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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/objects.h"
namespace v8 {
namespace internal {
// Abstract base class for handles that can operate on objects with differing
// ElementsKinds.
class ElementsAccessor {
public:
explicit ElementsAccessor(const char* name) : name_(name) { }
virtual ~ElementsAccessor() { }
const char* name() const { return name_; }
// 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.
virtual bool HasElement(Handle<JSObject> holder, uint32_t index,
Handle<FixedArrayBase> backing_store) = 0;
inline bool HasElement(Handle<JSObject> holder, uint32_t index) {
return HasElement(holder, index, handle(holder->elements()));
}
// Returns the element with the specified index or undefined if there is no
// such element. This method doesn't iterate 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.
virtual Handle<Object> Get(Handle<JSObject> holder, uint32_t index,
Handle<FixedArrayBase> backing_store) = 0;
inline Handle<Object> Get(Handle<JSObject> holder, uint32_t index) {
return Get(holder, index, handle(holder->elements()));
}
// 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 15.4.5.2, 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 elements from one backing store to another. Typically, callers specify
// the source JSObject or JSArray in source_holder. If the holder's backing
// store is available, it can be passed in source and source_holder is
// ignored.
virtual void CopyElements(
Handle<FixedArrayBase> source,
uint32_t source_start,
ElementsKind source_kind,
Handle<FixedArrayBase> destination,
uint32_t destination_start,
int copy_size) = 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;
inline void CopyElements(
Handle<JSObject> from_holder,
Handle<FixedArrayBase> to,
ElementsKind from_kind) {
CopyElements(
*from_holder, 0, from_kind, to, 0, kCopyToEndAndInitializeToHole);
}
virtual void GrowCapacityAndConvert(Handle<JSObject> object,
uint32_t capacity) = 0;
virtual Handle<FixedArray> AddElementsToFixedArray(
Handle<JSObject> receiver, Handle<FixedArray> to,
FixedArray::KeyFilter filter) = 0;
// 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];
}
static ElementsAccessor* ForArray(Handle<FixedArrayBase> array);
static void InitializeOncePerProcess();
static void TearDown();
virtual void Set(FixedArrayBase* backing_store, uint32_t index,
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 entry,
Handle<Object> value, PropertyAttributes attributes,
uint32_t new_capacity) = 0;
protected:
friend class LookupIterator;
static ElementsAccessor* ForArray(FixedArrayBase* array);
virtual uint32_t GetCapacity(JSObject* holder,
FixedArrayBase* backing_store) = 0;
// 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(JSObject* holder,
FixedArrayBase* backing_store,
uint32_t index) = 0;
virtual PropertyDetails GetDetails(FixedArrayBase* backing_store,
uint32_t entry) = 0;
private:
static ElementsAccessor** elements_accessors_;
const char* name_;
DISALLOW_COPY_AND_ASSIGN(ElementsAccessor);
};
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 v8::internal
#endif // V8_ELEMENTS_H_
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