001/**
002 *
003 * Copyright (c) 2014, the Railo Company Ltd. All rights reserved.
004 *
005 * This library is free software; you can redistribute it and/or
006 * modify it under the terms of the GNU Lesser General Public
007 * License as published by the Free Software Foundation; either 
008 * version 2.1 of the License, or (at your option) any later version.
009 * 
010 * This library is distributed in the hope that it will be useful,
011 * but WITHOUT ANY WARRANTY; without even the implied warranty of
012 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
013 * Lesser General Public License for more details.
014 * 
015 * You should have received a copy of the GNU Lesser General Public 
016 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
017 * 
018 **/
019package lucee.commons.collection.concurrent;
020
021import lucee.commons.collection.concurrent.ConcurrentLinkedHashMapPro.Entry;
022
023
024public class LFUPolicy implements EvictionPolicy {
025
026        @Override
027        public boolean accessOrder() {
028                return true;
029        }
030        
031        @Override
032        public boolean insertionOrder() {
033                return false;
034        }
035        
036        @Override
037        public Entry<?, ?> evictElement(Entry<?, ?> head) {
038                return head.getAfter();
039        }
040
041        @Override
042        public Entry<?, ?> recordInsertion(Entry<?, ?> head, Entry<?, ?> insertedEntry) {
043                return null;
044        }
045
046        @Override
047        public Entry<?, ?> recordAccess(Entry<?, ?> head, Entry<?, ?> accessedEntry) {
048                Entry<?, ?> lfuEntry = accessedEntry.getAfter();
049                while(lfuEntry != head && lfuEntry.getAccessCount() <= accessedEntry.getAccessCount())
050                        lfuEntry = lfuEntry.getAfter();
051                return lfuEntry;
052        }
053
054
055}