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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* 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
#ifndef vm_NativeObject_h
#define vm_NativeObject_h
#include "mozilla/Assertions.h"
#include "mozilla/Attributes.h"
#include "mozilla/Maybe.h"
#include <algorithm>
#include <stdint.h>
#include "NamespaceImports.h"
#include "gc/Barrier.h"
#include "gc/MaybeRooted.h"
#include "gc/ZoneAllocator.h"
#include "js/shadow/Object.h" // JS::shadow::Object
#include "js/shadow/Zone.h" // JS::shadow::Zone
#include "js/Value.h"
#include "vm/GetterSetter.h"
#include "vm/JSAtomUtils.h" // AtomIsMarked
#include "vm/JSObject.h"
#include "vm/Shape.h"
#include "vm/StringType.h"
namespace js {
class JS_PUBLIC_API GenericPrinter;
class PropertyResult;
namespace gc {
class TenuringTracer;
} // namespace gc
#ifdef ENABLE_RECORD_TUPLE
// Defined in vm/RecordTupleShared.{h,cpp}. We cannot include that file
// because it causes circular dependencies.
extern bool IsExtendedPrimitiveWrapper(const JSObject& obj);
#endif
/*
* To really poison a set of values, using 'magic' or 'undefined' isn't good
* in debug builds and crash in release builds. Instead, we use a safe-for-crash
* pointer.
*/
static MOZ_ALWAYS_INLINE void Debug_SetValueRangeToCrashOnTouch(Value* beg,
Value* end) {
#ifdef DEBUG
for (Value* v = beg; v != end; ++v) {
*v = js::PoisonedObjectValue(0x48);
}
#endif
}
static MOZ_ALWAYS_INLINE void Debug_SetValueRangeToCrashOnTouch(Value* vec,
size_t len) {
#ifdef DEBUG
Debug_SetValueRangeToCrashOnTouch(vec, vec + len);
#endif
}
static MOZ_ALWAYS_INLINE void Debug_SetValueRangeToCrashOnTouch(
GCPtr<Value>* vec, size_t len) {
#ifdef DEBUG
Debug_SetValueRangeToCrashOnTouch((Value*)vec, len);
#endif
}
static MOZ_ALWAYS_INLINE void Debug_SetSlotRangeToCrashOnTouch(HeapSlot* vec,
uint32_t len) {
#ifdef DEBUG
Debug_SetValueRangeToCrashOnTouch((Value*)vec, len);
#endif
}
static MOZ_ALWAYS_INLINE void Debug_SetSlotRangeToCrashOnTouch(HeapSlot* begin,
HeapSlot* end) {
#ifdef DEBUG
Debug_SetValueRangeToCrashOnTouch((Value*)begin, end - begin);
#endif
}
class ArrayObject;
/*
* ES6 20130308 draft 8.4.2.4 ArraySetLength.
*
* |id| must be "length", |desc| is the new non-accessor descriptor, and
* |result| receives an error code if the change is invalid.
*/
extern bool ArraySetLength(JSContext* cx, Handle<ArrayObject*> obj, HandleId id,
Handle<PropertyDescriptor> desc,
ObjectOpResult& result);
/*
* [SMDOC] NativeObject Elements layout
*
* Elements header used for native objects. The elements component of such
* objects offers an efficient representation for all or some of the indexed
* properties of the object, using a flat array of Values rather than a shape
* hierarchy stored in the object's slots. This structure is immediately
* followed by an array of elements, with the elements member in an object
* pointing to the beginning of that array (the end of this structure). See
* below for usage of this structure.
*
* The sets of properties represented by an object's elements and slots
* are disjoint. The elements contain only indexed properties, while the slots
* can contain both named and indexed properties; any indexes in the slots are
* distinct from those in the elements. If isIndexed() is false for an object,
* all indexed properties (if any) are stored in the dense elements.
*
* Indexes will be stored in the object's slots instead of its elements in
* the following case:
* - there are more than MIN_SPARSE_INDEX slots total and the load factor
* (COUNT / capacity) is less than 0.25
* - a property is defined that has non-default property attributes.
*
* We track these pieces of metadata for dense elements:
* - The length property as a uint32_t, accessible for array objects with
* ArrayObject::{length,setLength}(). This is unused for non-arrays.
* - The number of element slots (capacity), gettable with
* getDenseCapacity().
* - The array's initialized length, accessible with
* getDenseInitializedLength().
*
* Holes in the array are represented by MagicValue(JS_ELEMENTS_HOLE) values.
* These indicate indexes which are not dense properties of the array. The
* property may, however, be held by the object's properties.
*
* The capacity and length of an object's elements are almost entirely
* unrelated! In general the length may be greater than, less than, or equal
* to the capacity. The first case occurs with |new Array(100)|. The length
* is 100, but the capacity remains 0 (indices below length and above capacity
* must be treated as holes) until elements between capacity and length are
* set. The other two cases are common, depending upon the number of elements
* in an array and the underlying allocator used for element storage.
*
* The only case in which the capacity and length of an object's elements are
* related is when the object is an array with non-writable length. In this
* case the capacity is always less than or equal to the length. This permits
* JIT code to optimize away the check for non-writable length when assigning
* to possibly out-of-range elements: such code already has to check for
* |index < capacity|, and fallback code checks for non-writable length.
*
* The initialized length of an object specifies the number of elements that
* have been initialized. All elements above the initialized length are
* holes in the object, and the memory for all elements between the initialized
* length and capacity is left uninitialized. The initialized length is some
* value less than or equal to both the object's length and the object's
* capacity.
*
* There is flexibility in exactly the value the initialized length must hold,
* e.g. if an array has length 5, capacity 10, completely empty, it is valid
* for the initialized length to be any value between zero and 5, as long as
* the in memory values below the initialized length have been initialized with
* a hole value. However, in such cases we want to keep the initialized length
* as small as possible: if the object is known to have no hole values below
* its initialized length, then it is "packed" and can be accessed much faster
* by JIT code.
*
* Elements do not track property creation order, so enumerating the elements
* of an object does not necessarily visit indexes in the order they were
* created.
*
*
* [SMDOC] NativeObject shifted elements optimization
*
* Shifted elements
* ----------------
* It's pretty common to use an array as a queue, like this:
*
* while (arr.length > 0)
* foo(arr.shift());
*
* To ensure we don't get quadratic behavior on this, elements can be 'shifted'
* in memory. tryShiftDenseElements does this by incrementing elements_ to point
* to the next element and moving the ObjectElements header in memory (so it's
* stored where the shifted Value used to be).
*
* Shifted elements can be moved when we grow the array, when the array is
* made non-extensible (for simplicity, shifted elements are not supported on
* objects that are non-extensible, have copy-on-write elements, or on arrays
* with non-writable length).
*/
class ObjectElements {
public:
enum Flags : uint16_t {
// Elements are stored inline in the object allocation.
// An object allocated with the FIXED flag set can have the flag unset later
// if `growElements()` is called to increase the capacity beyond what was
// initially allocated. Once the flag is unset, it will remain so for the
// rest of the lifetime of the object.
FIXED = 0x1,
// Present only if these elements correspond to an array with
// non-writable length; never present for non-arrays.
NONWRITABLE_ARRAY_LENGTH = 0x2,
#ifdef ENABLE_RECORD_TUPLE
// Records, Tuples and Boxes must be atomized before being hashed. We store
// the "is atomized" flag here for tuples, and in fixed slots for records
// and boxes.
TUPLE_IS_ATOMIZED = 0x4,
#endif
// For TypedArrays only: this TypedArray's storage is mapping shared
// memory. This is a static property of the TypedArray, set when it
// is created and never changed.
SHARED_MEMORY = 0x8,
// These elements are not extensible. If this flag is set, the object's
// Shape must also have the NotExtensible flag. This exists on
// ObjectElements in addition to Shape to simplify JIT code.
NOT_EXTENSIBLE = 0x10,
// These elements are set to integrity level "sealed". If this flag is
// set, the NOT_EXTENSIBLE flag must be set as well.
SEALED = 0x20,
// These elements are set to integrity level "frozen". If this flag is
// set, the SEALED flag must be set as well.
//
// This flag must only be set if the Shape has the FrozenElements flag.
// The Shape flag ensures a shape guard can be used to guard against frozen
// elements. The ObjectElements flag is convenient for JIT code and
// ObjectElements assertions.
FROZEN = 0x40,
// If this flag is not set, the elements are guaranteed to contain no hole
// values (the JS_ELEMENTS_HOLE MagicValue) in [0, initializedLength).
NON_PACKED = 0x80,
// If this flag is not set, there's definitely no for-in iterator that
// covers these dense elements so elements can be deleted without calling
// SuppressDeletedProperty. This is used by fast paths for various Array
// builtins. See also NativeObject::denseElementsMaybeInIteration.
MAYBE_IN_ITERATION = 0x100,
};
// The flags word stores both the flags and the number of shifted elements.
