compat/bswap.h

   1 #ifndef COMPAT_BSWAP_H
   2 #define COMPAT_BSWAP_H
   3
   4 /*
   5  * Let's make sure we always have a sane definition for ntohl()/htonl().
   6  * Some libraries define those as a function call, just to perform byte
   7  * shifting, bringing significant overhead to what should be a simple
   8  * operation.
   9  */
  10
  11 /*
  12  * Default version that the compiler ought to optimize properly with
  13  * constant values.
  14  */
  15 static inline uint32_t default_swab32(uint32_t val)
  16 {
  17         return (((val & 0xff000000) >> 24) |
  18                 ((val & 0x00ff0000) >>  8) |
  19                 ((val & 0x0000ff00) <<  8) |
  20                 ((val & 0x000000ff) << 24));
  21 }
  22
  23 static inline uint64_t default_bswap64(uint64_t val)
  24 {
  25         return (((val & (uint64_t)0x00000000000000ffULL) << 56) |
  26                 ((val & (uint64_t)0x000000000000ff00ULL) << 40) |
  27                 ((val & (uint64_t)0x0000000000ff0000ULL) << 24) |
  28                 ((val & (uint64_t)0x00000000ff000000ULL) <<  8) |
  29                 ((val & (uint64_t)0x000000ff00000000ULL) >>  8) |
  30                 ((val & (uint64_t)0x0000ff0000000000ULL) >> 24) |
  31                 ((val & (uint64_t)0x00ff000000000000ULL) >> 40) |
  32                 ((val & (uint64_t)0xff00000000000000ULL) >> 56));
  33 }
  34
  35 #undef bswap32
  36 #undef bswap64
  37
  38 #if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
  39
  40 #define bswap32 git_bswap32
  41 static inline uint32_t git_bswap32(uint32_t x)
  42 {
  43         uint32_t result;
  44         if (__builtin_constant_p(x))
  45                 result = default_swab32(x);
  46         else
  47                 __asm__("bswap %0" : "=r" (result) : "0" (x));
  48         return result;
  49 }
  50
  51 #define bswap64 git_bswap64
  52 #if defined(__x86_64__)
  53 static inline uint64_t git_bswap64(uint64_t x)
  54 {
  55         uint64_t result;
  56         if (__builtin_constant_p(x))
  57                 result = default_bswap64(x);
  58         else
  59                 __asm__("bswap %q0" : "=r" (result) : "0" (x));
  60         return result;
  61 }
  62 #else
  63 static inline uint64_t git_bswap64(uint64_t x)
  64 {
  65         union { uint64_t i64; uint32_t i32[2]; } tmp, result;
  66         if (__builtin_constant_p(x))
  67                 result.i64 = default_bswap64(x);
  68         else {
  69                 tmp.i64 = x;
  70                 result.i32[0] = git_bswap32(tmp.i32[1]);
  71                 result.i32[1] = git_bswap32(tmp.i32[0]);
  72         }
  73         return result.i64;
  74 }
  75 #endif
  76
  77 #elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
  78
  79 #include <stdlib.h>
  80
  81 #define bswap32(x) _byteswap_ulong(x)
  82 #define bswap64(x) _byteswap_uint64(x)
  83
  84 #endif
  85
  86 #if defined(bswap32)
  87
  88 #undef ntohl
  89 #undef htonl
  90 #define ntohl(x) bswap32(x)
  91 #define htonl(x) bswap32(x)
  92
  93 #endif
  94
  95 #if defined(bswap64)
  96
  97 #undef ntohll
  98 #undef htonll
  99 #define ntohll(x) bswap64(x)
 100 #define htonll(x) bswap64(x)
 101
 102 #else
 103
 104 #undef ntohll
 105 #undef htonll
 106
 107 #if defined(__BYTE_ORDER) && defined(__LITTLE_ENDIAN) && defined(__BIG_ENDIAN)
 108
 109 # define GIT_BYTE_ORDER __BYTE_ORDER
 110 # define GIT_LITTLE_ENDIAN __LITTLE_ENDIAN
 111 # define GIT_BIG_ENDIAN __BIG_ENDIAN
