murmurhash.h

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#include <derive-c/core.h>
#include <stddef.h>
#include <stdint.h>
 
FORCE_INLINE uint32_t derive_c_rotl32(uint32_t x, int8_t r) { return (x << r) | (x >> (32 - r)); }
 
FORCE_INLINE uint64_t derive_c_rotl64(uint64_t x, int8_t r) { return (x << r) | (x >> (64 - r)); }
 
FORCE_INLINE uint32_t derive_c_getblock32(const uint32_t* p, int32_t i) { return p[i]; }
 
FORCE_INLINE uint64_t derive_c_getblock64(const uint64_t* p, int32_t i) { return p[i]; }
 
FORCE_INLINE uint32_t derive_c_fmix32(uint32_t h) {
    h ^= h >> 16;
    h *= 0x85ebca6b;
    h ^= h >> 13;
    h *= 0xc2b2ae35;
    h ^= h >> 16;
 
    return h;
}
 
FORCE_INLINE uint64_t derive_c_fmix64(uint64_t k) {
    k ^= k >> 33;
    k *= 0xff51afd7ed558ccdLLU;
    k ^= k >> 33;
    k *= 0xc4ceb9fe1a85ec53LLU;
    k ^= k >> 33;
 
    return k;
}
 
void derive_c_MurmurHash3_x86_32(const void* key, int32_t len, uint32_t seed, void* out) {
    const uint8_t* data = (const uint8_t*)key;
    const int32_t 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 + (ptrdiff_t)(nblocks * 4));
 
    for (int i = -nblocks; i; i++) {
        uint32_t k1 = derive_c_getblock32(blocks, i);
 
        k1 *= c1;
        k1 = derive_c_rotl32(k1, 15);
        k1 *= c2;
 
        h1 ^= k1;
        h1 = derive_c_rotl32(h1, 13);
        h1 = h1 * 5 + 0xe6546b64;
    }
 
    // tail
 
    const uint8_t* tail = (const uint8_t*)(data + (ptrdiff_t)(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 = derive_c_rotl32(k1, 15);
        k1 *= c2;
        h1 ^= k1;
    default:
    };
 
    // finalization
 
    h1 ^= len;
 
    h1 = derive_c_fmix32(h1);
 
    *(uint32_t*)out = h1;
}
 
void derive_c_MurmurHash3_x86_128(const void* key, const int32_t len, uint32_t seed, void* out) {
    const uint8_t* data = (const uint8_t*)key;
    const int32_t 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 + (ptrdiff_t)(nblocks * 16));
 
    for (int i = -nblocks; i; i++) {
        uint32_t k1 = derive_c_getblock32(blocks, (i * 4) + 0);
        uint32_t k2 = derive_c_getblock32(blocks, (i * 4) + 1);
        uint32_t k3 = derive_c_getblock32(blocks, (i * 4) + 2);
        uint32_t k4 = derive_c_getblock32(blocks, (i * 4) + 3);
 
        k1 *= c1;
        k1 = derive_c_rotl32(k1, 15);
        k1 *= c2;
        h1 ^= k1;
 
        h1 = derive_c_rotl32(h1, 19);
        h1 += h2;
        h1 = h1 * 5 + 0x561ccd1b;
 
        k2 *= c2;
        k2 = derive_c_rotl32(k2, 16);
        k2 *= c3;
        h2 ^= k2;
 
        h2 = derive_c_rotl32(h2, 17);
        h2 += h3;
        h2 = h2 * 5 + 0x0bcaa747;
 
        k3 *= c3;
        k3 = derive_c_rotl32(k3, 17);
        k3 *= c4;
        h3 ^= k3;
 
        h3 = derive_c_rotl32(h3, 15);
        h3 += h4;
        h3 = h3 * 5 + 0x96cd1c35;
 
        k4 *= c4;
        k4 = derive_c_rotl32(k4, 18);
        k4 *= c1;
        h4 ^= k4;
 
        h4 = derive_c_rotl32(h4, 13);
        h4 += h1;
        h4 = h4 * 5 + 0x32ac3b17;
    }
 
