stdio/freopen.c

   1 /* Copyright (C) 1991, 1994, 1995 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 Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 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 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <errno.h>
  21 #include <stdio.h>
  22
  23
  24 /* Defined in fopen.c.  */
  25 extern int __getmode __P ((const char *, __io_mode *));
  26
  27 /* Defined in sysd-stdio.c.  */
  28 extern int __stdio_reopen __P ((const char *filename, __io_mode mode,
  29                                 PTR *cookieptr, __io_close_fn closefn));
  30
  31 /* Replace STREAM, opening it on FILENAME.  */
  32 FILE *
  33 DEFUN(freopen, (filename, mode, stream),
  34       CONST char *filename AND CONST char *mode AND register FILE *stream)
  35 {
  36   __io_mode m;
  37   PTR cookie;
  38
  39   if (!__getmode (mode, &m))
  40     {
  41       (void) fclose (stream);
  42       errno = EINVAL;
  43       return NULL;
  44     }
  45
  46   if (stream->__mode.__write)
  47     /* Flush the stream.  */
  48     (void) fflush (stream);
  49
  50   /* Open the file, attempting to preserve the old cookie value.  */
  51   cookie = stream->__cookie;
  52   if (__stdio_reopen (filename, m, &cookie,
  53                       stream->__seen ?
  54                       stream->__io_funcs.__close :
  55                       __stdio_close))
  56     {
  57       int save = errno;
  58       (void) fclose (stream);
  59       errno = save;
  60       return NULL;
  61     }
  62
  63   /* Close the stream, first disabling its cookie close function because
  64      __stdio_reopen has already dealt with closing the old cookie.  */
  65   stream->__seen = 1;           /* It might have no functions yet.  */
  66   stream->__io_funcs.__close = NULL;
  67   (void) fclose (stream);
  68
  69   stream->__magic = _IOMAGIC;
  70   stream->__cookie = cookie;
  71   stream->__mode = m;
  72
  73   return stream;
  74 }