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/*
* Copyright (C) 2016 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_OBJ_PTR_H_
#define ART_RUNTIME_OBJ_PTR_H_
#include <ostream>
#include <type_traits>
#include "base/mutex.h" // For Locks::mutator_lock_.
#include "globals.h"
#include "mirror/object_reference.h"
namespace art {
// Value type representing a pointer to a mirror::Object of type MirrorType
// Pass kPoison as a template boolean for testing in non-debug builds.
// Since the cookie is thread based, it is not safe to share an ObjPtr between threads.
template<class MirrorType, bool kPoison = kIsDebugBuild>
class ObjPtr {
static constexpr size_t kCookieShift =
sizeof(mirror::HeapReference<mirror::Object>) * kBitsPerByte - kObjectAlignmentShift;
static constexpr size_t kCookieBits = sizeof(uintptr_t) * kBitsPerByte - kCookieShift;
static constexpr uintptr_t kCookieMask = (static_cast<uintptr_t>(1u) << kCookieBits) - 1;
static_assert(kCookieBits >= kObjectAlignmentShift,
"must have a least kObjectAlignmentShift bits");
public:
ALWAYS_INLINE ObjPtr() REQUIRES_SHARED(Locks::mutator_lock_) : reference_(0u) {}
ALWAYS_INLINE ObjPtr(std::nullptr_t) REQUIRES_SHARED(Locks::mutator_lock_) : reference_(0u) {}
template <typename Type>
ALWAYS_INLINE ObjPtr(Type* ptr) REQUIRES_SHARED(Locks::mutator_lock_)
: reference_(Encode(static_cast<MirrorType*>(ptr))) {
static_assert(std::is_base_of<MirrorType, Type>::value,
"Input type must be a subtype of the ObjPtr type");
}
template <typename Type>
ALWAYS_INLINE ObjPtr(const ObjPtr<Type, kPoison>& other) REQUIRES_SHARED(Locks::mutator_lock_)
: reference_(Encode(static_cast<MirrorType*>(other.Ptr()))) {
static_assert(std::is_base_of<MirrorType, Type>::value,
"Input type must be a subtype of the ObjPtr type");
}
template <typename Type>
ALWAYS_INLINE ObjPtr& operator=(const ObjPtr<Type, kPoison>& other)
REQUIRES_SHARED(Locks::mutator_lock_) {
static_assert(std::is_base_of<MirrorType, Type>::value,
"Input type must be a subtype of the ObjPtr type");
reference_ = Encode(static_cast<MirrorType*>(other.Ptr()));
return *this;
}
ALWAYS_INLINE ObjPtr& operator=(MirrorType* ptr) REQUIRES_SHARED(Locks::mutator_lock_) {
Assign(ptr);
return *this;
}
ALWAYS_INLINE void Assign(MirrorType* ptr) REQUIRES_SHARED(Locks::mutator_lock_) {
reference_ = Encode(ptr);
}
ALWAYS_INLINE MirrorType* operator->() const REQUIRES_SHARED(Locks::mutator_lock_) {
return Ptr();
}
ALWAYS_INLINE bool IsNull() const {
return reference_ == 0;
}
// Ptr makes sure that the object pointer is valid.
ALWAYS_INLINE MirrorType* Ptr() const REQUIRES_SHARED(Locks::mutator_lock_) {
AssertValid();
return PtrUnchecked();
}
ALWAYS_INLINE bool IsValid() const REQUIRES_SHARED(Locks::mutator_lock_);
ALWAYS_INLINE void AssertValid() const REQUIRES_SHARED(Locks::mutator_lock_);
ALWAYS_INLINE bool operator==(const ObjPtr& ptr) const REQUIRES_SHARED(Locks::mutator_lock_) {
return Ptr() == ptr.Ptr();
}
template <typename PointerType>
ALWAYS_INLINE bool operator==(const PointerType* ptr) const
REQUIRES_SHARED(Locks::mutator_lock_) {
return Ptr() == ptr;
}
ALWAYS_INLINE bool operator==(std::nullptr_t) const {
return IsNull();
}
ALWAYS_INLINE bool operator!=(const ObjPtr& ptr) const REQUIRES_SHARED(Locks::mutator_lock_) {
return Ptr() != ptr.Ptr();
}
template <typename PointerType>
ALWAYS_INLINE bool operator!=(const PointerType* ptr) const
REQUIRES_SHARED(Locks::mutator_lock_) {
return Ptr() != ptr;
}
ALWAYS_INLINE bool operator!=(std::nullptr_t) const {
return !IsNull();
}
// Ptr unchecked does not check that object pointer is valid. Do not use if you can avoid it.
ALWAYS_INLINE MirrorType* PtrUnchecked() const {
if (kPoison) {
return reinterpret_cast<MirrorType*>(
static_cast<uintptr_t>(static_cast<uint32_t>(reference_ << kObjectAlignmentShift)));
} else {
return reinterpret_cast<MirrorType*>(reference_);
}
}
// Static function to be friendly with null pointers.
template <typename SourceType>
static ObjPtr<MirrorType> DownCast(ObjPtr<SourceType> ptr) REQUIRES_SHARED(Locks::mutator_lock_) {
static_assert(std::is_base_of<SourceType, MirrorType>::value,
"Target type must be a subtype of source type");
return static_cast<MirrorType*>(ptr.Ptr());
}
private:
// Trim off high bits of thread local cookie.
ALWAYS_INLINE static uintptr_t TrimCookie(uintptr_t cookie) {
return cookie & kCookieMask;
}
ALWAYS_INLINE uintptr_t GetCookie() const {
return reference_ >> kCookieShift;
}
ALWAYS_INLINE static uintptr_t Encode(MirrorType* ptr) REQUIRES_SHARED(Locks::mutator_lock_);
// The encoded reference and cookie.
uintptr_t reference_;
};
template<class MirrorType, bool kPoison, typename PointerType>
ALWAYS_INLINE bool operator==(const PointerType* a, const ObjPtr<MirrorType, kPoison>& b)
REQUIRES_SHARED(Locks::mutator_lock_) {
return b == a;
}
template<class MirrorType, bool kPoison>
ALWAYS_INLINE bool operator==(std::nullptr_t, const ObjPtr<MirrorType, kPoison>& b) {
return b == nullptr;
}
template<typename MirrorType, bool kPoison, typename PointerType>
ALWAYS_INLINE bool operator!=(const PointerType* a, const ObjPtr<MirrorType, kPoison>& b)
REQUIRES_SHARED(Locks::mutator_lock_) {
return b != a;
}
template<class MirrorType, bool kPoison>
ALWAYS_INLINE bool operator!=(std::nullptr_t, const ObjPtr<MirrorType, kPoison>& b) {
return b != nullptr;
}
template<class MirrorType, bool kPoison = kIsDebugBuild>
static inline ObjPtr<MirrorType, kPoison> MakeObjPtr(MirrorType* ptr) {
return ObjPtr<MirrorType, kPoison>(ptr);
}
template<class MirrorType, bool kPoison = kIsDebugBuild>
static inline ObjPtr<MirrorType, kPoison> MakeObjPtr(ObjPtr<MirrorType, kPoison> ptr) {
return ObjPtr<MirrorType, kPoison>(ptr);
}
template<class MirrorType, bool kPoison>
ALWAYS_INLINE std::ostream& operator<<(std::ostream& os, ObjPtr<MirrorType, kPoison> ptr);
} // namespace art
#endif // ART_RUNTIME_OBJ_PTR_H_
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