Robin E. R. Davies
124 lines
4.4 KiB
C++
124 lines
4.4 KiB
C++
/*
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* Copyright (c) 2025 Robin E. R. Davies
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* All rights reserved.
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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/*
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* Copyright (c) 2025 Robin E. R. Davies
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* All rights reserved.
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* Permission is hereby granted, free of charge, to any person obtaining a copy
|
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
|
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* furnished to do so, subject to the following conditions:
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#pragma once
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#include <unordered_map>
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#include <list>
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#include <stdexcept>
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template <typename KEY, typename VALUE>
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class LRUCache {
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public:
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struct CacheNode {
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KEY key;
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VALUE value;
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CacheNode(KEY k, VALUE v) : key(k), value(v) {}
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};
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private:
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size_t capacity;
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std::list<CacheNode> cache_list; // Doubly-linked list for LRU order
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std::unordered_map<KEY, typename std::list<CacheNode>::iterator> cache_map; // Map key to list iterator
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public:
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explicit LRUCache(size_t cap) : capacity(cap) {
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if (cap == 0) {
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throw std::invalid_argument("Cache capacity must be greater than 0");
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}
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}
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// Get value by key, return false if not found
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bool get(const KEY& key, VALUE& value) {
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auto it = cache_map.find(key);
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if (it == cache_map.end()) {
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return false;
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}
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// Move to front (most recently used)
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cache_list.splice(cache_list.begin(), cache_list, it->second);
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value = it->second->value;
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return true;
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}
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// Put key-value pair into cache
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void put(const KEY& key, const VALUE& value) {
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auto it = cache_map.find(key);
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if (it != cache_map.end()) {
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// Update existing key
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cache_list.splice(cache_list.begin(), cache_list, it->second);
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it->second->value = value;
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return;
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}
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// Add new key-value pair
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cache_list.emplace_front(key, value);
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cache_map[key] = cache_list.begin();
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// Evict least recently used if over capacity
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if (cache_map.size() > capacity) {
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auto lru = cache_list.back();
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cache_map.erase(lru.key);
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cache_list.pop_back();
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}
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}
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// Check if key exists
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bool contains(const KEY& key) const {
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return cache_map.find(key) != cache_map.end();
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}
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// Get current size
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size_t size() const {
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return cache_map.size();
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}
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// Get capacity
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size_t get_capacity() const {
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return capacity;
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}
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const std::list<CacheNode> &cache() const {
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return cache_list;
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}
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};
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