls. + +@<encode pop $n$@>= +#if SHOW_WRITE_TIMING + printf("!%d:%d:%d>%d\n",j++,i,last_depth,last_depth-n); +#endif + if (n<=10) + PUT1(system_macro_pop_0+n); + else if (n<=255) + { PUT1(system_macro_pop_small); + PUT1(n); + } + else + { PUT1(system_macro_pop); + PUT2(n); + } + last_depth=last_depth-n; + +@ Now we can output the timing data. + +@d SHOW_WRITE_TIMING 0 + +@<output timing data@>= + + i=0; +{ int j=0; + last_depth=-1; + while (i< st_count) + { int8_t c = stamp[i]>>24; + if (c==system_macro_pop) + { int n=stamp[i]&0xFFFF; + @<encode pop $n$@>@; + i++; + } + else if (c==system_macro_push) + { int d=stamp[i+1]>>16; + if (d<=last_depth) + { int n=last_depth-d+1; + @<encode pop $n$@>@; + /* here I could optimize the case $n=1$ by setting the |POP_BIT| + in |system_macro_push|*/ + } +#if SHOW_WRITE_TIMING + print_char('!');print_int(j++); + print_char(':');print_int(i); + print_char(':'); print_int(system_macro_push); + print_char(':');print_int(d); + print_char(':'); print_cs(stamp[i+1]&0xffff); + print_char(']');print_ln(); +#endif + PUT4(stamp[i]); i++; + PUT2(stamp[i]); i++; + last_depth=d; + } + else + { + if (c&POP_BIT) + { last_depth--; +#if SHOW_WRITE_TIMING + printf("!%d:%d:%d>%d}\n",j++,i,last_depth+1,last_depth); +#endif + } +#if SHOW_WRITE_TIMING + printf("!%d:%d:%d:%d>\n",j++,i,stamp[i]>>24,last_depth); +#endif + PUT4(stamp[i]);i++; + PUT4(stamp[i]);i++; + } + } +} + +@*1 Dumping the profiling information. + +We dump the number of files first and then dump +the file names including the +terminating zero byte. +We put eight byte into a memory word and dump them together. +The last memory word is padded with zeros. + +@<Dump the full file names@>= +{ two_halves hw; + int i,j; + hw.rh=file_num; + i=0; + for (k=0; k<=file_num; k++) + { j=strlen(file_num_name[k]); + if (j>i) i=j; + } + hw.lh=i; + dump_hh(hw); +} +{ memory_word m; + int word_count=0; + int byte_count=0; + m.w=0; + for (k=0;k<=file_num;k++) + { char *s=file_num_name[k]; + do + { m.w=(m.w<<8)|*s; + byte_count++; + if (byte_count==8) + { dump_wd(m); word_count++; + m.w=0; byte_count=0; + } + } while (*s++!=0); + } + if (byte_count >0) + { while (byte_count<8) + { m.w=(m.w<<8)|0; + byte_count++; + } + dump_wd(m);word_count++; + } + print_ln();print_int(file_num); + print(" file names dumped; total size "); print_int(word_count*8); +} + +@ @<Undump the full file names@>= + +{ two_halves hw; + memory_word m; + int byte_count=0; + int i,j; + char *buf; + undump_hh(hw); + file_num=hw.rh; + if (file_num>MAX_FILE_NUM) overflow("file number",file_num); + i=hw.lh; + buf=malloc(i+1); + if (buf==NULL) + { print_err("Out of memory while reading filenames from format file"); + succumb; + } + for (k=0;k<=file_num;k++) + { char *s=buf; + do + { if (byte_count==0) + { undump_wd(m); byte_count=8; } + *s=(m.w>>56)&0xFF; m.w=m.w<<8; + byte_count--; + } while (*s++!=0); + file_num_name[k]=strdup(buf); + if (file_num_name[k]==NULL) + { print_err("Out of memory while reading filenames from format file"); + succumb; + } + } + free(buf); +} + + +@ +Next we dump the file and line information from the |fl_mem| array. +Because some formats leave many unallocated memory words in the |avail| +list we dump only those memory words that are not on the avail list. +We set the entry |fl_mem[p]| to zero if |p| is on the |avail| list +while we traverse the list when dumping the memory words. +Besides the unallocated entries also entries that specify the unknown +file with line zero are completely zero. We do not dump these as well. + +When dumping an entry we set the topmost bit of the entry to 1. +An entry that has the topmost bit equal to zero contains the count +of the following zero entries. We dump entries in pairs since +the dump file is organized as a file of memory words + +@<Dump the file and line information@>= +{ int word_count=0; + k=hi_mem_min; + while (k<=mem_end) + { two_halves hw; + halfword e; + int word_count=0; + @<compute the next file line entry@>@; + hw.rh=e; + if (k>mem_end) e=0; + else + { @<compute the next file line entry@>@; } + hw.lh=e; + dump_hh(hw); word_count++; + } + print_ln(); print_int(word_count); + print(" words of file/line information dumped."); +} +@ @<compute the next file line entry@>= + if (fl_mem[k]!=0) e=fl_mem[k++]|0x80000000; + else + { int i; + i=1; k++; + while (k<=mem_end && fl_mem[k]==0) + { i++; k++; } + e=i; + } + +@ @<Undump the file and line information@>= +k=hi_mem_min; +while (k<=mem_end) +{ two_halves hw; + halfword e; + undump_hh(hw); + e=hw.rh; + @<get the next file line entry@>@; + if (k<=mem_end) + { e=hw.lh; + @<get the next file line entry@>@; + } +} + +@ @<get the next file line entry@>= +if (e&0x80000000) + fl_mem[k++]=e&~0x80000000; +else +{ int i; + i=e; + while (i>0) + {i--; k++;} +} + +@*1 Profiling \.{PDF} Specific Macros. +Macro packages providing \.{PDF} specific features typicaly test +whether the current engine is generating \.{PDF} output +before activating \.{PDF}-specific macros, and these macros +then use \.{PDF}-specific primitives. To be able to profile +these macros, the engine must provide (or at least pretend to provide) +the necessary primitives to make the test for \.{PDF} output succeed +and prevent the macros from failing because of undefined +primitives or unexpected behaviour. Generating \.{PDF} ouput +is usualy not required. + +The {\tt -pdf} option is designed to provide the necessary behaviour +by implementing replacements for the primitives of \pdfTeX. + +@<explain the options@>= + " -pdf "@/ + @t\qquad@>"\t pretend to be pdftex; requires -ini; implies -ltx\n"@/ + +@ This option will set the |pdf_on| variable, defined below, to true. + The option requires the {\tt -ini} option because its effect is just + the definition of additional primitives during initialization. It further + implies the {\tt -ltx} option because the primitives necesary to + run \LaTeX\ are part of \pdfTeX. + +@<handle the options@>= +else @+if (ARGUMENT_IS ("pdf")) @t\2@> + if (iniversion) pdf_on=ltxp=true; + else + { fprintf(stderr,"-pdf requires -ini; try -ini -pdf\n"); + exit(1); + } + +@ @<more options@>= + { "pdf", 0, 0, 0 }, + +@ @<Global variables@>= +static int @!pdf_on=false; + +@ Let us start with implementing the \.{PDF} version primitive. +This primitive uses the |last_item| command with a special modifier +\pdfTeX\ adds the codes for its extensions: |pdftex_version_code|, \dots +between \TeX's |badness_code| and \eTeX's |eTeX_int| codes. +Some codes like |elapsed_time_code| or |random_seed_code| are already defined above +but we duplicate them here for simplicity. +So here is the pdf version as well as all of PDF\TeX's command codes +for the |last_item| command: + +@d pdftex_version 140 /* \.{\\pdftexversion} */ +@d pdftex_revision "25" /* \.{\\pdftexrevision} */ +@d pdftex_version_string "-1.40.25" /*current \pdfTeX\ version*/ +@# +@d pdftex_first_rint_code (badness_code+1) /*base for \pdfTeX's command codes*/ +@d pdftex_version_code (pdftex_first_rint_code+0) /*code for \.{\\pdftexversion}*/ +@d pdf_last_obj_code (pdftex_first_rint_code+1) /*code for \.{\\pdflastobj}*/ +@d pdf_last_xform_code (pdftex_first_rint_code+2) /*code for \.{\\pdflastxform}*/ +@d pdf_last_ximage_code (pdftex_first_rint_code+3) /*code for \.{\\pdflastximage}*/ +@d pdf_last_ximage_pages_code (pdftex_first_rint_code+4) /*code for \.{\\pdflastximagepages}*/ +@d pdf_last_annot_code (pdftex_first_rint_code+5) /*code for \.