jemalloc/internal/hash.h

#ifndef JEMALLOC_INTERNAL_HASH_H
#define JEMALLOC_INTERNAL_HASH_H

#include "jemalloc/internal/assert.h"

/*
 * The following hash function is based on MurmurHash3, placed into the public
 * domain by Austin Appleby.  See https://github.com/aappleby/smhasher for
 * details.
 */

/******************************************************************************/
/* Internal implementation. */
static inline uint32_t
hash_rotl_32(uint32_t x, int8_t r) {
	return ((x << r) | (x >> (32 - r)));
}

static inline uint64_t
hash_rotl_64(uint64_t x, int8_t r) {
	return ((x << r) | (x >> (64 - r)));
}

static inline uint32_t
hash_get_block_32(const uint32_t *p, int i) {
	/* Handle unaligned read. */
	if (unlikely((uintptr_t)p & (sizeof(uint32_t)-1)) != 0) {
		uint32_t ret;

		memcpy(&ret, (const uint8_t *)(p + i), sizeof(uint32_t));
		return ret;
	}

	return p[i];
}

static inline uint64_t
hash_get_block_64(const uint64_t *p, int i) {
	/* Handle unaligned read. */
	if (unlikely((uintptr_t)p & (sizeof(uint64_t)-1)) != 0) {
		uint64_t ret;

		memcpy(&ret, (const uint8_t *)(p + i), sizeof(uint64_t));
		return ret;
	}

	return p[i];
}

static inline uint32_t
hash_fmix_32(uint32_t h) {
	h ^= h >> 16;
	h *= 0x85ebca6b;
	h ^= h >> 13;
	h *= 0xc2b2ae35;
	h ^= h >> 16;

	return h;
}

static inline uint64_t
hash_fmix_64(uint64_t k) {
	k ^= k >> 33;
	k *= KQU(0xff51afd7ed558ccd);
	k ^= k >> 33;
	k *= KQU(0xc4ceb9fe1a85ec53);
	k ^= k >> 33;

	return k;
}

static inline uint32_t
hash_x86_32(const void *key, int len, uint32_t seed) {
	const uint8_t *data = (const uint8_t *) key;
	const int nblocks = len / 4;

	uint32_t h1 = seed;

	const uint32_t c1 = 0xcc9e2d51;
	const uint32_t c2 = 0x1b873593;

	/* body */
	{
		const uint32_t *blocks = (const uint32_t *) (data + nblocks*4);
		int i;

		for (i = -nblocks; i; i++) {
			uint32_t k1 = hash_get_block_32(blocks, i);

			k1 *= c1;
			k1 = hash_rotl_32(k1, 15);
			k1 *= c2;

			h1 ^= k1;
			h1 = hash_rotl_32(h1, 13);
			h1 = h1*5 + 0xe6546b64;
		}
	}

	/* tail */
	{
		const uint8_t *tail = (const uint8_t *) (data + nblocks*4);

		uint32_t k1 = 0;

		switch (len & 3) {
		case 3: k1 ^= tail[2] << 16;
		case 2: k1 ^= tail[1] << 8;
		case 1: k1 ^= tail[0]; k1 *= c1; k1 = hash_rotl_32(k1, 15);
			k1 *= c2; h1 ^= k1;
		}
	}

	/* finalization */
	h1 ^= len;

	h1 = hash_fmix_32(h1);

	return h1;
}

UNUSED static inline void
hash_x86_128(const void *key, const int len, uint32_t seed,
    uint64_t r_out[2]) {
	const uint8_t * data = (const uint8_t *) key;
	const int nblocks = len / 16;

	uint32_t h1 = seed;
	uint32_t h2 = seed;
	uint32_t h3 = seed;
	uint32_t h4 = seed;

	const uint32_t c1 = 0x239b961b;
	const uint32_t c2 = 0xab0e9789;
	const uint32_t c3 = 0x38b34ae5;
	const uint32_t c4 = 0xa1e38b93;

