Mercurial > jdk8-mips64-public > nashorn / file revision

 /*

  * 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;

 import static jdk.nashorn.internal.codegen.CompilerConstants.staticCall;

 import static jdk.nashorn.internal.codegen.CompilerConstants.virtualCall;

 import static jdk.nashorn.internal.codegen.CompilerConstants.virtualCallNoLookup;

 import static jdk.nashorn.internal.lookup.Lookup.MH;

 import static jdk.nashorn.internal.runtime.ECMAErrors.referenceError;

 import static jdk.nashorn.internal.runtime.ECMAErrors.typeError;

 import static jdk.nashorn.internal.runtime.PropertyDescriptor.CONFIGURABLE;

 import static jdk.nashorn.internal.runtime.PropertyDescriptor.ENUMERABLE;

 import static jdk.nashorn.internal.runtime.PropertyDescriptor.GET;

 import static jdk.nashorn.internal.runtime.PropertyDescriptor.SET;

 import static jdk.nashorn.internal.runtime.PropertyDescriptor.VALUE;

 import static jdk.nashorn.internal.runtime.PropertyDescriptor.WRITABLE;

 import static jdk.nashorn.internal.runtime.ScriptRuntime.UNDEFINED;

 import static jdk.nashorn.internal.runtime.arrays.ArrayIndex.getArrayIndexNoThrow;

 import static jdk.nashorn.internal.runtime.arrays.ArrayIndex.isValidArrayIndex;

 import java.lang.invoke.MethodHandle;

 import java.lang.invoke.MethodHandles;

 import java.lang.invoke.MethodType;

 import java.util.AbstractMap;

 import java.util.ArrayList;

 import java.util.Arrays;

 import java.util.Collection;

 import java.util.Collections;

 import java.util.HashSet;

 import java.util.Iterator;

 import java.util.LinkedHashSet;

 import java.util.List;

 import java.util.Map;

 import java.util.Set;

 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.nashorn.internal.codegen.CompilerConstants.Call;

 import jdk.nashorn.internal.codegen.ObjectClassGenerator;

 import jdk.nashorn.internal.lookup.Lookup;

 import jdk.nashorn.internal.lookup.MethodHandleFactory;

 import jdk.nashorn.internal.objects.AccessorPropertyDescriptor;

 import jdk.nashorn.internal.objects.DataPropertyDescriptor;

 import jdk.nashorn.internal.runtime.arrays.ArrayData;

 import jdk.nashorn.internal.runtime.linker.Bootstrap;

 import jdk.nashorn.internal.runtime.linker.LinkerCallSite;

 import jdk.nashorn.internal.runtime.linker.NashornCallSiteDescriptor;

 import jdk.nashorn.internal.runtime.linker.NashornGuards;

 /**

  * Base class for generic JavaScript objects.

  * <p>

  * Notes:

  * <ul>

  * <li>The map is used to identify properties in the object.</li>

  * <li>If the map is modified then it must be cloned and replaced.  This notifies

  *     any code that made assumptions about the object that things have changed.

  *     Ex. CallSites that have been validated must check to see if the map has

  *     changed (or a map from a different object type) and hence relink the method

  *     to call.</li>

  * <li>Modifications of the map include adding/deleting attributes or changing a

  *     function field value.</li>

  * </ul>

  */

 public abstract class ScriptObject extends PropertyListenerManager implements PropertyAccess {

     /** Search fall back routine name for "no such method" */

     static final String NO_SUCH_METHOD_NAME   = "__noSuchMethod__";

     /** Search fall back routine name for "no such property" */

     static final String NO_SUCH_PROPERTY_NAME = "__noSuchProperty__";

     /** Per ScriptObject flag - is this a scope object? */

     public static final int IS_SCOPE       = 0b0000_0001;

     /** Per ScriptObject flag - is this an array object? */

     public static final int IS_ARRAY       = 0b0000_0010;

     /** Per ScriptObject flag - is this an arguments object? */

     public static final int IS_ARGUMENTS   = 0b0000_0100;

     /** Spill growth rate - by how many elements does {@link ScriptObject#spill} when full */

     public static final int SPILL_RATE = 8;

     /** Map to property information and accessor functions. Ordered by insertion. */

     private PropertyMap map;

     /** Object flags. */

     private int flags;

     /** Area for properties added to object after instantiation, see {@link SpillProperty} */

     public Object[] spill;

     /** Local embed area position 0 - used for {@link SpillProperty} before {@link ScriptObject#spill} */

     public Object embed0;

     /** Local embed area position 1 - used for {@link SpillProperty} before {@link ScriptObject#spill} */

     public Object embed1;

     /** Local embed area position 2 - used for {@link SpillProperty} before {@link ScriptObject#spill} */

     public Object embed2;

     /** Local embed area position 3 - used for {@link SpillProperty} before {@link ScriptObject#spill} */

     public Object embed3;

     /** Indexed array data. */

     private ArrayData arrayData;

     static final MethodHandle SETEMBED           = findOwnMH("setEmbed",         void.class, CallSiteDescriptor.class, PropertyMap.class, PropertyMap.class, MethodHandle.class, int.class, Object.class, Object.class);

     static final MethodHandle SETSPILL           = findOwnMH("setSpill",         void.class, CallSiteDescriptor.class, PropertyMap.class, PropertyMap.class, int.class, Object.class, Object.class);

     static final MethodHandle SETSPILLWITHNEW    = findOwnMH("setSpillWithNew",  void.class, CallSiteDescriptor.class, PropertyMap.class, PropertyMap.class, int.class, Object.class, Object.class);

     static final MethodHandle SETSPILLWITHGROW   = findOwnMH("setSpillWithGrow", void.class, CallSiteDescriptor.class, PropertyMap.class, PropertyMap.class, int.class, int.class, Object.class, Object.class);

     private static final MethodHandle TRUNCATINGFILTER   = findOwnMH("truncatingFilter", Object[].class, int.class, Object[].class);

     private static final MethodHandle KNOWNFUNCPROPGUARD = findOwnMH("knownFunctionPropertyGuard", boolean.class, Object.class, PropertyMap.class, MethodHandle.class, Object.class, ScriptFunction.class);

     /** Method handle for getting a function argument at a given index. Used from MapCreator */

     public static final Call GET_ARGUMENT       = virtualCall(ScriptObject.class, "getArgument", Object.class, int.class);

     /** Method handle for setting a function argument at a given index. Used from MapCreator */

     public static final Call SET_ARGUMENT       = virtualCall(ScriptObject.class, "setArgument", void.class, int.class, Object.class);

     /** Method handle for getting the proto of a ScriptObject */

     public static final Call GET_PROTO          = virtualCallNoLookup(ScriptObject.class, "getProto", ScriptObject.class);

     /** Method handle for setting the proto of a ScriptObject */

     public static final Call SET_PROTO          = virtualCallNoLookup(ScriptObject.class, "setProto", void.class, ScriptObject.class);

     /** Method handle for setting the user accessors of a ScriptObject */

     public static final Call SET_USER_ACCESSORS = virtualCall(ScriptObject.class, "setUserAccessors", void.class, String.class, ScriptFunction.class, ScriptFunction.class);

     /** Method handle for getter for {@link UserAccessorProperty}, given a slot */

     static final Call USER_ACCESSOR_GETTER = staticCall(MethodHandles.lookup(), ScriptObject.class, "userAccessorGetter", Object.class, ScriptObject.class, int.class, Object.class);

     /** Method handle for setter for {@link UserAccessorProperty}, given a slot */

     static final Call USER_ACCESSOR_SETTER = staticCall(MethodHandles.lookup(), ScriptObject.class, "userAccessorSetter", void.class, ScriptObject.class, int.class, String.class, Object.class, Object.class);

     private static final MethodHandle INVOKE_UA_GETTER = Bootstrap.createDynamicInvoker("dyn:call", Object.class,

             Object.class, Object.class);

     private static final MethodHandle INVOKE_UA_SETTER = Bootstrap.createDynamicInvoker("dyn:call", void.class,

             Object.class, Object.class, Object.class);

     /**

      * Constructor

      */

     public ScriptObject() {

         this(null);

     }

     /**

     * Constructor

     *

     * @param map {@link PropertyMap} used to create the initial object

     */

     public ScriptObject(final PropertyMap map) {

         if (Context.DEBUG) {

             ScriptObject.count++;

         }

         this.arrayData = ArrayData.EMPTY_ARRAY;

         if (map == null) {

             this.setMap(PropertyMap.newMap(getClass()));

             return;

         }

         this.setMap(map);

     }

     /**

      * Copy all properties from the source object with their receiver bound to the source.

      * This function was known as mergeMap

      *

      * @param source The source object to copy from.

      */

     public void addBoundProperties(final ScriptObject source) {

         PropertyMap newMap = this.getMap();

         for (final Property property : source.getMap().getProperties()) {

             final String key = property.getKey();

             if (newMap.findProperty(key) == null) {

                 if (property instanceof UserAccessorProperty) {

                     final UserAccessorProperty prop = this.newUserAccessors(key, property.getFlags(), property.getGetterFunction(source), property.getSetterFunction(source));

                     newMap = newMap.addProperty(prop);

                 } else {

                     newMap = newMap.newPropertyBind((AccessorProperty)property, source);

                 }

             }

         }

         this.setMap(newMap);

     }

     /**

      * Bind the method handle to the specified receiver, while preserving its original type (it will just ignore the

      * first argument in lieu of the bound argument).

      * @param methodHandle Method handle to bind to.

      * @param receiver     Object to bind.

      * @return Bound method handle.

      */

     static MethodHandle bindTo(final MethodHandle methodHandle, final Object receiver) {

         return MH.dropArguments(MH.bindTo(methodHandle, receiver), 0, methodHandle.type().parameterType(0));

     }

     /**

      * Return a property iterator.

      * @return Property iterator.

      */

     public Iterator<String> propertyIterator() {

         return new KeyIterator(this);

     }

     /**

      * Return a property value iterator.

      * @return Property value iterator.

