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 >= 20
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>>) &&
requires(_Tp && __t,_Up && __u)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>
operator__fn71 _LIBCPP_HIDE_FROM_ABI 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>
operator__fn80 _LIBCPP_HIDE_FROM_ABI 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>
operator__fn91 _LIBCPP_HIDE_FROM_ABI 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>
requires(_Tp & __a,_Tp & __b)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> &&
requires(_Tp && __t,_Up && __u)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 >= 20
118
119 _LIBCPP_END_NAMESPACE_STD
120
121 #endif // _LIBCPP___CONCEPTS_SWAPPABLE_H
122