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/* An ftello() function that works around platform bugs.
Copyright (C) 2007, 2009-2023 Free Software Foundation, Inc.
This file 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 file 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>
#include <errno.h>
#include "intprops.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 FTELLO_BROKEN_AFTER_UNGETC /* macOS >= 10.15 */
/* The system's ftello() is completely broken, because it calls __sflush,
which makes side effects on the stream. */
/* Handle non-seekable files first. */
if (fp->_file < 0 || fp->_seek == NULL)
{
errno = ESPIPE;
return -1;
}
/* Determine the current offset, ignoring buffered and pushed-back bytes. */
off_t pos;
if (fp->_flags & __SOFF)
pos = fp->_offset;
else
{
pos = fp->_seek (fp->_cookie, 0, SEEK_CUR);
if (pos < 0)
return -1;
if (fp->_flags & __SOPT)
{
fp->_offset = pos;
fp->_flags |= __SOFF;
}
}
if (fp->_flags & __SRD)
{
/* Now consider buffered and pushed-back bytes from ungetc. */
if (fp->_ub._base != NULL)
/* Considering the buffered bytes, we are at position
pos - fp->_ur.
Considering also the pushed-back bytes, we are at position
pos - fp->_ur - fp->_r. */
pos = pos - fp->_ur - fp->_r;
else
/* Considering the buffered bytes, we are at position
pos - fp->_r. */
pos = pos - fp->_r;
if (pos < 0)
{
errno = EIO;
return -1;
}
}
else if ((fp->_flags & __SWR) && fp->_p != NULL)
{
/* Consider the buffered bytes. */
off_t buffered = fp->_p - fp->_bf._base;
/* Compute pos + buffered, with overflow check. */
off_t sum;
if (! INT_ADD_OK (pos, buffered, &sum))
{
errno = EOVERFLOW;
return -1;
}
pos = sum;
}
return pos;
#else
# 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);
#endif
}
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