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/* An lseek() function that detects pipes.
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 <unistd.h>
#if defined _WIN32 && ! defined __CYGWIN__
/* Windows platforms. */
/* Get GetFileType. */
# include <windows.h>
/* Get _get_osfhandle. */
# if GNULIB_MSVC_NOTHROW
# include "msvc-nothrow.h"
# else
# include <io.h>
# endif
#else
# include <sys/stat.h>
#endif
#include <errno.h>
#undef lseek
off_t
rpl_lseek (int fd, off_t offset, int whence)
{
#if defined _WIN32 && ! defined __CYGWIN__
/* mingw lseek mistakenly succeeds on pipes, sockets, and terminals. */
HANDLE h = (HANDLE) _get_osfhandle (fd);
if (h == INVALID_HANDLE_VALUE)
{
errno = EBADF;
return -1;
}
if (GetFileType (h) != FILE_TYPE_DISK)
{
errno = ESPIPE;
return -1;
}
#elif defined __APPLE__ && defined __MACH__ && defined SEEK_DATA
if (whence == SEEK_DATA)
{
/* If OFFSET points to data, macOS lseek+SEEK_DATA returns the
start S of the first data region that begins *after* OFFSET,
where the region from OFFSET to S consists of possibly-empty
data followed by a possibly-empty hole. To work around this
portability glitch, check whether OFFSET is within data by
using lseek+SEEK_HOLE, and if so return to OFFSET by using
lseek+SEEK_SET. Also, contrary to the macOS documentation,
lseek+SEEK_HOLE can fail with ENXIO if there are no holes on
or after OFFSET. What a mess! */
off_t next_hole = lseek (fd, offset, SEEK_HOLE);
if (next_hole < 0)
return errno == ENXIO ? offset : next_hole;
if (next_hole != offset)
whence = SEEK_SET;
}
#else
/* BeOS lseek mistakenly succeeds on pipes... */
struct stat statbuf;
if (fstat (fd, &statbuf) < 0)
return -1;
if (!S_ISREG (statbuf.st_mode))
{
errno = ESPIPE;
return -1;
}
#endif
#if _GL_WINDOWS_64_BIT_OFF_T || (defined __MINGW32__ && defined _FILE_OFFSET_BITS && (_FILE_OFFSET_BITS == 64))
return _lseeki64 (fd, offset, whence);
#else
return lseek (fd, offset, whence);
#endif
}
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