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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_MIRROR_OBJ_PTR_H_
#define ART_RUNTIME_MIRROR_OBJ_PTR_H_
#include "base/mutex.h" // For Locks::mutator_lock_.
#include "globals.h"
#include "mirror/object_reference.h"
#include "utils.h"
namespace art {
namespace mirror {
class Object;
// Value type representing a pointer to a mirror::Object of type MirrorType
// Pass kPoison as a template boolean for testing in non-debug builds.
// Note that the functions are not 100% thread safe and may have spurious positive check passes in
// these cases.
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 explicit ObjPtr(MirrorType* ptr) REQUIRES_SHARED(Locks::mutator_lock_)
: reference_(Encode(ptr)) {}
ALWAYS_INLINE explicit ObjPtr(const ObjPtr& other) REQUIRES_SHARED(Locks::mutator_lock_)
= default;
ALWAYS_INLINE ObjPtr& operator=(const ObjPtr& other) {
reference_ = other.reference_;
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 Get();
}
ALWAYS_INLINE MirrorType* Get() const REQUIRES_SHARED(Locks::mutator_lock_) {
return Decode();
}
ALWAYS_INLINE bool IsNull() const {
return reference_ == 0;
}
ALWAYS_INLINE bool IsValid() const REQUIRES_SHARED(Locks::mutator_lock_) {
if (!kPoison || IsNull()) {
return true;
}
return GetCookie() == TrimCookie(Thread::Current()->GetPoisonObjectCookie());
}
ALWAYS_INLINE void AssertValid() const REQUIRES_SHARED(Locks::mutator_lock_) {
if (kPoison) {
CHECK(IsValid()) << "Stale object pointer, expected cookie "
<< TrimCookie(Thread::Current()->GetPoisonObjectCookie()) << " but got " << GetCookie();
}
}
ALWAYS_INLINE bool operator==(const ObjPtr& ptr) const REQUIRES_SHARED(Locks::mutator_lock_) {
return Decode() == ptr.Decode();
}
ALWAYS_INLINE bool operator==(const MirrorType* ptr) const REQUIRES_SHARED(Locks::mutator_lock_) {
return Decode() == ptr;
}
ALWAYS_INLINE bool operator==(std::nullptr_t) const REQUIRES_SHARED(Locks::mutator_lock_) {
return IsNull();
}
ALWAYS_INLINE bool operator!=(const ObjPtr& ptr) const REQUIRES_SHARED(Locks::mutator_lock_) {
return Decode() != ptr.Decode();
}
ALWAYS_INLINE bool operator!=(const MirrorType* ptr) const REQUIRES_SHARED(Locks::mutator_lock_) {
return Decode() != ptr;
}
ALWAYS_INLINE bool operator!=(std::nullptr_t) const REQUIRES_SHARED(Locks::mutator_lock_) {
return !IsNull();
}
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_) {
uintptr_t ref = reinterpret_cast<uintptr_t>(ptr);
if (kPoison && ref != 0) {
DCHECK_LE(ref, 0xFFFFFFFFU);
ref >>= kObjectAlignmentShift;
// Put cookie in high bits.
Thread* self = Thread::Current();
DCHECK(self != nullptr);
ref |= self->GetPoisonObjectCookie() << kCookieShift;
}
return ref;
}
// Decode makes sure that the object pointer is valid.
ALWAYS_INLINE MirrorType* Decode() const REQUIRES_SHARED(Locks::mutator_lock_) {
AssertValid();
if (kPoison) {
return reinterpret_cast<MirrorType*>(
static_cast<uintptr_t>(static_cast<uint32_t>(reference_ << kObjectAlignmentShift)));
} else {
return reinterpret_cast<MirrorType*>(reference_);
}
}
// The encoded reference and cookie.
uintptr_t reference_;
};
} // namespace mirror
} // namespace art
#endif // ART_RUNTIME_MIRROR_OBJ_PTR_H_