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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 }