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_BEGIN_NAMESPACE_STD 23 24 #if _LIBCPP_STD_VER > 11 25 template<class _T1, class _T2 = _T1> 26 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_SINCE_CXX20 27 _T1 exchange(_T1& __obj, _T2&& __new_value) 28 noexcept(is_nothrow_move_constructible<_T1>::value && is_nothrow_assignable<_T1&, _T2>::value) 29 { 30 _T1 __old_value = _VSTD::move(__obj); 31 __obj = _VSTD::forward<_T2>(__new_value); 32 return __old_value; 33 } 34 #endif // _LIBCPP_STD_VER > 11 35 36 _LIBCPP_END_NAMESPACE_STD 37 38 #endif // _LIBCPP___UTILITY_EXCHANGE_H 39