JSArray.cpp 71.6 KB
Newer Older
darin's avatar
darin committed
1 2
/*
 *  Copyright (C) 1999-2000 Harri Porten (porten@kde.org)
3
 *  Copyright (C) 2003, 2007, 2008, 2009 Apple Inc. All rights reserved.
darin's avatar
darin committed
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
 *  Copyright (C) 2003 Peter Kelly (pmk@post.com)
 *  Copyright (C) 2006 Alexey Proskuryakov (ap@nypop.com)
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library 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
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */

#include "config.h"
darin@apple.com's avatar
darin@apple.com committed
24
#include "JSArray.h"
darin's avatar
darin committed
25

darin@apple.com's avatar
darin@apple.com committed
26
#include "ArrayPrototype.h"
27
#include "CachedCall.h"
28
#include "Error.h"
29
#include "Executable.h"
30
#include "GetterSetter.h"
darin's avatar
darin committed
31
#include "PropertyNameArray.h"
ap@webkit.org's avatar
ap@webkit.org committed
32
#include <wtf/AVLTree.h>
33
#include <wtf/Assertions.h>
34
#include <wtf/OwnPtr.h>
35
#include <Operations.h>
darin's avatar
darin committed
36

37
using namespace std;
ap@webkit.org's avatar
ap@webkit.org committed
38
using namespace WTF;
bdash's avatar
bdash committed
39

40
namespace JSC {
darin's avatar
darin committed
41

ggaren@apple.com's avatar
ggaren@apple.com committed
42 43
ASSERT_CLASS_FITS_IN_CELL(JSArray);

barraclough@apple.com's avatar
barraclough@apple.com committed
44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
// Overview of JSArray
//
// Properties of JSArray objects may be stored in one of three locations:
//   * The regular JSObject property map.
//   * A storage vector.
//   * A sparse map of array entries.
//
// Properties with non-numeric identifiers, with identifiers that are not representable
// as an unsigned integer, or where the value is greater than  MAX_ARRAY_INDEX
// (specifically, this is only one property - the value 0xFFFFFFFFU as an unsigned 32-bit
// integer) are not considered array indices and will be stored in the JSObject property map.
//
// All properties with a numeric identifer, representable as an unsigned integer i,
// where (i <= MAX_ARRAY_INDEX), are an array index and will be stored in either the
// storage vector or the sparse map.  An array index i will be handled in the following
// fashion:
//
61 62
//   * Where (i < MIN_SPARSE_ARRAY_INDEX) the value will be stored in the storage vector,
//     unless the array is in SparseMode in which case all properties go into the map.
barraclough@apple.com's avatar
barraclough@apple.com committed
63 64 65 66 67 68 69 70 71
//   * Where (MIN_SPARSE_ARRAY_INDEX <= i <= MAX_STORAGE_VECTOR_INDEX) the value will either
//     be stored in the storage vector or in the sparse array, depending on the density of
//     data that would be stored in the vector (a vector being used where at least
//     (1 / minDensityMultiplier) of the entries would be populated).
//   * Where (MAX_STORAGE_VECTOR_INDEX < i <= MAX_ARRAY_INDEX) the value will always be stored
//     in the sparse array.

// The definition of MAX_STORAGE_VECTOR_LENGTH is dependant on the definition storageSize
// function below - the MAX_STORAGE_VECTOR_LENGTH limit is defined such that the storage
72 73 74
// size calculation cannot overflow.  (sizeof(ArrayStorage) - sizeof(WriteBarrier<Unknown>)) +
// (vectorLength * sizeof(WriteBarrier<Unknown>)) must be <= 0xFFFFFFFFU (which is maximum value of size_t).
#define MAX_STORAGE_VECTOR_LENGTH static_cast<unsigned>((0xFFFFFFFFU - (sizeof(ArrayStorage) - sizeof(WriteBarrier<Unknown>))) / sizeof(WriteBarrier<Unknown>))
barraclough@apple.com's avatar
barraclough@apple.com committed
75 76 77 78 79

// These values have to be macros to be used in max() and min() without introducing
// a PIC branch in Mach-O binaries, see <rdar://problem/5971391>.
#define MIN_SPARSE_ARRAY_INDEX 10000U
#define MAX_STORAGE_VECTOR_INDEX (MAX_STORAGE_VECTOR_LENGTH - 1)
80
// 0xFFFFFFFF is a bit weird -- is not an array index even though it's an integer.
barraclough@apple.com's avatar
barraclough@apple.com committed
81
#define MAX_ARRAY_INDEX 0xFFFFFFFEU
darin's avatar
darin committed
82

83 84 85 86 87 88 89 90
// The value BASE_VECTOR_LEN is the maximum number of vector elements we'll allocate
// for an array that was created with a sepcified length (e.g. a = new Array(123))
#define BASE_VECTOR_LEN 4U
    
// The upper bound to the size we'll grow a zero length array when the first element
// is added.
#define FIRST_VECTOR_GROW 4U

darin's avatar
darin committed
91
// Our policy for when to use a vector and when to use a sparse map.
barraclough@apple.com's avatar
barraclough@apple.com committed
92 93
// For all array indices under MIN_SPARSE_ARRAY_INDEX, we always use a vector.
// When indices greater than MIN_SPARSE_ARRAY_INDEX are involved, we use a vector
darin's avatar
darin committed
94 95 96
// as long as it is 1/8 full. If more sparse than that, we use a map.
static const unsigned minDensityMultiplier = 8;

97
const ClassInfo JSArray::s_info = {"Array", &JSNonFinalObject::s_info, 0, 0, CREATE_METHOD_TABLE(JSArray)};
darin's avatar
darin committed
98

99 100 101 102 103
// We keep track of the size of the last array after it was grown.  We use this
// as a simple heuristic for as the value to grow the next array from size 0.
// This value is capped by the constant FIRST_VECTOR_GROW defined above.
static unsigned lastArraySize = 0;

darin's avatar
darin committed
104 105
static inline size_t storageSize(unsigned vectorLength)
{
barraclough@apple.com's avatar
barraclough@apple.com committed
106 107 108 109
    ASSERT(vectorLength <= MAX_STORAGE_VECTOR_LENGTH);

    // MAX_STORAGE_VECTOR_LENGTH is defined such that provided (vectorLength <= MAX_STORAGE_VECTOR_LENGTH)
    // - as asserted above - the following calculation cannot overflow.
110
    size_t size = (sizeof(ArrayStorage) - sizeof(WriteBarrier<Unknown>)) + (vectorLength * sizeof(WriteBarrier<Unknown>));
barraclough@apple.com's avatar
barraclough@apple.com committed
111 112
    // Assertion to detect integer overflow in previous calculation (should not be possible, provided that
    // MAX_STORAGE_VECTOR_LENGTH is correctly defined).
113
    ASSERT(((size - (sizeof(ArrayStorage) - sizeof(WriteBarrier<Unknown>))) / sizeof(WriteBarrier<Unknown>) == vectorLength) && (size >= (sizeof(ArrayStorage) - sizeof(WriteBarrier<Unknown>))));
barraclough@apple.com's avatar
barraclough@apple.com committed
114 115

    return size;
darin's avatar
darin committed
116 117 118 119
}

static inline bool isDenseEnoughForVector(unsigned length, unsigned numValues)
{
120
    return length <= MIN_SPARSE_ARRAY_INDEX || length / minDensityMultiplier <= numValues;
darin's avatar
darin committed
121 122
}

