JDK14/Java14源码在线阅读

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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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 * 2 along with this work; if not, write to the Free Software Foundation,
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package jdk.nashorn.internal.runtime;

import static jdk.nashorn.internal.lookup.Lookup.MH;
import static jdk.nashorn.internal.runtime.ECMAErrors.referenceError;
import static jdk.nashorn.internal.runtime.JSType.getAccessorTypeIndex;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.SwitchPoint;
import jdk.dynalink.CallSiteDescriptor;
import jdk.dynalink.linker.GuardedInvocation;
import jdk.dynalink.linker.LinkRequest;
import jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor;
import jdk.nashorn.internal.runtime.linker.NashornGuards;

/**
 * Instances of this class are quite ephemeral; they only exist for the duration of an invocation of
 * {@link ScriptObject#findSetMethod(CallSiteDescriptor, jdk.dynalink.linker.LinkRequest)} and
 * serve as the actual encapsulation of the algorithm for creating an appropriate property setter method.
 */
final class SetMethodCreator {
    // See constructor parameters for description of fields
    private final ScriptObject       sobj;
    private final PropertyMap        map;
    private final FindProperty       find;
    private final CallSiteDescriptor desc;
    private final Class<?>           type;
    private final LinkRequest        request;

    /**
     * Creates a new property setter method creator.
     * @param sobj the object for which we're creating the property setter
     * @param find a result of a {@link ScriptObject#findProperty(Object, boolean)} on the object for the property we
     * want to create a setter for. Can be null if the property does not yet exist on the object.
     * @param desc the descriptor of the call site that triggered the property setter lookup
     * @param request the link request
     */
    SetMethodCreator(final ScriptObject sobj, final FindProperty find, final CallSiteDescriptor desc, final LinkRequest request) {
        this.sobj    = sobj;
        this.map     = sobj.getMap();
        this.find    = find;
        this.desc    = desc;
        this.type    = desc.getMethodType().parameterType(1);
        this.request = request;
    }

    private String getName() {
        return NashornCallSiteDescriptor.getOperand(desc);
    }

    private PropertyMap getMap() {
        return map;
    }

    /**
     * Creates the actual guarded invocation that represents the dynamic setter method for the property.
     * @return the actual guarded invocation that represents the dynamic setter method for the property.
     */
    GuardedInvocation createGuardedInvocation(final SwitchPoint builtinSwitchPoint) {
        return createSetMethod(builtinSwitchPoint).createGuardedInvocation();
    }

    /**
     * This class encapsulates the results of looking up a setter method; it's basically a triple of a method handle,
     * a Property object, and flags for invocation.
     *
     */
    private class SetMethod {
        private final MethodHandle methodHandle;
        private final Property property;

        /**
         * Creates a new lookup result.
         * @param methodHandle the actual method handle
         * @param property the property object. Can be null in case we're creating a new property in the global object.
         */
        SetMethod(final MethodHandle methodHandle, final Property property) {
            assert methodHandle != null;
            this.methodHandle = methodHandle;
            this.property     = property;
        }

        /**
         * Composes from its components an actual guarded invocation that represents the dynamic setter method for the property.
         * @return the composed guarded invocation that represents the dynamic setter method for the property.
         */
        GuardedInvocation createGuardedInvocation() {
            // getGuard() and getException() either both return null, or neither does. The reason for that is that now
            // getGuard returns a map guard that casts its argument to ScriptObject, and if that fails, we need to
            // relink on ClassCastException.
            final boolean explicitInstanceOfCheck = NashornGuards.explicitInstanceOfCheck(desc, request);
            return new GuardedInvocation(methodHandle, NashornGuards.getGuard(sobj, property, desc, explicitInstanceOfCheck),
                    (SwitchPoint)null, explicitInstanceOfCheck ? null : ClassCastException.class);
        }
    }

    private SetMethod createSetMethod(final SwitchPoint builtinSwitchPoint) {
        if (find != null) {
            return createExistingPropertySetter();
        }

        checkStrictCreateNewVariable();

        if (sobj.isScope()) {
            return createGlobalPropertySetter();
        }

        return createNewPropertySetter(builtinSwitchPoint);
    }

    private void checkStrictCreateNewVariable() {
        // In strict mode, assignment can not create a new variable.
        // See also ECMA Annex C item 4. ReferenceError is thrown.
        if (NashornCallSiteDescriptor.isScope(desc) && NashornCallSiteDescriptor.isStrict(desc)) {
            throw referenceError("not.defined", getName());
        }
    }

