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_HANDLE_H_ 18 #define ART_RUNTIME_HANDLE_H_ 19 20 #include <android-base/logging.h> 21 22 #include "base/casts.h" 23 #include "base/macros.h" 24 #include "base/mutex.h" 25 #include "base/value_object.h" 26 #include "jni.h" 27 #include "obj_ptr.h" 28 #include "stack_reference.h" 29 30 namespace art { 31 32 class Thread; 33 34 template<class T> class Handle; 35 36 // Handles are memory locations that contain GC roots. As the mirror::Object*s within a handle are 37 // GC visible then the GC may move the references within them, something that couldn't be done with 38 // a wrap pointer. Handles are generally allocated within HandleScopes. Handle is a super-class 39 // of MutableHandle and doesn't support assignment operations. 40 template<class T> 41 class Handle : public ValueObject { 42 public: 43 Handle() : reference_(nullptr) { 44 } 45 46 ALWAYS_INLINE Handle(const Handle<T>& handle) = default; 47 48 ALWAYS_INLINE Handle<T>& operator=(const Handle<T>& handle) = default; 49 50 ALWAYS_INLINE explicit Handle(StackReference<T>* reference) : reference_(reference) { 51 } 52 53 ALWAYS_INLINE T& operator*() const REQUIRES_SHARED(Locks::mutator_lock_) { 54 return *Get(); 55 } 56 57 ALWAYS_INLINE T* operator->() const REQUIRES_SHARED(Locks::mutator_lock_) { 58 return Get(); 59 } 60 61 ALWAYS_INLINE T* Get() const REQUIRES_SHARED(Locks::mutator_lock_) { 62 return down_cast<T*>(reference_->AsMirrorPtr()); 63 } 64 65 ALWAYS_INLINE bool IsNull() const REQUIRES_SHARED(Locks::mutator_lock_) { 66 return Get() == nullptr; 67 } 68 69 ALWAYS_INLINE jobject ToJObject() const REQUIRES_SHARED(Locks::mutator_lock_) { 70 if (UNLIKELY(reference_->AsMirrorPtr() == nullptr)) { 71 // Special case so that we work with null handles. 72 return nullptr; 73 } 74 return reinterpret_cast<jobject>(reference_); 75 } 76 77 ALWAYS_INLINE StackReference<mirror::Object>* GetReference() { 78 return reference_; 79 } 80 81 ALWAYS_INLINE const StackReference<mirror::Object>* GetReference() const { 82 return reference_; 83 } 84 85 ALWAYS_INLINE bool operator!=(std::nullptr_t) const REQUIRES_SHARED(Locks::mutator_lock_) { 86 return !IsNull(); 87 } 88 89 ALWAYS_INLINE bool operator==(std::nullptr_t) const REQUIRES_SHARED(Locks::mutator_lock_) { 90 return IsNull(); 91 } 92 93 protected: 94 template<typename S> 95 explicit Handle(StackReference<S>* reference) 96 : reference_(reference) { 97 } 98 template<typename S> 99 explicit Handle(const Handle<S>& handle) 100 : reference_(handle.reference_) { 101 } 102 103 StackReference<mirror::Object>* reference_; 104 105 private: 106 friend class BuildGenericJniFrameVisitor; 107 template<class S> friend class Handle; 108 friend class HandleScope; 109 template<class S> friend class HandleWrapper; 110 template<size_t kNumReferences> friend class StackHandleScope; 111 }; 112 113 // Handles that support assignment. 114 template<class T> 115 class MutableHandle : public Handle<T> { 116 public: 117 MutableHandle() { 118 } 119 120 ALWAYS_INLINE MutableHandle(const MutableHandle<T>& handle) 121 REQUIRES_SHARED(Locks::mutator_lock_) = default; 122 123 ALWAYS_INLINE MutableHandle<T>& operator=(const MutableHandle<T>& handle) 124 REQUIRES_SHARED(Locks::mutator_lock_) = default; 125 126 ALWAYS_INLINE explicit MutableHandle(StackReference<T>* reference) 127 REQUIRES_SHARED(Locks::mutator_lock_) 128 : Handle<T>(reference) { 129 } 130 131 ALWAYS_INLINE T* Assign(T* reference) REQUIRES_SHARED(Locks::mutator_lock_) { 132 StackReference<mirror::Object>* ref = Handle<T>::GetReference(); 133 T* old = down_cast<T*>(ref->AsMirrorPtr()); 134 ref->Assign(reference); 135 return old; 136 } 137 138 ALWAYS_INLINE T* Assign(ObjPtr<T> reference) REQUIRES_SHARED(Locks::mutator_lock_) { 139 StackReference<mirror::Object>* ref = Handle<T>::GetReference(); 140 T* old = down_cast<T*>(ref->AsMirrorPtr()); 141 ref->Assign(reference.Ptr()); 142 return old; 143 } 144 145 146 template<typename S> 147 explicit MutableHandle(const MutableHandle<S>& handle) REQUIRES_SHARED(Locks::mutator_lock_) 148 : Handle<T>(handle) { 149 } 150 151 template<typename S> 152 explicit MutableHandle(StackReference<S>* reference) REQUIRES_SHARED(Locks::mutator_lock_) 153 : Handle<T>(reference) { 154 } 155 156 private: 157 friend class BuildGenericJniFrameVisitor; 158 friend class HandleScope; 159 template<class S> friend class HandleWrapper; 160 template<size_t kNumReferences> friend class StackHandleScope; 161 }; 162 163 // A special case of Handle that only holds references to null. Invalid when if it goes out of 164 // scope. Example: Handle<T> h = ScopedNullHandle<T> will leave h being undefined. 165 template<class T> 166 class ScopedNullHandle : public Handle<T> { 167 public: 168 ScopedNullHandle() : Handle<T>(&null_ref_) {} 169 170 private: 171 StackReference<mirror::Object> null_ref_; 172 }; 173 174 } // namespace art 175 176 #endif // ART_RUNTIME_HANDLE_H_ 177
