/*

 * Copyright (c) 2002, 2015, Oracle and/or its affiliates. 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.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.java2d;

import sun.awt.util.ThreadGroupUtils;

import sun.misc.ManagedLocalsThread;

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.ArrayList;

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<Object> queue = new ReferenceQueue<>();

    private static final Hashtable<java.lang.ref.Reference<Object>, DisposerRecord> 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 java.security.PrivilegedAction<Void>() {

                public Void run() {

                    System.loadLibrary("awt");

                    return null;

                }

            });

        initIDs();

        String type = 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();

        AccessController.doPrivileged((PrivilegedAction<Void>) () -> {

            String name = "Java2D Disposer";

            ThreadGroup rootTG = ThreadGroupUtils.getRootThreadGroup();

            Thread t = new ManagedLocalsThread(rootTG, disposerInstance, name);

            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.

     * @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<Object> 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 = records.remove(obj);

                rec.dispose();

                obj = null;

                rec = null;

                clearDeferredRecords();

            } catch (Exception e) {

                System.out.println("Exception while removing reference.");

            }

        }

    }

    /*

     * This is a marker interface that, if implemented, means it

     * doesn't acquire any special locks, and is safe to

     * be disposed in the poll loop on whatever thread

     * which happens to be the Toolkit thread, is in use.

     */

    public static interface PollDisposable {

    };

    private static ArrayList<DisposerRecord> deferredRecords = null;

    private static void clearDeferredRecords() {

        if (deferredRecords == null || deferredRecords.isEmpty()) {

            return;

        }

        for (int i=0;i<deferredRecords.size(); i++) {

            try {

                DisposerRecord rec = deferredRecords.get(i);

                rec.dispose();

            } catch (Exception e) {

                System.out.println("Exception while disposing deferred rec.");

            }

        }

        deferredRecords.clear();

    }

    /*

     * Set to indicate the queue is presently being polled.

     */

    public static volatile boolean pollingQueue = false;

    /*

     * The pollRemove() method is called back from a dispose method

     * that is running on the toolkit thread and wants to

     * dispose any pending refs that are safe to be disposed

     * on that thread.

     */

    public static void pollRemove() {

        /* This should never be called recursively, so this check

         * is just a safeguard against the unexpected.

         */

        if (pollingQueue) {

            return;

        }

        Object obj;

        pollingQueue = true;

        int freed = 0;

        int deferred = 0;

        try {

            while ( freed < 10000 && deferred < 100 &&

                    (obj = queue.poll()) != null ) {

                freed++;

                ((Reference)obj).clear();

                DisposerRecord rec = records.remove(obj);

                if (rec instanceof PollDisposable) {

                    rec.dispose();

                    obj = null;

                    rec = null;

                } else {

                    if (rec == null) { // shouldn't happen, but just in case.

                        continue;

                    }

                    deferred++;

                    if (deferredRecords == null) {

                      deferredRecords = new ArrayList<DisposerRecord>(5);

                    }

                    deferredRecords.add(rec);

                }

            }

        } catch (Exception e) {

            System.out.println("Exception while removing reference.");

        } finally {

            pollingQueue = false;

        }

    }

    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.

     */

    @SuppressWarnings("unchecked")

    public static void addReference(Reference<Object> 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<Object> getQueue() {

        return queue;

    }

}