text: /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
  /*
   * Copyright (c) 2013-2018 Regents of the University of California.
   *
   * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
   *
   * ndn-cxx library is free software: you can redistribute it and/or modify it under the
   * terms of the GNU Lesser General Public License as published by the Free Software
   * Foundation, either version 3 of the License, or (at your option) any later version.
   *
   * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
   * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
   * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
   *
   * You should have received copies of the GNU General Public License and GNU Lesser
   * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
   * <http://www.gnu.org/licenses/>.
   *
   * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
   */
  
  #ifndef NDN_IMS_IN_MEMORY_STORAGE_LRU_HPP
  #define NDN_IMS_IN_MEMORY_STORAGE_LRU_HPP
  
  #include "ndn-cxx/ims/in-memory-storage.hpp"
  
  #include <boost/multi_index_container.hpp>
  #include <boost/multi_index/hashed_index.hpp>
  #include <boost/multi_index/identity.hpp>
  #include <boost/multi_index/member.hpp>
  #include <boost/multi_index/sequenced_index.hpp>
  
  namespace ndn {
  
  /** @brief Provides in-memory storage employing Least Recently Used (LRU) replacement policy.
   */
  class InMemoryStorageLru : public InMemoryStorage
  {
  public:
    explicit
    InMemoryStorageLru(size_t limit = 16);
  
    InMemoryStorageLru(DummyIoService& ioService, size_t limit = 16);
  
  NDN_CXX_PUBLIC_WITH_TESTS_ELSE_PROTECTED:
    /** @brief Removes one Data packet from in-memory storage based on LRU, i.e. evict the least
     *  recently accessed Data packet
     *  @return{ whether the Data was removed }
     */
    bool
    evictItem() override;
  
    /** @brief Update the entry when the entry is returned by the find() function,
     *  update the last used time according to LRU
     */
    void
    afterAccess(InMemoryStorageEntry* entry) override;
  
    /** @brief Update the entry after a entry is successfully inserted, add it to the cleanupIndex
     */
    void
    afterInsert(InMemoryStorageEntry* entry) override;
  
    /** @brief Update the entry or other data structures before a entry is successfully erased,
     *  erase it from the cleanupIndex
     */
    void
    beforeErase(InMemoryStorageEntry* entry) override;
  
  private:
    // multi_index_container to implement LRU
    class byUsedTime;
    class byEntity;
  
    typedef boost::multi_index_container<
      InMemoryStorageEntry*,
      boost::multi_index::indexed_by<
  
        // by Entry itself
        boost::multi_index::hashed_unique<
          boost::multi_index::tag<byEntity>,
          boost::multi_index::identity<InMemoryStorageEntry*>
        >,
  
        // by last used time (LRU)
        boost::multi_index::sequenced<
          boost::multi_index::tag<byUsedTime>
        >
  
      >
    > CleanupIndex;
  
    CleanupIndex m_cleanupIndex;
  };
  
  } // namespace ndn
  
  #endif // NDN_IMS_IN_MEMORY_STORAGE_LRU_HPP
  