=head1 NAME

perlapio - perl's IO abstraction interface.

=head1 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 *);

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 *);

=head1 DESCRIPTION

Perl's source code should use the above functions instead of those

defined in ANSI C's I<stdio.h>. The perl headers 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".

=over 4

=item B<PerlIO *>

This 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).

=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() arguments are the same.

=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 to fread() and fwrite(). Note that arguments

are different, there is only one "count" and order has

"file" first.

=item B<PerlIO_close(f)>

=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.

=item B<PerlIO_getc(f)>

This corresponds to getc().

=item B<PerlIO_eof(f)>

This corresponds to feof().

=item B<PerlIO_error(f)>

This corresponds to ferror().

=item B<PerlIO_fileno(f)>

This corresponds to fileno(), note that on some platforms,

the meaning of "fileno" may not match Unix.

=item B<PerlIO_clearerr(f)>

This corresponds to clearerr(), i.e., clears 'eof' and 'error'

flags for the "stream".

=item B<PerlIO_flush(f)>

This corresponds to fflush().

=item B<PerlIO_tell(f)>

This corresponds to ftell().

=item B<PerlIO_seek(f,o,w)>

This corresponds to fseek().

=item B<PerlIO_getpos(f,p)>, B<PerlIO_setpos(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().

=item B<PerlIO_rewind(f)>

This corresponds to rewind(). Note may be redefined

in terms of PerlIO_seek() at some point.

=item B<PerlIO_tmpfile()>

This corresponds to tmpfile(), i.e., returns an anonymous

PerlIO which will automatically be deleted when closed.

=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 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.

=over 4

=item B<PerlIO_importFILE(f,flags)>

Used to get a PerlIO * from a FILE *.

May need additional arguments, interface under review.

=item B<PerlIO_exportFILE(f,flags)>

Given an PerlIO * return a 'native' FILE * suitable for

passing to code expecting to be compiled and linked with

ANSI C I<stdio.h>.

The fact that such a FILE * has been 'exported' is recorded,

and may affect future PerlIO operations on the original

PerlIO *.

=item B<PerlIO_findFILE(f)>

Returns previously 'exported' FILE * (if any).

Place holder until interface is fully defined.

=item B<PerlIO_releaseFILE(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.

=item B<PerlIO_setlinebuf(f)>

This corresponds to setlinebuf(). Use is deprecated pending

further discussion. (Perl core uses it I<only> when "dumping";

it has nothing to do with $| auto-flush.)

=back

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.

=over 4

=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.

=item B<PerlIO_get_ptr(f)>

Return pointer to next readable byte in buffer.

=item B<PerlIO_get_cnt(f)>

Return count of readable bytes in the buffer.

=item B<PerlIO_canset_cnt(f)>

Implementation can adjust its idea of number of

bytes in the buffer.

=item B<PerlIO_fast_gets(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'

=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>.

=item B<PerlIO_set_cnt(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".

=item B<PerlIO_has_base(f)>

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.

=item B<PerlIO_get_bufsiz(f)>

Return I<total size> of buffer.

=back