	/* body */
	{
		const uint32_t *blocks = (const uint32_t *) (data + nblocks*16);
		int i;

		for (i = -nblocks; i; i++) {
			uint32_t k1 = hash_get_block_32(blocks, i*4 + 0);
			uint32_t k2 = hash_get_block_32(blocks, i*4 + 1);
			uint32_t k3 = hash_get_block_32(blocks, i*4 + 2);
			uint32_t k4 = hash_get_block_32(blocks, i*4 + 3);

			k1 *= c1; k1 = hash_rotl_32(k1, 15); k1 *= c2; h1 ^= k1;

			h1 = hash_rotl_32(h1, 19); h1 += h2;
			h1 = h1*5 + 0x561ccd1b;

			k2 *= c2; k2 = hash_rotl_32(k2, 16); k2 *= c3; h2 ^= k2;

			h2 = hash_rotl_32(h2, 17); h2 += h3;
			h2 = h2*5 + 0x0bcaa747;

			k3 *= c3; k3 = hash_rotl_32(k3, 17); k3 *= c4; h3 ^= k3;

			h3 = hash_rotl_32(h3, 15); h3 += h4;
			h3 = h3*5 + 0x96cd1c35;

			k4 *= c4; k4 = hash_rotl_32(k4, 18); k4 *= c1; h4 ^= k4;

			h4 = hash_rotl_32(h4, 13); h4 += h1;
			h4 = h4*5 + 0x32ac3b17;
		}
	}

	/* tail */
	{
		const uint8_t *tail = (const uint8_t *) (data + nblocks*16);
		uint32_t k1 = 0;
		uint32_t k2 = 0;
		uint32_t k3 = 0;
		uint32_t k4 = 0;

		switch (len & 15) {
		case 15: k4 ^= tail[14] << 16;	/*FALLTHROUGH*/
		case 14: k4 ^= tail[13] << 8;	/*FALLTHROUGH*/
		case 13: k4 ^= tail[12] << 0;
			k4 *= c4; k4 = hash_rotl_32(k4, 18); k4 *= c1; h4 ^= k4;
			/*FALLTHROUGH*/

		case 12: k3 ^= tail[11] << 24;	/*FALLTHROUGH*/
		case 11: k3 ^= tail[10] << 16;	/*FALLTHROUGH*/
		case 10: k3 ^= tail[ 9] << 8;	/*FALLTHROUGH*/
		case  9: k3 ^= tail[ 8] << 0;
			k3 *= c3; k3 = hash_rotl_32(k3, 17); k3 *= c4; h3 ^= k3;
			/*FALLTHROUGH*/

		case  8: k2 ^= tail[ 7] << 24;	/*FALLTHROUGH*/
		case  7: k2 ^= tail[ 6] << 16;	/*FALLTHROUGH*/
		case  6: k2 ^= tail[ 5] << 8;	/*FALLTHROUGH*/
		case  5: k2 ^= tail[ 4] << 0;
			k2 *= c2; k2 = hash_rotl_32(k2, 16); k2 *= c3; h2 ^= k2;
			/*FALLTHROUGH*/

		case  4: k1 ^= tail[ 3] << 24;	/*FALLTHROUGH*/
		case  3: k1 ^= tail[ 2] << 16;	/*FALLTHROUGH*/
		case  2: k1 ^= tail[ 1] << 8;	/*FALLTHROUGH*/
		case  1: k1 ^= tail[ 0] << 0;
			k1 *= c1; k1 = hash_rotl_32(k1, 15); k1 *= c2; h1 ^= k1;
		}
	}

	/* finalization */
	h1 ^= len; h2 ^= len; h3 ^= len; h4 ^= len;

	h1 += h2; h1 += h3; h1 += h4;
	h2 += h1; h3 += h1; h4 += h1;

	h1 = hash_fmix_32(h1);
	h2 = hash_fmix_32(h2);
	h3 = hash_fmix_32(h3);
	h4 = hash_fmix_32(h4);

	h1 += h2; h1 += h3; h1 += h4;
	h2 += h1; h3 += h1; h4 += h1;

	r_out[0] = (((uint64_t) h2) << 32) | h1;
	r_out[1] = (((uint64_t) h4) << 32) | h3;
}

