Mercurial > jdk8-mips64-public > nashorn / file revision

 /*

  * Copyright (c) 2010, 2013, Oracle and/or its affiliates. All rights reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.  Oracle designates this

  * particular file as subject to the "Classpath" exception as provided

  * by Oracle in the LICENSE file that accompanied this code.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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  */

 package jdk.nashorn.internal.runtime.linker;

 import static jdk.nashorn.internal.lookup.Lookup.MH;

 import java.lang.invoke.MethodHandle;

 import java.lang.invoke.MethodHandles;

 import jdk.internal.dynalink.linker.ConversionComparator;

 import jdk.internal.dynalink.linker.GuardedInvocation;

 import jdk.internal.dynalink.linker.GuardedTypeConversion;

 import jdk.internal.dynalink.linker.GuardingTypeConverterFactory;

 import jdk.internal.dynalink.linker.LinkRequest;

 import jdk.internal.dynalink.linker.LinkerServices;

 import jdk.internal.dynalink.linker.TypeBasedGuardingDynamicLinker;

 import jdk.internal.dynalink.support.TypeUtilities;

 import jdk.nashorn.internal.objects.Global;

 import jdk.nashorn.internal.runtime.ConsString;

 import jdk.nashorn.internal.runtime.JSType;

 import jdk.nashorn.internal.runtime.ScriptRuntime;

 /**

  * Internal linker for String, Boolean, and Number objects, only ever used by Nashorn engine and not exposed to other

  * engines. It is used for treatment of strings, boolean, and numbers as JavaScript primitives. Also provides ECMAScript

  * primitive type conversions for these types when linking to Java methods.

  */

 final class NashornPrimitiveLinker implements TypeBasedGuardingDynamicLinker, GuardingTypeConverterFactory, ConversionComparator {

     private static final GuardedTypeConversion VOID_TO_OBJECT = new GuardedTypeConversion(

             new GuardedInvocation(MethodHandles.constant(Object.class, ScriptRuntime.UNDEFINED)), true);

     @Override

     public boolean canLinkType(final Class<?> type) {

         return canLinkTypeStatic(type);

     }

     private static boolean canLinkTypeStatic(final Class<?> type) {

         return type == String.class || type == Boolean.class || type == ConsString.class || type == Integer.class

                 || type == Double.class || type == Float.class || type == Short.class || type == Byte.class;

     }

     @Override

     public GuardedInvocation getGuardedInvocation(final LinkRequest origRequest, final LinkerServices linkerServices)

             throws Exception {

         final LinkRequest request = origRequest.withoutRuntimeContext(); // Nashorn has no runtime context

         final Object self = request.getReceiver();

         final NashornCallSiteDescriptor desc = (NashornCallSiteDescriptor) request.getCallSiteDescriptor();

         return Bootstrap.asTypeSafeReturn(Global.primitiveLookup(request, self), linkerServices, desc);

     }

     /**

      * This implementation of type converter factory will pretty much allow implicit conversions of anything to anything

      * else that's allowed among JavaScript primitive types (string to number, boolean to string, etc.)

      * @param sourceType the type to convert from

      * @param targetType the type to convert to

      * @return a conditional converter from source to target type

      */

     @Override

     public GuardedTypeConversion convertToType(final Class<?> sourceType, final Class<?> targetType) {

         final MethodHandle mh = JavaArgumentConverters.getConverter(targetType);

         if (mh == null) {

             if(targetType == Object.class && sourceType == void.class) {

                 return VOID_TO_OBJECT;

             }

             return null;

         }

         return new GuardedTypeConversion(new GuardedInvocation(mh, canLinkTypeStatic(sourceType) ? null : GUARD_PRIMITIVE).asType(mh.type().changeParameterType(0, sourceType)), true);

     }

     /**

      * Implements the somewhat involved prioritization of JavaScript primitive types conversions. Instead of explaining

      * it here in prose, just follow the source code comments.

