src/bswap.h

   1 /*
   2  * Copyright (C) 2009-2011 the libgit2 contributors
   3  *
   4  * This file is part of libgit2, distributed under the GNU GPL v2 with
   5  * a Linking Exception. For full terms see the included COPYING file.
   6  */
   7
   8 #include "common.h"
   9
  10 /*
  11  * Default version that the compiler ought to optimize properly with
  12  * constant values.
  13  */
  14 GIT_INLINE(uint32_t) default_swab32(uint32_t val)
  15 {
  16         return (((val & 0xff000000) >> 24) |
  17                 ((val & 0x00ff0000) >>  8) |
  18                 ((val & 0x0000ff00) <<  8) |
  19                 ((val & 0x000000ff) << 24));
  20 }
  21
  22 #undef bswap32
  23
  24 GIT_INLINE(uint16_t) default_swab16(uint16_t val)
  25 {
  26         return (((val & 0xff00) >> 8) |
  27                 ((val & 0x00ff) << 8));
  28 }
  29
  30 #undef bswap16
  31
  32 #if defined(__GNUC__) && defined(__i386__)
  33
  34 #define bswap32(x) ({ \
  35         uint32_t __res; \
  36         if (__builtin_constant_p(x)) { \
  37                 __res = default_swab32(x); \
  38         } else { \
  39                 __asm__("bswap %0" : "=r" (__res) : "0" ((uint32_t)(x))); \
  40         } \
  41         __res; })
  42
  43 #define bswap16(x) ({ \
  44         uint16_t __res; \
  45         if (__builtin_constant_p(x)) { \
  46                 __res = default_swab16(x); \
  47         } else { \
  48                 __asm__("xchgb %b0,%h0" : "=q" (__res) : "0" ((uint16_t)(x))); \
  49         } \
  50         __res; })
  51
  52 #elif defined(__GNUC__) && defined(__x86_64__)
  53
  54 #define bswap32(x) ({ \
  55         uint32_t __res; \
  56         if (__builtin_constant_p(x)) { \
  57                 __res = default_swab32(x); \
  58         } else { \
  59                 __asm__("bswapl %0" : "=r" (__res) : "0" ((uint32_t)(x))); \
  60         } \
  61         __res; })
  62
  63 #define bswap16(x) ({ \
  64         uint16_t __res; \
  65         if (__builtin_constant_p(x)) { \
  66                 __res = default_swab16(x); \
  67         } else { \
  68                 __asm__("xchgb %b0,%h0" : "=Q" (__res) : "0" ((uint16_t)(x))); \
  69         } \
  70         __res; })
  71
  72 #elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
  73
  74 #include <stdlib.h>
  75
  76 #define bswap32(x) _byteswap_ulong(x)
  77 #define bswap16(x) _byteswap_ushort(x)
  78
  79 #endif
  80
  81 #ifdef bswap32
  82
  83 #undef ntohl
  84 #undef htonl
  85 #define ntohl(x) bswap32(x)
  86 #define htonl(x) bswap32(x)
  87
  88 #endif
  89
  90 #ifdef bswap16
  91
  92 #undef ntohs
  93 #undef htons
  94 #define ntohs(x) bswap16(x)
  95 #define htons(x) bswap16(x)
  96
  97 #endif