f4872f7477
String wrappers (new String("foo")) are special objects: their string
characters are accessed like elements, and they also have an elements
backing store. This used to require a bunch of explicit checks like:
if (obj->IsJSValue() && JSValue::cast(obj)->value()->IsString()) {
/* Handle string characters */
}
// Handle regular elements (for string wrappers and other objects)
obj->GetElementsAccessor()->Whatever(...);
This CL introduces new ElementsKinds for string wrapper objects (one for
fast elements, one for dictionary elements), which allow folding the
special-casing into new StringWrapperElementsAccessors.
No observable change in behavior is intended.
Review URL: https://codereview.chromium.org/1612323003
Cr-Commit-Position: refs/heads/master@{#33616}
193 lines
8.5 KiB
C++
193 lines
8.5 KiB
C++
// Copyright 2012 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef V8_ELEMENTS_H_
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#define V8_ELEMENTS_H_
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#include "src/elements-kind.h"
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#include "src/heap/heap.h"
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#include "src/isolate.h"
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#include "src/key-accumulator.h"
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#include "src/objects.h"
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namespace v8 {
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namespace internal {
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// Abstract base class for handles that can operate on objects with differing
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// ElementsKinds.
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class ElementsAccessor {
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public:
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explicit ElementsAccessor(const char* name) : name_(name) { }
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virtual ~ElementsAccessor() { }
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const char* name() const { return name_; }
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// Returns a shared ElementsAccessor for the specified ElementsKind.
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static ElementsAccessor* ForKind(ElementsKind elements_kind) {
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DCHECK(static_cast<int>(elements_kind) < kElementsKindCount);
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return elements_accessors_[elements_kind];
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}
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// Checks the elements of an object for consistency, asserting when a problem
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// is found.
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virtual void Validate(Handle<JSObject> obj) = 0;
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// Returns true if a holder contains an element with the specified index
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// without iterating up the prototype chain. The caller can optionally pass
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// in the backing store to use for the check, which must be compatible with
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// the ElementsKind of the ElementsAccessor. If backing_store is NULL, the
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// holder->elements() is used as the backing store. If a |filter| is
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// specified the PropertyAttributes of the element at the given index
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// are compared to the given |filter|. If they match/overlap the given
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// index is ignored. Note that only Dictionary elements have custom
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// PropertyAttributes associated, hence the |filter| argument is ignored for
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// all but DICTIONARY_ELEMENTS and SLOW_SLOPPY_ARGUMENTS_ELEMENTS.
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virtual bool HasElement(Handle<JSObject> holder, uint32_t index,
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Handle<FixedArrayBase> backing_store,
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PropertyFilter filter = ALL_PROPERTIES) = 0;
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inline bool HasElement(Handle<JSObject> holder, uint32_t index,
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PropertyFilter filter = ALL_PROPERTIES) {
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return HasElement(holder, index, handle(holder->elements()), filter);
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}
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// Returns true if the backing store is compact in the given range
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virtual bool IsPacked(Handle<JSObject> holder,
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Handle<FixedArrayBase> backing_store, uint32_t start,
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uint32_t end) = 0;
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virtual Handle<Object> Get(Handle<JSObject> holder, uint32_t entry) = 0;
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virtual PropertyDetails GetDetails(JSObject* holder, uint32_t entry) = 0;
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// Modifies the length data property as specified for JSArrays and resizes the
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// underlying backing store accordingly. The method honors the semantics of
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// changing array sizes as defined in EcmaScript 5.1 15.4.5.2, i.e. array that
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// have non-deletable elements can only be shrunk to the size of highest
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// element that is non-deletable.
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virtual void SetLength(Handle<JSArray> holder, uint32_t new_length) = 0;
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// Deletes an element in an object.
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virtual void Delete(Handle<JSObject> holder, uint32_t entry) = 0;
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// If kCopyToEnd is specified as the copy_size to CopyElements, it copies all
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// of elements from source after source_start to the destination array.
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static const int kCopyToEnd = -1;
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// If kCopyToEndAndInitializeToHole is specified as the copy_size to
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// CopyElements, it copies all of elements from source after source_start to
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// destination array, padding any remaining uninitialized elements in the
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// destination array with the hole.
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static const int kCopyToEndAndInitializeToHole = -2;
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// Copy all indices that have elements from |object| into the given
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// KeyAccumulator. For Dictionary-based element-kinds we filter out elements
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// whose PropertyAttribute match |filter|.
