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371 lines
13 KiB
Java
371 lines
13 KiB
Java
/*
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* Copyright (c) 1995, 2015, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package sun.awt.image;
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import java.util.Vector;
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import sun.awt.AppContext;
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/**
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* An ImageFetcher is a thread used to fetch ImageFetchable objects.
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* Once an ImageFetchable object has been fetched, the ImageFetcher
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* thread may also be used to animate it if necessary, via the
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* startingAnimation() / stoppingAnimation() methods.
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*
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* There can be up to FetcherInfo.MAX_NUM_FETCHERS_PER_APPCONTEXT
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* ImageFetcher threads for each AppContext. A per-AppContext queue
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* of ImageFetchables is used to track objects to fetch.
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*
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* @author Jim Graham
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* @author Fred Ecks
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*/
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class ImageFetcher extends Thread {
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static final int HIGH_PRIORITY = 8;
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static final int LOW_PRIORITY = 3;
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static final int ANIM_PRIORITY = 2;
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static final int TIMEOUT = 5000; // Time in milliseconds to wait for an
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// ImageFetchable to be added to the
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// queue before an ImageFetcher dies
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/**
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* We must only call the 5 args super() constructor passing
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* in "false" to indicate to not inherit locals.
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*/
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private ImageFetcher() {
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throw new UnsupportedOperationException("Must erase locals");
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}
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/**
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* Constructor for ImageFetcher -- only called by add() below.
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*/
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private ImageFetcher(ThreadGroup threadGroup, int index) {
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super(threadGroup, null, "Image Fetcher " + index, 0, false);
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setDaemon(true);
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}
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/**
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* Adds an ImageFetchable to the queue of items to fetch. Instantiates
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* a new ImageFetcher if it's reasonable to do so.
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* If there is no available fetcher to process an ImageFetchable, then
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* reports failure to caller.
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*/
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public static boolean add(ImageFetchable src) {
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final FetcherInfo info = FetcherInfo.getFetcherInfo();
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synchronized(info.waitList) {
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if (!info.waitList.contains(src)) {
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info.waitList.addElement(src);
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if (info.numWaiting == 0 &&
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info.numFetchers < info.fetchers.length) {
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createFetchers(info);
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}
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/* Creation of new fetcher may fail due to high vm load
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* or some other reason.
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* If there is already exist, but busy, fetcher, we leave
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* the src in queue (it will be handled by existing
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* fetcher later).
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* Otherwise, we report failure: there is no fetcher
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* to handle the src.
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*/
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if (info.numFetchers > 0) {
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info.waitList.notify();
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} else {
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info.waitList.removeElement(src);
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return false;
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}
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}
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}
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return true;
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}
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/**
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* Removes an ImageFetchable from the queue of items to fetch.
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*/
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public static void remove(ImageFetchable src) {
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final FetcherInfo info = FetcherInfo.getFetcherInfo();
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synchronized(info.waitList) {
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if (info.waitList.contains(src)) {
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info.waitList.removeElement(src);
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}
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}
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}
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/**
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* Checks to see if the given thread is one of the ImageFetchers.
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*/
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public static boolean isFetcher(Thread t) {
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final FetcherInfo info = FetcherInfo.getFetcherInfo();
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synchronized(info.waitList) {
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for (int i = 0; i < info.fetchers.length; i++) {
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if (info.fetchers[i] == t) {
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return true;
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}
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}
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}
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return false;
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}
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/**
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* Checks to see if the current thread is one of the ImageFetchers.
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*/
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public static boolean amFetcher() {
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return isFetcher(Thread.currentThread());
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}
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/**
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* Returns the next ImageFetchable to be processed. If TIMEOUT
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* elapses in the mean time, or if the ImageFetcher is interrupted,
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* null is returned.
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*/
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private static ImageFetchable nextImage() {
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final FetcherInfo info = FetcherInfo.getFetcherInfo();
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synchronized(info.waitList) {
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ImageFetchable src = null;
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long end = System.currentTimeMillis() + TIMEOUT;
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while (src == null) {
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while (info.waitList.size() == 0) {
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long now = System.currentTimeMillis();
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if (now >= end) {
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return null;
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}
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try {
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info.numWaiting++;
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info.waitList.wait(end - now);
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} catch (InterruptedException e) {
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// A normal occurrence as an AppContext is disposed
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return null;
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} finally {
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info.numWaiting--;
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}
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}
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src = info.waitList.elementAt(0);
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info.waitList.removeElement(src);
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}
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return src;
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}
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}
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/**
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* The main run() method of an ImageFetcher Thread. Calls fetchloop()
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* to do the work, then removes itself from the array of ImageFetchers.
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*/
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public void run() {
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final FetcherInfo info = FetcherInfo.getFetcherInfo();
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try {
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fetchloop();
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} catch (Exception e) {
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e.printStackTrace();
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} finally {
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synchronized(info.waitList) {
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Thread me = Thread.currentThread();
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for (int i = 0; i < info.fetchers.length; i++) {
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if (info.fetchers[i] == me) {
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info.fetchers[i] = null;
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info.numFetchers--;
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}
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}
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}
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}
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}
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/**
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* The main ImageFetcher loop. Repeatedly calls nextImage(), and
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* fetches the returned ImageFetchable objects until nextImage()
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* returns null.