    // tail
 
    const uint8_t* tail = (const uint8_t*)(data + (ptrdiff_t)(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;
    case 14:
        k4 ^= tail[13] << 8;
    case 13:
        k4 ^= tail[12] << 0;
        k4 *= c4;
        k4 = derive_c_rotl32(k4, 18);
        k4 *= c1;
        h4 ^= k4;
 
    case 12:
        k3 ^= tail[11] << 24;
    case 11:
        k3 ^= tail[10] << 16;
    case 10:
        k3 ^= tail[9] << 8;
    case 9:
        k3 ^= tail[8] << 0;
        k3 *= c3;
        k3 = derive_c_rotl32(k3, 17);
        k3 *= c4;
        h3 ^= k3;
 
    case 8:
        k2 ^= tail[7] << 24;
    case 7:
        k2 ^= tail[6] << 16;
    case 6:
        k2 ^= tail[5] << 8;
    case 5:
        k2 ^= tail[4] << 0;
        k2 *= c2;
        k2 = derive_c_rotl32(k2, 16);
        k2 *= c3;
        h2 ^= k2;
 
    case 4:
        k1 ^= tail[3] << 24;
    case 3:
        k1 ^= tail[2] << 16;
    case 2:
        k1 ^= tail[1] << 8;
    case 1:
        k1 ^= tail[0] << 0;
        k1 *= c1;
        k1 = derive_c_rotl32(k1, 15);
        k1 *= c2;
        h1 ^= k1;
    default:
    };
 
    // finalization
 
    h1 ^= len;
    h2 ^= len;
    h3 ^= len;
    h4 ^= len;
 
    h1 += h2;
    h1 += h3;
    h1 += h4;
    h2 += h1;
    h3 += h1;
    h4 += h1;
 
    h1 = derive_c_fmix32(h1);
    h2 = derive_c_fmix32(h2);
    h3 = derive_c_fmix32(h3);
    h4 = derive_c_fmix32(h4);
 
    h1 += h2;
    h1 += h3;
    h1 += h4;
    h2 += h1;
    h3 += h1;
    h4 += h1;
 
    ((uint32_t*)out)[0] = h1;
    ((uint32_t*)out)[1] = h2;
    ((uint32_t*)out)[2] = h3;
    ((uint32_t*)out)[3] = h4;
}
 
void derive_c_MurmurHash3_x64_128(const void* key, const int32_t len, const uint32_t seed,
                                  void* out) {
    const uint8_t* data = (const uint8_t*)key;
    const int32_t nblocks = len / 16;
 
    uint64_t h1 = seed;
    uint64_t h2 = seed;
 
    const uint64_t c1 = 0x87c37b91114253d5LLU;
    const uint64_t c2 = 0x4cf5ad432745937fLLU;
 
    // body
 
    const uint64_t* blocks = (const uint64_t*)(data);
 
    for (int32_t i = 0; i < nblocks; i++) {
        uint64_t k1 = derive_c_getblock64(blocks, (i * 2) + 0);
        uint64_t k2 = derive_c_getblock64(blocks, (i * 2) + 1);
 
        k1 *= c1;
        k1 = derive_c_rotl64(k1, 31);
        k1 *= c2;
        h1 ^= k1;
 
        h1 = derive_c_rotl64(h1, 27);
        h1 += h2;
        h1 = h1 * 5 + 0x52dce729;
 
        k2 *= c2;
        k2 = derive_c_rotl64(k2, 33);
        k2 *= c1;
        h2 ^= k2;
 
        h2 = derive_c_rotl64(h2, 31);
        h2 += h1;
        h2 = h2 * 5 + 0x38495ab5;
    }
 
    // tail
 
    const uint8_t* tail = (const uint8_t*)(data + (ptrdiff_t)(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 = derive_c_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 = derive_c_rotl64(k1, 31);
        k1 *= c2;
        h1 ^= k1;
    default:
    };
 
    // finalization
 
    h1 ^= len;
    h2 ^= len;
 
    h1 += h2;
    h2 += h1;
 
    h1 = derive_c_fmix64(h1);
    h2 = derive_c_fmix64(h2);
 
    h1 += h2;
    h2 += h1;
 
    ((uint64_t*)out)[0] = h1;
    ((uint64_t*)out)[1] = h2;
}
 
size_t derive_c_murmurhash(const void* key, int32_t len, uint32_t seed) {
#if SIZE_MAX == UINT64_MAX
    // 64-bit platform: use the x64 128-bit variant, return lower 64 bits
    uint64_t out128[2];
    derive_c_MurmurHash3_x64_128(key, len, seed, out128);
    return (size_t)out128[0];
#elif SIZE_MAX == UINT32_MAX
    // 32-bit platform: use the x86 32-bit variant
    uint32_t out32;
    MurmurHash3_x86_32(key, len, seed, &out32);
    return (size_t)out32;
#else
#error "Unsupported size_t width"
#endif
}