bits/byteswap.h

   1 /* Macros to swap the order of bytes in integer values.
   2    Copyright (C) 1997, 1998, 2000, 2001, 2002 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 Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    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 #ifndef _BITS_BYTESWAP_H
  25 #define _BITS_BYTESWAP_H 1
  26
  27 /* Swap bytes in 16 bit value.  */
  28 #ifdef __GNUC__
  29 # define __bswap_16(x) \
  30     (__extension__                                                            \
  31      ({ unsigned short int __bsx = (x);                                       \
  32         ((((__bsx) >> 8) & 0xff) | (((__bsx) & 0xff) << 8)); }))
  33 #else
  34 static __inline unsigned short int
  35 __bswap_16 (unsigned short int __bsx)
  36 {
  37   return ((((__bsx) >> 8) & 0xff) | (((__bsx) & 0xff) << 8));
  38 }
  39 #endif
  40
  41 /* Swap bytes in 32 bit value.  */
  42 #ifdef __GNUC__
  43 # define __bswap_32(x) \
  44     (__extension__                                                            \
  45      ({ unsigned int __bsx = (x);                                             \
  46         ((((__bsx) & 0xff000000) >> 24) | (((__bsx) & 0x00ff0000) >>  8) |    \
  47          (((__bsx) & 0x0000ff00) <<  8) | (((__bsx) & 0x000000ff) << 24)); }))
  48 #else
  49 static __inline unsigned int
  50 __bswap_32 (unsigned int __bsx)
  51 {
  52   return ((((__bsx) & 0xff000000) >> 24) | (((__bsx) & 0x00ff0000) >>  8) |
  53           (((__bsx) & 0x0000ff00) <<  8) | (((__bsx) & 0x000000ff) << 24));
  54 }
  55 #endif
  56
  57 #if defined __GNUC__ && __GNUC__ >= 2
  58 /* Swap bytes in 64 bit value.  */
  59 # define __bswap_constant_64(x) \
  60      ((((x) & 0xff00000000000000ull) >> 56)                                   \
  61       | (((x) & 0x00ff000000000000ull) >> 40)                                 \
  62       | (((x) & 0x0000ff0000000000ull) >> 24)                                 \
  63       | (((x) & 0x000000ff00000000ull) >> 8)                                  \
  64       | (((x) & 0x00000000ff000000ull) << 8)                                  \
  65       | (((x) & 0x0000000000ff0000ull) << 24)                                 \
  66       | (((x) & 0x000000000000ff00ull) << 40)                                 \
  67       | (((x) & 0x00000000000000ffull) << 56))
  68
  69 # define __bswap_64(x) \
  70      (__extension__                                                           \
  71       ({ union { __extension__ unsigned long long int __ll;                   \
  72                  unsigned int __l[2]; } __w, __r;                             \
  73          if (__builtin_constant_p (x))                                        \
  74            __r.__ll = __bswap_constant_64 (x);                                \
  75          else                                                                 \
  76            {                                                                  \
  77              __w.__ll = (x);                                                  \
  78              __r.__l[0] = __bswap_32 (__w.__l[1]);                            \
  79              __r.__l[1] = __bswap_32 (__w.__l[0]);                            \
  80            }                                                                  \
  81          __r.__ll; }))
  82 #endif
  83
  84 #endif /* _BITS_BYTESWAP_H */