// Allow shifting 2047 elements before actually moving the elements.
static const size_t NumShiftedElementsBits = 11;
static const size_t MaxShiftedElements = (1 << NumShiftedElementsBits) - 1;
static const size_t NumShiftedElementsShift = 32 - NumShiftedElementsBits;
static const size_t FlagsMask = (1 << NumShiftedElementsShift) - 1;
static_assert(MaxShiftedElements == 2047,
"MaxShiftedElements should match the comment");
private:
friend class ::JSObject;
friend class ArrayObject;
friend class NativeObject;
friend class gc::TenuringTracer;
#ifdef ENABLE_RECORD_TUPLE
friend class TupleType;
#endif
friend bool js::SetIntegrityLevel(JSContext* cx, HandleObject obj,
IntegrityLevel level);
friend bool ArraySetLength(JSContext* cx, Handle<ArrayObject*> obj,
HandleId id, Handle<PropertyDescriptor> desc,
ObjectOpResult& result);
// The NumShiftedElementsBits high bits of this are used to store the
// number of shifted elements, the other bits are available for the flags.
// See Flags enum above.
uint32_t flags;
/*
* Number of initialized elements. This is <= the capacity, and for arrays
* is <= the length. Memory for elements above the initialized length is
* uninitialized, but values between the initialized length and the proper
* length are conceptually holes.
*/
uint32_t initializedLength;
/* Number of allocated slots. */
uint32_t capacity;
/* 'length' property of array objects, unused for other objects. */
uint32_t length;
bool hasNonwritableArrayLength() const {
return flags & NONWRITABLE_ARRAY_LENGTH;
}
void setNonwritableArrayLength() {
// See ArrayObject::setNonWritableLength.
MOZ_ASSERT(capacity == initializedLength);
MOZ_ASSERT(numShiftedElements() == 0);
flags |= NONWRITABLE_ARRAY_LENGTH;
}
#ifdef ENABLE_RECORD_TUPLE
void setTupleIsAtomized() { flags |= TUPLE_IS_ATOMIZED; }
bool tupleIsAtomized() const { return flags & TUPLE_IS_ATOMIZED; }
#endif
void addShiftedElements(uint32_t count) {
MOZ_ASSERT(count < capacity);
MOZ_ASSERT(count < initializedLength);
MOZ_ASSERT(!(
flags & (NONWRITABLE_ARRAY_LENGTH | NOT_EXTENSIBLE | SEALED | FROZEN)));
uint32_t numShifted = numShiftedElements() + count;
MOZ_ASSERT(numShifted <= MaxShiftedElements);
flags = (numShifted << NumShiftedElementsShift) | (flags & FlagsMask);
capacity -= count;
initializedLength -= count;
}
void unshiftShiftedElements(uint32_t count) {
MOZ_ASSERT(count > 0);
MOZ_ASSERT(!(
flags & (NONWRITABLE_ARRAY_LENGTH | NOT_EXTENSIBLE | SEALED | FROZEN)));
uint32_t numShifted = numShiftedElements();
MOZ_ASSERT(count <= numShifted);
numShifted -= count;
flags = (numShifted << NumShiftedElementsShift) | (flags & FlagsMask);
capacity += count;
initializedLength += count;
}
void clearShiftedElements() {
flags &= FlagsMask;
MOZ_ASSERT(numShiftedElements() == 0);
}
void markNonPacked() { flags |= NON_PACKED; }
void markMaybeInIteration() { flags |= MAYBE_IN_ITERATION; }
bool maybeInIteration() { return flags & MAYBE_IN_ITERATION; }
void setNotExtensible() {
MOZ_ASSERT(!isNotExtensible());
flags |= NOT_EXTENSIBLE;
}
bool isNotExtensible() { return flags & NOT_EXTENSIBLE; }
void seal() {
MOZ_ASSERT(isNotExtensible());
MOZ_ASSERT(!isSealed());
MOZ_ASSERT(!isFrozen());
flags |= SEALED;
}
void freeze() {
MOZ_ASSERT(isNotExtensible());
MOZ_ASSERT(isSealed());
MOZ_ASSERT(!isFrozen());
flags |= FROZEN;
}
bool isFrozen() const { return flags & FROZEN; }
public:
constexpr ObjectElements(uint32_t capacity, uint32_t length)
: flags(0), initializedLength(0), capacity(capacity), length(length) {}
enum class SharedMemory { IsShared };
constexpr ObjectElements(uint32_t capacity, uint32_t length,
SharedMemory shmem)
: flags(SHARED_MEMORY),
initializedLength(0),
capacity(capacity),
length(length) {}
HeapSlot* elements() {
return reinterpret_cast<HeapSlot*>(uintptr_t(this) +
sizeof(ObjectElements));
}
const HeapSlot* elements() const {
return reinterpret_cast<const HeapSlot*>(uintptr_t(this) +
sizeof(ObjectElements));
}
static ObjectElements* fromElements(HeapSlot* elems) {
return reinterpret_cast<ObjectElements*>(uintptr_t(elems) -
sizeof(ObjectElements));
}
bool isSharedMemory() const { return flags & SHARED_MEMORY; }
static int offsetOfFlags() {
return int(offsetof(ObjectElements, flags)) - int(sizeof(ObjectElements));
}
static int offsetOfInitializedLength() {
return int(offsetof(ObjectElements, initializedLength)) -
int(sizeof(ObjectElements));
}
static int offsetOfCapacity() {
return int(offsetof(ObjectElements, capacity)) -
int(sizeof(ObjectElements));
}
static int offsetOfLength() {
return int(offsetof(ObjectElements, length)) - int(sizeof(ObjectElements));
}
static void PrepareForPreventExtensions(JSContext* cx, NativeObject* obj);
static void PreventExtensions(NativeObject* obj);
[[nodiscard]] static bool FreezeOrSeal(JSContext* cx,
Handle<NativeObject*> obj,
IntegrityLevel level);
bool isSealed() const { return flags & SEALED; }
bool isPacked() const { return !(flags & NON_PACKED); }
JS::PropertyAttributes elementAttributes() const {
if (isFrozen()) {
return {JS::PropertyAttribute::Enumerable};
}
if (isSealed()) {
return {JS::PropertyAttribute::Enumerable,
JS::PropertyAttribute::Writable};
}
return {JS::PropertyAttribute::Configurable,
JS::PropertyAttribute::Enumerable, JS::PropertyAttribute::Writable};
}
uint32_t numShiftedElements() const {
uint32_t numShifted = flags >> NumShiftedElementsShift;
MOZ_ASSERT_IF(numShifted > 0,
!(flags & (NONWRITABLE_ARRAY_LENGTH | NOT_EXTENSIBLE |
SEALED | FROZEN)));
return numShifted;
}
uint32_t numAllocatedElements() const {
return VALUES_PER_HEADER + capacity + numShiftedElements();
}
// This is enough slots to store an object of this class. See the static
// assertion below.
static const size_t VALUES_PER_HEADER = 2;
#if defined(DEBUG) || defined(JS_JITSPEW)
void dumpStringContent(js::GenericPrinter& out) const;
#endif
};
static_assert(ObjectElements::VALUES_PER_HEADER * sizeof(HeapSlot) ==
sizeof(ObjectElements),
"ObjectElements doesn't fit in the given number of slots");
/*
* Slots header used for native objects. The header stores the capacity and the
* slot data follows in memory.
*/
class alignas(HeapSlot) ObjectSlots {
uint32_t capacity_;
uint32_t dictionarySlotSpan_;
uint64_t maybeUniqueId_;
public:
// Special values for maybeUniqueId_ to indicate no unique ID is present.
static constexpr uint64_t NoUniqueIdInDynamicSlots = 0;
static constexpr uint64_t NoUniqueIdInSharedEmptySlots = 1;
static constexpr uint64_t LastNoUniqueIdValue = NoUniqueIdInSharedEmptySlots;
static constexpr size_t VALUES_PER_HEADER = 2;
static inline size_t allocCount(size_t slotCount) {
static_assert(sizeof(ObjectSlots) ==
ObjectSlots::VALUES_PER_HEADER * sizeof(HeapSlot));
#ifdef MOZ_VALGRIND
if (slotCount == 0) {
// Add an extra unused slot so that NativeObject::slots_ always points
// into the allocation otherwise valgrind thinks this is a leak.
slotCount = 1;
}
#endif
return slotCount + VALUES_PER_HEADER;
}
static inline size_t allocSize(size_t slotCount) {
return allocCount(slotCount) * sizeof(HeapSlot);
}
static ObjectSlots* fromSlots(HeapSlot* slots) {
MOZ_ASSERT(slots);
return reinterpret_cast<ObjectSlots*>(uintptr_t(slots) -
sizeof(ObjectSlots));
}
static constexpr size_t offsetOfCapacity() {
return offsetof(ObjectSlots, capacity_);
}
static constexpr size_t offsetOfDictionarySlotSpan() {
return offsetof(ObjectSlots, dictionarySlotSpan_);
}
static constexpr size_t offsetOfMaybeUniqueId() {
return offsetof(ObjectSlots, maybeUniqueId_);
}
static constexpr size_t offsetOfSlots() { return sizeof(ObjectSlots); }
constexpr explicit ObjectSlots(uint32_t capacity, uint32_t dictionarySlotSpan,
uint64_t maybeUniqueId);
constexpr uint32_t capacity() const { return capacity_; }
constexpr uint32_t dictionarySlotSpan() const { return dictionarySlotSpan_; }
bool isSharedEmptySlots() const {
return maybeUniqueId_ == NoUniqueIdInSharedEmptySlots;
}
constexpr bool hasUniqueId() const {
return maybeUniqueId_ > LastNoUniqueIdValue;
}
uint64_t uniqueId() const {
MOZ_ASSERT(hasUniqueId());
return maybeUniqueId_;
}
uintptr_t maybeUniqueId() const { return hasUniqueId() ? maybeUniqueId_ : 0; }
void setUniqueId(uint64_t uid) {
MOZ_ASSERT(uid > LastNoUniqueIdValue);
MOZ_ASSERT(!isSharedEmptySlots());
maybeUniqueId_ = uid;
}
void setDictionarySlotSpan(uint32_t span) { dictionarySlotSpan_ = span; }
HeapSlot* slots() const {
return reinterpret_cast<HeapSlot*>(uintptr_t(this) + sizeof(ObjectSlots));
}
};
/*
* Shared singletons for objects with no elements.
