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diff --git a/Master/tlpkg/tlperl/lib/pods/perlembed.pod b/Master/tlpkg/tlperl/lib/pods/perlembed.pod deleted file mode 100644 index e40035eb71a..00000000000 --- a/Master/tlpkg/tlperl/lib/pods/perlembed.pod +++ /dev/null @@ -1,1117 +0,0 @@ -=head1 NAME - -perlembed - how to embed perl in your C program - -=head1 DESCRIPTION - -=head2 PREAMBLE - -Do you want to: - -=over 5 - -=item B<Use C from Perl?> - -Read L<perlxstut>, L<perlxs>, L<h2xs>, L<perlguts>, and L<perlapi>. - -=item B<Use a Unix program from Perl?> - -Read about back-quotes and about C<system> and C<exec> in L<perlfunc>. - -=item B<Use Perl from Perl?> - -Read about L<perlfunc/do> and L<perlfunc/eval> and L<perlfunc/require> -and L<perlfunc/use>. - -=item B<Use C from C?> - -Rethink your design. - -=item B<Use Perl from C?> - -Read on... - -=back - -=head2 ROADMAP - -=over 5 - -=item * - -Compiling your C program - -=item * - -Adding a Perl interpreter to your C program - -=item * - -Calling a Perl subroutine from your C program - -=item * - -Evaluating a Perl statement from your C program - -=item * - -Performing Perl pattern matches and substitutions from your C program - -=item * - -Fiddling with the Perl stack from your C program - -=item * - -Maintaining a persistent interpreter - -=item * - -Maintaining multiple interpreter instances - -=item * - -Using Perl modules, which themselves use C libraries, from your C program - -=item * - -Embedding Perl under Win32 - -=back - -=head2 Compiling your C program - -If you have trouble compiling the scripts in this documentation, -you're not alone. The cardinal rule: COMPILE THE PROGRAMS IN EXACTLY -THE SAME WAY THAT YOUR PERL WAS COMPILED. (Sorry for yelling.) - -Also, every C program that uses Perl must link in the I<perl library>. -What's that, you ask? Perl is itself written in C; the perl library -is the collection of compiled C programs that were used to create your -perl executable (I</usr/bin/perl> or equivalent). (Corollary: you -can't use Perl from your C program unless Perl has been compiled on -your machine, or installed properly--that's why you shouldn't blithely -copy Perl executables from machine to machine without also copying the -I<lib> directory.) - -When you use Perl from C, your C program will--usually--allocate, -"run", and deallocate a I<PerlInterpreter> object, which is defined by -the perl library. - -If your copy of Perl is recent enough to contain this documentation -(version 5.002 or later), then the perl library (and I<EXTERN.h> and -I<perl.h>, which you'll also need) will reside in a directory -that looks like this: - - /usr/local/lib/perl5/your_architecture_here/CORE - -or perhaps just - - /usr/local/lib/perl5/CORE - -or maybe something like - - /usr/opt/perl5/CORE - -Execute this statement for a hint about where to find CORE: - - perl -MConfig -e 'print $Config{archlib}' - -Here's how you'd compile the example in the next section, -L<Adding a Perl interpreter to your C program>, on my Linux box: - - % gcc -O2 -Dbool=char -DHAS_BOOL -I/usr/local/include - -I/usr/local/lib/perl5/i586-linux/5.003/CORE - -L/usr/local/lib/perl5/i586-linux/5.003/CORE - -o interp interp.c -lperl -lm - -(That's all one line.) On my DEC Alpha running old 5.003_05, the -incantation is a bit different: - - % cc -O2 -Olimit 2900 -DSTANDARD_C -I/usr/local/include - -I/usr/local/lib/perl5/alpha-dec_osf/5.00305/CORE - -L/usr/local/lib/perl5/alpha-dec_osf/5.00305/CORE -L/usr/local/lib - -D__LANGUAGE_C__ -D_NO_PROTO -o interp interp.c -lperl -lm - -How can you figure out what to add? Assuming your Perl is post-5.001, -execute a C<perl -V> command and pay special attention to the "cc" and -"ccflags" information. - -You'll have to choose the appropriate compiler (I<cc>, I<gcc>, et al.) for -your machine: C<perl -MConfig -e 'print $Config{cc}'> will tell you what -to use. - -You'll also have to choose the appropriate library directory -(I</usr/local/lib/...