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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
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*
* 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).
*
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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 java.util.function.Supplier;
import jdk.dynalink.linker.ConversionComparator;
import jdk.dynalink.linker.GuardedInvocation;
import jdk.dynalink.linker.GuardingTypeConverterFactory;
import jdk.dynalink.linker.LinkRequest;
import jdk.dynalink.linker.LinkerServices;
import jdk.dynalink.linker.TypeBasedGuardingDynamicLinker;
import jdk.dynalink.linker.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;
import jdk.nashorn.internal.runtime.Symbol;
/**
* 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 GuardedInvocation VOID_TO_OBJECT =
new GuardedInvocation(MethodHandles.constant(Object.class, ScriptRuntime.UNDEFINED));
@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
|| type == Symbol.class;
}
@Override
public GuardedInvocation getGuardedInvocation(final LinkRequest request, final LinkerServices linkerServices)
throws Exception {
final Object self = request.getReceiver();
return Bootstrap.asTypeSafeReturn(Global.primitiveLookup(request, self), linkerServices, request.getCallSiteDescriptor());
}
/**
* 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 GuardedInvocation convertToType(final Class<?> sourceType, final Class<?> targetType, final Supplier<MethodHandles.Lookup> lookupSupplier) {
final MethodHandle mh = JavaArgumentConverters.getConverter(targetType);
if (mh == null) {
if(targetType == Object.class && sourceType == void.class) {
return VOID_TO_OBJECT;
}
return null;
}
return new GuardedInvocation(mh, canLinkTypeStatic(sourceType) ? null : GUARD_PRIMITIVE).asType(mh.type().changeParameterType(0, sourceType));
}
/**
* 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.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) {
/**代码未完, 请加载全部代码(NowJava.com).**/