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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
/**
* @author Oleg V. Khaschansky
* @version $Revision$
*/
/*
* Created on 18.01.2005
*/
package org.apache.harmony.awt.gl.image;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
/**
* This class provides functionality for simultaneous loading of
* several images and running animation.
*/
public class ImageLoader extends Thread {
// Contains ImageLoader objects
// and queue of image sources waiting to be loaded
static class ImageLoadersStorage {
private static final int MAX_THREADS = 5;
private static final int TIMEOUT = 4000;
static ImageLoadersStorage instance;
List<DecodingImageSource> queue = new LinkedList<DecodingImageSource>();
List<Thread> loaders = new ArrayList<Thread>(MAX_THREADS);
private int freeLoaders;
private ImageLoadersStorage() {}
static ImageLoadersStorage getStorage() {
if (instance == null) {
instance = new ImageLoadersStorage();
}
return instance;
}
}
ImageLoader() {
super();
setDaemon(true);
}
/**
* This method creates a new thread which is able to load an image
* or run animation (if the number of existing loader threads does not
* exceed the limit).
*/
private static void createLoader() {
final ImageLoadersStorage storage = ImageLoadersStorage.getStorage();
synchronized(storage.loaders) {
if (storage.loaders.size() < ImageLoadersStorage.MAX_THREADS) {
AccessController.doPrivileged(
new PrivilegedAction<Void>() {
public Void run() {
ImageLoader loader = new ImageLoader();
storage.loaders.add(loader);
loader.start();
return null;
}
});
}
}
}
/**
* Adds a new image source to the queue and starts a new loader
* thread if required
* @param imgSrc - image source
*/
public static void addImageSource(DecodingImageSource imgSrc) {
ImageLoadersStorage storage = ImageLoadersStorage.getStorage();
synchronized(storage.queue) {
if (!storage.queue.contains(imgSrc)) {
storage.queue.add(imgSrc);
}
if (storage.freeLoaders == 0) {
createLoader();
}
storage.queue.notify();
}
}
/**
* Waits for a new ImageSource until timout expires.
* Loader thread will terminate after returning from this method
* if timeout expired and image source was not picked up from the queue.
* @return image source picked up from the queue or null if timeout expired
*/
private static DecodingImageSource getWaitingImageSource() {
ImageLoadersStorage storage = ImageLoadersStorage.getStorage();
synchronized(storage.queue) {
DecodingImageSource isrc = null;
if (storage.queue.size() == 0) {
try {
storage.freeLoaders++;
storage.queue.wait(ImageLoadersStorage.TIMEOUT);
} catch (InterruptedException e) {
return null;
} finally {
storage.freeLoaders--;
}
}
if (storage.queue.size() > 0) {
isrc = storage.queue.get(0);
storage.queue.remove(0);
}
return isrc;
}
}
/**
* Entry point of the loader thread. Picks up image sources and
* runs decoders for them while there are available image sources in the queue.
* If there are no and timeout expires it terminates.
*/
@Override
public void run() {
ImageLoadersStorage storage = ImageLoadersStorage.getStorage();
try {
while (storage.loaders.contains(this)) {
Thread.interrupted(); // Reset the interrupted flag
DecodingImageSource isrc = getWaitingImageSource();
if (isrc != null) {
try {
isrc.load();
} catch (Exception e) {
e.printStackTrace();
}
} else {
break; // Don't wait if timeout expired - terminate loader
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
synchronized(storage.loaders) {
storage.loaders.remove(Thread.currentThread());
}
}
}
/**
* Removes current thread from loaders (so we are able
* to create more loaders) and decreases its priority.
*/
static void beginAnimation() {
ImageLoadersStorage storage = ImageLoadersStorage.getStorage();
Thread currThread = Thread.currentThread();
synchronized(storage) {
storage.loaders.remove(currThread);
if (storage.freeLoaders < storage.queue.size()) {
createLoader();
}
}
currThread.setPriority(Thread.MIN_PRIORITY);
}
/**
* Sends the current thread to wait for the new images to load
* if there are free placeholders for loaders
*/
static void endAnimation() {
ImageLoadersStorage storage = ImageLoadersStorage.getStorage();
Thread currThread = Thread.currentThread();
synchronized(storage) {
if (storage.loaders.size() < ImageLoadersStorage.MAX_THREADS &&
!storage.loaders.contains(currThread)
) {
storage.loaders.add(currThread);
}
}
currThread.setPriority(Thread.NORM_PRIORITY);
}
}
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