/* Flushing buffers of 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 "fpurge.h"

#if HAVE___FPURGE                   /* glibc >= 2.2, Solaris >= 7 */
# include <stdio_ext.h>
#endif
#include <stdlib.h>

int
fpurge (FILE *fp)
{
#if HAVE___FPURGE                   /* glibc >= 2.2, Solaris >= 7 */

  __fpurge (fp);
  /* The __fpurge function does not have a return value.  */
  return 0;

#elif HAVE_FPURGE                   /* FreeBSD, NetBSD, OpenBSD, MacOS X */

  /* Call the system's fpurge function.  */
# undef fpurge
# if !HAVE_DECL_FPURGE
  extern int fpurge (FILE *);
# endif
  int result = fpurge (fp);
# if defined __sferror              /* FreeBSD, NetBSD, OpenBSD, MacOS X, Cygwin */
  if (result == 0)
    /* Correct the invariants that fpurge broke.
       <stdio.h> on BSD systems says:
         "The following always hold: if _flags & __SRD, _w is 0."
       If this invariant is not fulfilled and the stream is read-write but
       currently writing, subsequent putc or fputc calls will write directly
       into the buffer, although they shouldn't be allowed to.  */
    if ((fp->_flags & __SRD) != 0)
      fp->_w = 0;
# endif
  return result;

#else

  /* Most systems provide FILE as a struct and the necessary bitmask in
     <stdio.h>, because they need it for implementing getc() and putc() as
     fast macros.  */
# if defined _IO_ferror_unlocked    /* GNU libc, BeOS */
  fp->_IO_read_end = fp->_IO_read_ptr;
  fp->_IO_write_ptr = fp->_IO_write_base;
  /* Avoid memory leak when there is an active ungetc buffer.  */
  if (fp->_IO_save_base != NULL)
    {
      free (fp->_IO_save_base);
      fp->_IO_save_base = NULL;
    }
  return 0;
# elif defined __sferror            /* FreeBSD, NetBSD, OpenBSD, MacOS X, Cygwin */
  fp->_p = fp->_bf._base;
  fp->_r = 0;
  fp->_w = ((fp->_flags & (__SLBF | __SNBF | __SRD)) == 0 /* fully buffered and not currently reading? */
	    ? fp->_bf._size
	    : 0);
  /* Avoid memory leak when there is an active ungetc buffer.  */
#  if defined __NetBSD__ || defined __OpenBSD__ /* NetBSD, OpenBSD */
   /* See <http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/stdio/fileext.h?rev=HEAD&content-type=text/x-cvsweb-markup>
      and <http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libc/stdio/fileext.h?rev=HEAD&content-type=text/x-cvsweb-markup> */
#   define fp_ub ((struct { struct __sbuf _ub; } *) fp->_ext._base)->_ub
#  else                                         /* FreeBSD, MacOS X, Cygwin */
#   define fp_ub fp->_ub
#  endif
  if (fp_ub._base != NULL)
    {
      if (fp_ub._base != fp->_ubuf)
	free (fp_ub._base);
      fp_ub._base = NULL;
    }
  return 0;
# elif defined _IOERR               /* AIX, HP-UX, IRIX, OSF/1, Solaris, mingw */
  fp->_ptr = fp->_base;
  if (fp->_ptr != NULL)
    fp->_cnt = 0;
  return 0;
# elif defined __UCLIBC__           /* uClibc */
#  ifdef __STDIO_BUFFERS
  if (fp->__modeflags & __FLAG_WRITING)
    fp->__bufpos = fp->__bufstart;
  else if (fp->__modeflags & (__FLAG_READONLY | __FLAG_READING))
    fp->__bufpos = fp->__bufread;
#  endif
  return 0;
# else
 #error "Please port gnulib fpurge.c to your platform! Look at the definitions of fflush, setvbuf and ungetc on your system, then report this to bug-gnulib."
# endif

#endif
}