      */

     public Iterator<Object> valueIterator() {

         return new ValueIterator(this);

     }

     /**

      * ECMA 8.10.1 IsAccessorDescriptor ( Desc )

      * @return true if this has a {@link AccessorPropertyDescriptor} with a getter or a setter

      */

     public final boolean isAccessorDescriptor() {

         return has(GET) || has(SET);

     }

     /**

      * ECMA 8.10.2 IsDataDescriptor ( Desc )

      * @return true if this has a {@link DataPropertyDescriptor}, i.e. the object has a property value and is writable

      */

     public final boolean isDataDescriptor() {

         return has(VALUE) || has(WRITABLE);

     }

     /**

      * ECMA 8.10.3 IsGenericDescriptor ( Desc )

      * @return true if this has a descriptor describing an {@link AccessorPropertyDescriptor} or {@link DataPropertyDescriptor}

      */

     public final boolean isGenericDescriptor() {

         return isAccessorDescriptor() || isDataDescriptor();

     }

     /**

       * ECMA 8.10.5 ToPropertyDescriptor ( Obj )

       *

       * @return property descriptor

       */

     public final PropertyDescriptor toPropertyDescriptor() {

         final GlobalObject global = (GlobalObject) Context.getGlobalTrusted();

         final PropertyDescriptor desc;

         if (isDataDescriptor()) {

             if (has(SET) || has(GET)) {

                 throw typeError((ScriptObject)global, "inconsistent.property.descriptor");

             }

             desc = global.newDataDescriptor(UNDEFINED, false, false, false);

         } else if (isAccessorDescriptor()) {

             if (has(VALUE) || has(WRITABLE)) {

                 throw typeError((ScriptObject)global, "inconsistent.property.descriptor");

             }

             desc = global.newAccessorDescriptor(UNDEFINED, UNDEFINED, false, false);

         } else {

             desc = global.newGenericDescriptor(false, false);

         }

         return desc.fillFrom(this);

     }

     /**

      * ECMA 8.10.5 ToPropertyDescriptor ( Obj )

      *

      * @param global  global scope object

      * @param obj object to create property descriptor from

      *

      * @return property descriptor

      */

     public static PropertyDescriptor toPropertyDescriptor(final ScriptObject global, final Object obj) {

         if (obj instanceof ScriptObject) {

             return ((ScriptObject)obj).toPropertyDescriptor();

         }

         throw typeError(global, "not.an.object", ScriptRuntime.safeToString(obj));

     }

     /**

      * ECMA 8.12.1 [[GetOwnProperty]] (P)

      *

      * @param key property key

      *

      * @return Returns the Property Descriptor of the named own property of this

      * object, or undefined if absent.

      */

     public Object getOwnPropertyDescriptor(final String key) {

         final Property property = getMap().findProperty(key);

         final GlobalObject global = (GlobalObject)Context.getGlobalTrusted();

         if (property != null) {

             final ScriptFunction get   = property.getGetterFunction(this);

             final ScriptFunction set   = property.getSetterFunction(this);

             final boolean configurable = property.isConfigurable();

             final boolean enumerable   = property.isEnumerable();

             final boolean writable     = property.isWritable();

             if (property instanceof UserAccessorProperty) {

                 return global.newAccessorDescriptor(

                     (get != null) ?

                         get :

                         UNDEFINED,

                     (set != null) ?

                         set :

                         UNDEFINED,

                     configurable,

                     enumerable);

             }

             return global.newDataDescriptor(getWithProperty(property), configurable, enumerable, writable);

         }

         final int index = getArrayIndexNoThrow(key);

         final ArrayData array = getArray();

         if (array.has(index)) {

             return array.getDescriptor(global, index);

         }

         return UNDEFINED;

     }

     /**

      * ECMA 8.12.2 [[GetProperty]] (P)

      *

      * @param key property key

      *

      * @return Returns the fully populated Property Descriptor of the named property

      * of this object, or undefined if absent.

      */

     public Object getPropertyDescriptor(final String key) {

         final Object res = getOwnPropertyDescriptor(key);

         if (res != UNDEFINED) {

             return res;

         } else if (getProto() != null) {

             return getProto().getOwnPropertyDescriptor(key);

         } else {

             return UNDEFINED;

         }

     }

     /**

      * ECMA 8.12.9 [[DefineOwnProperty]] (P, Desc, Throw)

      *

      * @param key the property key

      * @param propertyDesc the property descriptor

      * @param reject is the property extensible - true means new definitions are rejected

      *

      * @return true if property was successfully defined

      */

     public boolean defineOwnProperty(final String key, final Object propertyDesc, final boolean reject) {

         final ScriptObject       global  = Context.getGlobalTrusted();

         final PropertyDescriptor desc    = toPropertyDescriptor(global, propertyDesc);

         final Object             current = getOwnPropertyDescriptor(key);

         final String             name    = JSType.toString(key);

         if (current == UNDEFINED) {

             if (isExtensible()) {

                 // add a new own property

                 addOwnProperty(key, desc);

                 return true;

             }

             // new property added to non-extensible object

             if (reject) {

                 throw typeError(global, "object.non.extensible", name, ScriptRuntime.safeToString(this));

             }

             return false;

         }

         // modifying an existing property

         final PropertyDescriptor currentDesc = (PropertyDescriptor) current;

         final PropertyDescriptor newDesc     = desc;

         if (newDesc.type() == PropertyDescriptor.GENERIC &&

             ! newDesc.has(CONFIGURABLE) && ! newDesc.has(ENUMERABLE)) {

             // every descriptor field is absent

             return true;

         }

         if (currentDesc.equals(newDesc)) {

             // every descriptor field of the new is same as the current

             return true;

         }

         if (! currentDesc.isConfigurable()) {

             if (newDesc.has(CONFIGURABLE) && newDesc.isConfigurable()) {

                 // not configurable can not be made configurable

                 if (reject) {

                     throw typeError(global, "cant.redefine.property", name, ScriptRuntime.safeToString(this));

                 }

                 return false;

             }

             if (newDesc.has(ENUMERABLE) &&

                 currentDesc.isEnumerable() != newDesc.isEnumerable()) {

                 // cannot make non-enumerable as enumerable or vice-versa

                 if (reject) {

                     throw typeError(global, "cant.redefine.property", name, ScriptRuntime.safeToString(this));

                 }

                 return false;

             }

         }

         int propFlags = Property.mergeFlags(currentDesc, newDesc);

         Property property = getMap().findProperty(key);

         if (currentDesc.type() == PropertyDescriptor.DATA &&

             (newDesc.type() == PropertyDescriptor.DATA || newDesc.type() == PropertyDescriptor.GENERIC)) {

             if (! currentDesc.isConfigurable() && ! currentDesc.isWritable()) {

                 if (newDesc.has(WRITABLE) && newDesc.isWritable() ||

                     newDesc.has(VALUE) && ! ScriptRuntime.sameValue(currentDesc.getValue(), newDesc.getValue())) {

                     if (reject) {

                         throw typeError(global, "cant.redefine.property", name, ScriptRuntime.safeToString(this));

                     }

                     return false;

                 }

             }

             final boolean newValue = newDesc.has(VALUE);

             final Object value     = newValue? newDesc.getValue() : currentDesc.getValue();

             if (newValue && property != null) {

                 // Temporarily clear flags.

                 property = modifyOwnProperty(property, 0);

                 set(key, value, getContext()._strict);

             }

             if (property == null) {

                 // promoting an arrayData value to actual property

                 addOwnProperty(key, propFlags, value);

                 removeArraySlot(key);

             } else {

                 // Now set the new flags

                 modifyOwnProperty(property, propFlags);

             }

         } else if (currentDesc.type() == PropertyDescriptor.ACCESSOR &&

                    (newDesc.type() == PropertyDescriptor.ACCESSOR ||

                     newDesc.type() == PropertyDescriptor.GENERIC)) {

             if (! currentDesc.isConfigurable()) {

                 if (newDesc.has(PropertyDescriptor.GET) && ! ScriptRuntime.sameValue(currentDesc.getGetter(), newDesc.getGetter()) ||

                     newDesc.has(PropertyDescriptor.SET) && ! ScriptRuntime.sameValue(currentDesc.getSetter(), newDesc.getSetter())) {

                     if (reject) {

                         throw typeError(global, "cant.redefine.property", name, ScriptRuntime.safeToString(this));

                     }

                     return false;

                 }

             }

             // New set the new features.

             modifyOwnProperty(property, propFlags,

                                       newDesc.has(GET) ? newDesc.getGetter() : currentDesc.getGetter(),

                                       newDesc.has(SET) ? newDesc.getSetter() : currentDesc.getSetter());

         } else {

             // changing descriptor type

             if (! currentDesc.isConfigurable()) {

                 // not configurable can not be made configurable

                 if (reject) {

                     throw typeError(global, "cant.redefine.property", name, ScriptRuntime.safeToString(this));

                 }

                 return false;

             }

             propFlags = 0;

             // Preserve only configurable and enumerable from current desc

             // if those are not overridden in the new property descriptor.

             boolean value = newDesc.has(CONFIGURABLE)? newDesc.isConfigurable() : currentDesc.isConfigurable();

             if (!value) {

                 propFlags |= Property.NOT_CONFIGURABLE;

             }

             value = newDesc.has(ENUMERABLE)? newDesc.isEnumerable() : currentDesc.isEnumerable();

             if (!value) {

                 propFlags |= Property.NOT_ENUMERABLE;

             }

             final int type = newDesc.type();

             if (type == PropertyDescriptor.DATA) {

                 // get writable from the new descriptor

                 value = newDesc.has(WRITABLE) && newDesc.isWritable();

                 if (! value) {

                     propFlags |= Property.NOT_WRITABLE;

                 }

                 // delete the old property

                 deleteOwnProperty(property);

                 // add new data property

                 addOwnProperty(key, propFlags, newDesc.getValue());

             } else if (type == PropertyDescriptor.ACCESSOR) {

                 if (property == null) {

                     addOwnProperty(key, propFlags,

                                      newDesc.has(GET) ? newDesc.getGetter() : null,

                                      newDesc.has(SET) ? newDesc.getSetter() : null);

                 } else {

                     // Modify old property with the new features.

                     modifyOwnProperty(property, propFlags,

                                         newDesc.has(GET) ? newDesc.getGetter() : null,

                                         newDesc.has(SET) ? newDesc.getSetter() : null);

                 }

             }

         }

         checkIntegerKey(key);

         return true;

     }

     /**

      * Spec. mentions use of [[DefineOwnProperty]] for indexed properties in

      * certain places (eg. Array.prototype.map, filter). We can not use ScriptObject.set

      * method in such cases. This is because set method uses inherited setters (if any)

      * from any object in proto chain such as Array.prototype, Object.prototype.

      * This method directly sets a particular element value in the current object.

      *

      * @param index index key for property

      * @param value value to define

      */

     protected final void defineOwnProperty(final int index, final Object value) {

         if (index >= getArray().length()) {

             // make array big enough to hold..

             setArray(getArray().ensure(index));

         }

         setArray(getArray().set(index, value, false));

     }

     private void checkIntegerKey(final String key) {

         final int index = getArrayIndexNoThrow(key);

         if (isValidArrayIndex(index)) {

             final ArrayData data = getArray();

             if (data.has(index)) {

                 setArray(data.delete(index));

             }

         }

     }

     private void removeArraySlot(final String key) {

         final int index = getArrayIndexNoThrow(key);

         final ArrayData array = getArray();

         if (array.has(index)) {

             setArray(array.delete(index));

         }

     }

     /**

       * Add a new property to the object.

