Andrew's git - gitweb.git/blob

   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 */
  12static 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
  20static 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
  38static 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__)
  50static 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
  60static 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
 167static 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
 174static 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
 183static 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
 190static 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
 199static 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