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/* SPDX-License-Identifier: GPL-2.0-or-later
* Copyright 2018 Blender Foundation. */
/** \file
* \ingroup bli
*
* Functions to compute Murmur3 hash key.
*
* This Code is based on alShaders/Cryptomatte/MurmurHash3.h:
*
* MurmurHash3 was written by Austin Appleby, and is placed in the public
* domain. The author hereby disclaims copyright to this source code.
*/
#include "BLI_compiler_attrs.h"
#include "BLI_compiler_compat.h"
#include "BLI_hash_mm3.h" /* own include */
#if defined(_MSC_VER)
# include <stdlib.h>
# define ROTL32(x, y) _rotl(x, y)
# define BIG_CONSTANT(x) (x)
/* Other compilers */
#else /* defined(_MSC_VER) */
static inline uint32_t rotl32(uint32_t x, int8_t r)
{
return (x << r) | (x >> (32 - r));
}
# define ROTL32(x, y) rotl32(x, y)
# define BIG_CONSTANT(x) (x##LLU)
#endif /* !defined(_MSC_VER) */
/* Block read - if your platform needs to do endian-swapping or can only
* handle aligned reads, do the conversion here
*/
BLI_INLINE uint32_t getblock32(const uint32_t *p, int i)
{
return p[i];
}
BLI_INLINE uint64_t getblock64(const uint64_t *p, int i)
{
return p[i];
}
/* Finalization mix - force all bits of a hash block to avalanche */
BLI_INLINE uint32_t fmix32(uint32_t h)
{
h ^= h >> 16;
h *= 0x85ebca6b;
h ^= h >> 13;
h *= 0xc2b2ae35;
h ^= h >> 16;
return h;
}
BLI_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;
}
uint32_t BLI_hash_mm3(const unsigned char *data, size_t len, uint32_t seed)
{
const uint8_t *in_data = (const uint8_t *)data;
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 *)(in_data + nblocks * 4);
for (int i = -nblocks; i; i++) {
uint32_t k1 = getblock32(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 *)(in_data + nblocks * 4);
uint32_t k1 = 0;
switch (len & 3) {
case 3:
k1 ^= tail[2] << 16;
ATTR_FALLTHROUGH;
case 2:
k1 ^= tail[1] << 8;
ATTR_FALLTHROUGH;
case 1:
k1 ^= tail[0];
k1 *= c1;
k1 = ROTL32(k1, 15);
k1 *= c2;
h1 ^= k1;
}
/* finalization */
h1 ^= len;
h1 = fmix32(h1);
return h1;
}
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