perlapio
(1)
名称
perlapio - perl's IO abstraction interface.
用法概要
#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 */
描述
Perl Programmers Reference Guide PERLAPIO(1)
NAME
perlapio - perl's IO abstraction interface.
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 */
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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,...)
DESCRIPTION
Perl's source code, and extensions that want maximum
portability, should use the above functions instead of those
defined in ANSI C's stdio.h. The perl headers (in
particular "perlio.h") will "#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 *" 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:
1. USE_STDIO
All above are #define'd to stdio functions or are
trivial wrapper functions which call stdio. In this case
only PerlIO * is a FILE *. This has been the default
implementation since the abstraction was introduced in
perl5.003_02.
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 *.
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 at run
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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
"PerlIO_apply_layers()" does anything "interesting".
The USE_PERLIO implementation is described in perliol.
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 "EOF" which is usually -1) and set
"errno" on error.
PerlIO_stdin(), PerlIO_stdout(), PerlIO_stderr()
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.
PerlIO_open(path, mode), PerlIO_fdopen(fd,mode)
These correspond to fopen()/fdopen() and the arguments
are the same. Return "NULL" and set "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 - "errno" may not be
set when "NULL" is returned if this limit is exceeded.
PerlIO_reopen(path,mode,f)
While this currently exists in all three implementations
perl itself does not use it. As perl does not use it, it
is not well tested.
Perl prefers to "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.
PerlIO_printf(f,fmt,...), PerlIO_vprintf(f,fmt,a)
These are fprintf()/vfprintf() equivalents.
PerlIO_stdoutf(fmt,...)
This is printf() equivalent. printf is #defined to this
function, so it is (currently) legal to use
"printf(fmt,...)" in perl sources.
PerlIO_read(f,buf,count), PerlIO_write(f,buf,count)
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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 "EOF".
Returns a byte count if successful (which may be zero or
positive), returns negative value and sets "errno" on
error. Depending on implementation "errno" may be
"EINTR" if operation was interrupted by a signal.
PerlIO_close(f)
Depending on implementation "errno" may be "EINTR" if
operation was interrupted by a signal.
PerlIO_puts(f,s), PerlIO_putc(f,c)
These correspond to fputs() and fputc(). Note that
arguments have been revised to have "file" first.
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 c. Despite the
implied "character" in the name only values in the range
0..0xFF are defined. Returns the byte c on success or -1
("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.
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 ("EOF") on error.
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().
PerlIO_error(f)
This corresponds to ferror(). Returns a true/false
indication of whether there has been an IO error on the
handle.
PerlIO_fileno(f)
This corresponds to fileno(), note that on some
platforms, the meaning of "fileno" may not match Unix.
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Returns -1 if the handle has no open descriptor
associated with it.
PerlIO_clearerr(f)
This corresponds to clearerr(), i.e., clears 'error' and
(usually) 'eof' flags for the "stream". Does not return
a value.
PerlIO_flush(f)
This corresponds to fflush(). Sends any buffered write
data to the underlying file. If called with "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 "NULL", and attempts to retain
data on read streams either in the buffer or by seeking
the handle to the current logical position.
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
offset and 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 "Off_t" which is a perl Configure value which
may not be same as stdio's "off_t".
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 "Off_t" which is a perl Configure value
which may not be same as stdio's "off_t".
PerlIO_getpos(f,p), 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().
PerlIO_rewind(f)
This corresponds to rewind(). It is usually defined as
being
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PerlIO_seek(f,(Off_t)0L, SEEK_SET);
PerlIO_clearerr(f);
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 "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 "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.
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 only when "dumping";
it has nothing to do with $| auto-flush.)
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
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.
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 f is open, or use "r+" to
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indicate a read/write stream.
Once called the FILE * should ONLY be closed by calling
"PerlIO_close()" on the returned PerlIO *.
The PerlIO is set to textmode. Use PerlIO_binmode if
this is not the desired mode.
This is not the reverse of PerlIO_exportFILE().
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 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
"fclose()" on the file unless you call
"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).
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().
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
"PerlIO_close()".
"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
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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.
PerlIO_fast_gets(f)
Returns true if implementation has all the interfaces
required to allow perl's "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'
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.
PerlIO_get_cnt(f)
Return count of readable bytes in the buffer. Zero or
negative return means no more bytes available.
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.
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 "PerlIO_get_ptr" and
"PerlIO_get_cnt". The two values must be consistent with
each other (implementation may only use one or the other
or may require both).
PerlIO_canset_cnt(f)
Implementation can adjust its idea of number of bytes in
the buffer. Do not use this - use PerlIO_fast_gets.
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
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- use PerlIO_set_ptrcnt().
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 -T / -B tests. Other uses would be very
obscure...
PerlIO_get_base(f)
Return start of buffer. Access only positive offsets in
the buffer up to the value returned by
PerlIO_get_bufsiz().
PerlIO_get_bufsiz(f)
Return the 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
"read()" (or whatever) last time IO was requested.
Other Functions
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.
PerlIO_binmode(f,ptype,imode,layers)
The hook used by perl's "binmode" operator. ptype is
perl's character for the kind of IO:
'<' read
'>' write
'+' read/write
imode is "O_BINARY" or "O_TEXT".
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
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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.)
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.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
+---------------+------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+------------------+
|Availability | runtime/perl-512 |
+---------------+------------------+
|Stability | Uncommitted |
+---------------+------------------+
NOTES
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from
http://www.cpan.org/src/5.0/perl-5.12.5.tar.bz2
Further information about this software can be found on the
open source community website at http://www.perl.org/.
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