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#pragma once
#include "ref_counted.h"
#include <type_traits>
namespace NYT {
////////////////////////////////////////////////////////////////////////////////
//! A downcast that succeeds iff the object was allocated as *exactly* |New<T>()|
//! (not a subclass, not some other allocation path).
/*!
* |New<T>()| does not construct a |T| but a final |TRefCountedWrapper<T>|
* deriving from |T|, so |T| is never a leaf and |dynamic_cast<T*>| takes the
* slow is-a path. This casts to the wrapper instead and upcasts back to |T*|;
* since the wrapper is final, dynamic_cast lowers to one type_info compare --
* O(1), as cheap on a miss as on a hit.
*
* Pointer form returns |nullptr| on a miss (or null operand); reference form
* throws |std::bad_cast|. Constness is preserved. |T| must derive from
* |TRefCountedBase| and |U| must be polymorphic. Requires RTTI.
*/
template <class T, class U>
[[nodiscard]] std::conditional_t<std::is_const_v<U>, const T, T>* ExactRefCountedCast(U* ptr) noexcept;
template <class T, class U>
[[nodiscard]] std::conditional_t<std::is_const_v<U>, const T, T>& ExactRefCountedCast(U& ref);
////////////////////////////////////////////////////////////////////////////////
} // namespace NYT
#define EXACT_REF_COUNTED_CAST_INL_H_
#include "exact_ref_counted_cast-inl.h"
#undef EXACT_REF_COUNTED_CAST_INL_H_
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