// // ======================================================================== // Copyright (c) 1995-2017 Mort Bay Consulting Pty. Ltd. // ------------------------------------------------------------------------ // 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. // ======================================================================== // package org.eclipse.jetty.util; import java.util.concurrent.atomic.AtomicInteger; /** * <p>A callback wrapper that succeeds the wrapped callback when the count is * reached, or on first failure.</p> * <p>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.</p> * <p>Example:</p> * <pre> * public void process(EndPoint endPoint, ByteBuffer buffer, Callback callback) * { * ByteBuffer[] buffers = split(buffer); * CountCallback countCallback = new CountCallback(callback, buffers.length); * endPoint.write(countCallback, buffers); * } * </pre> */ public class CountingCallback extends Callback.Nested { private final AtomicInteger count; public CountingCallback(Callback callback, int count) { super(callback); 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()); } }