sysdeps/i386/bits/byteswap.h

   1 /* Macros to swap the order of bytes in integer values.
   2    Copyright (C) 1997, 1998, 2000, 2002, 2003, 2006, 2007, 2008
   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) & 0xff) | (((x) & 0xff) << 8))
  31
  32 #ifdef __GNUC__
  33 # if __GNUC__ >= 2
  34 #  define __bswap_16(x) \
  35      (__extension__                                                           \
  36       ({ register unsigned short int __v, __x = (x);                          \
  37          if (__builtin_constant_p (__x))                                      \
  38            __v = __bswap_constant_16 (__x);                                   \
  39          else                                                                 \
  40            __asm__ ("rorw $8, %w0"                                            \
  41                     : "=r" (__v)                                              \
  42                     : "0" (__x)                                               \
  43                     : "cc");                                                  \
  44          __v; }))
  45 # else
  46 /* This is better than nothing.  */
  47 #  define __bswap_16(x) \
  48      (__extension__                                                           \
  49       ({ register unsigned short int __x = (x); __bswap_constant_16 (__x); }))
  50 # endif
  51 #else
  52 static __inline unsigned short int
  53 __bswap_16 (unsigned short int __bsx)
  54 {
  55   return __bswap_constant_16 (__bsx);
  56 }
  57 #endif
  58
  59 /* Swap bytes in 32 bit value.  */
  60 #define __bswap_constant_32(x) \
  61      ((((x) & 0xff000000) >> 24) | (((x) & 0x00ff0000) >>  8) |               \
  62       (((x) & 0x0000ff00) <<  8) | (((x) & 0x000000ff) << 24))
  63
  64 #ifdef __GNUC__
  65 # if __GNUC__ >= 2
  66 /* To swap the bytes in a word the i486 processors and up provide the
  67    `bswap' opcode.  On i386 we have to use three instructions.  */
  68 #  if !defined __i486__ && !defined __pentium__ && !defined __pentiumpro__ \
  69       && !defined __pentium4__ && !defined __k8__ && !defined __athlon__ \
  70       && !defined __k6__ && !defined __nocona__ && !defined __core2__ \
  71       && !defined __geode__ && !defined __amdfam10__
  72 #   define __bswap_32(x)                                                      \
  73      (__extension__                                                           \
  74       ({ register unsigned int __v, __x = (x);                                \
  75          if (__builtin_constant_p (__x))                                      \
  76            __v = __bswap_constant_32 (__x);                                   \
  77          else                                                                 \
  78            __asm__ ("rorw $8, %w0;"                                           \
  79                     "rorl $16, %0;"                                           \
  80                     "rorw $8, %w0"                                            \
  81                     : "=r" (__v)                                              \
  82                     : "0" (__x)                                               \
  83                     : "cc");                                                  \
  84          __v; }))
  85 #  else
  86 #   define __bswap_32(x) \
  87      (__extension__                                                           \
  88       ({ register unsigned int __v, __x = (x);                                \
  89          if (__builtin_constant_p (__x))                                      \
  90            __v = __bswap_constant_32 (__x);                                   \
  91          else                                                                 \
  92            __asm__ ("bswap %0" : "=r" (__v) : "0" (__x));                     \
  93          __v; }))
  94 #  endif
  95 # else
  96 #  define __bswap_32(x) \
  97      (__extension__                                                           \
  98       ({ register unsigned int __x = (x); __bswap_constant_32 (__x); }))
  99 # endif
 100 #else
 101 static __inline unsigned int
 102 __bswap_32 (unsigned int __bsx)
 103 {
 104   return __bswap_constant_32 (__bsx);
 105 }
 106 #endif
 107
 108
 109 #if defined __GNUC__ && __GNUC__ >= 2
 110 /* Swap bytes in 64 bit value.  */
 111 #define __bswap_constant_64(x) \
 112      ((((x) & 0xff00000000000000ull) >> 56)                                   \
 113       | (((x) & 0x00ff000000000000ull) >> 40)                                 \
 114       | (((x) & 0x0000ff0000000000ull) >> 24)                                 \
 115       | (((x) & 0x000000ff00000000ull) >> 8)                                  \
 116       | (((x) & 0x00000000ff000000ull) << 8)                                  \
 117       | (((x) & 0x0000000000ff0000ull) << 24)                                 \
 118       | (((x) & 0x000000000000ff00ull) << 40)                                 \
 119       | (((x) & 0x00000000000000ffull) << 56))
 120
 121 # define __bswap_64(x) \
 122      (__extension__                                                           \
 123       ({ union { __extension__ unsigned long long int __ll;                   \
 124                  unsigned long int __l[2]; } __w, __r;                        \
 125          if (__builtin_constant_p (x))                                        \
 126            __r.__ll = __bswap_constant_64 (x);                                \
 127          else                                                                 \
 128            {                                                                  \
 129              __w.__ll = (x);                                                  \
 130              __r.__l[0] = __bswap_32 (__w.__l[1]);                            \
 131              __r.__l[1] = __bswap_32 (__w.__l[0]);                            \
 132            }                                                                  \
 133          __r.__ll; }))
 134 #endif
 135
 136 #endif /* _BITS_BYTESWAP_H */