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      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_REFERENCE_H_
     18 #define ART_RUNTIME_MIRROR_REFERENCE_H_
     19 
     20 #include "base/enums.h"
     21 #include "base/locks.h"
     22 #include "base/macros.h"
     23 #include "obj_ptr.h"
     24 #include "object.h"
     25 #include "read_barrier_option.h"
     26 
     27 namespace art {
     28 
     29 namespace gc {
     30 
     31 class ReferenceProcessor;
     32 class ReferenceQueue;
     33 
     34 }  // namespace gc
     35 
     36 struct ReferenceOffsets;
     37 struct FinalizerReferenceOffsets;
     38 
     39 namespace mirror {
     40 
     41 // C++ mirror of java.lang.ref.Reference
     42 class MANAGED Reference : public Object {
     43  public:
     44   // Size of java.lang.ref.Reference.class.
     45   static uint32_t ClassSize(PointerSize pointer_size);
     46 
     47   // Size of an instance of java.lang.ref.Reference.
     48   static constexpr uint32_t InstanceSize() {
     49     return sizeof(Reference);
     50   }
     51 
     52   static MemberOffset PendingNextOffset() {
     53     return OFFSET_OF_OBJECT_MEMBER(Reference, pending_next_);
     54   }
     55   static MemberOffset QueueOffset() {
     56     return OFFSET_OF_OBJECT_MEMBER(Reference, queue_);
     57   }
     58   static MemberOffset QueueNextOffset() {
     59     return OFFSET_OF_OBJECT_MEMBER(Reference, queue_next_);
     60   }
     61   static MemberOffset ReferentOffset() {
     62     return OFFSET_OF_OBJECT_MEMBER(Reference, referent_);
     63   }
     64   template<ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
     65   Object* GetReferent() REQUIRES_SHARED(Locks::mutator_lock_) {
     66     return GetFieldObjectVolatile<Object, kDefaultVerifyFlags, kReadBarrierOption>(
     67         ReferentOffset());
     68   }
     69   template<bool kTransactionActive>
     70   void SetReferent(ObjPtr<Object> referent) REQUIRES_SHARED(Locks::mutator_lock_);
     71   template<bool kTransactionActive>
     72   void ClearReferent() REQUIRES_SHARED(Locks::mutator_lock_) {
     73     SetFieldObjectVolatile<kTransactionActive>(ReferentOffset(), nullptr);
     74   }
     75 
     76   template <ReadBarrierOption kReadBarrierOption = kWithReadBarrier>
     77   Reference* GetPendingNext() REQUIRES_SHARED(Locks::mutator_lock_) {
     78     return GetFieldObject<Reference, kDefaultVerifyFlags, kReadBarrierOption>(PendingNextOffset());
     79   }
     80 
     81   void SetPendingNext(ObjPtr<Reference> pending_next) REQUIRES_SHARED(Locks::mutator_lock_);
     82 
     83   // Returns true if the reference's pendingNext is null, indicating it is
     84   // okay to process this reference.
     85   //
     86   // If pendingNext is not null, then one of the following cases holds:
     87   // 1. The reference has already been enqueued to a java ReferenceQueue. In
     88   // this case the referent should not be considered for reference processing
     89   // ever again.
     90   // 2. The reference is currently part of a list of references that may
     91   // shortly be enqueued on a java ReferenceQueue. In this case the reference
     92   // should not be processed again until and unless the reference has been
     93   // removed from the list after having determined the reference is not ready
     94   // to be enqueued on a java ReferenceQueue.
     95   bool IsUnprocessed() REQUIRES_SHARED(Locks::mutator_lock_) {
     96     return GetPendingNext<kWithoutReadBarrier>() == nullptr;
     97   }
     98 
     99  private:
    100   // Note: This avoids a read barrier, it should only be used by the GC.
    101   HeapReference<Object>* GetReferentReferenceAddr() REQUIRES_SHARED(Locks::mutator_lock_) {
    102     return GetFieldObjectReferenceAddr<kDefaultVerifyFlags>(ReferentOffset());
    103   }
    104 
    105   // Field order required by test "ValidateFieldOrderOfJavaCppUnionClasses".
    106   HeapReference<Reference> pending_next_;
    107   HeapReference<Object> queue_;
    108   HeapReference<Reference> queue_next_;
    109   HeapReference<Object> referent_;  // Note this is Java volatile:
    110 
    111   friend struct art::ReferenceOffsets;  // for verifying offset information
    112   friend class gc::ReferenceProcessor;
    113   friend class gc::ReferenceQueue;
    114   DISALLOW_IMPLICIT_CONSTRUCTORS(Reference);
    115 };
    116 
    117 // C++ mirror of java.lang.ref.FinalizerReference
    118 class MANAGED FinalizerReference : public Reference {
    119  public:
    120   static MemberOffset ZombieOffset() {
    121     return OFFSET_OF_OBJECT_MEMBER(FinalizerReference, zombie_);
    122   }
    123 
    124   template<bool kTransactionActive>
    125   void SetZombie(ObjPtr<Object> zombie) REQUIRES_SHARED(Locks::mutator_lock_);
    126 
    127   Object* GetZombie() REQUIRES_SHARED(Locks::mutator_lock_) {
    128     return GetFieldObjectVolatile<Object>(ZombieOffset());
    129   }
    130 
    131  private:
    132   HeapReference<FinalizerReference> next_;
    133   HeapReference<FinalizerReference> prev_;
    134   HeapReference<Object> zombie_;
    135 
    136   friend struct art::FinalizerReferenceOffsets;  // for verifying offset information
    137   DISALLOW_IMPLICIT_CONSTRUCTORS(FinalizerReference);
    138 };
    139 
    140 }  // namespace mirror
    141 }  // namespace art
    142 
    143 #endif  // ART_RUNTIME_MIRROR_REFERENCE_H_
    144