* emptyObjectElementsShared is used only for TypedArrays, when the TA
* maps shared memory.
*/
extern HeapSlot* const emptyObjectElements;
extern HeapSlot* const emptyObjectElementsShared;
/*
* Shared singletons for objects with no dynamic slots.
*/
extern HeapSlot* const emptyObjectSlots;
extern HeapSlot* const emptyObjectSlotsForDictionaryObject[];
class AutoCheckShapeConsistency;
class GCMarker;
// Operations which change an object's dense elements can either succeed, fail,
// or be unable to complete. The latter is used when the object's elements must
// become sparse instead. The enum below is used for such operations.
enum class DenseElementResult { Failure, Success, Incomplete };
// Stores a slot offset in bytes relative to either the NativeObject* address
// (if isFixedSlot) or to NativeObject::slots_ (if !isFixedSlot).
class TaggedSlotOffset {
uint32_t bits_ = 0;
public:
static constexpr size_t OffsetShift = 1;
static constexpr size_t IsFixedSlotFlag = 0b1;
static constexpr size_t MaxOffset = SHAPE_MAXIMUM_SLOT * sizeof(Value);
static_assert((uint64_t(MaxOffset) << OffsetShift) <= UINT32_MAX,
"maximum slot offset must fit in TaggedSlotOffset");
constexpr TaggedSlotOffset() = default;
TaggedSlotOffset(uint32_t offset, bool isFixedSlot)
: bits_((offset << OffsetShift) | isFixedSlot) {
MOZ_ASSERT(offset <= MaxOffset);
}
uint32_t offset() const { return bits_ >> OffsetShift; }
bool isFixedSlot() const { return bits_ & IsFixedSlotFlag; }
bool operator==(const TaggedSlotOffset& other) const {
return bits_ == other.bits_;
}
bool operator!=(const TaggedSlotOffset& other) const {
return !(*this == other);
}
};
enum class CanReuseShape {
// The Shape can be reused. This implies CanReusePropMap.
CanReuseShape,
// Only the PropMap can be reused.
CanReusePropMap,
// Neither the PropMap nor Shape can be reused.
NoReuse,
};
/*
* [SMDOC] NativeObject layout
*
* NativeObject specifies the internal implementation of a native object.
*
* Native objects use ShapedObject::shape to record property information. Two
* native objects with the same shape are guaranteed to have the same number of
* fixed slots.
*
* Native objects extend the base implementation of an object with storage for
* the object's named properties and indexed elements.
*
* These are stored separately from one another. Objects are followed by a
* variable-sized array of values for inline storage, which may be used by
* either properties of native objects (fixed slots), by elements (fixed
* elements), or by other data for certain kinds of objects, such as
* ArrayBufferObjects and TypedArrayObjects.
*
* Named property storage can be split between fixed slots and a dynamically
* allocated array (the slots member). For an object with N fixed slots, shapes
* with slots [0..N-1] are stored in the fixed slots, and the remainder are
* stored in the dynamic array. If all properties fit in the fixed slots, the
* 'slots_' member is nullptr.
*
* Elements are indexed via the 'elements_' member. This member can point to
* either the shared emptyObjectElements and emptyObjectElementsShared
* singletons, into the inline value array (the address of the third value, to
* leave room for a ObjectElements header;in this case numFixedSlots() is zero)
* or to a dynamically allocated array.
*
* Slots and elements may both be non-empty. The slots may be either names or
* indexes; no indexed property will be in both the slots and elements.
*/
class NativeObject : public JSObject {
protected:
/* Slots for object properties. */
js::HeapSlot* slots_;
/* Slots for object dense elements. */
js::HeapSlot* elements_;
friend class ::JSObject;
private:
static void staticAsserts() {
static_assert(sizeof(NativeObject) == sizeof(JSObject_Slots0),
"native object size must match GC thing size");
static_assert(sizeof(NativeObject) == sizeof(JS::shadow::Object),
"shadow interface must match actual implementation");
static_assert(sizeof(NativeObject) % sizeof(Value) == 0,
"fixed slots after an object must be aligned");
static_assert(offsetOfShape() == offsetof(JS::shadow::Object, shape),
"shadow type must match actual type");
static_assert(
offsetof(NativeObject, slots_) == offsetof(JS::shadow::Object, slots),
"shadow slots must match actual slots");
static_assert(
offsetof(NativeObject, elements_) == offsetof(JS::shadow::Object, _1),
"shadow placeholder must match actual elements");
static_assert(MAX_FIXED_SLOTS <= Shape::FIXED_SLOTS_MAX,
"verify numFixedSlots() bitfield is big enough");
static_assert(sizeof(NativeObject) + MAX_FIXED_SLOTS * sizeof(Value) ==
JSObject::MAX_BYTE_SIZE,
"inconsistent maximum object size");
// Sanity check NativeObject size is what we expect.
#ifdef JS_64BIT
static_assert(sizeof(NativeObject) == 3 * sizeof(void*));
#else
static_assert(sizeof(NativeObject) == 4 * sizeof(void*));
#endif
}
public:
NativeShape* shape() const { return &JSObject::shape()->asNative(); }
SharedShape* sharedShape() const { return &shape()->asShared(); }
DictionaryShape* dictionaryShape() const { return &shape()->asDictionary(); }
PropertyInfoWithKey getLastProperty() const {
return shape()->lastProperty();
}
HeapSlotArray getDenseElements() const { return HeapSlotArray(elements_); }
const Value& getDenseElement(uint32_t idx) const {
MOZ_ASSERT(idx < getDenseInitializedLength());
return elements_[idx];
}
bool containsDenseElement(uint32_t idx) const {
return idx < getDenseInitializedLength() &&
!elements_[idx].isMagic(JS_ELEMENTS_HOLE);
}
uint32_t getDenseInitializedLength() const {
return getElementsHeader()->initializedLength;
}
uint32_t getDenseCapacity() const { return getElementsHeader()->capacity; }
bool isSharedMemory() const { return getElementsHeader()->isSharedMemory(); }
// Update the object's shape and allocate slots if needed to match the shape's
// slot span.
MOZ_ALWAYS_INLINE bool setShapeAndAddNewSlots(JSContext* cx,
SharedShape* newShape,
uint32_t oldSpan,
uint32_t newSpan);
// Methods optimized for adding/removing a single slot. Must only be used for
// non-dictionary objects.
MOZ_ALWAYS_INLINE bool setShapeAndAddNewSlot(JSContext* cx,
SharedShape* newShape,
uint32_t slot);
void setShapeAndRemoveLastSlot(JSContext* cx, SharedShape* newShape,
uint32_t slot);
MOZ_ALWAYS_INLINE CanReuseShape
canReuseShapeForNewProperties(NativeShape* newShape) const {
NativeShape* oldShape = shape();
MOZ_ASSERT(oldShape->propMapLength() == 0,
"object must have no properties");
MOZ_ASSERT(newShape->propMapLength() > 0,
"new shape must have at least one property");
if (oldShape->isDictionary() || newShape->isDictionary()) {
return CanReuseShape::NoReuse;
}
// We only handle the common case where the old shape has no object flags
// (expected because it's an empty object) and the new shape has just the
// HasEnumerable flag that we can copy safely.
if (!oldShape->objectFlags().isEmpty()) {
return CanReuseShape::NoReuse;
}
MOZ_ASSERT(newShape->hasObjectFlag(ObjectFlag::HasEnumerable));
if (newShape->objectFlags() != ObjectFlags({ObjectFlag::HasEnumerable})) {
return CanReuseShape::NoReuse;
}
// If the number of fixed slots or the BaseShape is different, we can't
// reuse the Shape but we can still reuse the PropMap.
