mirror of https://gitee.com/bigwinds/arangodb
133 lines
4.4 KiB
C++
133 lines
4.4 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// DISCLAIMER
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///
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/// Copyright 2014-2016 ArangoDB GmbH, Cologne, Germany
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/// Copyright 2004-2014 triAGENS GmbH, Cologne, Germany
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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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/// Copyright holder is ArangoDB GmbH, Cologne, Germany
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///
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/// Portions of the code are:
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///
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/// Copyright (c) 2014, lamerman
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/// All rights reserved.
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///
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/// Redistribution and use in source and binary forms, with or without
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/// modification, are permitted provided that the following conditions are met:
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///
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/// * Redistributions of source code must retain the above copyright notice,
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/// this
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/// list of conditions and the following disclaimer.
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///
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/// * Redistributions in binary form must reproduce the above copyright notice,
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/// this list of conditions and the following disclaimer in the documentation
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/// and/or other materials provided with the distribution.
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///
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/// * Neither the name of lamerman nor the names of its
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/// contributors may be used to endorse or promote products derived from
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/// this software without specific prior written permission.
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///
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/// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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/// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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/// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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/// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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/// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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/// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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/// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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/// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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/// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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/// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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/// POSSIBILITY OF SUCH DAMAGE.
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///
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//////////////////////////////////////////////////////////////////////////////////
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#ifndef ARANGODB_LRUCACHE_H
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#define ARANGODB_LRUCACHE_H 1
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#include <cstddef>
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#include <list>
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#include <stdexcept>
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#include <unordered_map>
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namespace arangodb {
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namespace basics {
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template <typename key_t, typename value_t>
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class LruCache {
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public:
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typedef typename std::pair<key_t, value_t> key_value_pair_t;
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typedef typename std::list<key_value_pair_t>::iterator list_iterator_t;
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LruCache(size_t max_size) : _max_size(max_size) {}
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void put(const key_t& key, const value_t& value) {
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auto it = _cache_items_map.find(key);
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_cache_items_list.push_front(key_value_pair_t(key, value));
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if (it != _cache_items_map.end()) {
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_cache_items_list.erase(it->second);
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_cache_items_map.erase(it);
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}
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_cache_items_map[key] = _cache_items_list.begin();
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if (_cache_items_map.size() > _max_size) {
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auto last = _cache_items_list.end();
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last--;
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_cache_items_map.erase(last->first);
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_cache_items_list.pop_back();
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}
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}
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value_t const* get(const key_t& key) {
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auto it = _cache_items_map.find(key);
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if (it == _cache_items_map.end()) {
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return nullptr;
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} else {
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_cache_items_list.splice(_cache_items_list.begin(), _cache_items_list, it->second);
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return &it->second->second;
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}
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}
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bool remove(key_t const& key) {
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auto it = _cache_items_map.find(key);
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if (it == _cache_items_map.end()) {
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return false;
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} else {
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_cache_items_list.erase(it->second);
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_cache_items_map.erase(it);
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return true;
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}
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}
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void clear() {
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_cache_items_map.clear();
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_cache_items_list.clear();
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}
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bool exists(const key_t& key) const {
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return _cache_items_map.find(key) != _cache_items_map.end();
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}
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size_t size() const { return _cache_items_map.size(); }
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private:
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std::list<key_value_pair_t> _cache_items_list;
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std::unordered_map<key_t, list_iterator_t> _cache_items_map;
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size_t _max_size;
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};
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} // namespace basics
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} // namespace arangodb
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#endif
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