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#pragma once
#include "intrusive_ptr.h"
namespace NYT {
////////////////////////////////////////////////////////////////////////////////
// Atomic ptr based on https://github.com/facebook/folly/blob/main/folly/concurrency/AtomicSharedPtr.h
// Operators * and -> for TAtomicIntrusivePtr are useless because it is not safe to work with atomic ptr such way
// Safe usage is to convert to TIntrusivePtr.
// Max TAtomicIntrusivePtr count per object is (2**16 = 2**32 / 2**16).
template <class T>
class TAtomicIntrusivePtr
{
public:
TAtomicIntrusivePtr() = default;
TAtomicIntrusivePtr(std::nullptr_t);
explicit TAtomicIntrusivePtr(TIntrusivePtr<T> other);
TAtomicIntrusivePtr(TAtomicIntrusivePtr&& other);
~TAtomicIntrusivePtr();
TAtomicIntrusivePtr& operator=(TIntrusivePtr<T> other);
TAtomicIntrusivePtr& operator=(std::nullptr_t);
TIntrusivePtr<T> Acquire() const;
TIntrusivePtr<T> Exchange(TIntrusivePtr<T> other);
void Reset();
bool CompareAndSwap(void*& comparePtr, T* target);
bool CompareAndSwap(void*& comparePtr, TIntrusivePtr<T> target);
// Result is suitable only for comparison. Not dereference.
void* Get() const;
explicit operator bool() const;
private:
template <class U>
friend bool operator==(const TAtomicIntrusivePtr<U>& lhs, const TIntrusivePtr<U>& rhs);
template <class U>
friend bool operator==(const TIntrusivePtr<U>& lhs, const TAtomicIntrusivePtr<U>& rhs);
template <class U>
friend bool operator!=(const TAtomicIntrusivePtr<U>& lhs, const TIntrusivePtr<U>& rhs);
template <class U>
friend bool operator!=(const TIntrusivePtr<U>& lhs, const TAtomicIntrusivePtr<U>& rhs);
// Keeps packed pointer (localRefCount, objectPtr).
// Atomic ptr holds N references, where N = ReservedRefCount - localRefCount.
// LocalRefCount is incremented in Acquire method.
// When localRefCount exceeds ReservedRefCount / 2 a new portion of refs are required globally.
// This field is marked mutable in order to make Acquire const-qualified in accordance to its semantics.
mutable std::atomic<char*> Ptr_ = nullptr;
constexpr static int CounterBits = 64 - PtrBits;
constexpr static int ReservedRefCount = (1 << CounterBits) - 1;
// Consume ref if ownership is transferred.
// AcquireObject(ptr.Release(), true)
// AcquireObject(ptr.Get(), false)
static char* AcquireObject(T* obj, bool consumeRef = false);
static void ReleaseObject(void* packedPtr);
static void DoRelease(T* obj, int refs);
};
////////////////////////////////////////////////////////////////////////////////
} // namespace NYT
#define ATOMIC_INTRUSIVE_PTR_INL_H_
#include "atomic_intrusive_ptr-inl.h"
#undef ATOMIC_INTRUSIVE_PTR_INL_H_
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