85 lines
2.6 KiB
C++
85 lines
2.6 KiB
C++
/*
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* Copyright (C) 2015 ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef UTILS_HASH_HH_
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#define UTILS_HASH_HH_
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#include <functional>
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#include "core/apply.hh"
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namespace utils {
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// public for unit testing etc
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inline size_t hash_combine(size_t left, size_t right) {
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return left + 0x9e3779b9 + (right << 6) + (right >> 2);
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}
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struct tuple_hash {
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private:
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// CMH. Add specializations here to handle recursive tuples
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template<typename T>
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static size_t hash(const T& t) {
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return std::hash<T>()(t);
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}
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template<size_t index, typename...Types>
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struct hash_impl {
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size_t operator()(const std::tuple<Types...>& t, size_t a) const {
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return hash_impl<index-1, Types...>()(t, hash_combine(hash(std::get<index>(t)), a));
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}
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size_t operator()(const std::tuple<Types...>& t) const {
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return hash_impl<index-1, Types...>()(t, hash(std::get<index>(t)));
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}
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};
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template<class...Types>
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struct hash_impl<0, Types...> {
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size_t operator()(const std::tuple<Types...>& t, size_t a) const {
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return hash_combine(hash(std::get<0>(t)), a);
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}
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size_t operator()(const std::tuple<Types...>& t) const {
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return hash(std::get<0>(t));
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}
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};
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public:
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template<typename T1, typename T2>
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size_t operator()(const std::pair<T1, T2>& p) const {
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return hash_combine(hash(p.first), hash(p.second));
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}
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template<typename T1, typename T2>
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size_t operator()(const T1& t1, const T2& t2) const {
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return hash_combine(hash(t1), hash(t2));
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}
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template<typename... Args>
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size_t operator()(const std::tuple<Args...>& v) const;
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};
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template<typename... Args>
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inline size_t tuple_hash::operator()(const std::tuple<Args...>& v) const {
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return hash_impl<std::tuple_size<std::tuple<Args...>>::value - 1, Args...>()(v);
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}
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template<>
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inline size_t tuple_hash::operator()(const std::tuple<>& v) const {
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return 0;
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}
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}
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#endif /* UTILS_HASH_HH_ */
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