/*
============================================================================
The Apache Software License, Version 1.1
============================================================================
Copyright (C) 1999-2003 The Apache Software Foundation. All rights reserved.
Redistribution and use in source and binary forms, with or without modifica-
tion, are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice,
this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
3. The end-user documentation included with the redistribution, if any, must
include the following acknowledgment: "This product includes software
developed by the Apache Software Foundation (http://www.apache.org/)."
Alternately, this acknowledgment may appear in the software itself, if
and wherever such third-party acknowledgments normally appear.
4. The names "Jakarta", "Avalon", "Excalibur" and "Apache Software Foundation"
must not be used to endorse or promote products derived from this software
without prior written permission. For written permission, please contact
apache@apache.org.
5. Products derived from this software may not be called "Apache", nor may
"Apache" appear in their name, without prior written permission of the
Apache Software Foundation.
THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
APACHE SOFTWARE FOUNDATION OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLU-
DING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
This software consists of voluntary contributions made by many individuals
on behalf of the Apache Software Foundation. For more information on the
Apache Software Foundation, please see <http://www.apache.org/>.
*/
package org.apache.excalibur.event.impl;
import org.apache.excalibur.event.PreparedEnqueue;
import org.apache.excalibur.event.SinkException;
import org.apache.excalibur.event.SinkFullException;
import EDU.oswego.cs.dl.util.concurrent.ReentrantLock;
/**
* An implementation of the <code>Queue</code> that has a fixed size. Once
* the maximum number of elements are set, this <code>Queue</code> cannot be
* changed.
*
* @author <a href="mailto:bloritsch@apache.org">Berin Loritsch</a>
*
* @deprecated Use the DefaultQueue as it properly supports the EnqueuePredicates
*/
public final class FixedSizeQueue
extends AbstractQueue
{
private final Object[] m_elements;
private final ReentrantLock m_mutex;
private int m_start = 0;
private int m_end = 0;
protected int m_reserve = 0;
/**
* Create a <code>FixedSizedQueue</code> with the specified maximum size.
* The maximum size must be 1 or more.
*
* @param size The maximum number of events the Queue can handle
*/
public FixedSizeQueue( int size )
{
if( size < 1 )
throw new IllegalArgumentException( "Cannot specify an unbounded Queue" );
m_elements = new Object[ size + 1 ];
m_mutex = new ReentrantLock();
}
public int size()
{
int size = 0;
if( m_end < m_start )
{
size = maxSize() - m_start + m_end;
}
else
{
size = m_end - m_start;
}
return size + m_reserve;
}
public int maxSize()
{
return m_elements.length;
}
public PreparedEnqueue prepareEnqueue( final Object[] elements )
throws SinkException
{
PreparedEnqueue enqueue = null;
try
{
m_mutex.acquire();
try
{
if( elements.length + size() > maxSize() )
{
throw new SinkFullException( "Not enough room to enqueue these elements." );
}
enqueue = new FixedSizePreparedEnqueue( this, elements );
}
finally
{
m_mutex.release();
}
}
catch( InterruptedException ie )
{
}
return enqueue;
}
public boolean tryEnqueue( final Object element )
{
boolean success = false;
try
{
m_mutex.acquire();
try
{
if( 1 + size() > maxSize() )
{
return false;
}
addElement( element );
success = true;
}
finally
{
m_mutex.release();
}
}
catch( InterruptedException ie )
{
}
return success;
}
public void enqueue( final Object[] elements )
throws SinkException
{
final int len = elements.length;
try
{
m_mutex.acquire();
try
{
if( elements.length + size() > maxSize() )
{
throw new SinkFullException( "Not enough room to enqueue these elements." );
}
for( int i = 0; i < len; i++ )
{
addElement( elements[ i ] );
}
}
finally
{
m_mutex.release();
}
}
catch( InterruptedException ie )
{
}
}
public void enqueue( final Object element )
throws SinkException
{
try
{
m_mutex.acquire();
try
{
if( 1 + size() > maxSize() )
{
throw new SinkFullException( "Not enough room to enqueue these elements." );
}
addElement( element );
}
finally
{
m_mutex.release();
}
}
catch( InterruptedException ie )
{
}
}
public Object[] dequeue( final int numElements )
{
Object[] elements = EMPTY_ARRAY;
try
{
if( m_mutex.attempt( m_timeout ) )
{
try
{
elements = retrieveElements( Math.min( size(),
numElements ) );
}
finally
{
m_mutex.release();
}
}
}
catch( InterruptedException ie )
{
}
return elements;
}
private final void addElement( Object element )
{
m_elements[ m_end ] = element;
m_end++;
if( m_end >= maxSize() )
{
m_end = 0;
}
}
private final Object removeElement()
{
Object element = m_elements[ m_start ];
if( null != element )
{
m_elements[ m_start ] = null;
m_start++;
if( m_start >= maxSize() )
{
m_start = 0;
}
}
return element;
}
/**
* Removes exactly <code>count</code> elements from the underlying
* element store and returns them as an array of Objects.
* The caller is responsible for synchronizing access to the
* element store and passing the correct value for
* <code>count</code>.
* <p>
* The method can be further optimized by using System.arraycopy
* if it is found to underperform.
*
* @param count number of elements to return
* @return requested number of elements
*/
private final Object[] retrieveElements( int count )
{
Object[] elements = new Object[ count ];
for( int i = 0; i < count; i++ )
{
elements[ i ] = removeElement();
}
return elements;
}
public Object[] dequeueAll()
{
Object[] elements = EMPTY_ARRAY;
try
{
if( m_mutex.attempt( m_timeout ) )
{
try
{
elements = retrieveElements( size() );
}
finally
{
m_mutex.release();
}
}
}
catch( InterruptedException ie )
{
}
return elements;
}
public Object dequeue()
{
Object element = null;
try
{
if( m_mutex.attempt( m_timeout ) )
{
try
{
if( size() > 0 )
{
element = removeElement();
}
}
finally
{
m_mutex.release();
}
}
}
catch( InterruptedException ie )
{
}
return element;
}
private static final class FixedSizePreparedEnqueue implements PreparedEnqueue
{
private final FixedSizeQueue m_parent;
private Object[] m_elements;
private FixedSizePreparedEnqueue( FixedSizeQueue parent, Object[] elements )
{
m_parent = parent;
m_elements = elements;
m_parent.m_reserve += m_elements.length;
}
public void commit()
{
if( null == m_elements )
{
throw new IllegalStateException( "This PreparedEnqueue has already been processed!" );
}
try
{
m_parent.enqueue( m_elements );
m_parent.m_reserve -= m_elements.length;
m_elements = null;
}
catch( Exception e )
{
throw new IllegalStateException( "Default enqueue did not happen--should be impossible" );
// will never happen
}
}
public void abort()
{
if( null == m_elements )
{
throw new IllegalStateException( "This PreparedEnqueue has already been processed!" );
}
m_parent.m_reserve -= m_elements.length;
m_elements = null;
}
}
}