       *

       * @param key          property key

       * @param propertyDesc property descriptor for property

       */

     public final void addOwnProperty(final String key, final PropertyDescriptor propertyDesc) {

         // Already checked that there is no own property with that key.

         PropertyDescriptor pdesc = propertyDesc;

         final int propFlags = Property.toFlags(pdesc);

         if (pdesc.type() == PropertyDescriptor.GENERIC) {

             final GlobalObject global = (GlobalObject) Context.getGlobalTrusted();

             final PropertyDescriptor dDesc = global.newDataDescriptor(UNDEFINED, false, false, false);

             dDesc.fillFrom((ScriptObject)pdesc);

             pdesc = dDesc;

         }

         final int type = pdesc.type();

         if (type == PropertyDescriptor.DATA) {

             addOwnProperty(key, propFlags, pdesc.getValue());

         } else if (type == PropertyDescriptor.ACCESSOR) {

             addOwnProperty(key, propFlags,

                     pdesc.has(GET) ? pdesc.getGetter() : null,

                     pdesc.has(SET) ? pdesc.getSetter() : null);

         }

         checkIntegerKey(key);

     }

     /**

      * Low level property API (not using property descriptors)

      * <p>

      * Find a property in the prototype hierarchy. Note: this is final and not

      * a good idea to override. If you have to, use

      * {jdk.nashorn.internal.objects.NativeArray{@link #getProperty(String)} or

      * {jdk.nashorn.internal.objects.NativeArray{@link #getPropertyDescriptor(String)} as the

      * overriding way to find array properties

      *

      * @see jdk.nashorn.internal.objects.NativeArray

      *

      * @param key  Property key.

      * @param deep Whether the search should look up proto chain.

      *

      * @return FindPropertyData or null if not found.

      */

     public final FindProperty findProperty(final String key, final boolean deep) {

         return findProperty(key, deep, false, this);

     }

     /**

      * Low level property API (not using property descriptors)

      * <p>

      * Find a property in the prototype hierarchy. Note: this is not a good idea

      * to override except as it was done in {@link WithObject}.

      * If you have to, use

      * {jdk.nashorn.internal.objects.NativeArray{@link #getProperty(String)} or

      * {jdk.nashorn.internal.objects.NativeArray{@link #getPropertyDescriptor(String)} as the

      * overriding way to find array properties

      *

      * @see jdk.nashorn.internal.objects.NativeArray

      *

      * @param key  Property key.

      * @param deep Whether the search should look up proto chain.

      * @param stopOnNonScope should a deep search stop on the first non-scope object?

      * @param start the object on which the lookup was originally initiated

      *

      * @return FindPropertyData or null if not found.

      */

     FindProperty findProperty(final String key, final boolean deep, final boolean stopOnNonScope, final ScriptObject start) {

         // if doing deep search, stop search on the first non-scope object if asked to do so

         if (stopOnNonScope && start != this && !isScope()) {

             return null;

         }

         final PropertyMap selfMap  = getMap();

         final Property    property = selfMap.findProperty(key);

         if (property != null) {

             return new FindProperty(start, this, property);

         }

         if (deep) {

             final ScriptObject proto = getProto();

             if(proto != null) {

                 return proto.findProperty(key, deep, stopOnNonScope, start);

             }

         }

         return null;

     }

     /**

      * Add a new property to the object.

      * <p>

      * This a more "low level" way that doesn't involve {@link PropertyDescriptor}s

      *

      * @param key             Property key.

      * @param propertyFlags   Property flags.

      * @param getter          Property getter, or null if not defined

      * @param setter          Property setter, or null if not defined

      *

      * @return New property.

      */

     public final Property addOwnProperty(final String key, final int propertyFlags, final ScriptFunction getter, final ScriptFunction setter) {

         return addOwnProperty(newUserAccessors(key, propertyFlags, getter, setter));

     }

     /**

      * Add a new property to the object.

      * <p>

      * This a more "low level" way that doesn't involve {@link PropertyDescriptor}s

      *

      * @param key             Property key.

      * @param propertyFlags   Property flags.

      * @param value           Value of property

      *

      * @return New property.

      */

     public final Property addOwnProperty(final String key, final int propertyFlags, final Object value) {

         final MethodHandle setter = addSpill(key, propertyFlags);

         try {

             setter.invokeExact((Object)this, value);

         } catch (final Error|RuntimeException e) {

             throw e;

         } catch (final Throwable e) {

             throw new RuntimeException(e);

         }

         return getMap().findProperty(key);

     }

     /**

      * Add a new property to the object.

      * <p>

      * This a more "low level" way that doesn't involve {@link PropertyDescriptor}s

      *

      * @param newProperty property to add

      *

      * @return New property.

      */

     public final Property addOwnProperty(final Property newProperty) {

         PropertyMap oldMap = getMap();

         while (true) {

             final PropertyMap newMap = oldMap.addProperty(newProperty);

             if (!compareAndSetMap(oldMap, newMap)) {

                 oldMap = getMap();

                 final Property oldProperty = oldMap.findProperty(newProperty.getKey());

                 if (oldProperty != null) {

                     return oldProperty;

                 }

             } else {

                 return newProperty;

             }

         }

     }

     private void erasePropertyValue(final Property property) {

         // Erase the property field value with undefined. If the property is defined

         // by user-defined accessors, we don't want to call the setter!!

         if (!(property instanceof UserAccessorProperty)) {

             try {

                 // make the property value to be undefined

                 //TODO specproperties

                 property.getSetter(Object.class, getMap()).invokeExact((Object)this, (Object)UNDEFINED);

             } catch (final RuntimeException | Error e) {

                 throw e;

             } catch (final Throwable t) {

                 throw new RuntimeException(t);

             }

         }

     }

     /**

      * Delete a property from the object.

      *

      * @param property Property to delete.

      *

      * @return true if deleted.

      */

     public final boolean deleteOwnProperty(final Property property) {

         erasePropertyValue(property);

         PropertyMap oldMap = getMap();

         while (true) {

             final PropertyMap newMap = oldMap.deleteProperty(property);

             if (newMap == null) {

                 return false;

             }

             if (!compareAndSetMap(oldMap, newMap)) {

                 oldMap = getMap();

             } else {

                 // delete getter and setter function references so that we don't leak

                 if (property instanceof UserAccessorProperty) {

                     final UserAccessorProperty uc = (UserAccessorProperty) property;

                     setEmbedOrSpill(uc.getGetterSlot(), null);

                     setEmbedOrSpill(uc.getSetterSlot(), null);

                 }

                 return true;

             }

         }

     }

     /**

      * Modify a property in the object

      *

      * @param oldProperty    property to modify

      * @param propertyFlags  new property flags

      * @param getter         getter for {@link UserAccessorProperty}, null if not present or N/A

      * @param setter         setter for {@link UserAccessorProperty}, null if not present or N/A

      *

      * @return new property

      */

     public final Property modifyOwnProperty(final Property oldProperty, final int propertyFlags, final ScriptFunction getter, final ScriptFunction setter) {

         Property newProperty;

         if (oldProperty instanceof UserAccessorProperty) {

             // re-use the slots of the old user accessor property.

             final UserAccessorProperty uc = (UserAccessorProperty) oldProperty;

             int getterSlot = uc.getGetterSlot();

             // clear the old getter and set the new getter

             setEmbedOrSpill(getterSlot, getter);

             // if getter function is null, flag the slot to be negative (less by 1)

             if (getter == null) {

                 getterSlot = -getterSlot - 1;

             }

             int setterSlot = uc.getSetterSlot();

             // clear the old setter and set the new setter

             setEmbedOrSpill(setterSlot, setter);

             // if setter function is null, flag the slot to be negative (less by 1)

             if (setter == null) {

                 setterSlot = -setterSlot - 1;

             }

             newProperty = new UserAccessorProperty(oldProperty.getKey(), propertyFlags, getterSlot, setterSlot);

             // if just flipping getter and setter with new functions, no need to change property or map

             if (oldProperty.equals(newProperty)) {

                 return oldProperty;

             }

         } else {

             // erase old property value and create new user accessor property

             erasePropertyValue(oldProperty);

             newProperty = newUserAccessors(oldProperty.getKey(), propertyFlags, getter, setter);

         }

         notifyPropertyModified(this, oldProperty, newProperty);

         return modifyOwnProperty(oldProperty, newProperty);

     }

     /**

       * Modify a property in the object

       *

       * @param oldProperty    property to modify

       * @param propertyFlags  new property flags

       *

       * @return new property

       */

     public final Property modifyOwnProperty(final Property oldProperty, final int propertyFlags) {

         return modifyOwnProperty(oldProperty, oldProperty.setFlags(propertyFlags));

     }

     /**

      * Modify a property in the object, replacing a property with a new one

      *

      * @param oldProperty   property to replace

      * @param newProperty   property to replace it with

      *

      * @return new property

      */

     private Property modifyOwnProperty(final Property oldProperty, final Property newProperty) {

         assert newProperty.getKey().equals(oldProperty.getKey()) : "replacing property with different key";

         PropertyMap oldMap = getMap();

         while (true) {

             final PropertyMap newMap = oldMap.replaceProperty(oldProperty, newProperty);

             if (!compareAndSetMap(oldMap, newMap)) {

                 oldMap = getMap();

                 final Property oldPropertyLookup = oldMap.findProperty(oldProperty.getKey());

                 if (oldPropertyLookup != null && oldPropertyLookup.equals(newProperty)) {

                     return oldPropertyLookup;

                 }

             } else {

                 return newProperty;

             }

         }

     }

     /**

      * Update getter and setter in an object literal.

      *

      * @param key    Property key.

