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)
 105# if defined(BYTE_ORDER) && defined(LITTLE_ENDIAN) && defined(BIG_ENDIAN)
 106#  define __BYTE_ORDER BYTE_ORDER
 107#  define __LITTLE_ENDIAN LITTLE_ENDIAN
 108#  define __BIG_ENDIAN BIG_ENDIAN
 109# endif
 110#endif
 111
 112#if !defined(__BYTE_ORDER)
 113# error "Cannot determine endianness"
 114#endif
 115
 116#if __BYTE_ORDER == __BIG_ENDIAN
 117# define ntohll(n) (n)
 118# define htonll(n) (n)
 119#else
 120# define ntohll(n) default_bswap64(n)
 121# define htonll(n) default_bswap64(n)
 122#endif
 123
 124#endif