123 124
#if !CHECK_ARRAY_CONSISTENCY

darin@apple.com's avatar
darin@apple.com committed
125
inline void JSArray::checkConsistency(ConsistencyCheckType)
126 127 128 129 130
{
}

#endif

131 132
JSArray::JSArray(JSGlobalData& globalData, Structure* structure)
    : JSNonFinalObject(globalData, structure)
133
    , m_storage(0)
weinig@apple.com's avatar
weinig@apple.com committed
134
{
135 136
}

137
void JSArray::finishCreation(JSGlobalData& globalData, unsigned initialLength)
138 139
{
    Base::finishCreation(globalData);
140 141
    ASSERT(inherits(&s_info));

142 143
    unsigned initialVectorLength = BASE_VECTOR_LEN;
    unsigned initialStorageSize = storageSize(initialVectorLength);
weinig@apple.com's avatar
weinig@apple.com committed
144

145
    m_storage = static_cast<ArrayStorage*>(fastMalloc(initialStorageSize));
146
    m_storage->m_allocBase = m_storage;
147
    m_storage->m_length = initialLength;
148
    m_indexBias = 0;
149 150 151 152 153 154 155
    m_vectorLength = initialVectorLength;
    m_storage->m_sparseValueMap = 0;
    m_storage->subclassData = 0;
    m_storage->m_numValuesInVector = 0;
#if CHECK_ARRAY_CONSISTENCY
    m_storage->m_inCompactInitialization = false;
#endif
weinig@apple.com's avatar
weinig@apple.com committed
156

157 158 159
    WriteBarrier<Unknown>* vector = m_storage->m_vector;
    for (size_t i = 0; i < initialVectorLength; ++i)
        vector[i].clear();
160

161 162 163
    checkConsistency();
    
    Heap::heap(this)->reportExtraMemoryCost(initialStorageSize);
weinig@apple.com's avatar
weinig@apple.com committed
164 165
}

166
JSArray* JSArray::tryFinishCreationUninitialized(JSGlobalData& globalData, unsigned initialLength)
darin's avatar
darin committed
167
{
168
    Base::finishCreation(globalData);
169 170
    ASSERT(inherits(&s_info));

171 172 173 174 175 176 177 178
    // Check for lengths larger than we can handle with a vector.
    if (initialLength > MAX_STORAGE_VECTOR_LENGTH)
        return 0;

    unsigned initialVectorLength = max(initialLength, BASE_VECTOR_LEN);
    unsigned initialStorageSize = storageSize(initialVectorLength);

    m_storage = static_cast<ArrayStorage*>(fastMalloc(initialStorageSize));
179
    m_storage->m_allocBase = m_storage;
180
    m_storage->m_length = 0;
181
    m_indexBias = 0;
182
    m_vectorLength = initialVectorLength;
183 184
    m_storage->m_sparseValueMap = 0;
    m_storage->subclassData = 0;
185
    m_storage->m_numValuesInVector = initialLength;
186
#if CHECK_ARRAY_CONSISTENCY
187
    m_storage->m_inCompactInitialization = true;
188
#endif
189

190 191 192 193 194 195
    WriteBarrier<Unknown>* vector = m_storage->m_vector;
    for (size_t i = initialLength; i < initialVectorLength; ++i)
        vector[i].clear();

    Heap::heap(this)->reportExtraMemoryCost(initialStorageSize);
    return this;
darin's avatar
darin committed
196 197
}

darin@apple.com's avatar
darin@apple.com committed
198
JSArray::~JSArray()
darin's avatar
darin committed
199
{
200
    ASSERT(jsCast<JSArray*>(this));
201

202 203 204 205 206
    // If we are unable to allocate memory for m_storage then this may be null.
    if (!m_storage)
        return;

    checkConsistency(DestructorConsistencyCheck);
207 208
    delete m_storage->m_sparseValueMap;
    fastFree(m_storage->m_allocBase);
darin's avatar
darin committed
209 210
}

211 212 213 214 215
void JSArray::destroy(JSCell* cell)
{
    jsCast<JSArray*>(cell)->JSArray::~JSArray();
}

216
inline std::pair<SparseArrayValueMap::iterator, bool> SparseArrayValueMap::add(JSArray* array, unsigned i)
217
{
218 219 220 221 222 223 224 225
    SparseArrayEntry entry;
    std::pair<iterator, bool> result = m_map.add(i, entry);
    size_t capacity = m_map.capacity();
    if (capacity != m_reportedCapacity) {
        Heap::heap(array)->reportExtraMemoryCost((capacity - m_reportedCapacity) * (sizeof(unsigned) + sizeof(WriteBarrier<Unknown>)));
        m_reportedCapacity = capacity;
    }
    return result;
226 227
}

228
inline void SparseArrayValueMap::put(ExecState* exec, JSArray* array, unsigned i, JSValue value)
229
{
230 231 232 233 234 235 236 237 238 239
    SparseArrayEntry& entry = add(array, i).first->second;

    if (!(entry.attributes & (Getter | Setter))) {
        if (entry.attributes & ReadOnly) {
            // FIXME: should throw if being called from strict mode.
            // throwTypeError(exec, StrictModeReadonlyPropertyWriteError);
            return;
        }

        entry.set(exec->globalData(), array, value);
240
        return;
241
    }
242

243 244 245 246 247 248 249
    JSValue accessor = entry.Base::get();
    ASSERT(accessor.isGetterSetter());
    JSObject* setter = asGetterSetter(accessor)->setter();
    
    if (!setter) {
        throwTypeError(exec, "setting a property that has only a getter");
        return;
250
    }
251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303

    CallData callData;
    CallType callType = setter->methodTable()->getCallData(setter, callData);
    MarkedArgumentBuffer args;
    args.append(value);
    call(exec, setter, callType, callData, array, args);
}

inline void SparseArrayEntry::get(PropertySlot& slot) const
{
    JSValue value = Base::get();
    ASSERT(value);

    if (LIKELY(!value.isGetterSetter())) {
        slot.setValue(value);
        return;
    }

    JSObject* getter = asGetterSetter(value)->getter();
    if (!getter) {
        slot.setUndefined();
        return;
    }

    slot.setGetterSlot(getter);
}

inline void SparseArrayEntry::get(PropertyDescriptor& descriptor) const
{
    descriptor.setDescriptor(Base::get(), attributes);
}

inline JSValue SparseArrayEntry::get(ExecState* exec, JSArray* array) const
{
    JSValue result = Base::get();
    ASSERT(result);

    if (LIKELY(!result.isGetterSetter()))
        return result;

    JSObject* getter = asGetterSetter(result)->getter();
    if (!getter)
        return jsUndefined();

    CallData callData;
    CallType callType = getter->methodTable()->getCallData(getter, callData);
    return call(exec, getter, callType, callData, array, exec->emptyList());
}

inline JSValue SparseArrayEntry::getNonSparseMode() const
{
    ASSERT(!attributes);
    return Base::get();
304 305 306 307 308 309 310 311 312
}

inline void SparseArrayValueMap::visitChildren(SlotVisitor& visitor)
{
    iterator end = m_map.end();
    for (iterator it = m_map.begin(); it != end; ++it)
        visitor.append(&it->second);
}

