/*
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* Copyright (C) 2014 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ART_RUNTIME_HANDLE_SCOPE_H_
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#define ART_RUNTIME_HANDLE_SCOPE_H_
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#include <stack>
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#include <android-base/logging.h>
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#include "base/enums.h"
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#include "base/locks.h"
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#include "base/macros.h"
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#include "stack_reference.h"
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namespace art {
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template<class T> class Handle;
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class HandleScope;
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template<class T> class HandleWrapper;
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template<class T> class HandleWrapperObjPtr;
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template<class T> class MutableHandle;
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template<class MirrorType> class ObjPtr;
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class Thread;
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class VariableSizedHandleScope;
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namespace mirror {
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class Object;
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} // namespace mirror
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// Basic handle scope, tracked by a list. May be variable sized.
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class PACKED(4) BaseHandleScope {
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public:
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bool IsVariableSized() const {
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return number_of_references_ == kNumReferencesVariableSized;
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}
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// Number of references contained within this handle scope.
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ALWAYS_INLINE uint32_t NumberOfReferences() const;
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ALWAYS_INLINE bool Contains(StackReference<mirror::Object>* handle_scope_entry) const;
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template <typename Visitor>
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ALWAYS_INLINE void VisitRoots(Visitor& visitor) REQUIRES_SHARED(Locks::mutator_lock_);
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// Link to previous BaseHandleScope or null.
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BaseHandleScope* GetLink() const {
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return link_;
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}
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ALWAYS_INLINE VariableSizedHandleScope* AsVariableSized();
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ALWAYS_INLINE HandleScope* AsHandleScope();
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ALWAYS_INLINE const VariableSizedHandleScope* AsVariableSized() const;
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ALWAYS_INLINE const HandleScope* AsHandleScope() const;
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protected:
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BaseHandleScope(BaseHandleScope* link, uint32_t num_references)
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: link_(link),
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number_of_references_(num_references) {}
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// Variable sized constructor.
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explicit BaseHandleScope(BaseHandleScope* link)
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: link_(link),
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number_of_references_(kNumReferencesVariableSized) {}
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static constexpr int32_t kNumReferencesVariableSized = -1;
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// Link-list of handle scopes. The root is held by a Thread.
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BaseHandleScope* const link_;
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// Number of handlerized references. -1 for variable sized handle scopes.
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const int32_t number_of_references_;
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private:
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DISALLOW_COPY_AND_ASSIGN(BaseHandleScope);
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};
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// HandleScopes are scoped objects containing a number of Handles. They are used to allocate
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// handles, for these handles (and the objects contained within them) to be visible/roots for the
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// GC. It is most common to stack allocate HandleScopes using StackHandleScope.
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class PACKED(4) HandleScope : public BaseHandleScope {
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public:
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~HandleScope() {}
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// We have versions with and without explicit pointer size of the following. The first two are
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// used at runtime, so OFFSETOF_MEMBER computes the right offsets automatically. The last one
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// takes the pointer size explicitly so that at compile time we can cross-compile correctly.
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// Returns the size of a HandleScope containing num_references handles.
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static size_t SizeOf(uint32_t num_references);
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// Returns the size of a HandleScope containing num_references handles.
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static size_t SizeOf(PointerSize pointer_size, uint32_t num_references);
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ALWAYS_INLINE mirror::Object* GetReference(size_t i) const
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REQUIRES_SHARED(Locks::mutator_lock_);
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ALWAYS_INLINE Handle<mirror::Object> GetHandle(size_t i);
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ALWAYS_INLINE MutableHandle<mirror::Object> GetMutableHandle(size_t i)
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REQUIRES_SHARED(Locks::mutator_lock_);
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ALWAYS_INLINE void SetReference(size_t i, mirror::Object* object)
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REQUIRES_SHARED(Locks::mutator_lock_);
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ALWAYS_INLINE bool Contains(StackReference<mirror::Object>* handle_scope_entry) const;
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// Offset of link within HandleScope, used by generated code.
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static constexpr size_t LinkOffset(PointerSize pointer_size ATTRIBUTE_UNUSED) {
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return 0;
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}
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// Offset of length within handle scope, used by generated code.
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static constexpr size_t NumberOfReferencesOffset(PointerSize pointer_size) {
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return static_cast<size_t>(pointer_size);
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}
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// Offset of link within handle scope, used by generated code.
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static constexpr size_t ReferencesOffset(PointerSize pointer_size) {
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return NumberOfReferencesOffset(pointer_size) + sizeof(number_of_references_);
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}
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// Placement new creation.
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static HandleScope* Create(void* storage, BaseHandleScope* link, uint32_t num_references)
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WARN_UNUSED {
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return new (storage) HandleScope(link, num_references);
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}
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// Number of references contained within this handle scope.
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ALWAYS_INLINE uint32_t NumberOfReferences() const {
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DCHECK_GE(number_of_references_, 0);
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return static_cast<uint32_t>(number_of_references_);
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}
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template <typename Visitor>
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ALWAYS_INLINE void VisitRoots(Visitor& visitor) REQUIRES_SHARED(Locks::mutator_lock_);
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protected:
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// Return backing storage used for references.
