Mercurial > hg > orthanc
view Core/MultiThreading/CacheIndex.h @ 282:915ed24547ea
cache lru policy
author | Sebastien Jodogne <s.jodogne@gmail.com> |
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date | Wed, 12 Dec 2012 13:17:42 +0100 |
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children | c9977db00e1d |
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/** * Orthanc - A Lightweight, RESTful DICOM Store * Copyright (C) 2012 Medical Physics Department, CHU of Liege, * Belgium * * This program is free software: you can redistribute it and/or * modify it under the terms of the GNU General Public License as * published by the Free Software Foundation, either version 3 of the * License, or (at your option) any later version. * * In addition, as a special exception, the copyright holders of this * program give permission to link the code of its release with the * OpenSSL project's "OpenSSL" library (or with modified versions of it * that use the same license as the "OpenSSL" library), and distribute * the linked executables. You must obey the GNU General Public License * in all respects for all of the code used other than "OpenSSL". If you * modify file(s) with this exception, you may extend this exception to * your version of the file(s), but you are not obligated to do so. If * you do not wish to do so, delete this exception statement from your * version. If you delete this exception statement from all source files * in the program, then also delete it here. * * This program 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 * General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program. If not, see <http://www.gnu.org/licenses/>. **/ #pragma once #include <list> #include <map> #include <boost/noncopyable.hpp> namespace Orthanc { class NullType { }; /** * This class implements the index of a cache with least recently * used (LRU) recycling policy. All the items of the cache index * can be associated with a payload. * Reference: http://stackoverflow.com/a/2504317 **/ template <typename T, typename Payload = NullType> class CacheIndex : public boost::noncopyable { private: typedef std::list< std::pair<T, Payload> > Queue; typedef std::map<T, typename Queue::iterator> Index; Index index_; Queue queue_; /** * Internal method for debug builds to check whether the internal * data structures are not corrupted. **/ void CheckInvariants() const; public: /** * Add a new element to the cache index, and make it the most * recent element. * \param id The ID of the element. * \param payload The payload of the element. **/ void Add(T id, Payload payload = Payload()); /** * When accessing an element of the cache, this method tags the * element as the most recently used. * \param id The most recently accessed item. **/ void TagAsMostRecent(T id); /** * Remove an element from the cache index. * \param id The item to remove. **/ Payload Invalidate(T id); /** * Get the oldest element in the cache and remove it. * \return The oldest item. **/ T RemoveOldest() { Payload p; return RemoveOldest(p); } /** * Get the oldest element in the cache, remove it and return the * associated payload. * \param payload Where to store the associated payload. * \return The oldest item. **/ T RemoveOldest(Payload& payload); /** * Check whether an element is contained in the cache. * \param id The item. * \return \c true iff the item is indexed by the cache. **/ bool Contains(T id) const { return index_.find(id) != index_.end(); } /** * Check whether the cache index is empty. * \return \c true iff the cache is empty. **/ bool IsEmpty() const { return index_.empty(); } }; }