git/compat/bswap.h

51 строка
1.0 KiB
C

/*
* Let's make sure we always have a sane definition for ntohl()/htonl().
* Some libraries define those as a function call, just to perform byte
* shifting, bringing significant overhead to what should be a simple
* operation.
*/
/*
* Default version that the compiler ought to optimize properly with
* constant values.
*/
static inline uint32_t default_swab32(uint32_t val)
{
return (((val & 0xff000000) >> 24) |
((val & 0x00ff0000) >> 8) |
((val & 0x0000ff00) << 8) |
((val & 0x000000ff) << 24));
}
#undef bswap32
#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
#define bswap32 git_bswap32
static inline uint32_t git_bswap32(uint32_t x)
{
uint32_t result;
if (__builtin_constant_p(x))
result = default_swab32(x);
else
__asm__("bswap %0" : "=r" (result) : "0" (x));
return result;
}
#elif defined(_MSC_VER) && (defined(_M_IX86) || defined(_M_X64))
#include <stdlib.h>
#define bswap32(x) _byteswap_ulong(x)
#endif
#ifdef bswap32
#undef ntohl
#undef htonl
#define ntohl(x) bswap32(x)
#define htonl(x) bswap32(x)
#endif