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/*
* Copyright (c) 2010, 2020 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package org.glassfish.grizzly.impl;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.concurrent.locks.AbstractQueuedSynchronizer;
import org.glassfish.grizzly.CompletionHandler;
/**
* Safe {@link FutureImpl} implementation.
*
* (Based on the JDK {@link java.util.concurrent.FutureTask})
*
* @see Future
*/
@SuppressWarnings("deprecation")
public class SafeFutureImpl implements FutureImpl {
private final Object chSync = new Object();
private Set> completionHandlers;
/**
* {@inheritDoc}
*/
@Override
public void addCompletionHandler(final CompletionHandler completionHandler) {
if (isDone()) {
notifyCompletionHandler(completionHandler);
} else {
synchronized (chSync) {
if (!isDone()) {
if (completionHandlers == null) {
completionHandlers = new HashSet<>(2);
}
completionHandlers.add(completionHandler);
return;
}
}
notifyCompletionHandler(completionHandler);
}
}
/**
* Construct {@link SafeFutureImpl}.
*/
@SuppressWarnings("unchecked")
public static SafeFutureImpl create() {
return new SafeFutureImpl<>();
}
/**
* Creates SafeFutureImpl
*/
@SuppressWarnings("unchecked")
public SafeFutureImpl() {
sync = new Sync();
}
/**
* Set the result value and notify about operation completion.
*
* @param result the result value
*/
@Override
public void result(R result) {
sync.innerSet(result);
}
/**
* Notify about the failure, occurred during asynchronous operation execution.
*
* @param failure
*/
@Override
public void failure(Throwable failure) {
sync.innerSetException(failure);
}
@Override
public void markForRecycle(boolean recycleResult) {
}
@Override
public void recycle(boolean recycleResult) {
}
@Override
public void recycle() {
}
@Override
public R getResult() {
if (isDone()) {
try {
return get();
} catch (Throwable ignored) {
}
}
return null;
}
/**
* The method is called when this SafeFutureImpl is marked as completed. Subclasses can override this method.
*/
protected void onComplete() {
}
/**
* Notify registered {@link CompletionHandler}s about the result.
*/
private void notifyCompletionHandlers() {
assert isDone();
final Set> localSet;
synchronized (chSync) {
if (completionHandlers == null) {
return;
}
localSet = completionHandlers;
completionHandlers = null;
}
final boolean isCancelled = isCancelled();
final R result = sync.result;
final Throwable error = sync.exception;
for (Iterator> it = localSet.iterator(); it.hasNext();) {
final CompletionHandler completionHandler = it.next();
it.remove();
try {
if (isCancelled) {
completionHandler.cancelled();
} else if (error != null) {
completionHandler.failed(error);
} else {
completionHandler.completed(result);
}
} catch (Exception ignored) {
}
}
}
/**
* Notify single {@link CompletionHandler} about the result.
*/
private void notifyCompletionHandler(final CompletionHandler completionHandler) {
if (isCancelled()) {
completionHandler.cancelled();
} else {
try {
final R result = get();
try {
completionHandler.completed(result);
} catch (Exception ignored) {
}
} catch (ExecutionException e) {
completionHandler.failed(e.getCause());
} catch (Exception e) {
completionHandler.failed(e);
}
}
}
// FROM FUTURETASK =========================================================
/**
* Synchronization control for FutureTask
*/
private final Sync sync;
/**
* {@inheritDoc}
*/
@Override
public boolean isCancelled() {
return sync.innerIsCancelled();
}
/**
* {@inheritDoc}
*/
@Override
public boolean isDone() {
return sync.ranOrCancelled();
}
/**
* {@inheritDoc}
*/
@Override
public boolean cancel(boolean mayInterruptIfRunning) {
return sync.innerCancel(mayInterruptIfRunning);
}
/**
* @throws CancellationException {@inheritDoc}
*/
@Override
public R get() throws InterruptedException, ExecutionException {
return sync.innerGet();
}
/**
* @throws CancellationException {@inheritDoc}
*/
@Override
public R get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
return sync.innerGet(unit.toNanos(timeout));
}
/**
* Protected method invoked when this task transitions to state isDone (whether normally or via cancellation).
* The default implementation does nothing. Subclasses may override this method to invoke completion callbacks or
* perform bookkeeping. Note that you can query status inside the implementation of this method to determine whether
* this task has been cancelled.
*/
protected void done() {
notifyCompletionHandlers();
onComplete();
}
/**
* Synchronization control for FutureTask. Note that this must be a non-static inner class in order to invoke the
* protected done method. For clarity, all inner class support methods are same as outer, prefixed with
* "inner".
*
* Uses AQS sync state to represent run status
*/
private final class Sync extends AbstractQueuedSynchronizer {
private static final long serialVersionUID = -7828117401763700385L;
/**
* State value representing that task is ready to run
*/
private static final int READY = 0;
/**
* State value representing that result/exception is being set
*/
private static final int RESULT = 1;
/**
* State value representing that task ran
*/
private static final int RAN = 2;
/**
* State value representing that task was cancelled
*/
private static final int CANCELLED = 3;
/**
* The result to return from get()
*/
private R result;
/**
* The exception to throw from get()
*/
private Throwable exception;
private boolean ranOrCancelled() {
return (getState() & (RAN | CANCELLED)) != 0;
}
/**
* Implements AQS base acquire to succeed if ran or cancelled
*/
@Override
protected int tryAcquireShared(int ignore) {
return ranOrCancelled() ? 1 : -1;
}
/**
* Implements AQS base release to always signal after setting final done status by nulling runner thread.
*/
@Override
protected boolean tryReleaseShared(int ignore) {
return true;
}
boolean innerIsCancelled() {
return getState() == CANCELLED;
}
R innerGet() throws InterruptedException, ExecutionException {
acquireSharedInterruptibly(0);
if (getState() == CANCELLED) {
throw new CancellationException();
}
if (exception != null) {
throw new ExecutionException(exception);
}
return result;
}
R innerGet(long nanosTimeout) throws InterruptedException, ExecutionException, TimeoutException {
if (!tryAcquireSharedNanos(0, nanosTimeout)) {
throw new TimeoutException();
}
if (getState() == CANCELLED) {
throw new CancellationException();
}
if (exception != null) {
throw new ExecutionException(exception);
}
return result;
}
void innerSet(R v) {
if (compareAndSetState(READY, RESULT)) {
result = v;
setState(RAN);
releaseShared(0);
done();
}
}
void innerSetException(Throwable t) {
if (compareAndSetState(READY, RESULT)) {
exception = t;
setState(RAN);
releaseShared(0);
done();
}
}
boolean innerCancel(boolean mayInterruptIfRunning) {
if (compareAndSetState(READY, CANCELLED)) {
releaseShared(0);
done();
return true;
}
return false;
}
}
}
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