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fixed-hash64.c
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fixed-hash64.c
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#include "fixed-hash64.h"
#include "defs.h"
#define BIG_CONSTANT(x) (x##LLU)
static 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;
}
static FORCE_INLINE uint32_t rotl32 ( uint32_t x, int8_t r )
{
return (x << r) | (x >> (32 - r));
}
uint64_t fixed_hash64(const void *key, int len, uint32_t seed)
{
uint32_t h1 = seed;
uint32_t h2 = seed;
const uint64_t c1 = BIG_CONSTANT(0x87c37b91114253d5);
const uint64_t c2 = BIG_CONSTANT(0x4cf5ad432745937f);
uint32_t k1 = (uint32_t) (uintptr_t) key;
uint32_t k2 = (uint32_t) ((uintptr_t) key >> (uint64_t) 32);
k1 *= c1;
k1 = rotl32(k1,31);
k1 *= c2;
h1 ^= k1;
h1 = rotl32(h1,27);
h1 += h2;
h1 = h1 * 5 + 0x52dce729;
k2 *= c2;
k2 = rotl32(k2,33);
k2 *= c1;
h2 ^= k2;
h2 = rotl32(h2,31);
h2 += h1;
h2 = h2 * 5 + 0x38495ab5;
h1 ^= len; h2 ^= len;
h1 += h2;
h2 += h1;
h1 = fmix64(h1);
h2 = fmix64(h2);
h1 += h2;
h2 += h1;
uint64_t result = ((uint64_t) h1 << 32) | (uint64_t) h2;
return result;
}