rckrdmrd
97f407c661
- Prefijo v2: MCH - TRACEABILITY-MASTER.yml creado - Listo para integracion como submodulo Workspace: v2.0.0 | SIMCO: v4.0.0
107 lines
3.1 KiB
C++
107 lines
3.1 KiB
C++
/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#pragma once
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#include <concepts>
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#include <list>
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#include <mutex>
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#include <unordered_map>
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namespace facebook::react {
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template <typename GeneratorT, typename ValueT>
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concept CacheGeneratorFunction = std::invocable<GeneratorT> && std::same_as<std::invoke_result_t<GeneratorT>, ValueT>;
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/*
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* Simple thread-safe LRU cache.
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*
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* TODO T228961279: The maxSize template parameter should be removed, since it
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* may be overriden by the constructor.
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*/
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template <typename KeyT, typename ValueT, int maxSize>
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class SimpleThreadSafeCache {
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public:
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SimpleThreadSafeCache() : maxSize_(maxSize) {}
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SimpleThreadSafeCache(unsigned long size) : maxSize_{size} {}
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/*
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* Returns a value from the map with a given key.
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* If the value wasn't found in the cache, constructs the value using given
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* generator function, stores it inside a cache and returns it.
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* Can be called from any thread.
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*/
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ValueT get(const KeyT &key, CacheGeneratorFunction<ValueT> auto generator) const
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{
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return getMapIterator(key, std::move(generator))->second->second;
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}
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/*
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* Returns pointers to both the key and value from the map with a given key.
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* If the value wasn't found in the cache, constructs the value using given
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* generator function, stores it inside a cache and returns it.
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* Can be called from any thread.
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*/
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std::pair<const KeyT *, const ValueT *> getWithKey(const KeyT &key, CacheGeneratorFunction<ValueT> auto generator)
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const
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{
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auto it = getMapIterator(key, std::move(generator));
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return std::make_pair(&it->first, &it->second->second);
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}
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/*
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* Returns a value from the map with a given key.
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* If the value wasn't found in the cache, returns empty optional.
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* Can be called from any thread.
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*/
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std::optional<ValueT> get(const KeyT &key) const
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{
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std::lock_guard<std::mutex> lock(mutex_);
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if (auto it = map_.find(key); it != map_.end()) {
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// Move accessed item to front of list
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list_.splice(list_.begin(), list_, it->second);
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return it->second->second;
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}
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return ValueT{};
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}
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private:
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using EntryT = std::pair<KeyT, ValueT>;
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using iterator = typename std::list<EntryT>::iterator;
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auto getMapIterator(const KeyT &key, CacheGeneratorFunction<ValueT> auto generator) const
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{
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std::lock_guard<std::mutex> lock(mutex_);
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if (auto it = map_.find(key); it != map_.end()) {
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// Move accessed item to front of list
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list_.splice(list_.begin(), list_, it->second);
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return it;
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}
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auto value = generator();
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// Add new value to front of list and map
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list_.emplace_front(key, value);
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auto [it, _] = map_.insert_or_assign(key, list_.begin());
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if (list_.size() > maxSize_) {
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// Evict least recently used item (back of list)
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map_.erase(list_.back().first);
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list_.pop_back();
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}
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return it;
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}
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size_t maxSize_;
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mutable std::mutex mutex_;
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mutable std::list<EntryT> list_;
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mutable std::unordered_map<KeyT, iterator> map_;
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};
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} // namespace facebook::react
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