sysdeps/unix/sysv/linux/pread64.c

   1 /* Copyright (C) 1997, 1998, 1999, 2000 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <endian.h>
  22 #include <unistd.h>
  23
  24 #include <sysdep.h>
  25 #include <sys/syscall.h>
  26
  27 #include "kernel-features.h"
  28
  29 #if defined __NR_pread || __ASSUME_PREAD_SYSCALL > 0
  30
  31 extern ssize_t __syscall_pread (int fd, void *buf, size_t count,
  32                                 off_t offset_hi, off_t offset_lo);
  33
  34 # if __ASSUME_PREAD_SYSCALL == 0
  35 static ssize_t __emulate_pread64 (int fd, void *buf, size_t count,
  36                                   off64_t offset) internal_function;
  37 # endif
  38
  39
  40 ssize_t
  41 __libc_pread64 (fd, buf, count, offset)
  42      int fd;
  43      void *buf;
  44      size_t count;
  45      off64_t offset;
  46 {
  47   ssize_t result;
  48
  49   /* First try the syscall.  */
  50 # if __BYTE_ORDER == __LITTLE_ENDIAN
  51   result = INLINE_SYSCALL (pread, 5, fd, buf, count,
  52                            (off_t) (offset & 0xffffffff),
  53                            (off_t) (offset >> 32));
  54 # elif __BYTE_ORDER == __BIG_ENDIAN
  55   result = INLINE_SYSCALL (pread, 5, fd, buf, count,
  56                            (off_t) (offset >> 32),
  57                            (off_t) (offset & 0xffffffff));
  58 # endif
  59
  60 # if __ASSUME_PREAD_SYSCALL == 0
  61   if (result == -1 && errno == ENOSYS)
  62     /* No system call available.  Use the emulation.  */
  63     result = __emulate_pread64 (fd, buf, count, offset);
  64 # endif
  65
  66   return result;
  67 }
  68
  69 weak_alias (__libc_pread64, __pread64)
  70 weak_alias (__libc_pread64, pread64)
  71
  72 # define __libc_pread64(fd, buf, count, offset) \
  73      static internal_function __emulate_pread64 (fd, buf, count, offset)
  74 #endif
  75
  76 # if __ASSUME_PREAD_SYSCALL == 0
  77 # include <sysdeps/posix/pread64.c>
  78 #endif