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_PUSH_MACROS
32#include <__undef_macros>
33
34_LIBCPP_BEGIN_NAMESPACE_STD
35
36#if _LIBCPP_STD_VER >= 20
37
38// [concept.swappable]
39
40namespace ranges {
41namespace __swap {
42
43template <class _Tp>
44void swap(_Tp&, _Tp&) = delete;
45
46// clang-format off
47template <class _Tp, class _Up>
48concept __unqualified_swappable_with =
49    (__class_or_enum<remove_cvref_t<_Tp>> || __class_or_enum<remove_cvref_t<_Up>>) &&
50    requires(_Tp&& __t, _Up&& __u) {
51        swap(std::forward<_Tp>(__t), std::forward<_Up>(__u));
52    };
53// clang-format on
54
55struct __fn;
56
57// clang-format off
58template <class _Tp, class _Up, size_t _Size>
59concept __swappable_arrays =
60    !__unqualified_swappable_with<_Tp (&)[_Size], _Up (&)[_Size]> &&
61    extent_v<_Tp> == extent_v<_Up> &&
62    requires(_Tp (&__t)[_Size], _Up (&__u)[_Size], const __fn& __swap) {
63        __swap(__t[0], __u[0]);
64    };
65// clang-format on
66
67template <class _Tp>
68concept __exchangeable =
69    !__unqualified_swappable_with<_Tp&, _Tp&> && move_constructible<_Tp> && assignable_from<_Tp&, _Tp>;
70
71struct __fn {
72  // 2.1   `S` is `(void)swap(E1, E2)`* if `E1` or `E2` has class or enumeration type and...
73  // *The name `swap` is used here unqualified.
74  template <class _Tp, class _Up>
75    requires __unqualified_swappable_with<_Tp, _Up>
76  _LIBCPP_HIDE_FROM_ABI constexpr void operator()(_Tp&& __t, _Up&& __u) const
77      noexcept(noexcept(swap(std::forward<_Tp>(__t), std::forward<_Up>(__u)))) {
78    swap(std::forward<_Tp>(__t), std::forward<_Up>(__u));
79  }
80
81  // 2.2   Otherwise, if `E1` and `E2` are lvalues of array types with equal extent and...
82  template <class _Tp, class _Up, size_t _Size>
83    requires __swappable_arrays<_Tp, _Up, _Size>
84  _LIBCPP_HIDE_FROM_ABI constexpr void operator()(_Tp (&__t)[_Size], _Up (&__u)[_Size]) const
85      noexcept(noexcept((*this)(*__t, *__u))) {
86    // TODO(cjdb): replace with `ranges::swap_ranges`.
87    for (size_t __i = 0; __i < _Size; ++__i) {
88      (*this)(__t[__i], __u[__i]);
89    }
90  }
91
92  // 2.3   Otherwise, if `E1` and `E2` are lvalues of the same type `T` that models...
93  template <__exchangeable _Tp>
94  _LIBCPP_HIDE_FROM_ABI constexpr void operator()(_Tp& __x, _Tp& __y) const
95      noexcept(is_nothrow_move_constructible_v<_Tp> && is_nothrow_move_assignable_v<_Tp>) {
96    __y = std::exchange(__x, std::move(__y));
97  }
98};
99} // namespace __swap
100
101inline namespace __cpo {
102inline constexpr auto swap = __swap::__fn{};
103} // namespace __cpo
104} // namespace ranges
105
106template <class _Tp>
107concept swappable = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
108
109template <class _Tp, class _Up>
110concept swappable_with = common_reference_with<_Tp, _Up> && requires(_Tp&& __t, _Up&& __u) {
111  ranges::swap(std::forward<_Tp>(__t), std::forward<_Tp>(__t));
112  ranges::swap(std::forward<_Up>(__u), std::forward<_Up>(__u));
113  ranges::swap(std::forward<_Tp>(__t), std::forward<_Up>(__u));
114  ranges::swap(std::forward<_Up>(__u), std::forward<_Tp>(__t));
115};
116
117#endif // _LIBCPP_STD_VER >= 20
118
119_LIBCPP_END_NAMESPACE_STD
120
121_LIBCPP_POP_MACROS
122
123#endif // _LIBCPP___CONCEPTS_SWAPPABLE_H
124