Andrew's git - gitweb.git/blob

   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 */
  15static 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
  23static 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
  41static 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__)
  53static 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
  63static 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
 170static 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
 177static 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
 186static 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
 193static 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
 202static 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 */