chromium/third_party/libc++/src/include/__stop_token/intrusive_shared_ptr.h

// -*- C++ -*-
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef _LIBCPP___STOP_TOKEN_INTRUSIVE_SHARED_PTR_H
#define _LIBCPP___STOP_TOKEN_INTRUSIVE_SHARED_PTR_H

#include <__atomic/atomic.h>
#include <__atomic/memory_order.h>
#include <__config>
#include <__type_traits/is_reference.h>
#include <__utility/move.h>
#include <__utility/swap.h>
#include <cstddef>

#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
#  pragma GCC system_header
#endif

_LIBCPP_PUSH_MACROS
#include <__undef_macros>

_LIBCPP_BEGIN_NAMESPACE_STD

#if _LIBCPP_STD_VER >= 20

// For intrusive_shared_ptr to work with a type T, specialize __intrusive_shared_ptr_traits<T> and implement
// the following function:
//
// static std::atomic<U>& __get_atomic_ref_count(T&);
//
// where U must be an integral type representing the number of references to the object.
template <class _Tp>
struct __intrusive_shared_ptr_traits;

// A reference counting shared_ptr for types whose reference counter
// is stored inside the class _Tp itself.
// When the reference count goes to zero, the destructor of _Tp will be called
template <class _Tp>
struct __intrusive_shared_ptr { … };

#endif // _LIBCPP_STD_VER >= 20

_LIBCPP_END_NAMESPACE_STD

_LIBCPP_POP_MACROS

#endif // _LIBCPP___STOP_TOKEN_INTRUSIVE_SHARED_PTR_H