sapling/mercurial/bitmanipulation.h

#ifndef _HG_BITMANIPULATION_H_
#define _HG_BITMANIPULATION_H_

#include <string.h>

#include "compat.h"

#if defined(_MSC_VER)
/* Windows only supports little-endian platforms */
static inline uint64_t hg_be_u64(uint64_t x)
{
	return _byteswap_uint64(x);
}
static inline uint32_t hg_be_u32(uint32_t x)
{
	return _byteswap_ulong(x);
}
static inline uint16_t hg_be_u16(uint16_t x)
{
	return _byteswap_ushort(x);
}
#elif __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
static inline uint64_t hg_be_u64(uint64_t x)
{
	return __builtin_bswap64(x);
}
static inline uint32_t hg_be_u32(uint32_t x)
{
	return __builtin_bswap32(x);
}
static inline uint16_t hg_be_u16(uint16_t x)
{
	return __builtin_bswap16(x);
}
#else
/* For completeness... */
static inline uint64_t hg_be_u64(uint64_t x)
{
	return x;
}
static inline uint32_t hg_be_u32(uint32_t x)
{
	return x;
}
static inline uint16_t hg_be_u16(uint16_t x)
{
	return x;
}
#endif

static inline uint32_t getbe32(const char *c)
{
	uint32_t value;
	memcpy(&value, c, sizeof(value));
	return hg_be_u32(value);
}

static inline uint16_t getbeuint16(const char *c)
{
	uint16_t value;
	memcpy(&value, c, sizeof(value));
	return hg_be_u16(value);
}

static inline int16_t getbeint16(const char *c)
{
	/*
	 * Note: this code technically has undefined behavior for negative
	 * values, although it's written in a way that the compiler and UBSAN
	 * hopefully shouldn't complain about it.
	 *
	 * This relies on the platform using 2s-compliment representations for
	 * signed integers.  This isn't guaranteed by the C standard, but is
	 * true in practice for all modern platforms.
	 */
	union {
		uint16_t unsignedvalue;
		int16_t signedvalue;
	} u;
	u.unsignedvalue = getbeuint16(c);
	return u.signedvalue;
}

static inline void putbe32(uint32_t x, char *c)
{
	uint32_t v = hg_be_u32(x);
	memcpy(c, &v, sizeof(v));
}

static inline double getbefloat64(const char *c)
{
	uint64_t n;
	double d;
	memcpy(&n, c, sizeof(n));
	n = hg_be_u64(n);
	memcpy(&d, &n, sizeof(n));
	return d;
}

#endif