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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.codehaus.activemq.journal.impl;
    19
    20  import java.nio.ByteBuffer;
    21  import java.util.ArrayList;
    22
    23  import org.apache.commons.logging.Log;
    24  import org.apache.commons.logging.LogFactory;
    25
    26  /***
    27   * Provides a simple pool of ByteBuffer objects.
    28   *
    29   * @version $Revision: 1.1 $
    30   */
    31  public class ByteBufferPool {
    32  	final static private Log log = LogFactory.getLog(ByteBufferPool.class);
    33
    34  	private final ArrayList pool = new ArrayList();
    35  	private final int bufferSize;
    36  	private final int maxBuffers;
    37
    38  	/***
    39  	 * Creates a pool of 4 x 4 Meg ByteBuffers
    40  	 *
    41  	 */
    42  	public ByteBufferPool() {
    43  		this(4, 1024*1024*4);
    44  	}
    45
    46  	/***
    47  	 * Creates a pool of <code>bufferCount</code> ByteBuffers that are
    48  	 * directly allocated being <code>bufferSize</code> big.
    49  	 *
    50  	 * @param bufferCount the number of buffers that will be in the pool.
    51  	 * @param bufferSize the size of the buffers that are in the pool.
    52  	 */
    53  	public ByteBufferPool(int bufferCount,int bufferSize) {
    54  		this.maxBuffers = bufferCount;
    55  		this.bufferSize = bufferSize;
    56
    57  		for (int i = 0; i < bufferCount; i++) {
    58  			ByteBuffer bb = ByteBuffer.allocateDirect(bufferSize);
    59  			pool.add(bb);
    60  		}
    61  	}
    62
    63  	/***
    64  	 * Blocks until a ByteBuffer can be retreived from the pool.
    65  	 *
    66  	 * @return
    67  	 * @throws InterruptedException
    68  	 */
    69  	public ByteBuffer getByteBuffer() throws InterruptedException {
    70  		ByteBuffer answer=null;
    71  		synchronized(this) {
    72  			while(answer==null) {
    73  				if( pool.size()>0) {
    74  					answer = (ByteBuffer) pool.remove(pool.size()-1);
    75  				}
    76  				if( answer==null ) {
    77  					log.warn("Performance Warning: Buffer pool ran out of buffers.  Waiting for buffer to be returned.  System may be uner heavy load or you may need to configure more buffers in the pool.");
    78  					this.wait();
    79  				}
    80  			}
    81  		}
    82  		return answer;
    83  	}
    84
    85  	/***
    86  	 * Returns a ByteBuffer to the pool.
    87  	 *
    88  	 * @param buffer
    89  	 */
    90  	public void returnByteBuffer(ByteBuffer buffer) {
    91  		buffer.clear();
    92  		synchronized(this) {
    93  			pool.add(buffer);
    94  			this.notify();
    95  		}
    96  	}
    97
    98  }