313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348
void JSArray::enterSparseMode(JSGlobalData& globalData)
{
    ArrayStorage* storage = m_storage;
    SparseArrayValueMap* map = storage->m_sparseValueMap;

    if (!map)
        map = storage->m_sparseValueMap = new SparseArrayValueMap;

    if (map->sparseMode())
        return;

    map->setSparseMode();

    unsigned usedVectorLength = min(storage->m_length, m_vectorLength);
    for (unsigned i = 0; i < usedVectorLength; ++i) {
        JSValue value = storage->m_vector[i].get();
        // This will always be a new entry in the map, so no need to check we can write,
        // and attributes are default so no need to set them.
        if (value)
            map->add(this, i).first->second.set(globalData, this, value);
    }

    ArrayStorage* newStorage = static_cast<ArrayStorage*>(fastMalloc(storageSize(0)));
    memcpy(newStorage, m_storage, storageSize(0));
    newStorage->m_allocBase = newStorage;
    fastFree(m_storage);
    m_storage = newStorage;
    m_indexBias = 0;
    m_vectorLength = 0;
}

void JSArray::putDescriptor(ExecState* exec, SparseArrayEntry* entryInMap, PropertyDescriptor& descriptor, PropertyDescriptor& oldDescriptor)
{
    if (descriptor.isDataDescriptor()) {
        if (descriptor.value())
            entryInMap->set(exec->globalData(), this, descriptor.value());
349 350
        else if (oldDescriptor.isAccessorDescriptor())
            entryInMap->set(exec->globalData(), this, jsUndefined());
351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458
        entryInMap->attributes = descriptor.attributesOverridingCurrent(oldDescriptor) & ~(Getter | Setter);
        return;
    }

    if (descriptor.isAccessorDescriptor()) {
        JSObject* getter = 0;
        if (descriptor.getter() && descriptor.getter().isObject())
            getter = asObject(descriptor.getter());
        if (!getter && oldDescriptor.isAccessorDescriptor()) {
            if (oldDescriptor.getter() && oldDescriptor.getter().isObject())
                getter = asObject(oldDescriptor.getter());
        }
        JSObject* setter = 0;
        if (descriptor.setter() && descriptor.setter().isObject())
            setter = asObject(descriptor.setter());
        if (!setter && oldDescriptor.isAccessorDescriptor()) {
            if (oldDescriptor.setter() && oldDescriptor.setter().isObject())
                setter = asObject(oldDescriptor.setter());
        }

        GetterSetter* accessor = GetterSetter::create(exec);
        if (getter)
            accessor->setGetter(exec->globalData(), getter);
        if (setter)
            accessor->setSetter(exec->globalData(), setter);

        entryInMap->set(exec->globalData(), this, accessor);
        entryInMap->attributes = descriptor.attributesOverridingCurrent(oldDescriptor) & ~DontDelete;
        return;
    }

    ASSERT(descriptor.isGenericDescriptor());
    entryInMap->attributes = descriptor.attributesOverridingCurrent(oldDescriptor);
}

static bool reject(ExecState* exec, bool throwException, const char* message)
{
    if (throwException)
        throwTypeError(exec, message);
    return false;
}

// Defined in ES5.1 8.12.9
bool JSArray::defineOwnNumericProperty(ExecState* exec, unsigned index, PropertyDescriptor& descriptor, bool throwException)
{
    ASSERT(index != 0xFFFFFFFF);

    if (!inSparseMode()) {
        // Fast case: we're putting a regular property to a regular array
        // FIXME: this will pessimistically assume that if attributes are missing then they'll default to false
        // – however if the property currently exists missing attributes will override from their current 'true'
        // state (i.e. defineOwnProperty could be used to set a value without needing to entering 'SparseMode').
        if (!descriptor.attributes()) {
            ASSERT(!descriptor.isAccessorDescriptor());
            putByIndex(this, exec, index, descriptor.value());
            return true;
        }

        enterSparseMode(exec->globalData());
    }

    SparseArrayValueMap* map = m_storage->m_sparseValueMap;
    ASSERT(map);

    // 1. Let current be the result of calling the [[GetOwnProperty]] internal method of O with property name P.
    std::pair<SparseArrayValueMap::iterator, bool> result = map->add(this, index);
    SparseArrayEntry* entryInMap = &result.first->second;

    // 2. Let extensible be the value of the [[Extensible]] internal property of O.
    // 3. If current is undefined and extensible is false, then Reject.
    // 4. If current is undefined and extensible is true, then
    if (result.second) {
        if (!isExtensible()) {
            map->remove(result.first);
            return reject(exec, throwException, "Attempting to define property on object that is not extensible.");
        }

        // 4.a. If IsGenericDescriptor(Desc) or IsDataDescriptor(Desc) is true, then create an own data property
        // named P of object O whose [[Value]], [[Writable]], [[Enumerable]] and [[Configurable]] attribute values
        // are described by Desc. If the value of an attribute field of Desc is absent, the attribute of the newly
        // created property is set to its default value.
        // 4.b. Else, Desc must be an accessor Property Descriptor so, create an own accessor property named P of
        // object O whose [[Get]], [[Set]], [[Enumerable]] and [[Configurable]] attribute values are described by
        // Desc. If the value of an attribute field of Desc is absent, the attribute of the newly created property
        // is set to its default value.
        // 4.c. Return true.

        PropertyDescriptor defaults;
        entryInMap->setWithoutWriteBarrier(jsUndefined());
        entryInMap->attributes = DontDelete | DontEnum | ReadOnly;
        entryInMap->get(defaults);

        putDescriptor(exec, entryInMap, descriptor, defaults);
        if (index >= m_storage->m_length)
            m_storage->m_length = index + 1;
        return true;
    }

    // 5. Return true, if every field in Desc is absent.
    // 6. Return true, if every field in Desc also occurs in current and the value of every field in Desc is the same value as the corresponding field in current when compared using the SameValue algorithm (9.12).
    PropertyDescriptor current;
    entryInMap->get(current);
    if (descriptor.isEmpty() || descriptor.equalTo(exec, current))
        return true;

    // 7. If the [[Configurable]] field of current is false then
    if (!current.configurable()) {
        // 7.a. Reject, if the [[Configurable]] field of Desc is true.
459
        if (descriptor.configurablePresent() && !descriptor.configurable())
460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585
            return reject(exec, throwException, "Attempting to change configurable attribute of unconfigurable property.");
        // 7.b. Reject, if the [[Enumerable]] field of Desc is present and the [[Enumerable]] fields of current and Desc are the Boolean negation of each other.
        if (descriptor.enumerablePresent() && current.enumerable() != descriptor.enumerable())
            return reject(exec, throwException, "Attempting to change enumerable attribute of unconfigurable property.");
    }

