content: /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.activemq.memory.list;
  
  import java.util.ArrayList;
  import java.util.Iterator;
  import java.util.LinkedList;
  import java.util.List;
  import org.apache.activemq.broker.region.MessageReference;
  import org.apache.activemq.command.ActiveMQDestination;
  import org.apache.activemq.command.Message;
  import org.apache.activemq.filter.DestinationFilter;
  
  /**
   * A simple fixed size {@link MessageList} where there is a single, fixed size
   * list that all messages are added to for simplicity. Though this will lead to
   * possibly slow recovery times as many more messages than is necessary will
   * have to be iterated through for each subscription.
   * 
   * 
   */
  public class SimpleMessageList implements MessageList {
      private final LinkedList<MessageReference> list = new LinkedList<MessageReference>();
      private int maximumSize = 100 * 64 * 1024;
      private int size;
      private final Object lock = new Object();
  
      public SimpleMessageList() {
      }
  
      public SimpleMessageList(int maximumSize) {
          this.maximumSize = maximumSize;
      }
  
      public void add(MessageReference node) {
          int delta = node.getMessageHardRef().getSize();
          synchronized (lock) {
              list.add(node);
              size += delta;
              while (size > maximumSize) {
                  MessageReference evicted = list.removeFirst();
                  size -= evicted.getMessageHardRef().getSize();
              }
          }
      }
  
      public List<MessageReference> getMessages(ActiveMQDestination destination) {
          return getList();
      }
  
      public Message[] browse(ActiveMQDestination destination) {
          List<Message> result = new ArrayList<Message>();
          DestinationFilter filter = DestinationFilter.parseFilter(destination);
          synchronized (lock) {
              for (Iterator<MessageReference> i = list.iterator(); i.hasNext();) {
                  MessageReference ref = i.next();
                  Message msg;
                  msg = ref.getMessage();
                  if (filter.matches(msg.getDestination())) {
                      result.add(msg);
                  }
  
              }
          }
          return result.toArray(new Message[result.size()]);
      }
  
      /**
       * Returns a copy of the list
       */
      public List<MessageReference> getList() {
          synchronized (lock) {
              return new ArrayList<MessageReference>(list);
          }
      }
  
      public int getSize() {
          synchronized (lock) {
              return size;
          }
      }
  
      public void clear() {
          synchronized (lock) {
              list.clear();
              size = 0;
          }
      }
  
  }
  