jdk/src/share/classes/sun/java2d/Disposer.java

/*
 * Copyright 2002-2005 Sun Microsystems, Inc.  All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Sun designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Sun in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
 * CA 95054 USA or visit www.sun.com if you need additional information or
 * have any questions.
 */

package sun.java2d;

import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.PhantomReference;
import java.lang.ref.WeakReference;
import java.util.Hashtable;

/**
 * This class is used for registering and disposing the native
 * data associated with java objects.
 *
 * The object can register itself by calling one of the addRecord
 * methods and providing either the pointer to the native disposal
 * method or a descendant of the DisposerRecord class with overridden
 * dispose() method.
 *
 * When the object becomes unreachable, the dispose() method
 * of the associated DisposerRecord object will be called.
 *
 * @see DisposerRecord
 */
public class Disposer implements Runnable {
    private static final ReferenceQueue queue = new ReferenceQueue();
    private static final Hashtable records = new Hashtable();

    private static Disposer disposerInstance;
    public static final int WEAK = 0;
    public static final int PHANTOM = 1;
    public static int refType = PHANTOM;

    static {
        java.security.AccessController.doPrivileged(
            new sun.security.action.LoadLibraryAction("awt"));
        initIDs();
        String type = (String) java.security.AccessController.doPrivileged(
                new sun.security.action.GetPropertyAction("sun.java2d.reftype"));
        if (type != null) {
            if (type.equals("weak")) {
                refType = WEAK;
                System.err.println("Using WEAK refs");
            } else {
                refType = PHANTOM;
                System.err.println("Using PHANTOM refs");
            }
        }
        disposerInstance = new Disposer();
        java.security.AccessController.doPrivileged(
            new java.security.PrivilegedAction() {
                public Object run() {
                    /* The thread must be a member of a thread group
                     * which will not get GCed before VM exit.
                     * Make its parent the top-level thread group.
                     */
                    ThreadGroup tg = Thread.currentThread().getThreadGroup();
                    for (ThreadGroup tgn = tg;
                         tgn != null;
                         tg = tgn, tgn = tg.getParent());
                    Thread t =
                        new Thread(tg, disposerInstance, "Java2D Disposer");
                    t.setDaemon(true);
                    t.setPriority(Thread.MAX_PRIORITY);
                    t.start();
                    return null;
                }
            }
        );
    }

    /**
     * Registers the object and the native data for later disposal.
     * @param target Object to be registered
     * @param disposeMethod pointer to the native disposal method
     * @param pData pointer to the data to be passed to the
     *              native disposal method
     */
    public static void addRecord(Object target,
                                 long disposeMethod, long pData)
    {
        disposerInstance.add(target,
                             new DefaultDisposerRecord(disposeMethod, pData));
    }

    /**
     * Registers the object and the native data for later disposal.
     * @param target Object to be registered
     * @param rec the associated DisposerRecord object
     * @see DisposerRecord
     */
    public static void addRecord(Object target, DisposerRecord rec) {
        disposerInstance.add(target, rec);
    }

    /**
     * Performs the actual registration of the target object to be disposed.
     * @param target Object to be registered, or if target is an instance
     *               of DisposerTarget, its associated disposer referent
     *               will be the Object that is registered
     * @param rec the associated DisposerRecord object
     * @see DisposerRecord
     */
    synchronized void add(Object target, DisposerRecord rec) {
        if (target instanceof DisposerTarget) {
            target = ((DisposerTarget)target).getDisposerReferent();
        }
        java.lang.ref.Reference ref;
        if (refType == PHANTOM) {
            ref = new PhantomReference(target, queue);
        } else {
            ref = new WeakReference(target, queue);
        }
        records.put(ref, rec);
    }

    public void run() {
        while (true) {
            try {
                Object obj = queue.remove();
                ((Reference)obj).clear();
                DisposerRecord rec = (DisposerRecord)records.remove(obj);
                rec.dispose();
                obj = null;
                rec = null;
            } catch (Exception e) {
                System.out.println("Exception while removing reference: " + e);
                e.printStackTrace();
            }
        }
    }

    private static native void initIDs();

    /*
     * This was added for use by the 2D font implementation to avoid creation
     * of an additional disposer thread.
     * WARNING: this thread class monitors a specific queue, so a reference
     * added here must have been created with this queue. Failure to do
     * so will clutter the records hashmap and no one will be cleaning up
     * the reference queue.
     */
    public static void addReference(Reference ref, DisposerRecord rec) {
        records.put(ref, rec);
    }

    public static void addObjectRecord(Object obj, DisposerRecord rec) {
        records.put(new WeakReference(obj, queue) , rec);
    }

    /* This is intended for use in conjunction with addReference(..)
     */
    public static ReferenceQueue getQueue() {
        return queue;
    }

}