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___CONCEPTS_SWAPPABLE_H
10 #define _LIBCPP___CONCEPTS_SWAPPABLE_H
11 
12 #include <__concepts/assignable.h>
13 #include <__concepts/class_or_enum.h>
14 #include <__concepts/common_reference_with.h>
15 #include <__concepts/constructible.h>
16 #include <__config>
17 #include <__type_traits/extent.h>
18 #include <__type_traits/is_nothrow_move_assignable.h>
19 #include <__type_traits/is_nothrow_move_constructible.h>
20 #include <__type_traits/remove_cvref.h>
21 #include <__utility/exchange.h>
22 #include <__utility/forward.h>
23 #include <__utility/move.h>
24 #include <__utility/swap.h>
25 #include <cstddef>
26 
27 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
28 #  pragma GCC system_header
29 #endif
30 
31 _LIBCPP_BEGIN_NAMESPACE_STD
32 
33 #if _LIBCPP_STD_VER > 17
34 
35 // [concept.swappable]
36 
37 namespace ranges {
38 namespace __swap {
39 
40   template<class _Tp>
41   void swap(_Tp&, _Tp&) = delete;
42 
43   template<class _Tp, class _Up>
44   concept __unqualified_swappable_with =
45     (__class_or_enum<remove_cvref_t<_Tp>> || __class_or_enum<remove_cvref_t<_Up>>) &&
46     requires(_Tp&& __t, _Up&& __u) {
47       swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
48     };
49 
50   struct __fn;
51 
52   template<class _Tp, class _Up, size_t _Size>
53   concept __swappable_arrays =
54     !__unqualified_swappable_with<_Tp(&)[_Size], _Up(&)[_Size]> &&
55     extent_v<_Tp> == extent_v<_Up> &&
56     requires(_Tp(& __t)[_Size], _Up(& __u)[_Size], const __fn& __swap) {
57       __swap(__t[0], __u[0]);
58     };
59 
60   template<class _Tp>
61   concept __exchangeable =
62     !__unqualified_swappable_with<_Tp&, _Tp&> &&
63     move_constructible<_Tp> &&
64     assignable_from<_Tp&, _Tp>;
65 
66   struct __fn {
67     // 2.1   `S` is `(void)swap(E1, E2)`* if `E1` or `E2` has class or enumeration type and...
68     // *The name `swap` is used here unqualified.
69     template<class _Tp, class _Up>
70       requires __unqualified_swappable_with<_Tp, _Up>
71     constexpr void operator()(_Tp&& __t, _Up&& __u) const
72       noexcept(noexcept(swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u))))
73     {
74       swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
75     }
76 
77     // 2.2   Otherwise, if `E1` and `E2` are lvalues of array types with equal extent and...
78     template<class _Tp, class _Up, size_t _Size>
79       requires __swappable_arrays<_Tp, _Up, _Size>
80     constexpr void operator()(_Tp(& __t)[_Size], _Up(& __u)[_Size]) const
81       noexcept(noexcept((*this)(*__t, *__u)))
82     {
83       // TODO(cjdb): replace with `ranges::swap_ranges`.
84       for (size_t __i = 0; __i < _Size; ++__i) {
85         (*this)(__t[__i], __u[__i]);
86       }
87     }
88 
89     // 2.3   Otherwise, if `E1` and `E2` are lvalues of the same type `T` that models...
90     template<__exchangeable _Tp>
91     constexpr void operator()(_Tp& __x, _Tp& __y) const
92       noexcept(is_nothrow_move_constructible_v<_Tp> && is_nothrow_move_assignable_v<_Tp>)
93     {
94       __y = _VSTD::exchange(__x, _VSTD::move(__y));
95     }
96   };
97 } // namespace __swap
98 
99 inline namespace __cpo {
100   inline constexpr auto swap = __swap::__fn{};
101 } // namespace __cpo
102 } // namespace ranges
103 
104 template<class _Tp>
105 concept swappable = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
106 
107 template<class _Tp, class _Up>
108 concept swappable_with =
109   common_reference_with<_Tp, _Up> &&
110   requires(_Tp&& __t, _Up&& __u) {
111     ranges::swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Tp>(__t));
112     ranges::swap(_VSTD::forward<_Up>(__u), _VSTD::forward<_Up>(__u));
113     ranges::swap(_VSTD::forward<_Tp>(__t), _VSTD::forward<_Up>(__u));
114     ranges::swap(_VSTD::forward<_Up>(__u), _VSTD::forward<_Tp>(__t));
115   };
116 
117 #endif // _LIBCPP_STD_VER > 17
118 
119 _LIBCPP_END_NAMESPACE_STD
120 
121 #endif // _LIBCPP___CONCEPTS_SWAPPABLE_H
122