bits/byteswap.h

   1 /* Macros to swap the order of bytes in integer values.
   2    Copyright (C) 1997, 1998, 2000, 2001 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 #ifdef __GNUC__
  26 # define __bswap_16(x) \
  27     (__extension__                                                            \
  28      ({ unsigned short int __bsx = (x);                                       \
  29         ((((__bsx) >> 8) & 0xff) | (((__bsx) & 0xff) << 8)); }))
  30 #else
  31 static __inline unsigned short int
  32 __bswap_16 (unsigned short int __bsx)
  33 {
  34   return ((((__bsx) >> 8) & 0xff) | (((__bsx) & 0xff) << 8));
  35 }
  36 #endif
  37
  38 /* Swap bytes in 32 bit value.  */
  39 #ifdef __GNUC__
  40 # define __bswap_32(x) \
  41     (__extension__                                                            \
  42      ({ unsigned int __bsx = (x);                                             \
  43         ((((__bsx) & 0xff000000) >> 24) | (((__bsx) & 0x00ff0000) >>  8) |    \
  44          (((__bsx) & 0x0000ff00) <<  8) | (((__bsx) & 0x000000ff) << 24)); }))
  45 #else
  46 static __inline unsigned int
  47 __bswap_32 (unsigned int __bsx)
  48 {
  49   return ((((__bsx) & 0xff000000) >> 24) | (((__bsx) & 0x00ff0000) >>  8) |
  50           (((__bsx) & 0x0000ff00) <<  8) | (((__bsx) & 0x000000ff) << 24));
  51 }
  52 #endif
  53
  54 #if defined __GNUC__ && __GNUC__ >= 2
  55 /* Swap bytes in 64 bit value.  */
  56 # define __bswap_constant_64(x) \
  57      ((((x) & 0xff00000000000000ull) >> 56)                                   \
  58       | (((x) & 0x00ff000000000000ull) >> 40)                                 \
  59       | (((x) & 0x0000ff0000000000ull) >> 24)                                 \
  60       | (((x) & 0x000000ff00000000ull) >> 8)                                  \
  61       | (((x) & 0x00000000ff000000ull) << 8)                                  \
  62       | (((x) & 0x0000000000ff0000ull) << 24)                                 \
  63       | (((x) & 0x000000000000ff00ull) << 40)                                 \
  64       | (((x) & 0x00000000000000ffull) << 56))
  65
  66 # define __bswap_64(x) \
  67      (__extension__                                                           \
  68       ({ union { __extension__ unsigned long long int __ll;                   \
  69                  unsigned int __l[2]; } __w, __r;                             \
  70          if (__builtin_constant_p (x))                                        \
  71            __r.__ll = __bswap_constant_64 (x);                                \
  72          else                                                                 \
  73            {                                                                  \
  74              __w.__ll = (x);                                                  \
  75              __r.__l[0] = __bswap_32 (__w.__l[1]);                            \
  76              __r.__l[1] = __bswap_32 (__w.__l[0]);                            \
  77            }                                                                  \
  78          __r.__ll; }))
  79 #endif