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jsarray.cpp
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jsarray.cpp
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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sts=4 et sw=4 tw=99:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "jsarrayinlines.h"
#include "mozilla/ArrayUtils.h"
#include "mozilla/CheckedInt.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/FloatingPoint.h"
#include "mozilla/MathAlgorithms.h"
#include <algorithm>
#include "jsapi.h"
#include "jsatom.h"
#include "jscntxt.h"
#include "jsfriendapi.h"
#include "jsfun.h"
#include "jsiter.h"
#include "jsnum.h"
#include "jsobj.h"
#include "jstypes.h"
#include "jsutil.h"
#include "ds/Sort.h"
#include "gc/Heap.h"
#include "jit/InlinableNatives.h"
#include "js/Class.h"
#include "js/Conversions.h"
#include "vm/ArgumentsObject.h"
#include "vm/Interpreter.h"
#include "vm/SelfHosting.h"
#include "vm/Shape.h"
#include "vm/StringBuffer.h"
#include "vm/TypedArrayObject.h"
#include "vm/WrapperObject.h"
#include "jsatominlines.h"
#include "vm/ArgumentsObject-inl.h"
#include "vm/ArrayObject-inl.h"
#include "vm/Caches-inl.h"
#include "vm/GeckoProfiler-inl.h"
#include "vm/Interpreter-inl.h"
#include "vm/NativeObject-inl.h"
#include "vm/UnboxedObject-inl.h"
using namespace js;
using namespace js::gc;
using mozilla::Abs;
using mozilla::ArrayLength;
using mozilla::CeilingLog2;
using mozilla::CheckedInt;
using mozilla::DebugOnly;
using mozilla::IsNaN;
using JS::AutoCheckCannotGC;
using JS::IsArrayAnswer;
using JS::ToUint32;
bool
JS::IsArray(JSContext* cx, HandleObject obj, IsArrayAnswer* answer)
{
if (obj->is<ArrayObject>()) {
*answer = IsArrayAnswer::Array;
return true;
}
if (obj->is<ProxyObject>())
return Proxy::isArray(cx, obj, answer);
*answer = IsArrayAnswer::NotArray;
return true;
}
bool
JS::IsArray(JSContext* cx, HandleObject obj, bool* isArray)
{
IsArrayAnswer answer;
if (!IsArray(cx, obj, &answer))
return false;
if (answer == IsArrayAnswer::RevokedProxy) {
JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_PROXY_REVOKED);
return false;
}
*isArray = answer == IsArrayAnswer::Array;
return true;
}
// ES2017 7.1.15 ToLength, but clamped to the [0,2^32-2] range.
static bool
ToLengthClamped(JSContext* cx, HandleValue v, uint32_t* out)
{
if (v.isInt32()) {
int32_t i = v.toInt32();
*out = i < 0 ? 0 : i;
return true;
}
double d;
if (v.isDouble()) {
d = v.toDouble();
} else {
if (!ToNumber(cx, v, &d))
return false;
}
d = JS::ToInteger(d);
if (d <= 0.0)
*out = 0;
else if (d < double(UINT32_MAX - 1))
*out = uint32_t(d);
else
*out = UINT32_MAX;
return true;
}
bool
js::GetLengthProperty(JSContext* cx, HandleObject obj, uint32_t* lengthp)
{
if (obj->is<ArrayObject>()) {
*lengthp = obj->as<ArrayObject>().length();
return true;
}
if (obj->is<ArgumentsObject>()) {
ArgumentsObject& argsobj = obj->as<ArgumentsObject>();
if (!argsobj.hasOverriddenLength()) {
*lengthp = argsobj.initialLength();
return true;
}
}
RootedValue value(cx);
if (!GetProperty(cx, obj, obj, cx->names().length, &value))
return false;
if (!ToLengthClamped(cx, value, lengthp))
return false;
return true;
}
// ES2017 7.1.15 ToLength.