if (oldShape->numFixedSlots() != newShape->numFixedSlots() ||
oldShape->base() != newShape->base()) {
return CanReuseShape::CanReusePropMap;
}
MOZ_ASSERT(oldShape->getObjectClass() == newShape->getObjectClass());
MOZ_ASSERT(oldShape->proto() == newShape->proto());
MOZ_ASSERT(oldShape->realm() == newShape->realm());
return CanReuseShape::CanReuseShape;
}
// Newly-created TypedArrays that map a SharedArrayBuffer are
// marked as shared by giving them an ObjectElements that has the
// ObjectElements::SHARED_MEMORY flag set.
void setIsSharedMemory() {
MOZ_ASSERT(elements_ == emptyObjectElements);
elements_ = emptyObjectElementsShared;
}
inline bool isInWholeCellBuffer() const;
static inline NativeObject* create(JSContext* cx, gc::AllocKind kind,
gc::Heap heap, Handle<SharedShape*> shape,
gc::AllocSite* site = nullptr);
template <typename T>
static inline T* create(JSContext* cx, gc::AllocKind kind, gc::Heap heap,
Handle<SharedShape*> shape,
gc::AllocSite* site = nullptr) {
NativeObject* nobj = create(cx, kind, heap, shape, site);
return nobj ? &nobj->as<T>() : nullptr;
}
#ifdef DEBUG
static void enableShapeConsistencyChecks();
#endif
protected:
#ifdef DEBUG
friend class js::AutoCheckShapeConsistency;
void checkShapeConsistency();
#else
void checkShapeConsistency() {}
#endif
void maybeFreeDictionaryPropSlots(JSContext* cx, DictionaryPropMap* map,
uint32_t mapLength);
[[nodiscard]] static bool toDictionaryMode(JSContext* cx,
Handle<NativeObject*> obj);
private:
inline void setEmptyDynamicSlots(uint32_t dictonarySlotSpan);
inline void setDictionaryModeSlotSpan(uint32_t span);
friend class gc::TenuringTracer;
// Given a slot range from |start| to |end| exclusive, call |fun| with
// pointers to the corresponding fixed slot and/or dynamic slot ranges.
template <typename Fun>
void forEachSlotRangeUnchecked(uint32_t start, uint32_t end, const Fun& fun) {
MOZ_ASSERT(end >= start);
uint32_t nfixed = numFixedSlots();
if (start < nfixed) {
HeapSlot* fixedStart = &fixedSlots()[start];
HeapSlot* fixedEnd = &fixedSlots()[std::min(nfixed, end)];
fun(fixedStart, fixedEnd);
start = nfixed;
}
if (end > nfixed) {
HeapSlot* dynStart = &slots_[start - nfixed];
HeapSlot* dynEnd = &slots_[end - nfixed];
fun(dynStart, dynEnd);
}
}
template <typename Fun>
void forEachSlotRange(uint32_t start, uint32_t end, const Fun& fun) {
MOZ_ASSERT(slotInRange(end, SENTINEL_ALLOWED));
forEachSlotRangeUnchecked(start, end, fun);
}
protected:
friend class DictionaryPropMap;
friend class GCMarker;
friend class Shape;
void invalidateSlotRange(uint32_t start, uint32_t end) {
#ifdef DEBUG
forEachSlotRange(start, end, [](HeapSlot* slotsStart, HeapSlot* slotsEnd) {
Debug_SetSlotRangeToCrashOnTouch(slotsStart, slotsEnd);
});
#endif /* DEBUG */
}
void initFixedSlots(uint32_t numSlots) {
MOZ_ASSERT(numSlots == numUsedFixedSlots());
HeapSlot* slots = fixedSlots();
for (uint32_t i = 0; i < numSlots; i++) {
slots[i].initAsUndefined();
}
}
void initDynamicSlots(uint32_t numSlots) {
MOZ_ASSERT(numSlots == sharedShape()->slotSpan() - numFixedSlots());
HeapSlot* slots = slots_;
for (uint32_t i = 0; i < numSlots; i++) {
slots[i].initAsUndefined();
}
}
void initSlots(uint32_t nfixed, uint32_t slotSpan) {
initFixedSlots(std::min(nfixed, slotSpan));
if (slotSpan > nfixed) {
initDynamicSlots(slotSpan - nfixed);
}
}
#ifdef DEBUG
enum SentinelAllowed{SENTINEL_NOT_ALLOWED, SENTINEL_ALLOWED};
/*
* Check that slot is in range for the object's allocated slots.
* If sentinelAllowed then slot may equal the slot capacity.
*/
bool slotInRange(uint32_t slot,
SentinelAllowed sentinel = SENTINEL_NOT_ALLOWED) const;
/*
* Check whether a slot is a fixed slot.
*/
bool slotIsFixed(uint32_t slot) const;
/*
* Check whether the supplied number of fixed slots is correct.
*/
bool isNumFixedSlots(uint32_t nfixed) const;
#endif
/*
* Minimum size for dynamically allocated slots in normal Objects.
* ArrayObjects don't use this limit and can have a lower slot capacity,
* since they normally don't have a lot of slots.
*/
static const uint32_t SLOT_CAPACITY_MIN = 8 - ObjectSlots::VALUES_PER_HEADER;
/*
* Minimum size for dynamically allocated elements in normal Objects.
*/
static const uint32_t ELEMENT_CAPACITY_MIN =
8 - ObjectElements::VALUES_PER_HEADER;
HeapSlot* fixedSlots() const {
return reinterpret_cast<HeapSlot*>(uintptr_t(this) + sizeof(NativeObject));
}
public:
inline void initEmptyDynamicSlots();
[[nodiscard]] static bool generateNewDictionaryShape(
JSContext* cx, Handle<NativeObject*> obj);
// The maximum number of slots in an object.
// |MAX_SLOTS_COUNT * sizeof(JS::Value)| shouldn't overflow
// int32_t (see slotsSizeMustNotOverflow).
static const uint32_t MAX_SLOTS_COUNT = (1 << 28) - 1;
static void slotsSizeMustNotOverflow() {
static_assert(
NativeObject::MAX_SLOTS_COUNT <= INT32_MAX / sizeof(JS::Value),
"every caller of this method requires that a slot "
"number (or slot count) count multiplied by "
"sizeof(Value) can't overflow uint32_t (and sometimes "
"int32_t, too)");
}
uint32_t numFixedSlots() const {
return reinterpret_cast<const JS::shadow::Object*>(this)->numFixedSlots();
}
// Get the number of fixed slots when the shape pointer may have been
// forwarded by a moving GC. You need to use this rather that
// numFixedSlots() in a trace hook if you access an object that is not the
// object being traced, since it may have a stale shape pointer.
inline uint32_t numFixedSlotsMaybeForwarded() const;
uint32_t numUsedFixedSlots() const {
uint32_t nslots = sharedShape()->slotSpan();
return std::min(nslots, numFixedSlots());
}
uint32_t slotSpan() const {
if (inDictionaryMode()) {
return dictionaryModeSlotSpan();
}
MOZ_ASSERT(getSlotsHeader()->dictionarySlotSpan() == 0);
return sharedShape()->slotSpan();
}
uint32_t dictionaryModeSlotSpan() const {
MOZ_ASSERT(inDictionaryMode());
return getSlotsHeader()->dictionarySlotSpan();
}
/* Whether a slot is at a fixed offset from this object. */
bool isFixedSlot(size_t slot) { return slot < numFixedSlots(); }
/* Index into the dynamic slots array to use for a dynamic slot. */
size_t dynamicSlotIndex(size_t slot) {
MOZ_ASSERT(slot >= numFixedSlots());
return slot - numFixedSlots();
}
// Native objects are never proxies. Call isExtensible instead.
bool nonProxyIsExtensible() const = delete;
bool isExtensible() const {
#ifdef ENABLE_RECORD_TUPLE
if (IsExtendedPrimitiveWrapper(*this)) {
return false;
}
#endif
return !hasFlag(ObjectFlag::NotExtensible);
}
/*
* Whether there may be indexed properties on this object, excluding any in
* the object's elements.
*/
bool isIndexed() const { return hasFlag(ObjectFlag::Indexed); }
bool hasInterestingSymbol() const {
return hasFlag(ObjectFlag::HasInterestingSymbol);
}
bool hasEnumerableProperty() const {
return hasFlag(ObjectFlag::HasEnumerable);
}
static bool setHadGetterSetterChange(JSContext* cx,
Handle<NativeObject*> obj) {
return setFlag(cx, obj, ObjectFlag::HadGetterSetterChange);
}
bool hadGetterSetterChange() const {
return hasFlag(ObjectFlag::HadGetterSetterChange);
}
bool allocateInitialSlots(JSContext* cx, uint32_t capacity);
/*
* Grow or shrink slots immediately before changing the slot span.
* The number of allocated slots is not stored explicitly, and changes to
* the slots must track changes in the slot span.