    private SetMethod createExistingPropertySetter() {
        final Property property = find.getProperty();
        final boolean isStrict  = NashornCallSiteDescriptor.isStrict(desc);
        final MethodHandle methodHandle;

        if (NashornCallSiteDescriptor.isDeclaration(desc) && property.needsDeclaration()) {
            // This is a LET or CONST being declared. The property is already there but flagged as needing declaration.
            // We create a new PropertyMap with the flag removed. The map is installed with a fast compare-and-set
            // method if the pre-callsite map is stable (which should be the case for function scopes except for
            // non-strict functions containing eval() with var). Otherwise we have to use a slow setter that creates
            // a new PropertyMap on the fly.
            final PropertyMap oldMap = getMap();
            final Property newProperty = property.removeFlags(Property.NEEDS_DECLARATION);
            final PropertyMap newMap = oldMap.replaceProperty(property, newProperty);
            final MethodHandle fastSetter = find.replaceProperty(newProperty).getSetter(type, isStrict, request);
            final MethodHandle slowSetter = MH.insertArguments(ScriptObject.DECLARE_AND_SET, 1, getName()).asType(fastSetter.type());

            // cas map used as guard, if true that means we can do the set fast
            MethodHandle casMap = MH.insertArguments(ScriptObject.CAS_MAP, 1, oldMap, newMap);
            casMap = MH.dropArguments(casMap, 1, type);
            casMap = MH.asType(casMap, casMap.type().changeParameterType(0, Object.class));
            methodHandle = MH.guardWithTest(casMap, fastSetter, slowSetter);
        } else {
            methodHandle = find.getSetter(type, isStrict, request);
        }

        assert methodHandle != null;
        assert property     != null;

        final MethodHandle boundHandle;
        if (find.isInheritedOrdinaryProperty()) {
            boundHandle = ScriptObject.addProtoFilter(methodHandle, find.getProtoChainLength());
        } else {
            boundHandle = methodHandle;
        }
        return new SetMethod(boundHandle, property);
    }

    private SetMethod createGlobalPropertySetter() {
        final ScriptObject global = Context.getGlobal();
        return new SetMethod(MH.filterArguments(global.addSpill(type, getName()), 0, ScriptObject.GLOBALFILTER), null);
    }

    private SetMethod createNewPropertySetter(final SwitchPoint builtinSwitchPoint) {
        final SetMethod sm = map.getFreeFieldSlot() > -1 ? createNewFieldSetter(builtinSwitchPoint) : createNewSpillPropertySetter(builtinSwitchPoint);
        map.propertyChanged(sm.property);
        return sm;
    }

    private SetMethod createNewSetter(final Property property, final SwitchPoint builtinSwitchPoint) {
        property.setBuiltinSwitchPoint(builtinSwitchPoint);

        final PropertyMap oldMap   = getMap();
        final PropertyMap newMap   = getNewMap(property);
        final boolean     isStrict = NashornCallSiteDescriptor.isStrict(desc);
        final String      name     = NashornCallSiteDescriptor.getOperand(desc);

        //fast type specific setter
        final MethodHandle fastSetter = property.getSetter(type, newMap); //0 sobj, 1 value, slot folded for spill property already

        //slow setter, that calls ScriptObject.set with appropriate type and key name
        MethodHandle slowSetter = ScriptObject.SET_SLOW[getAccessorTypeIndex(type)];
        slowSetter = MH.insertArguments(slowSetter, 3, NashornCallSiteDescriptor.getFlags(desc));
        slowSetter = MH.insertArguments(slowSetter, 1, name);
        slowSetter = MH.asType(slowSetter, slowSetter.type().changeParameterType(0, Object.class));

        assert slowSetter.type().equals(fastSetter.type()) : "slow=" + slowSetter + " != fast=" + fastSetter;

        //cas map used as guard, if true that means we can do the set fast
        MethodHandle casMap = MH.insertArguments(ScriptObject.CAS_MAP, 1, oldMap, newMap);
        casMap = MH.dropArguments(casMap, 1, type);
        casMap = MH.asType(casMap, casMap.type().changeParameterType(0, Object.class));
        final MethodHandle casGuard = MH.guardWithTest(casMap, fastSetter, slowSetter);

        //outermost level needs an extendable check. if object can be extended, guard is true and
        //we can run the cas setter. The setter goes to "nop" VOID_RETURN if false or throws an
        //exception if we are in strict mode and object is not extensible

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