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 #include <features.h>
  27
  28 /* Swap bytes in 16 bit value.  */
  29 #define __bswap_constant_16(x) \
  30      ((((x) >> 8) & 0xffu) | (((x) & 0xffu) << 8))
  31
  32 /* Get __bswap_16.  */
  33 #include <bits/byteswap-16.h>
  34
  35 /* Swap bytes in 32 bit value.  */
  36 #define __bswap_constant_32(x) \
  37      ((((x) & 0xff000000u) >> 24) | (((x) & 0x00ff0000u) >>  8) |             \
  38       (((x) & 0x0000ff00u) <<  8) | (((x) & 0x000000ffu) << 24))
  39
  40 #ifdef __GNUC__
  41 # if __GNUC_PREREQ (4, 2)
  42 static __inline unsigned int
  43 __bswap_32 (unsigned int __bsx)
  44 {
  45   return __builtin_bswap32 (__bsx);
  46 }
  47 # else
  48 #  define __bswap_32(x) \
  49   (__extension__                                                              \
  50    ({ register unsigned int __bsx = (x); __bswap_constant_32 (__bsx); }))
  51 # endif
  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 /* Swap bytes in 64 bit value.  */
  61 #if __GNUC_PREREQ (2, 0)
  62 # define __bswap_constant_64(x) \
  63      (__extension__ ((((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 # if __GNUC_PREREQ (4, 2)
  73 static __inline unsigned long long int
  74 __bswap_64 (unsigned long long int __bsx)
  75 {
  76   return __builtin_bswap64 (__bsx);
  77 }
  78 # else
  79 #  define __bswap_64(x) \
  80      (__extension__                                                           \
  81       ({ union { __extension__ unsigned long long int __ll;                   \
  82                  unsigned int __l[2]; } __w, __r;                             \
  83          if (__builtin_constant_p (x))                                        \
  84            __r.__ll = __bswap_constant_64 (x);                                \
  85          else                                                                 \
  86            {                                                                  \
  87              __w.__ll = (x);                                                  \
  88              __r.__l[0] = __bswap_32 (__w.__l[1]);                            \
  89              __r.__l[1] = __bswap_32 (__w.__l[0]);                            \
  90            }                                                                  \
  91          __r.__ll; }))
  92 # endif
  93 #elif __GLIBC_HAVE_LONG_LONG
  94 # define __bswap_constant_64(x) \
  95      ((((x) & 0xff00000000000000ull) >> 56)                                   \
  96       | (((x) & 0x00ff000000000000ull) >> 40)                                 \
  97       | (((x) & 0x0000ff0000000000ull) >> 24)                                 \
  98       | (((x) & 0x000000ff00000000ull) >> 8)                                  \
  99       | (((x) & 0x00000000ff000000ull) << 8)                                  \
 100       | (((x) & 0x0000000000ff0000ull) << 24)                                 \
 101       | (((x) & 0x000000000000ff00ull) << 40)                                 \
 102       | (((x) & 0x00000000000000ffull) << 56))
 103
 104 static __inline unsigned long long int
 105 __bswap_64 (unsigned long long int __bsx)
 106 {
 107   return __bswap_constant_64 (__bsx);
 108 }
 109 #endif
 110
 111 #endif /* _BITS_BYTESWAP_H */