77 lines
1.9 KiB
C
77 lines
1.9 KiB
C
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/*
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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 <functional>
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#include <memory>
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#include <mutex>
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#include <optional>
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#include <folly/container/EvictingCacheMap.h>
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namespace facebook::react {
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/*
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* Simple thread-safe LRU cache.
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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() : map_{maxSize} {}
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SimpleThreadSafeCache(unsigned long size) : map_{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, std::function<ValueT(const KeyT& key)> generator)
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const {
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std::lock_guard<std::mutex> lock(mutex_);
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auto iterator = map_.find(key);
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if (iterator == map_.end()) {
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auto value = generator(key);
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map_.set(key, value);
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return value;
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}
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return iterator->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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std::lock_guard<std::mutex> lock(mutex_);
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auto iterator = map_.find(key);
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if (iterator == map_.end()) {
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return {};
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}
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return iterator->second;
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}
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/*
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* Sets a key-value pair in the LRU cache.
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* Can be called from any thread.
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*/
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void set(const KeyT& key, const ValueT& value) const {
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std::lock_guard<std::mutex> lock(mutex_);
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map_.set(std::move(key), std::move(value));
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}
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private:
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mutable folly::EvictingCacheMap<KeyT, ValueT> map_;
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mutable std::mutex mutex_;
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};
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} // namespace facebook::react
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