PERLAPIO(1) PERLAPIO(1)
NAME
perlapio - perl's IO abstraction interface.
SYNOPSIS
PerlIO *PerlIO_stdin(void);
PerlIO *PerlIO_stdout(void);
PerlIO *PerlIO_stderr(void);
PerlIO *PerlIO_open(const char *,const char *);
int PerlIO_close(PerlIO *);
int PerlIO_stdoutf(const char *,...)
int PerlIO_puts(PerlIO *,const char *);
int PerlIO_putc(PerlIO *,int);
int PerlIO_write(PerlIO *,const void *,size_t);
int PerlIO_printf(PerlIO *, const char *,...);
int PerlIO_vprintf(PerlIO *, const char *, va_list);
int PerlIO_flush(PerlIO *);
int PerlIO_eof(PerlIO *);
int PerlIO_error(PerlIO *);
void PerlIO_clearerr(PerlIO *);
int PerlIO_getc(PerlIO *);
int PerlIO_ungetc(PerlIO *,int);
int PerlIO_read(PerlIO *,void *,size_t);
int PerlIO_fileno(PerlIO *);
PerlIO *PerlIO_fdopen(int, const char *);
PerlIO *PerlIO_importFILE(FILE *, int flags);
FILE *PerlIO_exportFILE(PerlIO *, int flags);
FILE *PerlIO_findFILE(PerlIO *);
void PerlIO_releaseFILE(PerlIO *,FILE *);
void PerlIO_setlinebuf(PerlIO *);
long PerlIO_tell(PerlIO *);
int PerlIO_seek(PerlIO *,off_t,int);
int PerlIO_getpos(PerlIO *,Fpos_t *)
int PerlIO_setpos(PerlIO *,Fpos_t *)
void PerlIO_rewind(PerlIO *);
int PerlIO_has_base(PerlIO *);
int PerlIO_has_cntptr(PerlIO *);
int PerlIO_fast_gets(PerlIO *);
int PerlIO_canset_cnt(PerlIO *);
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char *PerlIO_get_ptr(PerlIO *);
int PerlIO_get_cnt(PerlIO *);
void PerlIO_set_cnt(PerlIO *,int);
void PerlIO_set_ptrcnt(PerlIO *,char *,int);
char *PerlIO_get_base(PerlIO *);
int PerlIO_get_bufsiz(PerlIO *);
DESCRIPTION
Perl's source code should use the above functions instead of those
defined in ANSI C's stdio.h, perlio.h will the #define them to the I/O
mechanism selected at Configure time.
The functions are modeled on those in stdio.h, but parameter order has
been "tidied up a little".
PerlIO *
This takes the place of FILE *. Unlike FILE * it should be treated as
opaque (it is probably safe to assume it is a pointer to something).
PerlIOstdin(), PerlIOstdout(), PerlIOstderr()
Use these rather than stdin, stdout, stderr. They are written to look
like "function calls" rather than variables because this makes it
easier to make them function calls if platform cannot export data to
loaded modules, or if (say) different "threads" might have different
values.
PerlIOopen(path, mode), PerlIOfdopen(fd,mode)
These correspond to fopen()/fdopen() arguments are the same.
PerlIOprintf(f,fmt,...), PerlIOvprintf(f,fmt,a)
These are is fprintf()/vfprintf equivalents.
PerlIOstdoutf(fmt,...)
This is printf() equivalent. printf is #defined to this function, so
it is (currently) legal to use printf(fmt,...) in perl sources.
PerlIOread(f,buf,count), PerlIOwrite(f,buf,count)
These correspond to fread() and fwrite(). Note that arguments are
different, there is only one "count" and order has "file" first.
PerlIOclose(f)
PerlIOputs(f,s), PerlIOputc(f,c)
These correspond to fputs() and fputc(). Note that arguments have
been revised to have "file" first.
PerlIOungetc(f,c)
This corresponds to ungetc(). Note that arguments have been revised
to have "file" first.
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PerlIOgetc(f)
This corresponds to getc().
PerlIOeof(f)
This corresponds to feof().
PerlIOerror(f)
This corresponds to ferror().
PerlIOfileno(f)
This corresponds to fileno(), note that on some platforms, the
meaning of "fileno" may not match Unix.
PerlIOclearerr(f)
This corresponds to clearerr(), i.e., clears 'eof' and 'error' flags
for the "stream".
PerlIOflush(f)
This corresponds to fflush().
PerlIOtell(f)
This corresponds to ftell().
PerlIOseek(f,o,w)
This corresponds to fseek().
PerlIOgetpos(f,p), PerlIOsetpos(f,p)
These correspond to fgetpos() and fsetpos(). If platform does not
have the stdio calls then they are implemented in terms of
PerlIO_tell() and PerlIO_seek().
PerlIOrewind(f)
This corresponds to rewind(). Note may be redefined in terms of
PerlIO_seek() at some point.
PerlIOtmpfile()
This corresponds to tmpfile(), i.e., returns an anonymous PerlIO
which will automatically be deleted when closed.
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 if perlio is implemented on top of (say) sfio then mechanisms
must exist to create a FILE * which can be passed to library code which
is going to use stdio calls.
PerlIOimportFILE(f,flags)
Used to get a PerlIO * from a FILE *. May need additional arguments,
interface under review.
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PerlIOexportFILE(f,flags)
Given an PerlIO * return a 'native' FILE * suitable for passing to
code expecting to be compiled and linked with ANSI C stdio.h.
The fact that such a FILE * has been 'exported' is recorded, and may
affect future PerlIO operations on the original PerlIO *.
PerlIOfindFILE(f)
Returns previously 'exported' FILE * (if any). Place holder until
interface is fully defined.
PerlIOreleaseFILE(p,f)
Calling PerlIO_releaseFILE informs PerlIO that all use of FILE * is
complete. It is removed from list of 'exported' FILE *s, and
associated PerlIO * should revert to original behaviour.
PerlIOsetlinebuf(f)
This corresponds to setlinebuf(). Use is deprecated pending further
discussion. (Perl core uses it only when "dumping" is has nothing to
do with $| auto-flush.)
In addition to user API 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. This
section is really of interest to only those concerned with detailed
perl-core behaviour or implementing a PerlIO mapping.
PerlIOhascntptr(f)
Implementation can return pointer to current position in the "buffer"
and a count of bytes available in the buffer.
PerlIOgetptr(f)
Return pointer to next readable byte in buffer.
PerlIOgetcnt(f)
Return count of readable bytes in the buffer.
PerlIOcansetcnt(f)
Implementation can adjust its idea of number of bytes in the buffer.
PerlIOfastgets(f)
Implementation has all the interfaces required to allow perl's fast
code to handle <FILE> mechanism.
PerlIO_fast_gets(f) = PerlIO_has_cntptr(f) && \
PerlIO_canset_cnt(f) && \
`Can set pointer into buffer'
PerlIOsetptrcnt(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
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previous calls to PerlIO_get_ptr and PerlIO_get_cnt.
PerlIOsetcnt(f,c)
Obscure - set count of bytes in the buffer. Deprecated. Currently
used in only doio.c to force count < -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".
PerlIOhasbase(f)
Implementation has a buffer, and can return pointer to whole buffer
and its size. Used by perl for -T / -B tests. Other uses would be
very obscure...
PerlIOgetbase(f)
Return start of buffer.
PerlIOgetbufsiz(f)
Return total size of buffer.
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