1 /*
2 * Copyright (c) 2010, 2013, 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.linker;
27
28 import static jdk.nashorn.internal.lookup.Lookup.MH;
29
30 import java.lang.invoke.MethodHandle;
31 import java.lang.invoke.MethodHandles;
32 import java.lang.ref.WeakReference;
33 import jdk.internal.dynalink.CallSiteDescriptor;
34 import jdk.nashorn.internal.codegen.ObjectClassGenerator;
35 import jdk.nashorn.internal.objects.Global;
36 import jdk.nashorn.internal.runtime.Property;
37 import jdk.nashorn.internal.runtime.PropertyMap;
38 import jdk.nashorn.internal.runtime.ScriptFunction;
39 import jdk.nashorn.internal.runtime.ScriptObject;
40
41 /**
42 * Constructor of method handles used to guard call sites.
43 */
44 public final class NashornGuards {
45 private static final MethodHandle IS_SCRIPTOBJECT = findOwnMH("isScriptObject", boolean.class, Object.class);
46 private static final MethodHandle IS_SCRIPTFUNCTION = findOwnMH("isScriptFunction", boolean.class, Object.class);
47 private static final MethodHandle IS_MAP = findOwnMH("isMap", boolean.class, Object.class, PropertyMap.class);
48 private static final MethodHandle SAME_OBJECT = findOwnMH("sameObject", boolean.class, Object.class, WeakReference.class);
49 private static final MethodHandle IS_INSTANCEOF_2 = findOwnMH("isInstanceOf2", boolean.class, Object.class, Class.class, Class.class);
50
51 // don't create me!
52 private NashornGuards() {
53 }
54
55 /**
56 * Get the guard that checks if an item is a {@code ScriptObject}
57 * @return method handle for guard
58 */
59 public static MethodHandle getScriptObjectGuard() {
60 return IS_SCRIPTOBJECT;
61 }
62
63 /**
64 * Get the guard that checks if an item is a {@code ScriptFunction}
65 * @return method handle for guard
66 */
67 public static MethodHandle getScriptFunctionGuard() {
68 return IS_SCRIPTFUNCTION;
69 }
70
71 /**
72 * Get the guard that checks if a {@link PropertyMap} is equal to
73 * a known map, using reference comparison
74 *
75 * @param map The map to check against. This will be bound to the guard method handle
76 *
77 * @return method handle for guard
78 */
79 public static MethodHandle getMapGuard(final PropertyMap map) {
80 return MH.insertArguments(IS_MAP, 1, map);
81 }
82
83 /**
84 * Determine whether the given callsite needs a guard.
85 * @param property the property, or null
86 * @param desc the callsite descriptor
87 * @return true if a guard should be used for this callsite
88 */
89 static boolean needsGuard(final Property property, final CallSiteDescriptor desc) {
90 return property == null || property.isConfigurable()
91 || property.isBound() || !ObjectClassGenerator.OBJECT_FIELDS_ONLY
92 || !NashornCallSiteDescriptor.isFastScope(desc) || property.canChangeType();
93 }
94
95 /**
96 * Get the guard for a property access. This returns an identity guard for non-configurable global properties
97 * and a map guard for everything else.
98 *
99 * @param sobj the first object in the prototype chain
100 * @param property the property
101 * @param desc the callsite descriptor
102 * @return method handle for guard
103 */
104 public static MethodHandle getGuard(final ScriptObject sobj, final Property property, final CallSiteDescriptor desc) {
105 if (!needsGuard(property, desc)) {
106 return null;
107 }
108 if (NashornCallSiteDescriptor.isScope(desc)) {
109 if (property != null && property.isBound()) {
110 // This is a declared top level variables in main script or eval, use identity guard.
111 return getIdentityGuard(sobj);
112 }
113 if (!(sobj instanceof Global) && (property == null || property.isConfigurable())) {
114 // Undeclared variables in nested evals need stronger guards
115 return combineGuards(getIdentityGuard(sobj), getMapGuard(sobj.getMap()));
116 }
117 }
118 return getMapGuard(sobj.getMap());
119 }
120
121
122 /**
123 * Get a guard that checks referential identity of the current object.
124 *
125 * @param sobj the self object
126 * @return true if same self object instance
127 */
128 public static MethodHandle getIdentityGuard(final ScriptObject sobj) {
129 return MH.insertArguments(SAME_OBJECT, 1, new WeakReference<>(sobj));
130 }
131
132 /**
133 * Get a guard that checks if in item is an instance of either of two classes.
134 *
135 * @param class1 the first class
136 * @param class2 the second class
137 * @return method handle for guard
138 */
139 public static MethodHandle getInstanceOf2Guard(final Class<?> class1, final Class<?> class2) {
140 return MH.insertArguments(IS_INSTANCEOF_2, 1, class1, class2);
141 }
142
143 /**
144 * Combine two method handles of type {@code (Object)boolean} using logical AND.
145 *
146 * @param guard1 the first guard
147 * @param guard2 the second guard, only invoked if guard1 returns true
148 * @return true if both guard1 and guard2 returned true
149 */
150 public static MethodHandle combineGuards(final MethodHandle guard1, final MethodHandle guard2) {
151 return MH.guardWithTest(guard1, guard2, MH.dropArguments(MH.constant(boolean.class, false), 0, Object.class));
152 }
153
154 @SuppressWarnings("unused")
155 private static boolean isScriptObject(final Object self) {
156 return self instanceof ScriptObject;
157 }
158
159 @SuppressWarnings("unused")
160 private static boolean isScriptFunction(final Object self) {
161 return self instanceof ScriptFunction;
162 }
163
164 @SuppressWarnings("unused")
165 private static boolean isMap(final Object self, final PropertyMap map) {
166 return self instanceof ScriptObject && ((ScriptObject)self).getMap() == map;
167 }
168
169 @SuppressWarnings("unused")
170 private static boolean sameObject(final Object self, final WeakReference<ScriptObject> ref) {
171 return self == ref.get();
172 }
173
174 @SuppressWarnings("unused")
175 private static boolean isInstanceOf2(final Object self, final Class<?> class1, final Class<?> class2) {
176 return class1.isInstance(self) || class2.isInstance(self);
177 }
178
179 private static MethodHandle findOwnMH(final String name, final Class<?> rtype, final Class<?>... types) {
180 return MH.findStatic(MethodHandles.lookup(), NashornGuards.class, name, MH.type(rtype, types));
181 }
182
183 }