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Diffstat (limited to 'Master/tlpkg/tlperl/lib/pods/perlapio.pod')
-rw-r--r-- | Master/tlpkg/tlperl/lib/pods/perlapio.pod | 525 |
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diff --git a/Master/tlpkg/tlperl/lib/pods/perlapio.pod b/Master/tlpkg/tlperl/lib/pods/perlapio.pod deleted file mode 100644 index bb7115f8e8c..00000000000 --- a/Master/tlpkg/tlperl/lib/pods/perlapio.pod +++ /dev/null @@ -1,525 +0,0 @@ -=head1 NAME - -perlapio - perl's IO abstraction interface. - -=head1 SYNOPSIS - - #define PERLIO_NOT_STDIO 0 /* For co-existence with stdio only */ - #include <perlio.h> /* Usually via #include <perl.h> */ - - PerlIO *PerlIO_stdin(void); - PerlIO *PerlIO_stdout(void); - PerlIO *PerlIO_stderr(void); - - PerlIO *PerlIO_open(const char *path,const char *mode); - PerlIO *PerlIO_fdopen(int fd, const char *mode); - PerlIO *PerlIO_reopen(const char *path, const char *mode, PerlIO *old); /* deprecated */ - int PerlIO_close(PerlIO *f); - - int PerlIO_stdoutf(const char *fmt,...) - int PerlIO_puts(PerlIO *f,const char *string); - int PerlIO_putc(PerlIO *f,int ch); - int PerlIO_write(PerlIO *f,const void *buf,size_t numbytes); - int PerlIO_printf(PerlIO *f, const char *fmt,...); - int PerlIO_vprintf(PerlIO *f, const char *fmt, va_list args); - int PerlIO_flush(PerlIO *f); - - int PerlIO_eof(PerlIO *f); - int PerlIO_error(PerlIO *f); - void PerlIO_clearerr(PerlIO *f); - - int PerlIO_getc(PerlIO *d); - int PerlIO_ungetc(PerlIO *f,int ch); - int PerlIO_read(PerlIO *f, void *buf, size_t numbytes); - - int PerlIO_fileno(PerlIO *f); - - void PerlIO_setlinebuf(PerlIO *f); - - Off_t PerlIO_tell(PerlIO *f); - int PerlIO_seek(PerlIO *f, Off_t offset, int whence); - void PerlIO_rewind(PerlIO *f); - - int PerlIO_getpos(PerlIO *f, SV *save); /* prototype changed */ - int PerlIO_setpos(PerlIO *f, SV *saved); /* prototype changed */ - - int PerlIO_fast_gets(PerlIO *f); - int PerlIO_has_cntptr(PerlIO *f); - int PerlIO_get_cnt(PerlIO *f); - char *PerlIO_get_ptr(PerlIO *f); - void PerlIO_set_ptrcnt(PerlIO *f, char *ptr, int count); - - int PerlIO_canset_cnt(PerlIO *f); /* deprecated */ - void PerlIO_set_cnt(PerlIO *f, int count); /* deprecated */ - - int PerlIO_has_base(PerlIO *f); - char *PerlIO_get_base(PerlIO *f); - int PerlIO_get_bufsiz(PerlIO *f); - - PerlIO *PerlIO_importFILE(FILE *stdio, const char *mode); - FILE *PerlIO_exportFILE(PerlIO *f, int flags); - FILE *PerlIO_findFILE(PerlIO *f); - void PerlIO_releaseFILE(PerlIO *f,FILE *stdio); - - int PerlIO_apply_layers(PerlIO *f, const char *mode, const char *layers); - int PerlIO_binmode(PerlIO *f, int ptype, int imode, const char *layers); - void PerlIO_debug(const char *fmt,...) - -=head1 DESCRIPTION - -Perl's source code, and extensions that want maximum portability, -should use the above functions instead of those defined in ANSI C's -I<stdio.h>. The perl headers (in particular "perlio.h") will -C<#define> them to the I/O mechanism selected at Configure time. - -The functions are modeled on those in I<stdio.h>, but parameter order -has been "tidied up a little". - -C<PerlIO *> takes the place of FILE *. Like FILE * it should be -treated as opaque (it is probably safe to assume it is a pointer to -something). - -There are currently three implementations: - -=over 4 - -=item 1. USE_STDIO - -All above are #define'd to stdio functions or are trivial wrapper -functions which call stdio. In this case I<only> PerlIO * is a FILE *. -This has been the default implementation since the abstraction was -introduced in perl5.003_02. - -=item 2. USE_SFIO - -A "legacy" implementation in terms of the "sfio" library. Used for -some specialist applications on Unix machines ("sfio" is not widely -ported away from Unix). Most of above are #define'd to the sfio -functions. PerlIO * is in this case Sfio_t *. - -=item 3. USE_PERLIO - -Introduced just after perl5.7.0, this is a re-implementation of the -above abstraction which allows perl