{\\pdflastannot}*/ +@d pdf_retval_code (pdftex_first_rint_code+6) /*global multi-purpose return value*/ +@d pdf_last_ximage_colordepth_code (pdftex_first_rint_code+7) /*code for \.{\\pdflastximagecolordepth}*/ +@d pdf_last_link_code (pdftex_first_rint_code+8) /*code for \.{\\pdflastlink}*/ +@d pdftex_last_item_codes (pdftex_first_rint_code+8) /*end of \pdfTeX's command codes*/ + +@ Using these codes we can add the primitives: + +@<Put each...@>= +if (pdf_on) +{ +primitive("pdftexversion", last_item, pdftex_version_code);@/ +@!@:pdftex\_version\_}{\.{\\pdftexversion} primitive@> +primitive("pdflastobj", last_item, pdf_last_obj_code);@/ +@!@:pdf\_last\_obj\_}{\.{\\pdflastobj} primitive@> +primitive("pdflastxform", last_item, pdf_last_xform_code);@/ +@!@:pdf\_last\_xform\_}{\.{\\pdflastxform} primitive@> +primitive("pdflastximage", last_item, pdf_last_ximage_code);@/ +@!@:pdf\_last\_ximage\_}{\.{\\pdflastximage} primitive@> +primitive("pdflastximagepages", last_item, pdf_last_ximage_pages_code);@/ +@!@:pdf\_last\_ximage\_pages\_}{\.{\\pdflastximagepages} primitive@> +primitive("pdflastannot", last_item, pdf_last_annot_code);@/ +@!@:pdf\_last\_annot\_}{\.{\\pdflastannot} primitive@> +primitive("pdfretval", last_item, pdf_retval_code);@/ +@!@:pdf\_retval\_}{\.{\\pdfretval} primitive@> +primitive("pdflastximagecolordepth", last_item, pdf_last_ximage_colordepth_code);@/ +@!@:pdf\_last\_ximage\_colordepth\_}{\.{\\pdflastximagecolordepth} primitive@> +primitive("pdflastlink", last_item, pdf_last_link_code);@/ +@!@:pdf\_last\_link\_}{\.{\\pdflastlink} primitive@> +} + +@ Next we need to print the commands: + +@<Cases of |last_item| for |print_cmd_chr|@>= + case pdftex_version_code: print_esc("pdftexversion");@+break; + case pdf_last_obj_code: print_esc("pdflastobj");@+break; + case pdf_last_xform_code: print_esc("pdflastxform");@+break; + case pdf_last_ximage_code: print_esc("pdflastximage");@+break; + case pdf_last_ximage_pages_code: print_esc("pdflastximagepages");@+break; + case pdf_last_annot_code: print_esc("pdflastannot");@+break; + case pdf_retval_code: print_esc("pdfretval");@+break; + case pdf_last_ximage_colordepth_code: print_esc("pdflastximagecolordepth");@+break; + case pdf_last_link_code: print_esc("pdflastlink");@+break; + +@ The implementation needs a few global variables. + +@<Glob...@>= +static int +@!pdf_last_obj, +@!pdf_last_xform, +@!pdf_last_ximage, +@!pdf_last_ximage_pages, +@!pdf_last_annot, +@!pdf_retval, +@!pdf_last_ximage_colordepth, +@!pdf_last_link; + + +@ And this is sufficient to finish the implementation of this first batch of primitives: +@<Cases for fetching an integer value@>= + case pdftex_version_code: cur_val=pdftex_version;@+break; + case pdf_last_obj_code: cur_val=pdf_last_obj;@+break; + case pdf_last_xform_code: cur_val=pdf_last_xform;@+break; + case pdf_last_ximage_code: cur_val=pdf_last_ximage;@+break; + case pdf_last_ximage_pages_code: cur_val=pdf_last_ximage_pages;@+break; + case pdf_last_annot_code: cur_val=pdf_last_annot;@+break; + case pdf_retval_code: cur_val=pdf_retval;@+break; + case pdf_last_ximage_colordepth_code: cur_val=pdf_last_ximage_colordepth;@+break; + case pdf_last_link_code: cur_val=pdf_last_link;@+break; + + +@ The next group of primitves uses the assignment commands. We start +by defining the necessary command codes followed by the primitives. + +@d pdftex_first_loc tex_toks /*base for \pdfTeX's token list parameters*/ +@d pdf_pages_attr_loc (pdftex_first_loc+0) /*points to token list for \.{\\pdfpagesattr}*/ +@d pdf_page_attr_loc (pdftex_first_loc+1) /*points to token list for \.{\\pdfpageattr}*/ +@d pdf_page_resources_loc (pdftex_first_loc+2) /*points to token list for \.{\\pdfpageresources}*/ +@d pdf_pk_mode_loc (pdftex_first_loc+3) /*points to token list for \.{\\pdfpkmode}*/ +@d pdf_toks (pdftex_first_loc+4) /*end of \pdfTeX's token list parameters*/ +@# +@d pdftex_first_integer_code tex_int_pars /*base for \pdfTeX's integer parameters*/ +@d pdf_output_code (pdftex_first_integer_code+0) /*switch on PDF output if positive*/ +@d pdf_compress_level_code (pdftex_first_integer_code+1) /*compress level of streams*/ +@d pdf_decimal_digits_code (pdftex_first_integer_code+2) /*digits after the decimal point of numbers*/ +@d pdf_move_chars_code (pdftex_first_integer_code+3) /*move chars 0..31 to higher area if possible*/ +@d pdf_image_resolution_code (pdftex_first_integer_code+4) /*default image resolution*/ +@d pdf_pk_resolution_code (pdftex_first_integer_code+5) /*default resolution of PK font*/ +@d pdf_unique_resname_code (pdftex_first_integer_code+6) /*generate unique names for resouces*/ +@d pdf_option_always_use_pdfpagebox_code (pdftex_first_integer_code+7) /*if the PDF inclusion should always use a specific PDF page box*/ +@d pdf_option_pdf_inclusion_errorlevel_code (pdftex_first_integer_code+8) /*if the PDF inclusion should treat pdfs newer than |pdf_minor_version| as an error*/ +@d pdf_major_version_code (pdftex_first_integer_code+9) /*integer part of the PDF version produced*/ +@d pdf_minor_version_code (pdftex_first_integer_code+10) /*fractional part of the PDF version produced*/ +@d pdf_force_pagebox_code (pdftex_first_integer_code+11) /*if the PDF inclusion should always use a specific PDF page box*/ +@d pdf_pagebox_code (pdftex_first_integer_code+12) /*default pagebox to use for PDF inclusion*/ +@d pdf_inclusion_errorlevel_code (pdftex_first_integer_code+13) /*if the PDF inclusion should treat pdfs newer than |pdf_minor_version| as an error*/ +@d pdf_gamma_code (pdftex_first_integer_code+14) +@d pdf_image_gamma_code (pdftex_first_integer_code+15) +@d pdf_image_hicolor_code (pdftex_first_integer_code+16) +@d pdf_image_apply_gamma_code (pdftex_first_integer_code+17) +@d pdf_adjust_spacing_code (pdftex_first_integer_code+18) /*level of spacing adjusting*/ +@d pdf_protrude_chars_code (pdftex_first_integer_code+19) /*protrude chars at left/right edge of paragraphs*/ +@d pdf_tracing_fonts_code (pdftex_first_integer_code+20) /*level of font detail in log*/ +@d pdf_objcompresslevel_code (pdftex_first_integer_code+21) /*activate object streams*/ +@d pdf_adjust_interword_glue_code (pdftex_first_integer_code+22) /*adjust interword glue?*/ +@d pdf_prepend_kern_code (pdftex_first_integer_code+23) /*prepend kern before certain characters?*/ +@d pdf_append_kern_code (pdftex_first_integer_code+24) /*append kern before certain characters?*/ +@d pdf_gen_tounicode_code (pdftex_first_integer_code+25) /*generate ToUnicode for fonts?*/ +@d pdf_draftmode_code (pdftex_first_integer_code+26) /*switch on draftmode if positive*/ +@d pdf_inclusion_copy_font_code (pdftex_first_integer_code+27) /*generate ToUnicode for fonts?*/ +@d pdf_suppress_warning_dup_dest_code (pdftex_first_integer_code+28) /*suppress warning about duplicated destinations*/ +@d pdf_suppress_warning_dup_map_code (pdftex_first_integer_code+29) /*suppress warning about duplicated map lines*/ +@d pdf_suppress_warning_page_group_code (pdftex_first_integer_code+30) /*suppress warning about multiple pdfs with page group*/ +@d pdf_info_omit_date_code (pdftex_first_integer_code+31) /*omit generating CreationDate and ModDate*/ +@d pdf_suppress_ptex_info_code (pdftex_first_integer_code+32) /*suppress /PTEX.* entries in PDF dictionaries*/ +@d pdf_omit_charset_code (pdftex_first_integer_code+33) /*suppress /PTEX.* entries in PDF dictionaries*/ +@d pdf_omit_info_dict_code (pdftex_first_integer_code+34) /*suppress /PTEX.* entries in PDF dictionaries*/ +@d pdf_omit_procset_code (pdftex_first_integer_code+35) /*suppress /PTEX.