*/
bool growSlots(JSContext* cx, uint32_t oldCapacity, uint32_t newCapacity);
bool growSlotsForNewSlot(JSContext* cx, uint32_t numFixed, uint32_t slot);
void shrinkSlots(JSContext* cx, uint32_t oldCapacity, uint32_t newCapacity);
bool allocateSlots(Nursery& nursery, uint32_t newCapacity);
/*
* This method is static because it's called from JIT code. On OOM, returns
* false without leaving a pending exception on the context.
*/
static bool growSlotsPure(JSContext* cx, NativeObject* obj,
uint32_t newCapacity);
/*
* Like growSlotsPure but for dense elements. This will return
* false if we failed to allocate a dense element for some reason (OOM, too
* many dense elements, non-writable array length, etc).
*/
static bool addDenseElementPure(JSContext* cx, NativeObject* obj);
/*
* Indicates whether this object has an ObjectSlots allocation attached. The
* capacity of this can be zero if it is only used to hold a unique ID.
*/
bool hasDynamicSlots() const {
return !getSlotsHeader()->isSharedEmptySlots();
}
/* Compute the number of dynamic slots required for this object. */
MOZ_ALWAYS_INLINE uint32_t calculateDynamicSlots() const;
MOZ_ALWAYS_INLINE uint32_t numDynamicSlots() const;
#ifdef DEBUG
uint32_t outOfLineNumDynamicSlots() const;
#endif
bool empty() const { return shape()->propMapLength() == 0; }
mozilla::Maybe<PropertyInfo> lookup(JSContext* cx, jsid id);
mozilla::Maybe<PropertyInfo> lookup(JSContext* cx, PropertyName* name) {
return lookup(cx, NameToId(name));
}
bool contains(JSContext* cx, jsid id) { return lookup(cx, id).isSome(); }
bool contains(JSContext* cx, PropertyName* name) {
return lookup(cx, name).isSome();
}
bool contains(JSContext* cx, jsid id, PropertyInfo prop) {
mozilla::Maybe<PropertyInfo> found = lookup(cx, id);
return found.isSome() && *found == prop;
}
/* Contextless; can be called from other pure code. */
mozilla::Maybe<PropertyInfo> lookupPure(jsid id);
mozilla::Maybe<PropertyInfo> lookupPure(PropertyName* name) {
return lookupPure(NameToId(name));
}
bool containsPure(jsid id) { return lookupPure(id).isSome(); }
bool containsPure(PropertyName* name) { return containsPure(NameToId(name)); }
bool containsPure(jsid id, PropertyInfo prop) {
mozilla::Maybe<PropertyInfo> found = lookupPure(id);
return found.isSome() && *found == prop;
}
private:
/*
* Allocate and free an object slot.
*
* after calling object-parameter-free shape methods, avoiding coupling
* logic across the object vs. shape module wall.
*/
static bool allocDictionarySlot(JSContext* cx, Handle<NativeObject*> obj,
uint32_t* slotp);
void freeDictionarySlot(uint32_t slot);
static MOZ_ALWAYS_INLINE bool maybeConvertToDictionaryForAdd(
JSContext* cx, Handle<NativeObject*> obj);
public:
// Add a new property. Must only be used when the |id| is not already present
// in the object's shape. Checks for non-extensibility must be done by the
// callers.
static bool addProperty(JSContext* cx, Handle<NativeObject*> obj, HandleId id,
PropertyFlags flags, uint32_t* slotOut);
static bool addProperty(JSContext* cx, Handle<NativeObject*> obj,
Handle<PropertyName*> name, PropertyFlags flags,
uint32_t* slotOut) {
RootedId id(cx, NameToId(name));
return addProperty(cx, obj, id, flags, slotOut);
}
static bool addPropertyInReservedSlot(JSContext* cx,
Handle<NativeObject*> obj, HandleId id,
uint32_t slot, PropertyFlags flags);
static bool addPropertyInReservedSlot(JSContext* cx,
Handle<NativeObject*> obj,
Handle<PropertyName*> name,
uint32_t slot, PropertyFlags flags) {
RootedId id(cx, NameToId(name));
return addPropertyInReservedSlot(cx, obj, id, slot, flags);
}
static bool addCustomDataProperty(JSContext* cx, Handle<NativeObject*> obj,
HandleId id, PropertyFlags flags);
// Change a property with key |id| in this object. The object must already
// have a property (stored in the shape tree) with this |id|.
static bool changeProperty(JSContext* cx, Handle<NativeObject*> obj,
HandleId id, PropertyFlags flags,
uint32_t* slotOut);
static bool changeCustomDataPropAttributes(JSContext* cx,
Handle<NativeObject*> obj,
HandleId id, PropertyFlags flags);
// Remove the property named by id from this object.
static bool removeProperty(JSContext* cx, Handle<NativeObject*> obj,
HandleId id);
static bool freezeOrSealProperties(JSContext* cx, Handle<NativeObject*> obj,
IntegrityLevel level);
protected:
static bool changeNumFixedSlotsAfterSwap(JSContext* cx,
Handle<NativeObject*> obj,
uint32_t nfixed);
// For use from JSObject::swap.
[[nodiscard]] bool prepareForSwap(JSContext* cx,
MutableHandleValueVector slotValuesOut);
[[nodiscard]] static bool fixupAfterSwap(JSContext* cx,
Handle<NativeObject*> obj,
gc::AllocKind kind,
HandleValueVector slotValues);
public:
// Return true if this object has been converted from shared-immutable
// shapes to object-owned dictionary shapes.
bool inDictionaryMode() const { return shape()->isDictionary(); }
const Value& getSlot(uint32_t slot) const {
MOZ_ASSERT(slotInRange(slot));
uint32_t fixed = numFixedSlots();
if (slot < fixed) {
return fixedSlots()[slot];
}
return slots_[slot - fixed];
}
const HeapSlot* getSlotAddressUnchecked(uint32_t slot) const {
uint32_t fixed = numFixedSlots();
if (slot < fixed) {
return fixedSlots() + slot;
}
return slots_ + (slot - fixed);
}
HeapSlot* getSlotAddressUnchecked(uint32_t slot) {
uint32_t fixed = numFixedSlots();
if (slot < fixed) {
return fixedSlots() + slot;
}
return slots_ + (slot - fixed);
}
HeapSlot* getSlotsUnchecked() { return slots_; }
HeapSlot* getSlotAddress(uint32_t slot) {
/*
* This can be used to get the address of the end of the slots for the
* object, which may be necessary when fetching zero-length arrays of
* slots (e.g. for callObjVarArray).
*/
MOZ_ASSERT(slotInRange(slot, SENTINEL_ALLOWED));
return getSlotAddressUnchecked(slot);
}
const HeapSlot* getSlotAddress(uint32_t slot) const {
/*
* This can be used to get the address of the end of the slots for the
* object, which may be necessary when fetching zero-length arrays of
* slots (e.g. for callObjVarArray).
*/
MOZ_ASSERT(slotInRange(slot, SENTINEL_ALLOWED));
return getSlotAddressUnchecked(slot);
}
MOZ_ALWAYS_INLINE HeapSlot& getSlotRef(uint32_t slot) {
MOZ_ASSERT(slotInRange(slot));
return *getSlotAddress(slot);
}
MOZ_ALWAYS_INLINE const HeapSlot& getSlotRef(uint32_t slot) const {
MOZ_ASSERT(slotInRange(slot));
return *getSlotAddress(slot);
}
// Check requirements on values stored to this object.
MOZ_ALWAYS_INLINE void checkStoredValue(const Value& v) {
MOZ_ASSERT(IsObjectValueInCompartment(v, compartment()));
MOZ_ASSERT(AtomIsMarked(zoneFromAnyThread(), v));
MOZ_ASSERT_IF(v.isMagic() && v.whyMagic() == JS_ELEMENTS_HOLE,
!denseElementsArePacked());
}
MOZ_ALWAYS_INLINE void setSlot(uint32_t slot, const Value& value) {
MOZ_ASSERT(slotInRange(slot));
checkStoredValue(value);
getSlotRef(slot).set(this, HeapSlot::Slot, slot, value);
}
MOZ_ALWAYS_INLINE void initSlot(uint32_t slot, const Value& value) {
MOZ_ASSERT(getSlot(slot).isUndefined());
MOZ_ASSERT(slotInRange(slot));
checkStoredValue(value);
initSlotUnchecked(slot, value);
}
MOZ_ALWAYS_INLINE void initSlotUnchecked(uint32_t slot, const Value& value) {
getSlotAddressUnchecked(slot)->init(this, HeapSlot::Slot, slot, value);
}
// Returns the GetterSetter for an accessor property.
GetterSetter* getGetterSetter(uint32_t slot) const {
return getSlot(slot).toGCThing()->as<GetterSetter>();
}
GetterSetter* getGetterSetter(PropertyInfo prop) const {
MOZ_ASSERT(prop.isAccessorProperty());
return getGetterSetter(prop.slot());
}
// Returns the (possibly nullptr) getter or setter object. |prop| and |slot|
// must be (for) an accessor property.
