object_reference.h revision e63a745f26fec5a5b4162fc83f6e88a1f696c30c 
1/*
2 * Copyright (C) 2014 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ART_RUNTIME_MIRROR_OBJECT_REFERENCE_H_
18#define ART_RUNTIME_MIRROR_OBJECT_REFERENCE_H_
19
20#include "globals.h"
21#include "locks.h"
22
23namespace art {
24namespace mirror {
25
26class Object;
27
28// Classes shared with the managed side of the world need to be packed so that they don't have
29// extra platform specific padding.
30#define MANAGED PACKED(4)
31
32// Value type representing a reference to a mirror::Object of type MirrorType.
33template<bool kPoisonReferences, class MirrorType>
34class MANAGED ObjectReference {
35 public:
36  MirrorType* AsMirrorPtr() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
37    return UnCompress();
38  }
39
40  void Assign(MirrorType* other) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
41    reference_ = Compress(other);
42  }
43
44  void Clear() {
45    reference_ = 0;
46  }
47
48  uint32_t AsVRegValue() const {
49    return reference_;
50  }
51
52 protected:
53  ObjectReference<kPoisonReferences, MirrorType>(MirrorType* mirror_ptr)
54      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
55      : reference_(Compress(mirror_ptr)) {
56  }
57
58  // Compress reference to its bit representation.
59  static uint32_t Compress(MirrorType* mirror_ptr) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
60    uintptr_t as_bits = reinterpret_cast<uintptr_t>(mirror_ptr);
61    return static_cast<uint32_t>(kPoisonReferences ? -as_bits : as_bits);
62  }
63
64  // Uncompress an encoded reference from its bit representation.
65  MirrorType* UnCompress() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
66    uintptr_t as_bits = kPoisonReferences ? -reference_ : reference_;
67    return reinterpret_cast<MirrorType*>(as_bits);
68  }
69
70  friend class Object;
71
72  // The encoded reference to a mirror::Object.
73  uint32_t reference_;
74};
75
76// References between objects within the managed heap.
77template<class MirrorType>
78class MANAGED HeapReference : public ObjectReference<kPoisonHeapReferences, MirrorType> {
79 public:
80  static HeapReference<MirrorType> FromMirrorPtr(MirrorType* mirror_ptr)
81      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
82    return HeapReference<MirrorType>(mirror_ptr);
83  }
84 private:
85  HeapReference<MirrorType>(MirrorType* mirror_ptr) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
86      : ObjectReference<kPoisonHeapReferences, MirrorType>(mirror_ptr) {}
87};
88
89}  // namespace mirror
90}  // namespace art
91
92#endif  // ART_RUNTIME_MIRROR_OBJECT_REFERENCE_H_
93