1 /*
2 * Copyright (c) 2011, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 /*
27 * To change this template, choose Tools | Templates
28 * and open the template in the editor.
29 */
30
31 package com.sun.webkit;
32
33 import java.lang.ref.ReferenceQueue;
34 import java.lang.ref.WeakReference;
35 import java.security.PrivilegedAction;
36 import java.util.Arrays;
37 import java.util.Collection;
38 import java.util.HashSet;
39 import java.util.Set;
40 import java.util.concurrent.LinkedBlockingQueue;
41
42 /**
43 * This class is used for registering and disposing the native
44 * data associated with java objects.
45 *
46 * The object can register itself by calling the addRecord method and
47 * providing a descendant of the DisposerRecord class with overridden
48 * dispose() method.
49 *
50 * When the object becomes unreachable, the dispose() method
51 * of the associated DisposerRecord object will be called.
52 *
53 * @see DisposerRecord
54 */
55 public final class Disposer implements Runnable {
56 private static final ReferenceQueue queue = new ReferenceQueue();
57 private static final Disposer disposerInstance = new Disposer();
58 private static final Set<WeakDisposerRecord> records =
59 new HashSet<WeakDisposerRecord>();
60
61 static {
62 java.security.AccessController.doPrivileged((PrivilegedAction<Void>) () -> {
63 /*
64 * The thread must be a member of a thread group
65 * which will not get GCed before VM exit.
66 * Make its parent the top-level thread group.
67 */
68 ThreadGroup tg = Thread.currentThread().getThreadGroup();
69 for (ThreadGroup tgn = tg;
70 tgn != null;
71 tg = tgn, tgn = tg.getParent());
72
73 Thread t = new Thread(tg, disposerInstance, "Disposer");
74 t.setDaemon(true);
75 t.setPriority(Thread.MAX_PRIORITY);
76 t.start();
77 return null;
78 });
79 }
80
81 /**
82 * Registers the object and the native data for later disposal.
83 * @param target Object to be registered
84 * @param rec the associated DisposerRecord object
85 * @see DisposerRecord
86 */
87 public static void addRecord(Object target, DisposerRecord rec) {
88 disposerInstance.add(target, rec);
89 }
90
91 /**
92 * Performs the actual registration of the target object to be disposed.
93 * @param target Object to be registered
94 * @param rec the associated DisposerRecord object
95 * @see DisposerRecord
96 */
97 private synchronized void add(Object target, DisposerRecord rec) {
98 records.add(new WeakDisposerRecord(target, rec));
99 }
100
101 public void run() {
102 while (true) {
103 try {
104 WeakDisposerRecord obj = (WeakDisposerRecord) queue.remove();
105 obj.clear();
106 DisposerRunnable.getInstance().enqueue(obj);
107 } catch (Exception e) {
108 System.out.println("Exception while removing reference: " + e);
109 e.printStackTrace();
110 }
111 }
112 }
113
114 private static final class DisposerRunnable implements Runnable {
115 private static final DisposerRunnable theInstance = new DisposerRunnable();
116
117 private static DisposerRunnable getInstance() {
118 return theInstance;
119 }
120
121 private boolean isRunning = false;
122 private final Object disposerLock = new Object();
123 private final LinkedBlockingQueue<WeakDisposerRecord> disposerQueue
124 = new LinkedBlockingQueue<WeakDisposerRecord>();
125
126 private void enqueueAll(Collection<WeakDisposerRecord> objs) {
127 synchronized (disposerLock) {
128 disposerQueue.addAll(objs);
129 if (!isRunning) {
130 Invoker.getInvoker().invokeOnEventThread(this);
131 isRunning = true;
132 }
133 }
134 }
135
136 private void enqueue(WeakDisposerRecord obj) {
137 enqueueAll(Arrays.asList(obj));
138 }
139
140 @Override public void run() {
141 while (true) {
142 WeakDisposerRecord obj;
143 synchronized (disposerLock) {
144 obj = disposerQueue.poll();
145 if (obj == null) {
146 isRunning = false;
147 break;
148 }
149 }
150 // Check if the object has not yet been removed & disposed.
151 if (records.contains(obj)) {
152 records.remove(obj);
153 obj.dispose();
154 }
155 }
156 }
157 }
158
159 public static class WeakDisposerRecord
160 extends WeakReference
161 implements DisposerRecord
162 {
163 protected WeakDisposerRecord(Object referent) {
164 super(referent, Disposer.queue);
165 this.record = null;
166 }
167
168 private WeakDisposerRecord(Object referent, DisposerRecord record) {
169 super(referent, Disposer.queue);
170 this.record = record;
171 }
172
173 private final DisposerRecord record;
174
175 @Override
176 public void dispose() {
177 record.dispose();
178 }
179 }
180 }