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1 // Copyright 2012 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #ifndef V8_ELEMENTS_H_
6 #define V8_ELEMENTS_H_
7 
8 #include "src/elements-kind.h"
9 #include "src/keys.h"
10 #include "src/objects.h"
11 
12 namespace v8 {
13 namespace internal {
14 
15 class JSTypedArray;
16 
17 // Abstract base class for handles that can operate on objects with differing
18 // ElementsKinds.
19 class ElementsAccessor {
20  public:
ElementsAccessor(const char * name)21   explicit ElementsAccessor(const char* name) : name_(name) { }
~ElementsAccessor()22   virtual ~ElementsAccessor() { }
23 
name()24   const char* name() const { return name_; }
25 
26   // Returns a shared ElementsAccessor for the specified ElementsKind.
ForKind(ElementsKind elements_kind)27   static ElementsAccessor* ForKind(ElementsKind elements_kind) {
28     DCHECK_LT(static_cast<int>(elements_kind), kElementsKindCount);
29     return elements_accessors_[elements_kind];
30   }
31 
32   // Checks the elements of an object for consistency, asserting when a problem
33   // is found.
34   virtual void Validate(JSObject* obj) = 0;
35 
36   // Returns true if a holder contains an element with the specified index
37   // without iterating up the prototype chain.  The caller can optionally pass
38   // in the backing store to use for the check, which must be compatible with
39   // the ElementsKind of the ElementsAccessor. If backing_store is nullptr, the
40   // holder->elements() is used as the backing store. If a |filter| is
41   // specified the PropertyAttributes of the element at the given index
42   // are compared to the given |filter|. If they match/overlap the given
43   // index is ignored. Note that only Dictionary elements have custom
44   // PropertyAttributes associated, hence the |filter| argument is ignored for
45   // all but DICTIONARY_ELEMENTS and SLOW_SLOPPY_ARGUMENTS_ELEMENTS.
46   virtual bool HasElement(JSObject* holder, uint32_t index,
47                           FixedArrayBase* backing_store,
48                           PropertyFilter filter = ALL_PROPERTIES) = 0;
49 
50   inline bool HasElement(JSObject* holder, uint32_t index,
51                          PropertyFilter filter = ALL_PROPERTIES);
52 
53   // Note: this is currently not implemented for string wrapper and
54   // typed array elements.
55   virtual bool HasEntry(JSObject* holder, uint32_t entry) = 0;
56 
57   // TODO(cbruni): HasEntry and Get should not be exposed publicly with the
58   // entry parameter.
59   virtual Handle<Object> Get(Handle<JSObject> holder, uint32_t entry) = 0;
60 
61   virtual bool HasAccessors(JSObject* holder) = 0;
62   virtual uint32_t NumberOfElements(JSObject* holder) = 0;
63 
64   // Modifies the length data property as specified for JSArrays and resizes the
65   // underlying backing store accordingly. The method honors the semantics of
66   // changing array sizes as defined in EcmaScript 5.1 15.4.5.2, i.e. array that
67   // have non-deletable elements can only be shrunk to the size of highest
68   // element that is non-deletable.
69   virtual void SetLength(Handle<JSArray> holder, uint32_t new_length) = 0;
70 
71 
72   // If kCopyToEnd is specified as the copy_size to CopyElements, it copies all
73   // of elements from source after source_start to the destination array.
74   static const int kCopyToEnd = -1;
75   // If kCopyToEndAndInitializeToHole is specified as the copy_size to
76   // CopyElements, it copies all of elements from source after source_start to
77   // destination array, padding any remaining uninitialized elements in the
78   // destination array with the hole.
79   static const int kCopyToEndAndInitializeToHole = -2;
80 
81   // Copy all indices that have elements from |object| into the given
82   // KeyAccumulator. For Dictionary-based element-kinds we filter out elements
83   // whose PropertyAttribute match |filter|.
