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// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_ELEMENTS_H_
#define V8_ELEMENTS_H_
#include "src/elements-kind.h"
#include "src/heap/heap.h"
#include "src/isolate.h"
#include "src/keys.h"
#include "src/objects.h"
namespace v8 {
namespace internal {
// Abstract base class for handles that can operate on objects with differing
// ElementsKinds.
class ElementsAccessor {
explicit ElementsAccessor(const char* name) : name_(name) { }
virtual ~ElementsAccessor() { }
const char* name() const { return name_; }
// Returns a shared ElementsAccessor for the specified ElementsKind.
static ElementsAccessor* ForKind(ElementsKind elements_kind) {
DCHECK(static_cast<int>(elements_kind) < kElementsKindCount);
return elements_accessors_[elements_kind];
// Checks the elements of an object for consistency, asserting when a problem
// is found.
virtual void Validate(Handle<JSObject> obj) = 0;
// Returns true if a holder contains an element with the specified index
// without iterating up the prototype chain. The caller can optionally pass
// in the backing store to use for the check, which must be compatible with
// the ElementsKind of the ElementsAccessor. If backing_store is NULL, the
// holder->elements() is used as the backing store. If a |filter| is
// specified the PropertyAttributes of the element at the given index
// are compared to the given |filter|. If they match/overlap the given
// index is ignored. Note that only Dictionary elements have custom
// PropertyAttributes associated, hence the |filter| argument is ignored for
virtual bool HasElement(Handle<JSObject> holder, uint32_t index,
Handle<FixedArrayBase> backing_store,
PropertyFilter filter = ALL_PROPERTIES) = 0;
inline bool HasElement(Handle<JSObject> holder, uint32_t index,
PropertyFilter filter = ALL_PROPERTIES) {
return HasElement(holder, index, handle(holder->elements()), filter);
virtual Handle<Object> Get(Handle<JSObject> holder, uint32_t entry) = 0;
virtual PropertyDetails GetDetails(JSObject* holder, uint32_t entry) = 0;
virtual bool HasAccessors(JSObject* holder) = 0;
virtual uint32_t NumberOfElements(JSObject* holder) = 0;
// Modifies the length data property as specified for JSArrays and resizes the
// underlying backing store accordingly. The method honors the semantics of
// changing array sizes as defined in EcmaScript 5.1, i.e. array that
// have non-deletable elements can only be shrunk to the size of highest
// element that is non-deletable.
virtual void SetLength(Handle<JSArray> holder, uint32_t new_length) = 0;
// Deletes an element in an object.
virtual void Delete(Handle<JSObject> holder, uint32_t entry) = 0;
// If kCopyToEnd is specified as the copy_size to CopyElements, it copies all
// of elements from source after source_start to the destination array.
static const int kCopyToEnd = -1;
// If kCopyToEndAndInitializeToHole is specified as the copy_size to
// CopyElements, it copies all of elements from source after source_start to
// destination array, padding any remaining uninitialized elements in the
// destination array with the hole.
static const int kCopyToEndAndInitializeToHole = -2;
// Copy all indices that have elements from |object| into the given
// KeyAccumulator. For Dictionary-based element-kinds we filter out elements
// whose PropertyAttribute match |filter|.
virtual void CollectElementIndices(Handle<JSObject> object,
Handle<FixedArrayBase> backing_store,
KeyAccumulator* keys) = 0;
inline void CollectElementIndices(Handle<JSObject> object,
KeyAccumulator* keys) {
CollectElementIndices(object, handle(object->elements(), keys->isolate()),
virtual Maybe<bool> CollectValuesOrEntries(
Isolate* isolate, Handle<JSObject> object,
Handle<FixedArray> values_or_entries, bool get_entries, int* nof_items,
PropertyFilter filter = ALL_PROPERTIES) = 0;
virtual MaybeHandle<FixedArray> PrependElementIndices(
Handle<JSObject> object, Handle<FixedArrayBase> backing_store,
Handle<FixedArray> keys, GetKeysConversion convert,
PropertyFilter filter = ALL_PROPERTIES) = 0;
inline MaybeHandle<FixedArray> PrependElementIndices(
Handle<JSObject> object, Handle<FixedArray> keys,
GetKeysConversion convert, PropertyFilter filter = ALL_PROPERTIES) {
return PrependElementIndices(object, handle(object->elements()), keys,
convert, filter);
virtual void AddElementsToKeyAccumulator(Handle<JSObject> receiver,
KeyAccumulator* accumulator,
AddKeyConversion convert) = 0;
virtual void TransitionElementsKind(Handle<JSObject> object,
Handle<Map> map) = 0;
virtual void GrowCapacityAndConvert(Handle<JSObject> object,
uint32_t capacity) = 0;
// Unlike GrowCapacityAndConvert do not attempt to convert the backing store
// and simply return false in this case.
