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 <__utility/forward.h> 14 #include <__utility/move.h> 15 #include <type_traits> 16 17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 18 #pragma GCC system_header 19 #endif 20 21 _LIBCPP_BEGIN_NAMESPACE_STD 22 23 #if _LIBCPP_STD_VER > 11 24 template<class _T1, class _T2 = _T1> 25 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 26 _T1 exchange(_T1& __obj, _T2&& __new_value) 27 noexcept(is_nothrow_move_constructible<_T1>::value && is_nothrow_assignable<_T1&, _T2>::value) 28 { 29 _T1 __old_value = _VSTD::move(__obj); 30 __obj = _VSTD::forward<_T2>(__new_value); 31 return __old_value; 32 } 33 #endif // _LIBCPP_STD_VER > 11 34 35 _LIBCPP_END_NAMESPACE_STD 36 37 #endif // _LIBCPP___UTILITY_EXCHANGE_H 38