* entries in PDF dictionaries*/ +@d pdf_int_pars (pdftex_first_integer_code+36) /*total number of \pdfTeX's integer parameters*/ +@# +@d pdftex_first_dimen_code 23 /*first number defined in this section*/ +@d pdf_h_origin_code (pdftex_first_dimen_code+0) /*horigin of the PDF output*/ +@d pdf_v_origin_code (pdftex_first_dimen_code+1) /*vorigin of the PDF output*/ +@d pdf_link_margin_code (pdftex_first_dimen_code+2) /*link margin in the PDF output*/ +@d pdf_dest_margin_code (pdftex_first_dimen_code+3) /*dest margin in the PDF output*/ +@d pdf_thread_margin_code (pdftex_first_dimen_code+4) /*thread margin in the PDF output*/ +@d pdf_first_line_height_code (pdftex_first_dimen_code+5) +@d pdf_last_line_depth_code (pdftex_first_dimen_code+6) +@d pdf_each_line_height_code (pdftex_first_dimen_code+7) +@d pdf_each_line_depth_code (pdftex_first_dimen_code+8) +@d pdf_ignored_dimen_code (pdftex_first_dimen_code+9) +@d pdf_px_dimen_code (pdftex_first_dimen_code+10) +@d pdftex_last_dimen_code (pdftex_first_dimen_code+10) /*last number defined in this section*/ +@d dimen_pars (pdftex_last_dimen_code+1) /*total number of dimension parameters*/ + +@<Put each...@>= +if (pdf_on) +{ +primitive("pdfpagesattr", assign_toks, pdf_pages_attr_loc); +@!@:pdf\_pages\_attr\_}{\.{\\pdfpagesattr} primitive@> +primitive("pdfpageattr", assign_toks, pdf_page_attr_loc); +@!@:pdf\_page\_attr\_}{\.{\\pdfpageattr} primitive@> +primitive("pdfpageresources", assign_toks, pdf_page_resources_loc); +@!@:pdf\_page\_resources\_}{\.{\\pdfpageresources} primitive@> +primitive("pdfpkmode", assign_toks, pdf_pk_mode_loc); +@!@:pdf\_pk\_mode\_}{\.{\\pdfpkmode} primitive@> +@# +primitive("pdfoutput", assign_int, int_base+pdf_output_code);@/ +@!@:pdf\_output\_}{\.{\\pdfoutput} primitive@> +primitive("pdfcompresslevel", assign_int, int_base+pdf_compress_level_code);@/ +@!@:pdf\_compress\_level\_}{\.{\\pdfcompresslevel} primitive@> +primitive("pdfobjcompresslevel", assign_int, int_base+pdf_objcompresslevel_code);@/ +@!@:pdf\_objcompresslevel\_}{\.{\\pdfobjcompresslevel} primitive@> +primitive("pdfdecimaldigits", assign_int, int_base+pdf_decimal_digits_code);@/ +@!@:pdf\_decimal\_digits\_}{\.{\\pdfdecimaldigits} primitive@> +primitive("pdfmovechars", assign_int, int_base+pdf_move_chars_code);@/ +@!@:pdf\_move\_chars\_}{\.{\\pdfmovechars} primitive@> +primitive("pdfimageresolution", assign_int, int_base+pdf_image_resolution_code);@/ +@!@:pdf\_image\_resolution\_}{\.{\\pdfimageresolution} primitive@> +primitive("pdfpkresolution", assign_int, int_base+pdf_pk_resolution_code);@/ +@!@:pdf\_pk\_resolution\_}{\.{\\pdfpkresolution} primitive@> +primitive("pdfuniqueresname", assign_int, int_base+pdf_unique_resname_code);@/ +@!@:pdf\_unique\_resname\_}{\.{\\pdfuniqueresname} primitive@> +primitive("pdfoptionpdfminorversion", assign_int, int_base+pdf_minor_version_code);@/ +@!@:pdf\_minor\_version\_}{\.{\\pdfoptionpdfminorversion} primitive@> +primitive("pdfoptionalwaysusepdfpagebox", assign_int, int_base+pdf_option_always_use_pdfpagebox_code);@/ +@!@:pdf\_option\_always\_use\_pdfpagebox\_}{\.{\\pdfoptionalwaysusepdfpagebox} primitive@> +primitive("pdfoptionpdfinclusionerrorlevel", assign_int, int_base+pdf_option_pdf_inclusion_errorlevel_code);@/ +@!@:pdf\_option\_pdf\_inclusion\_errorlevel\_}{\.{\\pdfoptionpdfinclusionerrorlevel} primitive@> +primitive("pdfmajorversion", assign_int, int_base+pdf_major_version_code);@/ +@!@:pdf\_major\_version\_}{\.{\\pdfmajorversion} primitive@> +primitive("pdfminorversion", assign_int, int_base+pdf_minor_version_code);@/ +@!@:pdf\_minor\_version\_}{\.{\\pdfminorversion} primitive@> +primitive("pdfforcepagebox", assign_int, int_base+pdf_force_pagebox_code);@/ +@!@:pdf\_force\_pagebox\_}{\.{\\pdfforcepagebox} primitive@> +primitive("pdfpagebox", assign_int, int_base+pdf_pagebox_code);@/ +@!@:pdf\_pagebox\_}{\.{\\pdfpagebox} primitive@> +primitive("pdfinclusionerrorlevel", assign_int, int_base+pdf_inclusion_errorlevel_code);@/ +@!@:pdf\_inclusion\_errorlevel\_}{\.{\\pdfinclusionerrorlevel} primitive@> +primitive("pdfgamma", assign_int, int_base+pdf_gamma_code);@/ +@!@:pdf\_gamma\_}{\.{\\pdfgamma} primitive@> +@!@:pdf\_gamma\_}{\.{\\pdfgamma} primitive@> +primitive("pdfimagegamma", assign_int, int_base+pdf_image_gamma_code);@/ +@!@:pdf\_image\_gamma\_}{\.{\\pdfimagegamma} primitive@> +primitive("pdfimagehicolor", assign_int, int_base+pdf_image_hicolor_code);@/ +@!@:pdf\_image\_hicolor\_}{\.{\\pdfimagehicolor} primitive@> +primitive("pdfimageapplygamma", assign_int, int_base+pdf_image_apply_gamma_code);@/ +@!@:pdf\_image\_apply\_gamma\_}{\.{\\pdfimageapplygamma} primitive@> +primitive("pdfadjustspacing", assign_int, int_base+pdf_adjust_spacing_code);@/ +@!@:pdf\_adjust\_spacing\_}{\.{\\pdfadjustspacing} primitive@> +primitive("pdfprotrudechars", assign_int, int_base+pdf_protrude_chars_code);@/ +@!@:pdf\_protrude\_chars\_}{\.{\\pdfprotrudechars} primitive@> +primitive("pdftracingfonts", assign_int, int_base+pdf_tracing_fonts_code);@/ +@!@:pdf\_tracing\_fonts\_}{\.{\\pdftracingfonts} primitive@> +primitive("pdfadjustinterwordglue", assign_int, int_base+pdf_adjust_interword_glue_code);@/ +@!@:pdf\_adjust\_interword\_glue\_}{\.{\\pdfadjustinterwordglue} primitive@> +primitive("pdfprependkern", assign_int, int_base+pdf_prepend_kern_code);@/ +@!@:pdf\_prepend\_kern\_}{\.{\\pdfprependkern} primitive@> +primitive("pdfappendkern", assign_int, int_base+pdf_append_kern_code);@/ +@!@:pdf\_append\_kern\_}{\.{\\pdfappendkern} primitive@> +primitive("pdfgentounicode", assign_int, int_base+pdf_gen_tounicode_code);@/ +@!@:pdf\_gen\_tounicode\_}{\.{\\pdfgentounicode} primitive@> +primitive("pdfdraftmode", assign_int, int_base+pdf_draftmode_code);@/ +@!@:pdf\_draftmode\_}{\.{\\pdfdraftmode} primitive@> +primitive("pdfinclusioncopyfonts", assign_int, int_base+pdf_inclusion_copy_font_code);@/ +@!@:pdf\_inclusion\_copy\_font\_}{\.{\\pdfinclusioncopyfonts} primitive@> +primitive("pdfsuppresswarningdupdest", assign_int, int_base+pdf_suppress_warning_dup_dest_code);@/ +@!@:pdf\_suppress\_warning\_dup\_dest\_}{\.{\\pdfsuppresswarningdupdest} primitive@> +primitive("pdfsuppresswarningdupmap", assign_int, int_base+pdf_suppress_warning_dup_map_code);@/ +@!@:pdf\_suppress\_warning\_dup\_map\_}{\.{\\pdfsuppresswarningdupmap} primitive@> +primitive("pdfsuppresswarningpagegroup", assign_int, int_base+pdf_suppress_warning_page_group_code);@/ +@!@:pdf\_suppress\_warning\_page\_group\_}{\.{\\pdfsuppresswarningpagegroup} primitive@> +primitive("pdfinfoomitdate", assign_int, int_base+pdf_info_omit_date_code);@/ +@!@:pdf\_info\_omit\_date\_}{\.{\\pdfinfoomitdate} primitive@> +primitive("pdfsuppressptexinfo", assign_int, int_base+pdf_suppress_ptex_info_code);@/ +@!@:pdf\_suppress\_ptex\_info\_}{\.{\\pdfsuppressptexinfo} primitive@> +primitive("pdfomitcharset", assign_int, int_base+pdf_omit_charset_code);@/ +@!@:pdf\_omit\_charset}{\.{\\pdfomitcharset} primitive@> +primitive("pdfomitinfodict", assign_int, int_base+pdf_omit_info_dict_code);@/ +@!@:pdf\_omit\_info\_dict}{\.{\\pdfomitinfodict} primitive@> +primitive("pdfomitprocset", assign_int, int_base+pdf_omit_procset_code);@/ +@!@:pdf\_omit\_procset}{\.{\\pdfomitprocset} primitive@> +@# +primitive("pdfhorigin", assign_dimen, dimen_base+pdf_h_origin_code);@/ +@!@:pdf\_h\_origin\_}{\.{\\pdfhorigin} primitive@> +primitive("pdfvorigin", assign_dimen, dimen_base+pdf_v_origin_code);@/ +@!@:pdf\_v\_origin\_}{\.