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.util.function.Supplier;
  33 import jdk.dynalink.linker.ConversionComparator;
  34 import jdk.dynalink.linker.GuardedInvocation;
  35 import jdk.dynalink.linker.GuardingTypeConverterFactory;
  36 import jdk.dynalink.linker.LinkRequest;
  37 import jdk.dynalink.linker.LinkerServices;
  38 import jdk.dynalink.linker.TypeBasedGuardingDynamicLinker;
  39 import jdk.dynalink.linker.support.TypeUtilities;
  40 import jdk.nashorn.internal.objects.Global;
  41 import jdk.nashorn.internal.runtime.ConsString;
  42 import jdk.nashorn.internal.runtime.JSType;
  43 import jdk.nashorn.internal.runtime.ScriptRuntime;
  44 import jdk.nashorn.internal.runtime.Symbol;
  45 
  46 /**
  47  * Internal linker for String, Boolean, and Number objects, only ever used by Nashorn engine and not exposed to other
  48  * engines. It is used for treatment of strings, boolean, and numbers as JavaScript primitives. Also provides ECMAScript
  49  * primitive type conversions for these types when linking to Java methods.
  50  */
  51 final class NashornPrimitiveLinker implements TypeBasedGuardingDynamicLinker, GuardingTypeConverterFactory, ConversionComparator {
  52     private static final GuardedInvocation VOID_TO_OBJECT =
  53             new GuardedInvocation(MethodHandles.constant(Object.class, ScriptRuntime.UNDEFINED));
  54 
  55     @Override
  56     public boolean canLinkType(final Class<?> type) {
  57         return canLinkTypeStatic(type);
  58     }
  59 
  60     private static boolean canLinkTypeStatic(final Class<?> type) {
  61         return type == String.class || type == Boolean.class || type == ConsString.class || type == Integer.class
  62                 || type == Double.class || type == Float.class || type == Short.class || type == Byte.class
  63                 || type == Symbol.class;
  64     }
  65 
  66     @Override
  67     public GuardedInvocation getGuardedInvocation(final LinkRequest request, final LinkerServices linkerServices)
  68             throws Exception {
  69         final Object self = request.getReceiver();
  70         return Bootstrap.asTypeSafeReturn(Global.primitiveLookup(request, self), linkerServices, request.getCallSiteDescriptor());
  71     }
  72 
  73     /**
  74      * This implementation of type converter factory will pretty much allow implicit conversions of anything to anything
  75      * else that's allowed among JavaScript primitive types (string to number, boolean to string, etc.)
  76      * @param sourceType the type to convert from
  77      * @param targetType the type to convert to
  78      * @return a conditional converter from source to target type
  79      */
  80     @Override
  81     public GuardedInvocation convertToType(final Class<?> sourceType, final Class<?> targetType, final Supplier<MethodHandles.Lookup> lookupSupplier) {
  82         final MethodHandle mh = JavaArgumentConverters.getConverter(targetType);
  83         if (mh == null) {
  84             if(targetType == Object.class && sourceType == void.class) {
  85                 return VOID_TO_OBJECT;
  86             }
  87             return null;
  88         }
  89 
  90         return new GuardedInvocation(mh, canLinkTypeStatic(sourceType) ? null : GUARD_PRIMITIVE).asType(mh.type().changeParameterType(0, sourceType));
  91     }
  92 
  93     /**
  94      * Implements the somewhat involved prioritization of JavaScript primitive types conversions. Instead of explaining
  95      * it here in prose, just follow the source code comments.
  96      * @param sourceType the source type to convert from
  97      * @param targetType1 one candidate target type
  98      * @param targetType2 another candidate target type
  99      * @return one of {@link jdk.dynalink.linker.ConversionComparator.Comparison} values signifying which
 100      * target type should be favored for conversion.