>) for your machine. If your compiler complains -that certain functions are undefined, or that it can't locate -I<-lperl>, then you need to change the path following the C<-L>. If it -complains that it can't find I<EXTERN.h> and I<perl.h>, you need to -change the path following the C<-I>. - -You may have to add extra libraries as well. Which ones? -Perhaps those printed by - - perl -MConfig -e 'print $Config{libs}' - -Provided your perl binary was properly configured and installed the -B<ExtUtils::Embed> module will determine all of this information for -you: - - % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` - -If the B<ExtUtils::Embed> module isn't part of your Perl distribution, -you can retrieve it from -http://www.perl.com/perl/CPAN/modules/by-module/ExtUtils/ -(If this documentation came from your Perl distribution, then you're -running 5.004 or better and you already have it.) - -The B<ExtUtils::Embed> kit on CPAN also contains all source code for -the examples in this document, tests, additional examples and other -information you may find useful. - -=head2 Adding a Perl interpreter to your C program - -In a sense, perl (the C program) is a good example of embedding Perl -(the language), so I'll demonstrate embedding with I<miniperlmain.c>, -included in the source distribution. Here's a bastardized, non-portable -version of I<miniperlmain.c> containing the essentials of embedding: - - #include <EXTERN.h> /* from the Perl distribution */ - #include <perl.h> /* from the Perl distribution */ - - static PerlInterpreter *my_perl; /*** The Perl interpreter ***/ - - int main(int argc, char **argv, char **env) - { - PERL_SYS_INIT3(&argc,&argv,&env); - my_perl = perl_alloc(); - perl_construct(my_perl); - PL_exit_flags |= PERL_EXIT_DESTRUCT_END; - perl_parse(my_perl, NULL, argc, argv, (char **)NULL); - perl_run(my_perl); - perl_destruct(my_perl); - perl_free(my_perl); - PERL_SYS_TERM(); - } - -Notice that we don't use the C<env> pointer. Normally handed to -C<perl_parse> as its final argument, C<env> here is replaced by -C<NULL>, which means that the current environment will be used. - -The macros PERL_SYS_INIT3() and PERL_SYS_TERM() provide system-specific -tune up of the C runtime environment necessary to run Perl interpreters; -they should only be called once regardless of how many interpreters you -create or destroy. Call PERL_SYS_INIT3() before you create your first -interpreter, and PERL_SYS_TERM() after you free your last interpreter. - -Since PERL_SYS_INIT3() may change C<env>, it may be more appropriate to -provide C<env> as an argument to perl_parse(). - -Also notice that no matter what arguments you pass to perl_parse(), -PERL_SYS_INIT3() must be invoked on the C main() argc, argv and env and -only once. - -Now compile this program (I'll call it I<interp.c>) into an executable: - - % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` - -After a successful compilation, you'll be able to use I<interp> just -like perl itself: - - % interp - print "Pretty Good Perl \n"; - print "10890 - 9801 is ", 10890 - 9801; - <CTRL-D> - Pretty Good Perl - 10890 - 9801 is 1089 - -or - - % interp -e 'printf("%x", 3735928559)' - deadbeef - -You can also read and execute Perl statements from a file while in the -midst of your C program, by placing the filename in I<argv[1]> before -calling I<perl_run>. - -=head2 Calling a Perl subroutine from your C program - -To call individual Perl subroutines, you can use any of the B<call_*> -functions documented in L<perlcall>. -In this example we'll use C<call_argv>. - -That's shown below, in a program I'll call I<showtime.c>. - - #include <EXTERN.h> - #include <perl.h> - - static PerlInterpreter *my_perl; - - int main(int argc, char **argv, char **env) - { - char *args[] = { NULL }; - PERL_SYS_INIT3(&argc,&argv,&env); - my_perl = perl_alloc(); - perl_construct(my_perl); - - perl_parse(my_perl, NULL, argc, argv, NULL); - PL_exit_flags |= PERL_EXIT_DESTRUCT_END; - - /*** skipping perl_run() ***/ - - call_argv("showtime", G_DISCARD | G_NOARGS, args); - - perl_destruct(my_perl); - perl_free(my_perl); - PERL_SYS_TERM(); - } - -where I<showtime> is a Perl subroutine that takes no arguments (that's the -I<G_NOARGS>) and for which I'll ignore the return value (that's the -I<G_DISCARD>). Those flags, and others, are discussed in L<perlcall>. - -I'll define the I<showtime> subroutine in a file called I<showtime.pl>: - - print "I shan't be printed."; - - sub showtime { - print time; - } - -Simple enough. Now compile and run: - - % cc -o showtime showtime.c `perl -MExtUtils::Embed -e ccopts -e ldopts` - - % showtime showtime.pl - 818284590 - -yielding the number of seconds that elapsed between January 1, 1970 -(the beginning of the Unix epoch), and the moment I began writing this -sentence. - -In this particular case we don't have to call I<perl_run>, as we set -the PL_exit_flag