{\\pdfvorigin} primitive@> +primitive("pdflinkmargin", assign_dimen, dimen_base+pdf_link_margin_code);@/ +@!@:pdf\_link\_margin\_}{\.{\\pdflinkmargin} primitive@> +primitive("pdfdestmargin", assign_dimen, dimen_base+pdf_dest_margin_code);@/ +@!@:pdf\_dest\_margin\_}{\.{\\pdfdestmargin} primitive@> +primitive("pdfthreadmargin", assign_dimen, dimen_base+pdf_thread_margin_code);@/ +@!@:pdf\_thread\_margin\_}{\.{\\pdfthreadmargin} primitive@> +primitive("pdffirstlineheight", assign_dimen, dimen_base+pdf_first_line_height_code);@/ +@!@:pdf\_first\_line\_height\_}{\.{\\pdffirstlineheight} primitive@> +primitive("pdflastlinedepth", assign_dimen, dimen_base+pdf_last_line_depth_code);@/ +@!@:pdf\_last\_line\_depth\_}{\.{\\pdflastlinedepth} primitive@> +primitive("pdfeachlineheight", assign_dimen, dimen_base+pdf_each_line_height_code);@/ +@!@:pdf\_each\_line\_height\_}{\.{\\pdfeachlineheight} primitive@> +primitive("pdfeachlinedepth", assign_dimen, dimen_base+pdf_each_line_depth_code);@/ +@!@:pdf\_each\_line\_depth\_}{\.{\\pdfeachlinedepth} primitive@> +primitive("pdfignoreddimen", assign_dimen, dimen_base+pdf_ignored_dimen_code);@/ +@!@:pdf\_ignored\_dimen\_}{\.{\\pdfignoreddimen} primitive@> +primitive("pdfpxdimen", assign_dimen, dimen_base+pdf_px_dimen_code);@/ +@!@:pdf\_px\_dimen\_}{\.{\\pdfpxdimen} primitive@> +primitive("ifpdfprimitive", if_test, if_primitive_code); +@!@:if\_primitive\_}{\.{\\if} primitive@> + + +} + +@ As before we add cases to the printing routines. + +@<Cases of |assign_toks| for |print_cmd_chr|@>= + case pdf_pages_attr_loc: print_esc("pdfpagesattr");@+break; + case pdf_page_attr_loc: print_esc("pdfpageattr");@+break; + case pdf_page_resources_loc: print_esc("pdfpageresources");@+break; + case pdf_pk_mode_loc: print_esc("pdfpkmode");@+break; + +@ @<Cases for |print_param|@>= +case pdf_output_code: print_esc("pdfoutput");@+break; +case pdf_compress_level_code: print_esc("pdfcompresslevel");@+break; +case pdf_objcompresslevel_code: print_esc("pdfobjcompresslevel");@+break; +case pdf_decimal_digits_code: print_esc("pdfdecimaldigits");@+break; +case pdf_move_chars_code: print_esc("pdfmovechars");@+break; +case pdf_image_resolution_code: print_esc("pdfimageresolution");@+break; +case pdf_pk_resolution_code: print_esc("pdfpkresolution");@+break; +case pdf_unique_resname_code: print_esc("pdfuniqueresname");@+break; +case pdf_option_always_use_pdfpagebox_code: print_esc("pdfoptionalwaysusepdfpagebox");@+break; +case pdf_option_pdf_inclusion_errorlevel_code: print_esc("pdfoptionpdfinclusionerrorlevel");@+break; +case pdf_major_version_code: print_esc("pdfmajorversion");@+break; +case pdf_minor_version_code: print_esc("pdfminorversion");@+break; +case pdf_force_pagebox_code: print_esc("pdfforcepagebox");@+break; +case pdf_pagebox_code: print_esc("pdfpagebox");@+break; +case pdf_inclusion_errorlevel_code: print_esc("pdfinclusionerrorlevel");@+break; +case pdf_gamma_code: print_esc("pdfgamma");@+break; +case pdf_image_gamma_code: print_esc("pdfimagegamma");@+break; +case pdf_image_hicolor_code: print_esc("pdfimagehicolor");@+break; +case pdf_image_apply_gamma_code: print_esc("pdfimageapplygamma");@+break; +case pdf_adjust_spacing_code: print_esc("pdfadjustspacing");@+break; +case pdf_protrude_chars_code: print_esc("pdfprotrudechars");@+break; +case pdf_tracing_fonts_code: print_esc("pdftracingfonts");@+break; +case pdf_adjust_interword_glue_code: print_esc("pdfadjustinterwordglue");@+break; +case pdf_prepend_kern_code: print_esc("pdfprependkern");@+break; +case pdf_append_kern_code: print_esc("pdfappendkern");@+break; +case pdf_gen_tounicode_code: print_esc("pdfgentounicode");@+break; +case pdf_draftmode_code: print_esc("pdfdraftmode");@+break; +case pdf_inclusion_copy_font_code: print_esc("pdfinclusioncopyfonts");@+break; +case pdf_suppress_warning_dup_dest_code: print_esc("pdfsuppresswarningdupdest");@+break; +case pdf_suppress_warning_dup_map_code: print_esc("pdfsuppresswarningdupmap");@+break; +case pdf_suppress_warning_page_group_code: print_esc("pdfsuppresswarningpagegroup");@+break; +case pdf_info_omit_date_code: print_esc("pdfinfoomitdate");@+break; +case pdf_suppress_ptex_info_code: print_esc("pdfsuppressptexinfo");@+break; +case pdf_omit_charset_code: print_esc("pdfomitcharset");@+break; +case pdf_omit_info_dict_code: print_esc("pdfomitinfodict");@+break; +case pdf_omit_procset_code: print_esc("pdfomitprocset");@+break; + +@ @<Cases for |print_lenght_param|@>= +case pdf_h_origin_code: print_esc("pdfhorigin");@+break; +case pdf_v_origin_code: print_esc("pdfvorigin");@+break; +case pdf_link_margin_code: print_esc("pdflinkmargin");@+break; +case pdf_dest_margin_code: print_esc("pdfdestmargin");@+break; +case pdf_thread_margin_code: print_esc("pdfthreadmargin");@+break; +case pdf_first_line_height_code: print_esc("pdffirstlineheight");@+break; +case pdf_last_line_depth_code: print_esc("pdflastlinedepth");@+break; +case pdf_each_line_height_code: print_esc("pdfeachlineheight");@+break; +case pdf_each_line_depth_code: print_esc("pdfeachlinedepth");@+break; +case pdf_ignored_dimen_code: print_esc("pdfignoreddimen");@+break; +case pdf_px_dimen_code: print_esc("pdfpxdimen");@+break; + +@ It remains to initialize some of these entries. + +@<Initialize table entries...@>= +dimen_par(pdf_h_origin_code)=4736287; /* 0.5 inch */ +dimen_par(pdf_v_origin_code)=4736287; +int_par(pdf_compress_level_code)=9; +int_par(pdf_objcompresslevel_code)=0; +int_par(pdf_decimal_digits_code)=3; +int_par(pdf_image_resolution_code)=72; +int_par(pdf_major_version_code)=1; +int_par(pdf_minor_version_code)=4; +int_par(pdf_gamma_code)=1000; +int_par(pdf_image_gamma_code)=2200; +int_par(pdf_image_hicolor_code)=1; +int_par(pdf_image_apply_gamma_code)=0; +int_par(pdf_draftmode_code)=0; +dimen_par(pdf_px_dimen_code)=65782; /* 1bp */ + +@ The next class of primitives extend the |convert| comand. +These codes go in between |Prote_last_convert_code| and |job_name_code|. + +@d pdftex_first_convert_code (Prote_last_convert_code+1) /*base for \pdfTeX's command codes*/ +@d pdftex_revision_code (pdftex_first_convert_code+0) /*command code for \.{\\pdftexrevision}*/ +@d pdftex_banner_code (pdftex_first_convert_code+1) /*command code for \.{\\pdftexbanner}*/ +@d pdf_font_name_code (pdftex_first_convert_code+2) /*command code for \.{\\pdffontname}*/ +@d pdf_font_objnum_code (pdftex_first_convert_code+3) /*command code for \.{\\pdffontobjnum}*/ +@d pdf_font_size_code (pdftex_first_convert_code+4) /*command code for \.{\\pdffontsize}*/ +@d pdf_page_ref_code (pdftex_first_convert_code+5) /*command code for \.{\\pdfpageref}*/ +@d pdf_xform_name_code (pdftex_first_convert_code+6) /*command code for \.{\\pdfxformname}*/ +@d pdf_escape_string_code (pdftex_first_convert_code+7) /*command code for \.{\\pdfescapestring}*/ +@d pdf_escape_name_code (pdftex_first_convert_code+8) /*command code for \.{\\pdfescapename}*/ +@d left_margin_kern_code (pdftex_first_convert_code+9) /*command code for \.{\\leftmarginkern}*/ +@d right_margin_kern_code (pdftex_first_convert_code+10) /*command code for \.{\\rightmarginkern}*/ +@d pdf_colorstack_init_code (pdftex_first_convert_code+11) /*command code for \.{\\pdfcolorstackinit}*/ +@d pdf_escape_hex_code (pdftex_first_convert_code+12) /*command code for \.{\\pdfescapehex}*/ +@d pdf_unescape_hex_code (pdftex_first_convert_code+13) /*command code for \.{\\pdfunescapehex}*/ +@d pdf_match_code (pdftex_first_convert_code+14) /*command code for \.{\\pdfmatch}*/ +@d pdf_last_match_code (pdftex_first_convert_code+15) /*command code for \.