    // 8. If IsGenericDescriptor(Desc) is true, then no further validation is required.
    if (!descriptor.isGenericDescriptor()) {
        // 9. Else, if IsDataDescriptor(current) and IsDataDescriptor(Desc) have different results, then
        if (current.isDataDescriptor() != descriptor.isDataDescriptor()) {
            // 9.a. Reject, if the [[Configurable]] field of current is false.
            if (!current.configurable())
                return reject(exec, throwException, "Attempting to change access mechanism for an unconfigurable property.");
            // 9.b. If IsDataDescriptor(current) is true, then convert the property named P of object O from a
            // data property to an accessor property. Preserve the existing values of the converted property‘s
            // [[Configurable]] and [[Enumerable]] attributes and set the rest of the property‘s attributes to
            // their default values.
            // 9.c. Else, convert the property named P of object O from an accessor property to a data property.
            // Preserve the existing values of the converted property‘s [[Configurable]] and [[Enumerable]]
            // attributes and set the rest of the property‘s attributes to their default values.
        } else if (current.isDataDescriptor() && descriptor.isDataDescriptor()) {
            // 10. Else, if IsDataDescriptor(current) and IsDataDescriptor(Desc) are both true, then
            // 10.a. If the [[Configurable]] field of current is false, then
            if (!current.configurable() && !current.writable()) {
                // 10.a.i. Reject, if the [[Writable]] field of current is false and the [[Writable]] field of Desc is true.
                if (descriptor.writable())
                    return reject(exec, throwException, "Attempting to change writable attribute of unconfigurable property.");
                // 10.a.ii. If the [[Writable]] field of current is false, then
                // 10.a.ii.1. Reject, if the [[Value]] field of Desc is present and SameValue(Desc.[[Value]], current.[[Value]]) is false.
                if (descriptor.value() && !sameValue(exec, descriptor.value(), current.value()))
                    return reject(exec, throwException, "Attempting to change value of a readonly property.");
            }
            // 10.b. else, the [[Configurable]] field of current is true, so any change is acceptable.
        } else {
            // 11. Else, IsAccessorDescriptor(current) and IsAccessorDescriptor(Desc) are both true so, if the [[Configurable]] field of current is false, then
            if (!current.configurable()) {
                // 11.i. Reject, if the [[Set]] field of Desc is present and SameValue(Desc.[[Set]], current.[[Set]]) is false.
                if (descriptor.setterPresent() && descriptor.setter() != current.setter())
                    return reject(exec, throwException, "Attempting to change the setter of an unconfigurable property.");
                // 11.ii. Reject, if the [[Get]] field of Desc is present and SameValue(Desc.[[Get]], current.[[Get]]) is false.
                if (descriptor.getterPresent() && descriptor.getter() != current.getter())
                    return reject(exec, throwException, "Attempting to change the getter of an unconfigurable property.");
            }
        }
    }

    // 12. For each attribute field of Desc that is present, set the correspondingly named attribute of the property named P of object O to the value of the field.
    putDescriptor(exec, entryInMap, descriptor, current);
    // 13. Return true.
    return true;
}

void JSArray::setLengthWritable(ExecState* exec, bool writable)
{
    ASSERT(isLengthWritable() || !writable);
    if (!isLengthWritable() || writable)
        return;

    enterSparseMode(exec->globalData());

    SparseArrayValueMap* map = m_storage->m_sparseValueMap;
    ASSERT(map);
    map->setLengthIsReadOnly();
}

// Defined in ES5.1 15.4.5.1
bool JSArray::defineOwnProperty(JSObject* object, ExecState* exec, const Identifier& propertyName, PropertyDescriptor& descriptor, bool throwException)
{
    JSArray* array = static_cast<JSArray*>(object);

    // 3. If P is "length", then
    if (propertyName == exec->propertyNames().length) {
        // All paths through length definition call the default [[DefineOwnProperty]], hence:
        // from ES5.1 8.12.9 7.a.
        if (descriptor.configurable())
            return reject(exec, throwException, "Attempting to change configurable attribute of unconfigurable property.");
        // from ES5.1 8.12.9 7.b.
        if (descriptor.enumerable())
            return reject(exec, throwException, "Attempting to change enumerable attribute of unconfigurable property.");

        // a. If the [[Value]] field of Desc is absent, then
        // a.i. Return the result of calling the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", Desc, and Throw as arguments.
        if (descriptor.isAccessorDescriptor())
            return reject(exec, throwException, "Attempting to change access mechanism for an unconfigurable property.");
        // from ES5.1 8.12.9 10.a.
        if (!array->isLengthWritable() && descriptor.writable())
            return reject(exec, throwException, "Attempting to change writable attribute of unconfigurable property.");
        // This descriptor is either just making length read-only, or changing nothing!
        if (!descriptor.value()) {
            array->setLengthWritable(exec, descriptor.writable());
            return true;
        }
        
        // b. Let newLenDesc be a copy of Desc.
        // c. Let newLen be ToUint32(Desc.[[Value]]).
        unsigned newLen = descriptor.value().toUInt32(exec);
        // d. If newLen is not equal to ToNumber( Desc.[[Value]]), throw a RangeError exception.
        if (newLen != descriptor.value().toNumber(exec)) {
            throwError(exec, createRangeError(exec, "Invalid array length"));
            return false;
        }

        // Based on SameValue check in 8.12.9, this is always okay.
        if (newLen == array->length()) {
            array->setLengthWritable(exec, descriptor.writable());
            return true;
        }

        // e. Set newLenDesc.[[Value] to newLen.
        // f. If newLen >= oldLen, then
        // f.i. Return the result of calling the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", newLenDesc, and Throw as arguments.
        // g. Reject if oldLenDesc.[[Writable]] is false.
        if (!array->isLengthWritable())
            return reject(exec, throwException, "Attempting to change value of a readonly property.");
        
        // h. If newLenDesc.[[Writable]] is absent or has the value true, let newWritable be true.
        // i. Else,
        // i.i. Need to defer setting the [[Writable]] attribute to false in case any elements cannot be deleted.
        // i.ii. Let newWritable be false.
        // i.iii. Set newLenDesc.[[Writable] to true.
        // j. Let succeeded be the result of calling the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", newLenDesc, and Throw as arguments.
        // k. If succeeded is false, return false.
        // l. While newLen < oldLen repeat,
        // l.i. Set oldLen to oldLen – 1.
        // l.ii. Let deleteSucceeded be the result of calling the [[Delete]] internal method of A passing ToString(oldLen) and false as arguments.
        // l.iii. If deleteSucceeded is false, then
586
        if (!array->setLength(exec, newLen, throwException)) {
587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621
            // 1. Set newLenDesc.[[Value] to oldLen+1.
            // 2. If newWritable is false, set newLenDesc.[[Writable] to false.
            // 3. Call the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", newLenDesc, and false as arguments.
            // 4. Reject.
            array->setLengthWritable(exec, descriptor.writable());
            return false;
        }

        // m. If newWritable is false, then
        // i. Call the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", Property Descriptor{[[Writable]]: false}, and false as arguments. This call will always return true.
        array->setLengthWritable(exec, descriptor.writable());
        // n. Return true.
        return true;
    }

    // 4. Else if P is an array index (15.4), then
    bool isArrayIndex;
    // a. Let index be ToUint32(P).
    unsigned index = propertyName.toArrayIndex(isArrayIndex);
    if (isArrayIndex) {
        // b. Reject if index >= oldLen and oldLenDesc.[[Writable]] is false.
        if (index >= array->length() && !array->isLengthWritable())
            return reject(exec, throwException, "Attempting to define numeric property on array with non-writable length property.");
        // c. Let succeeded be the result of calling the default [[DefineOwnProperty]] internal method (8.12.9) on A passing P, Desc, and false as arguments.
        // d. Reject if succeeded is false.
        // e. If index >= oldLen
        // e.i. Set oldLenDesc.[[Value]] to index + 1.
        // e.ii. Call the default [[DefineOwnProperty]] internal method (8.12.9) on A passing "length", oldLenDesc, and false as arguments. This call will always return true.
        // f. Return true.
        return array->defineOwnNumericProperty(exec, index, descriptor, throwException);
    }

    return JSObject::defineOwnProperty(object, exec, propertyName, descriptor, throwException);
}

