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
|
/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_MIRROR_OBJECT_REFERENCE_H_
#define ART_RUNTIME_MIRROR_OBJECT_REFERENCE_H_
#include "base/atomic.h"
#include "base/locks.h" // For Locks::mutator_lock_.
#include "heap_poisoning.h"
#include "obj_ptr.h"
#include "runtime_globals.h"
namespace art {
namespace mirror {
class Object;
// Classes shared with the managed side of the world need to be packed so that they don't have
// extra platform specific padding.
#define MANAGED PACKED(4)
template<bool kPoisonReferences, class MirrorType>
class PtrCompression {
public:
// Compress reference to its bit representation.
static uint32_t Compress(MirrorType* mirror_ptr) {
uintptr_t as_bits = reinterpret_cast<uintptr_t>(mirror_ptr);
return static_cast<uint32_t>(kPoisonReferences ? -as_bits : as_bits);
}
// Uncompress an encoded reference from its bit representation.
static MirrorType* Decompress(uint32_t ref) {
uintptr_t as_bits = kPoisonReferences ? -ref : ref;
return reinterpret_cast<MirrorType*>(as_bits);
}
// Convert an ObjPtr to a compressed reference.
static uint32_t Compress(ObjPtr<MirrorType> ptr) REQUIRES_SHARED(Locks::mutator_lock_);
};
// Value type representing a reference to a mirror::Object of type MirrorType.
template<bool kPoisonReferences, class MirrorType>
class MANAGED ObjectReference {
private:
using Compression = PtrCompression<kPoisonReferences, MirrorType>;
public:
/*
* Returns a pointer to the mirror of the managed object this reference is for.
*
* This does NOT return the current object (which isn't derived from, and
* therefor cannot be a mirror::Object) as a mirror pointer. Instead, this
* returns a pointer to the mirror of the managed object this refers to.
*
* TODO (chriswailes): Rename to GetPtr().
*/
MirrorType* AsMirrorPtr() const {
return Compression::Decompress(reference_);
}
void Assign(MirrorType* other) {
reference_ = Compression::Compress(other);
}
void Assign(ObjPtr<MirrorType> ptr) REQUIRES_SHARED(Locks::mutator_lock_);
void Clear() {
reference_ = 0;
DCHECK(IsNull());
}
bool IsNull() const {
return reference_ == 0;
}
uint32_t AsVRegValue() const {
return reference_;
}
static ObjectReference<kPoisonReferences, MirrorType> FromMirrorPtr(MirrorType* mirror_ptr)
REQUIRES_SHARED(Locks::mutator_lock_) {
return ObjectReference<kPoisonReferences, MirrorType>(mirror_ptr);
}
protected:
explicit ObjectReference(MirrorType* mirror_ptr) REQUIRES_SHARED(Locks::mutator_lock_)
: reference_(Compression::Compress(mirror_ptr)) {
}
// The encoded reference to a mirror::Object.
uint32_t reference_;
};
// References between objects within the managed heap.
// Similar API to ObjectReference, but not a value type. Supports atomic access.
template<class MirrorType>
class MANAGED HeapReference {
private:
using Compression = PtrCompression<kPoisonHeapReferences, MirrorType>;
public:
HeapReference() REQUIRES_SHARED(Locks::mutator_lock_) : HeapReference(nullptr) {}
template <bool kIsVolatile = false>
MirrorType* AsMirrorPtr() const REQUIRES_SHARED(Locks::mutator_lock_) {
return Compression::Decompress(
kIsVolatile ? reference_.load(std::memory_order_seq_cst) : reference_.LoadJavaData());
}
template <bool kIsVolatile = false>
void Assign(MirrorType* other) REQUIRES_SHARED(Locks::mutator_lock_) {
if (kIsVolatile) {
reference_.store(Compression::Compress(other), std::memory_order_seq_cst);
} else {
reference_.StoreJavaData(Compression::Compress(other));
}
}
template <bool kIsVolatile = false>
void Assign(ObjPtr<MirrorType> ptr) REQUIRES_SHARED(Locks::mutator_lock_);
void Clear() {
reference_.StoreJavaData(0);
DCHECK(IsNull());
}
bool IsNull() const {
return reference_.LoadJavaData() == 0;
}
static HeapReference<MirrorType> FromMirrorPtr(MirrorType* mirror_ptr)
REQUIRES_SHARED(Locks::mutator_lock_) {
return HeapReference<MirrorType>(mirror_ptr);
}
bool CasWeakRelaxed(MirrorType* old_ptr, MirrorType* new_ptr)
REQUIRES_SHARED(Locks::mutator_lock_);
private:
explicit HeapReference(MirrorType* mirror_ptr) REQUIRES_SHARED(Locks::mutator_lock_)
: reference_(Compression::Compress(mirror_ptr)) {}
// The encoded reference to a mirror::Object. Atomically updateable.
Atomic<uint32_t> reference_;
};
static_assert(sizeof(mirror::HeapReference<mirror::Object>) == kHeapReferenceSize,
"heap reference size does not match");
// Standard compressed reference used in the runtime. Used for StackReference and GC roots.
template<class MirrorType>
class MANAGED CompressedReference : public mirror::ObjectReference<false, MirrorType> {
public:
CompressedReference<MirrorType>() noexcept REQUIRES_SHARED(Locks::mutator_lock_)
: mirror::ObjectReference<false, MirrorType>(nullptr) {}
static CompressedReference<MirrorType> FromMirrorPtr(MirrorType* p)
REQUIRES_SHARED(Locks::mutator_lock_) {
return CompressedReference<MirrorType>(p);
}
private:
explicit CompressedReference(MirrorType* p) REQUIRES_SHARED(Locks::mutator_lock_)
: mirror::ObjectReference<false, MirrorType>(p) {}
};
} // namespace mirror
} // namespace art
#endif // ART_RUNTIME_MIRROR_OBJECT_REFERENCE_H_
|
