001/**
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.activemq.memory.list;
018
019import java.util.ArrayList;
020import java.util.Iterator;
021import java.util.LinkedList;
022import java.util.List;
023import org.apache.activemq.broker.region.MessageReference;
024import org.apache.activemq.command.ActiveMQDestination;
025import org.apache.activemq.command.Message;
026import org.apache.activemq.filter.DestinationFilter;
027
028/**
029 * A simple fixed size {@link MessageList} where there is a single, fixed size
030 * list that all messages are added to for simplicity. Though this will lead to
031 * possibly slow recovery times as many more messages than is necessary will
032 * have to be iterated through for each subscription.
033 * 
034 * 
035 */
036public class SimpleMessageList implements MessageList {
037    private final LinkedList<MessageReference> list = new LinkedList<MessageReference>();
038    private int maximumSize = 100 * 64 * 1024;
039    private int size;
040    private final Object lock = new Object();
041
042    public SimpleMessageList() {
043    }
044
045    public SimpleMessageList(int maximumSize) {
046        this.maximumSize = maximumSize;
047    }
048
049    public void add(MessageReference node) {
050        int delta = node.getMessageHardRef().getSize();
051        synchronized (lock) {
052            list.add(node);
053            size += delta;
054            while (size > maximumSize) {
055                MessageReference evicted = list.removeFirst();
056                size -= evicted.getMessageHardRef().getSize();
057            }
058        }
059    }
060
061    public List<MessageReference> getMessages(ActiveMQDestination destination) {
062        return getList();
063    }
064
065    public Message[] browse(ActiveMQDestination destination) {
066        List<Message> result = new ArrayList<Message>();
067        DestinationFilter filter = DestinationFilter.parseFilter(destination);
068        synchronized (lock) {
069            for (Iterator<MessageReference> i = list.iterator(); i.hasNext();) {
070                MessageReference ref = i.next();
071                Message msg;
072                msg = ref.getMessage();
073                if (filter.matches(msg.getDestination())) {
074                    result.add(msg);
075                }
076
077            }
078        }
079        return result.toArray(new Message[result.size()]);
080    }
081
082    /**
083     * Returns a copy of the list
084     */
085    public List<MessageReference> getList() {
086        synchronized (lock) {
087            return new ArrayList<MessageReference>(list);
088        }
089    }
090
091    public int getSize() {
092        synchronized (lock) {
093            return size;
094        }
095    }
096
097    public void clear() {
098        synchronized (lock) {
099            list.clear();
100            size = 0;
101        }
102    }
103
104}