Mercurial > hg > orthanc
diff Core/MultiThreading/CacheIndex.h @ 282:915ed24547ea
cache lru policy
author | Sebastien Jodogne <s.jodogne@gmail.com> |
---|---|
date | Wed, 12 Dec 2012 13:17:42 +0100 |
parents | |
children | c9977db00e1d |
line wrap: on
line diff
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Core/MultiThreading/CacheIndex.h Wed Dec 12 13:17:42 2012 +0100 @@ -0,0 +1,126 @@ +/** + * 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(); + } + }; +}