more control over how IO is done -as it decouples IO from the way the operating system and C library -choose to do things. For USE_PERLIO PerlIO * has an extra layer of -indirection - it is a pointer-to-a-pointer. This allows the PerlIO * -to remain with a known value while swapping the implementation around -underneath I<at run time>. In this case all the above are true (but -very simple) functions which call the underlying implementation. - -This is the only implementation for which C<PerlIO_apply_layers()> -does anything "interesting". - -The USE_PERLIO implementation is described in L<perliol>. - -=back - -Because "perlio.h" is a thin layer (for efficiency) the semantics of -these functions are somewhat dependent on the underlying implementation. -Where these variations are understood they are noted below. - -Unless otherwise noted, functions return 0 on success, or a negative -value (usually C<EOF> which is usually -1) and set C<errno> on error. - -=over 4 - -=item B<PerlIO_stdin()>, B<PerlIO_stdout()>, B<PerlIO_stderr()> - -Use these rather than C<stdin>, C<stdout>, C<stderr>. They are written -to look like "function calls" rather than variables because this makes -it easier to I<make them> function calls if platform cannot export data -to loaded modules, or if (say) different "threads" might have different -values. - -=item B<PerlIO_open(path, mode)>, B<PerlIO_fdopen(fd,mode)> - -These correspond to fopen()/fdopen() and the arguments are the same. -Return C<NULL> and set C<errno> if there is an error. There may be an -implementation limit on the number of open handles, which may be lower -than the limit on the number of open files - C<errno> may not be set -when C<NULL> is returned if this limit is exceeded. - -=item B<PerlIO_reopen(path,mode,f)> - -While this currently exists in all three implementations perl itself -does not use it. I<As perl does not use it, it is not well tested.> - -Perl prefers to C<dup> the new low-level descriptor to the descriptor -used by the existing PerlIO. This may become the behaviour of this -function in the future. - -=item B<PerlIO_printf(f,fmt,...)>, B<PerlIO_vprintf(f,fmt,a)> - -These are fprintf()/vfprintf() equivalents. - -=item B<PerlIO_stdoutf(fmt,...)> - -This is printf() equivalent. printf is #defined to this function, -so it is (currently) legal to use C<printf(fmt,...)> in perl sources. - -=item B<PerlIO_read(f,buf,count)>, B<PerlIO_write(f,buf,count)> - -These correspond functionally to fread() and fwrite() but the -arguments and return values are different. The PerlIO_read() and -PerlIO_write() signatures have been modeled on the more sane low level -read() and write() functions instead: The "file" argument is passed -first, there is only one "count", and the return value can distinguish -between error and C<EOF>. - -Returns a byte count if successful (which may be zero or -positive), returns negative value and sets C<errno> on error. -Depending on implementation C<errno> may be C<EINTR> if operation was -interrupted by a signal. - -=item B<PerlIO_close(f)> - -Depending on implementation C<errno> may be C<EINTR> if operation was -interrupted by a signal. - -=item B<PerlIO_puts(f,s)>, B<PerlIO_putc(f,c)> - -These correspond to fputs() and fputc(). -Note that arguments have been revised to have "file" first. - -=item B<PerlIO_ungetc(f,c)> - -This corresponds to ungetc(). Note that arguments have been revised -to have "file" first. Arranges that next read operation will return -the byte B<c>. Despite the implied "character" in the name only -values in the range 0..0xFF are defined. Returns the byte B<c> on -success or -1 (C<EOF>) on error. The number of bytes that can be -"pushed back" may vary, only 1 character is certain, and then only if -it is the last character that was read from the handle. - -=item B<PerlIO_getc(f)> - -This corresponds to getc(). -Despite the c in the name only byte range 0..0xFF is supported. -Returns the character read or -1 (C<EOF>) on error. - -=item B<PerlIO_eof(f)> - -This corresponds to feof(). Returns a true/false indication of -whether the handle is at end of file. For terminal devices this may -or may not be "sticky" depending on the implementation. The flag is -cleared by PerlIO_seek(), or PerlIO_rewind(). - -=item B<PerlIO_error(f)> - -This corresponds to ferror(). Returns a true/false indication of -whether there has been an IO error on the handle. - -=item B<PerlIO_fileno(f)> - -This corresponds to fileno(), note that on some platforms, the meaning -of "fileno" may not match Unix. Returns -1 if the handle has no open -descriptor associated with it. - -=item B<PerlIO_clearerr(f)> - -This corresponds to clearerr(), i.e., clears 'error' and (usually) -'eof' flags for the "stream". Does not return a value. - -=item B<PerlIO_flush(f)> - -This corresponds to fflush(). Sends any buffered write data to the -underlying file. If called with C<NULL> this may flush all open -streams (or core dump with some USE_STDIO implementations). Calling -on a handle open for read only, or on which last operation was a read -of some kind may lead to undefined behaviour on some USE_STDIO -implementations. The USE_PERLIO (layers) implementation tries to -behave better: it flushes all open streams when passed C<NULL>, and -attempts to retain data on read streams either in the buffer or by -seeking the handle to the current logical position. - -=item B<PerlIO_seek(f,offset,whence)> - -This corresponds to fseek(). Sends buffered write data to the -underlying file, or discards any buffered read data, then positions -the file descriptor as specified by B<offset> and B<whence> (sic). -This is the correct thing to do when switching between read and write -on the same handle (see issues with PerlIO_flush() above). Offset is -of type C<Off_t> which is a perl Configure value which may not be same -as stdio's C<off_t>. - -=item B<PerlIO_tell(f)> - -This corresponds to ftell(). Returns the current file position, or -(Off_t) -1 on error. May just return value system "knows" without -making a system call or checking the underlying file descriptor (so -use on shared file descriptors is not safe without a -PerlIO_seek()). Return value is of type C<Off_t> which is a perl -Configure value which may not be same as stdio's C<off_t>. - -=item B<PerlIO_getpos(f,p)>, B<PerlIO_setpos(f,p)> - -These correspond (loosely) to fgetpos() and fsetpos(). Rather than -stdio's Fpos_t they expect a "Perl Scalar Value" to be passed. What is -stored there should be considered opaque. The layout of the data may -vary from handle to handle. When not using stdio or if platform does -not have the stdio calls then they are implemented in terms of -PerlIO_tell() and PerlIO_seek(). - -=item B<PerlIO_rewind(f)> - -This corresponds to rewind(). It is usually defined as being - - PerlIO_seek(f,(Off_t)0L, SEEK_SET); - PerlIO_clearerr(f); - -=item B<PerlIO_tmpfile()> - -This corresponds to tmpfile(), i.e., returns an anonymous PerlIO or -NULL on error. The system will attempt to automatically delete the -file when closed. On Unix the file is usually C<unlink>-ed just after -it is created so it does not matter how it gets closed. On other -systems the file may only be deleted if closed via PerlIO_close() -and/or the program exits via C<exit>. Depending on the implementation -there may be "race conditions" which allow other processes access to -the file, though in general it will be safer in this regard than -ad. hoc. schemes. - -=item B<PerlIO_setlinebuf(f)> - -This corresponds to setlinebuf(). Does not return a value. What -constitutes a "line" is implementation dependent but usually means -that writing "\n" flushes the buffer. What happens with things like -"this\nthat" is uncertain. (Perl core uses it I<only> when "dumping"; -it has nothing to do with $| auto-flush.) - -=back - -=head2 Co-existence with stdio - -There is outline support for co-existence of PerlIO with stdio. -Obviously if