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/*
* Copyright 2018 Blender Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* This is taken from 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 <stdlib.h>
#include <string.h>
#include "util/math.h"
#include "util/murmurhash.h"
#if defined(_MSC_VER)
# define ROTL32(x, y) _rotl(x, y)
# define ROTL64(x, y) _rotl64(x, y)
# define BIG_CONSTANT(x) (x)
#else
ccl_device_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
CCL_NAMESPACE_BEGIN
/* Block read - if your platform needs to do endian-swapping or can only
* handle aligned reads, do the conversion here. */
ccl_device_inline uint32_t mm_hash_getblock32(const uint32_t *p, int i)
{
return p[i];
}
/* Finalization mix - force all bits of a hash block to avalanche */
ccl_device_inline uint32_t mm_hash_fmix32(uint32_t h)
{
h ^= h >> 16;
h *= 0x85ebca6b;
h ^= h >> 13;
h *= 0xc2b2ae35;
h ^= h >> 16;
return h;
}
uint32_t util_murmur_hash3(const void *key, int len, uint32_t seed)
{
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;
const uint32_t *blocks = (const uint32_t *)(data + nblocks * 4);
for (int i = -nblocks; i; i++) {
uint32_t k1 = mm_hash_getblock32(blocks, i);
k1 *= c1;
k1 = ROTL32(k1, 15);
k1 *= c2;
h1 ^= k1;
h1 = ROTL32(h1, 13);
h1 = h1 * 5 + 0xe6546b64;
}
const uint8_t *tail = (const uint8_t *)(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;
}
h1 ^= len;
h1 = mm_hash_fmix32(h1);
return h1;
}
/* This is taken from the cryptomatte specification 1.0 */
float util_hash_to_float(uint32_t hash)
{
uint32_t mantissa = hash & ((1 << 23) - 1);
uint32_t exponent = (hash >> 23) & ((1 << 8) - 1);
exponent = max(exponent, (uint32_t)1);
exponent = min(exponent, (uint32_t)254);
exponent = exponent << 23;
uint32_t sign = (hash >> 31);
sign = sign << 31;
uint32_t float_bits = sign | exponent | mantissa;
float f;
memcpy(&f, &float_bits, sizeof(uint32_t));
return f;
}
CCL_NAMESPACE_END
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