84   virtual void CollectElementIndices(Handle<JSObject> object,
85                                      Handle<FixedArrayBase> backing_store,
86                                      KeyAccumulator* keys) = 0;
87 
88   inline void CollectElementIndices(Handle<JSObject> object,
89                                     KeyAccumulator* keys);
90 
91   virtual Maybe<bool> CollectValuesOrEntries(
92       Isolate* isolate, Handle<JSObject> object,
93       Handle<FixedArray> values_or_entries, bool get_entries, int* nof_items,
94       PropertyFilter filter = ALL_PROPERTIES) = 0;
95 
96   virtual MaybeHandle<FixedArray> PrependElementIndices(
97       Handle<JSObject> object, Handle<FixedArrayBase> backing_store,
98       Handle<FixedArray> keys, GetKeysConversion convert,
99       PropertyFilter filter = ALL_PROPERTIES) = 0;
100 
101   inline MaybeHandle<FixedArray> PrependElementIndices(
102       Handle<JSObject> object, Handle<FixedArray> keys,
103       GetKeysConversion convert, PropertyFilter filter = ALL_PROPERTIES);
104 
105   virtual void AddElementsToKeyAccumulator(Handle<JSObject> receiver,
106                                            KeyAccumulator* accumulator,
107                                            AddKeyConversion convert) = 0;
108 
109   virtual void TransitionElementsKind(Handle<JSObject> object,
110                                       Handle<Map> map) = 0;
111   virtual void GrowCapacityAndConvert(Handle<JSObject> object,
112                                       uint32_t capacity) = 0;
113   // Unlike GrowCapacityAndConvert do not attempt to convert the backing store
114   // and simply return false in this case.
115   virtual bool GrowCapacity(Handle<JSObject> object, uint32_t index) = 0;
116 
117   static void InitializeOncePerProcess();
118   static void TearDown();
119 
120   virtual void Set(Handle<JSObject> holder, uint32_t entry, Object* value) = 0;
121 
122   virtual void Add(Handle<JSObject> object, uint32_t index,
123                    Handle<Object> value, PropertyAttributes attributes,
124                    uint32_t new_capacity) = 0;
125 
126   static Handle<JSArray> Concat(Isolate* isolate, Arguments* args,
127                                 uint32_t concat_size, uint32_t result_length);
128 
129   virtual uint32_t Push(Handle<JSArray> receiver, Arguments* args,
130                         uint32_t push_size) = 0;
131 
132   virtual uint32_t Unshift(Handle<JSArray> receiver, Arguments* args,
133                            uint32_t unshift_size) = 0;
134 
135   virtual Handle<JSObject> Slice(Handle<JSObject> receiver, uint32_t start,
136                                  uint32_t end) = 0;
137 
138   virtual Handle<JSArray> Splice(Handle<JSArray> receiver,
139                                  uint32_t start, uint32_t delete_count,
140                                  Arguments* args, uint32_t add_count) = 0;
141 
142   virtual Handle<Object> Pop(Handle<JSArray> receiver) = 0;
143 
144   virtual Handle<Object> Shift(Handle<JSArray> receiver) = 0;
145 
146   virtual Handle<NumberDictionary> Normalize(Handle<JSObject> object) = 0;
147 
148   virtual uint32_t GetCapacity(JSObject* holder,
149                                FixedArrayBase* backing_store) = 0;
150 
151   virtual Object* Fill(Handle<JSObject> receiver, Handle<Object> obj_value,
152                        uint32_t start, uint32_t end) = 0;
153 
154   // Check an Object's own elements for an element (using SameValueZero
155   // semantics)
156   virtual Maybe<bool> IncludesValue(Isolate* isolate, Handle<JSObject> receiver,
157                                     Handle<Object> value, uint32_t start,
158                                     uint32_t length) = 0;
159 
160   // Check an Object's own elements for the index of an element (using SameValue
161   // semantics)
162   virtual Maybe<int64_t> IndexOfValue(Isolate* isolate,
163                                       Handle<JSObject> receiver,
164                                       Handle<Object> value, uint32_t start,
165                                       uint32_t length) = 0;
166 
167   virtual Maybe<int64_t> LastIndexOfValue(Handle<JSObject> receiver,
168                                           Handle<Object> value,
