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_GC_ROOT_H_
18#define ART_RUNTIME_GC_ROOT_H_
19
20#include "base/macros.h"
21#include "base/mutex.h"       // For Locks::mutator_lock_.
22#include "object_callbacks.h"
23
24namespace art {
25
26template<class MirrorType>
27class PACKED(4) GcRoot {
28 public:
29  template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
30  ALWAYS_INLINE MirrorType* Read() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
31  ALWAYS_INLINE void Assign(MirrorType* value) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
32
33  void VisitRoot(RootCallback* callback, void* arg, uint32_t thread_id, RootType root_type) {
34    callback(reinterpret_cast<mirror::Object**>(&root_), arg, thread_id, root_type);
35  }
36
37  // This is only used by IrtIterator.
38  ALWAYS_INLINE MirrorType** AddressWithoutBarrier() {
39    return &root_;
40  }
41
42  bool IsNull() const {
43    // It's safe to null-check it without a read barrier.
44    return root_ == nullptr;
45  }
46
47  ALWAYS_INLINE explicit GcRoot<MirrorType>() : root_(nullptr) {
48  }
49
50  ALWAYS_INLINE explicit GcRoot<MirrorType>(MirrorType* ref)
51      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) : root_(ref) {
52  }
53
54 private:
55  MirrorType* root_;
56};
57
58}  // namespace art
59
60#endif  // ART_RUNTIME_GC_ROOT_H_
61