~laumann/C

ref: 74c6c80ca891acc54bb96e3aac560ca2ce1635e4 C/progress/bswap.h -rw-r--r-- 1.0 KiB
74c6c80c — Thomas Bracht Laumann Jespersen Added help message and -h,--help option. 9 years ago
                                                                                
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/*
 * 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