1// Copyright 2012 the V8 project authors. All rights reserved.
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3// modification, are permitted provided that the following conditions are
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27
28#ifndef V8_ELEMENTS_H_
29#define V8_ELEMENTS_H_
30
31#include "elements-kind.h"
32#include "objects.h"
33#include "heap.h"
34#include "isolate.h"
35
36namespace v8 {
37namespace internal {
38
39// Abstract base class for handles that can operate on objects with differing
40// ElementsKinds.
41class ElementsAccessor {
42 public:
43  explicit ElementsAccessor(const char* name) : name_(name) { }
44  virtual ~ElementsAccessor() { }
45
46  virtual ElementsKind kind() const = 0;
47  const char* name() const { return name_; }
48
49  // Checks the elements of an object for consistency, asserting when a problem
50  // is found.
51  virtual void Validate(JSObject* obj) = 0;
52
53  // Returns true if a holder contains an element with the specified key
54  // without iterating up the prototype chain.  The caller can optionally pass
55  // in the backing store to use for the check, which must be compatible with
56  // the ElementsKind of the ElementsAccessor. If backing_store is NULL, the
57  // holder->elements() is used as the backing store.
58  virtual bool HasElement(Object* receiver,
59                          JSObject* holder,
60                          uint32_t key,
61                          FixedArrayBase* backing_store = NULL) = 0;
62
63  // Returns the element with the specified key or undefined if there is no such
64  // element. This method doesn't iterate up the prototype chain.  The caller
65  // can optionally pass in the backing store to use for the check, which must
66  // be compatible with the ElementsKind of the ElementsAccessor. If
67  // backing_store is NULL, the holder->elements() is used as the backing store.
68  MUST_USE_RESULT virtual MaybeObject* Get(
69      Object* receiver,
70      JSObject* holder,
71      uint32_t key,
72      FixedArrayBase* backing_store = NULL) = 0;
73
74  // Returns an element's attributes, or ABSENT if there is no such
75  // element. This method doesn't iterate up the prototype chain.  The caller
76  // can optionally pass in the backing store to use for the check, which must
77  // be compatible with the ElementsKind of the ElementsAccessor. If
78  // backing_store is NULL, the holder->elements() is used as the backing store.
79  MUST_USE_RESULT virtual PropertyAttributes GetAttributes(
80      Object* receiver,
81      JSObject* holder,
82      uint32_t key,
83      FixedArrayBase* backing_store = NULL) = 0;
84
85  // Returns an element's type, or NONEXISTENT if there is no such
86  // element. This method doesn't iterate up the prototype chain.  The caller
87  // can optionally pass in the backing store to use for the check, which must
88  // be compatible with the ElementsKind of the ElementsAccessor. If
89  // backing_store is NULL, the holder->elements() is used as the backing store.
90  MUST_USE_RESULT virtual PropertyType GetType(
91      Object* receiver,
92      JSObject* holder,
93      uint32_t key,
94      FixedArrayBase* backing_store = NULL) = 0;
95
96  // Returns an element's accessors, or NULL if the element does not exist or
97  // is plain. This method doesn't iterate up the prototype chain.  The caller
98  // can optionally pass in the backing store to use for the check, which must
99  // be compatible with the ElementsKind of the ElementsAccessor. If
100  // backing_store is NULL, the holder->elements() is used as the backing store.
101  MUST_USE_RESULT virtual AccessorPair* GetAccessorPair(
102      Object* receiver,
103      JSObject* holder,
104      uint32_t key,
105      FixedArrayBase* backing_store = NULL) = 0;
106
107  // Modifies the length data property as specified for JSArrays and resizes the
108  // underlying backing store accordingly. The method honors the semantics of
109  // changing array sizes as defined in EcmaScript 5.1 15.4.5.2, i.e. array that
110  // have non-deletable elements can only be shrunk to the size of highest
111  // element that is non-deletable.