{\\pdflastmatch}*/ +@d pdf_insert_ht_code (pdftex_first_convert_code+16) /*command code for \.{\\pdfinsertht}*/ +@d pdf_ximage_bbox_code (pdftex_first_convert_code+17) /*command code for \.{\\pdfximagebbox}*/ +@d pdftex_convert_codes (pdftex_first_convert_code+18) /*end of \pdfTeX's command codes*/ + + +@<Put each...@>= +if (pdf_on) +{ +primitive("pdftexrevision", convert, pdftex_revision_code);@/ +@!@:pdftex\_revision\_}{\.{\\pdftexrevision} primitive@> +primitive("pdftexbanner", convert, pdftex_banner_code);@/ +@!@:pdftex\_banner\_}{\.{\\pdftexbanner} primitive@> +primitive("pdffontname", convert, pdf_font_name_code);@/ +@!@:pdf\_font\_name\_}{\.{\\pdffontname} primitive@> +primitive("pdffontobjnum", convert, pdf_font_objnum_code);@/ +@!@:pdf\_font\_objnum\_}{\.{\\pdffontobjnum} primitive@> +primitive("pdffontsize", convert, pdf_font_size_code);@/ +@!@:pdf\_font\_size\_}{\.{\\pdffontsize} primitive@> +primitive("pdfpageref", convert, pdf_page_ref_code);@/ +@!@:pdf\_page\_ref\_}{\.{\\pdfpageref} primitive@> +primitive("leftmarginkern", convert, left_margin_kern_code);@/ +@!@:left\_margin\_kern\_}{\.{\\leftmarginkern} primitive@> +primitive("rightmarginkern", convert, right_margin_kern_code);@/ +@!@:right\_margin\_kern\_}{\.{\\rightmarginkern} primitive@> +primitive("pdfxformname", convert, pdf_xform_name_code);@/ +@!@:pdf\_xform\_name\_}{\.{\\pdfxformname} primitive@> +primitive("pdfescapestring", convert, pdf_escape_string_code);@/ +@!@:pdf\_escape\_string\_}{\.{\\pdfescapestring} primitive@> +primitive("pdfescapename", convert, pdf_escape_name_code);@/ +@!@:pdf\_escape\_name\_}{\.{\\pdfescapename} primitive@> +primitive("pdfescapehex", convert, pdf_escape_hex_code);@/ +@!@:pdf\_escape\_hex\_}{\.{\\pdfescapehex} primitive@> +primitive("pdfunescapehex", convert, pdf_unescape_hex_code);@/ +@!@:pdf\_unescape\_hex\_}{\.{\\pdfunescapehex} primitive@> +primitive("pdfmatch", convert, pdf_match_code);@/ +@!@:pdf\_match\_}{\.{\\pdfmatch} primitive@> +primitive("pdflastmatch", convert, pdf_last_match_code);@/ +@!@:pdf\_last\_match\_}{\.{\\pdflastmatch} primitive@> +primitive("pdfcolorstackinit", convert, pdf_colorstack_init_code);@/ +@!@:pdf\_colorstack\_init\_}{\.{\\pdfcolorstackinit} primitive@> +} + +@ The usual code for printing: + +@<Cases of |convert| for |print_cmd_chr|@>= + case pdftex_revision_code: print_esc("pdftexrevision");@+break; + case pdftex_banner_code: print_esc("pdftexbanner");@+break; + case pdf_font_name_code: print_esc("pdffontname");@+break; + case pdf_font_objnum_code: print_esc("pdffontobjnum");@+break; + case pdf_font_size_code: print_esc("pdffontsize");@+break; + case pdf_page_ref_code: print_esc("pdfpageref");@+break; + case left_margin_kern_code: print_esc("leftmarginkern");@+break; + case right_margin_kern_code: print_esc("rightmarginkern");@+break; + case pdf_xform_name_code: print_esc("pdfxformname");@+break; + case pdf_escape_string_code: print_esc("pdfescapestring");@+break; + case pdf_escape_name_code: print_esc("pdfescapename");@+break; + case pdf_escape_hex_code: print_esc("pdfescapehex");@+break; + case pdf_unescape_hex_code: print_esc("pdfunescapehex");@+break; + case pdf_match_code: print_esc("pdfmatch");@+break; + case pdf_last_match_code: print_esc("pdflastmatch");@+break; + case pdf_colorstack_init_code: print_esc("pdfcolorstackinit");@+break; + case pdf_insert_ht_code: print_esc("pdfinsertht");@+break; + case pdf_ximage_bbox_code: print_esc("pdfximagebbox");@+break; + +@ The following code is taken from pdftex. At this point, I should drop +some of the primitives that I do not want to implement. +To skip general text we use the following macro + + +@<Cases of `Scan the argument for command |c|'@>= +case pdftex_revision_code: do_nothing;@+break; +case pdftex_banner_code: do_nothing;@+break; +case pdf_font_name_code: case pdf_font_objnum_code: + case pdf_font_size_code: {@+ + scan_font_ident(); + if (cur_val==null_font) + pdf_error("font","invalid font identifier"); +} @+break; +case pdf_page_ref_code: {@+ + scan_int(); + if (cur_val <= 0) + pdf_error("pageref","invalid page number"); +} @+break; +case left_margin_kern_code: case right_margin_kern_code: {@+ + pointer p; + scan_register_num(); + fetch_box(p); + if ((p==null)||(type(p)!=hlist_node)) + pdf_error("marginkern","a non-empty hbox expected"); +} @+break; +case pdf_xform_name_code: {@+ + scan_int(); +} @+break; +case pdf_escape_string_code: +case pdf_escape_name_code: +case pdf_escape_hex_code: +case pdf_unescape_hex_code: + scan_general_x_text(); /*the simplified version*/ + ins_list(link(link(garbage))); + free_avail(link(garbage)); /*drop reference count*/ + return; +case pdf_match_code: + scan_keyword("icase"); + if (scan_keyword("subcount")) scan_int(); + scan_pdf_ext_toks(); /*the simplified version*/ + scan_pdf_ext_toks(); /*the simplified version*/ + break; +case pdf_last_match_code: + {@+pointer p,q; + scan_int(); + /* always returning ``\.{-1->}''*/ + p=temp_head;link(p)=null; + store_new_token(other_token+'-'); + store_new_token(other_token+'1'); + store_new_token(other_token+'-'); + store_new_token(other_token+'>'); + ins_list(link(temp_head)); + return; + } +case pdf_colorstack_init_code: + {@+ + scan_keyword("page"); + if (!scan_keyword("direct")) + scan_keyword("page"); + scan_pdf_ext_toks(); /*the simplified version*/ + cur_val=0; + } @+break; +case pdf_insert_ht_code: scan_register_num();@+break; +case pdf_ximage_bbox_code: {@+ + scan_int(); + scan_int(); +}@+break; + + +@ This is the ``dummy'' |scan_pdf_ext_toks| routine we used above +and a variation of it which we need later. + +@<Declare procedures needed in |do_ext...@>= +static void scan_pdf_ext_toks(void) +{ scan_toks(false,true); /*like \.{\\special}*/ + flush_list(def_ref); +} +static void scan_pdf_ext_late_toks(void) +{ scan_toks(false, false); /*like \.{\\special}, but doesn't expand*/ + flush_list(def_ref); +} + + +@ The second part of handling conversion commands is the printing of the result. + +@<Cases of `Print the result of command |c|'@>= +case pdftex_revision_code: print(pdftex_revision);@+break; +case pdftex_banner_code: print("This is pdfTeX, Version 3.141592653");@+break; +case pdf_font_name_code: case pdf_font_objnum_code: print_int(cur_val);@+break; +case pdf_font_size_code: + print_scaled(font_size[cur_val]); + print("pt");@+break; +case pdf_page_ref_code: print_int(1);@+break; +case pdf_xform_name_code: print_int(cur_val);@+break; +case pdf_escape_string_code: +case pdf_escape_name_code: +case left_margin_kern_code: print("0pt");@+break; +case right_margin_kern_code: print("0pt");@+break; +case pdf_colorstack_init_code: print_int(cur_val);@+break; +case pdf_escape_hex_code: +case pdf_unescape_hex_code: +case pdf_match_code: +case pdf_last_match_code: +case pdf_insert_ht_code: print("10pt");@+break; +case pdf_ximage_bbox_code: print("10pt");@+break; + + +@ A few functions are neede to complete the implementation of the \pdfTeX\ simulation. + + +@<Error handling procedures@>= +static void pdf_error(char *t, char *p) +{@+ + normalize_selector(); + print_err("pdfTeX error"); + if (t!