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71 lines
2.1 KiB
71 lines
2.1 KiB
/*
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* Copyright 2014 Google Inc. All rights reserved.
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*
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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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#ifndef FRUIT_HASH_CODES_DEFN_H
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#define FRUIT_HASH_CODES_DEFN_H
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#include <fruit/impl/util/hash_codes.h>
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namespace fruit {
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namespace impl {
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template <typename Tuple, int index>
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inline std::size_t hashTupleElement(const Tuple& x) {
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const auto& value = std::get<index>(x);
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using T = typename std::remove_const<typename std::remove_reference<decltype(value)>::type>::type;
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return std::hash<T>()(value);
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}
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template <typename Tuple, int last_index>
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struct HashTupleHelper;
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template <int last_index>
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struct HashTupleHelper<std::tuple<>, last_index> {
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std::size_t operator()(const std::tuple<>&) {
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return 0;
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}
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};
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template <typename... Args>
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struct HashTupleHelper<std::tuple<Args...>, 1> {
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std::size_t operator()(const std::tuple<Args...>& x) {
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return hashTupleElement<std::tuple<Args...>, 0>(x);
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}
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};
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template <typename... Args, int last_index>
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struct HashTupleHelper<std::tuple<Args...>, last_index> {
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std::size_t operator()(const std::tuple<Args...>& x) {
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return combineHashes(hashTupleElement<std::tuple<Args...>, last_index - 1>(x),
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HashTupleHelper<std::tuple<Args...>, last_index - 1>()(x));
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}
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};
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template <typename... Args>
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inline std::size_t hashTuple(const std::tuple<Args...>& x) {
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return HashTupleHelper<std::tuple<Args...>, sizeof...(Args)>()(x);
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}
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inline std::size_t combineHashes(std::size_t h1, std::size_t h2) {
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h1 ^= h2 + 0x9e3779b9 + (h1 << 6) + (h1 >> 2);
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return h1;
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}
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} // namespace impl
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} // namespace fruit
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#endif // FRUIT_HASH_CODES_DEFN_H
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