/*

 * 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.nashorn.internal.runtime;

import java.lang.invoke.SwitchPoint;

/**

 * This class represents a property map that can be shared among multiple prototype objects, allowing all inheriting

 * top-level objects to also share one property map. This class is only used for prototype objects, the

 * top-level objects use ordinary {@link PropertyMap}s with the {@link PropertyMap#sharedProtoMap} field

 * set to the expected shared prototype map.

 *

 * <p>When an instance of this class is evolved because a property is added, removed, or modified in an object

 * using it, the {@link #invalidateSwitchPoint()} method is invoked to signal to all callsites and inheriting

 * objects that the assumption of a single shared prototype map is no longer valid. The property map resulting

 * from the modification will no longer be an instance of this class.</p>

 */

public final class SharedPropertyMap extends PropertyMap {

    private SwitchPoint switchPoint;

    private static final long serialVersionUID = 2166297719721778876L;

    /**

     * Create a new shared property map from the given {@code map}.

     * @param map property map to copy

     */

    SharedPropertyMap(final PropertyMap map) {

        super(map);

        this.switchPoint = new SwitchPoint();

    }

    @Override

    public void propertyChanged(final Property property) {

        invalidateSwitchPoint();

        super.propertyChanged(property);

    }

    @Override

    synchronized boolean isValidSharedProtoMap() {

        return switchPoint != null;

    }

    @Override

    synchronized SwitchPoint getSharedProtoSwitchPoint() {

        return switchPoint;

    }

    /**

     * Invalidate the shared prototype switch point if this is a shared prototype map.

     */

    synchronized void invalidateSwitchPoint() {

        if (switchPoint != null) {

            assert !switchPoint.hasBeenInvalidated();

            SwitchPoint.invalidateAll(new SwitchPoint[]{ switchPoint });

            switchPoint = null;

        }

    }

}