=0) {@+ + print(" ("); + print(t); + print(")"); + } + print(": ");print(p); + succumb; +} + + +@ The last command we need to consider is the |extension| command. + +@d pdf_literal_node (pdftex_first_extension_code+0) + +@d pdf_lateliteral_node (pdftex_first_extension_code+1) /*Not needed*/ + +@d pdf_obj_code (pdftex_first_extension_code+2) +@d pdf_refobj_node (pdftex_first_extension_code+3) +@d pdf_xform_code (pdftex_first_extension_code+4) +@d pdf_refxform_node (pdftex_first_extension_code+5) +@d pdf_ximage_code (pdftex_first_extension_code+6) +@d pdf_refximage_node (pdftex_first_extension_code+7) +@d pdf_annot_node (pdftex_first_extension_code+8) +@d pdf_start_link_node (pdftex_first_extension_code+9) +@d pdf_end_link_node (pdftex_first_extension_code+10) +@d pdf_outline_code (pdftex_first_extension_code+11) +@d pdf_dest_node (pdftex_first_extension_code+12) +@d pdf_thread_node (pdftex_first_extension_code+13) +@d pdf_start_thread_node (pdftex_first_extension_code+14) +@d pdf_end_thread_node (pdftex_first_extension_code+15) + +@d pdf_info_code (pdftex_first_extension_code+16) +@d pdf_catalog_code (pdftex_first_extension_code+17) +@d pdf_names_code (pdftex_first_extension_code+18) + +@d pdf_font_attr_code (pdftex_first_extension_code+19) +@d pdf_include_chars_code (pdftex_first_extension_code+20) +@d pdf_map_file_code (pdftex_first_extension_code+21) +@d pdf_map_line_code (pdftex_first_extension_code+22) +@d pdf_trailer_code (pdftex_first_extension_code+23) +@d pdf_trailer_id_code (pdftex_first_extension_code+24) + +@d pdf_font_expand_code (pdftex_first_extension_code+25) + +@d pdf_snap_ref_point_node (pdftex_first_extension_code+26) +@d pdf_snapy_node (pdftex_first_extension_code+27) +@d pdf_snapy_comp_node (pdftex_first_extension_code+28) +@d pdf_glyph_to_unicode_code (pdftex_first_extension_code+29) +@d pdf_colorstack_node (pdftex_first_extension_code+30) +@d pdf_setmatrix_node (pdftex_first_extension_code+31) +@d pdf_save_node (pdftex_first_extension_code+32) +@d pdf_restore_node (pdftex_first_extension_code+33) +@d pdf_nobuiltin_tounicode_code (pdftex_first_extension_code+34) +@d pdf_interword_space_on_node (pdftex_first_extension_code+35) +@d pdf_interword_space_off_node (pdftex_first_extension_code+36) +@d pdf_fake_space_node (pdftex_first_extension_code+37) +@d pdf_running_link_off_node (pdftex_first_extension_code+38) +@d pdf_running_link_on_node (pdftex_first_extension_code+39) +@d pdf_space_font_code (pdftex_first_extension_code+40) +@# +@d tracing_stack_level_code (pdftex_first_extension_code+41) +@d pdf_par_token_context_code (pdftex_first_extension_code+42) +@d pdf_par_token_name_code (pdftex_first_extension_code+43) +@d pdf_show_stream_code (pdftex_first_extension_code+44) +@# +@d pdftex_last_extension_code (pdftex_first_extension_code+44) + +@<Put each...@>= +if (pdf_on) +{ +primitive("pdfliteral", extension, pdf_literal_node);@/ +@!@:pdf\_literal\_}{\.{\\pdfliteral} primitive@> +primitive("pdfobj", extension, pdf_obj_code);@/ +@!@:pdf\_obj\_}{\.{\\pdfobj} primitive@> +primitive("pdfrefobj", extension, pdf_refobj_node);@/ +@!@:pdf\_refobj\_}{\.{\\pdfrefobj} primitive@> +primitive("pdfxform", extension, pdf_xform_code);@/ +@!@:pdf\_xform\_}{\.{\\pdfxform} primitive@> +primitive("pdfrefxform", extension, pdf_refxform_node);@/ +@!@:pdf\_refxform\_}{\.{\\pdfrefxform} primitive@> +primitive("pdfximage", extension, pdf_ximage_code);@/ +@!@:pdf\_ximage\_}{\.{\\pdfximage} primitive@> +primitive("pdfrefximage", extension, pdf_refximage_node);@/ +@!@:pdf\_refximage\_}{\.{\\pdfrefximage} primitive@> +primitive("pdfannot", extension, pdf_annot_node);@/ +@!@:pdf\_annot\_}{\.{\\pdfannot} primitive@> +primitive("pdfstartlink", extension, pdf_start_link_node);@/ +@!@:pdf\_start\_link\_}{\.{\\pdfstartlink} primitive@> +primitive("pdfendlink", extension, pdf_end_link_node);@/ +@!@:pdf\_end\_link\_}{\.{\\pdfendlink} primitive@> +primitive("pdfoutline", extension, pdf_outline_code);@/ +@!@:pdf\_outline\_}{\.{\\pdfoutline} primitive@> +primitive("pdfdest", extension, pdf_dest_node);@/ +@!@:pdf\_dest\_}{\.{\\pdfdest} primitive@> +primitive("pdfthread", extension, pdf_thread_node);@/ +@!@:pdf\_thread\_}{\.{\\pdfthread} primitive@> +primitive("pdfstartthread", extension, pdf_start_thread_node);@/ +@!@:pdf\_start\_thread\_}{\.{\\pdfstartthread} primitive@> +primitive("pdfendthread", extension, pdf_end_thread_node);@/ +@!@:pdf\_end\_thread\_}{\.{\\pdfendthread} primitive@> + +primitive("pdfinfo", extension, pdf_info_code);@/ +@!@:pdf\_info\_}{\.{\\pdfinfo} primitive@> +primitive("pdfcatalog", extension, pdf_catalog_code);@/ +@!@:pdf\_catalog\_}{\.{\\pdfcatalog} primitive@> +primitive("pdfnames", extension, pdf_names_code);@/ +@!@:pdf\_names\_}{\.{\\pdfnames} primitive@> + +primitive("pdffontattr", extension, pdf_font_attr_code);@/ +@!@:pdf\_font\_attr\_}{\.{\\pdffontattr} primitive@> +primitive("pdfincludechars", extension, pdf_include_chars_code);@/ +@!@:pdf\_include\_chars\_}{\.{\\pdfincludechars} primitive@> +primitive("pdfmapfile", extension, pdf_map_file_code);@/ +@!@:pdf\_map\_file\_}{\.{\\pdfmapfile} primitive@> +primitive("pdfmapline", extension, pdf_map_line_code);@/ +@!@:pdf\_map\_line\_}{\.{\\pdfmapline} primitive@> +primitive("pdftrailer", extension, pdf_trailer_code);@/ +@!@:pdf\_trailer\_}{\.{\\pdftrailer} primitive@> +primitive("pdftrailerid", extension, pdf_trailer_id_code);@/ +@!@:pdf\_trailer\_id\_}{\.{\\pdftrailerid} primitive@> + +primitive("pdffontexpand", extension, pdf_font_expand_code);@/ +@!@:pdf\_font\_expand\_}{\.{\\pdffontexpand} primitive@> + +primitive("pdfsnaprefpoint", extension, pdf_snap_ref_point_node);@/ +@!@:pdf\_snap\_ref\_point\_}{\.{\\pdfsnaprefpoint} primitive@> +primitive("pdfsnapy", extension, pdf_snapy_node);@/ +@!@:pdf\_snapy\_}{\.{\\pdfsnapy} primitive@> +primitive("pdfsnapycomp", extension, pdf_snapy_comp_node);@/ +@!@:pdf\_snapy\_comp\_}{\.{\\pdfsnapycomp} primitive@> +primitive("pdfglyphtounicode", extension, pdf_glyph_to_unicode_code);@/ +@!@:pdf\_glyph\_to\_unicode\_}{\.{\\pdfglyphtounicode} primitive@> +primitive("pdfcolorstack", extension, pdf_colorstack_node);@/ +@!@:pdf\_colorstack\_}{\.{\\pdfcolorstack} primitive@> +primitive("pdfsetmatrix", extension, pdf_setmatrix_node);@/ +@!@:pdf\_setmatrix\_}{\.{\\pdfsetmatrix} primitive@> +primitive("pdfsave", extension, pdf_save_node);@/ +@!@:pdf\_save\_}{\.{\\pdfsave} primitive@> +primitive("pdfrestore", extension, pdf_restore_node);@/ +@!@:pdf\_restore\_}{\.{\\pdfrestore} primitive@> +primitive("pdfnobuiltintounicode", extension, pdf_nobuiltin_tounicode_code);@/ +@!@:pdf\_nobuiltin\_tounicode\_}{\.{\\pdfnobuiltintounicode} primitive@> +primitive("pdfinterwordspaceon", extension, pdf_interword_space_on_node);@/ +@!@:pdf\_interword\_space\_on\_}{\.{\\pdfinterwordspaceon} primitive@> +primitive("pdfinterwordspaceoff", extension, pdf_interword_space_off_node);@/ +@!@:pdf\_interword\_space\_off\_}{\.{\\pdfinterwordspaceoff} primitive@> +primitive("pdffakespace", extension, pdf_fake_space_node);@/ +@!@:pdf\_fake\_space\_}{\.{\\pdffakespace} primitive@> +primitive("pdfrunninglinkoff", extension, pdf_running_link_off_node);@/ +@!@:pdf\_running\_link\_off\_}{\.{\\pdfrunninglinkoff} primitive@> +primitive("pdfrunninglinkon", extension, pdf_running_link_on_node);@/ +@!@:pdf\_running\_link\_on\_}{\.{\\pdfrunninglinkon} primitive@> +primitive("pdfspacefont", extension, pdf_space_font_code);@/ +@!@:pdf\_space\_font\_}{\.{\\pdfspacefont} primitive@> +@# +primitive("tracingstacklevels", extension, tracing_stack_level_code);@/ +@!@:tracingstacklevels\_}{\.{\\tracingstacklevels} primitive@> +primitive("partokencontext", extension, pdf_par_token_context_code);@/ +@!@:\partokencontext}{\.{\\partokencontext} primitive@> +primitive("partokenname", extension, pdf_par_token_name_code);@/ +@!@:partokenname\_}{\.