static bool
ToLength(JSContext* cx, HandleValue v, uint64_t* out)
{
if (v.isInt32()) {
int32_t i = v.toInt32();
*out = i < 0 ? 0 : i;
return true;
}
double d;
if (v.isDouble()) {
d = v.toDouble();
} else {
if (!ToNumber(cx, v, &d))
return false;
}
d = JS::ToInteger(d);
if (d <= 0.0)
*out = 0;
else
*out = uint64_t(Min(d, DOUBLE_INTEGRAL_PRECISION_LIMIT - 1));
return true;
}
static bool
GetLengthProperty(JSContext* cx, HandleObject obj, uint64_t* lengthp)
{
if (obj->is<ArrayObject>()) {
*lengthp = obj->as<ArrayObject>().length();
return true;
}
if (obj->is<ArgumentsObject>()) {
ArgumentsObject& argsobj = obj->as<ArgumentsObject>();
if (!argsobj.hasOverriddenLength()) {
*lengthp = argsobj.initialLength();
return true;
}
}
RootedValue value(cx);
if (!GetProperty(cx, obj, obj, cx->names().length, &value))
return false;
return ToLength(cx, value, lengthp);
}
/*
* Determine if the id represents an array index.
*
* An id is an array index according to ECMA by (15.4):
*
* "Array objects give special treatment to a certain class of property names.
* A property name P (in the form of a string value) is an array index if and
* only if ToString(ToUint32(P)) is equal to P and ToUint32(P) is not equal
* to 2^32-1."
*
* This means the largest allowed index is actually 2^32-2 (4294967294).
*
* In our implementation, it would be sufficient to check for id.isInt32()
* except that by using signed 31-bit integers we miss the top half of the
* valid range. This function checks the string representation itself; note
* that calling a standard conversion routine might allow strings such as
* "08" or "4.0" as array indices, which they are not.
*
*/
template <typename CharT>
static bool
StringIsArrayIndex(const CharT* s, uint32_t length, uint32_t* indexp)
{
const CharT* end = s + length;
if (length == 0 || length > (sizeof("4294967294") - 1) || !JS7_ISDEC(*s))
return false;
uint32_t c = 0, previous = 0;
uint32_t index = JS7_UNDEC(*s++);
/* Don't allow leading zeros. */
if (index == 0 && s != end)
return false;
for (; s < end; s++) {
if (!JS7_ISDEC(*s))
return false;
previous = index;
c = JS7_UNDEC(*s);
index = 10 * index + c;
}
/* Make sure we didn't overflow. */
if (previous < (MAX_ARRAY_INDEX / 10) || (previous == (MAX_ARRAY_INDEX / 10) &&
c <= (MAX_ARRAY_INDEX % 10))) {
MOZ_ASSERT(index <= MAX_ARRAY_INDEX);
*indexp = index;
return true;
}
return false;
}
JS_FRIEND_API(bool)
js::StringIsArrayIndex(JSLinearString* str, uint32_t* indexp)
{
AutoCheckCannotGC nogc;
return str->hasLatin1Chars()
? ::StringIsArrayIndex(str->latin1Chars(nogc), str->length(), indexp)
: ::StringIsArrayIndex(str->twoByteChars(nogc), str->length(), indexp);
}
template <typename T>
static bool
ToId(JSContext* cx, T index, MutableHandleId id);
template <>
bool
ToId(JSContext* cx, uint32_t index, MutableHandleId id)
{
return IndexToId(cx, index, id);
}
template <>
bool
ToId(JSContext* cx, uint64_t index, MutableHandleId id)
{
MOZ_ASSERT(index < uint64_t(DOUBLE_INTEGRAL_PRECISION_LIMIT));
if (index == uint32_t(index))
return IndexToId(cx, uint32_t(index), id);
Value tmp = DoubleValue(index);
return ValueToId<CanGC>(cx, HandleValue::fromMarkedLocation(&tmp), id);
}
/*
* If the property at the given index exists, get its value into |vp| and set
* |*hole| to false. Otherwise set |*hole| to true and |vp| to Undefined.
