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 */ 017 package org.apache.activemq.memory.buffer; 018 019 import java.util.ArrayList; 020 import java.util.Iterator; 021 import java.util.LinkedList; 022 import java.util.List; 023 024 import org.apache.activemq.broker.region.MessageReference; 025 import org.apache.activemq.command.ActiveMQMessage; 026 import org.apache.activemq.command.Message; 027 028 /** 029 * Allows messages to be added to the end of the buffer such that they are kept 030 * around and evicted in a FIFO manner. 031 * 032 * @version $Revision: 1.1 $ 033 */ 034 public class MessageQueue { 035 036 private MessageBuffer buffer; 037 private LinkedList<MessageReference> list = new LinkedList<MessageReference>(); 038 private int size; 039 private Object lock = new Object(); 040 private int position; 041 042 public MessageQueue(MessageBuffer buffer) { 043 this.buffer = buffer; 044 } 045 046 public void add(MessageReference messageRef) { 047 Message message = messageRef.getMessageHardRef(); 048 int delta = message.getSize(); 049 int newSize = 0; 050 synchronized (lock) { 051 list.add(messageRef); 052 size += delta; 053 newSize = size; 054 } 055 buffer.onSizeChanged(this, delta, newSize); 056 } 057 058 public void add(ActiveMQMessage message) { 059 int delta = message.getSize(); 060 int newSize = 0; 061 synchronized (lock) { 062 list.add(message); 063 size += delta; 064 newSize = size; 065 } 066 buffer.onSizeChanged(this, delta, newSize); 067 } 068 069 public int evictMessage() { 070 synchronized (lock) { 071 if (!list.isEmpty()) { 072 ActiveMQMessage message = (ActiveMQMessage) list.removeFirst(); 073 int messageSize = message.getSize(); 074 size -= messageSize; 075 return messageSize; 076 } 077 } 078 return 0; 079 } 080 081 /** 082 * Returns a copy of the list 083 */ 084 public List<MessageReference> getList() { 085 synchronized (lock) { 086 return new ArrayList<MessageReference>(list); 087 } 088 } 089 090 public void appendMessages(List<MessageReference> answer) { 091 synchronized (lock) { 092 for (Iterator<MessageReference> iter = list.iterator(); iter.hasNext();) { 093 answer.add(iter.next()); 094 } 095 } 096 } 097 098 public int getSize() { 099 synchronized (lock) { 100 return size; 101 } 102 } 103 104 public int getPosition() { 105 return position; 106 } 107 108 public void setPosition(int position) { 109 this.position = position; 110 } 111 112 public void clear() { 113 synchronized (lock) { 114 list.clear(); 115 size = 0; 116 } 117 } 118 119 }