/*
 * Copyright (c) 2016, 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 jdk.internal.ref;

import jdk.internal.misc.InnocuousThread;
import jdk.internal.vm.annotation.ReservedStackAccess;

import java.lang.ref.Cleaner;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.concurrent.ThreadFactory;

/**
 * CleanerFactory provides a Cleaner for use within system modules.
 * The cleaner is created on the first reference to the CleanerFactory.
 */
public final class CleanerFactory {

    /* The common Cleaner. Lazily initialized */
    private static class Common {
        static final Cleaner INSTANCE = Cleaner.create(new ThreadFactory() {
            @Override
            public Thread newThread(Runnable r) {
                return AccessController.doPrivileged(new PrivilegedAction<>() {
                    @Override
                    public Thread run() {
                        Thread t = InnocuousThread.newSystemThread("Common-Cleaner", r);
                        t.setPriority(Thread.MAX_PRIORITY - 2);
                        return t;
                    }
                });
            }
        });
    }

    /* The NIO DirectByteBuffer ExtendedCleaner. Lazily initialized */
    private static class DBB {
        static final ExtendedCleaner INSTANCE = ExtendedCleaner.create(new ThreadFactory() {
            @Override
            public Thread newThread(Runnable r) {
                return AccessController.doPrivileged(new PrivilegedAction<>() {
                    @Override
                    public Thread run() {
                        Thread t = InnocuousThread.newSystemThread("DirectByteBuffer-Cleaner", r);
                        t.setPriority(Thread.MAX_PRIORITY - 2);
                        return t;
                    }
                });
            }
        });
    }

    /**
     * Cleaner for use within system modules.
     * <p>
     * This Cleaner will run on a thread whose context class loader
     * is {@code null}. The system cleaning action to perform in
     * this Cleaner should handle a {@code null} context class loader.
     *
     * @return a Cleaner for use within system modules
     */
    public static Cleaner cleaner() {
        return Common.INSTANCE;
    }

    /**
     * ExtendedCleaner for DirectByteBuffer use.
     * <p>
     * This Cleaner will mostly run on a background thread whose
     * context class loader is {@code null}. But since this is
     * {@link ExtendedCleaner} it allows other threads to help executing
     * cleaning actions. Cleaning actions to be performed in this ExtendedCleaner
     * should handle a {@code null} context class loader and any application
     * thread. When they are executed by an application thread they are
     * executed in the context of {@link ReservedStackAccess} annotation.
     *
     * @return an ExtendedCleaner for use in DirectByteBuffer
     */
    public static ExtendedCleaner dbbCleaner() {
        return DBB.INSTANCE;
    }
}