/*
* Copyright 2003-2005 The Apache Software Foundation
*
* 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 org.apache.commons.collections.buffer;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Collection;
import org.apache.commons.collections.Buffer;
import org.apache.commons.collections.BufferUnderflowException;
/**
* Decorates another <code>Buffer</code> to make {@link #get()} and
* {@link #remove()} block when the <code>Buffer</code> is empty.
* <p>
* If either <code>get</code> or <code>remove</code> is called on an empty
* <code>Buffer</code>, the calling thread waits for notification that
* an <code>add</code> or <code>addAll</code> operation has completed.
* <p>
* When one or more entries are added to an empty <code>Buffer</code>,
* all threads blocked in <code>get</code> or <code>remove</code> are notified.
* There is no guarantee that concurrent blocked <code>get</code> or
* <code>remove</code> requests will be "unblocked" and receive data in the
* order that they arrive.
* <p>
* This class is Serializable from Commons Collections 3.1.
* This class contains an extra field in 3.2, however the serialization
* specification will handle this gracefully.
*
* @author Stephen Colebourne
* @author Janek Bogucki
* @author Phil Steitz
* @author James Carman
* @version $Revision: 348808 $ $Date: 2005-11-24 21:35:09 +0000 (Thu, 24 Nov 2005) $
* @since Commons Collections 3.0
*/
public class BlockingBuffer extends SynchronizedBuffer {
/** Serialization version. */
private static final long serialVersionUID = 1719328905017860541L;
/** The timeout value in milliseconds. */
private final long timeout;
/**
* Factory method to create a blocking buffer.
*
* @param buffer the buffer to decorate, must not be null
* @return a new blocking Buffer
* @throws IllegalArgumentException if buffer is null
*/
public static Buffer decorate(Buffer buffer) {
return new BlockingBuffer(buffer);
}
/**
* Factory method to create a blocking buffer with a timeout value.
*
* @param buffer the buffer to decorate, must not be null
* @param timeoutMillis the timeout value in milliseconds, zero or less for no timeout
* @return a new blocking buffer
* @throws IllegalArgumentException if the buffer is null
* @since Commons Collections 3.2
*/
public static Buffer decorate(Buffer buffer, long timeoutMillis) {
return new BlockingBuffer(buffer, timeoutMillis);
}
//-----------------------------------------------------------------------
/**
* Constructor that wraps (not copies).
*
* @param buffer the buffer to decorate, must not be null
* @throws IllegalArgumentException if the buffer is null
*/
protected BlockingBuffer(Buffer buffer) {
super(buffer);
this.timeout = 0;
}
/**
* Constructor that wraps (not copies).
*
* @param buffer the buffer to decorate, must not be null
* @param timeoutMillis the timeout value in milliseconds, zero or less for no timeout
* @throws IllegalArgumentException if the buffer is null
* @since Commons Collections 3.2
*/
protected BlockingBuffer(Buffer buffer, long timeoutMillis) {
super(buffer);
this.timeout = (timeoutMillis < 0 ? 0 : timeoutMillis);
}
//-----------------------------------------------------------------------
public boolean add(Object o) {
synchronized (lock) {
boolean result = collection.add(o);
lock.notifyAll();
return result;
}
}
public boolean addAll(Collection c) {
synchronized (lock) {
boolean result = collection.addAll(c);
lock.notifyAll();
return result;
}
}
/**
* Gets the next value from the buffer, waiting until an object is
* added if the buffer is empty. This method uses the default timeout
* set in the constructor.
*
* @throws BufferUnderflowException if an interrupt is received
*/
public Object get() {
synchronized (lock) {
while (collection.isEmpty()) {
try {
if (timeout <= 0) {
lock.wait();
} else {
return get(timeout);
}
} catch (InterruptedException e) {
PrintWriter out = new PrintWriter(new StringWriter());
e.printStackTrace(out);
throw new BufferUnderflowException("Caused by InterruptedException: " + out.toString());
}
}
return getBuffer().get();
}
}
/**
* Gets the next value from the buffer, waiting until an object is
* added for up to the specified timeout value if the buffer is empty.
*
* @param timeout the timeout value in milliseconds
* @throws BufferUnderflowException if an interrupt is received
* @throws BufferUnderflowException if the timeout expires
* @since Commons Collections 3.2
*/
public Object get(final long timeout) {
synchronized (lock) {
final long expiration = System.currentTimeMillis() + timeout;
long timeLeft = expiration - System.currentTimeMillis();
while (timeLeft > 0 && collection.isEmpty()) {
try {
lock.wait(timeLeft);
timeLeft = expiration - System.currentTimeMillis();
} catch(InterruptedException e) {
PrintWriter out = new PrintWriter(new StringWriter());
e.printStackTrace(out);
throw new BufferUnderflowException("Caused by InterruptedException: " + out.toString());
}
}
if (collection.isEmpty()) {
throw new BufferUnderflowException("Timeout expired");
}
return getBuffer().get();
}
}
/**
* Removes the next value from the buffer, waiting until an object is
* added if the buffer is empty. This method uses the default timeout
* set in the constructor.
*
* @throws BufferUnderflowException if an interrupt is received
*/
public Object remove() {
synchronized (lock) {
while (collection.isEmpty()) {
try {
if (timeout <= 0) {
lock.wait();
} else {
return remove(timeout);
}
} catch (InterruptedException e) {
PrintWriter out = new PrintWriter(new StringWriter());
e.printStackTrace(out);
throw new BufferUnderflowException("Caused by InterruptedException: " + out.toString());
}
}
return getBuffer().remove();
}
}
/**
* Removes the next value from the buffer, waiting until an object is
* added for up to the specified timeout value if the buffer is empty.
*
* @param timeout the timeout value in milliseconds
* @throws BufferUnderflowException if an interrupt is received
* @throws BufferUnderflowException if the timeout expires
* @since Commons Collections 3.2
*/
public Object remove(final long timeout) {
synchronized (lock) {
final long expiration = System.currentTimeMillis() + timeout;
long timeLeft = expiration - System.currentTimeMillis();
while (timeLeft > 0 && collection.isEmpty()) {
try {
lock.wait(timeLeft);
timeLeft = expiration - System.currentTimeMillis();
} catch(InterruptedException e) {
PrintWriter out = new PrintWriter(new StringWriter());
e.printStackTrace(out);
throw new BufferUnderflowException("Caused by InterruptedException: " + out.toString());
}
}
if (collection.isEmpty()) {
throw new BufferUnderflowException("Timeout expired");
}
return getBuffer().remove();
}
}
}