2 * Copyright (C) 2016 The Android Open Source Project
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
8 * http://www.apache.org/licenses/LICENSE-2.0
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.
17 #ifndef ART_RUNTIME_OBJ_PTR_H_
18 #define ART_RUNTIME_OBJ_PTR_H_
21 #include <type_traits>
23 #include "base/macros.h"
24 #include "base/mutex.h" // For Locks::mutator_lock_.
29 constexpr bool kObjPtrPoisoning = kIsDebugBuild;
31 // Value type representing a pointer to a mirror::Object of type MirrorType
32 // Pass kPoison as a template boolean for testing in non-debug builds.
33 // Since the cookie is thread based, it is not safe to share an ObjPtr between threads.
34 template<class MirrorType>
36 static constexpr size_t kCookieShift =
37 sizeof(kHeapReferenceSize) * kBitsPerByte - kObjectAlignmentShift;
38 static constexpr size_t kCookieBits = sizeof(uintptr_t) * kBitsPerByte - kCookieShift;
39 static constexpr uintptr_t kCookieMask = (static_cast<uintptr_t>(1u) << kCookieBits) - 1;
41 static_assert(kCookieBits >= kObjectAlignmentShift,
42 "must have a least kObjectAlignmentShift bits");
45 ALWAYS_INLINE ObjPtr() REQUIRES_SHARED(Locks::mutator_lock_) : reference_(0u) {}
47 // Note: The following constructors allow implicit conversion. This simplifies code that uses
48 // them, e.g., for parameter passing. However, in general, implicit-conversion constructors
49 // are discouraged and detected by cpplint and clang-tidy. So mark these constructors
50 // as NOLINT (without category, as the categories are different).
52 ALWAYS_INLINE ObjPtr(std::nullptr_t) // NOLINT
53 REQUIRES_SHARED(Locks::mutator_lock_)
56 template <typename Type,
57 typename = typename std::enable_if<std::is_base_of<MirrorType, Type>::value>::type>
58 ALWAYS_INLINE ObjPtr(Type* ptr) // NOLINT
59 REQUIRES_SHARED(Locks::mutator_lock_)
60 : reference_(Encode(static_cast<MirrorType*>(ptr))) {
63 template <typename Type,
64 typename = typename std::enable_if<std::is_base_of<MirrorType, Type>::value>::type>
65 ALWAYS_INLINE ObjPtr(const ObjPtr<Type>& other) // NOLINT
66 REQUIRES_SHARED(Locks::mutator_lock_)
67 : reference_(Encode(static_cast<MirrorType*>(other.Ptr()))) {
70 template <typename Type,
71 typename = typename std::enable_if<std::is_base_of<MirrorType, Type>::value>::type>
72 ALWAYS_INLINE ObjPtr& operator=(const ObjPtr<Type>& other)
73 REQUIRES_SHARED(Locks::mutator_lock_) {
74 reference_ = Encode(static_cast<MirrorType*>(other.Ptr()));
78 ALWAYS_INLINE ObjPtr& operator=(MirrorType* ptr) REQUIRES_SHARED(Locks::mutator_lock_) {
83 ALWAYS_INLINE void Assign(MirrorType* ptr) REQUIRES_SHARED(Locks::mutator_lock_) {
84 reference_ = Encode(ptr);
87 ALWAYS_INLINE MirrorType* operator->() const REQUIRES_SHARED(Locks::mutator_lock_) {
91 ALWAYS_INLINE bool IsNull() const {
92 return reference_ == 0;
95 // Ptr makes sure that the object pointer is valid.
