runtime/ObjectConstructor.cpp

   1 /*
   2  *  Copyright (C) 1999-2000 Harri Porten (porten@kde.org)
   3  *  Copyright (C) 2008 Apple Inc. All rights reserved.
   4  *
   5  *  This library is free software; you can redistribute it and/or
   6  *  modify it under the terms of the GNU Lesser General Public
   7  *  License as published by the Free Software Foundation; either
   8  *  version 2 of the License, or (at your option) any later version.
   9  *
  10  *  This library is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  *  Lesser General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU Lesser General Public
  16  *  License along with this library; if not, write to the Free Software
  17  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  18  *
  19  */
  20
  21 #include "config.h"
  22 #include "ObjectConstructor.h"
  23
  24 #include "Error.h"
  25 #include "ExceptionHelpers.h"
  26 #include "JSFunction.h"
  27 #include "JSArray.h"
  28 #include "JSGlobalObject.h"
  29 #include "Lookup.h"
  30 #include "ObjectPrototype.h"
  31 #include "PropertyDescriptor.h"
  32 #include "PropertyNameArray.h"
  33
  34 namespace JSC {
  35
  36 ASSERT_CLASS_FITS_IN_CELL(ObjectConstructor);
  37
  38 static EncodedJSValue JSC_HOST_CALL objectConstructorGetPrototypeOf(ExecState*);
  39 static EncodedJSValue JSC_HOST_CALL objectConstructorGetOwnPropertyDescriptor(ExecState*);
  40 static EncodedJSValue JSC_HOST_CALL objectConstructorGetOwnPropertyNames(ExecState*);
  41 static EncodedJSValue JSC_HOST_CALL objectConstructorKeys(ExecState*);
  42 static EncodedJSValue JSC_HOST_CALL objectConstructorDefineProperty(ExecState*);
  43 static EncodedJSValue JSC_HOST_CALL objectConstructorDefineProperties(ExecState*);
  44 static EncodedJSValue JSC_HOST_CALL objectConstructorCreate(ExecState*);
  45 static EncodedJSValue JSC_HOST_CALL objectConstructorSeal(ExecState*);
  46 static EncodedJSValue JSC_HOST_CALL objectConstructorFreeze(ExecState*);
  47 static EncodedJSValue JSC_HOST_CALL objectConstructorPreventExtensions(ExecState*);
  48 static EncodedJSValue JSC_HOST_CALL objectConstructorIsSealed(ExecState*);
  49 static EncodedJSValue JSC_HOST_CALL objectConstructorIsFrozen(ExecState*);
  50 static EncodedJSValue JSC_HOST_CALL objectConstructorIsExtensible(ExecState*);
  51
  52 }
  53
  54 #include "ObjectConstructor.lut.h"
  55
  56 namespace JSC {
  57
  58 ASSERT_HAS_TRIVIAL_DESTRUCTOR(ObjectConstructor);
  59
  60 const ClassInfo ObjectConstructor::s_info = { "Function", &InternalFunction::s_info, 0, ExecState::objectConstructorTable, CREATE_METHOD_TABLE(ObjectConstructor) };
  61
  62 /* Source for ObjectConstructor.lut.h
  63 @begin objectConstructorTable
  64   getPrototypeOf            objectConstructorGetPrototypeOf             DontEnum|Function 1
  65   getOwnPropertyDescriptor  objectConstructorGetOwnPropertyDescriptor   DontEnum|Function 2
  66   getOwnPropertyNames       objectConstructorGetOwnPropertyNames        DontEnum|Function 1
  67   keys                      objectConstructorKeys                       DontEnum|Function 1
  68   defineProperty            objectConstructorDefineProperty             DontEnum|Function 3
  69   defineProperties          objectConstructorDefineProperties           DontEnum|Function 2
  70   create                    objectConstructorCreate                     DontEnum|Function 2
  71   seal                      objectConstructorSeal                       DontEnum|Function 1
  72   freeze                    objectConstructorFreeze                     DontEnum|Function 1
  73   preventExtensions         objectConstructorPreventExtensions          DontEnum|Function 1
  74   isSealed                  objectConstructorIsSealed                   DontEnum|Function 1
  75   isFrozen                  objectConstructorIsFrozen                   DontEnum|Function 1
  76   isExtensible              objectConstructorIsExtensible               DontEnum|Function 1
  77 @end
  78 */
  79
  80 ObjectConstructor::ObjectConstructor(JSGlobalObject* globalObject, Structure* structure)
  81     : InternalFunction(globalObject, structure)
  82 {
  83 }
  84
  85 void ObjectConstructor::finishCreation(ExecState* exec, ObjectPrototype* objectPrototype)
  86 {
  87     Base::finishCreation(exec->globalData(), Identifier(exec, "Object"));
  88     // ECMA 15.2.3.1
  89     putDirectWithoutTransition(exec->globalData(), exec->propertyNames().prototype, objectPrototype, DontEnum | DontDelete | ReadOnly);
