AllocationStrategy.java revision 1786:80120e9b3273
1/* 2 * Copyright (c) 2014, 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 */ 25package jdk.nashorn.internal.runtime; 26 27import static jdk.nashorn.internal.lookup.Lookup.MH; 28 29import java.io.Serializable; 30import java.lang.invoke.MethodHandle; 31import java.lang.invoke.MethodHandles; 32import java.lang.ref.WeakReference; 33import jdk.nashorn.internal.codegen.Compiler; 34import jdk.nashorn.internal.codegen.CompilerConstants; 35import jdk.nashorn.internal.codegen.ObjectClassGenerator; 36 37/** 38 * Encapsulates the allocation strategy for a function when used as a constructor. 39 */ 40final public class AllocationStrategy implements Serializable { 41 private static final long serialVersionUID = 1L; 42 43 private static final MethodHandles.Lookup LOOKUP = MethodHandles.lookup(); 44 45 /** Number of fields in the allocated object */ 46 private final int fieldCount; 47 48 /** Whether to use dual field representation */ 49 private final boolean dualFields; 50 51 /** Name of class where allocator function resides */ 52 private transient String allocatorClassName; 53 54 /** lazily generated allocator */ 55 private transient MethodHandle allocator; 56 57 /** Last used allocator map */ 58 private transient AllocatorMap lastMap; 59 60 /** 61 * Construct an allocation strategy with the given map and class name. 62 * @param fieldCount number of fields in the allocated object 63 * @param dualFields whether to use dual field representation 64 */ 65 public AllocationStrategy(final int fieldCount, final boolean dualFields) { 66 this.fieldCount = fieldCount; 67 this.dualFields = dualFields; 68 } 69 70 private String getAllocatorClassName() { 71 if (allocatorClassName == null) { 72 // These classes get loaded, so an interned variant of their name is most likely around anyway. 73 allocatorClassName = Compiler.binaryName(ObjectClassGenerator.getClassName(fieldCount, dualFields)).intern(); 74 } 75 return allocatorClassName; 76 } 77 78 /** 79 * Get the property map for the allocated object. 80 * @param prototype the prototype object 81 * @return the property map 82 */ 83 synchronized PropertyMap getAllocatorMap(final ScriptObject prototype) { 84 assert prototype != null; 85 final PropertyMap protoMap = prototype.getMap(); 86 87 if (lastMap != null) { 88 if (!lastMap.hasSharedProtoMap()) { 89 if (lastMap.hasSamePrototype(prototype)) { 90 return lastMap.allocatorMap; 91 } 92 if (lastMap.hasSameProtoMap(protoMap) && lastMap.hasUnchangedProtoMap()) { 93 // Convert to shared prototype map. Allocated objects will use the same property map 94 // that can be used as long as none of the prototypes modify the shared proto map. 95 final PropertyMap allocatorMap = PropertyMap.newMap(null, getAllocatorClassName(), 0, fieldCount, 0); 96 final SharedPropertyMap sharedProtoMap = new SharedPropertyMap(protoMap); 97 allocatorMap.setSharedProtoMap(sharedProtoMap); 98 prototype.setMap(sharedProtoMap); 99 lastMap = new AllocatorMap(prototype, protoMap, allocatorMap); 100 return allocatorMap; 101 } 102 } 103 104 if (lastMap.hasValidSharedProtoMap() && lastMap.hasSameProtoMap(protoMap)) { 105 prototype.setMap(lastMap.getSharedProtoMap()); 106 return lastMap.allocatorMap; 107 } 108 } 109 110 final PropertyMap allocatorMap = PropertyMap.newMap(null, getAllocatorClassName(), 0, fieldCount, 0); 111 lastMap = new AllocatorMap(prototype, protoMap, allocatorMap); 112 113 return allocatorMap; 114 } 115 116 /** 117 * Allocate an object with the given property map 118 * @param map the property map 119 * @return the allocated object 120 */ 121 ScriptObject allocate(final PropertyMap map) { 122 try { 123 if (allocator == null) { 124 allocator = MH.findStatic(LOOKUP, Context.forStructureClass(getAllocatorClassName()), 125 CompilerConstants.ALLOCATE.symbolName(), MH.type(ScriptObject.class, PropertyMap.class)); 126 } 127 return (ScriptObject)allocator.invokeExact(map); 128 } catch (final RuntimeException | Error e) { 129 throw e; 130 } catch (final Throwable t) { 131 throw new RuntimeException(t); 132 } 133 } 134 135 @Override 136 public String toString() { 137 return "AllocationStrategy[fieldCount=" + fieldCount + "]"; 138 } 139 140 static class AllocatorMap { 141 final private WeakReference<ScriptObject> prototype; 142 final private WeakReference<PropertyMap> prototypeMap; 143 144 private final PropertyMap allocatorMap; 145 146 AllocatorMap(final ScriptObject prototype, final PropertyMap protoMap, final PropertyMap allocMap) { 147 this.prototype = new WeakReference<>(prototype); 148 this.prototypeMap = new WeakReference<>(protoMap); 149 this.allocatorMap = allocMap; 150 } 151 152 boolean hasSamePrototype(final ScriptObject proto) { 153 return prototype.get() == proto; 154 } 155 156 boolean hasSameProtoMap(final PropertyMap protoMap) { 157 return prototypeMap.get() == protoMap || allocatorMap.getSharedProtoMap() == protoMap; 158 } 159 160 boolean hasUnchangedProtoMap() { 161 final ScriptObject proto = prototype.get(); 162 return proto != null && proto.getMap() == prototypeMap.get(); 163 } 164 165 boolean hasSharedProtoMap() { 166 return getSharedProtoMap() != null; 167 } 168 169 boolean hasValidSharedProtoMap() { 170 return hasSharedProtoMap() && getSharedProtoMap().isValidSharedProtoMap(); 171 } 172 173 PropertyMap getSharedProtoMap() { 174 return allocatorMap.getSharedProtoMap(); 175 } 176 177 } 178} 179