compat/bswap.h

   1 /*
   2  * Let's make sure we always have a sane definition for ntohl()/htonl().
   3  * Some libraries define those as a function call, just to perform byte
   4  * shifting, bringing significant overhead to what should be a simple
   5  * operation.
   6  */
   7
   8 /*
   9  * Default version that the compiler ought to optimize properly with
  10  * constant values.
  11  */
  12 static inline uint32_t default_swab32(uint32_t val)
  13 {
  14         return (((val & 0xff000000) >> 24) |
  15                 ((val & 0x00ff0000) >>  8) |
  16                 ((val & 0x0000ff00) <<  8) |
  17                 ((val & 0x000000ff) << 24));
  18 }
  19
  20 static inline uint64_t default_bswap64(uint64_t val)
  21 {
  22         return (((val & (uint64_t)0x00000000000000ffULL) << 56) |
  23                 ((val & (uint64_t)0x000000000000ff00ULL) << 40) |
  24                 ((val & (uint64_t)0x0000000000ff0000ULL) << 24) |
  25                 ((val & (uint64_t)0x00000000ff000000ULL) <<  8) |
  26                 ((val & (uint64_t)0x000000ff00000000ULL) >>  8) |
  27                 ((val & (uint64_t)0x0000ff0000000000ULL) >> 24) |
  28                 ((val & (uint64_t)0x00ff000000000000ULL) >> 40) |
  29                 ((val & (uint64_t)0xff00000000000000ULL) >> 56));
  30 }
  31
  32 #undef bswap32
  33 #undef bswap64
  34
  35 #if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
  36
  37 #define bswap32 git_bswap32
  38 static inline uint32_t git_bswap32(uint32_t x)
  39 {
  40         uint32_t result;
  41         if (__builtin_constant_p(x))
  42                 result = default_swab32(x);
  43         else
  44                 __asm__("bswap %0" : "=r" (result) : "0" (x));
  45         return result;
  46 }
  47
  48 #define bswap64 git_bswap64
  49 #if defined(__x86_64__)
  50 static inline uint64_t git_bswap64(uint64_t x)
  51 {
  52         uint64_t result;
  53         if (__builtin_constant_p(x))
  54                 result = default_bswap64(x);
  55         else
  56                 __asm__("bswap %q0" : "=r" (result) : "0" (x));
  57         return result;
  58 }
  59 #else
  60 static inline uint64_t git_bswap64(uint64_t x)
  61 {
  62         union { uint64_t i64; uint32_t i32[2]; } tmp, result;
  63         if (__builtin_constant_p(x))
  64                 result.i64 = default_bswap64(x);
  65         else {
  66                 tmp.i64 = x;
  67                 result.i32[0] = git_bswap32(tmp.i32[1]);
  68                 result.i32[1] = git_bswap32(tmp.i32[0]);
  69         }
  70         return result.i64;
  71 }
  72 #endif
  73
  74 #elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
  75
  76 #include <stdlib.h>
  77
  78 #define bswap32(x) _byteswap_ulong(x)
  79 #define bswap64(x) _byteswap_uint64(x)
  80
  81 #endif
  82
  83 #if defined(bswap32)
  84
  85 #undef ntohl
  86 #undef htonl
  87 #define ntohl(x) bswap32(x)
  88 #define htonl(x) bswap32(x)
  89
  90 #endif
  91
  92 #if defined(bswap64)
  93
  94 #undef ntohll
  95 #undef htonll
  96 #define ntohll(x) bswap64(x)
  97 #define htonll(x) bswap64(x)
  98
  99 #else
 100
 101 #undef ntohll
 102 #undef htonll
 103
 104 #if defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && defined(__BIG_ENDIAN)
 105
 106 # define GIT_BYTE_ORDER __BYTE_ORDER
 107 # define GIT_LITTLE_ENDIAN __LITTLE_ENDIAN
 108 # define GIT_BIG_ENDIAN __BIG_ENDIAN
 109
