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1   /***
2    *
3    * Copyright 2004 Hiram Chirino
4    *
5    * Licensed under the Apache License, Version 2.0 (the "License");
6    * you may not use this file except in compliance with the License.
7    * You may obtain a copy of the License at
8    *
9    * http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   *
17   **/
18  package org.activeio.packet;
19  
20  import java.util.ArrayList;
21  
22  import org.activeio.Packet;
23  
24  import EDU.oswego.cs.dl.util.concurrent.SynchronizedInt;
25  
26  /***
27   * Provides a simple pool of Packet objects.  When the packets that this pool produces are disposed,
28   * they are returned to the pool.
29   * 
30   * @version $Revision: 1.1 $
31   */
32  abstract public class PacketPool {
33      
34      public static final int DEFAULT_POOL_SIZE = Integer.parseInt(System.getProperty("org.activeio.journal.active.DefaultPoolSize", ""+(5)));
35      public static final int DEFAULT_PACKET_SIZE = Integer.parseInt(System.getProperty("org.activeio.journal.active.DefaultPacketSize", ""+(1024*1024*4)));
36      
37  	private final ArrayList pool = new ArrayList();
38  	private final int maxPackets;
39      private int currentPoolSize;
40      
41      public class PooledPacket extends FilterPacket {
42          private final SynchronizedInt referenceCounter;
43          
44          public PooledPacket(Packet next) {
45              this(next, new SynchronizedInt(0));
46          }
47          
48          private PooledPacket(Packet next, SynchronizedInt referenceCounter) {
49              super(next);
50              this.referenceCounter=referenceCounter;
51              this.referenceCounter.increment();
52          }
53          
54          public Packet filter(Packet packet) {
55              return new PooledPacket(next, referenceCounter);
56          }
57  
58          int getReferenceCounter() {
59              return referenceCounter.get();
60          }
61          
62          public void dispose() {
63              if( referenceCounter.decrement()==0 ) {
64                  returnPacket(next);
65              }
66          }
67      }
68  	
69  	/***
70  	 * @param maxPackets the number of buffers that will be in the pool.
71  	 */
72  	public PacketPool(int maxPackets) {
73  		this.maxPackets = maxPackets;
74  	}
75  	
76  	/***
77  	 * Blocks until a ByteBuffer can be retreived from the pool.
78  	 * 
79  	 * @return
80  	 * @throws InterruptedException
81  	 */
82  	public Packet getPacket() throws InterruptedException {
83  	    Packet answer=null;
84  		synchronized(this) {
85  			while(answer==null) {
86  				if( pool.size()>0) {
87  					answer = (Packet) pool.remove(pool.size()-1);
88  				} else if( currentPoolSize < maxPackets ) {
89                       answer = allocateNewPacket();
90                       currentPoolSize++;
91                   }
92  				if( answer==null ) {
93  					this.wait();
94  				}
95  			}
96  		}
97  		return new PooledPacket(answer);
98  	}
99  
100 	/***
101 	 * Returns a ByteBuffer to the pool.
102 	 * 
103 	 * @param packet
104 	 */
105 	private void returnPacket(Packet packet) {
106 		packet.clear();
107 		synchronized(this) {
108 			pool.add(packet);
109 			this.notify();
110 		}
111 	}
112 	
113     /***
114      * @return
115      */
116     abstract protected Packet allocateNewPacket();
117     
118 }