PERL_EXIT_DESTRUCT_END which executes END blocks in -perl_destruct. - -If you want to pass arguments to the Perl subroutine, you can add -strings to the C<NULL>-terminated C<args> list passed to -I<call_argv>. For other data types, or to examine return values, -you'll need to manipulate the Perl stack. That's demonstrated in -L<Fiddling with the Perl stack from your C program>. - -=head2 Evaluating a Perl statement from your C program - -Perl provides two API functions to evaluate pieces of Perl code. -These are L<perlapi/eval_sv> and L<perlapi/eval_pv>. - -Arguably, these are the only routines you'll ever need to execute -snippets of Perl code from within your C program. Your code can be as -long as you wish; it can contain multiple statements; it can employ -L<perlfunc/use>, L<perlfunc/require>, and L<perlfunc/do> to -include external Perl files. - -I<eval_pv> lets us evaluate individual Perl strings, and then -extract variables for coercion into C types. The following program, -I<string.c>, executes three Perl strings, extracting an C<int> from -the first, a C<float> from the second, and a C<char *> from the third. - - #include <EXTERN.h> - #include <perl.h> - - static PerlInterpreter *my_perl; - - main (int argc, char **argv, char **env) - { - char *embedding[] = { "", "-e", "0" }; - - PERL_SYS_INIT3(&argc,&argv,&env); - my_perl = perl_alloc(); - perl_construct( my_perl ); - - perl_parse(my_perl, NULL, 3, embedding, NULL); - PL_exit_flags |= PERL_EXIT_DESTRUCT_END; - perl_run(my_perl); - - /** Treat $a as an integer **/ - eval_pv("$a = 3; $a **= 2", TRUE); - printf("a = %d\n", SvIV(get_sv("a", 0))); - - /** Treat $a as a float **/ - eval_pv("$a = 3.14; $a **= 2", TRUE); - printf("a = %f\n", SvNV(get_sv("a", 0))); - - /** Treat $a as a string **/ - eval_pv("$a = 'rekcaH lreP rehtonA tsuJ'; $a = reverse($a);", TRUE); - printf("a = %s\n", SvPV_nolen(get_sv("a", 0))); - - perl_destruct(my_perl); - perl_free(my_perl); - PERL_SYS_TERM(); - } - -All of those strange functions with I<sv> in their names help convert Perl scalars to C types. They're described in L<perlguts> and L<perlapi>. - -If you compile and run I<string.c>, you'll see the results of using -I<SvIV()> to create an C<int>, I<SvNV()> to create a C<float>, and -I<SvPV()> to create a string: - - a = 9 - a = 9.859600 - a = Just Another Perl Hacker - -In the example above, we've created a global variable to temporarily -store the computed value of our eval'ed expression. It is also -possible and in most cases a better strategy to fetch the return value -from I<eval_pv()> instead. Example: - - ... - SV *val = eval_pv("reverse 'rekcaH lreP rehtonA tsuJ'", TRUE); - printf("%s\n", SvPV_nolen(val)); - ... - -This way, we avoid namespace pollution by not creating global -variables and we've simplified our code as well. - -=head2 Performing Perl pattern matches and substitutions from your C program - -The I<eval_sv()> function lets us evaluate strings of Perl code, so we can -define some functions that use it to "specialize" in matches and -substitutions: I<match()>, I<substitute()>, and I<matches()>. - - I32 match(SV *string, char *pattern); - -Given a string and a pattern (e.g., C<m/clasp/> or C</\b\w*\b/>, which -in your C program might appear as "/\\b\\w*\\b/"), match() -returns 1 if the string matches the pattern and 0 otherwise. - - int substitute(SV **string, char *pattern); - -Given a pointer to an C<SV> and an C<=~> operation (e.g., -C<s/bob/robert/g> or C<tr[A-Z][a-z]>), substitute() modifies the string -within the C<SV> as according to the operation, returning the number of substitutions -made. - - int matches(SV *string, char *pattern, AV **matches); - -Given an C<SV>, a pattern, and a pointer to an empty C<AV>, -matches() evaluates C<$string =~ $pattern> in a list context, and -fills in I<matches> with the array elements, returning the number of matches found. - -Here's a sample program, I<match.c>, that uses all three (long lines have -been wrapped here): - - #include <EXTERN.h> - #include <perl.h> - - static PerlInterpreter *my_perl; - - /** my_eval_sv(code, error_check) - ** kinda like eval_sv(), - ** but we pop the return value off the stack - **/ - SV* my_eval_sv(SV *sv, I32 croak_on_error) - { - dSP; - SV* retval; - - - PUSHMARK(SP); - eval_sv(sv, G_SCALAR); - - SPAGAIN; - retval = POPs; - PUTBACK; - - if (croak_on_error && SvTRUE(ERRSV)) - croak(SvPVx_nolen(ERRSV)); - - return