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 jdk.internal.dynalink.linker.ConversionComparator;
33 import jdk.internal.dynalink.linker.GuardedInvocation;
34 import jdk.internal.dynalink.linker.GuardedTypeConversion;
35 import jdk.internal.dynalink.linker.GuardingTypeConverterFactory;
36 import jdk.internal.dynalink.linker.LinkRequest;
37 import jdk.internal.dynalink.linker.LinkerServices;
38 import jdk.internal.dynalink.linker.TypeBasedGuardingDynamicLinker;
39 import jdk.internal.dynalink.support.TypeUtilities;
40 import jdk.nashorn.internal.runtime.ConsString;
41 import jdk.nashorn.internal.runtime.Context;
42 import jdk.nashorn.internal.runtime.GlobalObject;
43
44 /**
45 * Internal linker for String, Boolean, and Number objects, only ever used by Nashorn engine and not exposed to other
46 * engines. It is used for treatment of strings, boolean, and numbers as JavaScript primitives. Also provides ECMAScript
47 * primitive type conversions for these types when linking to Java methods.
48 */
49 final class NashornPrimitiveLinker implements TypeBasedGuardingDynamicLinker, GuardingTypeConverterFactory, ConversionComparator {
50 @Override
51 public boolean canLinkType(final Class<?> type) {
52 return canLinkTypeStatic(type);
53 }
54
55 private static boolean canLinkTypeStatic(final Class<?> type) {
56 return type == String.class || type == Boolean.class || type == ConsString.class || Number.class.isAssignableFrom(type);
57 }
58
59 @Override
60 public GuardedInvocation getGuardedInvocation(final LinkRequest origRequest, final LinkerServices linkerServices)
61 throws Exception {
62 final LinkRequest request = origRequest.withoutRuntimeContext(); // Nashorn has no runtime context
63
64 final Object self = request.getReceiver();
65 final GlobalObject global = (GlobalObject) Context.getGlobal();
66 final NashornCallSiteDescriptor desc = (NashornCallSiteDescriptor) request.getCallSiteDescriptor();
67
68 return Bootstrap.asType(global.primitiveLookup(request, self), linkerServices, desc);
69 }
70
71 /**
72 * This implementation of type converter factory will pretty much allow implicit conversions of anything to anything
73 * else that's allowed among JavaScript primitive types (string to number, boolean to string, etc.)
74 * @param sourceType the type to convert from
75 * @param targetType the type to convert to
76 * @return a conditional converter from source to target type
77 */
78 @Override
79 public GuardedTypeConversion convertToType(final Class<?> sourceType, final Class<?> targetType) {
80 final MethodHandle mh = JavaArgumentConverters.getConverter(targetType);
81 if (mh == null) {
82 return null;
83 }
84
85 return new GuardedTypeConversion(new GuardedInvocation(mh, canLinkTypeStatic(sourceType) ? null : GUARD_PRIMITIVE).asType(mh.type().changeParameterType(0, sourceType)), true);
86 }
87
88 /**
89 * Implements the somewhat involved prioritization of JavaScript primitive types conversions. Instead of explaining
90 * it here in prose, just follow the source code comments.
91 * @param sourceType the source type to convert from
92 * @param targetType1 one candidate target type
93 * @param targetType2 another candidate target type
94 * @return one of {@link jdk.internal.dynalink.linker.ConversionComparator.Comparison} values signifying which
95 * target type should be favored for conversion.
96 */
97 @Override
98 public Comparison compareConversion(final Class<?> sourceType, final Class<?> targetType1, final Class<?> targetType2) {
99 final Class<?> wrapper1 = getWrapperTypeOrSelf(targetType1);
100 if (sourceType == wrapper1) {
101 // Source type exactly matches target 1
102 return Comparison.TYPE_1_BETTER;
103 }
104 final Class<?> wrapper2 = getWrapperTypeOrSelf(targetType2);
105 if (sourceType == wrapper2) {
106 // Source type exactly matches target 2
107 return Comparison.TYPE_2_BETTER;
108 }
109
110 if (Number.class.isAssignableFrom(sourceType)) {
111 // If exactly one of the targets is a number, pick it.
112 if (Number.class.isAssignableFrom(wrapper1)) {
113 if (!Number.class.isAssignableFrom(wrapper2)) {
114 return Comparison.TYPE_1_BETTER;
115 }
116 } else if (Number.class.isAssignableFrom(wrapper2)) {
117 return Comparison.TYPE_2_BETTER;
118 }
119
120 // If exactly one of the targets is a character, pick it. Numbers can be reasonably converted to chars using
121 // the UTF-16 values.
122 if (Character.class == wrapper1) {
123 return Comparison.TYPE_1_BETTER;
124 } else if (Character.class == wrapper2) {
125 return Comparison.TYPE_2_BETTER;
126 }
127
128 // For all other cases, we fall through to the next if statement - not that we repeat the condition in it
129 // too so if we entered this branch, we'll enter the below if statement too.
130 }
131
132 if (sourceType == String.class || sourceType == Boolean.class || Number.class.isAssignableFrom(sourceType)) {
133 // Treat wrappers as primitives.
134 final Class<?> primitiveType1 = getPrimitiveTypeOrSelf(targetType1);
135 final Class<?> primitiveType2 = getPrimitiveTypeOrSelf(targetType2);
136 // Basically, choose the widest possible primitive type. (First "if" returning TYPE_2_BETTER is correct;
137 // when faced with a choice between double and int, choose double).
138 if (TypeUtilities.isMethodInvocationConvertible(primitiveType1, primitiveType2)) {
139 return Comparison.TYPE_2_BETTER;
140 } else if (TypeUtilities.isMethodInvocationConvertible(primitiveType2, primitiveType1)) {
141 return Comparison.TYPE_1_BETTER;
142 }
143 // Ok, at this point we're out of possible number conversions, so try strings. A String can represent any
144 // value without loss, so if one of the potential targets is string, go for it.
145 if (targetType1 == String.class) {
146 return Comparison.TYPE_1_BETTER;
147 }
148 if (targetType2 == String.class) {
149 return Comparison.TYPE_2_BETTER;
150 }
151 }
152
153 return Comparison.INDETERMINATE;
154 }
155
156 private static Class<?> getPrimitiveTypeOrSelf(final Class<?> type) {
157 final Class<?> primitive = TypeUtilities.getPrimitiveType(type);
158 return primitive == null ? type : primitive;
159 }
160
161 private static Class<?> getWrapperTypeOrSelf(final Class<?> type) {
162 final Class<?> wrapper = TypeUtilities.getWrapperType(type);
163 return wrapper == null ? type : wrapper;
164 }
165
166 @SuppressWarnings("unused")
167 private static boolean isJavaScriptPrimitive(final Object o) {
168 return o instanceof String || o instanceof Boolean || o instanceof Number || o instanceof ConsString || o == null;
169 }
170
171 private static final MethodHandle GUARD_PRIMITIVE = findOwnMH("isJavaScriptPrimitive", boolean.class, Object.class);
172
173 private static MethodHandle findOwnMH(final String name, final Class<?> rtype, final Class<?>... types) {
174 return MH.findStatic(MethodHandles.lookup(), NashornPrimitiveLinker.class, name, MH.type(rtype, types));
175 }
176 }