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
37namespace ranges {
38namespace __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
99inline namespace __cpo {
100  inline constexpr auto swap = __swap::__fn{};
101} // namespace __cpo
102} // namespace ranges
103
104template<class _Tp>
105concept swappable = requires(_Tp& __a, _Tp& __b) { ranges::swap(__a, __b); };
106
107template<class _Tp, class _Up>
108concept 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