PerlIO is implemented in terms of stdio there is no -problem. However in other cases then mechanisms must exist to create a -FILE * which can be passed to library code which is going to use stdio -calls. - -The first step is to add this line: - - #define PERLIO_NOT_STDIO 0 - -I<before> including any perl header files. (This will probably become -the default at some point). That prevents "perlio.h" from attempting -to #define stdio functions onto PerlIO functions. - -XS code is probably better using "typemap" if it expects FILE * -arguments. The standard typemap will be adjusted to comprehend any -changes in this area. - -=over 4 - -=item B<PerlIO_importFILE(f,mode)> - -Used to get a PerlIO * from a FILE *. - -The mode argument should be a string as would be passed to -fopen/PerlIO_open. If it is NULL then - for legacy support - the code -will (depending upon the platform and the implementation) either -attempt to empirically determine the mode in which I<f> is open, or -use "r+" to indicate a read/write stream. - -Once called the FILE * should I<ONLY> be closed by calling -C<PerlIO_close()> on the returned PerlIO *. - -The PerlIO is set to textmode. Use PerlIO_binmode if this is -not the desired mode. - -This is B<not> the reverse of PerlIO_exportFILE(). - -=item B<PerlIO_exportFILE(f,mode)> - -Given a PerlIO * create a 'native' FILE * suitable for passing to code -expecting to be compiled and linked with ANSI C I<stdio.h>. The mode -argument should be a string as would be passed to fopen/PerlIO_open. -If it is NULL then - for legacy support - the FILE * is opened in same -mode as the PerlIO *. - -The fact that such a FILE * has been 'exported' is recorded, (normally -by pushing a new :stdio "layer" onto the PerlIO *), which may affect -future PerlIO operations on the original PerlIO *. You should not -call C<fclose()> on the file unless you call C<PerlIO_releaseFILE()> -to disassociate it from the PerlIO *. (Do not use PerlIO_importFILE() -for doing the disassociation.) - -Calling this function repeatedly will create a FILE * on each call -(and will push an :stdio layer each time as well). - -=item B<PerlIO_releaseFILE(p,f)> - -Calling PerlIO_releaseFILE informs PerlIO that all use of FILE * is -complete. It is removed from the list of 'exported' FILE *s, and the -associated PerlIO * should revert to its original behaviour. - -Use this to disassociate a file from a PerlIO * that was associated -using PerlIO_exportFILE(). - -=item B<PerlIO_findFILE(f)> - -Returns a native FILE * used by a stdio layer. If there is none, it -will create one with PerlIO_exportFILE. In either case the FILE * -should be considered as belonging to PerlIO subsystem and should -only be closed by calling C<PerlIO_close()>. - - -=back - -=head2 "Fast gets" Functions - -In addition to standard-like API defined so far above there is an -"implementation" interface which allows perl to get at internals of -PerlIO. The following calls correspond to the various FILE_xxx macros -determined by Configure - or their equivalent in other -implementations. This section is really of interest to only those -concerned with detailed perl-core behaviour, implementing a PerlIO -mapping or writing code which can make use of the "read ahead" that -has been done by the IO system in the same way perl does. Note that -any code that uses these interfaces must be prepared to do things the -traditional way if a handle does not support them. - -=over 4 - -=item B<PerlIO_fast_gets(f)> - -Returns true if implementation has all the interfaces required to -allow perl's C<sv_gets> to "bypass" normal IO mechanism. This can -vary from handle to handle. - - PerlIO_fast_gets(f) = PerlIO_has_cntptr(f) && \ - PerlIO_canset_cnt(f) && \ - 'Can set pointer into buffer' - -=item B<PerlIO_has_cntptr(f)> - -Implementation can return pointer to current position in the "buffer" -and a count of bytes available in the buffer. Do not use this - use -PerlIO_fast_gets. - -=item