  90     // no. of arguments for constructor
  91     putDirectWithoutTransition(exec->globalData(), exec->propertyNames().length, jsNumber(1), ReadOnly | DontEnum | DontDelete);
  92 }
  93
  94 bool ObjectConstructor::getOwnPropertySlot(JSCell* cell, ExecState* exec, const Identifier& propertyName, PropertySlot &slot)
  95 {
  96     return getStaticFunctionSlot<JSObject>(exec, ExecState::objectConstructorTable(exec), jsCast<ObjectConstructor*>(cell), propertyName, slot);
  97 }
  98
  99 bool ObjectConstructor::getOwnPropertyDescriptor(JSObject* object, ExecState* exec, const Identifier& propertyName, PropertyDescriptor& descriptor)
 100 {
 101     return getStaticFunctionDescriptor<JSObject>(exec, ExecState::objectConstructorTable(exec), jsCast<ObjectConstructor*>(object), propertyName, descriptor);
 102 }
 103
 104 // ECMA 15.2.2
 105 static ALWAYS_INLINE JSObject* constructObject(ExecState* exec, JSGlobalObject* globalObject, const ArgList& args)
 106 {
 107     JSValue arg = args.at(0);
 108     if (arg.isUndefinedOrNull())
 109         return constructEmptyObject(exec, globalObject);
 110     return arg.toObject(exec, globalObject);
 111 }
 112
 113 static EncodedJSValue JSC_HOST_CALL constructWithObjectConstructor(ExecState* exec)
 114 {
 115     ArgList args(exec);
 116     return JSValue::encode(constructObject(exec, asInternalFunction(exec->callee())->globalObject(), args));
 117 }
 118
 119 ConstructType ObjectConstructor::getConstructData(JSCell*, ConstructData& constructData)
 120 {
 121     constructData.native.function = constructWithObjectConstructor;
 122     return ConstructTypeHost;
 123 }
 124
 125 static EncodedJSValue JSC_HOST_CALL callObjectConstructor(ExecState* exec)
 126 {
 127     ArgList args(exec);
 128     return JSValue::encode(constructObject(exec, asInternalFunction(exec->callee())->globalObject(), args));
 129 }
 130
 131 CallType ObjectConstructor::getCallData(JSCell*, CallData& callData)
 132 {
 133     callData.native.function = callObjectConstructor;
 134     return CallTypeHost;
 135 }
 136
 137 EncodedJSValue JSC_HOST_CALL objectConstructorGetPrototypeOf(ExecState* exec)
 138 {
 139     if (!exec->argument(0).isObject())
 140         return throwVMError(exec, createTypeError(exec, "Requested prototype of a value that is not an object."));
 141     JSObject* object = asObject(exec->argument(0));
 142     if (!object->allowsAccessFrom(exec->trueCallerFrame()))
 143         return JSValue::encode(jsUndefined());
 144     return JSValue::encode(object->prototype());
 145 }
 146
 147 EncodedJSValue JSC_HOST_CALL objectConstructorGetOwnPropertyDescriptor(ExecState* exec)
 148 {
 149     if (!exec->argument(0).isObject())
 150         return throwVMError(exec, createTypeError(exec, "Requested property descriptor of a value that is not an object."));
 151     UString propertyName = exec->argument(1).toString(exec)->value(exec);
 152     if (exec->hadException())
 153         return JSValue::encode(jsNull());
 154     JSObject* object = asObject(exec->argument(0));
 155     PropertyDescriptor descriptor;
 156     if (!object->methodTable()->getOwnPropertyDescriptor(object, exec, Identifier(exec, propertyName), descriptor))
 157         return JSValue::encode(jsUndefined());
 158     if (exec->hadException())
 159         return JSValue::encode(jsUndefined());
 160
 161     JSObject* description = constructEmptyObject(exec);
 162     if (!descriptor.isAccessorDescriptor()) {
 163         description->putDirect(exec->globalData(), exec->propertyNames().value, descriptor.value() ? descriptor.value() : jsUndefined(), 0);
 164         description->putDirect(exec->globalData(), exec->propertyNames().writable, jsBoolean(descriptor.writable()), 0);
 165     } else {
 166         ASSERT(descriptor.getter());
 167         ASSERT(descriptor.setter());
 168         description->putDirect(exec->globalData(), exec->propertyNames().get, descriptor.getter(), 0);
 169         description->putDirect(exec->globalData(), exec->propertyNames().set, descriptor.setter(), 0);
 170     }
 171
 172     description->putDirect(exec->globalData(), exec->propertyNames().enumerable, jsBoolean(descriptor.enumerable()), 0);
 173     description->putDirect(exec->globalData(), exec->propertyNames().configurable, jsBoolean(descriptor.configurable()), 0);
 174
 175     return JSValue::encode(description);
 176 }
 177
 178 // FIXME: Use the enumeration cache.