      * @param getter {@link UserAccessorProperty} defined getter, or null if none

      * @param setter {@link UserAccessorProperty} defined setter, or null if none

      */

     public final void setUserAccessors(final String key, final ScriptFunction getter, final ScriptFunction setter) {

         final Property oldProperty = getMap().findProperty(key);

         if (oldProperty != null) {

             final UserAccessorProperty newProperty = newUserAccessors(oldProperty.getKey(), oldProperty.getFlags(), getter, setter);

             modifyOwnProperty(oldProperty, newProperty);

         } else {

             final UserAccessorProperty newProperty = newUserAccessors(key, 0, getter, setter);

             addOwnProperty(newProperty);

         }

     }

     private static int getIntValue(final FindProperty find) {

         final MethodHandle getter = find.getGetter(int.class);

         if (getter != null) {

             try {

                 return (int)getter.invokeExact((Object)find.getGetterReceiver());

             } catch (final Error|RuntimeException e) {

                 throw e;

             } catch (final Throwable e) {

                 throw new RuntimeException(e);

             }

         }

         return ObjectClassGenerator.UNDEFINED_INT;

     }

     private static long getLongValue(final FindProperty find) {

         final MethodHandle getter = find.getGetter(long.class);

         if (getter != null) {

             try {

                 return (long)getter.invokeExact((Object)find.getGetterReceiver());

             } catch (final Error|RuntimeException e) {

                 throw e;

             } catch (final Throwable e) {

                 throw new RuntimeException(e);

             }

         }

         return ObjectClassGenerator.UNDEFINED_LONG;

     }

     private static double getDoubleValue(final FindProperty find) {

         final MethodHandle getter = find.getGetter(double.class);

         if (getter != null) {

             try {

                 return (double)getter.invokeExact((Object)find.getGetterReceiver());

             } catch (final Error|RuntimeException e) {

                 throw e;

             } catch (final Throwable e) {

                 throw new RuntimeException(e);

             }

         }

         return ObjectClassGenerator.UNDEFINED_DOUBLE;

     }

     /**

       * Get the object value of a property

       *

       * @param find {@link FindProperty} lookup result

       *

       * @return the value of the property

       */

     protected static Object getObjectValue(final FindProperty find) {

         final MethodHandle getter = find.getGetter(Object.class);

         if (getter != null) {

             try {

                 return getter.invokeExact((Object)find.getGetterReceiver());

             } catch (final Error|RuntimeException e) {

                 throw e;

             } catch (final Throwable e) {

                 throw new RuntimeException(e);

             }

         }

         return UNDEFINED;

     }

     /**

      * Return methodHandle of value function for call.

      *

      * @param find      data from find property.

      * @param type      method type of function.

      * @param bindName  null or name to bind to second argument (property not found method.)

      *

      * @return value of property as a MethodHandle or null.

      *

      */

     @SuppressWarnings("static-method")

     protected MethodHandle getCallMethodHandle(final FindProperty find, final MethodType type, final String bindName) {

         return getCallMethodHandle(getObjectValue(find), type, bindName);

     }

     /**

      * Return methodHandle of value function for call.

      *

      * @param value     value of receiver, it not a {@link ScriptFunction} this will return null.

      * @param type      method type of function.

      * @param bindName  null or name to bind to second argument (property not found method.)

      *

      * @return value of property as a MethodHandle or null.

      */

     protected static MethodHandle getCallMethodHandle(final Object value, final MethodType type, final String bindName) {

         return value instanceof ScriptFunction ? ((ScriptFunction)value).getCallMethodHandle(type, bindName) : null;

     }

     /**

      * Get value using found property.

      *

      * @param property Found property.

      *

      * @return Value of property.

      */

     public final Object getWithProperty(final Property property) {

         return getObjectValue(new FindProperty(this, this, property));

     }

     /**

      * Get a property given a key

      *

      * @param key property key

      *

      * @return property for key

      */

     public final Property getProperty(final String key) {

         return getMap().findProperty(key);

     }

     static String convertKey(final Object key) {

         return (key instanceof String) ? (String)key : JSType.toString(key);

     }

     /**

      * Overridden by {@link jdk.nashorn.internal.objects.NativeArguments} class (internal use.)

      * Used for argument access in a vararg function using parameter name.

      * Returns the argument at a given key (index)

      *

      * @param key argument index

      *

      * @return the argument at the given position, or undefined if not present

      */

     public Object getArgument(final int key) {

         return get(key);

     }

     /**

      * Overridden by {@link jdk.nashorn.internal.objects.NativeArguments} class (internal use.)

      * Used for argument access in a vararg function using parameter name.

      * Returns the argument at a given key (index)

      *

      * @param key   argument index

      * @param value the value to write at the given index

      */

     public void setArgument(final int key, final Object value) {

         set(key, value, getContext()._strict);

     }

     /**

      * Return true if the script object context is strict

      * @return true if strict context

      */

     public final boolean isStrictContext() {

         return getContext()._strict;

     }

     /**

      * Return the current context from the object's map.

      * @return Current context.

      */

     final Context getContext() {

         return getMap().getContext();

     }

     /**

      * Return the map of an object.

      * @return PropertyMap object.

      */

     public final PropertyMap getMap() {

         return map;

     }

     /**

      * Set the initial map.

      * @param map Initial map.

      */

     public final void setMap(final PropertyMap map) {

         this.map = map;

     }

     /**

      * Conditionally set the new map if the old map is the same.

      * @param oldMap Map prior to manipulation.

      * @param newMap Replacement map.

      * @return true if the operation succeeded.

      */

     protected synchronized final boolean compareAndSetMap(final PropertyMap oldMap, final PropertyMap newMap) {

         final boolean update = oldMap == this.map;

         if (update) {

             this.map = newMap;

         }

         return update;

      }

     /**

      * Return the __proto__ of an object.

      * @return __proto__ object.

      */

     public final ScriptObject getProto() {

         return getMap().getProto();

     }

     /**

      * Check if this is a prototype

      * @return true if {@link PropertyMap#isPrototype()} is true for this ScriptObject

      */

     public final boolean isPrototype() {

         return getMap().isPrototype();

     }

     /**

      * Set the __proto__ of an object.

      * @param newProto new __proto__ to set.

      */

     public final void setProto(final ScriptObject newProto) {

         PropertyMap  oldMap   = getMap();

         ScriptObject oldProto = getProto();

         while (oldProto != newProto) {

             final PropertyMap newMap = oldMap.setProto(newProto);

             if (!compareAndSetMap(oldMap, newMap)) {

                 oldMap = getMap();

                 oldProto = getProto();

             } else {

                 if (isPrototype()) {

                     if (oldProto != null) {

                         oldProto.removePropertyListener(this);

                     }

                     if (newProto != null) {

                         newProto.addPropertyListener(this);

                     }

                 }

                 return;

             }

         }

     }

     /**

      * Set the __proto__ of an object with checks.

      * @param newProto Prototype to set.

      */

     public final void setProtoCheck(final Object newProto) {

         if (newProto == null || newProto instanceof ScriptObject) {

             setProto((ScriptObject)newProto);

         } else {

             final ScriptObject global = Context.getGlobalTrusted();

             final Object  newProtoObject = JSType.toScriptObject(global, newProto);

             if (newProtoObject instanceof ScriptObject) {

                 setProto((ScriptObject)newProtoObject);

             } else {

                 throw typeError(global, "cant.set.proto.to.non.object", ScriptRuntime.safeToString(this), ScriptRuntime.safeToString(newProto));

             }

         }

     }

     /**

      * return a List of own keys associated with the object.

      * @param all True if to include non-enumerable keys.

      * @return Array of keys.

      */

     public String[] getOwnKeys(final boolean all) {

         final List<Object> keys    = new ArrayList<>();

         final PropertyMap  selfMap = this.getMap();

         final ArrayData array  = getArray();

         final long length      = array.length();

         for (long i = 0; i < length; i = array.nextIndex(i)) {

             if (array.has((int)i)) {

                 keys.add(JSType.toString(i));

             }

         }

         for (final Property property : selfMap.getProperties()) {

             if (all || property.isEnumerable()) {

                 keys.add(property.getKey());

             }

         }

         return keys.toArray(new String[keys.size()]);

     }

     /**

      * Check if this ScriptObject has array entries. This means that someone has

      * set values with numeric keys in the object.

      *

      * Note: this can be O(n) up to the array length

      *

      * @return true if array entries exists.

      */

     public boolean hasArrayEntries() {

         final ArrayData array = getArray();

         final long length = array.length();

         for (long i = 0; i < length; i++) {

             if (array.has((int)i)) {

                 return true;

             }

         }

         return false;

     }

     /**

      * Return the valid JavaScript type name descriptor

      *

      * @return "Object"

      */

     public String getClassName() {

         return "Object";

     }

     /**

      * {@code length} is a well known property. This is its getter.

      * Note that this *may* be optimized by other classes

      *

      * @return length property value for this ScriptObject

      */

     public Object getLength() {

         return get("length");

     }

     /**

      * Stateless toString for ScriptObjects.

      *

      * @return string description of this object, e.g. {@code [object Object]}

      */

     public String safeToString() {

         return "[object " + getClassName() + "]";

     }

     /**

      * Return the default value of the object with a given preferred type hint.

      * The preferred type hints are String.class for type String, Number.class

      * for type Number. <p>

      *

      * A <code>hint</code> of null means "no hint".

      *

      * ECMA 8.12.8 [[DefaultValue]](hint)

      *

      * @param typeHint the preferred type hint

      * @return the default value

      */

     public Object getDefaultValue(final Class<?> typeHint) {

         // We delegate to GlobalObject, as the implementation uses dynamic call sites to invoke object's "toString" and

         // "valueOf" methods, and in order to avoid those call sites from becoming megamorphic when multiple contexts

         // are being executed in a long-running program, we move the code and their associated dynamic call sites

         // (Global.TO_STRING and Global.VALUE_OF) into per-context code.

         return ((GlobalObject)Context.getGlobalTrusted()).getDefaultValue(this, typeHint);

     }

     /**

      * Checking whether a script object is an instance of another. Used

      * in {@link ScriptFunction} for hasInstance implementation, walks

      * the proto chain

      *

      * @param instance instace to check

      * @return true if instance of instance

      */

     public boolean isInstance(final ScriptObject instance) {

         return false;

     }

     /**

      * Flag this ScriptObject as non extensible

      *

      * @return the object after being made non extensible

      */

     public ScriptObject preventExtensions() {

         PropertyMap oldMap = getMap();

         while (true) {

             final PropertyMap newMap = getMap().preventExtensions();

             if (!compareAndSetMap(oldMap, newMap)) {

                 oldMap = getMap();

             } else {

                 return this;

             }

         }

     }

     /**

      * Check whether if an Object (not just a ScriptObject) represents JavaScript array

      *

      * @param obj object to check

      *

      * @return true if array

      */

     public static boolean isArray(final Object obj) {

         return (obj instanceof ScriptObject) && ((ScriptObject)obj).isArray();

     }

     /**

      * Check if this ScriptObject is an array

      * @return true if array

      */

     public final boolean isArray() {

         return (flags & IS_ARRAY) != 0;

     }

     /**

      * Flag this ScriptObject as being an array

      */

     public final void setIsArray() {

         flags |= IS_ARRAY;

