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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 "base/casts.h"
#include "base/logging.h"
#include "base/macros.h"
#include "stack.h"
namespace art {
class Thread;
template<class T> class Handle;
// 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. ConstHandle is a super-class
// of Handle and doesn't support assignment operations.
template<class T>
class ConstHandle {
public:
ConstHandle() : reference_(nullptr) {
}
ALWAYS_INLINE ConstHandle(const ConstHandle<T>& handle) : reference_(handle.reference_) {
}
ALWAYS_INLINE ConstHandle<T>& operator=(const ConstHandle<T>& handle) {
reference_ = handle.reference_;
return *this;
}
ALWAYS_INLINE explicit ConstHandle(StackReference<T>* reference) : reference_(reference) {
}
ALWAYS_INLINE T& operator*() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
return *Get();
}
ALWAYS_INLINE T* operator->() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
return Get();
}
ALWAYS_INLINE T* Get() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
return reference_->AsMirrorPtr();
}
ALWAYS_INLINE jobject ToJObject() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
if (UNLIKELY(reference_->AsMirrorPtr() == nullptr)) {
// Special case so that we work with NullHandles.
return nullptr;
}
return reinterpret_cast<jobject>(reference_);
}
protected:
StackReference<T>* reference_;
template<typename S>
explicit ConstHandle(StackReference<S>* reference)
: reference_(reinterpret_cast<StackReference<T>*>(reference)) {
}
template<typename S>
explicit ConstHandle(const ConstHandle<S>& handle)
: reference_(reinterpret_cast<StackReference<T>*>(handle.reference_)) {
}
StackReference<T>* GetReference() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) ALWAYS_INLINE {
return reference_;
}
ALWAYS_INLINE const StackReference<T>* GetReference() const
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
return reference_;
}
private:
friend class BuildGenericJniFrameVisitor;
template<class S> friend class ConstHandle;
friend class HandleScope;
template<class S> friend class HandleWrapper;
template<size_t kNumReferences> friend class StackHandleScope;
};
// Handles that support assignment.
template<class T>
class Handle : public ConstHandle<T> {
public:
Handle() {
}
ALWAYS_INLINE Handle(const Handle<T>& handle) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
: ConstHandle<T>(handle.reference_) {
}
ALWAYS_INLINE Handle<T>& operator=(const Handle<T>& handle)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
ConstHandle<T>::operator=(handle);
return *this;
}
ALWAYS_INLINE explicit Handle(StackReference<T>* reference)
SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
: ConstHandle<T>(reference) {
}
ALWAYS_INLINE T* Assign(T* reference) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
StackReference<T>* ref = ConstHandle<T>::GetReference();
T* const old = ref->AsMirrorPtr();
ref->Assign(reference);
return old;
}
template<typename S>
explicit Handle(const Handle<S>& handle) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
: ConstHandle<T>(handle) {
}
protected:
template<typename S>
explicit Handle(StackReference<S>* reference) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
: ConstHandle<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.
template<class T>
class NullHandle : public Handle<T> {
public:
NullHandle() : Handle<T>(&null_ref_) {
}
private:
StackReference<T> null_ref_;
};
} // namespace art
#endif // ART_RUNTIME_HANDLE_H_
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