UNUSED static inline void
hash_x64_128(const void *key, const int len, const uint32_t seed,
    uint64_t r_out[2]) {
	const uint8_t *data = (const uint8_t *) key;
	const int nblocks = len / 16;

	uint64_t h1 = seed;
	uint64_t h2 = seed;

	const uint64_t c1 = KQU(0x87c37b91114253d5);
	const uint64_t c2 = KQU(0x4cf5ad432745937f);

	/* body */
	{
		const uint64_t *blocks = (const uint64_t *) (data);
		int i;

		for (i = 0; i < nblocks; i++) {
			uint64_t k1 = hash_get_block_64(blocks, i*2 + 0);
			uint64_t k2 = hash_get_block_64(blocks, i*2 + 1);

			k1 *= c1; k1 = hash_rotl_64(k1, 31); k1 *= c2; h1 ^= k1;

			h1 = hash_rotl_64(h1, 27); h1 += h2;
			h1 = h1*5 + 0x52dce729;

			k2 *= c2; k2 = hash_rotl_64(k2, 33); k2 *= c1; h2 ^= k2;

			h2 = hash_rotl_64(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; /* falls through */
		case 14: k2 ^= ((uint64_t)(tail[13])) << 40; /* falls through */
		case 13: k2 ^= ((uint64_t)(tail[12])) << 32; /* falls through */
		case 12: k2 ^= ((uint64_t)(tail[11])) << 24; /* falls through */
		case 11: k2 ^= ((uint64_t)(tail[10])) << 16; /* falls through */
		case 10: k2 ^= ((uint64_t)(tail[ 9])) << 8;  /* falls through */
		case  9: k2 ^= ((uint64_t)(tail[ 8])) << 0;
			k2 *= c2; k2 = hash_rotl_64(k2, 33); k2 *= c1; h2 ^= k2;
			/* falls through */
		case  8: k1 ^= ((uint64_t)(tail[ 7])) << 56; /* falls through */
		case  7: k1 ^= ((uint64_t)(tail[ 6])) << 48; /* falls through */
		case  6: k1 ^= ((uint64_t)(tail[ 5])) << 40; /* falls through */
		case  5: k1 ^= ((uint64_t)(tail[ 4])) << 32; /* falls through */
		case  4: k1 ^= ((uint64_t)(tail[ 3])) << 24; /* falls through */
		case  3: k1 ^= ((uint64_t)(tail[ 2])) << 16; /* falls through */
		case  2: k1 ^= ((uint64_t)(tail[ 1])) << 8;  /* falls through */
		case  1: k1 ^= ((uint64_t)(tail[ 0])) << 0;
			k1 *= c1; k1 = hash_rotl_64(k1, 31); k1 *= c2; h1 ^= k1;
		}
	}

	/* finalization */
	h1 ^= len; h2 ^= len;

	h1 += h2;
	h2 += h1;

	h1 = hash_fmix_64(h1);
	h2 = hash_fmix_64(h2);

	h1 += h2;
	h2 += h1;

	r_out[0] = h1;
	r_out[1] = h2;
}

/******************************************************************************/
/* API. */
static inline void
hash(const void *key, size_t len, const uint32_t seed, size_t r_hash[2]) {
	assert(len <= INT_MAX); /* Unfortunate implementation limitation. */

#if (LG_SIZEOF_PTR == 3 && !defined(JEMALLOC_BIG_ENDIAN))
	hash_x64_128(key, (int)len, seed, (uint64_t *)r_hash);
#else
	{
		uint64_t hashes[2];
		hash_x86_128(key, (int)len, seed, hashes);
		r_hash[0] = (size_t)hashes[0];
		r_hash[1] = (size_t)hashes[1];
	}
#endif
}

#endif /* JEMALLOC_INTERNAL_HASH_H */