     }

     /**

      * Check if this ScriptObject is an {@code arguments} vector

      * @return true if arguments vector

      */

     public final boolean isArguments() {

         return (flags & IS_ARGUMENTS) != 0;

     }

     /**

      * Flag this ScriptObject as being an {@code arguments} vector

      */

     public final void setIsArguments() {

         flags |= IS_ARGUMENTS;

     }

     /**

      * Get the {@link ArrayData} for this ScriptObject if it is an array

      * @return array data

      */

     public final ArrayData getArray() {

         return arrayData;

     }

     /**

      * Set the {@link ArrayData} for this ScriptObject if it is to be an array

      * @param arrayData the array data

      */

     public final void setArray(final ArrayData arrayData) {

         this.arrayData = arrayData;

     }

     /**

      * Check if this ScriptObject is extensible

      * @return true if extensible

      */

     public boolean isExtensible() {

         return getMap().isExtensible();

     }

     /**

      * ECMAScript 15.2.3.8 - seal implementation

      * @return the sealed ScriptObject

      */

     public ScriptObject seal() {

         PropertyMap oldMap = getMap();

         while (true) {

             final PropertyMap newMap = getMap().seal();

             if (!compareAndSetMap(oldMap, newMap)) {

                 oldMap = getMap();

             } else {

                 setArray(ArrayData.seal(getArray()));

                 return this;

             }

         }

     }

     /**

      * Check whether this ScriptObject is sealed

      * @return true if sealed

      */

     public boolean isSealed() {

         return getMap().isSealed();

     }

     /**

      * ECMA 15.2.39 - freeze implementation. Freeze this ScriptObject

      * @return the frozen ScriptObject

      */

     public ScriptObject freeze() {

         PropertyMap oldMap = getMap();

         while (true) {

             final PropertyMap newMap = getMap().freeze();

             if (!compareAndSetMap(oldMap, newMap)) {

                 oldMap = getMap();

             } else {

                 setArray(ArrayData.freeze(getArray()));

                 return this;

             }

         }

     }

     /**

      * Check whether this ScriptObject is frozen

      * @return true if frozed

      */

     public boolean isFrozen() {

         return getMap().isFrozen();

     }

     /**

      * Flag this ScriptObject as scope

      */

     public final void setIsScope() {

         if (Context.DEBUG) {

             scopeCount++;

         }

         flags |= IS_SCOPE;

     }

     /**

      * Check whether this ScriptObject is scope

      * @return true if scope

      */

     public final boolean isScope() {

         return (flags & IS_SCOPE) != 0;

     }

     /**

      * Clears the properties from a ScriptObject

      * (java.util.Map-like method to help ScriptObjectMirror implementation)

      */

     public void clear() {

         final boolean strict = getContext()._strict;

         final Iterator<String> iter = propertyIterator();

         while (iter.hasNext()) {

             delete(iter.next(), strict);

         }

     }

     /**

      * Checks if a property with a given key is present in a ScriptObject

      * (java.util.Map-like method to help ScriptObjectMirror implementation)

      *

      * @param key the key to check for

      * @return true if a property with the given key exists, false otherwise

      */

     public boolean containsKey(final Object key) {

         return has(key);

     }

     /**

      * Checks if a property with a given value is present in a ScriptObject

      * (java.util.Map-like method to help ScriptObjectMirror implementation)

      *

      * @param value value to check for

      * @return true if a property with the given value exists, false otherwise

      */

     public boolean containsValue(final Object value) {

         final Iterator<Object> iter = valueIterator();

         while (iter.hasNext()) {

             if (iter.next().equals(value)) {

                 return true;

             }

         }

         return false;

     }

     /**

      * Returns the set of {@literal <property, value>} entries that make up this

      * ScriptObject's properties

      * (java.util.Map-like method to help ScriptObjectMirror implementation)

      *

      * @return an entry set of all the properties in this object

      */

     public Set<Map.Entry<Object, Object>> entrySet() {

         final Iterator<String> iter = propertyIterator();

         final Set<Map.Entry<Object, Object>> entries = new HashSet<>();

         while (iter.hasNext()) {

             final Object key = iter.next();

             entries.add(new AbstractMap.SimpleImmutableEntry<>(key, get(key)));

         }

         return Collections.unmodifiableSet(entries);

     }

     /**

      * Check whether a ScriptObject contains no properties

      * (java.util.Map-like method to help ScriptObjectMirror implementation)

      *

      * @return true if object has no properties

      */

     public boolean isEmpty() {

         return !propertyIterator().hasNext();

     }

     /**

      * Return the set of keys (property names) for all properties

      * in this ScriptObject

      * (java.util.Map-like method to help ScriptObjectMirror implementation)

      *

      * @return keySet of this ScriptObject

      */

     public Set<Object> keySet() {

         final Iterator<String> iter = propertyIterator();

         final Set<Object> keySet = new HashSet<>();

         while (iter.hasNext()) {

             keySet.add(iter.next());

         }

         return Collections.unmodifiableSet(keySet);

     }

     /**

      * Put a property in the ScriptObject

      * (java.util.Map-like method to help ScriptObjectMirror implementation)

      *

      * @param key property key

      * @param value property value

      * @return oldValue if property with same key existed already

      */

     public Object put(final Object key, final Object value) {

         final Object oldValue = get(key);

         set(key, value, getContext()._strict);

         return oldValue;

     }

     /**

      * Put several properties in the ScriptObject given a mapping

      * of their keys to their values

      * (java.util.Map-like method to help ScriptObjectMirror implementation)

      *

      * @param otherMap a {@literal <key,value>} map of properties to add

      */

     public void putAll(final Map<?, ?> otherMap) {

         final boolean strict = getContext()._strict;

         for (final Map.Entry<?, ?> entry : otherMap.entrySet()) {

             set(entry.getKey(), entry.getValue(), strict);

         }

     }

     /**

      * Remove a property from the ScriptObject.

      * (java.util.Map-like method to help ScriptObjectMirror implementation)

      *

      * @param key the key of the property

      * @return the oldValue of the removed property

      */

     public Object remove(final Object key) {

         final Object oldValue = get(key);

         delete(key, getContext()._strict);

         return oldValue;

     }

     /**

      * Return the size of the ScriptObject - i.e. the number of properties

      * it contains

      * (java.util.Map-like method to help ScriptObjectMirror implementation)

      *

      * @return number of properties in ScriptObject

      */

     public int size() {

         int n = 0;

         for (final Iterator<String> iter = propertyIterator(); iter.hasNext(); iter.next()) {

             n++;

         }

         return n;

     }

     /**

      * Return the values of the properties in the ScriptObject

      * (java.util.Map-like method to help ScriptObjectMirror implementation)

      *

      * @return collection of values for the properties in this ScriptObject

      */

     public Collection<Object> values() {

         final List<Object>     values = new ArrayList<>(size());

         final Iterator<Object> iter   = valueIterator();

         while (iter.hasNext()) {

             values.add(iter.next());

         }

         return Collections.unmodifiableList(values);

     }

     /**

      * Lookup method that, given a CallSiteDescriptor, looks up the target

      * MethodHandle and creates a GuardedInvocation

      * with the appropriate guard(s).

      *

      * @param desc call site descriptor

      * @param request the link request

      *

      * @return GuardedInvocation for the callsite

      */

     public GuardedInvocation lookup(final CallSiteDescriptor desc, final LinkRequest request) {

         final int c = desc.getNameTokenCount();

         // JavaScript is "immune" to all currently defined Dynalink composite operation - getProp is the same as getElem

         // is the same as getMethod as JavaScript objects have a single namespace for all three. Therefore, we don't

         // care about them, and just link to whatever is the first operation.

         final String operator = CallSiteDescriptorFactory.tokenizeOperators(desc).get(0);

         // NOTE: we support getElem and setItem as JavaScript doesn't distinguish items from properties. Nashorn itself

         // emits "dyn:getProp:identifier" for "<expr>.<identifier>" and "dyn:getElem" for "<expr>[<expr>]", but we are

         // more flexible here and dispatch not on operation name (getProp vs. getElem), but rather on whether the

         // operation has an associated name or not.

         switch (operator) {

         case "getProp":

         case "getElem":

         case "getMethod":

             return c > 2 ? findGetMethod(desc, request, operator) : findGetIndexMethod(desc, request);

         case "setProp":

         case "setElem":

             return c > 2 ? findSetMethod(desc, request) : findSetIndexMethod(desc);

         case "call":

             return findCallMethod(desc, request);

         case "new":

             return findNewMethod(desc);

         case "callMethod":

             return findCallMethodMethod(desc, request);

         default:

             return null;

         }

     }

     /**

      * Find the appropriate New method for an invoke dynamic call.

      *

      * @param desc The invoke dynamic call site descriptor.

      *

      * @return GuardedInvocation to be invoked at call site.

      */

     protected GuardedInvocation findNewMethod(final CallSiteDescriptor desc) {

         return notAFunction();

     }

     /**

      * Find the appropriate CALL method for an invoke dynamic call.

      * This generates "not a function" always

      *

      * @param desc    the call site descriptor.

      * @param request the link request

      *

      * @return GuardedInvocation to be invoed at call site.

      */

     protected GuardedInvocation findCallMethod(final CallSiteDescriptor desc, final LinkRequest request) {

         return notAFunction();

     }

     private GuardedInvocation notAFunction() {

         throw typeError("not.a.function", ScriptRuntime.safeToString(this));

     }

     /**

      * Find an implementation for a "dyn:callMethod" operation. Note that Nashorn internally never uses

      * "dyn:callMethod", but instead always emits two call sites in bytecode, one for "dyn:getMethod", and then another

      * one for "dyn:call". Explicit support for "dyn:callMethod" is provided for the benefit of potential external

      * callers. The implementation itself actually folds a "dyn:getMethod" method handle into a "dyn:call" method handle.

      *

      * @param desc    the call site descriptor.

      * @param request the link request

      *

      * @return GuardedInvocation to be invoked at call site.

      */

     protected GuardedInvocation findCallMethodMethod(final CallSiteDescriptor desc, final LinkRequest request) {

         // R(P0, P1, ...)

         final MethodType callType = desc.getMethodType();

         // use type Object(P0) for the getter

         final CallSiteDescriptor getterType = desc.changeMethodType(MethodType.methodType(Object.class, callType.parameterType(0)));

         final GuardedInvocation getter = findGetMethod(getterType, request, "getMethod");

         // Object(P0) => Object(P0, P1, ...)

         final MethodHandle argDroppingGetter = MH.dropArguments(getter.getInvocation(), 1, callType.parameterList().subList(1, callType.parameterCount()));

         // R(Object, P0, P1, ...)

         final MethodHandle invoker = Bootstrap.createDynamicInvoker("dyn:call", callType.insertParameterTypes(0, argDroppingGetter.type().returnType()));

         // Fold Object(P0, P1, ...) into R(Object, P0, P1, ...) => R(P0, P1, ...)

         return getter.replaceMethods(MH.foldArguments(invoker, argDroppingGetter), getter.getGuard());

     }

     /**

      * Find the appropriate GET method for an invoke dynamic call.

