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#pragma once
#include "ref_counted.h"
#include <util/generic/hash.h>
namespace NYT {
////////////////////////////////////////////////////////////////////////////////
template <class T>
class TWeakPtr
{
public:
using TUnderlying = T;
using element_type = T;
//! Default constructor.
TWeakPtr() = default;
//! Null constructor.
TWeakPtr(std::nullptr_t);
//! Constructor from an unqualified reference.
/*!
* Note that this constructor could be racy due to unsynchronized operations
* on the object and on the counter.
*/
explicit TWeakPtr(T* p) noexcept;
//! Constructor from a strong reference.
TWeakPtr(const TIntrusivePtr<T>& ptr) noexcept;
//! Constructor from a strong reference with an upcast.
template <class U, class = typename std::enable_if_t<std::is_convertible_v<U*, T*>>>
TWeakPtr(const TIntrusivePtr<U>& ptr) noexcept;
//! Copy constructor.
TWeakPtr(const TWeakPtr& other) noexcept;
//! Copy constructor with an upcast.
template <class U, class = typename std::enable_if_t<std::is_convertible_v<U*, T*>>>
TWeakPtr(const TWeakPtr<U>& other) noexcept;
//! Move constructor.
TWeakPtr(TWeakPtr&& other) noexcept;
//! Move constructor with an upcast.
template <class U, class = typename std::enable_if_t<std::is_convertible_v<U*, T*>>>
TWeakPtr(TWeakPtr<U>&& other) noexcept;
//! Destructor.
~TWeakPtr();
//! Assignment operator from a strong reference.
template <class U>
TWeakPtr& operator=(const TIntrusivePtr<U>& ptr) noexcept;
//! Copy assignment operator.
TWeakPtr& operator=(const TWeakPtr& other) noexcept;
//! Copy assignment operator with an upcast.
template <class U>
TWeakPtr& operator=(const TWeakPtr<U>& other) noexcept;
//! Move assignment operator.
TWeakPtr& operator=(TWeakPtr&& other) noexcept;
//! Move assignment operator with an upcast.
template <class U>
TWeakPtr& operator=(TWeakPtr<U>&& other) noexcept;
//! Drop the pointer.
void Reset(); // noexcept
//! Replace the pointer with a specified one.
void Reset(T* p); // noexcept
//! Replace the pointer with a specified one.
template <class U>
void Reset(const TIntrusivePtr<U>& ptr); // noexcept
//! Swap the pointer with the other one.
void Swap(TWeakPtr& other) noexcept;
//! Acquire a strong reference to the pointee and return a strong pointer.
TIntrusivePtr<T> Lock() const noexcept;
//! Returns true if the pointee is null or already expired.
bool IsExpired() const noexcept;
//! Returns the underlying raw pointer. Note that it may point to an already
//! expired object.
T* Get() const noexcept;
private:
void AcquireRef();
void ReleaseRef();
template <class U>
friend class TWeakPtr;
T* T_ = nullptr;
#if defined(_tsan_enabled_)
const TRefCounter* RefCounter_ = nullptr;
#endif
const TRefCounter* GetRefCounterImpl() const;
const TRefCounter* TryGetRefCounterImpl() const;
};
////////////////////////////////////////////////////////////////////////////////
template <class T1, class T2>
bool operator==(const TWeakPtr<T1>& lhs, const TWeakPtr<T2>& rhs);
template <class T1, class T2>
bool operator==(const TIntrusivePtr<T1>& lhs, const TWeakPtr<T2>& rhs);
template <class T1, class T2>
bool operator==(const TWeakPtr<T1>& lhs, const TIntrusivePtr<T2>& rhs);
template <class T1, class T2>
bool operator==(T1* lhs, const TWeakPtr<T2>& rhs);
template <class T1, class T2>
bool operator==(const TWeakPtr<T1>& lhs, T2* rhs);
template <class T2>
bool operator==(std::nullptr_t, const TWeakPtr<T2>& rhs);
template <class T1>
bool operator==(const TWeakPtr<T1>& lhs, std::nullptr_t);
////////////////////////////////////////////////////////////////////////////////
//! Creates a weak pointer wrapper for a given raw pointer.
//! Compared to |TWeakPtr<T>::ctor|, type inference enables omitting |T|.
template <class T>
TWeakPtr<T> MakeWeak(T* p);
//! Creates a weak pointer wrapper for a given intrusive pointer.
//! Compared to |TWeakPtr<T>::ctor|, type inference enables omitting |T|.
template <class T>
TWeakPtr<T> MakeWeak(const TIntrusivePtr<T>& p);
//! A helper for acquiring weak pointer for pointee, resetting intrusive pointer and then
//! returning the pointee reference count using the acquired weak pointer.
//! This helper is designed for best effort in checking that the object is not leaked after
//! destructing (what seems to be) the last pointer to it.
//! NB: it is possible to rewrite this helper making it working event with intrinsic refcounted objects,
//! but it requires much nastier integration with the intrusive pointer destruction routines.
template <typename T>
int ResetAndGetResidualRefCount(TIntrusivePtr<T>& pointer);
////////////////////////////////////////////////////////////////////////////////
struct TTransparentWeakPtrHasher
{
using is_transparent = void;
template <class T>
std::size_t operator()(const TWeakPtr<T>& ptr) const;
template <class T>
std::size_t operator()(const TIntrusivePtr<T>& ptr) const;
template <class T>
std::size_t operator()(T* ptr) const;
};
////////////////////////////////////////////////////////////////////////////////
} // namespace NYT
template <class T>
struct THash<NYT::TWeakPtr<T>>
{
size_t operator()(const NYT::TWeakPtr<T>& ptr) const;
};
#define WEAK_PTR_INL_H_
#include "weak_ptr-inl.h"
#undef WEAK_PTR_INL_H_
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