/*

 * Copyright (c) 2005, 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 com.sun.jmx.mbeanserver;

import java.lang.ref.WeakReference;

import java.util.WeakHashMap;

import javax.management.Descriptor;

import javax.management.ImmutableDescriptor;

import javax.management.JMX;

public class DescriptorCache {

    private DescriptorCache() {

    }

    static DescriptorCache getInstance() {

        return instance;

    }

    public static DescriptorCache getInstance(JMX proof) {

        if (proof != null)

            return instance;

        else

            return null;

    }

    public ImmutableDescriptor get(ImmutableDescriptor descriptor) {

        WeakReference<ImmutableDescriptor> wr = map.get(descriptor);

        ImmutableDescriptor got = (wr == null) ? null : wr.get();

        if (got != null)

            return got;

        map.put(descriptor, new WeakReference<ImmutableDescriptor>(descriptor));

        return descriptor;

    }

    public ImmutableDescriptor union(Descriptor... descriptors) {

        return get(ImmutableDescriptor.union(descriptors));

    }

    private final static DescriptorCache instance = new DescriptorCache();

    private final WeakHashMap<ImmutableDescriptor,

                              WeakReference<ImmutableDescriptor>>

        map = new WeakHashMap<ImmutableDescriptor,

                              WeakReference<ImmutableDescriptor>>();

}