 179 EncodedJSValue JSC_HOST_CALL objectConstructorGetOwnPropertyNames(ExecState* exec)
 180 {
 181     if (!exec->argument(0).isObject())
 182         return throwVMError(exec, createTypeError(exec, "Requested property names of a value that is not an object."));
 183     PropertyNameArray properties(exec);
 184     asObject(exec->argument(0))->methodTable()->getOwnPropertyNames(asObject(exec->argument(0)), exec, properties, IncludeDontEnumProperties);
 185     JSArray* names = constructEmptyArray(exec);
 186     size_t numProperties = properties.size();
 187     for (size_t i = 0; i < numProperties; i++)
 188         names->push(exec, jsOwnedString(exec, properties[i].ustring()));
 189     return JSValue::encode(names);
 190 }
 191
 192 // FIXME: Use the enumeration cache.
 193 EncodedJSValue JSC_HOST_CALL objectConstructorKeys(ExecState* exec)
 194 {
 195     if (!exec->argument(0).isObject())
 196         return throwVMError(exec, createTypeError(exec, "Requested keys of a value that is not an object."));
 197     PropertyNameArray properties(exec);
 198     asObject(exec->argument(0))->methodTable()->getOwnPropertyNames(asObject(exec->argument(0)), exec, properties, ExcludeDontEnumProperties);
 199     JSArray* keys = constructEmptyArray(exec);
 200     size_t numProperties = properties.size();
 201     for (size_t i = 0; i < numProperties; i++)
 202         keys->push(exec, jsOwnedString(exec, properties[i].ustring()));
 203     return JSValue::encode(keys);
 204 }
 205
 206 // ES5 8.10.5 ToPropertyDescriptor
 207 static bool toPropertyDescriptor(ExecState* exec, JSValue in, PropertyDescriptor& desc)
 208 {
 209     if (!in.isObject()) {
 210         throwError(exec, createTypeError(exec, "Property description must be an object."));
 211         return false;
 212     }
 213     JSObject* description = asObject(in);
 214
 215     PropertySlot enumerableSlot(description);
 216     if (description->getPropertySlot(exec, exec->propertyNames().enumerable, enumerableSlot)) {
 217         desc.setEnumerable(enumerableSlot.getValue(exec, exec->propertyNames().enumerable).toBoolean(exec));
 218         if (exec->hadException())
 219             return false;
 220     }
 221
 222     PropertySlot configurableSlot(description);
 223     if (description->getPropertySlot(exec, exec->propertyNames().configurable, configurableSlot)) {
 224         desc.setConfigurable(configurableSlot.getValue(exec, exec->propertyNames().configurable).toBoolean(exec));
 225         if (exec->hadException())
 226             return false;
 227     }
 228
 229     JSValue value;
 230     PropertySlot valueSlot(description);
 231     if (description->getPropertySlot(exec, exec->propertyNames().value, valueSlot)) {
 232         desc.setValue(valueSlot.getValue(exec, exec->propertyNames().value));
 233         if (exec->hadException())
 234             return false;
 235     }
 236
 237     PropertySlot writableSlot(description);
 238     if (description->getPropertySlot(exec, exec->propertyNames().writable, writableSlot)) {
 239         desc.setWritable(writableSlot.getValue(exec, exec->propertyNames().writable).toBoolean(exec));
 240         if (exec->hadException())
 241             return false;
 242     }
 243
 244     PropertySlot getSlot(description);
 245     if (description->getPropertySlot(exec, exec->propertyNames().get, getSlot)) {
 246         JSValue get = getSlot.getValue(exec, exec->propertyNames().get);
 247         if (exec->hadException())
 248             return false;
 249         if (!get.isUndefined()) {
 250             CallData callData;
 251             if (getCallData(get, callData) == CallTypeNone) {
 252                 throwError(exec, createTypeError(exec, "Getter must be a function."));
 253                 return false;
 254             }
 255         }
 256         desc.setGetter(get);
 257     }
 258
 259     PropertySlot setSlot(description);
 260     if (description->getPropertySlot(exec, exec->propertyNames().set, setSlot)) {
 261         JSValue set = setSlot.getValue(exec, exec->propertyNames().set);
 262         if (exec->hadException())
 263             return false;
 264         if (!set.isUndefined()) {
 265             CallData callData;
 266             if (getCallData(set, callData) == CallTypeNone) {
 267                 throwError(exec, createTypeError(exec, "Setter must be a function."));
 268                 return false;
 269             }
 270         }
 271         desc.setSetter(set);