JSObject* getGetter(uint32_t slot) const {
return getGetterSetter(slot)->getter();
}
JSObject* getGetter(PropertyInfo prop) const {
return getGetterSetter(prop)->getter();
}
JSObject* getSetter(PropertyInfo prop) const {
return getGetterSetter(prop)->setter();
}
// Returns true if the property has a non-nullptr getter or setter object.
// |prop| can be any property.
bool hasGetter(PropertyInfo prop) const {
return prop.isAccessorProperty() && getGetter(prop);
}
bool hasSetter(PropertyInfo prop) const {
return prop.isAccessorProperty() && getSetter(prop);
}
// If the property has a non-nullptr getter/setter, return it as ObjectValue.
// Else return |undefined|. |prop| must be an accessor property.
Value getGetterValue(PropertyInfo prop) const {
MOZ_ASSERT(prop.isAccessorProperty());
if (JSObject* getterObj = getGetter(prop)) {
return ObjectValue(*getterObj);
}
return UndefinedValue();
}
Value getSetterValue(PropertyInfo prop) const {
MOZ_ASSERT(prop.isAccessorProperty());
if (JSObject* setterObj = getSetter(prop)) {
return ObjectValue(*setterObj);
}
return UndefinedValue();
}
[[nodiscard]] bool setUniqueId(JSRuntime* runtime, uint64_t uid);
inline bool hasUniqueId() const { return getSlotsHeader()->hasUniqueId(); }
inline uint64_t uniqueId() const { return getSlotsHeader()->uniqueId(); }
inline uint64_t maybeUniqueId() const {
return getSlotsHeader()->maybeUniqueId();
}
bool setOrUpdateUniqueId(JSContext* cx, uint64_t uid);
// MAX_FIXED_SLOTS is the biggest number of fixed slots our GC
// size classes will give an object.
static constexpr uint32_t MAX_FIXED_SLOTS =
JS::shadow::Object::MAX_FIXED_SLOTS;
private:
void prepareElementRangeForOverwrite(size_t start, size_t end) {
MOZ_ASSERT(end <= getDenseInitializedLength());
for (size_t i = start; i < end; i++) {
elements_[i].destroy();
}
}
/*
* Trigger the write barrier on a range of slots that will no longer be
* reachable.
*/
void prepareSlotRangeForOverwrite(size_t start, size_t end) {
for (size_t i = start; i < end; i++) {
getSlotAddressUnchecked(i)->destroy();
}
}
inline void shiftDenseElementsUnchecked(uint32_t count);
// Like getSlotRef, but optimized for reserved slots. This relies on the fact
// that the first reserved slots (up to MAX_FIXED_SLOTS) are always stored in
// fixed slots. This lets the compiler optimize away the branch below when
// |index| is a constant (after inlining).
//
// Note: objects that may be swapped have less predictable slot layouts
// because they could have been swapped with an object with fewer fixed slots.
// Fortunately, the only native objects that can be swapped are DOM objects
// and these shouldn't end up here (asserted below).
MOZ_ALWAYS_INLINE HeapSlot& getReservedSlotRef(uint32_t index) {
MOZ_ASSERT(index < JSSLOT_FREE(getClass()));
MOZ_ASSERT(slotIsFixed(index) == (index < MAX_FIXED_SLOTS));
MOZ_ASSERT(!ObjectMayBeSwapped(this));
return index < MAX_FIXED_SLOTS ? fixedSlots()[index]
: slots_[index - MAX_FIXED_SLOTS];
}
MOZ_ALWAYS_INLINE const HeapSlot& getReservedSlotRef(uint32_t index) const {
MOZ_ASSERT(index < JSSLOT_FREE(getClass()));
MOZ_ASSERT(slotIsFixed(index) == (index < MAX_FIXED_SLOTS));
MOZ_ASSERT(!ObjectMayBeSwapped(this));
return index < MAX_FIXED_SLOTS ? fixedSlots()[index]
: slots_[index - MAX_FIXED_SLOTS];
}
public:
MOZ_ALWAYS_INLINE const Value& getReservedSlot(uint32_t index) const {
return getReservedSlotRef(index);
}
MOZ_ALWAYS_INLINE void initReservedSlot(uint32_t index, const Value& v) {
MOZ_ASSERT(getReservedSlot(index).isUndefined());
checkStoredValue(v);
getReservedSlotRef(index).init(this, HeapSlot::Slot, index, v);
}
MOZ_ALWAYS_INLINE void setReservedSlot(uint32_t index, const Value& v) {
checkStoredValue(v);
getReservedSlotRef(index).set(this, HeapSlot::Slot, index, v);
}
// For slots which are known to always be fixed, due to the way they are
// allocated.
HeapSlot& getFixedSlotRef(uint32_t slot) {
MOZ_ASSERT(slotIsFixed(slot));
return fixedSlots()[slot];
}
const Value& getFixedSlot(uint32_t slot) const {
MOZ_ASSERT(slotIsFixed(slot));
return fixedSlots()[slot];
}
const Value& getDynamicSlot(uint32_t dynamicSlotIndex) const {
MOZ_ASSERT(dynamicSlotIndex < outOfLineNumDynamicSlots());
return slots_[dynamicSlotIndex];
}
void setFixedSlot(uint32_t slot, const Value& value) {
MOZ_ASSERT(slotIsFixed(slot));
checkStoredValue(value);
fixedSlots()[slot].set(this, HeapSlot::Slot, slot, value);
}
void setDynamicSlot(uint32_t numFixed, uint32_t slot, const Value& value) {
MOZ_ASSERT(numFixedSlots() == numFixed);
MOZ_ASSERT(slot >= numFixed);
MOZ_ASSERT(slot - numFixed < getSlotsHeader()->capacity());
checkStoredValue(value);
slots_[slot - numFixed].set(this, HeapSlot::Slot, slot, value);
}
void initFixedSlot(uint32_t slot, const Value& value) {
MOZ_ASSERT(slotIsFixed(slot));
checkStoredValue(value);
fixedSlots()[slot].init(this, HeapSlot::Slot, slot, value);
}
void initDynamicSlot(uint32_t numFixed, uint32_t slot, const Value& value) {
MOZ_ASSERT(numFixedSlots() == numFixed);
MOZ_ASSERT(slot >= numFixed);
MOZ_ASSERT(slot - numFixed < getSlotsHeader()->capacity());
checkStoredValue(value);
slots_[slot - numFixed].init(this, HeapSlot::Slot, slot, value);
}
template <typename T>
T* maybePtrFromReservedSlot(uint32_t slot) const {
Value v = getReservedSlot(slot);
return v.isUndefined() ? nullptr : static_cast<T*>(v.toPrivate());
}
/*
* Calculate the number of dynamic slots to allocate to cover the properties
* in an object with the given number of fixed slots and slot span.
*/
static MOZ_ALWAYS_INLINE uint32_t calculateDynamicSlots(uint32_t nfixed,
uint32_t span,
const JSClass* clasp);
static MOZ_ALWAYS_INLINE uint32_t calculateDynamicSlots(SharedShape* shape);
ObjectSlots* getSlotsHeader() const { return ObjectSlots::fromSlots(slots_); }
/* Elements accessors. */
// The maximum size, in sizeof(Value), of the allocation used for an
// object's dense elements. (This includes space used to store an
// ObjectElements instance.)
// |MAX_DENSE_ELEMENTS_ALLOCATION * sizeof(JS::Value)| shouldn't overflow
// int32_t (see elementsSizeMustNotOverflow).
static const uint32_t MAX_DENSE_ELEMENTS_ALLOCATION = (1 << 28) - 1;
// The maximum number of usable dense elements in an object.
static const uint32_t MAX_DENSE_ELEMENTS_COUNT =
MAX_DENSE_ELEMENTS_ALLOCATION - ObjectElements::VALUES_PER_HEADER;
static void elementsSizeMustNotOverflow() {
static_assert(
NativeObject::MAX_DENSE_ELEMENTS_COUNT <= INT32_MAX / sizeof(JS::Value),
"every caller of this method require that an element "
"count multiplied by sizeof(Value) can't overflow "
"uint32_t (and sometimes int32_t ,too)");
}
ObjectElements* getElementsHeader() const {
return ObjectElements::fromElements(elements_);
}
// Returns a pointer to the first element, including shifted elements.
inline HeapSlot* unshiftedElements() const {
return elements_ - getElementsHeader()->numShiftedElements();
}
// Like getElementsHeader, but returns a pointer to the unshifted header.
