Danny Robson
09aa86f55f
This code can now be found in libcruft-crypto. It was removed to prevent people relying on it, and to improve test iteration times in unoptimised builds.
58 lines
1.7 KiB
C++
58 lines
1.7 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 2010-2015 Danny Robson <danny@nerdcruft.net>
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*/
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#ifndef __UTIL_HASH_WANG_HPP
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#define __UTIL_HASH_WANG_HPP
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#include <cstdint>
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namespace util::hash {
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// Thomas Wang's integer mixing functions, ca 2007
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//-------------------------------------------------------------------------
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constexpr uint32_t
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wang (uint32_t key)
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{
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// a prime or an odd constant
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constexpr uint32_t c2 = 0x27d4eb2d;
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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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//-------------------------------------------------------------------------
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constexpr uint64_t
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wang (uint64_t key)
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{
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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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}
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#endif
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