eu.stratosphere.nephele.io.channels.MemoryBufferRecycler Maven / Gradle / Ivy
/***********************************************************************************************************************
* Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
*
* Licensed 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 eu.stratosphere.nephele.io.channels;
import java.util.concurrent.atomic.AtomicInteger;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import eu.stratosphere.core.memory.MemorySegment;
/**
* A memory buffer recycler takes care of the correct recycling of the internal byte buffer which backs a memory buffer.
* Since buffer objects can be duplicated, i.e. multiple buffer objects point to the same physical buffer, it is
* necessary to coordinate the recycling of the physical buffer.
*
* This class is thread-safe.
*
*/
public final class MemoryBufferRecycler {
/**
* The log object used to report debug information and possible errors.
*/
private static final Log LOG = LogFactory.getLog(MemoryBufferRecycler.class);
/**
* The original memory segment which has been taken from byte buffered channel manager's buffer pool.
*/
private final MemorySegment originalSegment;
/**
* The connection to the pool from which the byte buffer has originally been taken.
*/
private final MemoryBufferPoolConnector bufferPoolConnector;
/**
* The number of memory buffer objects which may still access the physical buffer.
*/
public final AtomicInteger referenceCounter = new AtomicInteger(1);
/**
* Constructs a new memory buffer recycler.
*
* @param originalBuffer
* the original byte buffer
* @param bufferPoolConnector
* the connection to the pool from which the byte buffer has originally been taken
*/
MemoryBufferRecycler(final MemorySegment originalSegment, final MemoryBufferPoolConnector bufferPoolConnector) {
this.originalSegment = originalSegment;
this.bufferPoolConnector = bufferPoolConnector;
}
/**
* Increases the number of references to the physical buffer by one.
*/
void increaseReferenceCounter() {
if (this.referenceCounter.getAndIncrement() == 0) {
LOG.error("Increasing reference counter from 0 to 1");
}
}
/**
* Decreases the number of references to the physical buffer by one. If the number of references becomes zero the
* physical buffer is recycled.
*/
void decreaseReferenceCounter() {
final int val = this.referenceCounter.decrementAndGet();
if (val == 0) {
this.bufferPoolConnector.recycle(this.originalSegment);
} else if (val < 0) {
LOG.error("reference counter is negative");
}
}
}