org.apache.commons.collections.buffer.BoundedBuffer Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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 org.apache.commons.collections.buffer;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Collection;
import java.util.Iterator;
import org.apache.commons.collections.BoundedCollection;
import org.apache.commons.collections.Buffer;
import org.apache.commons.collections.BufferOverflowException;
import org.apache.commons.collections.BufferUnderflowException;
import org.apache.commons.collections.iterators.AbstractIteratorDecorator;
/**
* Decorates another Buffer to ensure a fixed maximum size.
*
* Note: This class should only be used if you need to add bounded
* behaviour to another buffer. If you just want a bounded buffer then
* you should use {@link BoundedFifoBuffer} or {@link CircularFifoBuffer}.
*
* The decoration methods allow you to specify a timeout value.
* This alters the behaviour of the add methods when the buffer is full.
* Normally, when the buffer is full, the add method will throw an exception.
* With a timeout, the add methods will wait for up to the timeout period
* to try and add the elements.
*
* @author James Carman
* @author Stephen Colebourne
* @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
* @since Commons Collections 3.2
*/
public class BoundedBuffer extends SynchronizedBuffer implements BoundedCollection {
/** The serialization version. */
private static final long serialVersionUID = 1536432911093974264L;
/** The maximum size. */
private final int maximumSize;
/** The timeout milliseconds. */
private final long timeout;
/**
* Factory method to create a bounded buffer.
*
* When the buffer is full, it will immediately throw a
* BufferOverflowException on calling add().
*
* @param buffer the buffer to decorate, must not be null
* @param maximumSize the maximum size, must be size one or greater
* @return a new bounded buffer
* @throws IllegalArgumentException if the buffer is null
* @throws IllegalArgumentException if the maximum size is zero or less
*/
public static BoundedBuffer decorate(Buffer buffer, int maximumSize) {
return new BoundedBuffer(buffer, maximumSize, 0L);
}
/**
* Factory method to create a bounded buffer that blocks for a maximum
* amount of time.
*
* @param buffer the buffer to decorate, must not be null
* @param maximumSize the maximum size, must be size one or greater
* @param timeout the maximum amount of time to wait in milliseconds
* @return a new bounded buffer
* @throws IllegalArgumentException if the buffer is null
* @throws IllegalArgumentException if the maximum size is zero or less
*/
public static BoundedBuffer decorate(Buffer buffer, int maximumSize, long timeout) {
return new BoundedBuffer(buffer, maximumSize, timeout);
}
//-----------------------------------------------------------------------
/**
* Constructor that wraps (not copies) another buffer, making it bounded
* waiting only up to a maximum amount of time.
*
* @param buffer the buffer to wrap, must not be null
* @param maximumSize the maximum size, must be size one or greater
* @param timeout the maximum amount of time to wait
* @throws IllegalArgumentException if the buffer is null
* @throws IllegalArgumentException if the maximum size is zero or less
*/
protected BoundedBuffer(Buffer buffer, int maximumSize, long timeout) {
super(buffer);
if (maximumSize < 1) {
throw new IllegalArgumentException();
}
this.maximumSize = maximumSize;
this.timeout = timeout;
}
//-----------------------------------------------------------------------
public Object remove() {
synchronized (lock) {
Object returnValue = getBuffer().remove();
lock.notifyAll();
return returnValue;
}
}
public boolean add(Object o) {
synchronized (lock) {
timeoutWait(1);
return getBuffer().add(o);
}
}
public boolean addAll(final Collection c) {
synchronized (lock) {
timeoutWait(c.size());
return getBuffer().addAll(c);
}
}
public Iterator iterator() {
return new NotifyingIterator(collection.iterator());
}
private void timeoutWait(final int nAdditions) {
// method synchronized by callers
if (nAdditions > maximumSize) {
throw new BufferOverflowException(
"Buffer size cannot exceed " + maximumSize);
}
if (timeout <= 0) {
// no wait period (immediate timeout)
if (getBuffer().size() + nAdditions > maximumSize) {
throw new BufferOverflowException(
"Buffer size cannot exceed " + maximumSize);
}
return;
}
final long expiration = System.currentTimeMillis() + timeout;
long timeLeft = expiration - System.currentTimeMillis();
while (timeLeft > 0 && getBuffer().size() + nAdditions > maximumSize) {
try {
lock.wait(timeLeft);
timeLeft = expiration - System.currentTimeMillis();
} catch (InterruptedException ex) {
PrintWriter out = new PrintWriter(new StringWriter());
ex.printStackTrace(out);
throw new BufferUnderflowException(
"Caused by InterruptedException: " + out.toString());
}
}
if (getBuffer().size() + nAdditions > maximumSize) {
throw new BufferOverflowException("Timeout expired");
}
}
public boolean isFull() {
// size() is synchronized
return (size() == maxSize());
}
public int maxSize() {
return maximumSize;
}
//-----------------------------------------------------------------------
/**
* BoundedBuffer iterator.
*/
private class NotifyingIterator extends AbstractIteratorDecorator {
public NotifyingIterator(Iterator it) {
super(it);
}
public void remove() {
synchronized (lock) {
iterator.remove();
lock.notifyAll();
}
}
}
}