// This is mainly useful for free()ing dynamic elements: the pointer
// returned here is the one we got from malloc.
void* getUnshiftedElementsHeader() const {
return ObjectElements::fromElements(unshiftedElements());
}
uint32_t unshiftedIndex(uint32_t index) const {
return index + getElementsHeader()->numShiftedElements();
}
/* Accessors for elements. */
bool ensureElements(JSContext* cx, uint32_t capacity) {
MOZ_ASSERT(isExtensible());
if (capacity > getDenseCapacity()) {
return growElements(cx, capacity);
}
return true;
}
// Try to shift |count| dense elements, see the "Shifted elements" comment.
inline bool tryShiftDenseElements(uint32_t count);
// Try to make space for |count| dense elements at the start of the array.
bool tryUnshiftDenseElements(uint32_t count);
// Move the elements header and all shifted elements to the start of the
// allocated elements space, so that numShiftedElements is 0 afterwards.
void moveShiftedElements();
// If this object has many shifted elements call moveShiftedElements.
void maybeMoveShiftedElements();
static bool goodElementsAllocationAmount(JSContext* cx, uint32_t reqAllocated,
uint32_t length,
uint32_t* goodAmount);
bool growElements(JSContext* cx, uint32_t newcap);
void shrinkElements(JSContext* cx, uint32_t cap);
private:
// Run a post write barrier that encompasses multiple contiguous elements in a
// single step.
inline void elementsRangePostWriteBarrier(uint32_t start, uint32_t count);
public:
void shrinkCapacityToInitializedLength(JSContext* cx);
private:
void setDenseInitializedLengthInternal(uint32_t length) {
MOZ_ASSERT(length <= getDenseCapacity());
MOZ_ASSERT(!denseElementsAreFrozen());
prepareElementRangeForOverwrite(length,
getElementsHeader()->initializedLength);
getElementsHeader()->initializedLength = length;
}
public:
void setDenseInitializedLength(uint32_t length) {
MOZ_ASSERT(isExtensible());
setDenseInitializedLengthInternal(length);
}
void setDenseInitializedLengthMaybeNonExtensible(JSContext* cx,
uint32_t length) {
setDenseInitializedLengthInternal(length);
if (!isExtensible()) {
shrinkCapacityToInitializedLength(cx);
}
}
inline void ensureDenseInitializedLength(uint32_t index, uint32_t extra);
void setDenseElement(uint32_t index, const Value& val) {
MOZ_ASSERT_IF(val.isMagic(), val.whyMagic() != JS_ELEMENTS_HOLE);
setDenseElementUnchecked(index, val);
}
void initDenseElement(uint32_t index, const Value& val) {
MOZ_ASSERT(!val.isMagic(JS_ELEMENTS_HOLE));
initDenseElementUnchecked(index, val);
}
private:
// Note: 'Unchecked' here means we don't assert |val| isn't the hole
// MagicValue.
void initDenseElementUnchecked(uint32_t index, const Value& val) {
MOZ_ASSERT(index < getDenseInitializedLength());
MOZ_ASSERT(isExtensible());
checkStoredValue(val);
elements_[index].init(this, HeapSlot::Element, unshiftedIndex(index), val);
}
void setDenseElementUnchecked(uint32_t index, const Value& val) {
MOZ_ASSERT(index < getDenseInitializedLength());
MOZ_ASSERT(!denseElementsAreFrozen());
checkStoredValue(val);
elements_[index].set(this, HeapSlot::Element, unshiftedIndex(index), val);
}
// Mark the dense elements as possibly containing holes.
inline void markDenseElementsNotPacked();
public:
inline void initDenseElementHole(uint32_t index);
inline void setDenseElementHole(uint32_t index);
inline void removeDenseElementForSparseIndex(uint32_t index);
inline void copyDenseElements(uint32_t dstStart, const Value* src,
uint32_t count);
inline void initDenseElements(const Value* src, uint32_t count);
inline void initDenseElements(JSLinearString** src, uint32_t count);
inline void initDenseElements(NativeObject* src, uint32_t srcStart,
uint32_t count);
// Copy the first `count` dense elements from `src` to `this`, starting at
// `destStart`. The initialized length must already include the new elements.
inline void initDenseElementRange(uint32_t destStart, NativeObject* src,
uint32_t count);
// Store the Values in the range [begin, end) as elements of this array.
//
// Preconditions: This must be a boring ArrayObject with dense initialized
// length 0: no shifted elements, no frozen elements, no fixed "length", not
// indexed, not inextensible, not copy-on-write. Existing capacity is
// optional.
//
// This runs write barriers but does not update types. `end - begin` must
// return the size of the range, which must be >= 0 and fit in an int32_t.
template <typename Iter>
[[nodiscard]] inline bool initDenseElementsFromRange(JSContext* cx,
Iter begin, Iter end);
inline void moveDenseElements(uint32_t dstStart, uint32_t srcStart,
uint32_t count);
inline void reverseDenseElementsNoPreBarrier(uint32_t length);
inline DenseElementResult setOrExtendDenseElements(JSContext* cx,
uint32_t start,
const Value* vp,
uint32_t count);
bool denseElementsAreSealed() const {
return getElementsHeader()->isSealed();
}
bool denseElementsAreFrozen() const {
return hasFlag(ObjectFlag::FrozenElements);
}
bool denseElementsArePacked() const {
return getElementsHeader()->isPacked();
}
void markDenseElementsMaybeInIteration() {
getElementsHeader()->markMaybeInIteration();
}
// Return whether the object's dense elements might be in the midst of for-in
// iteration. We rely on this to be able to safely delete or move dense array
// elements without worrying about updating in-progress iterators.
//
// Note that it's fine to return false if this object is on the prototype of
// another object: SuppressDeletedProperty only suppresses properties deleted
// from the iterated object itself.
inline bool denseElementsHaveMaybeInIterationFlag();
inline bool denseElementsMaybeInIteration();
// Ensures that the object can hold at least index + extra elements. This
// returns DenseElement_Success on success, DenseElement_Failed on failure
// to grow the array, or DenseElement_Incomplete when the object is too
// sparse to grow (this includes the case of index + extra overflow). In
// the last two cases the object is kept intact.
inline DenseElementResult ensureDenseElements(JSContext* cx, uint32_t index,
uint32_t extra);
inline DenseElementResult extendDenseElements(JSContext* cx,
uint32_t requiredCapacity,
uint32_t extra);
/* Small objects are dense, no matter what. */
static const uint32_t MIN_SPARSE_INDEX = 1000;
/*
* Element storage for an object will be sparse if fewer than 1/8 indexes
* are filled in.
*/
static const unsigned SPARSE_DENSITY_RATIO = 8;
/*
* Check if after growing the object's elements will be too sparse.
* newElementsHint is an estimated number of elements to be added.
*/
bool willBeSparseElements(uint32_t requiredCapacity,
uint32_t newElementsHint);
/*
* After adding a sparse index to obj, see if it should be converted to use
* dense elements.
*/
static DenseElementResult maybeDensifySparseElements(
JSContext* cx, Handle<NativeObject*> obj);
static bool densifySparseElements(JSContext* cx, Handle<NativeObject*> obj);
inline HeapSlot* fixedElements() const {
static_assert(2 * sizeof(Value) == sizeof(ObjectElements),
"when elements are stored inline, the first two "
"slots will hold the ObjectElements header");
return &fixedSlots()[2];
}
#ifdef DEBUG
bool canHaveNonEmptyElements();
#endif
void setEmptyElements() { elements_ = emptyObjectElements; }
void initFixedElements(gc::AllocKind kind, uint32_t length);
// Update the elements pointer to use the fixed elements storage. The caller
// is responsible for initializing the elements themselves and setting the
// FIXED flag.
void setFixedElements(uint32_t numShifted = 0) {
MOZ_ASSERT(canHaveNonEmptyElements());
elements_ = fixedElements() + numShifted;
}
inline bool hasDynamicElements() const {
/*
* Note: for objects with zero fixed slots this could potentially give
* a spurious 'true' result, if the end of this object is exactly
* aligned with the end of its arena and dynamic slots are allocated
* immediately afterwards. Such cases cannot occur for dense arrays
* (which have at least two fixed slots) and can only result in a leak.
*/
return !hasEmptyElements() && !hasFixedElements();
}
inline bool hasFixedElements() const {
bool fixed = getElementsHeader()->flags & ObjectElements::FIXED;
MOZ_ASSERT_IF(fixed, unshiftedElements() == fixedElements());
return fixed;
}
inline bool hasEmptyElements() const {
return elements_ == emptyObjectElements ||
elements_ == emptyObjectElementsShared;
}
/*
* Get a pointer to the unused data in the object's allocation immediately
* following this object, for use with objects which allocate a larger size
* class than they need and store non-elements data inline.
*/
inline uint8_t* fixedData(size_t nslots) const;
inline void privatePreWriteBarrier(HeapSlot* pprivate);
// The methods below are used to store GC things in a reserved slot as
// PrivateValues. This is done to bypass the normal tracing code (debugger
// objects use this to store cross-compartment pointers).
