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 "base/mutex.h" // For Locks::mutator_lock_. 21 #include "globals.h" 22 23 namespace art { 24 namespace mirror { 25 26 class 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. 33 template<bool kPoisonReferences, class MirrorType> 34 class MANAGED ObjectReference { 35 public: AsMirrorPtr()36 MirrorType* AsMirrorPtr() const SHARED_REQUIRES(Locks::mutator_lock_) { 37 return UnCompress(); 38 } 39 Assign(MirrorType * other)40 void Assign(MirrorType* other) SHARED_REQUIRES(Locks::mutator_lock_) { 41 reference_ = Compress(other); 42 } 43 Clear()44 void Clear() { 45 reference_ = 0; 46 DCHECK(IsNull()); 47 } 48 IsNull()49 bool IsNull() const { 50 return reference_ == 0; 51 } 52 AsVRegValue()53 uint32_t AsVRegValue() const { 54 return reference_; 55 } 56 57 protected: 58 ObjectReference<kPoisonReferences, MirrorType>(MirrorType* mirror_ptr) SHARED_REQUIRES(Locks::mutator_lock_)59 SHARED_REQUIRES(Locks::mutator_lock_) 60 : reference_(Compress(mirror_ptr)) { 61 } 62 63 // Compress reference to its bit representation. Compress(MirrorType * mirror_ptr)64 static uint32_t Compress(MirrorType* mirror_ptr) SHARED_REQUIRES(Locks::mutator_lock_) { 65 uintptr_t as_bits = reinterpret_cast<uintptr_t>(mirror_ptr); 66 return static_cast<uint32_t>(kPoisonReferences ? -as_bits : as_bits); 67 } 68 69 // Uncompress an encoded reference from its bit representation. UnCompress()70 MirrorType* UnCompress() const SHARED_REQUIRES(Locks::mutator_lock_) { 71 uintptr_t as_bits = kPoisonReferences ? -reference_ : reference_; 72 return reinterpret_cast<MirrorType*>(as_bits); 73 } 74 75 friend class Object; 76 77 // The encoded reference to a mirror::Object. 78 uint32_t reference_; 79 }; 80 81 // References between objects within the managed heap. 82 template<class MirrorType> 83 class MANAGED HeapReference : public ObjectReference<kPoisonHeapReferences, MirrorType> { 84 public: FromMirrorPtr(MirrorType * mirror_ptr)85 static HeapReference<MirrorType> FromMirrorPtr(MirrorType* mirror_ptr) 86 SHARED_REQUIRES(Locks::mutator_lock_) { 87 return HeapReference<MirrorType>(mirror_ptr); 88 } 89 private: SHARED_REQUIRES(Locks::mutator_lock_)90 HeapReference<MirrorType>(MirrorType* mirror_ptr) SHARED_REQUIRES(Locks::mutator_lock_) 91 : ObjectReference<kPoisonHeapReferences, MirrorType>(mirror_ptr) {} 92 }; 93 94 // Standard compressed reference used in the runtime. Used for StackReference and GC roots. 95 template<class MirrorType> 96 class MANAGED CompressedReference : public mirror::ObjectReference<false, MirrorType> { 97 public: SHARED_REQUIRES(Locks::mutator_lock_)98 CompressedReference<MirrorType>() SHARED_REQUIRES(Locks::mutator_lock_) 99 : mirror::ObjectReference<false, MirrorType>(nullptr) {} 100 FromMirrorPtr(MirrorType * p)101 static CompressedReference<MirrorType> FromMirrorPtr(MirrorType* p) 102 SHARED_REQUIRES(Locks::mutator_lock_) { 103 return CompressedReference<MirrorType>(p); 104 } 105 106 private: SHARED_REQUIRES(Locks::mutator_lock_)107 CompressedReference<MirrorType>(MirrorType* p) SHARED_REQUIRES(Locks::mutator_lock_) 108 : mirror::ObjectReference<false, MirrorType>(p) {} 109 }; 110 111 } // namespace mirror 112 } // namespace art 113 114 #endif // ART_RUNTIME_MIRROR_OBJECT_REFERENCE_H_ 115