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