 112
 113 #elif defined(BYTE_ORDER) && defined(LITTLE_ENDIAN) && defined(BIG_ENDIAN)
 114
 115 # define GIT_BYTE_ORDER BYTE_ORDER
 116 # define GIT_LITTLE_ENDIAN LITTLE_ENDIAN
 117 # define GIT_BIG_ENDIAN BIG_ENDIAN
 118
 119 #else
 120
 121 # define GIT_BIG_ENDIAN 4321
 122 # define GIT_LITTLE_ENDIAN 1234
 123
 124 # if defined(_BIG_ENDIAN) && !defined(_LITTLE_ENDIAN)
 125 #  define GIT_BYTE_ORDER GIT_BIG_ENDIAN
 126 # elif defined(_LITTLE_ENDIAN) && !defined(_BIG_ENDIAN)
 127 #  define GIT_BYTE_ORDER GIT_LITTLE_ENDIAN
 128 # elif defined(__THW_BIG_ENDIAN__) && !defined(__THW_LITTLE_ENDIAN__)
 129 #  define GIT_BYTE_ORDER GIT_BIG_ENDIAN
 130 # elif defined(__THW_LITTLE_ENDIAN__) && !defined(__THW_BIG_ENDIAN__)
 131 #  define GIT_BYTE_ORDER GIT_LITTLE_ENDIAN
 132 # else
 133 #  error "Cannot determine endianness"
 134 # endif
 135
 136 #endif
 137
 138 #if GIT_BYTE_ORDER == GIT_BIG_ENDIAN
 139 # define ntohll(n) (n)
 140 # define htonll(n) (n)
 141 #else
 142 # define ntohll(n) default_bswap64(n)
 143 # define htonll(n) default_bswap64(n)
 144 #endif
 145
 146 #endif
 147
 148 /*
 149  * Performance might be improved if the CPU architecture is OK with
 150  * unaligned 32-bit loads and a fast ntohl() is available.
 151  * Otherwise fall back to byte loads and shifts which is portable,
 152  * and is faster on architectures with memory alignment issues.
 153  */
 154
 155 #if !defined(NO_UNALIGNED_LOADS) && ( \
 156     defined(__i386__) || defined(__x86_64__) || \
 157     defined(_M_IX86) || defined(_M_X64) || \
 158     defined(__ppc__) || defined(__ppc64__) || \
 159     defined(__powerpc__) || defined(__powerpc64__) || \
 160     defined(__s390__) || defined(__s390x__))
 161
 162 #define get_be16(p)     ntohs(*(unsigned short *)(p))
 163 #define get_be32(p)     ntohl(*(unsigned int *)(p))
 164 #define get_be64(p)     ntohll(*(uint64_t *)(p))
 165 #define put_be32(p, v)  do { *(unsigned int *)(p) = htonl(v); } while (0)
 166 #define put_be64(p, v)  do { *(uint64_t *)(p) = htonll(v); } while (0)
 167
 168 #else
 169
 170 static inline uint16_t get_be16(const void *ptr)
 171 {
 172         const unsigned char *p = ptr;
 173         return  (uint16_t)p[0] << 8 |
 174                 (uint16_t)p[1] << 0;
 175 }
 176
 177 static inline uint32_t get_be32(const void *ptr)
 178 {
 179         const unsigned char *p = ptr;
 180         return  (uint32_t)p[0] << 24 |
 181                 (uint32_t)p[1] << 16 |
 182                 (uint32_t)p[2] <<  8 |
 183                 (uint32_t)p[3] <<  0;
 184 }
 185
 186 static inline uint64_t get_be64(const void *ptr)
 187 {
 188         const unsigned char *p = ptr;
 189         return  (uint64_t)get_be32(&p[0]) << 32 |
 190                 (uint64_t)get_be32(&p[4]) <<  0;
 191 }
 192
 193 static inline void put_be32(void *ptr, uint32_t value)
 194 {
 195         unsigned char *p = ptr;
 196         p[0] = value >> 24;
 197         p[1] = value >> 16;
 198         p[2] = value >>  8;
 199         p[3] = value >>  0;
 200 }
 201
 202 static inline void put_be64(void *ptr, uint64_t value)
 203 {
 204         unsigned char *p = ptr;
 205         p[0] = value >> 56;
 206         p[1] = value >> 48;
 207         p[2] = value >> 40;
 208         p[3] = value >> 32;
 209         p[4] = value >> 24;
 210         p[5] = value >> 16;
 211         p[6] = value >>  8;
 212         p[7] = value >>  0;
 213 }
 214
 215 #endif
 216
 217 #endif /* COMPAT_BSWAP_H */