 110 #elif defined(BYTE_ORDER) && defined(LITTLE_ENDIAN) && defined(BIG_ENDIAN)
 111
 112 # define GIT_BYTE_ORDER BYTE_ORDER
 113 # define GIT_LITTLE_ENDIAN LITTLE_ENDIAN
 114 # define GIT_BIG_ENDIAN BIG_ENDIAN
 115
 116 #else
 117
 118 # define GIT_BIG_ENDIAN 4321
 119 # define GIT_LITTLE_ENDIAN 1234
 120
 121 # if defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)
 122 #  define GIT_BYTE_ORDER GIT_BIG_ENDIAN
 123 # elif defined(_LITTLE_ENDIAN) && !defined(_BIG_ENDIAN)
 124 #  define GIT_BYTE_ORDER GIT_LITTLE_ENDIAN
 125 # elif defined(__THW_BIG_ENDIAN__) && !defined(__THW_LITTLE_ENDIAN__)
 126 #  define GIT_BYTE_ORDER GIT_BIG_ENDIAN
 127 # elif defined(__THW_LITTLE_ENDIAN__) && !defined(__THW_BIG_ENDIAN__)
 128 #  define GIT_BYTE_ORDER GIT_LITTLE_ENDIAN
 129 # else
 130 #  error "Cannot determine endianness"
 131 # endif
 132
 133 #endif
 134
 135 #if GIT_BYTE_ORDER == GIT_BIG_ENDIAN
 136 # define ntohll(n) (n)
 137 # define htonll(n) (n)
 138 #else
 139 # define ntohll(n) default_bswap64(n)
 140 # define htonll(n) default_bswap64(n)
 141 #endif
 142
 143 #endif
 144
 145 /*
 146  * Performance might be improved if the CPU architecture is OK with
 147  * unaligned 32-bit loads and a fast ntohl() is available.
 148  * Otherwise fall back to byte loads and shifts which is portable,
 149  * and is faster on architectures with memory alignment issues.
 150  */
 151
 152 #if !defined(NO_UNALIGNED_LOADS) && ( \
 153     defined(__i386__) || defined(__x86_64__) || \
 154     defined(_M_IX86) || defined(_M_X64) || \
 155     defined(__ppc__) || defined(__ppc64__) || \
 156     defined(__powerpc__) || defined(__powerpc64__) || \
 157     defined(__s390__) || defined(__s390x__))
 158
 159 #define get_be16(p)     ntohs(*(unsigned short *)(p))
 160 #define get_be32(p)     ntohl(*(unsigned int *)(p))
 161 #define get_be64(p)     ntohll(*(uint64_t *)(p))
 162 #define put_be32(p, v)  do { *(unsigned int *)(p) = htonl(v); } while (0)
 163 #define put_be64(p, v)  do { *(uint64_t *)(p) = htonll(v); } while (0)
 164
 165 #else
 166
 167 static inline uint16_t get_be16(const void *ptr)
 168 {
 169         const unsigned char *p = ptr;
 170         return  (uint16_t)p[0] << 8 |
 171                 (uint16_t)p[1] << 0;
 172 }
 173
 174 static inline uint32_t get_be32(const void *ptr)
 175 {
 176         const unsigned char *p = ptr;
 177         return  (uint32_t)p[0] << 24 |
 178                 (uint32_t)p[1] << 16 |
 179                 (uint32_t)p[2] <<  8 |
 180                 (uint32_t)p[3] <<  0;
 181 }
 182
 183 static inline uint64_t get_be64(const void *ptr)
 184 {
 185         const unsigned char *p = ptr;
 186         return  (uint64_t)get_be32(&p[0]) << 32 |
 187                 (uint64_t)get_be32(&p[4]) <<  0;
 188 }
 189
 190 static inline void put_be32(void *ptr, uint32_t value)
 191 {
 192         unsigned char *p = ptr;
 193         p[0] = value >> 24;
 194         p[1] = value >> 16;
 195         p[2] = value >>  8;
 196         p[3] = value >>  0;
 197 }
 198
 199 static inline void put_be64(void *ptr, uint64_t value)
 200 {
 201         unsigned char *p = ptr;
 202         p[0] = value >> 56;
 203         p[1] = value >> 48;
 204         p[2] = value >> 40;
 205         p[3] = value >> 32;
 206         p[4] = value >> 24;
 207         p[5] = value >> 16;
 208         p[6] = value >>  8;
 209         p[7] = value >>  0;
 210 }
 211
 212 #endif