util: in-memory storage
refs #1940
specification:
http://redmine.named-data.net/projects/ndn-cxx/wiki/InMemoryStorage
Change-Id: I7416d0dac4b4865ad931c3bf83180a043788405b
diff --git a/src/util/in-memory-storage-lru.hpp b/src/util/in-memory-storage-lru.hpp
new file mode 100644
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+++ b/src/util/in-memory-storage-lru.hpp
@@ -0,0 +1,102 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2014 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_UTIL_IN_MEMORY_STORAGE_LRU_HPP
+#define NDN_UTIL_IN_MEMORY_STORAGE_LRU_HPP
+
+#include "in-memory-storage.hpp"
+
+#include <boost/multi_index/member.hpp>
+#include <boost/multi_index_container.hpp>
+#include <boost/multi_index/sequenced_index.hpp>
+#include <boost/multi_index/hashed_index.hpp>
+#include <boost/multi_index/identity.hpp>
+
+namespace ndn {
+namespace util {
+
+/** @brief Provides in-memory storage employing LRU replacement policy, of which the least
+ * recently used entry will be evict first.
+ */
+class InMemoryStorageLru : public InMemoryStorage
+{
+public:
+ explicit
+ InMemoryStorageLru(size_t limit = 10);
+
+ virtual
+ ~InMemoryStorageLru();
+
+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 }
+ */
+ virtual bool
+ evictItem();
+
+ /** @brief Update the entry when the entry is returned by the find() function,
+ * update the last used time according to LRU
+ */
+ virtual void
+ afterAccess(InMemoryStorageEntry* entry);
+
+ /** @brief Update the entry after a entry is successfully inserted, add it to the cleanupIndex
+ */
+ virtual void
+ afterInsert(InMemoryStorageEntry* entry);
+
+ /** @brief Update the entry or other data structures before a entry is successfully erased,
+ * erase it from the cleanupIndex
+ */
+ virtual void
+ beforeErase(InMemoryStorageEntry* entry);
+
+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 util
+} // namespace ndn
+
+#endif // NDN_UTIL_IN_MEMORY_STORAGE_LRU_HPP