      *

      * @param desc     the call site descriptor

      * @param request  the link request

      * @param operator operator for get: getProp, getMethod, getElem etc

      *

      * @return GuardedInvocation to be invoked at call site.

      */

     protected GuardedInvocation findGetMethod(final CallSiteDescriptor desc, final LinkRequest request, final String operator) {

         final String name = desc.getNameToken(CallSiteDescriptor.NAME_OPERAND);

         final FindProperty find = findProperty(name, true);

         MethodHandle methodHandle;

         if (find == null) {

             if ("getProp".equals(operator)) {

                 return noSuchProperty(desc, request);

             } else if ("getMethod".equals(operator)) {

                 return noSuchMethod(desc, request);

             } else if ("getElem".equals(operator)) {

                 return createEmptyGetter(desc, name);

             }

             throw new AssertionError(); // never invoked with any other operation

         }

         if (request.isCallSiteUnstable()) {

             return findMegaMorphicGetMethod(desc, name);

         }

         final Class<?> returnType = desc.getMethodType().returnType();

         final Property property = find.getProperty();

         methodHandle = find.getGetter(returnType);

         // getMap() is fine as we have the prototype switchpoint depending on where the property was found

         final MethodHandle guard = NashornGuards.getMapGuard(getMap());

         if (methodHandle != null) {

             assert methodHandle.type().returnType().equals(returnType);

             if (find.isSelf()) {

                 return new GuardedInvocation(methodHandle, ObjectClassGenerator.OBJECT_FIELDS_ONLY &&

                         NashornCallSiteDescriptor.isFastScope(desc) && !property.canChangeType() ? null : guard);

             }

             final ScriptObject prototype = find.getOwner();

             if (!property.hasGetterFunction()) {

                 methodHandle = bindTo(methodHandle, prototype);

             }

             return new GuardedInvocation(methodHandle, getMap().getProtoGetSwitchPoint(name), guard);

         }

         assert !NashornCallSiteDescriptor.isFastScope(desc);

         return new GuardedInvocation(Lookup.emptyGetter(returnType), getMap().getProtoGetSwitchPoint(name), guard);

     }

     private static GuardedInvocation findMegaMorphicGetMethod(final CallSiteDescriptor desc, final String name) {

         final MethodType mhType = desc.getMethodType().insertParameterTypes(1, Object.class);

         final GuardedInvocation inv = findGetIndexMethod(mhType);

         return inv.replaceMethods(MH.insertArguments(inv.getInvocation(), 1, name), inv.getGuard());

     }

     /**

      * Find the appropriate GETINDEX method for an invoke dynamic call.

      *

      * @param desc    the call site descriptor

      * @param request the link request

      *

      * @return GuardedInvocation to be invoked at call site.

      */

     protected GuardedInvocation findGetIndexMethod(final CallSiteDescriptor desc, final LinkRequest request) {

         return findGetIndexMethod(desc.getMethodType());

     }

     /**

      * Find the appropriate GETINDEX method for an invoke dynamic call.

      *

      * @param callType the call site method type

      * @return GuardedInvocation to be invoked at call site.

      */

     private static GuardedInvocation findGetIndexMethod(final MethodType callType) {

         final Class<?> returnClass = callType.returnType();

         final Class<?> keyClass    = callType.parameterType(1);

         String name = "get";

         if (returnClass.isPrimitive()) {

             //turn e.g. get with a double into getDouble

             final String returnTypeName = returnClass.getName();

             name += Character.toUpperCase(returnTypeName.charAt(0)) + returnTypeName.substring(1, returnTypeName.length());

         }

         return new GuardedInvocation(findOwnMH(name, returnClass, keyClass), getScriptObjectGuard(callType));

     }

     private static MethodHandle getScriptObjectGuard(final MethodType type) {

         return ScriptObject.class.isAssignableFrom(type.parameterType(0)) ? null : NashornGuards.getScriptObjectGuard();

     }

     /**

      * Find the appropriate SET method for an invoke dynamic call.

      *

      * @param desc    the call site descriptor

      * @param request the link request

      *

      * @return GuardedInvocation to be invoked at call site.

      */

     protected GuardedInvocation findSetMethod(final CallSiteDescriptor desc, final LinkRequest request) {

         final String name = desc.getNameToken(CallSiteDescriptor.NAME_OPERAND);

         if(request.isCallSiteUnstable()) {

             return findMegaMorphicSetMethod(desc, name);

         }

         final boolean scope = isScope();

         /*

          * If doing property set on a scope object, we should stop proto search on the first

          * non-scope object. Without this, for example, when assigning "toString" on global scope,

          * we'll end up assigning it on it's proto - which is Object.prototype.toString !!

          *

          * toString = function() { print("global toString"); } // don't affect Object.prototype.toString

          */

         FindProperty find = findProperty(name, true, scope, this);

         // If it's not a scope search, then we don't want any inherited properties except those with user defined accessors.

         if (!scope && find != null && find.isInherited() && !(find.getProperty() instanceof UserAccessorProperty)) {

             // We should still check if inherited data property is not writable

             if (isExtensible() && !find.getProperty().isWritable()) {

                 return createEmptySetMethod(desc, "property.not.writable", false);

             }

             // Otherwise, forget the found property

             find = null;

         }

         if (find != null) {

             if(!find.getProperty().isWritable()) {

                 // Existing, non-writable property

                 return createEmptySetMethod(desc, "property.not.writable", true);

             }

         } else if (!isExtensible()) {

             // Non-existing property on a non-extensible object

             return createEmptySetMethod(desc, "object.non.extensible", false);

         }

         return new SetMethodCreator(this, find, desc).createGuardedInvocation();

     }

     private GuardedInvocation createEmptySetMethod(final CallSiteDescriptor desc, String strictErrorMessage, boolean canBeFastScope) {

         final String name = desc.getNameToken(CallSiteDescriptor.NAME_OPERAND);

         if (NashornCallSiteDescriptor.isStrict(desc)) {

                throw typeError(strictErrorMessage, name, ScriptRuntime.safeToString((this)));

            }

            assert canBeFastScope || !NashornCallSiteDescriptor.isFastScope(desc);

            final PropertyMap myMap = getMap();

            return new GuardedInvocation(Lookup.EMPTY_SETTER, myMap.getProtoGetSwitchPoint(name), NashornGuards.getMapGuard(myMap));

     }

     @SuppressWarnings("unused")

     private static void setEmbed(final CallSiteDescriptor desc, final PropertyMap oldMap, final PropertyMap newMap, final MethodHandle setter, final int i, final Object self, final Object value) throws Throwable {

         final ScriptObject obj = (ScriptObject)self;

         if (obj.trySetEmbedOrSpill(desc, oldMap, newMap, value)) {

             obj.useEmbed(i);

             setter.invokeExact(self, value);

         }

     }

     @SuppressWarnings("unused")

     private static void setSpill(final CallSiteDescriptor desc, final PropertyMap oldMap, final PropertyMap newMap, final int index, final Object self, final Object value) {

         final ScriptObject obj = (ScriptObject)self;

         if (obj.trySetEmbedOrSpill(desc, oldMap, newMap, value)) {

             obj.spill[index] = value;

         }

     }

     private boolean trySetEmbedOrSpill(final CallSiteDescriptor desc, final PropertyMap oldMap, final PropertyMap newMap, final Object value) {

         final boolean isStrict = NashornCallSiteDescriptor.isStrict(desc);

         if (!isExtensible() && isStrict) {

             throw typeError("object.non.extensible", desc.getNameToken(2), ScriptRuntime.safeToString(this));

         } else if (compareAndSetMap(oldMap, newMap)) {

             return true;

         } else {

             set(desc.getNameToken(CallSiteDescriptor.NAME_OPERAND), value, isStrict);

             return false;

         }

     }

     @SuppressWarnings("unused")

     private static void setSpillWithNew(final CallSiteDescriptor desc, final PropertyMap oldMap, final PropertyMap newMap, final int index, final Object self, final Object value) {

         final ScriptObject obj      = (ScriptObject)self;

         final boolean      isStrict = NashornCallSiteDescriptor.isStrict(desc);

         if (!obj.isExtensible()) {

             if (isStrict) {

                 throw typeError("object.non.extensible", desc.getNameToken(2), ScriptRuntime.safeToString(obj));

             }

         } else if (obj.compareAndSetMap(oldMap, newMap)) {

             obj.spill = new Object[SPILL_RATE];

             obj.spill[index] = value;

         } else {

             obj.set(desc.getNameToken(2), value, isStrict);

         }

     }

     @SuppressWarnings("unused")

     private static void setSpillWithGrow(final CallSiteDescriptor desc, final PropertyMap oldMap, final PropertyMap newMap, final int index, final int newLength, final Object self, final Object value) {

         final ScriptObject obj      = (ScriptObject)self;

         final boolean      isStrict = NashornCallSiteDescriptor.isStrict(desc);

         if (!obj.isExtensible()) {

             if (isStrict) {

                 throw typeError("object.non.extensible", desc.getNameToken(2), ScriptRuntime.safeToString(obj));

             }

         } else if (obj.compareAndSetMap(oldMap, newMap)) {

             final int oldLength = obj.spill.length;

             final Object[] newSpill = new Object[newLength];

             System.arraycopy(obj.spill, 0, newSpill, 0, oldLength);

             obj.spill = newSpill;

             obj.spill[index] = value;

         } else {

             obj.set(desc.getNameToken(2), value, isStrict);

         }

     }

     private static GuardedInvocation findMegaMorphicSetMethod(final CallSiteDescriptor desc, final String name) {

         final MethodType type = desc.getMethodType().insertParameterTypes(1, Object.class);

         final GuardedInvocation inv = findSetIndexMethod(type, NashornCallSiteDescriptor.isStrict(desc));

         return inv.replaceMethods(MH.insertArguments(inv.getInvocation(), 1, name), inv.getGuard());

     }

     private static GuardedInvocation findSetIndexMethod(final CallSiteDescriptor desc) { // array, index, value

         return findSetIndexMethod(desc.getMethodType(), NashornCallSiteDescriptor.isStrict(desc));

     }

     /**

      * Find the appropriate SETINDEX method for an invoke dynamic call.

