Eric Blake wrote:
> m4 already calls close_stdin always, whether or not it read from stdin, so
> the current implementation is correct even when stdin is still in the
> initial state. However, if you want to optimize it further, such patches
> are worth considering.
Here is a primitive function that could be used in close_stdin to optimize
away the lseek system call.
The function name 'finpending()' is not particularly good. Can you think of a
better name?
Tested on glibc, MacOS X, NetBSD, AIX, HP-UX, IRIX, Solaris, OSF/1, BeOS, mingw.
Comments?
2007-08-18 Bruno Haible <[EMAIL PROTECTED]>
* modules/finpending: New file.
* lib/finpending.h: New file.
* lib/finpending.c: New file.
============================= modules/finpending =============================
Description:
finpending() function: Determine the number of bytes waiting in the input
buffer of a stream.
Files:
lib/finpending.h
lib/finpending.c
Depends-on:
configure.ac:
Makefile.am:
lib_SOURCES += finpending.c
Include:
"finpending.h"
License:
LGPL
Maintainer:
Bruno Haible
============================== lib/finpending.h ==============================
/* Retrieve information about a FILE stream.
Copyright (C) 2007 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
#include <stddef.h>
#include <stdio.h>
#ifdef __cplusplus
extern "C" {
#endif
/* Assuming the stream STREAM is open for reading:
Return the number of bytes waiting in the input buffer of STREAM.
If this number is 0 and the stream is not currently writing,
fflush (STREAM) is known to be a no-op.
STREAM must not be wide-character oriented. */
extern size_t finpending (FILE *stream);
#ifdef __cplusplus
}
#endif
============================== lib/finpending.c ==============================
/* Retrieve information about a FILE stream.
Copyright (C) 2007 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation,
Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
#include <config.h>
/* Specification. */
#include "finpending.h"
size_t
finpending (FILE *fp)
{
#if defined _IO_ferror_unlocked /* GNU libc, BeOS */
if (fp->_IO_write_ptr > fp->_IO_write_base)
return 0;
return fp->_IO_read_end - fp->_IO_read_ptr;
#elif defined __sferror /* FreeBSD, NetBSD, OpenBSD, MacOS X,
Cygwin */
if ((fp->_flags & __SWR) != 0 || fp->_r < 0)
return 0;
return fp->_r;
#elif defined _IOERR /* AIX, HP-UX, IRIX, OSF/1, Solaris, mingw
*/
# if defined __sun && defined __sparc && defined _LP64 /* Solaris/SPARC 64-bit
*/
# define fp_ ((struct { unsigned char *_ptr; \
unsigned char *_base; \
unsigned char *_end; \
long _cnt; \
} *) fp)
if ((((unsigned int *) fp) [9] & _IOWRT) != 0)
return 0;
return fp_->_cnt;
# else
if ((fp->_flag & _IOWRT) != 0)
return 0;
return fp->_cnt;
# endif
#elif defined __UCLIBC__ /* uClibc */
# ifdef __STDIO_BUFFERS
if (fp->__modeflags & __FLAG_WRITING)
return 0;
return fp->__bufread - fp->__bufpos;
# else
return 0;
# endif
#else
#error "Please port gnulib finpending.c to your platform! Look at the
definition of fflush, fread on your system, then report this to bug-gnulib."
#endif
}
==============================================================================
