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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
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 *
 * 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).
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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.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Hashtable;

import sun.misc.ThreadGroupUtils;

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 Also:
DisposerRecord/**
 * 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<Void>() {
                public Void 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 rootTG = ThreadGroupUtils.getRootThreadGroup();
                    Thread t = new Thread(rootTG, disposerInstance, "Java2D Disposer");
                    t.setContextClassLoader(null);
                    t.setDaemon(true);
                    t.setPriority(Thread.MAX_PRIORITY);
                    t.start();
                    return null;
                }
            }
        );
    }

    
Registers the object and the native data for later disposal.
Params:
target – Object to be registered
disposeMethod – pointer to the native disposal method
pData – pointer to the data to be passed to the
             native disposal method/**
     * 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.
Params:
target – Object to be registered
rec – the associated DisposerRecord object
See Also:
DisposerRecord/**
     * 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.
Params:
target – Object to be registered, or if target is an instance
              of DisposerTarget, its associated disposer referent
              will be the Object that is registered
rec – the associated DisposerRecord object
See Also:
DisposerRecord/**
     * 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.");
            }
        }
    }

    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;
    }

}