 272     }
 273
 274     if (!desc.isAccessorDescriptor())
 275         return true;
 276
 277     if (desc.value()) {
 278         throwError(exec, createTypeError(exec, "Invalid property.  'value' present on property with getter or setter."));
 279         return false;
 280     }
 281
 282     if (desc.writablePresent()) {
 283         throwError(exec, createTypeError(exec, "Invalid property.  'writable' present on property with getter or setter."));
 284         return false;
 285     }
 286     return true;
 287 }
 288
 289 EncodedJSValue JSC_HOST_CALL objectConstructorDefineProperty(ExecState* exec)
 290 {
 291     if (!exec->argument(0).isObject())
 292         return throwVMError(exec, createTypeError(exec, "Properties can only be defined on Objects."));
 293     JSObject* O = asObject(exec->argument(0));
 294     UString propertyName = exec->argument(1).toString(exec)->value(exec);
 295     if (exec->hadException())
 296         return JSValue::encode(jsNull());
 297     PropertyDescriptor descriptor;
 298     if (!toPropertyDescriptor(exec, exec->argument(2), descriptor))
 299         return JSValue::encode(jsNull());
 300     ASSERT((descriptor.attributes() & Accessor) || (!descriptor.isAccessorDescriptor()));
 301     ASSERT(!exec->hadException());
 302     O->methodTable()->defineOwnProperty(O, exec, Identifier(exec, propertyName), descriptor, true);
 303     return JSValue::encode(O);
 304 }
 305
 306 static JSValue defineProperties(ExecState* exec, JSObject* object, JSObject* properties)
 307 {
 308     PropertyNameArray propertyNames(exec);
 309     asObject(properties)->methodTable()->getOwnPropertyNames(asObject(properties), exec, propertyNames, ExcludeDontEnumProperties);
 310     size_t numProperties = propertyNames.size();
 311     Vector<PropertyDescriptor> descriptors;
 312     MarkedArgumentBuffer markBuffer;
 313     for (size_t i = 0; i < numProperties; i++) {
 314         PropertySlot slot;
 315         JSValue prop = properties->get(exec, propertyNames[i]);
 316         if (exec->hadException())
 317             return jsNull();
 318         PropertyDescriptor descriptor;
 319         if (!toPropertyDescriptor(exec, prop, descriptor))
 320             return jsNull();
 321         descriptors.append(descriptor);
 322         // Ensure we mark all the values that we're accumulating
 323         if (descriptor.isDataDescriptor() && descriptor.value())
 324             markBuffer.append(descriptor.value());
 325         if (descriptor.isAccessorDescriptor()) {
 326             if (descriptor.getter())
 327                 markBuffer.append(descriptor.getter());
 328             if (descriptor.setter())
 329                 markBuffer.append(descriptor.setter());
 330         }
 331     }
 332     for (size_t i = 0; i < numProperties; i++) {
 333         object->methodTable()->defineOwnProperty(object, exec, propertyNames[i], descriptors[i], true);
 334         if (exec->hadException())
 335             return jsNull();
 336     }
 337     return object;
 338 }
 339
 340 EncodedJSValue JSC_HOST_CALL objectConstructorDefineProperties(ExecState* exec)
 341 {
 342     if (!exec->argument(0).isObject())
 343         return throwVMError(exec, createTypeError(exec, "Properties can only be defined on Objects."));
 344     return JSValue::encode(defineProperties(exec, asObject(exec->argument(0)), exec->argument(1).toObject(exec)));
 345 }
 346
 347 EncodedJSValue JSC_HOST_CALL objectConstructorCreate(ExecState* exec)
 348 {
 349     if (!exec->argument(0).isObject() && !exec->argument(0).isNull())
 350         return throwVMError(exec, createTypeError(exec, "Object prototype may only be an Object or null."));
 351     JSValue proto = exec->argument(0);
 352     JSObject* newObject = proto.isObject() ? constructEmptyObject(exec, asObject(proto)->inheritorID(exec->globalData())) : constructEmptyObject(exec, exec->lexicalGlobalObject()->nullPrototypeObjectStructure());
 353     if (exec->argument(1).isUndefined())
 354         return JSValue::encode(newObject);
 355     if (!exec->argument(1).isObject())
 356         return throwVMError(exec, createTypeError(exec, "Property descriptor list must be an Object."));
 357     return JSValue::encode(defineProperties(exec, newObject, asObject(exec->argument(1))));
 358 }
 359
 360 EncodedJSValue JSC_HOST_CALL objectConstructorSeal(ExecState* exec)
 361 {
 362     // 1. If Type(O) is not Object throw a TypeError exception.