 101      */
 102     @Override
 103     public Comparison compareConversion(final Class<?> sourceType, final Class<?> targetType1, final Class<?> targetType2) {
 104         final Class<?> wrapper1 = getWrapperTypeOrSelf(targetType1);
 105         if (sourceType == wrapper1) {
 106             // Source type exactly matches target 1
 107             return Comparison.TYPE_1_BETTER;
 108         }
 109         final Class<?> wrapper2 = getWrapperTypeOrSelf(targetType2);
 110         if (sourceType == wrapper2) {
 111             // Source type exactly matches target 2
 112             return Comparison.TYPE_2_BETTER;
 113         }
 114 
 115         if (Number.class.isAssignableFrom(sourceType)) {
 116             // If exactly one of the targets is a number, pick it.
 117             if (Number.class.isAssignableFrom(wrapper1)) {
 118                 if (!Number.class.isAssignableFrom(wrapper2)) {
 119                     return Comparison.TYPE_1_BETTER;
 120                 }
 121             } else if (Number.class.isAssignableFrom(wrapper2)) {
 122                 return Comparison.TYPE_2_BETTER;
 123             }
 124 
 125             // If exactly one of the targets is a character, pick it. Numbers can be reasonably converted to chars using
 126             // the UTF-16 values.
 127             if (Character.class == wrapper1) {
 128                 return Comparison.TYPE_1_BETTER;
 129             } else if (Character.class == wrapper2) {
 130                 return Comparison.TYPE_2_BETTER;
 131             }
 132 
 133             // For all other cases, we fall through to the next if statement - not that we repeat the condition in it
 134             // too so if we entered this branch, we'll enter the below if statement too.
 135         }
 136 
 137         if (sourceType == String.class || sourceType == Boolean.class || Number.class.isAssignableFrom(sourceType)) {
 138             // Treat wrappers as primitives.
 139             final Class<?> primitiveType1 = getPrimitiveTypeOrSelf(targetType1);
 140             final Class<?> primitiveType2 = getPrimitiveTypeOrSelf(targetType2);
 141             // Basically, choose the widest possible primitive type. (First "if" returning TYPE_2_BETTER is correct;
 142             // when faced with a choice between double and int, choose double).
 143             if (TypeUtilities.isMethodInvocationConvertible(primitiveType1, primitiveType2)) {
 144                 return Comparison.TYPE_2_BETTER;
 145             } else if (TypeUtilities.isMethodInvocationConvertible(primitiveType2, primitiveType1)) {
 146                 return Comparison.TYPE_1_BETTER;
 147             }
 148             // Ok, at this point we're out of possible number conversions, so try strings. A String can represent any
 149             // value without loss, so if one of the potential targets is string, go for it.
 150             if (targetType1 == String.class) {
 151                 return Comparison.TYPE_1_BETTER;
 152             }
 153             if (targetType2 == String.class) {
 154                 return Comparison.TYPE_2_BETTER;
 155             }
 156         }
 157 
 158         return Comparison.INDETERMINATE;
 159     }
 160 
 161     private static Class<?> getPrimitiveTypeOrSelf(final Class<?> type) {
 162         final Class<?> primitive = TypeUtilities.getPrimitiveType(type);
 163         return primitive == null ? type : primitive;
 164     }
 165 
 166     private static Class<?> getWrapperTypeOrSelf(final Class<?> type) {
 167         final Class<?> wrapper = TypeUtilities.getWrapperType(type);
 168         return wrapper == null ? type : wrapper;
 169     }
 170 
 171     @SuppressWarnings("unused")
 172     private static boolean isJavaScriptPrimitive(final Object o) {
 173         return JSType.isString(o) || o instanceof Boolean || JSType.isNumber(o) || o == null || o instanceof Symbol;
 174     }
 175 
 176     private static final MethodHandle GUARD_PRIMITIVE = findOwnMH("isJavaScriptPrimitive", boolean.class, Object.class);
 177 
 178     private static MethodHandle findOwnMH(final String name, final Class<?> rtype, final Class<?>... types) {
 179         return MH.findStatic(MethodHandles.lookup(), NashornPrimitiveLinker.class, name, MH.type(rtype, types));
 180     }
 181 }