/* Read block from given position in file without changing file pointer.

   POSIX version.

   Copyright (C) 1997-2018 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 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.

   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

   Lesser General Public License for more details.

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

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <errno.h>

#include <unistd.h>

/* Note: This implementation of pread64 is not multithread-safe.  */

ssize_t

__libc_pread64 (int fd, void *buf, size_t nbyte, off64_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;

  off64_t old_offset = __libc_lseek64 (fd, 0, SEEK_CUR);

  if (old_offset == (off64_t) -1)

    return -1;

  /* Set to wanted position.  */

  if (__libc_lseek64 (fd, offset, SEEK_SET) == (off64_t) -1)

    return -1;

  /* Write out the data.  */

  result = __libc_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 (__libc_lseek64 (fd, old_offset, SEEK_SET) == (off64_t) -1)

    {

      if (result == -1)

	__set_errno (save_errno);

      return -1;

    }

  __set_errno (save_errno);

  return result;

}

#ifndef __libc_pread64

weak_alias (__libc_pread64, __pread64)

libc_hidden_weak (__pread64)

weak_alias (__libc_pread64, pread64)

#endif