1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___RANGES_SINGLE_VIEW_H
11#define _LIBCPP___RANGES_SINGLE_VIEW_H
12
13#include <__concepts/constructible.h>
14#include <__config>
15#include <__cstddef/ptrdiff_t.h>
16#include <__cstddef/size_t.h>
17#include <__ranges/movable_box.h>
18#include <__ranges/range_adaptor.h>
19#include <__ranges/view_interface.h>
20#include <__type_traits/decay.h>
21#include <__type_traits/is_object.h>
22#include <__utility/forward.h>
23#include <__utility/in_place.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
37namespace ranges {
38# if _LIBCPP_STD_VER >= 23
39template <move_constructible _Tp>
40# else
41template <copy_constructible _Tp>
42# endif
43 requires is_object_v<_Tp>
44class _LIBCPP_ABI_LLVM18_NO_UNIQUE_ADDRESS single_view : public view_interface<single_view<_Tp>> {
45 _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Tp> __value_;
46
47public:
48 _LIBCPP_HIDE_FROM_ABI single_view()
49 requires default_initializable<_Tp>
50 = default;
51
52 _LIBCPP_HIDE_FROM_ABI constexpr explicit single_view(const _Tp& __t)
53# if _LIBCPP_STD_VER >= 23
54 requires copy_constructible<_Tp>
55# endif
56 : __value_(in_place, __t) {
57 }
58
59 _LIBCPP_HIDE_FROM_ABI constexpr explicit single_view(_Tp&& __t) : __value_(in_place, std::move(__t)) {}
60
61 template <class... _Args>
62 requires constructible_from<_Tp, _Args...>
63 _LIBCPP_HIDE_FROM_ABI constexpr explicit single_view(in_place_t, _Args&&... __args)
64 : __value_{in_place, std::forward<_Args>(__args)...} {}
65
66 _LIBCPP_HIDE_FROM_ABI constexpr _Tp* begin() noexcept { return data(); }
67
68 _LIBCPP_HIDE_FROM_ABI constexpr const _Tp* begin() const noexcept { return data(); }
69
70 _LIBCPP_HIDE_FROM_ABI constexpr _Tp* end() noexcept { return data() + 1; }
71
72 _LIBCPP_HIDE_FROM_ABI constexpr const _Tp* end() const noexcept { return data() + 1; }
73
74 _LIBCPP_HIDE_FROM_ABI static constexpr bool empty() noexcept { return false; }
75
76 _LIBCPP_HIDE_FROM_ABI static constexpr size_t size() noexcept { return 1; }
77
78 _LIBCPP_HIDE_FROM_ABI constexpr _Tp* data() noexcept { return __value_.operator->(); }
79
80 _LIBCPP_HIDE_FROM_ABI constexpr const _Tp* data() const noexcept { return __value_.operator->(); }
81};
82
83template <class _Tp>
84single_view(_Tp) -> single_view<_Tp>;
85
86namespace views {
87namespace __single_view {
88
89struct __fn : __range_adaptor_closure<__fn> {
90 template <class _Range>
91 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const
92 noexcept(noexcept(single_view<decay_t<_Range&&>>(std::forward<_Range>(__range))))
93 -> decltype(single_view<decay_t<_Range&&>>(std::forward<_Range>(__range))) {
94 return single_view<decay_t<_Range&&>>(std::forward<_Range>(__range));
95 }
96};
97} // namespace __single_view
98
99inline namespace __cpo {
100inline constexpr auto single = __single_view::__fn{};
101} // namespace __cpo
102
103} // namespace views
104} // namespace ranges
105
106#endif // _LIBCPP_STD_VER >= 20
107
108_LIBCPP_END_NAMESPACE_STD
109
110_LIBCPP_POP_MACROS
111
112#endif // _LIBCPP___RANGES_SINGLE_VIEW_H
113