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, 2010
   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      ((unsigned short int) ((((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 = (unsigned short int) (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 = (unsigned short int) (x);          \
  50          __bswap_constant_16 (__x); }))
  51 # endif
  52 #else
  53 static __inline unsigned short int
  54 __bswap_16 (unsigned short int __bsx)
  55 {
  56   return __bswap_constant_16 (__bsx);
  57 }
  58 #endif
  59
  60 /* Swap bytes in 32 bit value.  */
  61 #define __bswap_constant_32(x) \
  62      ((((x) & 0xff000000) >> 24) | (((x) & 0x00ff0000) >>  8) |               \
  63       (((x) & 0x0000ff00) <<  8) | (((x) & 0x000000ff) << 24))
  64
  65 #ifdef __GNUC__
  66 # if __GNUC__ >= 2
  67 /* To swap the bytes in a word the i486 processors and up provide the
  68    `bswap' opcode.  On i386 we have to use three instructions.  */
  69 #  if !defined __i486__ && !defined __pentium__ && !defined __pentiumpro__ \
  70       && !defined __pentium4__ && !defined __k8__ && !defined __athlon__ \
  71       && !defined __k6__ && !defined __nocona__ && !defined __core2__ \
  72       && !defined __geode__ && !defined __amdfam10__
  73 #   define __bswap_32(x)                                                      \
  74      (__extension__                                                           \
  75       ({ register unsigned int __v, __x = (x);                                \
  76          if (__builtin_constant_p (__x))                                      \
  77            __v = __bswap_constant_32 (__x);                                   \
  78          else                                                                 \
  79            __asm__ ("rorw $8, %w0;"                                           \
  80                     "rorl $16, %0;"                                           \
  81                     "rorw $8, %w0"                                            \
  82                     : "=r" (__v)                                              \
  83                     : "0" (__x)                                               \
  84                     : "cc");                                                  \
  85          __v; }))
  86 #  else
  87 #   define __bswap_32(x) \
  88      (__extension__                                                           \
  89       ({ register unsigned int __v, __x = (x);                                \
  90          if (__builtin_constant_p (__x))                                      \
  91            __v = __bswap_constant_32 (__x);                                   \
  92          else                                                                 \
  93            __asm__ ("bswap %0" : "=r" (__v) : "0" (__x));                     \
  94          __v; }))
  95 #  endif
  96 # else
  97 #  define __bswap_32(x) \
  98      (__extension__                                                           \
  99       ({ register unsigned int __x = (x); __bswap_constant_32 (__x); }))
 100 # endif
 101 #else
 102 static __inline unsigned int
 103 __bswap_32 (unsigned int __bsx)
 104 {
 105   return __bswap_constant_32 (__bsx);
 106 }
 107 #endif
 108
 109
 110 #if defined __GNUC__ && __GNUC__ >= 2
 111 /* Swap bytes in 64 bit value.  */
 112 #define __bswap_constant_64(x) \
 113      ((((x) & 0xff00000000000000ull) >> 56)                                   \
 114       | (((x) & 0x00ff000000000000ull) >> 40)                                 \
 115       | (((x) & 0x0000ff0000000000ull) >> 24)                                 \
 116       | (((x) & 0x000000ff00000000ull) >> 8)                                  \
 117       | (((x) & 0x00000000ff000000ull) << 8)                                  \
 118       | (((x) & 0x0000000000ff0000ull) << 24)                                 \
 119       | (((x) & 0x000000000000ff00ull) << 40)                                 \
 120       | (((x) & 0x00000000000000ffull) << 56))
 121
 122 # define __bswap_64(x) \
 123      (__extension__                                                           \
 124       ({ union { __extension__ unsigned long long int __ll;                   \
 125                  unsigned long int __l[2]; } __w, __r;                        \
 126          if (__builtin_constant_p (x))                                        \
 127            __r.__ll = __bswap_constant_64 (x);                                \
 128          else                                                                 \
 129            {                                                                  \
 130              __w.__ll = (x);                                                  \
 131              __r.__l[0] = __bswap_32 (__w.__l[1]);                            \
 132              __r.__l[1] = __bswap_32 (__w.__l[0]);                            \
 133            }                                                                  \
 134          __r.__ll; }))
 135 #endif
 136
 137 #endif /* _BITS_BYTESWAP_H */