libio/ioseekoff.c

   1 /* Copyright (C) 1993, 1997, 1998, 1999, 2001 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.
  18
  19    As a special exception, if you link the code in this file with
  20    files compiled with a GNU compiler to produce an executable,
  21    that does not cause the resulting executable to be covered by
  22    the GNU Lesser General Public License.  This exception does not
  23    however invalidate any other reasons why the executable file
  24    might be covered by the GNU Lesser General Public License.
  25    This exception applies to code released by its copyright holders
  26    in files containing the exception.  */
  27
  28 #include <stdlib.h>
  29 #include <libioP.h>
  30 #include <errno.h>
  31 #ifndef errno
  32 extern int errno;
  33 #endif
  34 #ifndef __set_errno
  35 # define __set_errno(Val) errno = (Val)
  36 #endif
  37
  38 _IO_off64_t
  39 _IO_seekoff (fp, offset, dir, mode)
  40      _IO_FILE *fp;
  41      _IO_off64_t offset;
  42      int dir;
  43      int mode;
  44 {
  45   _IO_off64_t retval;
  46
  47   if (dir != _IO_seek_cur && dir != _IO_seek_set && dir != _IO_seek_end)
  48     {
  49       __set_errno (EINVAL);
  50       return EOF;
  51     }
  52
  53   /* If we have a backup buffer, get rid of it, since the __seekoff
  54      callback may not know to do the right thing about it.
  55      This may be over-kill, but it'll do for now. TODO */
  56   _IO_cleanup_region_start ((void (*) __P ((void *))) _IO_funlockfile, fp);
  57   _IO_flockfile (fp);
  58
  59   if (mode != 0 && _IO_have_backup (fp))
  60     {
  61       if (dir == _IO_seek_cur && _IO_in_backup (fp))
  62         {
  63           if (fp->_vtable_offset != 0 || fp->_mode <= 0)
  64             offset -= fp->_IO_read_end - fp->_IO_read_ptr;
  65           else
  66             abort ();
  67         }
  68       _IO_free_backup_area (fp);
  69     }
  70
  71   retval = _IO_SEEKOFF (fp, offset, dir, mode);
  72
  73   _IO_funlockfile (fp);
  74   _IO_cleanup_region_end (0);
  75   return retval;
  76 }