bits/byteswap.h

   1 /* Macros to swap the order of bytes in integer values.
   2    Copyright (C) 1997,1998,2000-2002,2005,2008,2011
   3    Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #if !defined _BYTESWAP_H && !defined _NETINET_IN_H && !defined _ENDIAN_H
  22 # error "Never use <bits/byteswap.h> directly; include <byteswap.h> instead."
  23 #endif
  24
  25 #ifndef _BITS_BYTESWAP_H
  26 #define _BITS_BYTESWAP_H 1
  27
  28 /* Swap bytes in 16 bit value.  */
  29 #define __bswap_constant_16(x) \
  30      ((((x) >> 8) & 0xffu) | (((x) & 0xffu) << 8))
  31
  32 #ifdef __GNUC__
  33 # define __bswap_16(x) \
  34     (__extension__                                                            \
  35      ({ unsigned short int __bsx = (x); __bswap_constant_16 (__bsx); }))
  36 #else
  37 static __inline unsigned short int
  38 __bswap_16 (unsigned short int __bsx)
  39 {
  40   return __bswap_constant_16 (__bsx);
  41 }
  42 #endif
  43
  44 /* Swap bytes in 32 bit value.  */
  45 #define __bswap_constant_32(x) \
  46      ((((x) & 0xff000000u) >> 24) | (((x) & 0x00ff0000u) >>  8) |             \
  47       (((x) & 0x0000ff00u) <<  8) | (((x) & 0x000000ffu) << 24))
  48
  49 #ifdef __GNUC__
  50 # define __bswap_32(x) \
  51   (__extension__                                                              \
  52    ({ register unsigned int __bsx = (x); __bswap_constant_32 (__bsx); }))
  53 #else
  54 static __inline unsigned int
  55 __bswap_32 (unsigned int __bsx)
  56 {
  57   return __bswap_constant_32 (__bsx);
  58 }
  59 #endif
  60
  61 #if defined __GNUC__ && __GNUC__ >= 2
  62 /* Swap bytes in 64 bit value.  */
  63 # define __bswap_constant_64(x) \
  64      (__extension__ ((((x) & 0xff00000000000000ull) >> 56)                    \
  65                      | (((x) & 0x00ff000000000000ull) >> 40)                  \
  66                      | (((x) & 0x0000ff0000000000ull) >> 24)                  \
  67                      | (((x) & 0x000000ff00000000ull) >> 8)                   \
  68                      | (((x) & 0x00000000ff000000ull) << 8)                   \
  69                      | (((x) & 0x0000000000ff0000ull) << 24)                  \
  70                      | (((x) & 0x000000000000ff00ull) << 40)                  \
  71                      | (((x) & 0x00000000000000ffull) << 56)))
  72
  73 # define __bswap_64(x) \
  74      (__extension__                                                           \
  75       ({ union { __extension__ unsigned long long int __ll;                   \
  76                  unsigned int __l[2]; } __w, __r;                             \
  77          if (__builtin_constant_p (x))                                        \
  78            __r.__ll = __bswap_constant_64 (x);                                \
  79          else                                                                 \
  80            {                                                                  \
  81              __w.__ll = (x);                                                  \
  82              __r.__l[0] = __bswap_32 (__w.__l[1]);                            \
  83              __r.__l[1] = __bswap_32 (__w.__l[0]);                            \
  84            }                                                                  \
  85          __r.__ll; }))
  86 #endif
  87
  88 #endif /* _BITS_BYTESWAP_H */