46 lines
1.3 KiB
C++
46 lines
1.3 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Copyright 2010-2015 Danny Robson <danny@nerdcruft.net>
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*/
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#pragma once
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#include <cstdint>
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namespace cruft::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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} |