*/
template <typename T>
static bool
HasAndGetElement(JSContext* cx, HandleObject obj, HandleObject receiver, T index, bool* hole,
MutableHandleValue vp)
{
if (obj->isNative()) {
NativeObject* nobj = &obj->as<NativeObject>();
if (index < nobj->getDenseInitializedLength()) {
vp.set(nobj->getDenseElement(size_t(index)));
if (!vp.isMagic(JS_ELEMENTS_HOLE)) {
*hole = false;
return true;
}
}
if (nobj->is<ArgumentsObject>() && index <= UINT32_MAX) {
if (nobj->as<ArgumentsObject>().maybeGetElement(uint32_t(index), vp)) {
*hole = false;
return true;
}
}
}
RootedId id(cx);
if (!ToId(cx, index, &id))
return false;
bool found;
if (!HasProperty(cx, obj, id, &found))
return false;
if (found) {
if (!GetProperty(cx, obj, receiver, id, vp))
return false;
} else {
vp.setUndefined();
}
*hole = !found;
return true;
}
template <typename T>
static inline bool
HasAndGetElement(JSContext* cx, HandleObject obj, T index, bool* hole, MutableHandleValue vp)
{
return HasAndGetElement(cx, obj, obj, index, hole, vp);
}
bool
ElementAdder::append(JSContext* cx, HandleValue v)
{
MOZ_ASSERT(index_ < length_);
if (resObj_) {
NativeObject* resObj = &resObj_->as<NativeObject>();
DenseElementResult result = resObj->setOrExtendDenseElements(cx, index_, v.address(), 1);
if (result == DenseElementResult::Failure)
return false;
if (result == DenseElementResult::Incomplete) {
if (!DefineDataElement(cx, resObj_, index_, v))
return false;
}
} else {
vp_[index_] = v;
}
index_++;
return true;
}
void
ElementAdder::appendHole()
{
MOZ_ASSERT(getBehavior_ == ElementAdder::CheckHasElemPreserveHoles);
MOZ_ASSERT(index_ < length_);
if (!resObj_)
vp_[index_].setMagic(JS_ELEMENTS_HOLE);
index_++;
}
bool
js::GetElementsWithAdder(JSContext* cx, HandleObject obj, HandleObject receiver,
uint32_t begin, uint32_t end, ElementAdder* adder)
{
MOZ_ASSERT(begin <= end);
RootedValue val(cx);
for (uint32_t i = begin; i < end; i++) {
if (adder->getBehavior() == ElementAdder::CheckHasElemPreserveHoles) {
bool hole;
if (!HasAndGetElement(cx, obj, receiver, i, &hole, &val))
return false;
if (hole) {
adder->appendHole();
continue;
}
} else {
MOZ_ASSERT(adder->getBehavior() == ElementAdder::GetElement);
if (!GetElement(cx, obj, receiver, i, &val))
return false;
}
if (!adder->append(cx, val))
return false;
}
return true;
}
static bool
ObjectMayHaveExtraIndexedProperties(JSObject* obj);
static inline bool
IsPackedArrayOrNoExtraIndexedProperties(JSObject* obj, uint64_t length)
{
return (IsPackedArray(obj) && obj->as<ArrayObject>().length() == length) ||
!ObjectMayHaveExtraIndexedProperties(obj);
}
static bool
GetDenseElements(NativeObject* aobj, uint32_t length, Value* vp)
{
MOZ_ASSERT(IsPackedArrayOrNoExtraIndexedProperties(aobj, length));
if (length > aobj->getDenseInitializedLength())
return false;
for (size_t i = 0; i < length; i++) {
vp[i] = aobj->getDenseElement(i);
// No other indexed properties so hole => undefined.
if (vp[i].isMagic(JS_ELEMENTS_HOLE))
vp[i] = UndefinedValue();
}
return true;
}
bool
js::GetElements(JSContext* cx, HandleObject aobj, uint32_t length, Value* vp)
{
if (IsPackedArrayOrNoExtraIndexedProperties(aobj, length)) {
if (GetDenseElements(&aobj->as<NativeObject>(), length, vp))
return true;
}
if (aobj->is<ArgumentsObject>()) {
ArgumentsObject& argsobj = aobj->as<ArgumentsObject>();
if (!argsobj.hasOverriddenLength()) {
if (argsobj.maybeGetElements(0, length, vp))
return true;
}
}
if (aobj->is<TypedArrayObject>()) {
TypedArrayObject* typedArray = &aobj->as<TypedArrayObject>();
if (typedArray->length() == length) {
typedArray->getElements(vp);
return true;
}
}
if (js::GetElementsOp op = aobj->getOpsGetElements()) {
ElementAdder adder(cx, vp, length, ElementAdder::GetElement);
return op(cx, aobj, 0, length, &adder);
}
for (uint32_t i = 0; i < length; i++) {
if (!GetElement(cx, aobj, aobj, i, MutableHandleValue::fromMarkedLocation(&vp[i])))
return false;
}
return true;
}
static inline bool
GetArrayElement(JSContext* cx, HandleObject obj, uint64_t index, MutableHandleValue vp)
{
if (obj->isNative()) {
NativeObject* nobj = &obj->as<NativeObject>();
if (index < nobj->getDenseInitializedLength()) {
vp.set(nobj->getDenseElement(size_t(index)));
if (!vp.isMagic(JS_ELEMENTS_HOLE))
return true;
}
if (nobj->is<ArgumentsObject>() && index <= UINT32_MAX) {
if (nobj->as<ArgumentsObject>().maybeGetElement(uint32_t(index), vp))
return true;
}
}
RootedId id(cx);
if (!ToId(cx, index, &id))
return false;
return GetProperty(cx, obj, obj, id, vp);
}
static inline bool
DefineArrayElement(JSContext* cx, HandleObject obj, uint64_t index, HandleValue value)
{
RootedId id(cx);
if (!ToId(cx, index, &id))
return false;
return DefineDataProperty(cx, obj, id, value);
}
// Set the value of the property at the given index to v.