 363     JSValue obj = exec->argument(0);
 364     if (!obj.isObject())
 365         return throwVMError(exec, createTypeError(exec, "Object.seal can only be called on Objects."));
 366     JSObject* object = asObject(obj);
 367
 368     if (isJSFinalObject(object)) {
 369         object->seal(exec->globalData());
 370         return JSValue::encode(obj);
 371     }
 372
 373     // 2. For each named own property name P of O,
 374     PropertyNameArray properties(exec);
 375     object->methodTable()->getOwnPropertyNames(object, exec, properties, IncludeDontEnumProperties);
 376     PropertyNameArray::const_iterator end = properties.end();
 377     for (PropertyNameArray::const_iterator iter = properties.begin(); iter != end; ++iter) {
 378         // a. Let desc be the result of calling the [[GetOwnProperty]] internal method of O with P.
 379         PropertyDescriptor desc;
 380         if (!object->methodTable()->getOwnPropertyDescriptor(object, exec, *iter, desc))
 381             continue;
 382         // b. If desc.[[Configurable]] is true, set desc.[[Configurable]] to false.
 383         desc.setConfigurable(false);
 384         // c. Call the [[DefineOwnProperty]] internal method of O with P, desc, and true as arguments.
 385         object->methodTable()->defineOwnProperty(object, exec, *iter, desc, true);
 386         if (exec->hadException())
 387             return JSValue::encode(obj);
 388     }
 389
 390     // 3. Set the [[Extensible]] internal property of O to false.
 391     object->preventExtensions(exec->globalData());
 392
 393     // 4. Return O.
 394     return JSValue::encode(obj);
 395 }
 396
 397 EncodedJSValue JSC_HOST_CALL objectConstructorFreeze(ExecState* exec)
 398 {
 399     // 1. If Type(O) is not Object throw a TypeError exception.
 400     JSValue obj = exec->argument(0);
 401     if (!obj.isObject())
 402         return throwVMError(exec, createTypeError(exec, "Object.freeze can only be called on Objects."));
 403     JSObject* object = asObject(obj);
 404
 405     if (isJSFinalObject(object)) {
 406         object->freeze(exec->globalData());
 407         return JSValue::encode(obj);
 408     }
 409
 410     // 2. For each named own property name P of O,
 411     PropertyNameArray properties(exec);
 412     object->methodTable()->getOwnPropertyNames(object, exec, properties, IncludeDontEnumProperties);
 413     PropertyNameArray::const_iterator end = properties.end();
 414     for (PropertyNameArray::const_iterator iter = properties.begin(); iter != end; ++iter) {
 415         // a. Let desc be the result of calling the [[GetOwnProperty]] internal method of O with P.
 416         PropertyDescriptor desc;
 417         if (!object->methodTable()->getOwnPropertyDescriptor(object, exec, *iter, desc))
 418             continue;
 419         // b. If IsDataDescriptor(desc) is true, then
 420         // i. If desc.[[Writable]] is true, set desc.[[Writable]] to false.
 421         if (desc.isDataDescriptor())
 422             desc.setWritable(false);
 423         // c. If desc.[[Configurable]] is true, set desc.[[Configurable]] to false.
 424         desc.setConfigurable(false);
 425         // d. Call the [[DefineOwnProperty]] internal method of O with P, desc, and true as arguments.
 426         object->methodTable()->defineOwnProperty(object, exec, *iter, desc, true);
 427         if (exec->hadException())
 428             return JSValue::encode(obj);
 429     }
 430
 431     // 3. Set the [[Extensible]] internal property of O to false.
