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Diffstat (limited to '')
-rw-r--r-- | src/seastar/include/seastar/util/indirect.hh | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/src/seastar/include/seastar/util/indirect.hh b/src/seastar/include/seastar/util/indirect.hh new file mode 100644 index 000000000..e544a5f1a --- /dev/null +++ b/src/seastar/include/seastar/util/indirect.hh @@ -0,0 +1,74 @@ +/* + * This file is open source software, licensed to you under the terms + * of the Apache License, Version 2.0 (the "License"). See the NOTICE file + * distributed with this work for additional information regarding copyright + * ownership. 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. + */ +/* + * Copyright (C) 2016 ScyllaDB + */ + +#pragma once + +#include <memory> + +namespace seastar { + +// This header defines functors for comparing and hashing pointers by pointed-to values instead of pointer addresses. +// +// Examples: +// +// std::multiset<shared_ptr<sstring>, indirect_less<shared_ptr<sstring>>> _multiset; +// +// std::unordered_map<shared_ptr<sstring>, bool, +// indirect_hash<shared_ptr<sstring>>, indirect_equal_to<shared_ptr<sstring>>> _unordered_map; +// + +template<typename Pointer, typename Equal = std::equal_to<typename std::pointer_traits<Pointer>::element_type>> +struct indirect_equal_to { + Equal _eq; + indirect_equal_to(Equal eq = Equal()) : _eq(std::move(eq)) {} + bool operator()(const Pointer& i1, const Pointer& i2) const { + if (bool(i1) ^ bool(i2)) { + return false; + } + return !i1 || _eq(*i1, *i2); + } +}; + +template<typename Pointer, typename Less = std::less<typename std::pointer_traits<Pointer>::element_type>> +struct indirect_less { + Less _cmp; + indirect_less(Less cmp = Less()) : _cmp(std::move(cmp)) {} + bool operator()(const Pointer& i1, const Pointer& i2) const { + if (i1 && i2) { + return _cmp(*i1, *i2); + } + return !i1 && i2; + } +}; + +template<typename Pointer, typename Hash = std::hash<typename std::pointer_traits<Pointer>::element_type>> +struct indirect_hash { + Hash _h; + indirect_hash(Hash h = Hash()) : _h(std::move(h)) {} + size_t operator()(const Pointer& p) const { + if (p) { + return _h(*p); + } + return 0; + } +}; + +} |