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#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
  21
  22#define bswap32(x) ({ \
  23        uint32_t __res; \
  24        if (__builtin_constant_p(x)) { \
  25                __res = default_swab32(x); \
  26        } else { \
  27                __asm__("bswap %0" : "=r" (__res) : "0" (x)); \
  28        } \
  29        __res; })
  30
  31#undef ntohl
  32#undef htonl
  33#define ntohl(x) bswap32(x)
  34#define htonl(x) bswap32(x)
  35
  36#endif