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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 ScriptObject.findSetMethod(CallSiteDescriptor, LinkRequest) and serve as the actual encapsulation of the algorithm for creating an appropriate property setter method.
/** * 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.
Params:
  • sobj – the object for which we're creating the property setter
  • find – a result of a 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.
  • desc – the descriptor of the call site that triggered the property setter lookup
  • request – the link 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.
Returns:the actual guarded invocation that represents the dynamic setter method for the property.
/** * 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.
/** * 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.
Params:
  • methodHandle – the actual method handle
  • property – the property object. Can be null in case we're creating a new property in the global object.
/** * 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.
Returns:the composed guarded invocation that represents the dynamic setter method for the 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.propertyAdded(sm.property, true); 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 MethodHandle extCheck = MH.insertArguments(ScriptObject.EXTENSION_CHECK, 1, isStrict, name); extCheck = MH.asType(extCheck, extCheck.type().changeParameterType(0, Object.class)); extCheck = MH.dropArguments(extCheck, 1, type); MethodHandle nop = JSType.VOID_RETURN.methodHandle(); nop = MH.dropArguments(nop, 0, Object.class, type); return new SetMethod(MH.asType(MH.guardWithTest(extCheck, casGuard, nop), fastSetter.type()), property); } private SetMethod createNewFieldSetter(final SwitchPoint builtinSwitchPoint) { return createNewSetter(new AccessorProperty(getName(), getFlags(sobj), sobj.getClass(), getMap().getFreeFieldSlot(), type), builtinSwitchPoint); } private SetMethod createNewSpillPropertySetter(final SwitchPoint builtinSwitchPoint) { return createNewSetter(new SpillProperty(getName(), getFlags(sobj), getMap().getFreeSpillSlot(), type), builtinSwitchPoint); } private PropertyMap getNewMap(final Property property) { return getMap().addProperty(property); } private static int getFlags(final ScriptObject scriptObject) { return scriptObject.useDualFields() ? Property.DUAL_FIELDS : 0; } }