58 lines
1.8 KiB
C++
58 lines
1.8 KiB
C++
/*
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* Frozen
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* Copyright 2016 QuarksLab
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*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. 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,
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* software distributed under the License is distributed on an
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* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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* KIND, either express or implied. See the License for the
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* specific language governing permissions and limitations
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* under the License.
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*/
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#ifndef FROZEN_LETITGO_ELSA_H
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#define FROZEN_LETITGO_ELSA_H
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#include <type_traits>
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namespace frozen {
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template <class T = void> struct elsa {
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static_assert(std::is_integral<T>::value || std::is_enum<T>::value,
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"only supports integral types, specialize for other types");
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constexpr std::size_t operator()(T const &value, std::size_t seed) const {
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std::size_t key = seed ^ static_cast<std::size_t>(value);
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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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template <> struct elsa<void> {
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template<class T>
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constexpr std::size_t operator()(T const &value, std::size_t seed) const {
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return elsa<T>{}(value, seed);
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}
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};
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template <class T=void> using anna = elsa<T>;
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} // namespace frozen
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#endif
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