retval; - } - - /** match(string, pattern) - ** - ** Used for matches in a scalar context. - ** - ** Returns 1 if the match was successful; 0 otherwise. - **/ - - I32 match(SV *string, char *pattern) - { - SV *command = newSV(0), *retval; - - sv_setpvf(command, "my $string = '%s'; $string =~ %s", - SvPV_nolen(string), pattern); - - retval = my_eval_sv(command, TRUE); - SvREFCNT_dec(command); - - return SvIV(retval); - } - - /** substitute(string, pattern) - ** - ** Used for =~ operations that modify their left-hand side (s/// and tr///) - ** - ** Returns the number of successful matches, and - ** modifies the input string if there were any. - **/ - - I32 substitute(SV **string, char *pattern) - { - SV *command = newSV(0), *retval; - - sv_setpvf(command, "$string = '%s'; ($string =~ %s)", - SvPV_nolen(*string), pattern); - - retval = my_eval_sv(command, TRUE); - SvREFCNT_dec(command); - - *string = get_sv("string", 0); - return SvIV(retval); - } - - /** matches(string, pattern, matches) - ** - ** Used for matches in a list context. - ** - ** Returns the number of matches, - ** and fills in **matches with the matching substrings - **/ - - I32 matches(SV *string, char *pattern, AV **match_list) - { - SV *command = newSV(0); - I32 num_matches; - - sv_setpvf(command, "my $string = '%s'; @array = ($string =~ %s)", - SvPV_nolen(string), pattern); - - my_eval_sv(command, TRUE); - SvREFCNT_dec(command); - - *match_list = get_av("array", 0); - num_matches = av_len(*match_list) + 1; - - return num_matches; - } - - main (int argc, char **argv, char **env) - { - char *embedding[] = { "", "-e", "0" }; - AV *match_list; - I32 num_matches, i; - SV *text; - - PERL_SYS_INIT3(&argc,&argv,&env); - my_perl = perl_alloc(); - perl_construct(my_perl); - perl_parse(my_perl, NULL, 3, embedding, NULL); - PL_exit_flags |= PERL_EXIT_DESTRUCT_END; - - text = newSV(0); - sv_setpv(text, "When he is at a convenience store and the " - "bill comes to some amount like 76 cents, Maynard is " - "aware that there is something he *should* do, something " - "that will enable him to get back a quarter, but he has " - "no idea *what*. He fumbles through his red squeezey " - "changepurse and gives the boy three extra pennies with " - "his dollar, hoping that he might luck into the correct " - "amount. The boy gives him back two of his own pennies " - "and then the big shiny quarter that is his prize. " - "-RICHH"); - - if (match(text, "m/quarter/")) /** Does text contain 'quarter'? **/ - printf("match: Text contains the word 'quarter'.\n\n"); - else - printf("match: Text doesn't contain the word 'quarter'.\n\n"); - - if (match(text, "m/eighth/")) /** Does text contain 'eighth'? **/ - printf("match: Text contains the word 'eighth'.\n\n"); - else - printf("match: Text doesn't contain the word 'eighth'.\n\n"); - - /** Match all occurrences of /wi../ **/ - num_matches = matches(text, "m/(wi..)/g", &match_list); - printf("matches: m/(wi..)/g found %d matches...\n", num_matches); - - for (i = 0; i < num_matches; i++) - printf("match: %s\n", SvPV_nolen(*av_fetch(match_list, i, FALSE))); - printf("\n"); - - /** Remove all vowels from text **/ - num_matches = substitute(&text, "s/[aeiou]//gi"); - if (num_matches) { - printf("substitute: s/[aeiou]//gi...%d substitutions made.\n", - num_matches); - printf("Now text is: %s\n\n", SvPV_nolen(text)); - } - - /** Attempt a substitution **/ - if (!substitute(&text, "s/Perl/C/")) { - printf("substitute: s/Perl/C...No substitution made.\n\n"); - } - - SvREFCNT_dec(text); - PL_perl_destruct_level = 1; - perl_destruct(my_perl); - perl_free(my_perl); - PERL_SYS_TERM(); - } - -which produces the output (again, long lines have been wrapped here) - - match: Text contains the word 'quarter'. - - match: Text doesn't contain the word 'eighth'. - - matches: m/(wi..)