96 ALWAYS_INLINE MirrorType* Ptr() const REQUIRES_SHARED(Locks::mutator_lock_) {
98 return PtrUnchecked();
101 ALWAYS_INLINE bool IsValid() const REQUIRES_SHARED(Locks::mutator_lock_);
103 ALWAYS_INLINE void AssertValid() const REQUIRES_SHARED(Locks::mutator_lock_);
105 ALWAYS_INLINE bool operator==(const ObjPtr& ptr) const REQUIRES_SHARED(Locks::mutator_lock_) {
106 return Ptr() == ptr.Ptr();
109 template <typename PointerType>
110 ALWAYS_INLINE bool operator==(const PointerType* ptr) const
111 REQUIRES_SHARED(Locks::mutator_lock_) {
115 ALWAYS_INLINE bool operator==(std::nullptr_t) const {
119 ALWAYS_INLINE bool operator!=(const ObjPtr& ptr) const REQUIRES_SHARED(Locks::mutator_lock_) {
120 return Ptr() != ptr.Ptr();
123 template <typename PointerType>
124 ALWAYS_INLINE bool operator!=(const PointerType* ptr) const
125 REQUIRES_SHARED(Locks::mutator_lock_) {
129 ALWAYS_INLINE bool operator!=(std::nullptr_t) const {
133 // Ptr unchecked does not check that object pointer is valid. Do not use if you can avoid it.
134 ALWAYS_INLINE MirrorType* PtrUnchecked() const {
135 if (kObjPtrPoisoning) {
136 return reinterpret_cast<MirrorType*>(
137 static_cast<uintptr_t>(static_cast<uint32_t>(reference_ << kObjectAlignmentShift)));
139 return reinterpret_cast<MirrorType*>(reference_);
143 // Static function to be friendly with null pointers.
144 template <typename SourceType>
145 static ObjPtr<MirrorType> DownCast(ObjPtr<SourceType> ptr) REQUIRES_SHARED(Locks::mutator_lock_) {
146 static_assert(std::is_base_of<SourceType, MirrorType>::value,
147 "Target type must be a subtype of source type");
148 return static_cast<MirrorType*>(ptr.Ptr());
152 // Trim off high bits of thread local cookie.
153 ALWAYS_INLINE static uintptr_t TrimCookie(uintptr_t cookie) {
154 return cookie & kCookieMask;
157 ALWAYS_INLINE uintptr_t GetCookie() const {
158 return reference_ >> kCookieShift;
161 ALWAYS_INLINE static uintptr_t Encode(MirrorType* ptr) REQUIRES_SHARED(Locks::mutator_lock_);
162 // The encoded reference and cookie.
163 uintptr_t reference_;
166 static_assert(std::is_trivially_copyable<ObjPtr<void>>::value,
167 "ObjPtr should be trivially copyable");
169 // Hash function for stl data structures.
172 template<class MirrorType>
173 size_t operator()(const ObjPtr<MirrorType>& ptr) const NO_THREAD_SAFETY_ANALYSIS {
174 return std::hash<MirrorType*>()(ptr.Ptr());
178 template<class MirrorType, typename PointerType>
179 ALWAYS_INLINE bool operator==(const PointerType* a, const ObjPtr<MirrorType>& b)
180 REQUIRES_SHARED(Locks::mutator_lock_) {
184 template<class MirrorType>
185 ALWAYS_INLINE bool operator==(std::nullptr_t, const ObjPtr<MirrorType>& b) {
189 template<typename MirrorType, typename PointerType>
190 ALWAYS_INLINE bool operator!=(const PointerType* a, const ObjPtr<MirrorType>& b)
191 REQUIRES_SHARED(Locks::mutator_lock_) {
195 template<class MirrorType>
196 ALWAYS_INLINE bool operator!=(std::nullptr_t, const ObjPtr<MirrorType>& b) {
200 template<class MirrorType>
201 static inline ObjPtr<MirrorType> MakeObjPtr(MirrorType* ptr) {
202 return ObjPtr<MirrorType>(ptr);
205 template<class MirrorType>
206 static inline ObjPtr<MirrorType> MakeObjPtr(ObjPtr<MirrorType> ptr) {
207 return ObjPtr<MirrorType>(ptr);
210 template<class MirrorType>
211 ALWAYS_INLINE std::ostream& operator<<(std::ostream& os, ObjPtr<MirrorType> ptr);
215 #endif // ART_RUNTIME_OBJ_PTR_H_