      *

      * @param callType the method type at the call site

      * @param isStrict are we in strict mode?

      *

      * @return GuardedInvocation to be invoked at call site.

      */

     private static GuardedInvocation findSetIndexMethod(final MethodType callType, final boolean isStrict) {

         assert callType.parameterCount() == 3;

         final Class<?>   keyClass   = callType.parameterType(1);

         final Class<?>   valueClass = callType.parameterType(2);

         MethodHandle methodHandle = findOwnMH("set", void.class, keyClass, valueClass, boolean.class);

         methodHandle = MH.insertArguments(methodHandle, 3, isStrict);

         return new GuardedInvocation(methodHandle, getScriptObjectGuard(callType));

     }

     /**

      * Fall back if a function property is not found.

      * @param desc The call site descriptor

      * @param request the link request

      * @return GuardedInvocation to be invoked at call site.

      */

     public GuardedInvocation noSuchMethod(final CallSiteDescriptor desc, final LinkRequest request) {

         final String       name      = desc.getNameToken(2);

         final FindProperty find      = findProperty(NO_SUCH_METHOD_NAME, true);

         final boolean      scopeCall = isScope() && NashornCallSiteDescriptor.isScope(desc);

         if (find == null) {

             return noSuchProperty(desc, request);

         }

         final ScriptFunction func = (ScriptFunction)getObjectValue(find);

         final Object thiz = scopeCall && func.isStrict() ? ScriptRuntime.UNDEFINED : this;

         // TODO: It'd be awesome if we could bind "name" without binding "this".

         return new GuardedInvocation(MH.dropArguments(MH.constant(ScriptFunction.class,

                 func.makeBoundFunction(thiz, new Object[] { name })), 0, Object.class),

                 null, NashornGuards.getMapGuard(getMap()));

     }

     /**

      * Fall back if a property is not found.

      * @param desc the call site descriptor.

      * @param request the link request

      * @return GuardedInvocation to be invoked at call site.

      */

     public GuardedInvocation noSuchProperty(final CallSiteDescriptor desc, final LinkRequest request) {

         final String name = desc.getNameToken(CallSiteDescriptor.NAME_OPERAND);

         final FindProperty find = findProperty(NO_SUCH_PROPERTY_NAME, true);

         final boolean scopeAccess = isScope() && NashornCallSiteDescriptor.isScope(desc);

         if (find != null) {

             final ScriptFunction func = (ScriptFunction)getObjectValue(find);

             MethodHandle methodHandle = getCallMethodHandle(func, desc.getMethodType(), name);

             if (methodHandle != null) {

                 if (scopeAccess && func.isStrict()) {

                     methodHandle = bindTo(methodHandle, UNDEFINED);

                 }

                 return new GuardedInvocation(methodHandle,

                         find.isInherited()? getMap().getProtoGetSwitchPoint(NO_SUCH_PROPERTY_NAME) : null,

                         getKnownFunctionPropertyGuard(getMap(), find.getGetter(Object.class), find.getOwner(), func));

             }

         }

         if (scopeAccess) {

             throw referenceError("not.defined", name);

         }

         return createEmptyGetter(desc, name);

     }

     /**

      * Invoke fall back if a property is not found.

      * @param name Name of property.

      * @return Result from call.

      */

     private Object invokeNoSuchProperty(final String name) {

         final FindProperty find = findProperty(NO_SUCH_PROPERTY_NAME, true);

         if (find != null) {

             final Object func = getObjectValue(find);

             if (func instanceof ScriptFunction) {

                 return ScriptRuntime.apply((ScriptFunction)func, this, name);

             }

         }

         return UNDEFINED;

     }

     private GuardedInvocation createEmptyGetter(final CallSiteDescriptor desc, final String name) {

         return new GuardedInvocation(Lookup.emptyGetter(desc.getMethodType().returnType()), getMap().getProtoGetSwitchPoint(name), NashornGuards.getMapGuard(getMap()));

     }

     private abstract static class ScriptObjectIterator <T extends Object> implements Iterator<T> {

         protected T[] values;

         protected final ScriptObject object;

         private int index;

         ScriptObjectIterator(final ScriptObject object) {

             this.object = object;

         }

         protected abstract void init();

         @Override

         public boolean hasNext() {

             if (values == null) {

                 init();

             }

             return index < values.length;

         }

         @Override

         public T next() {

             if (values == null) {

                 init();

             }

             return values[index++];

         }

         @Override

         public void remove() {

             throw new UnsupportedOperationException();

         }

     }

     private static class KeyIterator extends ScriptObjectIterator<String> {

         KeyIterator(final ScriptObject object) {

             super(object);

         }

         @Override

         protected void init() {

             final Set<String> keys = new LinkedHashSet<>();

             for (ScriptObject self = object; self != null; self = self.getProto()) {

                 keys.addAll(Arrays.asList(self.getOwnKeys(false)));

             }

             this.values = keys.toArray(new String[keys.size()]);

         }

     }

     private static class ValueIterator extends ScriptObjectIterator<Object> {

         ValueIterator(final ScriptObject object) {

             super(object);

         }

         @Override

         protected void init() {

             final ArrayList<Object> valueList = new ArrayList<>();

             for (ScriptObject self = object; self != null; self = self.getProto()) {

                 for (final String key : self.getOwnKeys(false)) {

                     valueList.add(self.get(key));

                 }

             }

             this.values = valueList.toArray(new Object[valueList.size()]);

         }

     }

     /**

      * Add a spill property for the given key.

      * @param key           Property key.

      * @param propertyFlags Property flags.

      * @return Added property.

      */

     private Property addSpillProperty(final String key, final int propertyFlags) {

         int i = findEmbed();

         Property spillProperty;

         if (i >= EMBED_SIZE) {

             i = getMap().getSpillLength();

             MethodHandle getter = MH.arrayElementGetter(Object[].class);

             MethodHandle setter = MH.arrayElementSetter(Object[].class);

             getter = MH.asType(MH.insertArguments(getter, 1, i), Lookup.GET_OBJECT_TYPE);

             setter = MH.asType(MH.insertArguments(setter, 1, i), Lookup.SET_OBJECT_TYPE);

             spillProperty = new SpillProperty(key, propertyFlags | Property.IS_SPILL, i, getter, setter);

             notifyPropertyAdded(this, spillProperty);

             spillProperty = addOwnProperty(spillProperty);

             i = spillProperty.getSlot();

             final int newLength = (i + SPILL_RATE) / SPILL_RATE * SPILL_RATE;

             final Object[] newSpill = new Object[newLength];

             if (spill != null) {

                 System.arraycopy(spill, 0, newSpill, 0, spill.length);

             }

             spill = newSpill;

          } else {

             useEmbed(i);

             spillProperty = new SpillProperty(key, propertyFlags, i, GET_EMBED[i], SET_EMBED[i]);

             notifyPropertyAdded(this, spillProperty);

             spillProperty = addOwnProperty(spillProperty);

         }

         return spillProperty;

     }

     /**

      * Add a spill entry for the given key.

      * @param key           Property key.

      * @param propertyFlags Property flags.

      * @return Setter method handle.

      */

     private MethodHandle addSpill(final String key, final int propertyFlags) {

         final Property spillProperty = addSpillProperty(key, propertyFlags);

         final Class<?> type = Object.class;

         return spillProperty.getSetter(type, getMap()); //TODO specfields

     }

     MethodHandle addSpill(final String key) {

         return addSpill(key, 0);

     }

     /**

      * Make sure arguments are paired correctly, with respect to more parameters than declared,

      * fewer parameters than declared and other things that JavaScript allows. This might involve

      * creating collectors.

      *

      * @param methodHandle method handle for invoke

      * @param callType     type of the call

      *

      * @return method handle with adjusted arguments

      */

     protected static MethodHandle pairArguments(final MethodHandle methodHandle, final MethodType callType) {

         return pairArguments(methodHandle, callType, null);

     }

     /**

      * Make sure arguments are paired correctly, with respect to more parameters than declared,

      * fewer parameters than declared and other things that JavaScript allows. This might involve

      * creating collectors.

      *

      * Make sure arguments are paired correctly.

      * @param methodHandle MethodHandle to adjust.

      * @param callType     MethodType of the call site.

      * @param callerVarArg true if the caller is vararg, false otherwise, null if it should be inferred from the

      * {@code callType}; basically, if the last parameter type of the call site is an array, it'll be considered a

      * variable arity call site. These are ordinarily rare; Nashorn code generator creates variable arity call sites

      * when the call has more than {@link LinkerCallSite#ARGLIMIT} parameters.

      *

      * @return method handle with adjusted arguments

      */

     public static MethodHandle pairArguments(final MethodHandle methodHandle, final MethodType callType, final Boolean callerVarArg) {

         final MethodType methodType = methodHandle.type();

         if (methodType.equals(callType)) {

             return methodHandle;

         }

         final int parameterCount = methodType.parameterCount();

         final int callCount      = callType.parameterCount();

         final boolean isCalleeVarArg = parameterCount > 0 && methodType.parameterType(parameterCount - 1).isArray();

         final boolean isCallerVarArg = callerVarArg != null ? callerVarArg.booleanValue() : (callCount > 0 &&

                 callType.parameterType(callCount - 1).isArray());

         if (callCount < parameterCount) {

             final int      missingArgs = parameterCount - callCount;

             final Object[] fillers     = new Object[missingArgs];

             Arrays.fill(fillers, UNDEFINED);

             if (isCalleeVarArg) {

                 fillers[missingArgs - 1] = new Object[0];

             }

             return MH.insertArguments(

                 methodHandle,

                 parameterCount - missingArgs,

                 fillers);

         }

         if (isCalleeVarArg) {

             return isCallerVarArg ?

                 methodHandle :

                 MH.asCollector(methodHandle, Object[].class, callCount - parameterCount + 1);

         }

         if (isCallerVarArg) {

             final int spreadArgs = parameterCount - callCount + 1;

             return MH.filterArguments(

                 MH.asSpreader(

                     methodHandle,

                     Object[].class,

                     spreadArgs),

                 callCount - 1,

                 MH.insertArguments(

                     TRUNCATINGFILTER,

                     0,

                     spreadArgs)

                 );

         }

         if (callCount > parameterCount) {

             final int discardedArgs = callCount - parameterCount;

             final Class<?>[] discards = new Class<?>[discardedArgs];

             Arrays.fill(discards, Object.class);

             return MH.dropArguments(methodHandle, callCount - discardedArgs, discards);

         }

         return methodHandle;