/g found 2 matches... - match: will - match: with - - substitute: s/[aeiou]//gi...139 substitutions made. - Now text is: Whn h s t cnvnnc str nd th bll cms t sm mnt lk 76 cnts, - Mynrd s wr tht thr s smthng h *shld* d, smthng tht wll nbl hm t gt bck - qrtr, bt h hs n d *wht*. H fmbls thrgh hs rd sqzy chngprs nd gvs th by - thr xtr pnns wth hs dllr, hpng tht h mght lck nt th crrct mnt. Th by gvs - hm bck tw f hs wn pnns nd thn th bg shny qrtr tht s hs prz. -RCHH - - substitute: s/Perl/C...No substitution made. - -=head2 Fiddling with the Perl stack from your C program - -When trying to explain stacks, most computer science textbooks mumble -something about spring-loaded columns of cafeteria plates: the last -thing you pushed on the stack is the first thing you pop off. That'll -do for our purposes: your C program will push some arguments onto "the Perl -stack", shut its eyes while some magic happens, and then pop the -results--the return value of your Perl subroutine--off the stack. - -First you'll need to know how to convert between C types and Perl -types, with newSViv() and sv_setnv() and newAV() and all their -friends. They're described in L<perlguts> and L<perlapi>. - -Then you'll need to know how to manipulate the Perl stack. That's -described in L<perlcall>. - -Once you've understood those, embedding Perl in C is easy. - -Because C has no builtin function for integer exponentiation, let's -make Perl's ** operator available to it (this is less useful than it -sounds, because Perl implements ** with C's I<pow()> function). First -I'll create a stub exponentiation function in I<power.pl>: - - sub expo { - my ($a, $b) = @_; - return $a ** $b; - } - -Now I'll create a C program, I<power.c>, with a function -I<PerlPower()> that contains all the perlguts necessary to push the -two arguments into I<expo()> and to pop the return value out. Take a -deep breath... - - #include <EXTERN.h> - #include <perl.h> - - static PerlInterpreter *my_perl; - - static void - PerlPower(int a, int b) - { - dSP; /* initialize stack pointer */ - ENTER; /* everything created after here */ - SAVETMPS; /* ...is a temporary variable. */ - PUSHMARK(SP); /* remember the stack pointer */ - XPUSHs(sv_2mortal(newSViv(a))); /* push the base onto the stack */ - XPUSHs(sv_2mortal(newSViv(b))); /* push the exponent onto stack */ - PUTBACK; /* make local stack pointer global */ - call_pv("expo", G_SCALAR); /* call the function */ - SPAGAIN; /* refresh stack pointer */ - /* pop the return value from stack */ - printf ("%d to the %dth power is %d.\n", a, b, POPi); - PUTBACK; - FREETMPS; /* free that return value */ - LEAVE; /* ...and the XPUSHed "mortal" args.*/ - } - - int main (int argc, char **argv, char **env) - { - char *my_argv[] = { "", "power.pl" }; - - PERL_SYS_INIT3(&argc,&argv,&env); - my_perl = perl_alloc(); - perl_construct( my_perl ); - - perl_parse(my_perl, NULL, 2, my_argv, (char **)NULL); - PL_exit_flags |= PERL_EXIT_DESTRUCT_END; - perl_run(my_perl); - - PerlPower(3, 4); /*** Compute 3 ** 4 ***/ - - perl_destruct(my_perl); - perl_free(my_perl); - PERL_SYS_TERM(); - } - - - -Compile and run: - - % cc -o power power.c `perl -MExtUtils::Embed -e ccopts -e ldopts` - - % power - 3 to the 4th power is 81. - -=head2 Maintaining a persistent interpreter - -When developing interactive and/or potentially long-running -applications, it's a good idea to maintain a persistent interpreter -rather than allocating and constructing a new interpreter multiple -times. The major reason is speed: since Perl will only be loaded into -memory once. - -However, you have to be more cautious with namespace and variable -scoping when using a persistent interpreter. In previous examples -we've been using global variables in the default package C<main>. We -knew exactly what code would be run, and assumed we could avoid -variable collisions and outrageous symbol table growth. - -Let's say your application is a server that will occasionally run Perl -code from some arbitrary file. Your server has no way of knowing what -code it's going to run. Very dangerous. - -If the file is pulled in by C<perl_parse()>, compiled into a newly -constructed interpreter, and subsequently cleaned out with -C<perl_destruct()> afterwards, you're shielded from most namespace -troubles. - -One way to avoid namespace collisions in this scenario is to translate -the filename into a guaranteed-unique package name, and then compile -the code into that package using L<perlfunc/eval>. In the example -below, each file will only be compiled once. Or, the application -might choose to clean out the symbol table associated with the file -after it's no longer needed. Using L<perlapi/call_argv>, We'll -call the subroutine C<Embed::Persistent::eval_file> which lives in the -file C<persistent.pl> and pass the filename and boolean cleanup/cache -flag as arguments. - -Note that the process will continue to grow for each file that it -uses. In addition, there might be C<AUTOLOAD>ed subroutines and other -conditions that cause Perl's symbol table to grow. You might want to -add