property.h revision 5913587db4c6bab03d97bfe44b06289fd6d7270d 
1// Copyright 2006-2008 the V8 project authors. All rights reserved.
2// Redistribution and use in source and binary forms, with or without
3// modification, are permitted provided that the following conditions are
4// met:
5//
6//     * Redistributions of source code must retain the above copyright
7//       notice, this list of conditions and the following disclaimer.
8//     * Redistributions in binary form must reproduce the above
9//       copyright notice, this list of conditions and the following
10//       disclaimer in the documentation and/or other materials provided
11//       with the distribution.
12//     * Neither the name of Google Inc. nor the names of its
13//       contributors may be used to endorse or promote products derived
14//       from this software without specific prior written permission.
15//
16// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27
28#ifndef V8_PROPERTY_H_
29#define V8_PROPERTY_H_
30
31namespace v8 {
32namespace internal {
33
34
35// Abstraction for elements in instance-descriptor arrays.
36//
37// Each descriptor has a key, property attributes, property type,
38// property index (in the actual instance-descriptor array) and
39// optionally a piece of data.
40//
41
42class Descriptor BASE_EMBEDDED {
43 public:
44  static int IndexFromValue(Object* value) {
45    return Smi::cast(value)->value();
46  }
47
48  MUST_USE_RESULT MaybeObject* KeyToSymbol() {
49    if (!StringShape(key_).IsSymbol()) {
50      Object* result;
51      { MaybeObject* maybe_result = Heap::LookupSymbol(key_);
52        if (!maybe_result->ToObject(&result)) return maybe_result;
53      }
54      key_ = String::cast(result);
55    }
56    return key_;
57  }
58
59  String* GetKey() { return key_; }
60  Object* GetValue() { return value_; }
61  PropertyDetails GetDetails() { return details_; }
62
63#ifdef DEBUG
64  void Print();
65#endif
66
67  void SetEnumerationIndex(int index) {
68    ASSERT(PropertyDetails::IsValidIndex(index));
69    details_ = PropertyDetails(details_.attributes(), details_.type(), index);
70  }
71
72 private:
73  String* key_;
74  Object* value_;
75  PropertyDetails details_;
76
77 protected:
78  Descriptor() : details_(Smi::FromInt(0)) {}
79
80  void Init(String* key, Object* value, PropertyDetails details) {
81    key_ = key;
82    value_ = value;
83    details_ = details;
84  }
85
86  Descriptor(String* key, Object* value, PropertyDetails details)
87      : key_(key),
88        value_(value),
89        details_(details) { }
90
91  Descriptor(String* key,
92             Object* value,
93             PropertyAttributes attributes,
94             PropertyType type,
95             int index = 0)
96      : key_(key),
97        value_(value),
98        details_(attributes, type, index) { }
99
100  friend class DescriptorArray;
101};
102
103// A pointer from a map to the new map that is created by adding
104// a named property.  These are key to the speed and functioning of V8.
105// The two maps should always have the same prototype, since
106// MapSpace::CreateBackPointers depends on this.
107class MapTransitionDescriptor: public Descriptor {
108 public:
109  MapTransitionDescriptor(String* key, Map* map, PropertyAttributes attributes)
110      : Descriptor(key, map, attributes, MAP_TRANSITION) { }
111};
112
113// Marks a field name in a map so that adding the field is guaranteed
114// to create a FIELD descriptor in the new map.  Used after adding
115// a constant function the first time, creating a CONSTANT_FUNCTION
116// descriptor in the new map.  This avoids creating multiple maps with
117// the same CONSTANT_FUNCTION field.
