chromium/net/third_party/quiche/src/quiche/quic/core/quic_lru_cache.h

// 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 "quiche/quic/platform/api/quic_export.h"
#include "quiche/quic/platform/api/quic_flag_utils.h"
#include "quiche/quic/platform/api/quic_flags.h"
#include "quiche/quic/platform/api/quic_logging.h"
#include "quiche/common/quiche_linked_hash_map.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 Hash = std::hash<K>,
          class Eq = std::equal_to<K>>
class QUICHE_EXPORT QuicLRUCache {
 private:
  using HashMapType =
      typename quiche::QuicheLinkedHashMap<K, std::unique_ptr<V>, Hash, Eq>;

 public:
  // The iterator, if valid, points to std::pair<K, std::unique_ptr<V>>.
  using iterator = typename HashMapType::iterator;
  using const_iterator = typename HashMapType::const_iterator;
  using reverse_iterator = typename HashMapType::reverse_iterator;
  using const_reverse_iterator = typename HashMapType::const_reverse_iterator;

  explicit QuicLRUCache(size_t capacity) : … { … }
  QuicLRUCache(const QuicLRUCache&) = delete;
  QuicLRUCache& operator=(const QuicLRUCache&) = delete;

  iterator begin() { … }
  const_iterator begin() const { … }

  iterator end() { … }
  const_iterator end() const { … }

  reverse_iterator rbegin() { … }
  const_reverse_iterator rbegin() const { … }

  reverse_iterator rend() { … }
  const_reverse_iterator rend() const { … }

  // 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) { … }

  iterator Lookup(const K& key) { … }

  iterator Erase(iterator iter) { … }

  // Removes all entries from the cache.
  void Clear() { … }

  // Returns maximum size of the cache.
  size_t MaxSize() const { … }

  // Returns current size of the cache.
  size_t Size() const { … }

 private:
  quiche::QuicheLinkedHashMap<K, std::unique_ptr<V>, Hash, Eq> cache_;
  const size_t capacity_;
};

}  // namespace quic

#endif  // QUICHE_QUIC_CORE_QUIC_LRU_CACHE_H_