blob: 84c8538224856548e14cf955248634a453cccdb7 (
plain)
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
|
// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_OBJECTS_MAYBE_OBJECT_H_
#define V8_OBJECTS_MAYBE_OBJECT_H_
#include "include/v8.h"
#include "src/globals.h"
#include "src/objects.h"
namespace v8 {
namespace internal {
class HeapObject;
class Smi;
class StringStream;
// A MaybeObject is either a SMI, a strong reference to a HeapObject, a weak
// reference to a HeapObject, or a cleared weak reference. It's used for
// implementing in-place weak references (see design doc: goo.gl/j6SdcK )
class MaybeObject {
public:
bool IsSmi() const { return HAS_SMI_TAG(this); }
inline bool ToSmi(Smi** value);
inline Smi* ToSmi();
bool IsClearedWeakHeapObject() const {
return ::v8::internal::IsClearedWeakHeapObject(this);
}
inline bool IsStrongOrWeakHeapObject() const;
inline bool ToStrongOrWeakHeapObject(HeapObject** result);
inline bool ToStrongOrWeakHeapObject(HeapObject** result,
HeapObjectReferenceType* reference_type);
inline bool IsStrongHeapObject() const;
inline bool ToStrongHeapObject(HeapObject** result);
inline HeapObject* ToStrongHeapObject();
inline bool IsWeakHeapObject() const;
inline bool IsWeakOrClearedHeapObject() const;
inline bool ToWeakHeapObject(HeapObject** result);
inline HeapObject* ToWeakHeapObject();
// Returns the HeapObject pointed to (either strongly or weakly).
inline HeapObject* GetHeapObject();
inline Object* GetHeapObjectOrSmi();
inline bool IsObject() const;
inline Object* ToObject();
static MaybeObject* FromSmi(Smi* smi) {
DCHECK(HAS_SMI_TAG(smi));
return reinterpret_cast<MaybeObject*>(smi);
}
static MaybeObject* FromObject(Object* object) {
DCHECK(!HasWeakHeapObjectTag(object));
return reinterpret_cast<MaybeObject*>(object);
}
static inline MaybeObject* MakeWeak(MaybeObject* object);
#ifdef VERIFY_HEAP
static void VerifyMaybeObjectPointer(Isolate* isolate, MaybeObject* p);
#endif
// Prints this object without details.
void ShortPrint(FILE* out = stdout);
// Prints this object without details to a message accumulator.
void ShortPrint(StringStream* accumulator);
void ShortPrint(std::ostream& os);
#ifdef OBJECT_PRINT
void Print();
void Print(std::ostream& os);
#else
void Print() { ShortPrint(); }
void Print(std::ostream& os) { ShortPrint(os); }
#endif
private:
DISALLOW_IMPLICIT_CONSTRUCTORS(MaybeObject);
};
// A HeapObjectReference is either a strong reference to a HeapObject, a weak
// reference to a HeapObject, or a cleared weak reference.
class HeapObjectReference : public MaybeObject {
public:
static HeapObjectReference* Strong(Object* object) {
DCHECK(!object->IsSmi());
DCHECK(!HasWeakHeapObjectTag(object));
return reinterpret_cast<HeapObjectReference*>(object);
}
static HeapObjectReference* Weak(Object* object) {
DCHECK(!object->IsSmi());
DCHECK(!HasWeakHeapObjectTag(object));
return AddWeakHeapObjectMask(object);
}
static HeapObjectReference* ClearedValue() {
return reinterpret_cast<HeapObjectReference*>(kClearedWeakHeapObject);
}
static void Update(HeapObjectReference** slot, HeapObject* value) {
DCHECK(!HAS_SMI_TAG(*slot));
DCHECK(Internals::HasHeapObjectTag(value));
#ifdef DEBUG
bool weak_before = HasWeakHeapObjectTag(*slot);
#endif
*slot = reinterpret_cast<HeapObjectReference*>(
reinterpret_cast<intptr_t>(value) |
(reinterpret_cast<intptr_t>(*slot) & kWeakHeapObjectMask));
#ifdef DEBUG
bool weak_after = HasWeakHeapObjectTag(*slot);
DCHECK_EQ(weak_before, weak_after);
#endif
}
private:
DISALLOW_IMPLICIT_CONSTRUCTORS(HeapObjectReference);
};
} // namespace internal
} // namespace v8
#endif // V8_OBJECTS_MAYBE_OBJECT_H_
|
