1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
|
// 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
// with the distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifndef V8_TRANSITIONS_H_
#define V8_TRANSITIONS_H_
#include "elements-kind.h"
#include "heap.h"
#include "isolate.h"
#include "objects.h"
#include "v8checks.h"
namespace v8 {
namespace internal {
// TransitionArrays are fixed arrays used to hold map transitions for property,
// constant, and element changes.
// The format of the these objects is:
// [0] Descriptor array
// [1] Undefined or back pointer map
// [2] Smi(0) or elements transition map
// [3] Smi(0) or fixed array of prototype transitions
// [4] First transition
// [length() - kTransitionSize] Last transition
class TransitionArray: public FixedArray {
public:
// Accessors for fetching instance transition at transition number.
inline String* GetKey(int transition_number);
inline void SetKey(int transition_number, String* value);
inline Object** GetKeySlot(int transition_number);
int GetSortedKeyIndex(int transition_number) { return transition_number; }
String* GetSortedKey(int transition_number) {
return GetKey(transition_number);
}
inline Map* GetTarget(int transition_number);
inline void SetTarget(int transition_number, Map* target);
inline PropertyDetails GetTargetDetails(int transition_number);
inline Map* elements_transition();
inline void set_elements_transition(
Map* target,
WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
inline bool HasElementsTransition();
inline void ClearElementsTransition();
inline DescriptorArray* descriptors();
inline void set_descriptors(DescriptorArray* descriptors,
WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
inline Object** GetDescriptorsSlot();
inline Object* back_pointer_storage();
inline void set_back_pointer_storage(
Object* back_pointer,
WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
inline FixedArray* GetPrototypeTransitions();
inline void SetPrototypeTransitions(
FixedArray* prototype_transitions,
WriteBarrierMode mode = UPDATE_WRITE_BARRIER);
inline Object** GetPrototypeTransitionsSlot();
inline bool HasPrototypeTransitions();
inline HeapObject* UncheckedPrototypeTransitions();
// Returns the number of transitions in the array.
int number_of_transitions() {
ASSERT(length() >= kFirstIndex);
int len = length();
return len <= kFirstIndex ? 0 : (len - kFirstIndex) / kTransitionSize;
}
inline int number_of_entries() { return number_of_transitions(); }
// Allocate a new transition array with a single entry.
static MUST_USE_RESULT MaybeObject* NewWith(String* name, Map* target);
// Copy the transition array, inserting a new transition.
// TODO(verwaest): This should not cause an existing transition to be
// overwritten.
MUST_USE_RESULT MaybeObject* CopyInsert(String* name, Map* target);
// Copy a single transition from the origin array.
inline void CopyFrom(TransitionArray* origin,
int origin_transition,
int target_transition,
const WhitenessWitness& witness);
// Search a transition for a given property name.
inline int Search(String* name);
// Allocates a TransitionArray.
MUST_USE_RESULT static MaybeObject* Allocate(int number_of_transitions);
// Casting.
static inline TransitionArray* cast(Object* obj);
// Constant for denoting key was not found.
static const int kNotFound = -1;
static const int kDescriptorsIndex = 0;
static const int kBackPointerStorageIndex = 1;
static const int kElementsTransitionIndex = 2;
static const int kPrototypeTransitionsIndex = 3;
static const int kFirstIndex = 4;
// Layout transition array header.
static const int kDescriptorsOffset = FixedArray::kHeaderSize;
static const int kBackPointerStorageOffset = kDescriptorsOffset +
kPointerSize;
static const int kElementsTransitionOffset = kBackPointerStorageOffset +
kPointerSize;
static const int kPrototypeTransitionsOffset = kElementsTransitionOffset +
kPointerSize;
// Layout of map transition.
static const int kTransitionKey = 0;
static const int kTransitionTarget = 1;
static const int kTransitionSize = 2;
#ifdef OBJECT_PRINT
// Print all the transitions.
inline void PrintTransitions() {
PrintTransitions(stdout);
}
void PrintTransitions(FILE* out);
#endif
#ifdef DEBUG
bool IsSortedNoDuplicates();
bool IsConsistentWithBackPointers(Map* current_map);
bool IsEqualTo(TransitionArray* other);
#endif
// The maximum number of transitions we want in a transition array (should
// fit in a page).
static const int kMaxNumberOfTransitions = 1024 + 512;
private:
// Conversion from transition number to array indices.
static int ToKeyIndex(int transition_number) {
return kFirstIndex +
(transition_number * kTransitionSize) +
kTransitionKey;
}
static int ToTargetIndex(int transition_number) {
return kFirstIndex +
(transition_number * kTransitionSize) +
kTransitionTarget;
}
inline void Set(int transition_number,
String* key,
Map* target,
const WhitenessWitness&);
DISALLOW_IMPLICIT_CONSTRUCTORS(TransitionArray);
};
} } // namespace v8::internal
#endif // V8_TRANSITIONS_H_
|