{\\partokenname} primitive@> +primitive("showstream", extension, pdf_show_stream_code);@/ +@!@:showstream\_}{\.{\\showstream} primitive@> +} + +@ After having defined the primitives, we arange for printing them. + +@<Cases of |extension| for |print_cmd_chr|@>= + case pdf_annot_node: print_esc("pdfannot");@+break; + case pdf_catalog_code: print_esc("pdfcatalog");@+break; + case pdf_dest_node: print_esc("pdfdest");@+break; + case pdf_end_link_node: print_esc("pdfendlink");@+break; + case pdf_end_thread_node: print_esc("pdfendthread");@+break; + case pdf_font_attr_code: print_esc("pdffontattr");@+break; + case pdf_font_expand_code: print_esc("pdffontexpand");@+break; + case pdf_include_chars_code: print_esc("pdfincludechars");@+break; + case pdf_info_code: print_esc("pdfinfo");@+break; + case pdf_literal_node: print_esc("pdfliteral");@+break; + case pdf_colorstack_node: print_esc("pdfcolorstack");@+break; + case pdf_setmatrix_node: print_esc("pdfsetmatrix");@+break; + case pdf_save_node: print_esc("pdfsave");@+break; + case pdf_restore_node: print_esc("pdfrestore");@+break; + case pdf_map_file_code: print_esc("pdfmapfile");@+break; + case pdf_map_line_code: print_esc("pdfmapline");@+break; + case pdf_names_code: print_esc("pdfnames");@+break; + case pdf_obj_code: print_esc("pdfobj");@+break; + case pdf_outline_code: print_esc("pdfoutline");@+break; + case pdf_refobj_node: print_esc("pdfrefobj");@+break; + case pdf_refxform_node: print_esc("pdfrefxform");@+break; + case pdf_refximage_node: print_esc("pdfrefximage");@+break; + case pdf_snap_ref_point_node: print_esc("pdfsnaprefpoint");@+break; + case pdf_snapy_comp_node: print_esc("pdfsnapycomp");@+break; + case pdf_snapy_node: print_esc("pdfsnapy");@+break; + case pdf_start_link_node: print_esc("pdfstartlink");@+break; + case pdf_start_thread_node: print_esc("pdfstartthread");@+break; + case pdf_thread_node: print_esc("pdfthread");@+break; + case pdf_trailer_code: print_esc("pdftrailer");@+break; + case pdf_trailer_id_code: print_esc("pdftrailerid");@+break; + case pdf_xform_code: print_esc("pdfxform");@+break; + case pdf_ximage_code: print_esc("pdfximage");@+break; + case pdf_nobuiltin_tounicode_code: print_esc("pdfnobuiltintounicode");@+break; + case pdf_glyph_to_unicode_code: print_esc("pdfglyphtounicode");@+break; + case pdf_interword_space_on_node: print_esc("pdfinterwordspaceon");@+break; + case pdf_interword_space_off_node: print_esc("pdfinterwordspaceoff");@+break; + case pdf_fake_space_node: print_esc("pdffakespace");@+break; + case pdf_running_link_off_node: print_esc("pdfrunninglinkoff");@+break; + case pdf_running_link_on_node: print_esc("pdfrunninglinkon");@+break; + case pdf_space_font_code: print_esc("pdfspacefont");@+break; + case tracing_stack_level_code: print_esc("tracingstacklevels");@+break; + case pdf_par_token_context_code: print_esc("partokencontext");@+break; + case pdf_par_token_name_code: print_esc("partokenname");@+break; + case pdf_show_stream_code: print_esc("showstream");@+break; + + +@ And last not least we have to implement the primitives. + +@<Cases for |do_extension|@>= + case pdf_annot_node: @<Implement \.{\\pdfannot}@>@;@+break; + case pdf_catalog_code: @<Implement \.{\\pdfcatalog}@>@;@+break; + case pdf_dest_node: @<Implement \.{\\pdfdest}@>@;@+break; + case pdf_end_link_node: @+break; + case pdf_end_thread_node: @+break; + case pdf_font_attr_code: @<Implement \.{\\pdffontattr}@>@;@+break; + case pdf_font_expand_code: read_expand_font();@+break; + case pdf_include_chars_code: pdf_include_chars();@+break; + case pdf_info_code: scan_pdf_ext_toks();@+break; + case pdf_literal_node: @<Implement \.{\\pdfliteral}@>@;@+break; + case pdf_colorstack_node: @<Implement \.{\\pdfcolorstack}@>@;@+break; + case pdf_setmatrix_node: scan_pdf_ext_toks();@+break; + case pdf_save_node: @+break; + case pdf_restore_node: @+break; + case pdf_map_file_code: scan_pdf_ext_toks();@+break; + case pdf_map_line_code: scan_pdf_ext_toks();@+break; + case pdf_names_code: scan_pdf_ext_toks();@+break; + case pdf_obj_code: @<Implement \.{\\pdfobj}@>@;@+break; + case pdf_outline_code: @<Implement \.{\\pdfoutline}@>@;@+break; + case pdf_refobj_node: scan_int();@+break; + case pdf_refxform_node: scan_int();@+break; + case pdf_refximage_node: scan_int();@+break; + case pdf_snap_ref_point_node: @+break; + case pdf_snapy_comp_node: scan_int();@+break; + case pdf_snapy_node: @+break; + case pdf_start_link_node: scan_annot(); scan_action();@+break; + case pdf_start_thread_node: scan_annot(); scan_thread_id();@+break; + case pdf_thread_node: scan_annot(); scan_thread_id();@+break; + case pdf_trailer_code: scan_pdf_ext_toks();@+break; + case pdf_trailer_id_code: scan_pdf_ext_toks();@+break; + case pdf_xform_code: @<Implement \.{\\pdfxform}@>@;@+break; + case pdf_ximage_code: scan_image(); @+break; + case pdf_glyph_to_unicode_code: scan_pdf_ext_toks();scan_pdf_ext_toks();@+break; + case pdf_nobuiltin_tounicode_code: scan_font_ident();@+break; + case pdf_interword_space_on_node: @+break; + case pdf_interword_space_off_node: @+break; + case pdf_fake_space_node: @+break; + case pdf_running_link_off_node: @+break; + case pdf_running_link_on_node: @+break; + case pdf_space_font_code: scan_pdf_ext_toks(); @+break; + case tracing_stack_level_code: scan_int();@+break; + case pdf_par_token_context_code: scan_optional_equals();scan_int();@+break; + case pdf_par_token_name_code: scan_optional_equals();get_token();@+break; + case pdf_show_stream_code: scan_optional_equals();scan_int();@+break; + + +@ @<Implement \.{\\pdfannot}@>= +{@+ if (scan_keyword("reserveobjnum")) {@+@<Scan an optional space@>;} + else{@+ + if (scan_keyword("useobjnum")) {@+scan_int();} + scan_annot(); + scan_pdf_ext_toks(); + } +} + +@ @<Implement \.{\\pdfcatalog}@>= +{@+ scan_pdf_ext_toks(); + if (scan_keyword("openaction")) scan_action(); +} + +@ The |scan_action| routine is used not only here +but also for links and outlines. + + +@d pdf_action_page 0 /*GoTo action*/ +@d pdf_action_goto 1 /*GoTo action*/ +@d pdf_action_thread 2 /*Thread action*/ +@d pdf_action_user 3 /*user-defined action*/ + +@<Declare procedures needed in |do_ext...@>= +static void scan_action(void) /*read an action specification*/ +{@+int pdf_action; + int pdf_action_file=0; + int pdf_action_new_window=0; + if (scan_keyword("user")) + pdf_action=pdf_action_user; + else if (scan_keyword("goto")) + pdf_action=pdf_action_goto; + else if (scan_keyword("thread")) + pdf_action=pdf_action_thread; + else + pdf_error("ext1","action type missing"); + if (pdf_action==pdf_action_user) {@+ + scan_pdf_ext_toks(); + return; } + if (scan_keyword("file")) {@+ + scan_pdf_ext_toks(); + pdf_action_file=1; + } + if (scan_keyword("struct")) {@+ + if (pdf_action!=pdf_action_goto) + pdf_error("ext1","only GoTo action can be used with `struct'"); + if (pdf_action_file!=0) {@+ + scan_pdf_ext_toks(); + } + else if (scan_keyword("name")) {@+ + scan_pdf_ext_toks(); + } + else if (scan_keyword("num")) {@+ + scan_int(); + if (cur_val <= 0) + pdf_error("ext1","num identifier must be positive"); + } + else + pdf_error("ext1","identifier type missing"); + } + if (scan_keyword("page")) {@+ + if (pdf_action!=pdf_action_goto) + pdf_error("ext1","only GoTo action can be used with `page'"); + pdf_action=pdf_action_page; + scan_int(); + if (cur_val <= 0) + pdf_error("ext1","page number must be positive"); + scan_pdf_ext_toks(); + } + else if (scan_keyword("name")) {@+ + scan_pdf_ext_toks(); + } + else if (scan_keyword("num")) {@+ + if ((pdf_action==pdf_action_goto)&& + (pdf_action_file!