ims: move InMemoryStorage from util/
refs #3940
Change-Id: I4468fe9b65ef6263a62800701eb6b03df28fa274
diff --git a/src/ims/in-memory-storage-lfu.hpp b/src/ims/in-memory-storage-lfu.hpp
new file mode 100644
index 0000000..7633cfd
--- /dev/null
+++ b/src/ims/in-memory-storage-lfu.hpp
@@ -0,0 +1,119 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2013-2017 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_LFU_HPP
+#define NDN_IMS_IN_MEMORY_STORAGE_LFU_HPP
+
+#include "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/ordered_index.hpp>
+
+namespace ndn {
+
+/** @brief Provides an in-memory storage with Least Frequently Used (LFU) replacement policy.
+ * @note The frequency right now is usage count.
+ * @sa https://en.wikipedia.org/w/index.php?title=Least_frequently_used&oldid=604542656
+ */
+class InMemoryStorageLfu : public InMemoryStorage
+{
+public:
+ explicit
+ InMemoryStorageLfu(size_t limit = 10);
+
+ explicit
+ InMemoryStorageLfu(boost::asio::io_service& ioService, size_t limit = 10);
+
+NDN_CXX_PUBLIC_WITH_TESTS_ELSE_PROTECTED:
+ /** @brief Removes one Data packet from in-memory storage based on LFU, i.e. evict the least
+ * frequently 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,
+ * increment the frequency according to LFU
+ */
+ 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:
+ // binds frequency and entry together
+ struct CleanupEntry
+ {
+ InMemoryStorageEntry* entry;
+ uint64_t frequency; // could potentially be overflowed
+ };
+
+ /** @brief Function to increment frequency of the entry in the CleanupEntry
+ */
+ static inline void
+ incrementFrequency(CleanupEntry& cleanupEntry)
+ {
+ ++cleanupEntry.frequency;
+ }
+
+private:
+ // multi_index_container to implement LFU
+ class byFrequency;
+ class byEntity;
+
+ typedef boost::multi_index_container<
+ CleanupEntry,
+ boost::multi_index::indexed_by<
+
+ // by Entry itself
+ boost::multi_index::hashed_unique<
+ boost::multi_index::tag<byEntity>,
+ boost::multi_index::member<CleanupEntry, InMemoryStorageEntry*, &CleanupEntry::entry>
+ >,
+
+ // by frequency (LFU)
+ boost::multi_index::ordered_non_unique<
+ boost::multi_index::tag<byFrequency>,
+ boost::multi_index::member<CleanupEntry, uint64_t, &CleanupEntry::frequency>,
+ std::less<uint64_t>
+ >
+
+ >
+ > CleanupIndex;
+
+ CleanupIndex m_cleanupIndex;
+};
+
+} // namespace ndn
+
+#endif // NDN_IMS_IN_MEMORY_STORAGE_LFU_HPP