      * @param sourceType the source type to convert from

      * @param targetType1 one candidate target type

      * @param targetType2 another candidate target type

      * @return one of {@link jdk.internal.dynalink.linker.ConversionComparator.Comparison} values signifying which

      * target type should be favored for conversion.

      */

     @Override

     public Comparison compareConversion(final Class<?> sourceType, final Class<?> targetType1, final Class<?> targetType2) {

         final Class<?> wrapper1 = getWrapperTypeOrSelf(targetType1);

         if (sourceType == wrapper1) {

             // Source type exactly matches target 1

             return Comparison.TYPE_1_BETTER;

         }

         final Class<?> wrapper2 = getWrapperTypeOrSelf(targetType2);

         if (sourceType == wrapper2) {

             // Source type exactly matches target 2

             return Comparison.TYPE_2_BETTER;

         }

         if (Number.class.isAssignableFrom(sourceType)) {

             // If exactly one of the targets is a number, pick it.

             if (Number.class.isAssignableFrom(wrapper1)) {

                 if (!Number.class.isAssignableFrom(wrapper2)) {

                     return Comparison.TYPE_1_BETTER;

                 }

             } else if (Number.class.isAssignableFrom(wrapper2)) {

                 return Comparison.TYPE_2_BETTER;

             }

             // If exactly one of the targets is a character, pick it. Numbers can be reasonably converted to chars using

             // the UTF-16 values.

             if (Character.class == wrapper1) {

                 return Comparison.TYPE_1_BETTER;

             } else if (Character.class == wrapper2) {

                 return Comparison.TYPE_2_BETTER;

             }

             // For all other cases, we fall through to the next if statement - not that we repeat the condition in it

             // too so if we entered this branch, we'll enter the below if statement too.

         }

         if (sourceType == String.class || sourceType == Boolean.class || Number.class.isAssignableFrom(sourceType)) {

             // Treat wrappers as primitives.

             final Class<?> primitiveType1 = getPrimitiveTypeOrSelf(targetType1);

             final Class<?> primitiveType2 = getPrimitiveTypeOrSelf(targetType2);

             // Basically, choose the widest possible primitive type. (First "if" returning TYPE_2_BETTER is correct;

             // when faced with a choice between double and int, choose double).

             if (TypeUtilities.isMethodInvocationConvertible(primitiveType1, primitiveType2)) {

                 return Comparison.TYPE_2_BETTER;

             } else if (TypeUtilities.isMethodInvocationConvertible(primitiveType2, primitiveType1)) {

                 return Comparison.TYPE_1_BETTER;

             }

             // Ok, at this point we're out of possible number conversions, so try strings. A String can represent any

             // value without loss, so if one of the potential targets is string, go for it.

             if (targetType1 == String.class) {

                 return Comparison.TYPE_1_BETTER;

             }

             if (targetType2 == String.class) {

                 return Comparison.TYPE_2_BETTER;

             }

         }

         return Comparison.INDETERMINATE;

     }

     private static Class<?> getPrimitiveTypeOrSelf(final Class<?> type) {

         final Class<?> primitive = TypeUtilities.getPrimitiveType(type);

         return primitive == null ? type : primitive;

     }

     private static Class<?> getWrapperTypeOrSelf(final Class<?> type) {

         final Class<?> wrapper = TypeUtilities.getWrapperType(type);

         return wrapper == null ? type : wrapper;

     }

     @SuppressWarnings("unused")

     private static boolean isJavaScriptPrimitive(final Object o) {

         return JSType.isString(o) || o instanceof Boolean || JSType.isNumber(o) || o == null;

     }

     private static final MethodHandle GUARD_PRIMITIVE = findOwnMH("isJavaScriptPrimitive", boolean.class, Object.class);

     private static MethodHandle findOwnMH(final String name, final Class<?> rtype, final Class<?>... types) {

         return MH.findStatic(MethodHandles.lookup(), NashornPrimitiveLinker.class, name, MH.type(rtype, types));

     }

 }