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 <__cstddef/size_t.h>
18#include <__type_traits/extent.h>
19#include <__type_traits/is_nothrow_assignable.h>
20#include <__type_traits/is_nothrow_constructible.h>
21#include <__type_traits/remove_cvref.h>
22#include <__utility/exchange.h>
23#include <__utility/forward.h>
24#include <__utility/move.h>
25
26#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
27# pragma GCC system_header
28#endif
29
30_LIBCPP_PUSH_MACROS
31#include <__undef_macros>
32
33_LIBCPP_BEGIN_NAMESPACE_STD
34
35#if _LIBCPP_STD_VER >= 20
36
37// [concept.swappable]
38
39namespace ranges {
40namespace __swap {
41
42template <class _Tp>
43void swap(_Tp&, _Tp&) = delete;
44
45// clang-format off
46template <class _Tp, class _Up>
47concept __unqualified_swappable_with =
48 (__class_or_enum<remove_cvref_t<_Tp>> || __class_or_enum<remove_cvref_t<_Up>>) &&
49 requires(_Tp&& __t, _Up&& __u) {
50 swap(std::forward<_Tp>(__t), std::forward<_Up>(__u));
51 };
52// clang-format on
53
54struct __fn;
55
56// clang-format off
57template <class _Tp, class _Up, size_t _Size>
58concept __swappable_arrays =
59 !__unqualified_swappable_with<_Tp (&)[_Size], _Up (&)[_Size]> &&
60 extent_v<_Tp> == extent_v<_Up> &&
61 requires(_Tp (&__t)[_Size], _Up (&__u)[_Size], const __fn& __swap) {
62 __swap(__t[0], __u[0]);
63 };
64// clang-format on
65
66template <class _Tp>
67concept __exchangeable =
68 !__unqualified_swappable_with<_Tp&, _Tp&> && move_constructible<_Tp> && assignable_from<_Tp&, _Tp>;
69
70struct __fn {
71 // 2.1 `S` is `(void)swap(E1, E2)`* if `E1` or `E2` has class or enumeration type and...
72 // *The name `swap` is used here unqualified.
73 template <class _Tp, class _Up>
74 requires __unqualified_swappable_with<_Tp, _Up>
75 _LIBCPP_HIDE_FROM_ABI constexpr void operator()(_Tp&& __t, _Up&& __u) const
76 noexcept(noexcept(swap(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
77 swap(std::forward<_Tp>(__t), std::forward<_Up>(__u));
78 }
79
80 // 2.2 Otherwise, if `E1` and `E2` are lvalues of array types with equal extent and...
81 template <class _Tp, class _Up, size_t _Size>
82 requires __swappable_arrays<_Tp, _Up, _Size>
83 _LIBCPP_HIDE_FROM_ABI constexpr void operator()(_Tp (&__t)[_Size], _Up (&__u)[_Size]) const
84 noexcept(noexcept((*this)(*__t, *__u))) {
85 // TODO(cjdb): replace with `ranges::swap_ranges`.
86 for (size_t __i = 0; __i < _Size; ++__i) {
87 (*this)(__t[__i], __u[__i]);
88 }
89 }
90
91 // 2.3 Otherwise, if `E1` and `E2` are lvalues of the same type `T` that models...
92 template <__exchangeable _Tp>
93 _LIBCPP_HIDE_FROM_ABI constexpr void operator()(_Tp& __x, _Tp& __y) const
94 noexcept(is_nothrow_move_constructible_v<_Tp> && is_nothrow_move_assignable_v<_Tp>) {
95 __y = std::exchange(__x, std::move(__y));
96 }
97};
98} // namespace __swap
99
100inline namespace __cpo {
101inline constexpr auto swap = __swap::__fn{};
102} // namespace __cpo
103} // namespace ranges
104
105template <class _Tp>
106concept swappable = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
107
108template <class _Tp, class _Up>
109concept swappable_with = common_reference_with<_Tp, _Up> && requires(_Tp&& __t, _Up&& __u) {
110 ranges::swap(std::forward<_Tp>(__t), std::forward<_Tp>(__t));
111 ranges::swap(std::forward<_Up>(__u), std::forward<_Up>(__u));
112 ranges::swap(std::forward<_Tp>(__t), std::forward<_Up>(__u));
113 ranges::swap(std::forward<_Up>(__u), std::forward<_Tp>(__t));
114};
115
116#endif // _LIBCPP_STD_VER >= 20
117
118_LIBCPP_END_NAMESPACE_STD
119
120_LIBCPP_POP_MACROS
121
122#endif // _LIBCPP___CONCEPTS_SWAPPABLE_H
123