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
  20#undef bswap32
  21
  22#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
  23
  24#define bswap32 git_bswap32
  25static inline uint32_t git_bswap32(uint32_t x)
  26{
  27        uint32_t result;
  28        if (__builtin_constant_p(x))
  29                result = default_swab32(x);
  30        else
  31                __asm__("bswap %0" : "=r" (result) : "0" (x));
  32        return result;
  33}
  34
  35#elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
  36
  37#include <stdlib.h>
  38
  39#define bswap32(x) _byteswap_ulong(x)
  40
  41#endif
  42
  43#ifdef bswap32
  44
  45#undef ntohl
  46#undef htonl
  47#define ntohl(x) bswap32(x)
  48#define htonl(x) bswap32(x)
  49
  50#endif