B<PerlIO_get_cnt(f)> - -Return count of readable bytes in the buffer. Zero or negative return -means no more bytes available. - -=item B<PerlIO_get_ptr(f)> - -Return pointer to next readable byte in buffer, accessing via the -pointer (dereferencing) is only safe if PerlIO_get_cnt() has returned -a positive value. Only positive offsets up to value returned by -PerlIO_get_cnt() are allowed. - -=item B<PerlIO_set_ptrcnt(f,p,c)> - -Set pointer into buffer, and a count of bytes still in the -buffer. Should be used only to set pointer to within range implied by -previous calls to C<PerlIO_get_ptr> and C<PerlIO_get_cnt>. The two -values I<must> be consistent with each other (implementation may only -use one or the other or may require both). - -=item B<PerlIO_canset_cnt(f)> - -Implementation can adjust its idea of number of bytes in the buffer. -Do not use this - use PerlIO_fast_gets. - -=item B<PerlIO_set_cnt(f,c)> - -Obscure - set count of bytes in the buffer. Deprecated. Only usable -if PerlIO_canset_cnt() returns true. Currently used in only doio.c to -force count less than -1 to -1. Perhaps should be PerlIO_set_empty or -similar. This call may actually do nothing if "count" is deduced from -pointer and a "limit". Do not use this - use PerlIO_set_ptrcnt(). - -=item B<PerlIO_has_base(f)> - -Returns true if implementation has a buffer, and can return pointer -to whole buffer and its size. Used by perl for B<-T> / B<-B> tests. -Other uses would be very obscure... - -=item B<PerlIO_get_base(f)> - -Return I<start> of buffer. Access only positive offsets in the buffer -up to the value returned by PerlIO_get_bufsiz(). - -=item B<PerlIO_get_bufsiz(f)> - -Return the I<total number of bytes> in the buffer, this is neither the -number that can be read, nor the amount of memory allocated to the -buffer. Rather it is what the operating system and/or implementation -happened to C<read()> (or whatever) last time IO was requested. - -=back - -=head2 Other Functions - -=over 4 - -=item PerlIO_apply_layers(f,mode,layers) - -The new interface to the USE_PERLIO implementation. The layers ":crlf" -and ":raw" are only ones allowed for other implementations and those -are silently ignored. (As of perl5.8 ":raw" is deprecated.) Use -PerlIO_binmode() below for the portable case. - -=item PerlIO_binmode(f,ptype,imode,layers) - -The hook used by perl's C<binmode> operator. -B<ptype> is perl's character for the kind of IO: - -=over 8 - -=item 'E<lt>' read - -=item 'E<gt>' write - -=item '+' read/write - -=back - -B<imode> is C<O_BINARY> or C<O_TEXT>. - -B<layers> is a string of layers to apply, only ":crlf" makes sense in -the non USE_PERLIO case. (As of perl5.8 ":raw" is deprecated in favour -of passing NULL.) - -Portable cases are: - - PerlIO_binmode(f,ptype,O_BINARY,NULL); -and - PerlIO_binmode(f,ptype,O_TEXT,":crlf"); - -On Unix these calls probably have no effect whatsoever. Elsewhere -they alter "\n" to CR,LF translation and possibly cause a special text -"end of file" indicator to be written or honoured on read. The effect -of making the call after doing any IO to the handle depends on the -implementation. (It may be ignored, affect any data which is already -buffered as well, or only apply to subsequent data.) - -=item PerlIO_debug(fmt,...) - -PerlIO_debug is a printf()-like function which can be used for -debugging. No return value. Its main use is inside PerlIO where using -real printf, warn() etc. would recursively call PerlIO and be a -problem. - -PerlIO_debug writes to the file named by $ENV{'PERLIO_DEBUG'} typical -use might be - - Bourne shells (sh, ksh, bash, zsh, ash, ...): - PERLIO_DEBUG=/dev/tty ./perl somescript some args - - Csh/Tcsh: - setenv PERLIO_DEBUG /dev/tty - ./perl somescript some args - - If you have the "env" utility: - env PERLIO_DEBUG=/dev/tty ./perl somescript some args - - Win32: - set PERLIO_DEBUG=CON - perl somescript some args - -If $ENV{'PERLIO_DEBUG'} is not set PerlIO_debug() is a no-op. - -=back |