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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/locks.h" // For Locks::mutator_lock_.
#include "base/macros.h"
#include "runtime_globals.h"
// Always inline ObjPtr methods even in debug builds.
#define OBJPTR_INLINE __attribute__ ((always_inline))
namespace art {
constexpr bool kObjPtrPoisoning = kIsDebugBuild;
// It turns out that most of the performance overhead comes from copying. Don't validate for now.
// This defers finding stale ObjPtr objects until they are used.
constexpr bool kObjPtrPoisoningValidateOnCopy = false;
// Value type representing a pointer to a mirror::Object of type MirrorType
// Since the cookie is thread based, it is not safe to share an ObjPtr between threads.
template<class MirrorType>
class ObjPtr {
static constexpr size_t kCookieShift =
kHeapReferenceSize * 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:
OBJPTR_INLINE ObjPtr() REQUIRES_SHARED(Locks::mutator_lock_) : reference_(0u) {}
// Note: The following constructors allow implicit conversion. This simplifies code that uses
// them, e.g., for parameter passing. However, in general, implicit-conversion constructors
// are discouraged and detected by clang-tidy.
OBJPTR_INLINE ObjPtr(std::nullptr_t)
REQUIRES_SHARED(Locks::mutator_lock_)
: reference_(0u) {}
template <typename Type,
typename = typename std::enable_if<std::is_base_of<MirrorType, Type>::value>::type>
OBJPTR_INLINE ObjPtr(Type* ptr)
REQUIRES_SHARED(Locks::mutator_lock_)
: reference_(Encode(static_cast<MirrorType*>(ptr))) {
}
template <typename Type,
typename = typename std::enable_if<std::is_base_of<MirrorType, Type>::value>::type>
OBJPTR_INLINE ObjPtr(const ObjPtr<Type>& other)
REQUIRES_SHARED(Locks::mutator_lock_)
: reference_(kObjPtrPoisoningValidateOnCopy
? Encode(static_cast<MirrorType*>(other.Ptr()))
: other.reference_) {
}
template <typename Type,
typename = typename std::enable_if<std::is_base_of<MirrorType, Type>::value>::type>
OBJPTR_INLINE ObjPtr& operator=(const ObjPtr<Type>& other)
REQUIRES_SHARED(Locks::mutator_lock_) {
reference_ = kObjPtrPoisoningValidateOnCopy
? Encode(static_cast<MirrorType*>(other.Ptr()))
: other.reference_;
return *this;
}
OBJPTR_INLINE ObjPtr& operator=(MirrorType* ptr) REQUIRES_SHARED(Locks::mutator_lock_) {
Assign(ptr);
return *this;
}
OBJPTR_INLINE void Assign(MirrorType* ptr) REQUIRES_SHARED(Locks::mutator_lock_) {
reference_ = Encode(ptr);
}
OBJPTR_INLINE MirrorType* operator->() const REQUIRES_SHARED(Locks::mutator_lock_) {
return Ptr();
}
OBJPTR_INLINE bool IsNull() const {
return reference_ == 0;
}
// Ptr makes sure that the object pointer is valid.
OBJPTR_INLINE MirrorType* Ptr() const REQUIRES_SHARED(Locks::mutator_lock_) {
AssertValid();
return PtrUnchecked();
}
OBJPTR_INLINE bool IsValid() const REQUIRES_SHARED(Locks::mutator_lock_);
OBJPTR_INLINE void AssertValid() const REQUIRES_SHARED(Locks::mutator_lock_);
OBJPTR_INLINE bool operator==(const ObjPtr& ptr) const REQUIRES_SHARED(Locks::mutator_lock_) {
return Ptr() == ptr.Ptr();
}
template <typename PointerType>
OBJPTR_INLINE bool operator==(const PointerType* ptr) const
REQUIRES_SHARED(Locks::mutator_lock_) {
return Ptr() == ptr;
}
OBJPTR_INLINE bool operator==(std::nullptr_t) const {
return IsNull();
}
OBJPTR_INLINE bool operator!=(const ObjPtr& ptr) const REQUIRES_SHARED(Locks::mutator_lock_) {
return Ptr() != ptr.Ptr();
}
template <typename PointerType>
OBJPTR_INLINE bool operator!=(const PointerType* ptr) const
REQUIRES_SHARED(Locks::mutator_lock_) {
return Ptr() != ptr;
}
OBJPTR_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.
OBJPTR_INLINE MirrorType* PtrUnchecked() const {
if (kObjPtrPoisoning) {
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.
OBJPTR_INLINE static uintptr_t GetCurrentTrimedCookie();
OBJPTR_INLINE uintptr_t GetCookie() const {
return reference_ >> kCookieShift;
}
OBJPTR_INLINE static uintptr_t Encode(MirrorType* ptr) REQUIRES_SHARED(Locks::mutator_lock_);
// The encoded reference and cookie.
uintptr_t reference_;
template <class T> friend class ObjPtr; // Required for reference_ access in copy cons/operator.
};
static_assert(std::is_trivially_copyable<ObjPtr<void>>::value,
"ObjPtr should be trivially copyable");
// Hash function for stl data structures.
class HashObjPtr {
public:
template<class MirrorType>
size_t operator()(const ObjPtr<MirrorType>& ptr) const NO_THREAD_SAFETY_ANALYSIS {
return std::hash<MirrorType*>()(ptr.Ptr());
}
};
template<class MirrorType, typename PointerType>
OBJPTR_INLINE bool operator==(const PointerType* a, const ObjPtr<MirrorType>& b)
REQUIRES_SHARED(Locks::mutator_lock_) {
return b == a;
}
template<class MirrorType>
OBJPTR_INLINE bool operator==(std::nullptr_t, const ObjPtr<MirrorType>& b) {
return b == nullptr;
}
template<typename MirrorType, typename PointerType>
OBJPTR_INLINE bool operator!=(const PointerType* a, const ObjPtr<MirrorType>& b)
REQUIRES_SHARED(Locks::mutator_lock_) {
return b != a;
}
template<class MirrorType>
OBJPTR_INLINE bool operator!=(std::nullptr_t, const ObjPtr<MirrorType>& b) {
return b != nullptr;
}
template<class MirrorType>
static inline ObjPtr<MirrorType> MakeObjPtr(MirrorType* ptr) {
return ObjPtr<MirrorType>(ptr);
}
template<class MirrorType>
static inline ObjPtr<MirrorType> MakeObjPtr(ObjPtr<MirrorType> ptr) {
return ObjPtr<MirrorType>(ptr);
}
template<class MirrorType>
OBJPTR_INLINE std::ostream& operator<<(std::ostream& os, ObjPtr<MirrorType> ptr);
} // namespace art
#endif // ART_RUNTIME_OBJ_PTR_H_