org.eclipse.jetty.util.CountingCallback Maven / Gradle / Ivy
//
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// Copyright (c) 1995-2022 Mort Bay Consulting Pty Ltd and others.
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.opensource.org/licenses/apache2.0.php
//
// You may elect to redistribute this code under either of these licenses.
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//
package org.eclipse.jetty.util;
import java.util.concurrent.atomic.AtomicInteger;
/**
* A callback wrapper that succeeds the wrapped callback when the count is
* reached, or on first failure.
* This callback is particularly useful when an async operation is split
* into multiple parts, for example when an original byte buffer that needs
* to be written, along with a callback, is split into multiple byte buffers,
* since it allows the original callback to be wrapped and notified only when
* the last part has been processed.
* Example:
*
* public void process(EndPoint endPoint, ByteBuffer buffer, Callback callback)
* {
* ByteBuffer[] buffers = split(buffer);
* CountCallback countCallback = new CountCallback(callback, buffers.length);
* endPoint.write(countCallback, buffers);
* }
*
*/
public class CountingCallback extends Callback.Nested
{
private final AtomicInteger count;
public CountingCallback(Callback callback, int count)
{
super(callback);
if (count < 1)
throw new IllegalArgumentException();
this.count = new AtomicInteger(count);
}
@Override
public void succeeded()
{
// Forward success on the last success.
while (true)
{
int current = count.get();
// Already completed ?
if (current == 0)
return;
if (count.compareAndSet(current, current - 1))
{
if (current == 1)
super.succeeded();
return;
}
}
}
@Override
public void failed(Throwable failure)
{
// Forward failure on the first failure.
while (true)
{
int current = count.get();
// Already completed ?
if (current == 0)
return;
if (count.compareAndSet(current, 0))
{
super.failed(failure);
return;
}
}
}
@Override
public String toString()
{
return String.format("%s@%x", getClass().getSimpleName(), hashCode());
}
}