static inline bool
SetArrayElement(JSContext* cx, HandleObject obj, uint64_t index, HandleValue v)
{
RootedId id(cx);
if (!ToId(cx, index, &id))
return false;
return SetProperty(cx, obj, id, v);
}
/*
* Attempt to delete the element |index| from |obj| as if by
* |obj.[[Delete]](index)|.
*
* If an error occurs while attempting to delete the element (that is, the call
* to [[Delete]] threw), return false.
*
* Otherwise call result.succeed() or result.fail() to indicate whether the
* deletion attempt succeeded (that is, whether the call to [[Delete]] returned
* true or false). (Deletes generally fail only when the property is
* non-configurable, but proxies may implement different semantics.)
*/
static bool
DeleteArrayElement(JSContext* cx, HandleObject obj, uint64_t index, ObjectOpResult& result)
{
if (obj->is<ArrayObject>() &&
!obj->as<NativeObject>().isIndexed() &&
!obj->as<NativeObject>().denseElementsAreFrozen())
{
ArrayObject* aobj = &obj->as<ArrayObject>();
if (index <= UINT32_MAX) {
uint32_t idx = uint32_t(index);
if (idx < aobj->getDenseInitializedLength()) {
if (!aobj->maybeCopyElementsForWrite(cx))
return false;
if (idx+1 == aobj->getDenseInitializedLength()) {
aobj->setDenseInitializedLength(idx);
} else {
aobj->markDenseElementsNotPacked(cx);
aobj->setDenseElement(idx, MagicValue(JS_ELEMENTS_HOLE));
}
if (!SuppressDeletedElement(cx, obj, idx))
return false;
}
}
return result.succeed();
}
RootedId id(cx);
if (!ToId(cx, index, &id))
return false;
return DeleteProperty(cx, obj, id, result);
}
/* ES6 draft rev 32 (2 Febr 2015) 7.3.7 */
static bool
DeletePropertyOrThrow(JSContext* cx, HandleObject obj, uint64_t index)
{
ObjectOpResult success;
if (!DeleteArrayElement(cx, obj, index, success))
return false;
if (!success) {
RootedId id(cx);
if (!ToId(cx, index, &id))
return false;
return success.reportError(cx, obj, id);
}
return true;
}
static bool
DeletePropertiesOrThrow(JSContext* cx, HandleObject obj, uint64_t len, uint64_t finalLength)
{
if (obj->is<ArrayObject>() &&
!obj->as<NativeObject>().isIndexed() &&
!obj->as<NativeObject>().denseElementsAreFrozen())
{
if (len <= UINT32_MAX) {
// Skip forward to the initialized elements of this array.
