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/*
* Copyright (C) 2008 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.common.util.concurrent;
import static java.lang.Math.min;
import static java.util.concurrent.TimeUnit.NANOSECONDS;
import com.google.common.annotations.GwtIncompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.FutureTask;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import org.checkerframework.checker.nullness.compatqual.NullableDecl;
/**
* A {@link FutureTask} that also implements the {@link ListenableFuture} interface. Unlike {@code
* FutureTask}, {@code ListenableFutureTask} does not provide an overrideable {@link
* FutureTask#done() done()} method. For similar functionality, call {@link #addListener}.
*
* <p>Few users should use this class. It is intended primarily for those who are implementing an
* {@code ExecutorService}. Most users should call {@link ListeningExecutorService#submit(Callable)
* ListeningExecutorService.submit} on a service obtained from {@link
* MoreExecutors#listeningDecorator}.
*
* @author Sven Mawson
* @since 1.0
*/
@GwtIncompatible
public class ListenableFutureTask<V> extends FutureTask<V> implements ListenableFuture<V> {
// TODO(cpovirk): explore ways of making ListenableFutureTask final. There are some valid reasons
// such as BoundedQueueExecutorService to allow extends but it would be nice to make it final to
// avoid unintended usage.
// The execution list to hold our listeners.
private final ExecutionList executionList = new ExecutionList();
/**
* Creates a {@code ListenableFutureTask} that will upon running, execute the given {@code
* Callable}.
*
* @param callable the callable task
* @since 10.0
*/
public static <V> ListenableFutureTask<V> create(Callable<V> callable) {
return new ListenableFutureTask<V>(callable);
}
/**
* Creates a {@code ListenableFutureTask} that will upon running, execute the given {@code
* Runnable}, and arrange that {@code get} will return the given result on successful completion.
*
* @param runnable the runnable task
* @param result the result to return on successful completion. If you don't need a particular
* result, consider using constructions of the form: {@code ListenableFuture<?> f =
* ListenableFutureTask.create(runnable, null)}
* @since 10.0
*/
public static <V> ListenableFutureTask<V> create(Runnable runnable, @NullableDecl V result) {
return new ListenableFutureTask<V>(runnable, result);
}
ListenableFutureTask(Callable<V> callable) {
super(callable);
}
ListenableFutureTask(Runnable runnable, @NullableDecl V result) {
super(runnable, result);
}
@Override
public void addListener(Runnable listener, Executor exec) {
executionList.add(listener, exec);
}
@CanIgnoreReturnValue
@Override
public V get(long timeout, TimeUnit unit)
throws TimeoutException, InterruptedException, ExecutionException {
long timeoutNanos = unit.toNanos(timeout);
if (timeoutNanos <= OverflowAvoidingLockSupport.MAX_NANOSECONDS_THRESHOLD) {
return super.get(timeout, unit);
}
// Waiting 68 years should be enough for any program.
return super.get(
min(timeoutNanos, OverflowAvoidingLockSupport.MAX_NANOSECONDS_THRESHOLD), NANOSECONDS);
}
/** Internal implementation detail used to invoke the listeners. */
@Override
protected void done() {
executionList.execute();
}
}
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