// Copyright 2012 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following
// disclaimer in the documentation and/or other materials provided
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// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
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//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef V8_ELEMENTS_H_
#define V8_ELEMENTS_H_
#include "objects.h"
#include "heap.h"
#include "isolate.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() { }
virtual ElementsKind kind() const = 0;
const char* name() const { return name_; }
// Returns true if a holder contains an element with the specified key
// 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(Object* receiver,
JSObject* holder,
uint32_t key,
FixedArrayBase* backing_store = NULL) = 0;
// Returns the element with the specified key 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 MaybeObject* Get(Object* receiver,
JSObject* holder,
uint32_t key,
FixedArrayBase* backing_store = NULL) = 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 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 MaybeObject* SetLength(JSArray* holder,
Object* new_length) = 0;
// Modifies both the length and capacity of a JSArray, resizing the underlying
// backing store as necessary. This method does NOT honor the semantics of
// EcmaScript 5.1 15.4.5.2, arrays can be shrunk beyond non-deletable
// elements. This method should only be called for array expansion OR by
// runtime JavaScript code that use InternalArrays and don't care about
// EcmaScript 5.1 semantics.
virtual MaybeObject* SetCapacityAndLength(JSArray* array,
int capacity,
int length) = 0;
// Deletes an element in an object, returning a new elements backing store.
virtual MaybeObject* Delete(JSObject* holder,
uint32_t key,
JSReceiver::DeleteMode mode) = 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 MaybeObject* CopyElements(JSObject* source_holder,
uint32_t source_start,
FixedArrayBase* destination,
ElementsKind destination_kind,
uint32_t destination_start,
int copy_size,
FixedArrayBase* source = NULL) = 0;
MaybeObject* CopyElements(JSObject* from_holder,
FixedArrayBase* to,
ElementsKind to_kind,
FixedArrayBase* from = NULL) {
return CopyElements(from_holder, 0, to, to_kind, 0,
kCopyToEndAndInitializeToHole, from);
}
virtual MaybeObject* AddElementsToFixedArray(Object* receiver,
JSObject* holder,
FixedArray* to,
FixedArrayBase* from = NULL) = 0;
// Returns a shared ElementsAccessor for the specified ElementsKind.
static ElementsAccessor* ForKind(ElementsKind elements_kind) {
ASSERT(elements_kind < kElementsKindCount);
return elements_accessors_[elements_kind];
}
static ElementsAccessor* ForArray(FixedArrayBase* array);
static void InitializeOncePerProcess();
protected:
friend class NonStrictArgumentsElementsAccessor;
virtual uint32_t GetCapacity(FixedArrayBase* backing_store) = 0;
// Element handlers distinguish between indexes and keys when they manipulate
// elements. Indexes refer to elements in terms of their location in the
// underlying storage's backing store representation, and are between 0 and
// GetCapacity. Keys refer to elements in terms of the value that would be
// specified in JavaScript to access the element. In most implementations,
// keys are equivalent to indexes, and GetKeyForIndex returns the same value
// it is passed. In the NumberDictionary ElementsAccessor, GetKeyForIndex maps
// the index to a key using the KeyAt method on the NumberDictionary.
virtual uint32_t GetKeyForIndex(FixedArrayBase* backing_store,
uint32_t index) = 0;
private:
static ElementsAccessor** elements_accessors_;
const char* name_;
DISALLOW_COPY_AND_ASSIGN(ElementsAccessor);
};
void CopyObjectToObjectElements(FixedArray* from_obj,
ElementsKind from_kind,
uint32_t from_start,
FixedArray* to_obj,
ElementsKind to_kind,
uint32_t to_start,
int copy_size);
} } // namespace v8::internal
#endif // V8_ELEMENTS_H_