File: fseeko.c

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/* An fseeko() function that, together with fflush(), is POSIX compliant.
   Copyright (C) 2007-2010 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 3, 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 <stdio.h>

/* Get off_t and lseek.  */
#include <unistd.h>

#include "stdio-impl.h"

int
fseeko (FILE *fp, off_t offset, int whence)
#undef fseeko
#if !HAVE_FSEEKO
# undef fseek
# define fseeko fseek
#endif
{
#if LSEEK_PIPE_BROKEN
  /* mingw gives bogus answers rather than failure on non-seekable files.  */
  if (lseek (fileno (fp), 0, SEEK_CUR) == -1)
    return EOF;
#endif

  /* These tests are based on fpurge.c.  */
#if defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
  if (fp->_IO_read_end == fp->_IO_read_ptr
      && fp->_IO_write_ptr == fp->_IO_write_base
      && fp->_IO_save_base == NULL)
#elif defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, MacOS X, Cygwin */
# if defined __SL64 && defined __SCLE /* Cygwin */
  if ((fp->_flags & __SL64) == 0)
    {
      /* Cygwin 1.5.0 through 1.5.24 failed to open stdin in 64-bit
         mode; but has an fseeko that requires 64-bit mode.  */
      FILE *tmp = fopen ("/dev/null", "r");
      if (!tmp)
        return -1;
      fp->_flags |= __SL64;
      fp->_seek64 = tmp->_seek64;
      fclose (tmp);
    }
# endif
  if (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)
      && fp_ub._base == NULL)
#elif defined __EMX__               /* emx+gcc */
  if (fp->_ptr == fp->_buffer
      && fp->_rcount == 0
      && fp->_wcount == 0
      && fp->_ungetc_count == 0)
#elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw */
  if (fp_->_ptr == fp_->_base
      && (fp_->_ptr == NULL || fp_->_cnt == 0))
#elif defined __UCLIBC__            /* uClibc */
  if (((fp->__modeflags & __FLAG_WRITING) == 0
       || fp->__bufpos == fp->__bufstart)
      && ((fp->__modeflags & (__FLAG_READONLY | __FLAG_READING)) == 0
          || fp->__bufpos == fp->__bufread))
#elif defined __QNX__               /* QNX */
  if ((fp->_Mode & 0x2000 /* _MWRITE */ ? fp->_Next == fp->_Buf : fp->_Next == fp->_Rend)
      && fp->_Rback == fp->_Back + sizeof (fp->_Back)
      && fp->_Rsave == NULL)
#elif defined __MINT__              /* Atari FreeMiNT */
  if (fp->__bufp == fp->__buffer
      && fp->__get_limit == fp->__bufp
      && fp->__put_limit == fp->__bufp
      && !fp->__pushed_back)
#else
  #error "Please port gnulib fseeko.c to your platform! Look at the code in fpurge.c, then report this to bug-gnulib."
#endif
    {
      /* We get here when an fflush() call immediately preceded this one.  We
         know there are no buffers.
         POSIX requires us to modify the file descriptor's position.
         But we cannot position beyond end of file here.  */
      off_t pos =
        lseek (fileno (fp),
               whence == SEEK_END && offset > 0 ? 0 : offset,
               whence);
      if (pos == -1)
        {
#if defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, MacOS X, Cygwin */
          fp_->_flags &= ~__SOFF;
#endif
          return -1;
        }

#if defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
      fp->_flags &= ~_IO_EOF_SEEN;
#elif defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, MacOS X, Cygwin */
# if defined __CYGWIN__
      /* fp_->_offset is typed as an integer.  */
      fp_->_offset = pos;
# else
      /* fp_->_offset is an fpos_t.  */
      {
        /* Use a union, since on NetBSD, the compilation flags
           determine whether fpos_t is typedef'd to off_t or a struct
           containing a single off_t member.  */
        union
          {
            fpos_t f;
            off_t o;
          } u;
        u.o = pos;
        fp_->_offset = u.f;
      }
# endif
      fp_->_flags |= __SOFF;
      fp_->_flags &= ~__SEOF;
#elif defined __EMX__               /* emx+gcc */
      fp->_flags &= ~_IOEOF;
#elif defined _IOERR                /* AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw */
      fp->_flag &= ~_IOEOF;
#elif defined __MINT__              /* Atari FreeMiNT */
      fp->__offset = pos;
      fp->__eof = 0;
#endif
      /* If we were not requested to position beyond end of file, we're
         done.  */
      if (!(whence == SEEK_END && offset > 0))
        return 0;
    }
  return fseeko (fp, offset, whence);
}