bits/byteswap.h

   1 /* Macros to swap the order of bytes in integer values.
   2    Copyright (C) 1997 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   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 #if !defined _BYTESWAP_H && !defined _NETINET_IN_H
  21 # error "Never use <bits/byteswap.h> directly; include <byteswap.h> instead."
  22 #endif
  23
  24 /* Swap bytes in 16 bit value.  */
  25 #define __bswap_16(x) \
  26      ((((x) >> 8) & 0xff) | (((x) & 0xff) << 8))
  27
  28 /* Swap bytes in 32 bit value.  */
  29 #define __bswap_32(x) \
  30      ((((x) & 0xff000000) >> 24) | (((x) & 0x00ff0000) >>  8) |               \
  31       (((x) & 0x0000ff00) <<  8) | (((x) & 0x000000ff) << 24))
  32
  33 #if defined __GNUC__ && __GNUC__ >= 2
  34 /* Swap bytes in 64 bit value.  */
  35 # define __bswap_64(x) \
  36      ({ union { unsigned long long int __ll;                                  \
  37                 unsigned long int __l[2]; } __v, __r;                         \
  38         __v.__ll = (x);                                                       \
  39         __r.__l[0] = __bswap_32 (__v.__l[1]);                                 \
  40         __r.__l[1] = __bswap_32 (__v.__l[0]);                                 \
  41         __r.__ll; })
  42 #endif