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/* Read block from given position in file without changing file pointer.
POSIX version.
Copyright (C) 1997, 1998 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
The GNU C Library 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <errno.h>
#include <unistd.h>
ssize_t
__pread (int fd, void *buf, size_t nbyte, off_t offset)
{
/* Since we must not change the file pointer preserve the value so that
we can restore it later. */
int save_errno;
ssize_t result;
off_t old_offset = __lseek (fd, 0, SEEK_CUR);
if (old_offset == (off_t) -1)
return -1;
/* Set to wanted position. */
if (__lseek (fd, offset, SEEK_SET) == (off_t) -1)
return -1;
/* Write out the data. */
result = __read (fd, buf, nbyte);
/* Now we have to restore the position. If this fails we have to
return this as an error. But if the writing also failed we
return this error. */
save_errno = errno;
if (__lseek (fd, old_offset, SEEK_SET) == (off_t) -1)
{
if (result == -1)
__set_errno (save_errno);
return -1;
}
__set_errno (save_errno);
return result;
}
#ifndef __pread
weak_alias (__pread, pread)
#endif
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