123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199 |
- /*
- * 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();
- }
- }
- }
|