bits/byteswap.h

   1 /* Macros to swap the order of bytes in integer values.
   2    Copyright (C) 1997,1998,2000,2001,2002,2005 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 #define __bswap_constant_16(x) \
  29      ((((x) >> 8) & 0xffu) | (((x) & 0xffu) << 8))
  30
  31 #ifdef __GNUC__
  32 # define __bswap_16(x) \
  33     (__extension__                                                            \
  34      ({ unsigned short int __bsx = (x); __bswap_constant_16 (__bsx); }))
  35 #else
  36 static __inline unsigned short int
  37 __bswap_16 (unsigned short int __bsx)
  38 {
  39   return __bswap_constant_16 (__bsx);
  40 }
  41 #endif
  42
  43 /* Swap bytes in 32 bit value.  */
  44 #define __bswap_constant_32(x) \
  45      ((((x) & 0xff000000u) >> 24) | (((x) & 0x00ff0000u) >>  8) |             \
  46       (((x) & 0x0000ff00u) <<  8) | (((x) & 0x000000ffu) << 24))
  47
  48 #ifdef __GNUC__
  49 # define __bswap_32(x) \
  50   (__extension__                                                              \
  51    ({ register unsigned int __bsx = (x); __bswap_constant_32 (__bsx); }))
  52 #else
  53 static __inline unsigned int
  54 __bswap_32 (unsigned int __bsx)
  55 {
  56   return __bswap_constant_32 (__bsx);
  57 }
  58 #endif
  59
  60 #if defined __GNUC__ && __GNUC__ >= 2
  61 /* Swap bytes in 64 bit value.  */
  62 # define __bswap_constant_64(x) \
  63      ((((x) & 0xff00000000000000ull) >> 56)                                   \
  64       | (((x) & 0x00ff000000000000ull) >> 40)                                 \
  65       | (((x) & 0x0000ff0000000000ull) >> 24)                                 \
  66       | (((x) & 0x000000ff00000000ull) >> 8)                                  \
  67       | (((x) & 0x00000000ff000000ull) << 8)                                  \
  68       | (((x) & 0x0000000000ff0000ull) << 24)                                 \
  69       | (((x) & 0x000000000000ff00ull) << 40)                                 \
  70       | (((x) & 0x00000000000000ffull) << 56))
  71
  72 # define __bswap_64(x) \
  73      (__extension__                                                           \
  74       ({ union { __extension__ unsigned long long int __ll;                   \
  75                  unsigned int __l[2]; } __w, __r;                             \
  76          if (__builtin_constant_p (x))                                        \
  77            __r.__ll = __bswap_constant_64 (x);                                \
  78          else                                                                 \
  79            {                                                                  \
  80              __w.__ll = (x);                                                  \
  81              __r.__l[0] = __bswap_32 (__w.__l[1]);                            \
  82              __r.__l[1] = __bswap_32 (__w.__l[0]);                            \
  83            }                                                                  \
  84          __r.__ll; }))
  85 #endif
  86
  87 #endif /* _BITS_BYTESWAP_H */