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package de.lmu.ifi.dbs.elki.visualization.visualizers.thumbs;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2015
Ludwig-Maximilians-Universität München
Lehr- und Forschungseinheit für Datenbanksysteme
ELKI Development Team
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.util.Queue;
import java.util.concurrent.ConcurrentLinkedQueue;
/**
* Thread to render thumbnails in the background.
*
* @author Erich Schubert
* @since 0.4.0
*
* @apiviz.uses Listener oneway - - signals
*/
public class ThumbnailThread extends Thread {
/**
* Queue of thumbnails to generate.
*/
private Queue<Task> queue = new ConcurrentLinkedQueue<>();
/**
* Flag to signal shutdown.
*/
private boolean shutdown = false;
/**
* The static thumbnail thread.
*/
private static ThumbnailThread THREAD = null;
/**
* Queue a thumbnail task in a global thumbnail thread.
*
* @param callback Callback
*/
public synchronized static Task QUEUE(Listener callback) {
final Task task = new Task(callback);
if(THREAD != null) {
// TODO: synchronization?
if(THREAD.isAlive()) {
THREAD.queue(task);
return task;
}
}
THREAD = new ThumbnailThread();
THREAD.queue(task);
THREAD.start();
return task;
}
/**
* Remove a pending task from the queue.
*
* @param task Task to remove.
*/
public static void UNQUEUE(Task task) {
if(THREAD != null) {
synchronized(THREAD) {
THREAD.queue.remove(task);
}
}
}
/**
* Shutdown the thumbnailer thread.
*/
public static synchronized void SHUTDOWN() {
if(THREAD != null && THREAD.isAlive()) {
THREAD.shutdown();
}
}
/**
* Queue a new thumbnail task.
*
* @param task Thumbnail task
*/
private void queue(Task task) {
this.queue.add(task);
}
/**
* Generate a single Thumbnail.
*
* @param ti Visualization task
*/
private void generateThumbnail(Task ti) {
ti.callback.doThumbnail();
}
@Override
public void run() {
while(!queue.isEmpty() && !shutdown) {
generateThumbnail(queue.poll());
}
}
/**
* Set the shutdown flag.
*/
private void shutdown() {
this.shutdown = true;
queue.clear();
}
/**
* A single thumbnailer task.
*
* @author Erich Schubert
*
* @apiviz.exclude
*/
public static class Task {
/**
* Runnable to call back
*/
Listener callback;
/**
* Constructor.
*
* @param callback Callback when complete
*/
public Task(Listener callback) {
super();
this.callback = callback;
}
}
/**
* Listener interface for completed thumbnails.
*
* @author Erich Schubert
*/
public interface Listener {
/**
* Callback when to (re-)compute the thumbnail.
*/
public void doThumbnail();
}
}
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