118class ConstTransitionDescriptor: public Descriptor {
119 public:
120  explicit ConstTransitionDescriptor(String* key, Map* map)
121      : Descriptor(key, map, NONE, CONSTANT_TRANSITION) { }
122};
123
124
125class FieldDescriptor: public Descriptor {
126 public:
127  FieldDescriptor(String* key,
128                  int field_index,
129                  PropertyAttributes attributes,
130                  int index = 0)
131      : Descriptor(key, Smi::FromInt(field_index), attributes, FIELD, index) {}
132};
133
134
135class ConstantFunctionDescriptor: public Descriptor {
136 public:
137  ConstantFunctionDescriptor(String* key,
138                             JSFunction* function,
139                             PropertyAttributes attributes,
140                             int index = 0)
141      : Descriptor(key, function, attributes, CONSTANT_FUNCTION, index) {}
142};
143
144
145class CallbacksDescriptor:  public Descriptor {
146 public:
147  CallbacksDescriptor(String* key,
148                      Object* proxy,
149                      PropertyAttributes attributes,
150                      int index = 0)
151      : Descriptor(key, proxy, attributes, CALLBACKS, index) {}
152};
153
154
155class LookupResult BASE_EMBEDDED {
156 public:
157  // Where did we find the result;
158  enum {
159    NOT_FOUND,
160    DESCRIPTOR_TYPE,
161    DICTIONARY_TYPE,
162    INTERCEPTOR_TYPE,
163    CONSTANT_TYPE
164  } lookup_type_;
165
166  LookupResult()
167      : lookup_type_(NOT_FOUND),
168        cacheable_(true),
169        details_(NONE, NORMAL) {}
170
171  void DescriptorResult(JSObject* holder, PropertyDetails details, int number) {
172    lookup_type_ = DESCRIPTOR_TYPE;
173    holder_ = holder;
174    details_ = details;
175    number_ = number;
176  }
177
178  void ConstantResult(JSObject* holder) {
179    lookup_type_ = CONSTANT_TYPE;
180    holder_ = holder;
181    details_ =
182        PropertyDetails(static_cast<PropertyAttributes>(DONT_ENUM |
183                                                        DONT_DELETE),
184                        CALLBACKS);
185    number_ = -1;
186  }
187
188  void DictionaryResult(JSObject* holder, int entry) {
189    lookup_type_ = DICTIONARY_TYPE;
190    holder_ = holder;
191    details_ = holder->property_dictionary()->DetailsAt(entry);
192    number_ = entry;
193  }
194
195  void InterceptorResult(JSObject* holder) {
196    lookup_type_ = INTERCEPTOR_TYPE;
197    holder_ = holder;
198    details_ = PropertyDetails(NONE, INTERCEPTOR);
199  }
200
201  void NotFound() {
202    lookup_type_ = NOT_FOUND;
203  }
204
205  JSObject* holder() {
206    ASSERT(IsFound());
207    return holder_;
208  }
209
210  PropertyType type() {
211    ASSERT(IsFound());
212    return details_.type();
213  }
214
215  PropertyAttributes GetAttributes() {
216    ASSERT(IsFound());
217    return details_.attributes();
218  }
219
220  PropertyDetails GetPropertyDetails() {
221    return details_;
222  }
223
224  bool IsReadOnly() { return details_.IsReadOnly(); }
225  bool IsDontDelete() { return details_.IsDontDelete(); }
226  bool IsDontEnum() { return details_.IsDontEnum(); }
227  bool IsDeleted() { return details_.IsDeleted(); }
228  bool IsFound() { return lookup_type_ != NOT_FOUND; }
229
230  // Is the result is a property excluding transitions and the null
231  // descriptor?
232  bool IsProperty() {
233    return IsFound() && (type() < FIRST_PHANTOM_PROPERTY_TYPE);
234  }
235
236  // Is the result a property or a transition?
237  bool IsPropertyOrTransition() {
238    return IsFound() && (type() != NULL_DESCRIPTOR);
239  }
240
241  bool IsCacheable() { return cacheable_; }
242  void DisallowCaching() { cacheable_ = false; }
243
244  Object* GetLazyValue() {
245    switch (type()) {
246      case FIELD:
247        return holder()->FastPropertyAt(GetFieldIndex());
248      case NORMAL: {
249        Object* value;
250        value = holder()->property_dictionary()->ValueAt(GetDictionaryEntry());
251        if (holder()->IsGlobalObject()) {
252          value = JSGlobalPropertyCell::cast(value)->value();
253        }
254        return value;
255      }
256      case CONSTANT_FUNCTION:
257        return GetConstantFunction();
258      default:
259        return Smi::FromInt(0);
260    }
261  }
262
263  Map* GetTransitionMap() {
264    ASSERT(lookup_type_ == DESCRIPTOR_TYPE);
265    ASSERT(type() == MAP_TRANSITION || type() == CONSTANT_TRANSITION);
266    return Map::cast(GetValue());
267  }
268
269  int GetFieldIndex() {
270    ASSERT(lookup_type_ == DESCRIPTOR_TYPE);
271    ASSERT(type() == FIELD);
272    return Descriptor::IndexFromValue(GetValue());
273  }
274
275  int GetDictionaryEntry() {
276    ASSERT(lookup_type_ == DICTIONARY_TYPE);
277    return number_;
278  }
279
280  JSFunction* GetConstantFunction() {
281    ASSERT(type() == CONSTANT_FUNCTION);
282    return JSFunction::cast(GetValue());
283  }
284
285  Object* GetCallbackObject() {
286    if (lookup_type_ == CONSTANT_TYPE) {
287      // For now we only have the __proto__ as constant type.
288      return Heap::prototype_accessors();
289    }
290    return GetValue();
291  }
292
293#ifdef DEBUG
294  void Print();
295#endif
296
297  Object* GetValue() {
298    if (lookup_type_ == DESCRIPTOR_TYPE) {
299      DescriptorArray* descriptors = holder()->map()->instance_descriptors();
300      return descriptors->GetValue(number_);
301    }
302    // In the dictionary case, the data is held in the value field.
303    ASSERT(lookup_type_ == DICTIONARY_TYPE);
304    return holder()->GetNormalizedProperty(this);
305  }
306
307 private:
308  JSObject* holder_;
309  int number_;
310  bool cacheable_;
311  PropertyDetails details_;
312};
313
314
315} }  // namespace v8::internal
316
317#endif  // V8_PROPERTY_H_
318