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/*
* Copyright (C) 2014 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_RUNTIME_HANDLE_H_
#define ART_RUNTIME_HANDLE_H_
#include <android-base/logging.h>
#include "base/casts.h"
#include "base/locks.h"
#include "base/macros.h"
#include "base/value_object.h"
#include "jni.h"
#include "obj_ptr.h"
#include "stack_reference.h"
namespace art {
class Thread;
template<class T> class Handle;
template<typename T> class IterationRange;
namespace mirror {
template<typename T> class ObjectArray;
template<typename T, typename C> class ArrayIter;
template<typename T> using HandleArrayIter = ArrayIter<T, Handle<ObjectArray<T>>>;
template<typename T> using ConstHandleArrayIter = ArrayIter<T, const Handle<ObjectArray<T>>>;
} // namespace mirror
// Handles are memory locations that contain GC roots. As the mirror::Object*s within a handle are
// GC visible then the GC may move the references within them, something that couldn't be done with
// a wrap pointer. Handles are generally allocated within HandleScopes. Handle is a super-class
// of MutableHandle and doesn't support assignment operations.
template<class T>
class Handle : public ValueObject {
public:
Handle() : reference_(nullptr) {
}
ALWAYS_INLINE Handle(const Handle<T>& handle) = default;
ALWAYS_INLINE Handle<T>& operator=(const Handle<T>& handle) = default;
template <typename Type,
typename = typename std::enable_if_t<std::is_base_of_v<T, Type>>>
ALWAYS_INLINE Handle(const Handle<Type>& other) : reference_(other.reference_) {
}
ALWAYS_INLINE explicit Handle(StackReference<T>* reference) : reference_(reference) {
}
ALWAYS_INLINE T& operator*() const REQUIRES_SHARED(Locks::mutator_lock_) {
return *Get();
}
ALWAYS_INLINE T* operator->() const REQUIRES_SHARED(Locks::mutator_lock_) {
return Get();
}
ALWAYS_INLINE T* Get() const REQUIRES_SHARED(Locks::mutator_lock_) {
return down_cast<T*>(reference_->AsMirrorPtr());
}
template <typename Type,
typename = typename std::enable_if_t<std::is_same_v<mirror::ObjectArray<Type>, T>>>
ALWAYS_INLINE IterationRange<mirror::ConstHandleArrayIter<Type>> ConstIterate() const
REQUIRES_SHARED(Locks::mutator_lock_) {
return T::ConstIterate(*this);
}
template <typename Type,
typename = typename std::enable_if_t<std::is_same_v<mirror::ObjectArray<Type>, T>>>
ALWAYS_INLINE IterationRange<mirror::HandleArrayIter<Type>> Iterate()
REQUIRES_SHARED(Locks::mutator_lock_) {
return T::Iterate(*this);
}
ALWAYS_INLINE bool IsNull() const {
// It's safe to null-check it without a read barrier.
return reference_->IsNull();
}
ALWAYS_INLINE jobject ToJObject() const REQUIRES_SHARED(Locks::mutator_lock_) {
if (UNLIKELY(reference_->AsMirrorPtr() == nullptr)) {
// Special case so that we work with null handles.
return nullptr;
}
return reinterpret_cast<jobject>(reference_);
}
ALWAYS_INLINE StackReference<mirror::Object>* GetReference() {
return reference_;
}
ALWAYS_INLINE const StackReference<mirror::Object>* GetReference() const {
return reference_;
}
ALWAYS_INLINE bool operator!=(std::nullptr_t) const REQUIRES_SHARED(Locks::mutator_lock_) {
return !IsNull();
}
ALWAYS_INLINE bool operator==(std::nullptr_t) const REQUIRES_SHARED(Locks::mutator_lock_) {
return IsNull();
}
protected:
template<typename S>
explicit Handle(StackReference<S>* reference)
: reference_(reference) {
}
template<typename S>
explicit Handle(const Handle<S>& handle)
: reference_(handle.reference_) {
}
StackReference<mirror::Object>* reference_;
private:
friend class BuildGenericJniFrameVisitor;
template<class S> friend class Handle;
friend class HandleScope;
template<class S> friend class HandleWrapper;
template<size_t kNumReferences> friend class StackHandleScope;
};
// Handles that support assignment.
template<class T>
class MutableHandle : public Handle<T> {
public:
MutableHandle() {
}
ALWAYS_INLINE MutableHandle(const MutableHandle<T>& handle)
REQUIRES_SHARED(Locks::mutator_lock_) = default;
ALWAYS_INLINE MutableHandle<T>& operator=(const MutableHandle<T>& handle)
REQUIRES_SHARED(Locks::mutator_lock_) = default;
ALWAYS_INLINE explicit MutableHandle(StackReference<T>* reference)
REQUIRES_SHARED(Locks::mutator_lock_)
: Handle<T>(reference) {
}
ALWAYS_INLINE T* Assign(T* reference) REQUIRES_SHARED(Locks::mutator_lock_) {
StackReference<mirror::Object>* ref = Handle<T>::GetReference();
T* old = down_cast<T*>(ref->AsMirrorPtr());
ref->Assign(reference);
return old;
}
ALWAYS_INLINE T* Assign(ObjPtr<T> reference) REQUIRES_SHARED(Locks::mutator_lock_) {
StackReference<mirror::Object>* ref = Handle<T>::GetReference();
T* old = down_cast<T*>(ref->AsMirrorPtr());
ref->Assign(reference.Ptr());
return old;
}
template<typename S>
explicit MutableHandle(const MutableHandle<S>& handle) REQUIRES_SHARED(Locks::mutator_lock_)
: Handle<T>(handle) {
}
template<typename S>
explicit MutableHandle(StackReference<S>* reference) REQUIRES_SHARED(Locks::mutator_lock_)
: Handle<T>(reference) {
}
private:
friend class BuildGenericJniFrameVisitor;
friend class HandleScope;
template<class S> friend class HandleWrapper;
template<size_t kNumReferences> friend class StackHandleScope;
};
// A special case of Handle that only holds references to null. Invalid when if it goes out of
// scope. Example: Handle<T> h = ScopedNullHandle<T> will leave h being undefined.
template<class T>
class ScopedNullHandle : public Handle<T> {
public:
ScopedNullHandle() : Handle<T>(&null_ref_) {}
private:
StackReference<mirror::Object> null_ref_;
};
} // namespace art
#endif // ART_RUNTIME_HANDLE_H_
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