112  MUST_USE_RESULT virtual MaybeObject* SetLength(JSArray* holder,
113                                                 Object* new_length) = 0;
114
115  // Modifies both the length and capacity of a JSArray, resizing the underlying
116  // backing store as necessary. This method does NOT honor the semantics of
117  // EcmaScript 5.1 15.4.5.2, arrays can be shrunk beyond non-deletable
118  // elements. This method should only be called for array expansion OR by
119  // runtime JavaScript code that use InternalArrays and don't care about
120  // EcmaScript 5.1 semantics.
121  MUST_USE_RESULT virtual MaybeObject* SetCapacityAndLength(JSArray* array,
122                                                            int capacity,
123                                                            int length) = 0;
124
125  // Deletes an element in an object, returning a new elements backing store.
126  MUST_USE_RESULT virtual MaybeObject* Delete(JSObject* holder,
127                                              uint32_t key,
128                                              JSReceiver::DeleteMode mode) = 0;
129
130  // If kCopyToEnd is specified as the copy_size to CopyElements, it copies all
131  // of elements from source after source_start to the destination array.
132  static const int kCopyToEnd = -1;
133  // If kCopyToEndAndInitializeToHole is specified as the copy_size to
134  // CopyElements, it copies all of elements from source after source_start to
135  // destination array, padding any remaining uninitialized elements in the
136  // destination array with the hole.
137  static const int kCopyToEndAndInitializeToHole = -2;
138
139  // Copy elements from one backing store to another. Typically, callers specify
140  // the source JSObject or JSArray in source_holder. If the holder's backing
141  // store is available, it can be passed in source and source_holder is
142  // ignored.
143  MUST_USE_RESULT virtual MaybeObject* CopyElements(
144      JSObject* source_holder,
145      uint32_t source_start,
146      ElementsKind source_kind,
147      FixedArrayBase* destination,
148      uint32_t destination_start,
149      int copy_size,
150      FixedArrayBase* source = NULL) = 0;
151
152  MUST_USE_RESULT MaybeObject* CopyElements(JSObject* from_holder,
153                                            FixedArrayBase* to,
154                                            ElementsKind from_kind,
155                                            FixedArrayBase* from = NULL) {
156    return CopyElements(from_holder, 0, from_kind, to, 0,
157                        kCopyToEndAndInitializeToHole, from);
158  }
159
160  MUST_USE_RESULT virtual MaybeObject* AddElementsToFixedArray(
161      Object* receiver,
162      JSObject* holder,
163      FixedArray* to,
164      FixedArrayBase* from = NULL) = 0;
165
166  // Returns a shared ElementsAccessor for the specified ElementsKind.
167  static ElementsAccessor* ForKind(ElementsKind elements_kind) {
168    ASSERT(elements_kind < kElementsKindCount);
169    return elements_accessors_[elements_kind];
170  }
171
172  static ElementsAccessor* ForArray(FixedArrayBase* array);
173
174  static void InitializeOncePerProcess();
175  static void TearDown();
176
177 protected:
178  friend class NonStrictArgumentsElementsAccessor;
179
180  virtual uint32_t GetCapacity(FixedArrayBase* backing_store) = 0;
181
182  // Element handlers distinguish between indexes and keys when they manipulate
183  // elements.  Indexes refer to elements in terms of their location in the
184  // underlying storage's backing store representation, and are between 0 and
185  // GetCapacity.  Keys refer to elements in terms of the value that would be
186  // specified in JavaScript to access the element. In most implementations,
187  // keys are equivalent to indexes, and GetKeyForIndex returns the same value
188  // it is passed. In the NumberDictionary ElementsAccessor, GetKeyForIndex maps
189  // the index to a key using the KeyAt method on the NumberDictionary.
190  virtual uint32_t GetKeyForIndex(FixedArrayBase* backing_store,
191                                  uint32_t index) = 0;
192
193 private:
194  static ElementsAccessor** elements_accessors_;
195  const char* name_;
196
197  DISALLOW_COPY_AND_ASSIGN(ElementsAccessor);
198};
199
200void CheckArrayAbuse(JSObject* obj, const char* op, uint32_t key,
201                     bool allow_appending = false);
202
203MUST_USE_RESULT MaybeObject* ArrayConstructInitializeElements(
204    JSArray* array, Arguments* args);
205
206} }  // namespace v8::internal
207
208#endif  // V8_ELEMENTS_H_
209