| /* |
| * Copyright (C) 2011, Google Inc. |
| * and other copyright owners as documented in the project's IP log. |
| * |
| * This program and the accompanying materials are made available |
| * under the terms of the Eclipse Distribution License v1.0 which |
| * accompanies this distribution, is reproduced below, and is |
| * available at http://www.eclipse.org/org/documents/edl-v10.php |
| * |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or |
| * without modification, are permitted provided that the following |
| * conditions are met: |
| * |
| * - Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * |
| * - 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. |
| * |
| * - Neither the name of the Eclipse Foundation, Inc. nor the |
| * names of its contributors may be used to endorse or promote |
| * products derived from this software without specific prior |
| * written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND |
| * CONTRIBUTORS "AS IS" AND ANY EXPRESS 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 COPYRIGHT OWNER OR |
| * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 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. |
| */ |
| |
| package org.eclipse.jgit.storage.dht; |
| |
| import java.util.concurrent.CountDownLatch; |
| import java.util.concurrent.TimeUnit; |
| import java.util.concurrent.TimeoutException; |
| |
| /** |
| * Helper to implement a synchronous method in terms of an asynchronous one. |
| * <p> |
| * Implementors can use this type to wait for an asynchronous computation to |
| * complete on a background thread by passing the Sync instance as though it |
| * were the AsyncCallback: |
| * |
| * <pre> |
| * Sync<T> sync = Sync.create(); |
| * async(..., sync); |
| * return sync.get(timeout, TimeUnit.MILLISECONDS); |
| * </pre> |
| * |
| * @param <T> |
| * type of value object. |
| */ |
| public abstract class Sync<T> implements AsyncCallback<T> { |
| private static final Sync<?> NONE = new Sync<Object>() { |
| public void onSuccess(Object result) { |
| // Discard |
| } |
| |
| public void onFailure(DhtException error) { |
| // Discard |
| } |
| |
| @Override |
| public Object get(long timeout, TimeUnit unit) throws DhtException, |
| InterruptedException, TimeoutException { |
| return null; |
| } |
| }; |
| |
| /** |
| * Helper method to create a new sync object. |
| * |
| * @param <T> |
| * type of value object. |
| * @return a new instance. |
| */ |
| public static <T> Sync<T> create() { |
| return new Value<T>(); |
| } |
| |
| /** |
| * Singleton callback that ignores onSuccess, onFailure. |
| * |
| * @param <T> |
| * type of value object. |
| * @return callback that discards all results. |
| */ |
| @SuppressWarnings("unchecked") |
| public static <T> Sync<T> none() { |
| return (Sync<T>) NONE; |
| } |
| |
| /** |
| * Wait for the asynchronous operation to complete. |
| * <p> |
| * To prevent application deadlock, waiting can only be performed with the |
| * supplied timeout. |
| * |
| * @param timeout |
| * amount of time to wait before failing. |
| * @return the returned value. |
| * @throws DhtException |
| * the asynchronous operation failed. |
| * @throws InterruptedException |
| * the current thread was interrupted before the operation |
| * completed. |
| * @throws TimeoutException |
| * the timeout elapsed before the operation completed. |
| */ |
| public T get(Timeout timeout) throws DhtException, InterruptedException, |
| TimeoutException { |
| return get(timeout.getTime(), timeout.getUnit()); |
| } |
| |
| /** |
| * Wait for the asynchronous operation to complete. |
| * <p> |
| * To prevent application deadlock, waiting can only be performed with the |
| * supplied timeout. |
| * |
| * @param timeout |
| * amount of time to wait before failing. |
| * @param unit |
| * units of {@code timeout}. For example |
| * {@link TimeUnit#MILLISECONDS}. |
| * @return the returned value. |
| * @throws DhtException |
| * the asynchronous operation failed. |
| * @throws InterruptedException |
| * the current thread was interrupted before the operation |
| * completed. |
| * @throws TimeoutException |
| * the timeout elapsed before the operation completed. |
| */ |
| public abstract T get(long timeout, TimeUnit unit) throws DhtException, |
| InterruptedException, TimeoutException; |
| |
| private static class Value<T> extends Sync<T> { |
| |
| private final CountDownLatch wait = new CountDownLatch(1); |
| |
| private T data; |
| |
| private DhtException error; |
| |
| /** |
| * Wait for the asynchronous operation to complete. |
| * <p> |
| * To prevent application deadlock, waiting can only be performed with |
| * the supplied timeout. |
| * |
| * @param timeout |
| * amount of time to wait before failing. |
| * @param unit |
| * units of {@code timeout}. For example |
| * {@link TimeUnit#MILLISECONDS}. |
| * @return the returned value. |
| * @throws DhtException |
| * the asynchronous operation failed. |
| * @throws InterruptedException |
| * the current thread was interrupted before the operation |
| * completed. |
| * @throws TimeoutException |
| * the timeout elapsed before the operation completed. |
| */ |
| public T get(long timeout, TimeUnit unit) throws DhtException, |
| InterruptedException, TimeoutException { |
| if (wait.await(timeout, unit)) { |
| if (error != null) |
| throw error; |
| return data; |
| } |
| throw new TimeoutException(); |
| } |
| |
| public void onSuccess(T obj) { |
| data = obj; |
| wait.countDown(); |
| } |
| |
| public void onFailure(DhtException err) { |
| error = err; |
| wait.countDown(); |
| } |
| } |
| } |