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123 lines
3.3 KiB
C++
123 lines
3.3 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 <cstddef>
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#include <list>
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#include <stdexcept>
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#include <unordered_map>
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#include <utility>
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namespace milvus {
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namespace cache {
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template <typename key_t, typename value_t>
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class LRU {
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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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typedef typename std::list<key_value_pair_t>::reverse_iterator reverse_list_iterator_t;
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explicit LRU(size_t max_size) : max_size_(max_size) {
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}
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void
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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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const value_t&
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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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throw std::range_error("There is no such key in cache");
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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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void
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erase(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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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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bool
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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
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size() const {
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return cache_items_map_.size();
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}
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list_iterator_t
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begin() {
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iter_ = cache_items_list_.begin();
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return iter_;
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}
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list_iterator_t
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end() {
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return cache_items_list_.end();
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}
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reverse_list_iterator_t
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rbegin() {
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return cache_items_list_.rbegin();
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}
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reverse_list_iterator_t
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rend() {
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return cache_items_list_.rend();
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}
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void
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clear() {
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cache_items_list_.clear();
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cache_items_map_.clear();
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}
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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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list_iterator_t iter_;
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};
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} // namespace cache
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} // namespace milvus
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