1 /* 2 * Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package jdk.nashorn.internal.runtime; 27 28 import java.lang.invoke.SwitchPoint; 29 30 /** 31 * This class represents a property map that can be shared among multiple prototype objects, allowing all inheriting 32 * top-level objects to also share one property map. This class is only used for prototype objects, the 33 * top-level objects use ordinary {@link PropertyMap}s with the {@link PropertyMap#sharedProtoMap} field 34 * set to the expected shared prototype map. 35 * 36 * <p>When an instance of this class is evolved because a property is added, removed, or modified in an object 37 * using it, the {@link #invalidateSwitchPoint()} method is invoked to signal to all callsites and inheriting 38 * objects that the assumption of a single shared prototype map is no longer valid. The property map resulting 39 * from the modification will no longer be an instance of this class.</p> 40 */ 41 public final class SharedPropertyMap extends PropertyMap { 42 43 @SuppressWarnings("serial") // Not statically typed as Serializable 44 private SwitchPoint switchPoint; 45 46 private static final long serialVersionUID = 2166297719721778876L; 47 48 /** 49 * Create a new shared property map from the given {@code map}. 50 * @param map property map to copy 51 */ 52 SharedPropertyMap(final PropertyMap map) { 53 super(map); 54 this.switchPoint = new SwitchPoint(); 55 } 56 57 @Override 58 public void propertyChanged(final Property property) { 59 invalidateSwitchPoint(); 60 super.propertyChanged(property); 61 } 62 63 @Override 64 synchronized boolean isValidSharedProtoMap() { 65 return switchPoint != null; 66 } 67 68 @Override 69 synchronized SwitchPoint getSharedProtoSwitchPoint() { 70 return switchPoint; 71 } 72 73 /** 74 * Invalidate the shared prototype switch point if this is a shared prototype map. 75 */ 76 synchronized void invalidateSwitchPoint() { 77 if (switchPoint != null) { 78 assert !switchPoint.hasBeenInvalidated(); 79 SwitchPoint.invalidateAll(new SwitchPoint[]{ switchPoint }); 80 switchPoint = null; 81 } 82 } 83 }