posix/pread.c

   1 /* Copyright (C) 1991-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <unistd.h>
  20
  21 /* Read NBYTES into BUF from FD at the given position OFFSET without
  22    changing the file pointer.  Return the number read or -1.  */
  23 ssize_t
  24 __libc_pread (int fd, void *buf, size_t nbytes, off_t offset)
  25 {
  26   if (nbytes == 0)
  27     return 0;
  28   if (fd < 0)
  29     {
  30       __set_errno (EBADF);
  31       return -1;
  32     }
  33   if (buf == NULL || offset < 0)
  34     {
  35       __set_errno (EINVAL);
  36       return -1;
  37     }
  38
  39   __set_errno (ENOSYS);
  40   return -1;
  41 }
  42 strong_alias (__libc_pread, __pread)
  43 weak_alias (__libc_pread, pread)
  44 stub_warning (pread)