Java example source code file (PrimitiveLookup.java)

This example Java source code file (PrimitiveLookup.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

callsitedescriptor, class, guardedinvocation, linkrequest, methodhandle, methodtype, primitivelookup, scriptobject, string

The PrimitiveLookup.java Java example source code

/*
 * 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
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

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.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
     * type {@code receiverClass}.
     */
    public static GuardedInvocation lookupPrimitive(final LinkRequest request, final Class<?> receiverClass,
                                                    final ScriptObject wrappedReceiver, final MethodHandle wrapFilter) {
        return lookupPrimitive(request, Guards.getInstanceOfGuard(receiverClass), wrappedReceiver, wrapFilter);
    }

    /**
     * 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.
     * @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 CallSiteDescriptor desc = request.getCallSiteDescriptor();
        final String operator = CallSiteDescriptorFactory.tokenizeOperators(desc).get(0);
        if ("setProp".equals(operator) || "setElem".equals(operator)) {
            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);
            if(wrappedReceiver.findProperty(name, true) == null) {
                // Give up early, give chance to BeanLinker and NashornBottomLinker to deal with it.
                return null;
            }
        }
        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.getSwitchPoint());
        }
        return null;
    }
}