622
bool JSArray::getOwnPropertySlotByIndex(JSCell* cell, ExecState* exec, unsigned i, PropertySlot& slot)
623
{
624
    JSArray* thisObject = jsCast<JSArray*>(cell);
625
    ArrayStorage* storage = thisObject->m_storage;
626
    
ggaren@apple.com's avatar
ggaren@apple.com committed
627
    if (i >= storage->m_length) {
barraclough@apple.com's avatar
barraclough@apple.com committed
628
        if (i > MAX_ARRAY_INDEX)
629
            return thisObject->methodTable()->getOwnPropertySlot(thisObject, exec, Identifier::from(exec, i), slot);
darin's avatar
darin committed
630 631 632
        return false;
    }

633
    if (i < thisObject->m_vectorLength) {
634 635 636
        JSValue value = storage->m_vector[i].get();
        if (value) {
            slot.setValue(value);
darin's avatar
darin committed
637 638 639
            return true;
        }
    } else if (SparseArrayValueMap* map = storage->m_sparseValueMap) {
640 641
        SparseArrayValueMap::iterator it = map->find(i);
        if (it != map->notFound()) {
642
            it->second.get(slot);
643
            return true;
darin's avatar
darin committed
644 645 646
        }
    }

647
    return JSObject::getOwnPropertySlot(thisObject, exec, Identifier::from(exec, i), slot);
darin's avatar
darin committed
648 649
}

650 651
bool JSArray::getOwnPropertySlot(JSCell* cell, ExecState* exec, const Identifier& propertyName, PropertySlot& slot)
{
652
    JSArray* thisObject = jsCast<JSArray*>(cell);
darin's avatar
darin committed
653
    if (propertyName == exec->propertyNames().length) {
654
        slot.setValue(jsNumber(thisObject->length()));
darin's avatar
darin committed
655 656 657 658
        return true;
    }

    bool isArrayIndex;
659
    unsigned i = propertyName.toArrayIndex(isArrayIndex);
darin's avatar
darin committed
660
    if (isArrayIndex)
661
        return JSArray::getOwnPropertySlotByIndex(thisObject, exec, i, slot);
darin's avatar
darin committed
662

663
    return JSObject::getOwnPropertySlot(thisObject, exec, propertyName, slot);
darin's avatar
darin committed
664 665
}

666
bool JSArray::getOwnPropertyDescriptor(JSObject* object, ExecState* exec, const Identifier& propertyName, PropertyDescriptor& descriptor)
667
{
668
    JSArray* thisObject = jsCast<JSArray*>(object);
669
    if (propertyName == exec->propertyNames().length) {
670
        descriptor.setDescriptor(jsNumber(thisObject->length()), DontDelete | DontEnum);
671 672
        return true;
    }
673

674
    ArrayStorage* storage = thisObject->m_storage;
675 676
    
    bool isArrayIndex;
677
    unsigned i = propertyName.toArrayIndex(isArrayIndex);
678
    if (isArrayIndex) {
679
        if (i >= storage->m_length)
680
            return false;
681
        if (i < thisObject->m_vectorLength) {
682
            WriteBarrier<Unknown>& value = storage->m_vector[i];
683
            if (value) {
684
                descriptor.setDescriptor(value.get(), 0);
685 686
                return true;
            }
687
        } else if (SparseArrayValueMap* map = storage->m_sparseValueMap) {
688 689
            SparseArrayValueMap::iterator it = map->find(i);
            if (it != map->notFound()) {
690
                it->second.get(descriptor);
691
                return true;
692 693 694
            }
        }
    }
695
    return JSObject::getOwnPropertyDescriptor(thisObject, exec, propertyName, descriptor);
696 697
}

698 699 700
// ECMA 15.4.5.1
void JSArray::put(JSCell* cell, ExecState* exec, const Identifier& propertyName, JSValue value, PutPropertySlot& slot)
{
701
    JSArray* thisObject = jsCast<JSArray*>(cell);
darin's avatar
darin committed
702
    bool isArrayIndex;
703
    unsigned i = propertyName.toArrayIndex(isArrayIndex);
darin's avatar
darin committed
704
    if (isArrayIndex) {
705
        putByIndex(thisObject, exec, i, value);
darin's avatar
darin committed
706 707 708 709
        return;
    }

    if (propertyName == exec->propertyNames().length) {
weinig@apple.com's avatar
weinig@apple.com committed
710 711
        unsigned newLength = value.toUInt32(exec);
        if (value.toNumber(exec) != static_cast<double>(newLength)) {
712
            throwError(exec, createRangeError(exec, "Invalid array length"));
darin's avatar
darin committed
713 714
            return;
        }
715
        thisObject->setLength(exec, newLength, slot.isStrictMode());
darin's avatar
darin committed
716 717 718
        return;
    }

719
    JSObject::put(thisObject, exec, propertyName, value, slot);
darin's avatar
darin committed
720 721
}

722
void JSArray::putByIndex(JSCell* cell, ExecState* exec, unsigned i, JSValue value)
723
{
724
    JSArray* thisObject = jsCast<JSArray*>(cell);
725 726 727
    thisObject->checkConsistency();

    ArrayStorage* storage = thisObject->m_storage;
728

729
    // Fast case - store to the vector.
730
    if (i < thisObject->m_vectorLength) {
731
        WriteBarrier<Unknown>& valueSlot = storage->m_vector[i];
732 733 734 735 736 737 738 739 740 741
        unsigned length = storage->m_length;

        // Update m_length & m_numValuesInVector as necessary.
        if (i >= length) {
            length = i + 1;
            storage->m_length = length;
            ++storage->m_numValuesInVector;
        } else if (!valueSlot)
            ++storage->m_numValuesInVector;

742 743
        valueSlot.set(exec->globalData(), thisObject, value);
        thisObject->checkConsistency();
darin's avatar
darin committed
744 745 746
        return;
    }

747 748 749 750 751 752 753 754
    // Handle 2^32-1 - this is not an array index (see ES5.1 15.4), and is treated as a regular property.
    if (UNLIKELY(i > MAX_ARRAY_INDEX)) {
        PutPropertySlot slot;
        thisObject->methodTable()->put(thisObject, exec, Identifier::from(exec, i), value, slot);
        return;
    }

    // For all other cases, call putByIndexBeyondVectorLength.
755
    thisObject->putByIndexBeyondVectorLength(exec, i, value);
756
    thisObject->checkConsistency();
757 758
}

759
NEVER_INLINE void JSArray::putByIndexBeyondVectorLength(ExecState* exec, unsigned i, JSValue value)
760
{
761 762
    JSGlobalData& globalData = exec->globalData();

763
    // i should be a valid array index that is outside of the current vector.
764
    ASSERT(i >= m_vectorLength);
765
    ASSERT(i <= MAX_ARRAY_INDEX);
766