     }

     @SuppressWarnings("unused")

     private static Object[] truncatingFilter(final int n, final Object[] array) {

         final int length = array == null ? 0 : array.length;

         if (n == length) {

             return array == null ? new Object[0] : array;

         }

         final Object[] newArray = new Object[n];

         if (array != null) {

             for (int i = 0; i < n && i < length; i++) {

                 newArray[i] = array[i];

             }

         }

         if (length < n) {

             final Object fill = UNDEFINED;

             for (int i = length; i < n; i++) {

                 newArray[i] = fill;

             }

         }

         return newArray;

     }

     /**

       * Numeric length setter for length property

       *

       * @param newLength new length to set

       */

     public final void setLength(final long newLength) {

        final long arrayLength = getArray().length();

        if (newLength == arrayLength) {

            return;

        }

        final boolean isStrict = getContext()._strict;

        if (newLength > arrayLength) {

            setArray(getArray().ensure(newLength - 1));

             if (getArray().canDelete(arrayLength, (newLength - 1), isStrict)) {

                setArray(getArray().delete(arrayLength, (newLength - 1)));

            }

            return;

        }

        if (newLength < arrayLength) {

            setArray(getArray().shrink(newLength));

            getArray().setLength(newLength);

        }

     }

     private int getInt(final int index, final String key) {

         for (ScriptObject object = this; object != null; object = object.getProto()) {

             final ArrayData array = object.getArray();

             if (array.has(index)) {

                 return array.getInt(index);

             }

             final FindProperty find = object.findProperty(key, false);

             if (find != null) {

                 return getIntValue(new FindProperty(this, find.getOwner(), find.getProperty()));

             }

         }

         return JSType.toInt32(invokeNoSuchProperty(key));

     }

     @Override

     public int getInt(final Object key) {

         return getInt(getArrayIndexNoThrow(key), convertKey(key));

     }

     @Override

     public int getInt(final double key) {

         return getInt(getArrayIndexNoThrow(key), convertKey(key));

     }

     @Override

     public int getInt(final long key) {

         return getInt(getArrayIndexNoThrow(key), convertKey(key));

     }

     @Override

     public int getInt(final int key) {

         return getInt(getArrayIndexNoThrow(key), convertKey(key));

     }

     private long getLong(final int index, final String key) {

         for (ScriptObject object = this; object != null; object = object.getProto()) {

             final ArrayData array = object.getArray();

             if (array.has(index)) {

                 return array.getLong(index);

             }

             final FindProperty find = object.findProperty(key, false);

             if (find != null) {

                 return getLongValue(new FindProperty(this, find.getOwner(), find.getProperty()));

             }

         }

         return JSType.toLong(invokeNoSuchProperty(key));

     }

     @Override

     public long getLong(final Object key) {

         return getLong(getArrayIndexNoThrow(key), convertKey(key));

     }

     @Override

     public long getLong(final double key) {

         return getLong(getArrayIndexNoThrow(key), convertKey(key));

     }

     @Override

     public long getLong(final long key) {

         return getLong(getArrayIndexNoThrow(key), convertKey(key));

     }

     @Override

     public long getLong(final int key) {

         return getLong(getArrayIndexNoThrow(key), convertKey(key));

     }

     private double getDouble(final int index, final String key) {

         for (ScriptObject object = this; object != null; object = object.getProto()) {

             final ArrayData array = object.getArray();

             if (array.has(index)) {

                 return array.getDouble(index);

             }

             final FindProperty find = object.findProperty(key, false);

             if (find != null) {

                 return getDoubleValue(new FindProperty(this, find.getOwner(), find.getProperty()));

             }

         }

         return JSType.toNumber(invokeNoSuchProperty(key));

     }

     @Override

     public double getDouble(final Object key) {

         return getDouble(getArrayIndexNoThrow(key), convertKey(key));

     }

     @Override

     public double getDouble(final double key) {

         return getDouble(getArrayIndexNoThrow(key), convertKey(key));

     }

     @Override

     public double getDouble(final long key) {

         return getDouble(getArrayIndexNoThrow(key), convertKey(key));

     }

     @Override

     public double getDouble(final int key) {

         return getDouble(getArrayIndexNoThrow(key), convertKey(key));

     }

     private Object get(final int index, final String key) {

         for (ScriptObject object = this; object != null; object = object.getProto()) {

             final ArrayData array = object.getArray();

             if (array.has(index)) {

                 return array.getObject(index);

             }

             final FindProperty find = object.findProperty(key, false);

             if (find != null) {

                 return getObjectValue(new FindProperty(this, find.getOwner(), find.getProperty()));

             }

         }

         return invokeNoSuchProperty(key);

     }

     @Override

     public Object get(final Object key) {

         return get(getArrayIndexNoThrow(key), convertKey(key));

     }

     @Override

     public Object get(final double key) {

         return get(getArrayIndexNoThrow(key), convertKey(key));

     }

     @Override

     public Object get(final long key) {

         return get(getArrayIndexNoThrow(key), convertKey(key));

     }

     @Override

     public Object get(final int key) {

         return get(getArrayIndexNoThrow(key), convertKey(key));

     }

     /**

      * Handle when an array doesn't have a slot - possibly grow and/or convert array.

      *

      * @param index  key as index

      * @param value  element value

      * @param strict are we in strict mode

      */

     private void doesNotHave(final int index, final Object value, final boolean strict) {

         final long oldLength = getArray().length();

         final long longIndex = index & JSType.MAX_UINT;

         if (!getArray().has(index)) {

             final String key = convertKey(longIndex);

             final FindProperty find = findProperty(key, true);

             if (find != null) {

                 setObject(find, strict, key, value);

                 return;

             }

         }

         if (longIndex >= oldLength) {

             if (!isExtensible()) {

                 if (strict) {

                     throw typeError("object.non.extensible", JSType.toString(index), ScriptRuntime.safeToString(this));

                 }

                 return;

             }

             setArray(getArray().ensure(longIndex));

         }

         if (value instanceof Integer) {

             setArray(getArray().set(index, (int)value, strict));

         } else if (value instanceof Long) {

             setArray(getArray().set(index, (long)value, strict));

         } else if (value instanceof Double) {

             setArray(getArray().set(index, (double)value, strict));

         } else {

             setArray(getArray().set(index, value, strict));

         }

         if (longIndex > oldLength) {

             ArrayData array = getArray();

             if (array.canDelete(oldLength, (longIndex - 1), strict)) {

                 array = array.delete(oldLength, (longIndex - 1));

             }

             setArray(array);

         }

     }

     /**

      * This is the most generic of all Object setters. Most of the others use this in some form.

      * TODO: should be further specialized

      *

      * @param find    found property

      * @param strict  are we in strict mode

      * @param key     property key

      * @param value   property value

      */

     public final void setObject(final FindProperty find, final boolean strict, final String key, final Object value) {

         FindProperty f = find;

         if (f != null && f.isInherited() && !(f.getProperty() instanceof UserAccessorProperty)) {

             f = null;

         }

         if (f != null) {

             if (!f.getProperty().isWritable()) {

                 if (strict) {

                     throw typeError("property.not.writable", key, ScriptRuntime.safeToString(this));

                 }

                 return;

             }

             try {

                 final MethodHandle setter = f.getSetter(Object.class, strict); //TODO specfields

                 setter.invokeExact((Object)f.getSetterReceiver(), value);

             } catch (final Error|RuntimeException e) {

                 throw e;

             } catch (final Throwable e) {

                 throw new RuntimeException(e);

             }

         } else if (!isExtensible()) {

             if (strict) {

                 throw typeError("object.non.extensible", key, ScriptRuntime.safeToString(this));

             }

         } else {

             spill(key, value);

         }

     }

     private void spill(final String key, final Object value) {

         try {

             addSpill(key).invokeExact((Object)this, value);

         } catch (final Error|RuntimeException e) {

             throw e;

         } catch (final Throwable e) {

             throw new RuntimeException(e);

         }

     }

     @Override

     public void set(final Object key, final int value, final boolean strict) {

         final int index = getArrayIndexNoThrow(key);

         if (isValidArrayIndex(index)) {

             if (getArray().has(index)) {

                 setArray(getArray().set(index, value, strict));

             } else {

                 doesNotHave(index, value, strict);

             }

             return;

         }

         set(key, JSType.toObject(value), strict);

     }

     @Override

     public void set(final Object key, final long value, final boolean strict) {

         final int index = getArrayIndexNoThrow(key);

         if (isValidArrayIndex(index)) {

             if (getArray().has(index)) {

                 setArray(getArray().set(index, value, strict));

             } else {

                 doesNotHave(index, value, strict);

             }

             return;

         }

         set(key, JSType.toObject(value), strict);

     }

     @Override

     public void set(final Object key, final double value, final boolean strict) {

         final int index = getArrayIndexNoThrow(key);

         if (isValidArrayIndex(index)) {

             if (getArray().has(index)) {

                 setArray(getArray().set(index, value, strict));

             } else {

                 doesNotHave(index, value, strict);

             }

             return;

         }

         set(key, JSType.toObject(value), strict);

     }

     @Override

     public void set(final Object key, final Object value, final boolean strict) {

         final int index = getArrayIndexNoThrow(key);

         if (isValidArrayIndex(index)) {

             if (getArray().has(index)) {

                 setArray(getArray().set(index, value, strict));

             } else {

                 doesNotHave(index, value, strict);

             }

             return;

         }

         final String       propName = convertKey(key);

         final FindProperty find     = findProperty(propName, true);

         setObject(find, strict, propName, value);

     }

     @Override

     public void set(final double key, final int value, final boolean strict) {

         final int index = getArrayIndexNoThrow(key);

         if (isValidArrayIndex(index)) {

             if (getArray().has(index)) {

                 setArray(getArray().set(index, value, strict));

             } else {

                 doesNotHave(index, value, strict);

             }

             return;

         }

         set(JSType.toObject(key), JSType.toObject(value), strict);

     }

     @Override

     public void set(final double key, final long value, final boolean strict) {

         final int index = getArrayIndexNoThrow(key);

         if (isValidArrayIndex(index)) {

             if (getArray().has(index)) {

                 setArray(getArray().set(index, value, strict));

             } else {

                 doesNotHave(index, value, strict);

             }

             return;

         }

         set(JSType.toObject(key), JSType.toObject(value), strict);

     }

     @Override

     public void set(final double key, final double value, final boolean strict) {

         final int index = getArrayIndexNoThrow(key);

         if (isValidArrayIndex(index)) {

             if (getArray().has(index)) {

                 setArray(getArray().set(index, value, strict));

             } else {

                 doesNotHave(index, value, strict);

             }

             return;

         }

         set(JSType.toObject(key), JSType.toObject(value), strict);

     }