//
// WARNING: make sure you REALLY need this and you know what you're doing
// before using these methods!
void setReservedSlotGCThingAsPrivate(uint32_t slot, gc::Cell* cell) {
#ifdef DEBUG
if (IsMarkedBlack(this)) {
JS::AssertCellIsNotGray(cell);
}
#endif
HeapSlot* pslot = getSlotAddress(slot);
Cell* prev = nullptr;
if (!pslot->isUndefined()) {
prev = static_cast<gc::Cell*>(pslot->toPrivate());
privatePreWriteBarrier(pslot);
}
setReservedSlotGCThingAsPrivateUnbarriered(slot, cell);
gc::PostWriteBarrierCell(this, prev, cell);
}
void setReservedSlotGCThingAsPrivateUnbarriered(uint32_t slot,
gc::Cell* cell) {
MOZ_ASSERT(slot < JSCLASS_RESERVED_SLOTS(getClass()));
MOZ_ASSERT(cell);
getReservedSlotRef(slot).unbarrieredSet(PrivateValue(cell));
}
void clearReservedSlotGCThingAsPrivate(uint32_t slot) {
MOZ_ASSERT(slot < JSCLASS_RESERVED_SLOTS(getClass()));
HeapSlot* pslot = &getReservedSlotRef(slot);
if (!pslot->isUndefined()) {
privatePreWriteBarrier(pslot);
pslot->unbarrieredSet(UndefinedValue());
}
}
/* Return the allocKind we would use if we were to tenure this object. */
inline js::gc::AllocKind allocKindForTenure() const;
// Native objects are never wrappers, so a native object always has a realm
// and global.
JS::Realm* realm() const { return nonCCWRealm(); }
inline js::GlobalObject& global() const;
TaggedSlotOffset getTaggedSlotOffset(size_t slot) const {
MOZ_ASSERT(slot < slotSpan());
uint32_t nfixed = numFixedSlots();
if (slot < nfixed) {
return TaggedSlotOffset(getFixedSlotOffset(slot),
/* isFixedSlot = */ true);
}
return TaggedSlotOffset((slot - nfixed) * sizeof(Value),
/* isFixedSlot = */ false);
}
/* JIT Accessors */
static size_t offsetOfElements() { return offsetof(NativeObject, elements_); }
static size_t offsetOfFixedElements() {
return sizeof(NativeObject) + sizeof(ObjectElements);
}
static constexpr size_t getFixedSlotOffset(size_t slot) {
MOZ_ASSERT(slot < MAX_FIXED_SLOTS);
return sizeof(NativeObject) + slot * sizeof(Value);
}
static constexpr size_t getFixedSlotIndexFromOffset(size_t offset) {
MOZ_ASSERT(offset >= sizeof(NativeObject));
offset -= sizeof(NativeObject);
MOZ_ASSERT(offset % sizeof(Value) == 0);
MOZ_ASSERT(offset / sizeof(Value) < MAX_FIXED_SLOTS);
return offset / sizeof(Value);
}
static constexpr size_t getDynamicSlotIndexFromOffset(size_t offset) {
MOZ_ASSERT(offset % sizeof(Value) == 0);
return offset / sizeof(Value);
}
static size_t offsetOfSlots() { return offsetof(NativeObject, slots_); }
};
inline void NativeObject::privatePreWriteBarrier(HeapSlot* pprivate) {
JS::shadow::Zone* shadowZone = this->shadowZoneFromAnyThread();
if (shadowZone->needsIncrementalBarrier() && pprivate->get().toPrivate() &&
getClass()->hasTrace()) {
getClass()->doTrace(shadowZone->barrierTracer(), this);
}
}
/*** Standard internal methods **********************************************/
/*
* These functions should follow the algorithms in ES6 draft rev 29 section 9.1
* ("Ordinary Object Internal Methods"). It's an ongoing project.
*
* Many native objects are not "ordinary" in ES6, so these functions also have
* to serve some of the special needs of Functions (9.2, 9.3, 9.4.1), Arrays
* (9.4.2), Strings (9.4.3), and so on.
*/
extern bool NativeDefineProperty(JSContext* cx, Handle<NativeObject*> obj,
HandleId id,
Handle<JS::PropertyDescriptor> desc,
ObjectOpResult& result);
extern bool NativeDefineDataProperty(JSContext* cx, Handle<NativeObject*> obj,
HandleId id, HandleValue value,
unsigned attrs, ObjectOpResult& result);
/* If the result out-param is omitted, throw on failure. */
extern bool NativeDefineAccessorProperty(JSContext* cx,
Handle<NativeObject*> obj, HandleId id,
HandleObject getter,
HandleObject setter, unsigned attrs);
extern bool NativeDefineDataProperty(JSContext* cx, Handle<NativeObject*> obj,
HandleId id, HandleValue value,
unsigned attrs);
extern bool NativeDefineDataProperty(JSContext* cx, Handle<NativeObject*> obj,
PropertyName* name, HandleValue value,
unsigned attrs);
extern bool NativeHasProperty(JSContext* cx, Handle<NativeObject*> obj,
HandleId id, bool* foundp);
extern bool NativeGetOwnPropertyDescriptor(
JSContext* cx, Handle<NativeObject*> obj, HandleId id,
MutableHandle<mozilla::Maybe<JS::PropertyDescriptor>> desc);
extern bool NativeGetProperty(JSContext* cx, Handle<NativeObject*> obj,
HandleValue receiver, HandleId id,
MutableHandleValue vp);
extern bool NativeGetPropertyNoGC(JSContext* cx, NativeObject* obj,
const Value& receiver, jsid id, Value* vp);
inline bool NativeGetProperty(JSContext* cx, Handle<NativeObject*> obj,
HandleId id, MutableHandleValue vp) {
RootedValue receiver(cx, ObjectValue(*obj));
return NativeGetProperty(cx, obj, receiver, id, vp);
}
extern bool NativeGetElement(JSContext* cx, Handle<NativeObject*> obj,
HandleValue receiver, int32_t index,
MutableHandleValue vp);
bool GetSparseElementHelper(JSContext* cx, Handle<NativeObject*> obj,
int32_t int_id, MutableHandleValue result);
bool SetPropertyByDefining(JSContext* cx, HandleId id, HandleValue v,
HandleValue receiver, ObjectOpResult& result);
bool SetPropertyOnProto(JSContext* cx, HandleObject obj, HandleId id,
HandleValue v, HandleValue receiver,
ObjectOpResult& result);
bool AddOrUpdateSparseElementHelper(JSContext* cx, Handle<NativeObject*> obj,
int32_t int_id, HandleValue v, bool strict);
/*
* Indicates whether an assignment operation is qualified (`x.y = 0`) or
* unqualified (`y = 0`). In strict mode, the latter is an error if no such
* variable already exists.
*
* Used as an argument to NativeSetProperty.
*/
enum QualifiedBool { Unqualified = 0, Qualified = 1 };
template <QualifiedBool Qualified>
extern bool NativeSetProperty(JSContext* cx, Handle<NativeObject*> obj,
HandleId id, HandleValue v, HandleValue receiver,
ObjectOpResult& result);
extern bool NativeSetElement(JSContext* cx, Handle<NativeObject*> obj,
uint32_t index, HandleValue v,
HandleValue receiver, ObjectOpResult& result);
extern bool NativeDeleteProperty(JSContext* cx, Handle<NativeObject*> obj,
HandleId id, ObjectOpResult& result);
/*** SpiderMonkey nonstandard internal methods ******************************/
template <AllowGC allowGC>
extern bool NativeLookupOwnProperty(
JSContext* cx, typename MaybeRooted<NativeObject*, allowGC>::HandleType obj,
typename MaybeRooted<jsid, allowGC>::HandleType id, PropertyResult* propp);
/*
* Get a property from `receiver`, after having already done a lookup and found
* the property on a native object `obj`.
*
* `prop` must be present in obj's shape.
*/
extern bool NativeGetExistingProperty(JSContext* cx, HandleObject receiver,
Handle<NativeObject*> obj, HandleId id,
PropertyInfo prop, MutableHandleValue vp);
/* * */
extern bool GetNameBoundInEnvironment(JSContext* cx, HandleObject env,
HandleId id, MutableHandleValue vp);
} /* namespace js */
template <>
inline bool JSObject::is<js::NativeObject>() const {
return shape()->isNative();
}
namespace js {
// Alternate to JSObject::as<NativeObject>() that tolerates null pointers.
inline NativeObject* MaybeNativeObject(JSObject* obj) {
return obj ? &obj->as<NativeObject>() : nullptr;
}
// Defined in NativeObject-inl.h.
bool IsPackedArray(JSObject* obj);
// Initialize an object's reserved slot with a private value pointing to
// malloc-allocated memory and associate the memory with the object.
//
// This call should be matched with a call to JS::GCContext::free_/delete_ in
// the object's finalizer to free the memory and update the memory accounting.
inline void InitReservedSlot(NativeObject* obj, uint32_t slot, void* ptr,
size_t nbytes, MemoryUse use) {
AddCellMemory(obj, nbytes, use);
obj->initReservedSlot(slot, PrivateValue(ptr));
}
template <typename T>
inline void InitReservedSlot(NativeObject* obj, uint32_t slot, T* ptr,
MemoryUse use) {
InitReservedSlot(obj, slot, ptr, sizeof(T), use);
}
bool AddSlotAndCallAddPropHook(JSContext* cx, Handle<NativeObject*> obj,
HandleValue v, Handle<Shape*> newShape);
} // namespace js
#endif /* vm_NativeObject_h */