stellar-stellar/deps/dablooms/murmur.cpp

//-----------------------------------------------------------------------------
// MurmurHash3 was written by Austin Appleby, and is placed in the public
// domain. The author hereby disclaims copyright to this source code.

// Note - The x86 and x64 versions do _not_ produce the same results, as the
// algorithms are optimized for their respective platforms. You can still
// compile and run any of them on any platform, but your performance with the
// non-native version will be less than optimal.

#include "murmur.h"

#define FORCE_INLINE inline static

FORCE_INLINE uint64_t rotl64(uint64_t x, int8_t r)
{
	return (x << r) | (x >> (64 - r));
}

#define ROTL64(x, y) rotl64(x, y)

#define BIG_CONSTANT(x) (x##LLU)

#define getblock(x, i) (x[i])

//-----------------------------------------------------------------------------
// Finalization mix - force all bits of a hash block to avalanche

FORCE_INLINE uint64_t fmix64(uint64_t k)
{
	k ^= k >> 33;
	k *= BIG_CONSTANT(0xff51afd7ed558ccd);
	k ^= k >> 33;
	k *= BIG_CONSTANT(0xc4ceb9fe1a85ec53);
	k ^= k >> 33;

	return k;
}

//-----------------------------------------------------------------------------

void MurmurHash3_x64_128(const void *key, const int len, const uint32_t seed, void *out)
{
	const uint8_t *data = (const uint8_t *)key;
	const int nblocks = len / 16;

	uint64_t h1 = seed;
	uint64_t h2 = seed;

	uint64_t c1 = BIG_CONSTANT(0x87c37b91114253d5);
	uint64_t c2 = BIG_CONSTANT(0x4cf5ad432745937f);

	int i;

	//----------
	// body

	const uint64_t *blocks = (const uint64_t *)(data);

	for (i = 0; i < nblocks; i++)
	{
		uint64_t k1 = getblock(blocks, i * 2 + 0);
		uint64_t k2 = getblock(blocks, i * 2 + 1);

		k1 *= c1;
		k1 = ROTL64(k1, 31);
		k1 *= c2;
		h1 ^= k1;

		h1 = ROTL64(h1, 27);
		h1 += h2;
		h1 = h1 * 5 + 0x52dce729;

		k2 *= c2;
		k2 = ROTL64(k2, 33);
		k2 *= c1;
		h2 ^= k2;

		h2 = ROTL64(h2, 31);
		h2 += h1;
		h2 = h2 * 5 + 0x38495ab5;
	}

	//----------
	// tail

	const uint8_t *tail = (const uint8_t *)(data + nblocks * 16);

	uint64_t k1 = 0;
	uint64_t k2 = 0;

	switch (len & 15)
	{
	case 15:
		k2 ^= ((uint64_t)tail[14]) << 48;
		[[fallthrough]];
	case 14:
		k2 ^= ((uint64_t)tail[13]) << 40;
		[[fallthrough]];
	case 13:
		k2 ^= ((uint64_t)tail[12]) << 32;
		[[fallthrough]];
	case 12:
		k2 ^= ((uint64_t)tail[11]) << 24;
		[[fallthrough]];
	case 11:
		k2 ^= ((uint64_t)tail[10]) << 16;
		[[fallthrough]];
	case 10:
		k2 ^= ((uint64_t)tail[9]) << 8;
		[[fallthrough]];
	case 9:
		k2 ^= ((uint64_t)tail[8]) << 0;
		k2 *= c2;
		k2 = ROTL64(k2, 33);
		k2 *= c1;
		h2 ^= k2;
		[[fallthrough]];
	case 8:
		k1 ^= ((uint64_t)tail[7]) << 56;
		[[fallthrough]];
	case 7:
		k1 ^= ((uint64_t)tail[6]) << 48;
		[[fallthrough]];
	case 6:
		k1 ^= ((uint64_t)tail[5]) << 40;
		[[fallthrough]];
	case 5:
		k1 ^= ((uint64_t)tail[4]) << 32;
		[[fallthrough]];
	case 4:
		k1 ^= ((uint64_t)tail[3]) << 24;
		[[fallthrough]];
	case 3:
		k1 ^= ((uint64_t)tail[2]) << 16;
		[[fallthrough]];
	case 2:
		k1 ^= ((uint64_t)tail[1]) << 8;
		[[fallthrough]];
	case 1:
		k1 ^= ((uint64_t)tail[0]) << 0;
		k1 *= c1;
		k1 = ROTL64(k1, 31);
		k1 *= c2;
		h1 ^= k1;
	}

	//----------
	// finalization

	h1 ^= len;
	h2 ^= len;

	h1 += h2;
	h2 += h1;

	h1 = fmix64(h1);
	h2 = fmix64(h2);

	h1 += h2;
	h2 += h1;

	((uint64_t *)out)[0] = h1;
	((uint64_t *)out)[1] = h2;
}

//-----------------------------------------------------------------------------