len = Min(uint32_t(len), obj->as<ArrayObject>().getDenseInitializedLength());
}
}
for (uint64_t k = len; k > finalLength; k--) {
if (!CheckForInterrupt(cx))
return false;
if (!DeletePropertyOrThrow(cx, obj, k - 1))
return false;
}
return true;
}
static bool
SetArrayLengthProperty(JSContext* cx, HandleArrayObject obj, HandleValue value)
{
RootedId id(cx, NameToId(cx->names().length));
ObjectOpResult result;
if (obj->lengthIsWritable()) {
if (!ArraySetLength(cx, obj, id, JSPROP_PERMANENT, value, result))
return false;
} else {
MOZ_ALWAYS_TRUE(result.fail(JSMSG_READ_ONLY));
}
return result.checkStrict(cx, obj, id);
}
static bool
SetLengthProperty(JSContext* cx, HandleObject obj, uint64_t length)
{
MOZ_ASSERT(length < uint64_t(DOUBLE_INTEGRAL_PRECISION_LIMIT));
RootedValue v(cx, NumberValue(length));
if (obj->is<ArrayObject>())
return SetArrayLengthProperty(cx, obj.as<ArrayObject>(), v);
return SetProperty(cx, obj, cx->names().length, v);
}
bool
js::SetLengthProperty(JSContext* cx, HandleObject obj, uint32_t length)
{
RootedValue v(cx, NumberValue(length));
if (obj->is<ArrayObject>())
return SetArrayLengthProperty(cx, obj.as<ArrayObject>(), v);
return SetProperty(cx, obj, cx->names().length, v);
}
static bool
array_length_getter(JSContext* cx, HandleObject obj, HandleId id, MutableHandleValue vp)
{
vp.setNumber(obj->as<ArrayObject>().length());
return true;
}
static bool
array_length_setter(JSContext* cx, HandleObject obj, HandleId id, HandleValue v,
ObjectOpResult& result)
{
MOZ_ASSERT(id == NameToId(cx->names().length));
if (!obj->is<ArrayObject>()) {
// This array .length property was found on the prototype
// chain. Ideally the setter should not have been called, but since
// we're here, do an impression of SetPropertyByDefining.
return DefineDataProperty(cx, obj, id, v, JSPROP_ENUMERATE, result);
}
HandleArrayObject arr = obj.as<ArrayObject>();
MOZ_ASSERT(arr->lengthIsWritable(),
"setter shouldn't be called if property is non-writable");
return ArraySetLength(cx, arr, id, JSPROP_PERMANENT, v, result);
}
struct ReverseIndexComparator
{
bool operator()(const uint32_t& a, const uint32_t& b, bool* lessOrEqualp) {
MOZ_ASSERT(a != b, "how'd we get duplicate indexes?");
*lessOrEqualp = b <= a;
return true;
}
};
static bool
MaybeInIteration(HandleObject obj, JSContext* cx)
{
/*
* Don't optimize if the array might be in the midst of iteration. We
* rely on this to be able to safely move dense array elements around with
* just a memmove (see NativeObject::moveDenseArrayElements), without worrying
* about updating any in-progress enumerators for properties implicitly
* deleted if a hole is moved from one location to another location not yet
* visited. See bug 690622.
*
* Note that it's fine to optimize if |obj| is on the prototype of another
* object: SuppressDeletedProperty only suppresses properties deleted from
* the iterated object itself.
*/
if (MOZ_LIKELY(!cx->compartment()->objectMaybeInIteration(obj)))
return false;
ObjectGroup* group = JSObject::getGroup(cx, obj);
if (MOZ_UNLIKELY(!group)) {
cx->recoverFromOutOfMemory();
return true;
}
if (MOZ_UNLIKELY(group->hasAllFlags(OBJECT_FLAG_ITERATED)))
return true;
return false;
}
/* ES6 draft rev 34 (2015 Feb 20) 9.4.2.4 ArraySetLength */
bool
js::ArraySetLength(JSContext* cx, Handle<ArrayObject*> arr, HandleId id,
unsigned attrs, HandleValue value, ObjectOpResult& result)
{
MOZ_ASSERT(id == NameToId(cx->names().length));
if (!arr->maybeCopyElementsForWrite(cx))
return false;
// Step 1.
uint32_t newLen;
if (attrs & JSPROP_IGNORE_VALUE) {
MOZ_ASSERT(value.isUndefined());
// The spec has us calling OrdinaryDefineOwnProperty if
// Desc.[[Value]] is absent, but our implementation is so different that
// this is impossible. Instead, set newLen to the current length and
// proceed to step 9.
newLen = arr->length();
} else {
// Step 2 is irrelevant in our implementation.
// Step 3.
if (!ToUint32(cx, value, &newLen))
return false;
// Step 4.
double d;
if (!ToNumber(cx, value, &d))
return false;
// Step 5.
if (d != newLen) {
JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_BAD_ARRAY_LENGTH);
return false;
}
// Steps 6-8 are irrelevant in our implementation.
