115 lines
3.6 KiB
C++
115 lines
3.6 KiB
C++
// Licensed to the Apache Software Foundation (ASF) under one
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// or more contributor license agreements. See the NOTICE file
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// distributed with this work for additional information
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// regarding copyright ownership. The ASF licenses this file
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// to you under the Apache License, Version 2.0 (the
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// "License"); you may not use this file except in compliance
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// with the License. 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,
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// software distributed under the License is distributed on an
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// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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// KIND, either express or implied. See the License for the
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// specific language governing permissions and limitations
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// under the License.
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#pragma once
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#include <iterator>
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#include <list>
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#include <unordered_map>
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namespace doris {
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template <typename Key, typename Value>
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class LruCache {
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public:
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typedef typename std::pair<Key, Value> KeyValuePair;
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typedef typename std::list<KeyValuePair>::iterator ListIterator;
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class Iterator {
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public:
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using iterator_category = std::input_iterator_tag;
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using value_type = KeyValuePair;
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using difference_type = ptrdiff_t;
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using pointer = KeyValuePair*;
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using reference = KeyValuePair&;
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Iterator(typename std::unordered_map<Key, ListIterator>::iterator it) : _it(it) {}
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Iterator& operator++() {
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++_it;
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return *this;
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}
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bool operator==(const Iterator& rhs) const { return _it == rhs._it; }
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bool operator!=(const Iterator& rhs) const { return _it != rhs._it; }
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KeyValuePair* operator->() { return _it->second.operator->(); }
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KeyValuePair& operator*() { return *_it->second; }
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private:
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typename std::unordered_map<Key, ListIterator>::iterator _it;
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};
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LruCache(size_t max_size) : _max_size(max_size) {}
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void put(const Key& key, const Value& value) {
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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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_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_list.push_front(KeyValuePair(key, value));
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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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void erase(const Key& 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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_cache_items_list.erase(it->second);
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_cache_items_map.erase(it);
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}
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}
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// Must copy value, because value maybe released when caller used
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bool get(const Key& key, Value* value) {
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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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}
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_cache_items_list.splice(_cache_items_list.begin(), _cache_items_list, it->second);
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*value = it->second->second;
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return true;
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}
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bool exists(const Key& 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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Iterator begin() { return Iterator(_cache_items_map.begin()); }
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Iterator end() { return Iterator(_cache_items_map.end()); }
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private:
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std::list<KeyValuePair> _cache_items_list;
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std::unordered_map<Key, ListIterator> _cache_items_map;
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size_t _max_size;
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};
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} // namespace doris
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