some logic that keeps track of the process size, or restarts -itself after a certain number of requests, to ensure that memory -consumption is minimized. You'll also want to scope your variables -with L<perlfunc/my> whenever possible. - - - package Embed::Persistent; - #persistent.pl - - use strict; - our %Cache; - use Symbol qw(delete_package); - - sub valid_package_name { - my($string) = @_; - $string =~ s/([^A-Za-z0-9\/])/sprintf("_%2x",unpack("C",$1))/eg; - # second pass only for words starting with a digit - $string =~ s|/(\d)|sprintf("/_%2x",unpack("C",$1))|eg; - - # Dress it up as a real package name - $string =~ s|/|::|g; - return "Embed" . $string; - } - - sub eval_file { - my($filename, $delete) = @_; - my $package = valid_package_name($filename); - my $mtime = -M $filename; - if(defined $Cache{$package}{mtime} - && - $Cache{$package}{mtime} <= $mtime) - { - # we have compiled this subroutine already, - # it has not been updated on disk, nothing left to do - print STDERR "already compiled $package->handler\n"; - } - else { - local *FH; - open FH, $filename or die "open '$filename' $!"; - local($/) = undef; - my $sub = <FH>; - close FH; - - #wrap the code into a subroutine inside our unique package - my $eval = qq{package $package; sub handler { $sub; }}; - { - # hide our variables within this block - my($filename,$mtime,$package,$sub); - eval $eval; - } - die $@ if $@; - - #cache it unless we're cleaning out each time - $Cache{$package}{mtime} = $mtime unless $delete; - } - - eval {$package->handler;}; - die $@ if $@; - - delete_package($package) if $delete; - - #take a look if you want - #print Devel::Symdump->rnew($package)->as_string, $/; - } - - 1; - - __END__ - - /* persistent.c */ - #include <EXTERN.h> - #include <perl.h> - - /* 1 = clean out filename's symbol table after each request, 0 = don't */ - #ifndef DO_CLEAN - #define DO_CLEAN 0 - #endif - - #define BUFFER_SIZE 1024 - - static PerlInterpreter *my_perl = NULL; - - int - main(int argc, char **argv, char **env) - { - char *embedding[] = { "", "persistent.pl" }; - char *args[] = { "", DO_CLEAN, NULL }; - char filename[BUFFER_SIZE]; - int exitstatus = 0; - - PERL_SYS_INIT3(&argc,&argv,&env); - if((my_perl = perl_alloc()) == NULL) { - fprintf(stderr, "no memory!"); - exit(1); - } - perl_construct(my_perl); - - PL_origalen = 1; /* don't let $0 assignment update the proctitle or embedding[0] */ - exitstatus = perl_parse(my_perl, NULL, 2, embedding, NULL); - PL_exit_flags |= PERL_EXIT_DESTRUCT_END; - if(!exitstatus) { - exitstatus = perl_run(my_perl); - - while(printf("Enter file name: ") && - fgets(filename, BUFFER_SIZE, stdin)) { - - filename[strlen(filename)-1] = '\0'; /* strip \n */ - /* call the subroutine, passing it the filename as an argument */ - args[0] = filename; - call_argv("Embed::Persistent::eval_file", - G_DISCARD | G_EVAL, args); - - /* check $@ */ - if(SvTRUE(ERRSV)) - fprintf(stderr, "eval error: %s\n", SvPV_nolen(ERRSV)); - } - } - - PL_perl_destruct_level = 0; - perl_destruct(my_perl); - perl_free(my_perl); - PERL_SYS_TERM(); - exit(exitstatus); - } - -Now compile: - - % cc -o persistent persistent.c `perl -MExtUtils::Embed -e ccopts -e ldopts` - -Here's an example script file: - - #test.pl - my $string = "hello"; - foo($string); - - sub foo { - print "foo says: @_\n"; - } - -Now run: - - % persistent - Enter file name: test.pl - foo says: hello - Enter file name: test.pl - already compiled Embed::test_2epl->handler - foo says: hello - Enter file name: ^C - -=head2 Execution of END blocks - -Traditionally END blocks have been executed at the end of the perl_run. -This causes problems for applications that never call perl_run. Since -perl 5.7.2 you can specify C<PL_exit_flags |= PERL_EXIT_DESTRUCT_END> -to get the new behaviour. This also enables the running of END blocks if -the perl_parse fails and C<perl_destruct> will return the exit value. - -=head2 $0 assignments - -When a perl script assigns a value to $0 then the perl runtime will -try to make this value show up as the program name reported by "ps" by -updating the memory pointed to by the argv passed to perl_parse() and -also calling API functions like setproctitle() where available. This -behaviour might not be appropriate when embedding perl and can be -disabled by assigning the value C<1> to the variable C<PL_origalen> -before perl_parse() is called. - -The F<persistent.c> example above is for instance likely to