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virtual void CollectElementIndices(Handle<JSObject> object,
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Handle<FixedArrayBase> backing_store,
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KeyAccumulator* keys,
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uint32_t range = kMaxUInt32,
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PropertyFilter filter = ALL_PROPERTIES,
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uint32_t offset = 0) = 0;
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inline void CollectElementIndices(Handle<JSObject> object,
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KeyAccumulator* keys,
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uint32_t range = kMaxUInt32,
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PropertyFilter filter = ALL_PROPERTIES,
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uint32_t offset = 0) {
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CollectElementIndices(object, handle(object->elements()), keys, range,
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filter, offset);
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}
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virtual void AddElementsToKeyAccumulator(Handle<JSObject> receiver,
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KeyAccumulator* accumulator,
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AddKeyConversion convert) = 0;
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virtual void GrowCapacityAndConvert(Handle<JSObject> object,
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uint32_t capacity) = 0;
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static void InitializeOncePerProcess();
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static void TearDown();
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virtual void Set(Handle<JSObject> holder, uint32_t entry, Object* value) = 0;
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virtual void Reconfigure(Handle<JSObject> object,
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Handle<FixedArrayBase> backing_store, uint32_t entry,
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Handle<Object> value,
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PropertyAttributes attributes) = 0;
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virtual void Add(Handle<JSObject> object, uint32_t index,
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Handle<Object> value, PropertyAttributes attributes,
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uint32_t new_capacity) = 0;
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static Handle<JSArray> Concat(Isolate* isolate, Arguments* args,
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uint32_t concat_size);
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virtual uint32_t Push(Handle<JSArray> receiver,
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Handle<FixedArrayBase> backing_store, Arguments* args,
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uint32_t push_size) = 0;
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virtual uint32_t Unshift(Handle<JSArray> receiver,
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Handle<FixedArrayBase> backing_store,
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Arguments* args, uint32_t unshift_size) = 0;
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virtual Handle<JSArray> Slice(Handle<JSObject> receiver,
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Handle<FixedArrayBase> backing_store,
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uint32_t start, uint32_t end) = 0;
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virtual Handle<JSArray> Splice(Handle<JSArray> receiver,
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Handle<FixedArrayBase> backing_store,
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uint32_t start, uint32_t delete_count,
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Arguments* args, uint32_t add_count) = 0;
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virtual Handle<Object> Pop(Handle<JSArray> receiver,
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Handle<FixedArrayBase> backing_store) = 0;
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virtual Handle<Object> Shift(Handle<JSArray> receiver,
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Handle<FixedArrayBase> backing_store) = 0;
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protected:
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friend class LookupIterator;
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// Element handlers distinguish between entries and indices when they
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// manipulate elements. Entries refer to elements in terms of their location
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// in the underlying storage's backing store representation, and are between 0
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// and GetCapacity. Indices refer to elements in terms of the value that would
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// be specified in JavaScript to access the element. In most implementations,
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// indices are equivalent to entries. In the NumberDictionary
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// ElementsAccessor, entries are mapped to an index using the KeyAt method on
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// the NumberDictionary.
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virtual uint32_t GetEntryForIndex(JSObject* holder,
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FixedArrayBase* backing_store,
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uint32_t index) = 0;
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// NOTE: this method violates the handlified function signature convention:
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// raw pointer parameter |source_holder| in the function that allocates.
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// This is done intentionally to avoid ArrayConcat() builtin performance
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// degradation.
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virtual void CopyElements(JSObject* source_holder, uint32_t source_start,
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ElementsKind source_kind,
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Handle<FixedArrayBase> destination,
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uint32_t destination_start, int copy_size) = 0;
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private:
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virtual uint32_t GetCapacity(JSObject* holder,
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FixedArrayBase* backing_store) = 0;
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static ElementsAccessor** elements_accessors_;
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const char* name_;
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DISALLOW_COPY_AND_ASSIGN(ElementsAccessor);
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};
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void CheckArrayAbuse(Handle<JSObject> obj, const char* op, uint32_t index,
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bool allow_appending = false);
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MUST_USE_RESULT MaybeHandle<Object> ArrayConstructInitializeElements(
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Handle<JSArray> array,
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Arguments* args);
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} // namespace internal
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} // namespace v8
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#endif // V8_ELEMENTS_H_
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