}
// Steps 9-11.
bool lengthIsWritable = arr->lengthIsWritable();
#ifdef DEBUG
{
RootedShape lengthShape(cx, arr->lookupPure(id));
MOZ_ASSERT(lengthShape);
MOZ_ASSERT(lengthShape->writable() == lengthIsWritable);
}
#endif
uint32_t oldLen = arr->length();
// Part of steps 1.a, 12.a, and 16: Fail if we're being asked to change
// enumerability or configurability, or otherwise break the object
// invariants. (ES6 checks these by calling OrdinaryDefineOwnProperty, but
// in SM, the array length property is hardly ordinary.)
if ((attrs & (JSPROP_PERMANENT | JSPROP_IGNORE_PERMANENT)) == 0 ||
(attrs & (JSPROP_ENUMERATE | JSPROP_IGNORE_ENUMERATE)) == JSPROP_ENUMERATE ||
(attrs & (JSPROP_GETTER | JSPROP_SETTER)) != 0 ||
(!lengthIsWritable && (attrs & (JSPROP_READONLY | JSPROP_IGNORE_READONLY)) == 0))
{
return result.fail(JSMSG_CANT_REDEFINE_PROP);
}
// Steps 12-13 for arrays with non-writable length.
if (!lengthIsWritable) {
if (newLen == oldLen)
return result.succeed();
return result.fail(JSMSG_CANT_REDEFINE_ARRAY_LENGTH);
}
// Step 19.
bool succeeded = true;
do {
// The initialized length and capacity of an array only need updating
// when non-hole elements are added or removed, which doesn't happen
// when array length stays the same or increases.
if (newLen >= oldLen)
break;
// Attempt to propagate dense-element optimization tricks, if possible,
// and avoid the generic (and accordingly slow) deletion code below.
// We can only do this if there are only densely-indexed elements.
// Once there's a sparse indexed element, there's no good way to know,
// save by enumerating all the properties to find it. But we *have* to
// know in case that sparse indexed element is non-configurable, as
// that element must prevent any deletions below it. Bug 586842 should
// fix this inefficiency by moving indexed storage to be entirely
// separate from non-indexed storage.
// A second reason for this optimization to be invalid is an active
// for..in iteration over the array. Keys deleted before being reached
// during the iteration must not be visited, and suppressing them here
// would be too costly.
if (!arr->isIndexed() && !MaybeInIteration(arr, cx)) {
if (!arr->maybeCopyElementsForWrite(cx))
return false;
uint32_t oldCapacity = arr->getDenseCapacity();
uint32_t oldInitializedLength = arr->getDenseInitializedLength();
MOZ_ASSERT(oldCapacity >= oldInitializedLength);
if (oldInitializedLength > newLen)
arr->setDenseInitializedLength(newLen);
if (oldCapacity > newLen)
arr->shrinkElements(cx, newLen);
// We've done the work of deleting any dense elements needing
// deletion, and there are no sparse elements. Thus we can skip
// straight to defining the length.
break;
}
// Step 15.
//
// Attempt to delete all elements above the new length, from greatest
// to least. If any of these deletions fails, we're supposed to define
// the length to one greater than the index that couldn't be deleted,
// *with the property attributes specified*. This might convert the
// length to be not the value specified, yet non-writable. (You may be
// forgiven for thinking these are interesting semantics.) Example:
//
// var arr =
// Object.defineProperty([0, 1, 2, 3], 1, { writable: false });
// Object.defineProperty(arr, "length",
// { value: 0, writable: false });
//
// will convert |arr| to an array of non-writable length two, then
// throw a TypeError.
//
// We implement this behavior, in the relevant lops below, by setting
// |succeeded| to false. Then we exit the loop, define the length
// appropriately, and only then throw a TypeError, if necessary.
uint32_t gap = oldLen - newLen;
const uint32_t RemoveElementsFastLimit = 1 << 24;
if (gap < RemoveElementsFastLimit) {
// If we're removing a relatively small number of elements, just do
// it exactly by the spec.
while (newLen < oldLen) {
// Step 15a.
oldLen--;
// Steps 15b-d.
ObjectOpResult deleteSucceeded;
if (!DeleteElement(cx, arr, oldLen, deleteSucceeded))
return false;
if (!deleteSucceeded) {
newLen = oldLen + 1;
succeeded = false;
break;
}
}
} else {
// If we're removing a large number of elements from an array
// that's probably sparse, try a different tack. Get all the own
// property names, sift out the indexes in the deletion range into
// a vector, sort the vector greatest to least, then delete the
// indexes greatest to least using that vector. See bug 322135.
//
// This heuristic's kind of a huge guess -- "large number of
// elements" and "probably sparse" are completely unprincipled
// predictions. In the long run, bug 586842 will support the right
// fix: store sparse elements in a sorted data structure that
// permits fast in-reverse-order traversal and concurrent removals.