169                                           uint32_t start) = 0;
170 
171   virtual void Reverse(JSObject* receiver) = 0;
172 
173   virtual void CopyElements(Isolate* isolate, Handle<FixedArrayBase> source,
174                             ElementsKind source_kind,
175                             Handle<FixedArrayBase> destination, int size) = 0;
176 
177   virtual Object* CopyElements(Handle<Object> source,
178                                Handle<JSObject> destination, size_t length,
179                                uint32_t offset = 0) = 0;
180 
181   virtual Handle<FixedArray> CreateListFromArrayLike(Isolate* isolate,
182                                                      Handle<JSObject> object,
183                                                      uint32_t length) = 0;
184 
185   virtual void CopyTypedArrayElementsSlice(JSTypedArray* source,
186                                            JSTypedArray* destination,
187                                            size_t start, size_t end) = 0;
188 
189  protected:
190   friend class LookupIterator;
191 
192   // Element handlers distinguish between entries and indices when they
193   // manipulate elements. Entries refer to elements in terms of their location
194   // in the underlying storage's backing store representation, and are between 0
195   // and GetCapacity. Indices refer to elements in terms of the value that would
196   // be specified in JavaScript to access the element. In most implementations,
197   // indices are equivalent to entries. In the NumberDictionary
198   // ElementsAccessor, entries are mapped to an index using the KeyAt method on
199   // the NumberDictionary.
200   virtual uint32_t GetEntryForIndex(Isolate* isolate, JSObject* holder,
201                                     FixedArrayBase* backing_store,
202                                     uint32_t index) = 0;
203 
204   virtual PropertyDetails GetDetails(JSObject* holder, uint32_t entry) = 0;
205   virtual void Reconfigure(Handle<JSObject> object,
206                            Handle<FixedArrayBase> backing_store, uint32_t entry,
207                            Handle<Object> value,
208                            PropertyAttributes attributes) = 0;
209 
210   // Deletes an element in an object.
211   virtual void Delete(Handle<JSObject> holder, uint32_t entry) = 0;
212 
213   // NOTE: this method violates the handlified function signature convention:
214   // raw pointer parameter |source_holder| in the function that allocates.
215   // This is done intentionally to avoid ArrayConcat() builtin performance
216   // degradation.
217   virtual void CopyElements(JSObject* source_holder, uint32_t source_start,
218                             ElementsKind source_kind,
219                             Handle<FixedArrayBase> destination,
220                             uint32_t destination_start, int copy_size) = 0;
221 
222  private:
223   static ElementsAccessor** elements_accessors_;
224   const char* name_;
225 
226   DISALLOW_COPY_AND_ASSIGN(ElementsAccessor);
227 };
228 
229 void CheckArrayAbuse(Handle<JSObject> obj, const char* op, uint32_t index,
230                      bool allow_appending = false);
231 
232 V8_WARN_UNUSED_RESULT MaybeHandle<Object> ArrayConstructInitializeElements(
233     Handle<JSArray> array, Arguments* args);
234 
235 // Called directly from CSA.
236 void CopyFastNumberJSArrayElementsToTypedArray(Context* context,
237                                                JSArray* source,
238                                                JSTypedArray* destination,
239                                                uintptr_t length,
240                                                uintptr_t offset);
241 void CopyTypedArrayElementsToTypedArray(JSTypedArray* source,
242                                         JSTypedArray* destination,
243                                         uintptr_t length, uintptr_t offset);
244 void CopyTypedArrayElementsSlice(JSTypedArray* source,
245                                  JSTypedArray* destination, uintptr_t start,
246                                  uintptr_t end);
247 
248 }  // namespace internal
249 }  // namespace v8
250 
251 #endif  // V8_ELEMENTS_H_
252