/* An ftello() function that works around platform bugs.

   Copyright (C) 2007, 2009-2020 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify

   it under the terms of the GNU Lesser General Public License as published by

   the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License

   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */

#include <stdio.h>

/* Get lseek.  */

#include <unistd.h>

#include "stdio-impl.h"

off_t

ftello (FILE *fp)

#undef ftello

#if !HAVE_FTELLO

# undef ftell

# define ftello ftell

#endif

#if _GL_WINDOWS_64_BIT_OFF_T

# undef ftello

# if HAVE__FTELLI64 /* msvc, mingw64 */

#  define ftello _ftelli64

# else /* mingw */

#  define ftello ftello64

# endif

#endif

{

#if LSEEK_PIPE_BROKEN

  /* mingw gives bogus answers rather than failure on non-seekable files.  */

  if (lseek (fileno (fp), 0, SEEK_CUR) == -1)

    return -1;

#endif

#if FTELLO_BROKEN_AFTER_SWITCHING_FROM_READ_TO_WRITE /* Solaris */

  /* The Solaris stdio leaves the _IOREAD flag set after reading from a file

     reaches EOF and the program then starts writing to the file.  ftello

     gets confused by this.  */

  if (fp_->_flag & _IOWRT)

    {

      off_t pos;

      /* Call ftello nevertheless, for the side effects that it does on fp.  */

      ftello (fp);

      /* Compute the file position ourselves.  */

      pos = lseek (fileno (fp), (off_t) 0, SEEK_CUR);

      if (pos >= 0)

        {

          if ((fp_->_flag & _IONBF) == 0 && fp_->_base != NULL)

            pos += fp_->_ptr - fp_->_base;

        }

      return pos;

    }

#endif

#if defined __SL64 && defined __SCLE /* Cygwin */

  if ((fp->_flags & __SL64) == 0)

    {

      /* Cygwin 1.5.0 through 1.5.24 failed to open stdin in 64-bit

         mode; but has an ftello that requires 64-bit mode.  */

      FILE *tmp = fopen ("/dev/null", "r");

      if (!tmp)

        return -1;

      fp->_flags |= __SL64;

      fp->_seek64 = tmp->_seek64;

      fclose (tmp);

    }

#endif

  return ftello (fp);

}