1//===----------------------------------------------------------------------===// 2// 3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4// See https://llvm.org/LICENSE.txt for license information. 5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6// 7//===----------------------------------------------------------------------===// 8 9#ifndef _LIBCPP___UTILITY_EXCHANGE_H 10#define _LIBCPP___UTILITY_EXCHANGE_H 11 12#include <__config> 13#include <__type_traits/is_nothrow_assignable.h> 14#include <__type_traits/is_nothrow_move_constructible.h> 15#include <__utility/forward.h> 16#include <__utility/move.h> 17 18#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 19# pragma GCC system_header 20#endif 21 22_LIBCPP_PUSH_MACROS 23#include <__undef_macros> 24 25_LIBCPP_BEGIN_NAMESPACE_STD 26 27#if _LIBCPP_STD_VER >= 14 28template <class _T1, class _T2 = _T1> 29inline _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 _T1 exchange(_T1& __obj, _T2&& __new_value) noexcept( 30 is_nothrow_move_constructible<_T1>::value && is_nothrow_assignable<_T1&, _T2>::value) { 31 _T1 __old_value = std::move(__obj); 32 __obj = std::forward<_T2>(__new_value); 33 return __old_value; 34} 35#endif // _LIBCPP_STD_VER >= 14 36 37_LIBCPP_END_NAMESPACE_STD 38 39_LIBCPP_POP_MACROS 40 41#endif // _LIBCPP___UTILITY_EXCHANGE_H 42