bits/byteswap.h

   1 /* Macros to swap the order of bytes in integer values.
   2    Copyright (C) 1997-2012  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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #if !defined _BYTESWAP_H && !defined _NETINET_IN_H && !defined _ENDIAN_H
  20 # error "Never use <bits/byteswap.h> directly; include <byteswap.h> instead."
  21 #endif
  22
  23 #ifndef _BITS_BYTESWAP_H
  24 #define _BITS_BYTESWAP_H 1
  25
  26 /* Swap bytes in 16 bit value.  */
  27 #define __bswap_constant_16(x) \
  28      ((((x) >> 8) & 0xffu) | (((x) & 0xffu) << 8))
  29
  30 /* Get __bswap_16.  */
  31 #include <bits/byteswap-16.h>
  32
  33 /* Swap bytes in 32 bit value.  */
  34 #define __bswap_constant_32(x) \
  35      ((((x) & 0xff000000u) >> 24) | (((x) & 0x00ff0000u) >>  8) |             \
  36       (((x) & 0x0000ff00u) <<  8) | (((x) & 0x000000ffu) << 24))
  37
  38 #ifdef __GNUC__
  39 # define __bswap_32(x) \
  40   (__extension__                                                              \
  41    ({ register unsigned int __bsx = (x); __bswap_constant_32 (__bsx); }))
  42 #else
  43 static __inline unsigned int
  44 __bswap_32 (unsigned int __bsx)
  45 {
  46   return __bswap_constant_32 (__bsx);
  47 }
  48 #endif
  49
  50 #if defined __GNUC__ && __GNUC__ >= 2
  51 /* Swap bytes in 64 bit value.  */
  52 # define __bswap_constant_64(x) \
  53      (__extension__ ((((x) & 0xff00000000000000ull) >> 56)                    \
  54                      | (((x) & 0x00ff000000000000ull) >> 40)                  \
  55                      | (((x) & 0x0000ff0000000000ull) >> 24)                  \
  56                      | (((x) & 0x000000ff00000000ull) >> 8)                   \
  57                      | (((x) & 0x00000000ff000000ull) << 8)                   \
  58                      | (((x) & 0x0000000000ff0000ull) << 24)                  \
  59                      | (((x) & 0x000000000000ff00ull) << 40)                  \
  60                      | (((x) & 0x00000000000000ffull) << 56)))
  61
  62 # define __bswap_64(x) \
  63      (__extension__                                                           \
  64       ({ union { __extension__ unsigned long long int __ll;                   \
  65                  unsigned int __l[2]; } __w, __r;                             \
  66          if (__builtin_constant_p (x))                                        \
  67            __r.__ll = __bswap_constant_64 (x);                                \
  68          else                                                                 \
  69            {                                                                  \
  70              __w.__ll = (x);                                                  \
  71              __r.__l[0] = __bswap_32 (__w.__l[1]);                            \
  72              __r.__l[1] = __bswap_32 (__w.__l[0]);                            \
  73            }                                                                  \
  74          __r.__ll; }))
  75 #elif __GLIBC_HAVE_LONG_LONG
  76 # define __bswap_constant_64(x) \
  77      ((((x) & 0xff00000000000000ull) >> 56)                                   \
  78       | (((x) & 0x00ff000000000000ull) >> 40)                                 \
  79       | (((x) & 0x0000ff0000000000ull) >> 24)                                 \
  80       | (((x) & 0x000000ff00000000ull) >> 8)                                  \
  81       | (((x) & 0x00000000ff000000ull) << 8)                                  \
  82       | (((x) & 0x0000000000ff0000ull) << 24)                                 \
  83       | (((x) & 0x000000000000ff00ull) << 40)                                 \
  84       | (((x) & 0x00000000000000ffull) << 56))
  85
  86 static __inline unsigned long long int
  87 __bswap_64 (unsigned long long int __bsx)
  88 {
  89   return __bswap_constant_64 (__bsx);
  90 }
  91 #endif
  92
  93 #endif /* _BITS_BYTESWAP_H */