767
    ArrayStorage* storage = m_storage;
darin's avatar
darin committed
768
    SparseArrayValueMap* map = storage->m_sparseValueMap;
ap@webkit.org's avatar
ap@webkit.org committed
769

770 771
    // First, handle cases where we don't currently have a sparse map.
    if (LIKELY(!map)) {
772 773 774 775
        // Update m_length if necessary.
        if (i >= storage->m_length)
            storage->m_length = i + 1;

776 777 778
        // Check that it is sensible to still be using a vector, and then try to grow the vector.
        if (LIKELY((isDenseEnoughForVector(i, storage->m_numValuesInVector)) && increaseVectorLength(i + 1))) {
            // success! - reread m_storage since it has likely been reallocated, and store to the vector.
779
            storage = m_storage;
780
            storage->m_vector[i].set(globalData, this, value);
781
            ++storage->m_numValuesInVector;
782
            return;
darin's avatar
darin committed
783
        }
784 785 786
        // We don't want to, or can't use a vector to hold this property - allocate a sparse map & add the value.
        map = new SparseArrayValueMap;
        storage->m_sparseValueMap = map;
787
        map->put(exec, this, i, value);
788
        return;
darin's avatar
darin committed
789 790
    }

791 792 793 794 795 796 797 798 799 800 801 802
    // Update m_length if necessary.
    unsigned length = storage->m_length;
    if (i >= length) {
        // Prohibit growing the array if length is not writable.
        if (map->lengthIsReadOnly()) {
            // FIXME: should throw in strict mode.
            return;
        }
        length = i + 1;
        storage->m_length = length;
    }

803 804 805 806
    // We are currently using a map - check whether we still want to be doing so.
    // We will continue  to use a sparse map if SparseMode is set, a vector would be too sparse, or if allocation fails.
    unsigned numValuesInArray = storage->m_numValuesInVector + map->size();
    if (map->sparseMode() || !isDenseEnoughForVector(length, numValuesInArray) || !increaseVectorLength(length)) {
807
        map->put(exec, this, i, value);
barraclough@apple.com's avatar
barraclough@apple.com committed
808 809
        return;
    }
darin's avatar
darin committed
810

811
    // Reread m_storage afterincreaseVectorLength, update m_numValuesInVector.
812
    storage = m_storage;
813
    storage->m_numValuesInVector = numValuesInArray;
814

815 816 817 818
    // Copy all values from the map into the vector, and delete the map.
    WriteBarrier<Unknown>* vector = storage->m_vector;
    SparseArrayValueMap::const_iterator end = map->end();
    for (SparseArrayValueMap::const_iterator it = map->begin(); it != end; ++it)
819
        vector[it->first].set(globalData, this, it->second.getNonSparseMode());
820 821 822 823 824 825 826 827
    delete map;
    storage->m_sparseValueMap = 0;

    // Store the new property into the vector.
    WriteBarrier<Unknown>& valueSlot = vector[i];
    if (!valueSlot)
        ++storage->m_numValuesInVector;
    valueSlot.set(globalData, this, value);
darin's avatar
darin committed
828 829
}

830 831
bool JSArray::deleteProperty(JSCell* cell, ExecState* exec, const Identifier& propertyName)
{
832
    JSArray* thisObject = jsCast<JSArray*>(cell);
darin's avatar
darin committed
833
    bool isArrayIndex;
834
    unsigned i = propertyName.toArrayIndex(isArrayIndex);
darin's avatar
darin committed
835
    if (isArrayIndex)
836
        return thisObject->methodTable()->deletePropertyByIndex(thisObject, exec, i);
darin's avatar
darin committed
837 838 839 840

    if (propertyName == exec->propertyNames().length)
        return false;

841
    return JSObject::deleteProperty(thisObject, exec, propertyName);
darin's avatar
darin committed
842 843
}

844
bool JSArray::deletePropertyByIndex(JSCell* cell, ExecState* exec, unsigned i)
845
{
846
    JSArray* thisObject = jsCast<JSArray*>(cell);
847 848
    thisObject->checkConsistency();

849 850 851
    if (i > MAX_ARRAY_INDEX)
        return thisObject->methodTable()->deleteProperty(thisObject, exec, Identifier::from(exec, i));

852
    ArrayStorage* storage = thisObject->m_storage;
853
    
854
    if (i < thisObject->m_vectorLength) {
855
        WriteBarrier<Unknown>& valueSlot = storage->m_vector[i];
856 857 858
        if (valueSlot) {
            valueSlot.clear();
            --storage->m_numValuesInVector;
859
        }
860
    } else if (SparseArrayValueMap* map = storage->m_sparseValueMap) {
861 862
        SparseArrayValueMap::iterator it = map->find(i);
        if (it != map->notFound()) {
863 864
            if (it->second.attributes & DontDelete)
                return false;
865
            map->remove(it);
darin's avatar
darin committed
866 867 868
        }
    }

869
    thisObject->checkConsistency();
870 871
    return true;
}
872

873 874
static int compareKeysForQSort(const void* a, const void* b)
{
875 876
    unsigned da = *static_cast<const unsigned*>(a);
    unsigned db = *static_cast<const unsigned*>(b);
877
    return (da > db) - (da < db);
darin's avatar
darin committed
878 879
}

880
void JSArray::getOwnPropertyNames(JSObject* object, ExecState* exec, PropertyNameArray& propertyNames, EnumerationMode mode)
darin's avatar
darin committed
881
{
882
    JSArray* thisObject = jsCast<JSArray*>(object);
darin's avatar
darin committed
883
    // FIXME: Filling PropertyNameArray with an identifier for every integer
884 885
    // is incredibly inefficient for large arrays. We need a different approach,
    // which almost certainly means a different structure for PropertyNameArray.
darin's avatar
darin committed
886

887
    ArrayStorage* storage = thisObject->m_storage;
888
    
889
    unsigned usedVectorLength = min(storage->m_length, thisObject->m_vectorLength);
darin's avatar
darin committed
890
    for (unsigned i = 0; i < usedVectorLength; ++i) {
891
        if (storage->m_vector[i])
ap@webkit.org's avatar
ap@webkit.org committed
892
            propertyNames.add(Identifier::from(exec, i));
darin's avatar
darin committed
893 894 895
    }

    if (SparseArrayValueMap* map = storage->m_sparseValueMap) {
896
        Vector<unsigned> keys;
897 898
        keys.reserveCapacity(map->size());
        
899
        SparseArrayValueMap::const_iterator end = map->end();
900 901
        for (SparseArrayValueMap::const_iterator it = map->begin(); it != end; ++it) {
            if (mode == IncludeDontEnumProperties || !(it->second.attributes & DontEnum))
902
                keys.append(static_cast<unsigned>(it->first));
903 904
        }

905
        qsort(keys.begin(), keys.size(), sizeof(unsigned), compareKeysForQSort);
906
        for (unsigned i = 0; i < keys.size(); ++i)
907
            propertyNames.add(Identifier::from(exec, keys[i]));
darin's avatar
darin committed
908
    }
909

910 911 912
    if (mode == IncludeDontEnumProperties)
        propertyNames.add(exec->propertyNames().length);

