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// Copyright (c) 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef QUICHE_QUIC_CORE_QUIC_LRU_CACHE_H_
#define QUICHE_QUIC_CORE_QUIC_LRU_CACHE_H_
#include <memory>
#include "quic/platform/api/quic_containers.h"
#include "quic/platform/api/quic_export.h"
#include "quic/platform/api/quic_flag_utils.h"
#include "quic/platform/api/quic_flags.h"
#include "quic/platform/api/quic_logging.h"
namespace quic {
// A LRU cache that maps from type Key to Value* in QUIC.
// This cache CANNOT be shared by multiple threads (even with locks) because
// Value* returned by Lookup() can be invalid if the entry is evicted by other
// threads.
template <class K, class V>
class QUIC_NO_EXPORT QuicLRUCache {
public:
explicit QuicLRUCache(size_t capacity) : capacity_(capacity) {}
QuicLRUCache(const QuicLRUCache&) = delete;
QuicLRUCache& operator=(const QuicLRUCache&) = delete;
// Inserts one unit of |key|, |value| pair to the cache. Cache takes ownership
// of inserted |value|.
void Insert(const K& key, std::unique_ptr<V> value) {
auto it = cache_.find(key);
if (it != cache_.end()) {
cache_.erase(it);
}
cache_.emplace(key, std::move(value));
if (cache_.size() > capacity_) {
cache_.pop_front();
}
QUICHE_DCHECK_LE(cache_.size(), capacity_);
}
// If cache contains an entry for |key|, return a pointer to it. This returned
// value is guaranteed to be valid until Insert or Clear.
// Else return nullptr.
V* Lookup(const K& key) {
auto it = cache_.find(key);
if (it == cache_.end()) {
return nullptr;
}
std::unique_ptr<V> value = std::move(it->second);
cache_.erase(it);
auto result = cache_.emplace(key, std::move(value));
QUICHE_DCHECK(result.second);
return result.first->second.get();
}
// Removes all entries from the cache.
void Clear() { cache_.clear(); }
// Returns maximum size of the cache.
size_t MaxSize() const { return capacity_; }
// Returns current size of the cache.
size_t Size() const { return cache_.size(); }
private:
QuicLinkedHashMap<K, std::unique_ptr<V>> cache_;
const size_t capacity_;
};
} // namespace quic
#endif // QUICHE_QUIC_CORE_QUIC_LRU_CACHE_H_
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