libio/ioseekoff.c

   1 /* Copyright (C) 1993-2017 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, see
  16    <http://www.gnu.org/licenses/>.
  17
  18    As a special exception, if you link the code in this file with
  19    files compiled with a GNU compiler to produce an executable,
  20    that does not cause the resulting executable to be covered by
  21    the GNU Lesser General Public License.  This exception does not
  22    however invalidate any other reasons why the executable file
  23    might be covered by the GNU Lesser General Public License.
  24    This exception applies to code released by its copyright holders
  25    in files containing the exception.  */
  26
  27 #include <stdlib.h>
  28 #include <libioP.h>
  29 #include <errno.h>
  30
  31 _IO_off64_t
  32 _IO_seekoff_unlocked (_IO_FILE *fp, _IO_off64_t offset, int dir, int mode)
  33 {
  34   if (dir != _IO_seek_cur && dir != _IO_seek_set && dir != _IO_seek_end)
  35     {
  36       __set_errno (EINVAL);
  37       return EOF;
  38     }
  39
  40   /* If we have a backup buffer, get rid of it, since the __seekoff
  41      callback may not know to do the right thing about it.
  42      This may be over-kill, but it'll do for now. TODO */
  43   if (mode != 0 && ((_IO_fwide (fp, 0) < 0 && _IO_have_backup (fp))
  44                     || (_IO_fwide (fp, 0) > 0 && _IO_have_wbackup (fp))))
  45     {
  46       if (dir == _IO_seek_cur && _IO_in_backup (fp))
  47         {
  48           if (_IO_vtable_offset (fp) != 0 || fp->_mode <= 0)
  49             offset -= fp->_IO_read_end - fp->_IO_read_ptr;
  50           else
  51             abort ();
  52         }
  53       if (_IO_fwide (fp, 0) < 0)
  54         _IO_free_backup_area (fp);
  55       else
  56         _IO_free_wbackup_area (fp);
  57     }
  58
  59   return _IO_SEEKOFF (fp, offset, dir, mode);
  60 }
  61
  62
  63 _IO_off64_t
  64 _IO_seekoff (_IO_FILE *fp, _IO_off64_t offset, int dir, int mode)
  65 {
  66   _IO_off64_t retval;
  67
  68   _IO_acquire_lock (fp);
  69   retval = _IO_seekoff_unlocked (fp, offset, dir, mode);
  70   _IO_release_lock (fp);
  71   return retval;
  72 }