87 lines
2.2 KiB
C++
87 lines
2.2 KiB
C++
/*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* Copyright 2010 Danny Robson <danny@nerdcruft.net>
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*/
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#include "hash.hpp"
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uint32_t
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util::wang32 (uint32_t key) {
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uint32_t c2 = 0x27d4eb2d; // a prime or an odd constant
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key = (key ^ 61) ^ (key >> 16);
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key = key + (key << 3);
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key = key ^ (key >> 4);
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key = key * c2;
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key = key ^ (key >> 15);
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return key;
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}
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uint64_t
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util::wang64 (uint64_t key) {
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key = (~key) + (key << 21); // key = (key << 21) - key - 1;
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key = key ^ (key >> 24);
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key = (key + (key << 3)) + (key << 8); // key * 265
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key = key ^ (key >> 14);
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key = (key + (key << 2)) + (key << 4); // key * 21
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key = key ^ (key >> 28);
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key = key + (key << 31);
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return key;
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}
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// 32: 2^ 24 + 2^8 + 0x93
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// 64: 2^ 40 + 2^8 + 0xb3
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// 128: 2^ 88 + 2^8 + 0x3B
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// 256: 2^168 + 2^8 + 0x63
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// 512: 2^344 + 2^8 + 0x57
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// 1024: 2^680 + 2^8 + 0x8D
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static const uint32_t FNV_1a_32_PRIME = 16777619U;
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static const uint64_t FNV_1a_64_PRIME = 1099511628211U;
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// Bias is the FNV-0 hash of "chongo <Landon Curt Noll> /\\../\\"
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static const uint32_t FNV_1a_32_BIAS = 2166136261U;
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static const uint64_t FNV_1a_64_BIAS = 14695981039346656037U;
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uint32_t
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util::fnv1a32 (const void *_data, size_t size) {
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const uint8_t *data = static_cast<const uint8_t*> (_data);
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uint32_t result = FNV_1a_32_BIAS;
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for (size_t i = 0; i < size; ++i) {
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result ^= data[i];
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result *= FNV_1a_32_PRIME;
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}
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return result;
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}
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uint64_t
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util::fnv1a64 (const void *_data, size_t size) {
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const uint8_t *data = static_cast<const uint8_t*> (_data);
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uint64_t result = FNV_1a_64_BIAS;
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for (size_t i = 0; i < size; ++i) {
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result ^= data[i];
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result *= FNV_1a_64_PRIME;
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}
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return result;
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}
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