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/*
* Frozen
* Copyright 2016 QuarksLab
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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
*
* 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.
*/
#ifndef FROZEN_LETITGO_ELSA_H
#define FROZEN_LETITGO_ELSA_H
#include <type_traits>
namespace frozen {
template <class T = void> struct elsa {
static_assert(std::is_integral<T>::value || std::is_enum<T>::value,
"only supports integral types, specialize for other types");
constexpr std::size_t operator()(T const &value, std::size_t seed) const {
std::size_t key = seed ^ static_cast<std::size_t>(value);
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;
}
};
template <> struct elsa<void> {
template<class T>
constexpr std::size_t operator()(T const &value, std::size_t seed) const {
return elsa<T>{}(value, seed);
}
};
template <class T> using anna = elsa<T>;
} // namespace frozen
#endif
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