segfault -when $0 is assigned to if the C<PL_origalen = 1;> assignment is -removed. This because perl will try to write to the read only memory -of the C<embedding[]> strings. - -=head2 Maintaining multiple interpreter instances - -Some rare applications will need to create more than one interpreter -during a session. Such an application might sporadically decide to -release any resources associated with the interpreter. - -The program must take care to ensure that this takes place I<before> -the next interpreter is constructed. By default, when perl is not -built with any special options, the global variable -C<PL_perl_destruct_level> is set to C<0>, since extra cleaning isn't -usually needed when a program only ever creates a single interpreter -in its entire lifetime. - -Setting C<PL_perl_destruct_level> to C<1> makes everything squeaky clean: - - while(1) { - ... - /* reset global variables here with PL_perl_destruct_level = 1 */ - PL_perl_destruct_level = 1; - perl_construct(my_perl); - ... - /* clean and reset _everything_ during perl_destruct */ - PL_perl_destruct_level = 1; - perl_destruct(my_perl); - perl_free(my_perl); - ... - /* let's go do it again! */ - } - -When I<perl_destruct()> is called, the interpreter's syntax parse tree -and symbol tables are cleaned up, and global variables are reset. The -second assignment to C<PL_perl_destruct_level> is needed because -perl_construct resets it to C<0>. - -Now suppose we have more than one interpreter instance running at the -same time. This is feasible, but only if you used the Configure option -C<-Dusemultiplicity> or the options C<-Dusethreads -Duseithreads> when -building perl. By default, enabling one of these Configure options -sets the per-interpreter global variable C<PL_perl_destruct_level> to -C<1>, so that thorough cleaning is automatic and interpreter variables -are initialized correctly. Even if you don't intend to run two or -more interpreters at the same time, but to run them sequentially, like -in the above example, it is recommended to build perl with the -C<-Dusemultiplicity> option otherwise some interpreter variables may -not be initialized correctly between consecutive runs and your -application may crash. - -See also L<perlxs/Thread-aware system interfaces>. - -Using C<-Dusethreads -Duseithreads> rather than C<-Dusemultiplicity> -is more appropriate if you intend to run multiple interpreters -concurrently in different threads, because it enables support for -linking in the thread libraries of your system with the interpreter. - -Let's give it a try: - - - #include <EXTERN.h> - #include <perl.h> - - /* we're going to embed two interpreters */ - - #define SAY_HELLO "-e", "print qq(Hi, I'm $^X\n)" - - int main(int argc, char **argv, char **env) - { - PerlInterpreter *one_perl, *two_perl; - char *one_args[] = { "one_perl", SAY_HELLO }; - char *two_args[] = { "two_perl", SAY_HELLO }; - - PERL_SYS_INIT3(&argc,&argv,&env); - one_perl = perl_alloc(); - two_perl = perl_alloc(); - - PERL_SET_CONTEXT(one_perl); - perl_construct(one_perl); - PERL_SET_CONTEXT(two_perl); - perl_construct(two_perl); - - PERL_SET_CONTEXT(one_perl); - perl_parse(one_perl, NULL, 3, one_args, (char **)NULL); - PERL_SET_CONTEXT(two_perl); - perl_parse(two_perl, NULL, 3, two_args, (char **)NULL); - - PERL_SET_CONTEXT(one_perl); - perl_run(one_perl); - PERL_SET_CONTEXT(two_perl); - perl_run(two_perl); - - PERL_SET_CONTEXT(one_perl); - perl_destruct(one_perl); - PERL_SET_CONTEXT(two_perl); - perl_destruct(two_perl); - - PERL_SET_CONTEXT(one_perl); - perl_free(one_perl); - PERL_SET_CONTEXT(two_perl); - perl_free(two_perl); - PERL_SYS_TERM(); - } - -Note the calls to PERL_SET_CONTEXT(). These are necessary to initialize -the global state that tracks which interpreter is the "current" one on -the particular process or thread that may be running it. It should -always be used if you have more than one interpreter and are making -perl API calls on both interpreters in an interleaved fashion. - -PERL_SET_CONTEXT(interp) should also be called whenever C<interp> is -used by a thread that did not create it (using either perl_alloc(), or -the more esoteric perl_clone()). - -Compile as usual: - - % cc -o multiplicity multiplicity.c `perl -MExtUtils::Embed -e ccopts -e ldopts` - -Run it, Run it: - - % multiplicity - Hi, I'm one_perl - Hi, I'm two_perl - -=head2 Using Perl modules, which themselves use C libraries, from your C program - -If you've played with the examples above and tried to embed a script -that I<use()>s a Perl module (such as I<Socket>) which itself uses a C or C++ library, -this probably happened: - - - Can't load module Socket, dynamic loading not available in this perl. - (You may need to build a new perl executable which either supports - dynamic loading or has the Socket module statically linked into it.) - - -What's wrong? - -Your interpreter doesn't know how to communicate with these extensions -on its own. A little glue will help. Up until now you've been -calling I<perl_parse()>, handing it NULL for the second argument: - - perl_parse(my_perl, NULL, argc, my_argv, NULL); - -That's where the glue code can be inserted to create the initial contact between -Perl and linked C/C++ routines. Let's take a look some pieces of I<perlmain.c> -to see how Perl does this: - - static void xs_init (pTHX); - - EXTERN_C void boot_DynaLoader (pTHX_ CV* cv); - EXTERN_C void boot_Socket (pTHX_ CV* cv); - - - EXTERN_C void - xs_init(pTHX) - { - char *file = __FILE__; - /* DynaLoader is a special case */ - newXS("DynaLoader::boot_DynaLoader", boot_DynaLoader, file); - newXS("Socket::bootstrap", boot_Socket, file); - } - -Simply put: for each extension linked with your Perl executable -(determined during its initial configuration on your -computer or when adding a new extension), -a Perl subroutine is created to incorporate the extension's -routines. Normally, that subroutine is named -I<Module::bootstrap()> and is invoked when you say I<use Module>. In -turn, this hooks into an XSUB, I<boot_Module>, which creates a Perl -counterpart for each of the extension's XSUBs. Don't worry about this -part; leave that to the I<xsubpp> and extension authors. If your -extension is dynamically loaded, DynaLoader creates I<Module::bootstrap()> -for you on the fly. In fact, if you have a working DynaLoader then there -is rarely any need to link in any other extensions statically. - - -Once you have this code, slap it into the second argument of I<perl_parse()>: - - - perl_parse(my_perl, xs_init, argc, my_argv, NULL); - - -Then compile: - - % cc -o interp interp.c `perl -MExtUtils::Embed -e ccopts -e ldopts` - - % interp - use Socket; - use SomeDynamicallyLoadedModule; - - print "Now I can use extensions!\n"' - -B<ExtUtils::Embed> can also automate writing the I<xs_init> glue code. - - % perl -MExtUtils::Embed -e xsinit -- -o perlxsi.c - % cc -c perlxsi.c `perl -MExtUtils::Embed -e ccopts` - % cc -c interp.c `perl -MExtUtils::Embed -e ccopts` - % cc -o interp perlxsi.o interp.o `perl -MExtUtils::Embed -e ldopts` - -Consult L<perlxs>, L<perlguts>, and L<perlapi> for more details. - -=head1 Hiding Perl_ - -If you completely hide the short forms of the Perl public API, -add -DPERL_NO_SHORT_NAMES to the compilation flags. This means that -for example instead of writing - - warn("%d bottles of beer on the wall", bottlecount); - -you will have to write the explicit full form - - Perl_warn(aTHX_ "%d bottles of beer on the wall", bottlecount); - -(See L<perlguts/"Background and PERL_IMPLICIT_CONTEXT"> for the explanation -of the C<aTHX_>. ) Hiding the short forms is very useful for avoiding -all sorts of nasty (C preprocessor or otherwise) conflicts with other -software packages (Perl defines about 2400 APIs with these short names, -take or leave few hundred, so there certainly is room for conflict.) - -=head1 MORAL - -You can sometimes I<write faster code> in C, but -you can always I<write code faster> in Perl. Because you can use -each from the other, combine them as you wish. - - -=head1 AUTHOR - -Jon Orwant <F<orwant@media.mit.edu>> and Doug MacEachern -<F<dougm@covalent.net>>, with small contributions from Tim Bunce, Tom -Christiansen, Guy Decoux, Hallvard Furuseth, Dov Grobgeld, and Ilya -Zakharevich. - -Doug MacEachern has an article on embedding in Volume 1, Issue 4 of -The Perl Journal ( http://www.tpj.com/ ). Doug is also the developer of the -most widely-used Perl embedding: the mod_perl system -(perl.apache.org), which embeds Perl in the Apache web server. -Oracle, Binary Evolution, ActiveState, and Ben Sugars's nsapi_perl -have used this model for Oracle, Netscape and Internet Information -Server Perl plugins. - -=head1 COPYRIGHT - -Copyright (C) 1995, 1996, 1997, 1998 Doug MacEachern and Jon Orwant. All -Rights Reserved. - -This document may be distributed under the same terms as Perl itself. |