runtime/linker/PrimitiveLookup.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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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.MethodType;
import jdk.internal.dynalink.CallSiteDescriptor;
import jdk.internal.dynalink.linker.GuardedInvocation;
import jdk.internal.dynalink.linker.LinkRequest;
import jdk.internal.dynalink.support.CallSiteDescriptorFactory;
import jdk.internal.dynalink.support.Guards;
import jdk.nashorn.internal.lookup.Lookup;
import jdk.nashorn.internal.runtime.FindProperty;
import jdk.nashorn.internal.runtime.ScriptObject;

/**
 * Implements lookup of methods to link for dynamic operations on JavaScript primitive values (booleans, strings, and
 * numbers). This class is only public so it can be accessed by classes in the {@code jdk.nashorn.internal.objects}
 * package.
 */
public final class PrimitiveLookup {

    private PrimitiveLookup() {
    }

    /**
     * Returns a guarded invocation representing the linkage for a dynamic operation on a primitive Java value.
     * @param request the link request for the dynamic call site.
     * @param receiverClass the class of the receiver value (e.g., {@link java.lang.Boolean}, {@link java.lang.String} etc.)
     * @param wrappedReceiver a transient JavaScript native wrapper object created as the object proxy for the primitive
     * value; see ECMAScript 5.1, section 8.7.1 for discussion of using {@code [[Get]]} on a property reference with a
     * primitive base value. This instance will be used to delegate actual lookup.
     * @param wrapFilter A method handle that takes a primitive value of type specified in the {@code receiverClass} and
     * creates a transient native wrapper of the same type as {@code wrappedReceiver} for subsequent invocations of the
     * method - it will be combined into the returned invocation as an argument filter on the receiver.
     * @return a guarded invocation representing the operation at the call site when performed on a JavaScript primitive
     * @param protoFilter A method handle that walks up the proto chain of this receiver object
     * type {@code receiverClass}.
     */
    public static GuardedInvocation lookupPrimitive(final LinkRequest request, final Class<?> receiverClass,
                                                    final ScriptObject wrappedReceiver, final MethodHandle wrapFilter,
                                                    final MethodHandle protoFilter) {
        return lookupPrimitive(request, Guards.getInstanceOfGuard(receiverClass), wrappedReceiver, wrapFilter, protoFilter);
    }

    /**
     * Returns a guarded invocation representing the linkage for a dynamic operation on a primitive Java value.
     * @param request the link request for the dynamic call site.
     * @param guard an explicit guard that will be used for the returned guarded invocation.
     * @param wrappedReceiver a transient JavaScript native wrapper object created as the object proxy for the primitive
     * value; see ECMAScript 5.1, section 8.7.1 for discussion of using {@code [[Get]]} on a property reference with a
     * primitive base value. This instance will be used to delegate actual lookup.
     * @param wrapFilter A method handle that takes a primitive value of type guarded by the {@code guard} and
     * creates a transient native wrapper of the same type as {@code wrappedReceiver} for subsequent invocations of the
     * method - it will be combined into the returned invocation as an argument filter on the receiver.
     * @param protoFilter A method handle that walks up the proto chain of this receiver object
     * @return a guarded invocation representing the operation at the call site when performed on a JavaScript primitive
     * type (that is implied by both {@code guard} and {@code wrappedReceiver}).
     */
    public static GuardedInvocation lookupPrimitive(final LinkRequest request, final MethodHandle guard,
                                                    final ScriptObject wrappedReceiver, final MethodHandle wrapFilter,
                                                    final MethodHandle protoFilter) {
        final CallSiteDescriptor desc = request.getCallSiteDescriptor();
        final String operator = CallSiteDescriptorFactory.tokenizeOperators(desc).get(0);
        if ("setProp".equals(operator) || "setElem".equals(operator)) {
            final MethodType type = desc.getMethodType();
            MethodHandle method = MH.asType(Lookup.EMPTY_SETTER, MH.type(void.class, Object.class, type.parameterType(1)));
            if (type.parameterCount() == 3) {
                method = MH.dropArguments(method, 2, type.parameterType(2));
            }
            return new GuardedInvocation(method, guard);
        }

        if(desc.getNameTokenCount() > 2) {
            final String name = desc.getNameToken(CallSiteDescriptor.NAME_OPERAND);
            final FindProperty find = wrappedReceiver.findProperty(name, true);
            if(find == null) {
                // Give up early, give chance to BeanLinker and NashornBottomLinker to deal with it.
                return null;
            } else if (find.isInherited() && !find.getProperty().hasGetterFunction(find.getOwner())) {
                // If property is found in the prototype object bind the method handle directly to
                // the proto filter instead of going through wrapper instantiation below.
                final ScriptObject proto = wrappedReceiver.getProto();
                final GuardedInvocation link = proto.lookup(desc, request);

                if (link != null) {
                    final MethodHandle invocation = link.getInvocation();
                    final MethodHandle adaptedInvocation = MH.asType(invocation, invocation.type().changeParameterType(0, Object.class));
                    final MethodHandle method = MH.filterArguments(adaptedInvocation, 0, protoFilter);
                    final MethodHandle protoGuard = MH.filterArguments(link.getGuard(), 0, protoFilter);
                    return new GuardedInvocation(method, NashornGuards.combineGuards(guard, protoGuard));
                }
            }
        }
        final GuardedInvocation link = wrappedReceiver.lookup(desc, request);
        if (link != null) {
            MethodHandle method = link.getInvocation();
            final Class<?> receiverType = method.type().parameterType(0);
            if (receiverType != Object.class) {
                final MethodType wrapType = wrapFilter.type();
                assert receiverType.isAssignableFrom(wrapType.returnType());
                method = MH.filterArguments(method, 0, MH.asType(wrapFilter, wrapType.changeReturnType(receiverType)));
            }
            return new GuardedInvocation(method, guard, link.getSwitchPoints(), null);
        }
        return null;
    }
}