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/* This is MurmurHash3. The original C++ code was placed in the public domain
* by its author, Austin Appleby.
*
* SPDX-License-Identifier: CC0-1.0
* Source: https://github.com/aappleby/smhasher/blob/master/src/MurmurHash3.cpp */
#include "murmurhash3.h"
#include "string.h"
static inline uint32_t fmix(uint32_t h)
{
h ^= h >> 16;
h *= 0x85ebca6b;
h ^= h >> 13;
h *= 0xc2b2ae35;
h ^= h >> 16;
return h;
}
static inline uint32_t rotl32(uint32_t x, int8_t r)
{
return (x << r) | (x >> (32 - r));
}
uint32_t hash(const char* data, size_t len_)
{
const int len = (int) len_;
const int nblocks = len / 4;
uint32_t h1 = 0xc062fb4a;
uint32_t c1 = 0xcc9e2d51;
uint32_t c2 = 0x1b873593;
//----------
// body
for(int i = 0; i < nblocks; ++i)
{
uint32_t k1;
memcpy(&k1, data + i * sizeof(k1), sizeof(k1));
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 = fmix(h1);
return h1;
}
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