libcruft-util/hash.cpp

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/*
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* 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
*
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* 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.
*
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* Copyright 2010 Danny Robson <danny@nerdcruft.net>
*/
#include "hash.hpp"
uint32_t
util::wang32 (uint32_t key) {
uint32_t c2 = 0x27d4eb2d; // a prime or an odd constant
key = (key ^ 61) ^ (key >> 16);
key = key + (key << 3);
key = key ^ (key >> 4);
key = key * c2;
key = key ^ (key >> 15);
return key;
}
uint64_t
util::wang64 (uint64_t key) {
key = (~key) + (key << 21); // key = (key << 21) - key - 1;
key = key ^ (key >> 24);
key = (key + (key << 3)) + (key << 8); // key * 265
key = key ^ (key >> 14);
key = (key + (key << 2)) + (key << 4); // key * 21
key = key ^ (key >> 28);
key = key + (key << 31);
return key;
}
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// 32: 2^ 24 + 2^8 + 0x93
// 64: 2^ 40 + 2^8 + 0xb3
// 128: 2^ 88 + 2^8 + 0x3B
// 256: 2^168 + 2^8 + 0x63
// 512: 2^344 + 2^8 + 0x57
// 1024: 2^680 + 2^8 + 0x8D
static const uint32_t FNV_1a_32_PRIME = 16777619U;
static const uint64_t FNV_1a_64_PRIME = 1099511628211U;
// Bias is the FNV-0 hash of "chongo <Landon Curt Noll> /\\../\\"
static const uint32_t FNV_1a_32_BIAS = 2166136261U;
static const uint64_t FNV_1a_64_BIAS = 14695981039346656037U;
uint32_t
util::fnv1a32 (const void *_data, size_t size) {
const uint8_t *data = static_cast<const uint8_t*> (_data);
uint32_t result = FNV_1a_32_BIAS;
for (size_t i = 0; i < size; ++i) {
result ^= data[i];
result *= FNV_1a_32_PRIME;
}
return result;
}
uint64_t
util::fnv1a64 (const void *_data, size_t size) {
const uint8_t *data = static_cast<const uint8_t*> (_data);
uint64_t result = FNV_1a_64_BIAS;
for (size_t i = 0; i < size; ++i) {
result ^= data[i];
result *= FNV_1a_64_PRIME;
}
return result;
}