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/*******************************************************************************
* Copyright (c) 2012 Tilera Corporation and others.
*
* This program and the accompanying materials
* are made available under the terms of the Eclipse Public License 2.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/legal/epl-2.0/
*
* SPDX-License-Identifier: EPL-2.0
*
* Contributors:
* William R. Swanson (Tilera Corporation)
*******************************************************************************/
package org.eclipse.cdt.visualizer.ui.util;
import java.util.concurrent.Callable;
/**
* Runnable object that returns a result object.
*
* This is like Future<V> from the concurrent package,
* but with a few less bells and whistles.
*
* Intended to be used, for example, as follows:
*
* RunnableWithResult<X> runnable = new RunnableWithResult<X>() {
* public X call() {
* ... do work, return an X object ...
* }
* }
*
* Thread thread = new Thread(runnable);
* thread.start();
* X result = runnable.getResult(0);
*
* or, to run it on the UI thread...
*
* GUIUtils.execAndWait(runnable);
* X result = runnable.getResult(0);
*
* Note: if you're invoking this from the UI thread,
* it's important to use execAndWait(), so that the runnable
* gets a turn on the event loop, otherwise you'll hang the UI!
*
*/
public class RunnableWithResult<V>
implements Runnable, Callable<V>
{
// --- members ---
/** Result to return */
protected V m_result = null;
/** Whether run() has completed */
protected boolean m_done = false;
// --- constructors/destructors ---
/** Constructor. */
public RunnableWithResult() {
}
/** Dispose method. */
public void dispose() {
m_result = null;
}
// --- accessors ---
/** Sets result value */
public void setResult(V result) {
m_result = result;
}
/** Gets result value. */
public V getResult() {
return m_result;
}
// --- Runnable implementation ---
/** Run method.
* Derived types should override call() rather than this method.
*/
public void run() {
m_done = false;
setResult(call());
m_done = true;
synchronized (this) {
notifyAll();
}
}
// --- Callable implementation ---
/** Method that returns the value.
* Default implementation returns null.
*/
public V call() {
return null;
}
// --- methods ---
/** Waits for result and returns it. */
public V waitForResult() {
return waitForResult(0, null);
}
/** Waits for result and returns it. */
public V waitForResult(long timeout) {
return waitForResult(timeout, null);
}
/** Waits for result and returns it.
* Returns null if specified timeout is exceeded.
*/
public V waitForResult(long timeout, V defaultValue) {
V result = defaultValue;
try {
if (timeout == 0) {
// wait forever
// (guard against spurious thread wakeup -- see wait() Javadoc)
while (! m_done) {
synchronized (this) {
this.wait(0);
}
}
}
else {
// wait until specified timeout
// (guard against spurious thread wakeup -- see wait() Javadoc)
long then = now();
long waitstep = timeout / 10;
if (waitstep == 0) waitstep = 1;
do {
synchronized (this) {
this.wait(waitstep);
}
}
while (! m_done && ((now() - then) < timeout));
}
}
catch (InterruptedException e) {
}
if (m_done) result = getResult();
return result;
}
/** Returns current time in milliseconds. */
protected static long now() {
return System.currentTimeMillis();
}
}
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