913
    JSObject::getOwnPropertyNames(thisObject, exec, propertyNames, mode);
darin's avatar
darin committed
914 915
}

916 917 918 919 920
ALWAYS_INLINE unsigned JSArray::getNewVectorLength(unsigned desiredLength)
{
    ASSERT(desiredLength <= MAX_STORAGE_VECTOR_LENGTH);

    unsigned increasedLength;
921
    unsigned maxInitLength = min(m_storage->m_length, 100000U);
922

923 924
    if (desiredLength < maxInitLength)
        increasedLength = maxInitLength;
925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942
    else if (!m_vectorLength)
        increasedLength = max(desiredLength, lastArraySize);
    else {
        // Mathematically equivalent to:
        //   increasedLength = (newLength * 3 + 1) / 2;
        // or:
        //   increasedLength = (unsigned)ceil(newLength * 1.5));
        // This form is not prone to internal overflow.
        increasedLength = desiredLength + (desiredLength >> 1) + (desiredLength & 1);
    }

    ASSERT(increasedLength >= desiredLength);

    lastArraySize = min(increasedLength, FIRST_VECTOR_GROW);

    return min(increasedLength, MAX_STORAGE_VECTOR_LENGTH);
}

darin@apple.com's avatar
darin@apple.com committed
943
bool JSArray::increaseVectorLength(unsigned newLength)
darin's avatar
darin committed
944
{
ap@webkit.org's avatar
ap@webkit.org committed
945 946
    // This function leaves the array in an internally inconsistent state, because it does not move any values from sparse value map
    // to the vector. Callers have to account for that, because they can do it more efficiently.
947 948
    if (newLength > MAX_STORAGE_VECTOR_LENGTH)
        return false;
ap@webkit.org's avatar
ap@webkit.org committed
949

950
    ArrayStorage* storage = m_storage;
darin's avatar
darin committed
951

952
    unsigned vectorLength = m_vectorLength;
darin's avatar
darin committed
953
    ASSERT(newLength > vectorLength);
954
    unsigned newVectorLength = getNewVectorLength(newLength);
955
    void* baseStorage = storage->m_allocBase;
darin's avatar
darin committed
956

957 958 959 960
    // Fast case - there is no precapacity. In these cases a realloc makes sense.
    if (LIKELY(!m_indexBias)) {
        if (!tryFastRealloc(baseStorage, storageSize(newVectorLength)).getValue(baseStorage))
            return false;
961

962 963
        storage = m_storage = reinterpret_cast_ptr<ArrayStorage*>(baseStorage);
        m_storage->m_allocBase = baseStorage;
964

965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987
        WriteBarrier<Unknown>* vector = storage->m_vector;
        for (unsigned i = vectorLength; i < newVectorLength; ++i)
            vector[i].clear();

        m_vectorLength = newVectorLength;
        
        Heap::heap(this)->reportExtraMemoryCost(storageSize(newVectorLength) - storageSize(vectorLength));
        return true;
    }

    // Remove some, but not all of the precapacity. Atomic decay, & capped to not overflow array length.
    unsigned newIndexBias = min(m_indexBias >> 1, MAX_STORAGE_VECTOR_LENGTH - newVectorLength);
    // Calculate new stoarge capcity, allowing room for the pre-capacity.
    unsigned newStorageCapacity = newVectorLength + newIndexBias;
    void* newAllocBase;
    if (!tryFastMalloc(storageSize(newStorageCapacity)).getValue(newAllocBase))
        return false;
    // The sum of m_vectorLength and m_indexBias will never exceed MAX_STORAGE_VECTOR_LENGTH.
    ASSERT(m_vectorLength <= MAX_STORAGE_VECTOR_LENGTH && (MAX_STORAGE_VECTOR_LENGTH - m_vectorLength) >= m_indexBias);
    unsigned currentCapacity = m_vectorLength + m_indexBias;
    // Currently there is no way to report to the heap that the extra capacity is shrinking!
    if (newStorageCapacity > currentCapacity)
        Heap::heap(this)->reportExtraMemoryCost((newStorageCapacity - currentCapacity) * sizeof(WriteBarrier<Unknown>));
ap@webkit.org's avatar
ap@webkit.org committed
988

989
    m_vectorLength = newVectorLength;
990 991 992 993 994 995 996 997 998 999 1000
    m_indexBias = newIndexBias;
    m_storage = reinterpret_cast_ptr<ArrayStorage*>(reinterpret_cast<WriteBarrier<Unknown>*>(newAllocBase) + m_indexBias);

    // Copy the ArrayStorage header & current contents of the vector, clear the new post-capacity.
    memmove(m_storage, storage, storageSize(vectorLength));
    for (unsigned i = vectorLength; i < m_vectorLength; ++i)
        m_storage->m_vector[i].clear();

    // Free the old allocation, update m_allocBase.
    fastFree(m_storage->m_allocBase);
    m_storage->m_allocBase = newAllocBase;
darin's avatar
darin committed
1001

1002 1003
    return true;
}
darin's avatar
darin committed
1004

1005 1006
// This method makes room in the vector, but leaves the new space uncleared.
bool JSArray::unshiftCountSlowCase(unsigned count)
1007
{
1008 1009
    // If not, we should have handled this on the fast path.
    ASSERT(count > m_indexBias);
1010

1011
    ArrayStorage* storage = m_storage;
1012

1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024
    // Step 1:
    // Gather 4 key metrics:
    //  * usedVectorLength - how many entries are currently in the vector (conservative estimate - fewer may be in use in sparse vectors).
    //  * requiredVectorLength - how many entries are will there be in the vector, after allocating space for 'count' more.
    //  * currentCapacity - what is the current size of the vector, including any pre-capacity.
    //  * desiredCapacity - how large should we like to grow the vector to - based on 2x requiredVectorLength.

    unsigned length = storage->m_length;
    unsigned usedVectorLength = min(m_vectorLength, length);
    ASSERT(usedVectorLength <= MAX_STORAGE_VECTOR_LENGTH);
    // Check that required vector length is possible, in an overflow-safe fashion.
    if (count > MAX_STORAGE_VECTOR_LENGTH - usedVectorLength)
1025
        return false;
1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091
    unsigned requiredVectorLength = usedVectorLength + count;
    ASSERT(requiredVectorLength <= MAX_STORAGE_VECTOR_LENGTH);
    // The sum of m_vectorLength and m_indexBias will never exceed MAX_STORAGE_VECTOR_LENGTH.
    ASSERT(m_vectorLength <= MAX_STORAGE_VECTOR_LENGTH && (MAX_STORAGE_VECTOR_LENGTH - m_vectorLength) >= m_indexBias);
    unsigned currentCapacity = m_vectorLength + m_indexBias;
    // The calculation of desiredCapacity won't overflow, due to the range of MAX_STORAGE_VECTOR_LENGTH.
    unsigned desiredCapacity = min(MAX_STORAGE_VECTOR_LENGTH, max(BASE_VECTOR_LEN, requiredVectorLength) << 1);

    // Step 2:
    // We're either going to choose to allocate a new ArrayStorage, or we're going to reuse the existing on.

    void* newAllocBase;
    unsigned newStorageCapacity;
    // If the current storage array is sufficiently large (but not too large!) then just keep using it.
    if (currentCapacity > desiredCapacity && isDenseEnoughForVector(currentCapacity, requiredVectorLength)) {
        newAllocBase = storage->m_allocBase;
        newStorageCapacity = currentCapacity;
    } else {
        if (!tryFastMalloc(storageSize(desiredCapacity)).getValue(newAllocBase))
            return false;
        newStorageCapacity = desiredCapacity;
        // Currently there is no way to report to the heap that the extra capacity is shrinking!
        if (desiredCapacity > currentCapacity)
            Heap::heap(this)->reportExtraMemoryCost((desiredCapacity - currentCapacity) * sizeof(WriteBarrier<Unknown>));
    }

    // Step 3:
    // Work out where we're going to move things to.

