murmur_hash_3.cpp

#include "murmur_hash_3.hpp"

#if defined(_MSC_VER)

#include <stdlib.h>
#define ROTL32(x,y) _rotl(x,y)
#define ROTL64(x,y) _rotl64(x,y)
#define BIG_CONSTANT(x) (x)

#else // defined(_MSC_VER)

inline uint32_t rotl32(uint32_t x, int8_t r) {
    return (x << r) | (x >> (32 - r));
}

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

#define ROTL32(x,y) rotl32(x,y)
#define ROTL64(x,y) rotl64(x,y)

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

#endif // if defined(_MSC_VER)

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

inline uint32_t fmix32(uint32_t h) {
    h ^= h >> 16;
    h *= 0x85ebca6b;
    h ^= h >> 13;
    h *= 0xc2b2ae35;
    h ^= h >> 16;

    return h;
}

inline uint64_t fmix(uint64_t k) {
    k ^= k >> 33;
    k *= BIG_CONSTANT(0xff51afd7ed558ccd);
    k ^= k >> 33;
    k *= BIG_CONSTANT(0xc4ceb9fe1a85ec53);
    k ^= k >> 33;

    return k;
}

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

void MurmurHash3_x86_32(const void *key, int len, uint32_t seed, void *out) {
    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);

    for (int i = -nblocks; i; i++) {
        uint32_t k1 = blocks[i];

        k1 *= c1;
        k1 = ROTL32(k1, 15);
        k1 *= c2;

        h1 ^= k1;
        h1 = ROTL32(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 = ROTL32(k1, 15);
        k1 *= c2;
        h1 ^= k1;
    };

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

    h1 ^= len;

    h1 = fmix32(h1);

    *(uint32_t *)out = h1;
}

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;

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

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

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

    for (int i = 0; i < nblocks; i++) {
        uint64_t k1 = blocks[i * 2 + 0];
        uint64_t k2 = 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;
    case 14:
        k2 ^= ((uint64_t)tail[13]) << 40;
    case 13:
        k2 ^= ((uint64_t)tail[12]) << 32;
    case 12:
        k2 ^= ((uint64_t)tail[11]) << 24;
    case 11:
        k2 ^= ((uint64_t)tail[10]) << 16;
    case 10:
        k2 ^= ((uint64_t)tail[9]) << 8;
    case    9:
        k2 ^= ((uint64_t)tail[ 8]) << 0;
        k2 *= c2;
        k2    = ROTL64(k2, 33);
        k2 *= c1;
        h2 ^= k2;
    case 8:
        k1 ^= ((uint64_t)tail[7]) << 56;
    case 7:
        k1 ^= ((uint64_t)tail[6]) << 48;
    case 6:
        k1 ^= ((uint64_t)tail[5]) << 40;
    case 5:
        k1 ^= ((uint64_t)tail[4]) << 32;
    case 4:
        k1 ^= ((uint64_t)tail[3]) << 24;
    case 3:
        k1 ^= ((uint64_t)tail[2]) << 16;
    case 2:
        k1 ^= ((uint64_t)tail[1]) << 8;
    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 = fmix(h1);
    h2 = fmix(h2);

    h1 += h2;
    h2 += h1;

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