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ALWAYS_INLINE StackReference<mirror::Object>* GetReferences() const {
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uintptr_t address = reinterpret_cast<uintptr_t>(this) + ReferencesOffset(kRuntimePointerSize);
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return reinterpret_cast<StackReference<mirror::Object>*>(address);
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}
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explicit HandleScope(size_t number_of_references) : HandleScope(nullptr, number_of_references) {}
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// Semi-hidden constructor. Construction expected by generated code and StackHandleScope.
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HandleScope(BaseHandleScope* link, uint32_t num_references)
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: BaseHandleScope(link, num_references) {}
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// Storage for references.
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// StackReference<mirror::Object> references_[number_of_references_]
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private:
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DISALLOW_COPY_AND_ASSIGN(HandleScope);
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};
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// Fixed size handle scope that is not necessarily linked in the thread.
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template<size_t kNumReferences>
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class PACKED(4) FixedSizeHandleScope : public HandleScope {
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public:
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template<class T>
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ALWAYS_INLINE MutableHandle<T> NewHandle(T* object) REQUIRES_SHARED(Locks::mutator_lock_);
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template<class T>
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ALWAYS_INLINE HandleWrapper<T> NewHandleWrapper(T** object)
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REQUIRES_SHARED(Locks::mutator_lock_);
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template<class T>
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ALWAYS_INLINE HandleWrapperObjPtr<T> NewHandleWrapper(ObjPtr<T>* object)
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REQUIRES_SHARED(Locks::mutator_lock_);
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template<class MirrorType>
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ALWAYS_INLINE MutableHandle<MirrorType> NewHandle(ObjPtr<MirrorType> object)
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REQUIRES_SHARED(Locks::mutator_lock_);
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ALWAYS_INLINE void SetReference(size_t i, mirror::Object* object)
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REQUIRES_SHARED(Locks::mutator_lock_);
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size_t RemainingSlots() const {
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return kNumReferences - pos_;
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}
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private:
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explicit ALWAYS_INLINE FixedSizeHandleScope(BaseHandleScope* link,
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mirror::Object* fill_value = nullptr);
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ALWAYS_INLINE ~FixedSizeHandleScope() {}
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template<class T>
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ALWAYS_INLINE MutableHandle<T> GetHandle(size_t i) REQUIRES_SHARED(Locks::mutator_lock_) {
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DCHECK_LT(i, kNumReferences);
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return MutableHandle<T>(&GetReferences()[i]);
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}
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// Reference storage needs to be first as expected by the HandleScope layout.
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StackReference<mirror::Object> storage_[kNumReferences];
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// Position new handles will be created.
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uint32_t pos_ = 0;
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template<size_t kNumRefs> friend class StackHandleScope;
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friend class VariableSizedHandleScope;
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};
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// Scoped handle storage of a fixed size that is stack allocated.
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template<size_t kNumReferences>
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class PACKED(4) StackHandleScope final : public FixedSizeHandleScope<kNumReferences> {
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public:
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explicit ALWAYS_INLINE StackHandleScope(Thread* self, mirror::Object* fill_value = nullptr);
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ALWAYS_INLINE ~StackHandleScope();
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Thread* Self() const {
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return self_;
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}
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private:
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// The thread that the stack handle scope is a linked list upon. The stack handle scope will
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// push and pop itself from this thread.
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Thread* const self_;
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};
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// Utility class to manage a variable sized handle scope by having a list of fixed size handle
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// scopes.
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// Calls to NewHandle will create a new handle inside the current FixedSizeHandleScope.
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// When the current handle scope becomes full a new one is created and put at the front of the
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// list.
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class VariableSizedHandleScope : public BaseHandleScope {
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public:
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explicit VariableSizedHandleScope(Thread* const self);
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~VariableSizedHandleScope();
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template<class T>
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MutableHandle<T> NewHandle(T* object) REQUIRES_SHARED(Locks::mutator_lock_);
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template<class MirrorType>
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MutableHandle<MirrorType> NewHandle(ObjPtr<MirrorType> ptr)
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REQUIRES_SHARED(Locks::mutator_lock_);
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// Number of references contained within this handle scope.
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ALWAYS_INLINE uint32_t NumberOfReferences() const;
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ALWAYS_INLINE bool Contains(StackReference<mirror::Object>* handle_scope_entry) const;
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template <typename Visitor>
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void VisitRoots(Visitor& visitor) REQUIRES_SHARED(Locks::mutator_lock_);
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private:
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static constexpr size_t kMaxLocalScopeSize = 64u;
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// In order to have consistent compilation with both 32bit and 64bit dex2oat
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// binaries we need this to be an actual constant. We picked this because it
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// will ensure that we use <64bit internal scopes.
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static constexpr size_t kNumReferencesPerScope = 12u;
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Thread* const self_;
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// Linked list of fixed size handle scopes.
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using LocalScopeType = FixedSizeHandleScope<kNumReferencesPerScope>;
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static_assert(sizeof(LocalScopeType) <= kMaxLocalScopeSize, "Unexpected size of LocalScopeType");
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LocalScopeType* current_scope_;
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DISALLOW_COPY_AND_ASSIGN(VariableSizedHandleScope);
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};
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} // namespace art
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#endif // ART_RUNTIME_HANDLE_SCOPE_H_
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