    // Determine how much of the vector to use as pre-capacity, and how much as post-capacity.
    // If the vector had no free post-capacity (length >= m_vectorLength), don't give it any.
    // If it did, we calculate the amount that will remain based on an atomic decay - leave the
    // vector with half the post-capacity it had previously.
    unsigned postCapacity = 0;
    if (length < m_vectorLength) {
        // Atomic decay, + the post-capacity cannot be greater than what is available.
        postCapacity = min((m_vectorLength - length) >> 1, newStorageCapacity - requiredVectorLength);
        // If we're moving contents within the same allocation, the post-capacity is being reduced.
        ASSERT(newAllocBase != storage->m_allocBase || postCapacity < m_vectorLength - length);
    }

    m_vectorLength = requiredVectorLength + postCapacity;
    m_indexBias = newStorageCapacity - m_vectorLength;
    m_storage = reinterpret_cast_ptr<ArrayStorage*>(reinterpret_cast<WriteBarrier<Unknown>*>(newAllocBase) + m_indexBias);

    // Step 4:
    // Copy array data / header into their new locations, clear post-capacity & free any old allocation.

    // If this is being moved within the existing buffer of memory, we are always shifting data
    // to the right (since count > m_indexBias). As such this memmove cannot trample the header.
    memmove(m_storage->m_vector + count, storage->m_vector, sizeof(WriteBarrier<Unknown>) * usedVectorLength);
    memmove(m_storage, storage, storageSize(0));

    // Are we copying into a new allocation?
    if (newAllocBase != m_storage->m_allocBase) {
        // Free the old allocation, update m_allocBase.
        fastFree(m_storage->m_allocBase);
        m_storage->m_allocBase = newAllocBase;

        // We need to clear any entries in the vector beyond length. We only need to
        // do this if this was a new allocation, because if we're using an existing
        // allocation the post-capacity will already be cleared, and in an existing
        // allocation we can only beshrinking the amount of post capacity.
        for (unsigned i = requiredVectorLength; i < m_vectorLength; ++i)
            m_storage->m_vector[i].clear();
    }
1092

ap@webkit.org's avatar
ap@webkit.org committed
1093
    return true;
darin's avatar
darin committed
1094 1095
}

1096
bool JSArray::setLength(ExecState* exec, unsigned newLength, bool throwException)
darin's avatar
darin committed
1097
{
1098 1099
    checkConsistency();

1100
    ArrayStorage* storage = m_storage;
1101
    unsigned length = storage->m_length;
darin's avatar
darin committed
1102

1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116
    // If the length is read only then we enter sparse mode, so should enter the following 'if'.
    ASSERT(isLengthWritable() || storage->m_sparseValueMap);

    if (SparseArrayValueMap* map = storage->m_sparseValueMap) {
        // Fail if the length is not writable.
        if (map->lengthIsReadOnly())
            return reject(exec, throwException, StrictModeReadonlyPropertyWriteError);

        if (newLength < length) {
            // Copy any keys we might be interested in into a vector.
            Vector<unsigned> keys;
            keys.reserveCapacity(min(map->size(), static_cast<size_t>(length - newLength)));
            SparseArrayValueMap::const_iterator end = map->end();
            for (SparseArrayValueMap::const_iterator it = map->begin(); it != end; ++it) {
1117
                unsigned index = static_cast<unsigned>(it->first);
1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148
                if (index < length && index >= newLength)
                    keys.append(index);
            }

            // Check if the array is in sparse mode. If so there may be non-configurable
            // properties, so we have to perform deletion with caution, if not we can
            // delete values in any order.
            if (map->sparseMode()) {
                qsort(keys.begin(), keys.size(), sizeof(unsigned), compareKeysForQSort);
                unsigned i = keys.size();
                while (i) {
                    unsigned index = keys[--i];
                    SparseArrayValueMap::iterator it = map->find(index);
                    ASSERT(it != map->notFound());
                    if (it->second.attributes & DontDelete) {
                        storage->m_length = index + 1;
                        return reject(exec, throwException, "Unable to delete property.");
                    }
                    map->remove(it);
                }
            } else {
                for (unsigned i = 0; i < keys.size(); ++i)
                    map->remove(keys[i]);
                if (map->isEmpty()) {
                    delete map;
                    storage->m_sparseValueMap = 0;
                }
            }
        }
    }

darin's avatar
darin committed
1149
    if (newLength < length) {
1150
        // Delete properties from the vector.
1151
        unsigned usedVectorLength = min(length, m_vectorLength);
darin's avatar
darin committed
1152
        for (unsigned i = newLength; i < usedVectorLength; ++i) {
1153
            WriteBarrier<Unknown>& valueSlot = storage->m_vector[i];
darin's avatar
darin committed
1154
            bool hadValue = valueSlot;
1155
            valueSlot.clear();
darin's avatar
darin committed
1156 1157 1158
            storage->m_numValuesInVector -= hadValue;
        }
    }
aroben@apple.com's avatar
aroben@apple.com committed
1159

1160
    storage->m_length = newLength;
1161 1162

    checkConsistency();
1163
    return true;
darin's avatar
darin committed
1164 1165
}

1166
JSValue JSArray::pop(ExecState* exec)
1167 1168 1169
{
    checkConsistency();

1170
    ArrayStorage* storage = m_storage;
1171 1172
    
    unsigned length = storage->m_length;
1173 1174 1175
    if (!length) {
        if (!isLengthWritable())
            throwTypeError(exec, StrictModeReadonlyPropertyWriteError);
1176
        return jsUndefined();
1177
    }
1178 1179 1180

    --length;

ggaren@apple.com's avatar
ggaren@apple.com committed
1181
    JSValue result;
1182

1183
    if (length < m_vectorLength) {
1184
        WriteBarrier<Unknown>& valueSlot = storage->m_vector[length];
1185
        if (valueSlot) {
1186
            --storage->m_numValuesInVector;
1187 1188
            result = valueSlot.get();
            valueSlot.clear();
1189
        } else
1190 1191 1192
            result = jsUndefined();
    } else {
        result = jsUndefined();
1193
        if (SparseArrayValueMap* map = storage->m_sparseValueMap) {
1194
            SparseArrayValueMap::iterator it = map->find(length);
1195
            if (it != map->notFound()) {
1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207
                unsigned attributes = it->second.attributes;

                result = it->second.get(exec, this);
                if (exec->hadException())
                    return jsUndefined();
                
                if (attributes & DontDelete) {
                    throwError(exec, createTypeError(exec, "Unable to delete property."));
                    checkConsistency();
                    return result;
                }
                
1208
                map->remove(it);
1209
                if (map->isEmpty() && !map->sparseMode()) {
1210
                    delete map;
barraclough@apple.com's avatar