Vector<uint32_t> indexes(cx);
{
AutoIdVector props(cx);
if (!GetPropertyKeys(cx, arr, JSITER_OWNONLY | JSITER_HIDDEN, &props))
return false;
for (size_t i = 0; i < props.length(); i++) {
if (!CheckForInterrupt(cx))
return false;
uint32_t index;
if (!IdIsIndex(props[i], &index))
continue;
if (index >= newLen && index < oldLen) {
if (!indexes.append(index))
return false;
}
}
}
uint32_t count = indexes.length();
{
// We should use radix sort to be O(n), but this is uncommon
// enough that we'll punt til someone complains.
Vector<uint32_t> scratch(cx);
if (!scratch.resize(count))
return false;
MOZ_ALWAYS_TRUE(MergeSort(indexes.begin(), count, scratch.begin(),
ReverseIndexComparator()));
}
uint32_t index = UINT32_MAX;
for (uint32_t i = 0; i < count; i++) {
MOZ_ASSERT(indexes[i] < index, "indexes should never repeat");
index = indexes[i];
// Steps 15b-d.
ObjectOpResult deleteSucceeded;
if (!DeleteElement(cx, arr, index, deleteSucceeded))
return false;
if (!deleteSucceeded) {
newLen = index + 1;
succeeded = false;
break;
}
}
}
} while (false);
// Update array length. Technically we should have been doing this
// throughout the loop, in step 19.d.iii.
arr->setLength(cx, newLen);
// Step 20.
if (attrs & JSPROP_READONLY) {
// Yes, we totally drop a non-stub getter/setter from a defineProperty
// API call on the floor here. Given that getter/setter will go away in
// the long run, with accessors replacing them both internally and at the
// API level, just run with this.
RootedShape lengthShape(cx, arr->lookup(cx, id));
if (!NativeObject::changeProperty(cx, arr, lengthShape,
lengthShape->attributes() | JSPROP_READONLY,
array_length_getter, array_length_setter))
{
return false;
}
}
// All operations past here until the |!succeeded| code must be infallible,
// so that all element fields remain properly synchronized.
// Trim the initialized length, if needed, to preserve the <= length
// invariant. (Capacity was already reduced during element deletion, if
// necessary.)
ObjectElements* header = arr->getElementsHeader();
header->initializedLength = Min(header->initializedLength, newLen);
if (attrs & JSPROP_READONLY)
arr->setNonWritableLength(cx);
if (!succeeded)
return result.fail(JSMSG_CANT_TRUNCATE_ARRAY);
return result.succeed();
}
bool
js::WouldDefinePastNonwritableLength(HandleNativeObject obj, uint32_t index)
{
if (!obj->is<ArrayObject>())
return false;
ArrayObject* arr = &obj->as<ArrayObject>();
return !arr->lengthIsWritable() && index >= arr->length();
}
static bool
array_addProperty(JSContext* cx, HandleObject obj, HandleId id, HandleValue v)
{
ArrayObject* arr = &obj->as<ArrayObject>();
uint32_t index;
if (!IdIsIndex(id, &index))
return true;
uint32_t length = arr->length();
if (index >= length) {
MOZ_ASSERT(arr->lengthIsWritable(),
"how'd this element get added if length is non-writable?");
arr->setLength(cx, index + 1);
}
return true;
}
static inline bool
ObjectMayHaveExtraIndexedOwnProperties(JSObject* obj)
{
if (!obj->isNative())
return true;
if (obj->as<NativeObject>().isIndexed())
return true;
if (obj->is<TypedArrayObject>())
return true;
return ClassMayResolveId(*obj->runtimeFromAnyThread()->commonNames,
obj->getClass(), INT_TO_JSID(0), obj);
}
/*
* Whether obj may have indexed properties anywhere besides its dense
* elements. This includes other indexed properties in its shape hierarchy, and
* indexed properties or elements along its prototype chain.
*/
static bool
ObjectMayHaveExtraIndexedProperties(JSObject* obj)
{
MOZ_ASSERT_IF(obj->hasDynamicPrototype(), !obj->isNative());
if (ObjectMayHaveExtraIndexedOwnProperties(obj))
return true;
do {
MOZ_ASSERT(obj->hasStaticPrototype(),
"dynamic-prototype objects must be non-native, ergo must "
"have failed ObjectMayHaveExtraIndexedOwnProperties");