=0)) + pdf_error("ext1", + "`goto' option cannot be used with both `file' and `num'"); + scan_int(); + if (cur_val <= 0) + pdf_error("ext1","num identifier must be positive"); + } + else + pdf_error("ext1","identifier type missing"); + if (scan_keyword("newwindow")) {@+ + pdf_action_new_window=1; + @<Scan an optional space@>;} + else if (scan_keyword("nonewwindow")) {@+ + pdf_action_new_window=2; + @<Scan an optional space@>;} + else + pdf_action_new_window=0; + if ((pdf_action_new_window > 0)&& + (((pdf_action!=pdf_action_goto)&& + (pdf_action!=pdf_action_page))|| + (pdf_action_file==0))) + pdf_error("ext1", + "`newwindow'/`nonewwindow' must be used with `goto' and `file' option"); +} + +@ Next we scan a destination. + +@d pdf_dest_xyz 0 +@d pdf_dest_fit 1 +@d pdf_dest_fith 2 +@d pdf_dest_fitv 3 +@d pdf_dest_fitb 4 +@d pdf_dest_fitbh 5 +@d pdf_dest_fitbv 6 +@d pdf_dest_fitr 7 + +@<Implement \.{\\pdfdest}@>= +{@+ int pdf_dest_type; + if (scan_keyword("struct")) {@+ + scan_int(); + if (cur_val <= 0) + pdf_error("ext1","struct identifier must be positive"); + } + if (scan_keyword("num")) {@+ + scan_int(); + if (cur_val <= 0) + pdf_error("ext1","num identifier must be positive"); + if (cur_val > max_halfword) + pdf_error("ext1","number too big"); + } + else if (scan_keyword("name")) {@+ + scan_pdf_ext_toks(); + } + else + pdf_error("ext1","identifier type missing"); + if (scan_keyword("xyz")) {@+ + pdf_dest_type=pdf_dest_xyz; + if (scan_keyword("zoom")) {@+ + scan_int(); + if (cur_val > max_halfword) + pdf_error("ext1","number too big"); + } + } + else if (scan_keyword("fitbh")) + pdf_dest_type=pdf_dest_fitbh; + else if (scan_keyword("fitbv")) + pdf_dest_type=pdf_dest_fitbv; + else if (scan_keyword("fitb")) + pdf_dest_type=pdf_dest_fitb; + else if (scan_keyword("fith")) + pdf_dest_type=pdf_dest_fith; + else if (scan_keyword("fitv")) + pdf_dest_type=pdf_dest_fitv; + else if (scan_keyword("fitr")) + pdf_dest_type=pdf_dest_fitr; + else if (scan_keyword("fit")) + pdf_dest_type=pdf_dest_fit; + else + pdf_error("ext1","destination type missing"); + @<Scan an optional space@>; + if (pdf_dest_type==pdf_dest_fitr) {@+ + scan_alt_rule(); /*scans | < rule spec > | to |alt_rule|*/ + } +} + + + +@ @<Declare procedures needed in |do_ext...@>= +static void scan_alt_rule(void) /*scans rule spec to |alt_rule|*/ +{@+ +reswitch: + if (scan_keyword("width")) {@+ + scan_normal_dimen; + goto reswitch; + } + if (scan_keyword("height")) {@+ + scan_normal_dimen; + goto reswitch; + } + if (scan_keyword("depth")) {@+ + scan_normal_dimen; + goto reswitch; + } +} + +static void scan_annot(void) /*scan an annotation*/ +{@+ + scan_alt_rule(); /*scans | < rule spec > |*/ + if (scan_keyword("attr")) + scan_pdf_ext_toks(); +} + + + +@ @<Implement \.{\\pdffontattr}@>= +{@+ + scan_font_ident(); + if (cur_val==null_font) + pdf_error("font","invalid font identifier"); + scan_pdf_ext_toks(); +} + +@ To implement \.{\\pdffontexpand} we need the following routine: + +@<Declare procedures needed in |do_ext...@>= +static void read_expand_font(void) /*read font expansion spec*/ +{@+int shrink_limit, stretch_limit, font_step; + internal_font_number f; + + /*read font expansion parameters*/ + scan_font_ident(); + f=cur_val; + if (f==null_font) + pdf_error("font expansion","invalid font identifier"); + scan_optional_equals(); + scan_int(); + scan_int(); + scan_int(); + if (scan_keyword("autoexpand")) {@+ + @<Scan an optional space@>; + } +} + +@ Do implement \.{\\pdfincludechars} we need the next function. +@<Declare procedures needed in |do_ext...@>= +static void pdf_include_chars(void) +{@+str_number s; + pool_pointer k; /*running indices*/ + internal_font_number f; + + scan_font_ident(); + f=cur_val; + if (f==null_font) + pdf_error("font","invalid font identifier"); + scan_pdf_ext_toks(); +} + +@ @<Implement \.{\\pdfliteral}@>= +{@+ int k; + if (scan_keyword("shipout")) k=pdf_lateliteral_node; + else k=pdf_literal_node; + if (scan_keyword("direct")) do_nothing; + else if (scan_keyword("page")) do_nothing; + else do_nothing; + if (k==pdf_literal_node) scan_pdf_ext_toks(); + else scan_pdf_ext_late_toks(); +} + +@ + +@d colorstack_set 0 +@d colorstack_push 1 +@d colorstack_data 1 /* last value where data field is set */ +@d colorstack_pop 2 +@d colorstack_current 3 + +@<Implement \.{\\pdfcolorstack}@>= +{@+int i; + scan_int(); + if (scan_keyword("set")) {@+ + i=colorstack_set; + } + else if (scan_keyword("push")) {@+ + i=colorstack_push; + } + else if (scan_keyword("pop")) {@+ + i=colorstack_pop; + } + else if (scan_keyword("current")) {@+ + i=colorstack_current; + } + else{@+ + i=-1; /*error*/ + } + if (i >= 0) {@+ + if (i <= colorstack_data) {@+ + scan_pdf_ext_toks(); + } + } +} + +@ @<Implement \.{\\pdfobj}@>= +{@+ + if (scan_keyword("reserveobjnum")) {@+ + @<Scan an optional space@>; + } + else{@+ + if (scan_keyword("useobjnum")) scan_int(); + if (scan_keyword("stream")) {@+ + if (scan_keyword("attr")) scan_pdf_ext_toks(); + } + if (scan_keyword("file")) do_nothing; + scan_pdf_ext_toks(); + } +} + +@ @<Implement \.{\\pdfoutline}@>= +{@+ + if (scan_keyword("attr")) scan_pdf_ext_toks(); + scan_action(); + if (scan_keyword("count")) scan_int(); + scan_pdf_ext_toks(); +} + +@ @<Implement \.{\\pdfxform}@>= +{@+ + if (scan_keyword("attr")) scan_pdf_ext_toks(); + if (scan_keyword("resources")) scan_pdf_ext_toks(); + scan_register_num(); +} + +@ The next procedure is neede for \.{\\pdfthread} and \.{\\pdfstartthread} + +@<Declare procedures needed in |do_ext...@>= +static void scan_thread_id(void) +{@+if (scan_keyword("num")) scan_int(); + else if (scan_keyword("name")) scan_pdf_ext_toks(); +} + +@ The next functions are used to implement \.{\\pdfximage}. +@<Declare procedures needed in |do_ext...@>= +static void scan_pdf_box_spec(void) /*scans PDF pagebox specification*/ +{@+ + if (scan_keyword("mediabox")) return; + else if (scan_keyword("cropbox")) return; + else if (scan_keyword("bleedbox")) return; + else if (scan_keyword("trimbox")) return; + else if (scan_keyword("artbox")) return; +} + +static void scan_image(void) +{@+ scan_alt_rule(); + if (scan_keyword("attr")) scan_pdf_ext_toks(); + if (scan_keyword("named")) scan_pdf_ext_toks(); + else if (scan_keyword("page")) scan_int(); + if (scan_keyword("colorspace")) scan_int(); + scan_pdf_box_spec(); + scan_pdf_ext_toks(); +} + + +@ The current version of the {\tt -pdf} version does not implementa all \pdfTeX\ primitives. + For example, the primitves \.{\\pdfcopyfont} and \.{\\letterspacefont} are not defined but + dummy versions could be implemented with |scan_font_ident| and |scan_int|. + + +@* Index. +Here is where you can find all uses of each identifier in the program, +with underlined entries pointing to where the identifier was defined. +If the identifier is only one letter long, however, you get to see only +the underlined entries. {\sl All references are to section numbers instead of +page numbers.} + +This index also lists error messages and other aspects of the program +that you might want to look up some day. For example, the entry +for ``system dependencies'' lists all sections that should receive +special attention from people who are installing \TeX\ in a new +operating environment. A list of various things that can't happen appears +under ``this can't happen''. Approximately 40 sections are listed under +``inner loop''; these account for about 60\pct! of \TeX's running time, +exclusive of input and output. |