libio/ftello.c

   1 /* Copyright (C) 1993, 1995, 1996, 1997, 1998 Free Software Foundation, Inc.
   2    This file is part of the GNU IO Library.
   3
   4    This library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU General Public License as
   6    published by the Free Software Foundation; either version 2, or (at
   7    your option) any later version.
   8
   9    This library is distributed in the hope that it will be useful, but
  10    WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this library; see the file COPYING.  If not, write to
  16    the Free Software Foundation, 59 Temple Place - Suite 330, Boston,
  17    MA 02111-1307, USA.
  18
  19    As a special exception, if you link this library with files
  20    compiled with a GNU compiler to produce an executable, this does
  21    not cause the resulting executable to be covered by the GNU General
  22    Public License.  This exception does not however invalidate any
  23    other reasons why the executable file might be covered by the GNU
  24    General Public License.  */
  25
  26 #include <stdio.h>
  27 #include <libioP.h>
  28 #include <errno.h>
  29
  30
  31 off_t
  32 ftello (fp)
  33      _IO_FILE *fp;
  34 {
  35   _IO_pos_t pos;
  36   CHECK_FILE (fp, -1L);
  37   _IO_cleanup_region_start ((void (*) __P ((void *))) _IO_funlockfile, fp);
  38   _IO_flockfile (fp);
  39   pos = _IO_seekoff (fp, 0, _IO_seek_cur, 0);
  40   if (_IO_in_backup (fp))
  41     pos -= fp->_IO_save_end - fp->_IO_save_base;
  42   _IO_funlockfile (fp);
  43   _IO_cleanup_region_end (0);
  44   if (pos == _IO_pos_BAD)
  45     {
  46 #ifdef EIO
  47       if (errno == 0)
  48         __set_errno (EIO);
  49 #endif
  50       return -1L;
  51     }
  52   return _IO_pos_as_off (pos);
  53 }