 432     object->preventExtensions(exec->globalData());
 433
 434     // 4. Return O.
 435     return JSValue::encode(obj);
 436 }
 437
 438 EncodedJSValue JSC_HOST_CALL objectConstructorPreventExtensions(ExecState* exec)
 439 {
 440     JSValue obj = exec->argument(0);
 441     if (!obj.isObject())
 442         return throwVMError(exec, createTypeError(exec, "Object.preventExtensions can only be called on Objects."));
 443     asObject(obj)->preventExtensions(exec->globalData());
 444     return JSValue::encode(obj);
 445 }
 446
 447 EncodedJSValue JSC_HOST_CALL objectConstructorIsSealed(ExecState* exec)
 448 {
 449     // 1. If Type(O) is not Object throw a TypeError exception.
 450     JSValue obj = exec->argument(0);
 451     if (!obj.isObject())
 452         return throwVMError(exec, createTypeError(exec, "Object.isSealed can only be called on Objects."));
 453     JSObject* object = asObject(obj);
 454
 455     if (isJSFinalObject(object))
 456         return JSValue::encode(jsBoolean(object->isSealed(exec->globalData())));
 457
 458     // 2. For each named own property name P of O,
 459     PropertyNameArray properties(exec);
 460     object->methodTable()->getOwnPropertyNames(object, exec, properties, IncludeDontEnumProperties);
 461     PropertyNameArray::const_iterator end = properties.end();
 462     for (PropertyNameArray::const_iterator iter = properties.begin(); iter != end; ++iter) {
 463         // a. Let desc be the result of calling the [[GetOwnProperty]] internal method of O with P.
 464         PropertyDescriptor desc;
 465         if (!object->methodTable()->getOwnPropertyDescriptor(object, exec, *iter, desc))
 466             continue;
 467         // b. If desc.[[Configurable]] is true, then return false.
 468         if (desc.configurable())
 469             return JSValue::encode(jsBoolean(false));
 470     }
 471
 472     // 3. If the [[Extensible]] internal property of O is false, then return true.
 473     // 4. Otherwise, return false.
 474     return JSValue::encode(jsBoolean(!object->isExtensible()));
 475 }
 476
 477 EncodedJSValue JSC_HOST_CALL objectConstructorIsFrozen(ExecState* exec)
 478 {
 479     // 1. If Type(O) is not Object throw a TypeError exception.
 480     JSValue obj = exec->argument(0);
 481     if (!obj.isObject())
 482         return throwVMError(exec, createTypeError(exec, "Object.isFrozen can only be called on Objects."));
 483     JSObject* object = asObject(obj);
 484
 485     if (isJSFinalObject(object))
 486         return JSValue::encode(jsBoolean(object->isFrozen(exec->globalData())));
 487
 488     // 2. For each named own property name P of O,
 489     PropertyNameArray properties(exec);
 490     object->methodTable()->getOwnPropertyNames(object, exec, properties, IncludeDontEnumProperties);
 491     PropertyNameArray::const_iterator end = properties.end();
 492     for (PropertyNameArray::const_iterator iter = properties.begin(); iter != end; ++iter) {
 493         // a. Let desc be the result of calling the [[GetOwnProperty]] internal method of O with P.
 494         PropertyDescriptor desc;
 495         if (!object->methodTable()->getOwnPropertyDescriptor(object, exec, *iter, desc))
 496             continue;
 497         // b. If IsDataDescriptor(desc) is true then
 498         // i. If desc.[[Writable]] is true, return false. c. If desc.[[Configurable]] is true, then return false.
 499         if ((desc.isDataDescriptor() && desc.writable()) || desc.configurable())
 500             return JSValue::encode(jsBoolean(false));
 501     }
 502
 503     // 3. If the [[Extensible]] internal property of O is false, then return true.
 504     // 4. Otherwise, return false.
 505     return JSValue::encode(jsBoolean(!object->isExtensible()));
 506 }
 507
 508 EncodedJSValue JSC_HOST_CALL objectConstructorIsExtensible(ExecState* exec)
 509 {
 510     JSValue obj = exec->argument(0);
 511     if (!obj.isObject())
 512         return throwVMError(exec, createTypeError(exec, "Object.isExtensible can only be called on Objects."));
 513     return JSValue::encode(jsBoolean(asObject(obj)->isExtensible()));
 514 }
 515
 516 } // namespace JSC