virtual bool GrowCapacity(Handle<JSObject> object, uint32_t index) = 0;
static void InitializeOncePerProcess();
static void TearDown();
virtual void Set(Handle<JSObject> holder, uint32_t entry, Object* value) = 0;
virtual void Reconfigure(Handle<JSObject> object,
Handle<FixedArrayBase> backing_store, uint32_t entry,
Handle<Object> value,
PropertyAttributes attributes) = 0;
virtual void Add(Handle<JSObject> object, uint32_t index,
Handle<Object> value, PropertyAttributes attributes,
uint32_t new_capacity) = 0;
static Handle<JSArray> Concat(Isolate* isolate, Arguments* args,
uint32_t concat_size, uint32_t result_length);
virtual uint32_t Push(Handle<JSArray> receiver, Arguments* args,
uint32_t push_size) = 0;
virtual uint32_t Unshift(Handle<JSArray> receiver,
Arguments* args, uint32_t unshift_size) = 0;
virtual Handle<JSArray> Slice(Handle<JSObject> receiver,
uint32_t start, uint32_t end) = 0;
virtual Handle<JSArray> Splice(Handle<JSArray> receiver,
uint32_t start, uint32_t delete_count,
Arguments* args, uint32_t add_count) = 0;
virtual Handle<Object> Pop(Handle<JSArray> receiver) = 0;
virtual Handle<Object> Shift(Handle<JSArray> receiver) = 0;
virtual Handle<SeededNumberDictionary> Normalize(Handle<JSObject> object) = 0;
virtual uint32_t GetCapacity(JSObject* holder,
FixedArrayBase* backing_store) = 0;
// Check an Object's own elements for an element (using SameValueZero
// semantics)
virtual Maybe<bool> IncludesValue(Isolate* isolate, Handle<JSObject> receiver,
Handle<Object> value, uint32_t start,
uint32_t length) = 0;
// Check an Object's own elements for the index of an element (using SameValue
// semantics)
virtual Maybe<int64_t> IndexOfValue(Isolate* isolate,
Handle<JSObject> receiver,
Handle<Object> value, uint32_t start,
uint32_t length) = 0;
virtual void CopyElements(Handle<FixedArrayBase> source,
ElementsKind source_kind,
Handle<FixedArrayBase> destination, int size) = 0;
virtual Handle<FixedArray> CreateListFromArray(Isolate* isolate,
Handle<JSArray> array) = 0;
friend class LookupIterator;
// Element handlers distinguish between entries and indices when they
// manipulate elements. Entries refer to elements in terms of their location
// in the underlying storage's backing store representation, and are between 0
// and GetCapacity. Indices refer to elements in terms of the value that would
// be specified in JavaScript to access the element. In most implementations,
// indices are equivalent to entries. In the NumberDictionary
// ElementsAccessor, entries are mapped to an index using the KeyAt method on
// the NumberDictionary.
virtual uint32_t GetEntryForIndex(Isolate* isolate, JSObject* holder,
FixedArrayBase* backing_store,
uint32_t index) = 0;
// NOTE: this method violates the handlified function signature convention:
// raw pointer parameter |source_holder| in the function that allocates.
// This is done intentionally to avoid ArrayConcat() builtin performance
// degradation.
virtual void CopyElements(JSObject* source_holder, uint32_t source_start,
ElementsKind source_kind,
Handle<FixedArrayBase> destination,
uint32_t destination_start, int copy_size) = 0;
static ElementsAccessor** elements_accessors_;
const char* name_;
void CheckArrayAbuse(Handle<JSObject> obj, const char* op, uint32_t index,
bool allow_appending = false);
MUST_USE_RESULT MaybeHandle<Object> ArrayConstructInitializeElements(
Handle<JSArray> array,
Arguments* args);
} // namespace internal
} // namespace v8
#endif // V8_ELEMENTS_H_