/* Open a stream to a file.

   Copyright (C) 2007-2018 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 of the License, 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, see <https://www.gnu.org/licenses/>.  */

/* Written by Bruno Haible <bruno@clisp.org>, 2007.  */

/* If the user's config.h happens to include <stdio.h>, let it include only

   the system's <stdio.h> here, so that orig_freopen doesn't recurse to

   rpl_freopen.  */

#define _GL_ALREADY_INCLUDING_STDIO_H

#include <config.h>

/* Get the original definition of freopen.  It might be defined as a macro.  */

#include <stdio.h>

#undef _GL_ALREADY_INCLUDING_STDIO_H

#include <errno.h>

static FILE *

orig_freopen (const char *filename, const char *mode, FILE *stream)

{

  return freopen (filename, mode, stream);

}

/* Specification.  */

/* Write "stdio.h" here, not <stdio.h>, otherwise OSF/1 5.1 DTK cc eliminates

   this include because of the preliminary #include <stdio.h> above.  */

#include "stdio.h"

#include <fcntl.h>

#include <string.h>

#include <unistd.h>

FILE *

rpl_freopen (const char *filename, const char *mode, FILE *stream)

{

  FILE *result;

#if defined _WIN32 && ! defined __CYGWIN__

  char const *null_device = "NUL";

  if (filename && strcmp (filename, "/dev/null") == 0)

    filename = null_device;

#else

  char const *null_device = "/dev/null";

#endif

#ifdef __KLIBC__

  errno = 0;

#endif

  result = orig_freopen (filename, mode, stream);

  if (!result)

    {

#ifdef __KLIBC__

      /* On OS/2 kLIBC, freopen returns NULL even if it is successful

         if filename is NULL. */

      if (!filename && !errno)

        result = stream;

#endif

    }

  else if (filename)

    {

      int fd = fileno (result);

      if (dup2 (fd, fd) < 0 && errno == EBADF)

        {

          int nullfd = open (null_device, O_RDONLY | O_CLOEXEC);

          int err = 0;

          if (nullfd != fd)

            {

              if (dup2 (nullfd, fd) < 0)

                err = 1;

              close (nullfd);

            }

          if (!err)

            result = orig_freopen (filename, mode, result);

        }

    }

  return result;

}