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*/
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private void fetchloop() {
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Thread me = Thread.currentThread();
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while (isFetcher(me)) {
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// we're ignoring the return value and just clearing
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// the interrupted flag, instead of bailing out if
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// the fetcher was interrupted, as we used to,
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// because there may be other images waiting
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// to be fetched (see 4789067)
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Thread.interrupted();
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me.setPriority(HIGH_PRIORITY);
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ImageFetchable src = nextImage();
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if (src == null) {
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return;
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}
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try {
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src.doFetch();
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} catch (Exception e) {
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System.err.println("Uncaught error fetching image:");
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e.printStackTrace();
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}
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stoppingAnimation(me);
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}
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}
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/**
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* Recycles this ImageFetcher thread as an image animator thread.
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* Removes this ImageFetcher from the array of ImageFetchers, and
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* resets the thread name to "ImageAnimator".
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*/
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static void startingAnimation() {
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final FetcherInfo info = FetcherInfo.getFetcherInfo();
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Thread me = Thread.currentThread();
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synchronized(info.waitList) {
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for (int i = 0; i < info.fetchers.length; i++) {
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if (info.fetchers[i] == me) {
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info.fetchers[i] = null;
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info.numFetchers--;
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me.setName("Image Animator " + i);
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if(info.waitList.size() > info.numWaiting) {
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createFetchers(info);
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}
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return;
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}
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}
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}
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me.setPriority(ANIM_PRIORITY);
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me.setName("Image Animator");
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}
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/**
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* Returns this image animator thread back to service as an ImageFetcher
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* if possible. Puts it back into the array of ImageFetchers and sets
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* the thread name back to "Image Fetcher". If there are already the
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* maximum number of ImageFetchers, this method simply returns, and
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* fetchloop() will drop out when it sees that this thread isn't one of
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* the ImageFetchers, and this thread will die.
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*/
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private static void stoppingAnimation(Thread me) {
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final FetcherInfo info = FetcherInfo.getFetcherInfo();
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synchronized(info.waitList) {
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int index = -1;
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for (int i = 0; i < info.fetchers.length; i++) {
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if (info.fetchers[i] == me) {
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return;
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}
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if (info.fetchers[i] == null) {
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index = i;
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}
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}
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if (index >= 0) {
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info.fetchers[index] = me;
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info.numFetchers++;
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me.setName("Image Fetcher " + index);
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return;
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}
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}
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}
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/**
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* Create and start ImageFetcher threads in the appropriate ThreadGroup.
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*/
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private static void createFetchers(final FetcherInfo info) {
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// We need to instantiate a new ImageFetcher thread.
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// First, figure out which ThreadGroup we'll put the
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// new ImageFetcher into
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final AppContext appContext = AppContext.getAppContext();
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ThreadGroup threadGroup = appContext.getThreadGroup();
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ThreadGroup fetcherThreadGroup;
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try {
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if (threadGroup.getParent() != null) {
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// threadGroup is not the root, so we proceed
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fetcherThreadGroup = threadGroup;
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} else {
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// threadGroup is the root ("system") ThreadGroup.
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// We instead want to use its child: the "main"
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// ThreadGroup. Thus, we start with the current
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// ThreadGroup, and go up the tree until
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// threadGroup.getParent().getParent() == null.
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threadGroup = Thread.currentThread().getThreadGroup();
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ThreadGroup parent = threadGroup.getParent();
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while ((parent != null)
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&& (parent.getParent() != null)) {
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threadGroup = parent;
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parent = threadGroup.getParent();
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}
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fetcherThreadGroup = threadGroup;
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}
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} catch (SecurityException e) {
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// Not allowed access to parent ThreadGroup -- just use
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// the AppContext's ThreadGroup
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fetcherThreadGroup = appContext.getThreadGroup();
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}
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final ThreadGroup fetcherGroup = fetcherThreadGroup;
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java.security.AccessController.doPrivileged(
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new java.security.PrivilegedAction<Object>() {
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public Object run() {
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for (int i = 0; i < info.fetchers.length; i++) {
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if (info.fetchers[i] == null) {
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ImageFetcher f = new ImageFetcher(fetcherGroup, i);
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try {
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f.start();
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info.fetchers[i] = f;
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info.numFetchers++;
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break;
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} catch (Error e) {
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}
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}
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}
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return null;
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}
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});
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return;
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}
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}
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/**
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* The FetcherInfo class encapsulates the per-AppContext ImageFetcher
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* information. This includes the array of ImageFetchers, as well as
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* the queue of ImageFetchable objects.
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*/
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class FetcherInfo {
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static final int MAX_NUM_FETCHERS_PER_APPCONTEXT = 4;
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Thread[] fetchers;
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int numFetchers;
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int numWaiting;
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Vector<ImageFetchable> waitList;
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private FetcherInfo() {
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fetchers = new Thread[MAX_NUM_FETCHERS_PER_APPCONTEXT];
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numFetchers = 0;
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numWaiting = 0;
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waitList = new Vector<>();
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}
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/* The key to put()/get() the FetcherInfo into/from the AppContext. */
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private static final Object FETCHER_INFO_KEY =
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new StringBuffer("FetcherInfo");
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static FetcherInfo getFetcherInfo() {
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AppContext appContext = AppContext.getAppContext();
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synchronized(appContext) {
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FetcherInfo info = (FetcherInfo)appContext.get(FETCHER_INFO_KEY);
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if (info == null) {
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info = new FetcherInfo();
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appContext.put(FETCHER_INFO_KEY, info);
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}
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return info;
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}
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}
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}
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