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_REVERSE_VIEW_H
11#define _LIBCPP___RANGES_REVERSE_VIEW_H
12
13#include <__concepts/constructible.h>
14#include <__config>
15#include <__iterator/concepts.h>
16#include <__iterator/next.h>
17#include <__iterator/reverse_iterator.h>
18#include <__ranges/access.h>
19#include <__ranges/all.h>
20#include <__ranges/concepts.h>
21#include <__ranges/enable_borrowed_range.h>
22#include <__ranges/non_propagating_cache.h>
23#include <__ranges/range_adaptor.h>
24#include <__ranges/size.h>
25#include <__ranges/subrange.h>
26#include <__ranges/view_interface.h>
27#include <__type_traits/conditional.h>
28#include <__type_traits/remove_cvref.h>
29#include <__utility/forward.h>
30#include <__utility/move.h>
31
32#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
33# pragma GCC system_header
34#endif
35
36_LIBCPP_PUSH_MACROS
37#include <__undef_macros>
38
39_LIBCPP_BEGIN_NAMESPACE_STD
40
41#if _LIBCPP_STD_VER >= 20
42
43namespace ranges {
44template <view _View>
45 requires bidirectional_range<_View>
46class reverse_view : public view_interface<reverse_view<_View>> {
47 // We cache begin() whenever ranges::next is not guaranteed O(1) to provide an
48 // amortized O(1) begin() method.
49 static constexpr bool _UseCache = !random_access_range<_View> && !common_range<_View>;
50 using _Cache = _If<_UseCache, __non_propagating_cache<reverse_iterator<iterator_t<_View>>>, __empty_cache>;
51 _LIBCPP_NO_UNIQUE_ADDRESS _Cache __cached_begin_ = _Cache();
52 _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
53
54public:
55 _LIBCPP_HIDE_FROM_ABI reverse_view()
56 requires default_initializable<_View>
57 = default;
58
59 _LIBCPP_HIDE_FROM_ABI constexpr explicit reverse_view(_View __view) : __base_(std::move(__view)) {}
60
61 _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
62 requires copy_constructible<_View>
63 {
64 return __base_;
65 }
66
67 _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
68
69 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator<iterator_t<_View>> begin() {
70 if constexpr (_UseCache)
71 if (__cached_begin_.__has_value())
72 return *__cached_begin_;
73
74 auto __tmp = std::make_reverse_iterator(ranges::next(ranges::begin(__base_), ranges::end(__base_)));
75 if constexpr (_UseCache)
76 __cached_begin_.__emplace(__tmp);
77 return __tmp;
78 }
79
80 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator<iterator_t<_View>> begin()
81 requires common_range<_View>
82 {
83 return std::make_reverse_iterator(ranges::end(__base_));
84 }
85
86 _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
87 requires common_range<const _View>
88 {
89 return std::make_reverse_iterator(ranges::end(__base_));
90 }
91
92 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator<iterator_t<_View>> end() {
93 return std::make_reverse_iterator(ranges::begin(__base_));
94 }
95
96 _LIBCPP_HIDE_FROM_ABI constexpr auto end() const
97 requires common_range<const _View>
98 {
99 return std::make_reverse_iterator(ranges::begin(__base_));
100 }
101
102 _LIBCPP_HIDE_FROM_ABI constexpr auto size()
103 requires sized_range<_View>
104 {
105 return ranges::size(__base_);
106 }
107
108 _LIBCPP_HIDE_FROM_ABI constexpr auto size() const
109 requires sized_range<const _View>
110 {
111 return ranges::size(__base_);
112 }
113};
114
115template <class _Range>
116reverse_view(_Range&&) -> reverse_view<views::all_t<_Range>>;
117
118template <class _Tp>
119inline constexpr bool enable_borrowed_range<reverse_view<_Tp>> = enable_borrowed_range<_Tp>;
120
121namespace views {
122namespace __reverse {
123template <class _Tp>
124inline constexpr bool __is_reverse_view = false;
125
126template <class _Tp>
127inline constexpr bool __is_reverse_view<reverse_view<_Tp>> = true;
128
129template <class _Tp>
130inline constexpr bool __is_sized_reverse_subrange = false;
131
132template <class _Iter>
133inline constexpr bool
134 __is_sized_reverse_subrange<subrange<reverse_iterator<_Iter>, reverse_iterator<_Iter>, subrange_kind::sized>> =
135 true;
136
137template <class _Tp>
138inline constexpr bool __is_unsized_reverse_subrange = false;
139
140template <class _Iter, subrange_kind _Kind>
141inline constexpr bool __is_unsized_reverse_subrange<subrange<reverse_iterator<_Iter>, reverse_iterator<_Iter>, _Kind>> =
142 _Kind == subrange_kind::unsized;
143
144template <class _Tp>
145struct __unwrapped_reverse_subrange {
146 using type =
147 void; // avoid SFINAE-ing out the overload below -- let the concept requirements do it for better diagnostics
148};
149
150template <class _Iter, subrange_kind _Kind>
151struct __unwrapped_reverse_subrange<subrange<reverse_iterator<_Iter>, reverse_iterator<_Iter>, _Kind>> {
152 using type = subrange<_Iter, _Iter, _Kind>;
153};
154
155struct __fn : __range_adaptor_closure<__fn> {
156 template <class _Range>
157 requires __is_reverse_view<remove_cvref_t<_Range>>
158 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const
159 noexcept(noexcept(std::forward<_Range>(__range).base())) -> decltype(std::forward<_Range>(__range).base()) {
160 return std::forward<_Range>(__range).base();
161 }
162
163 template <class _Range,
164 class _UnwrappedSubrange = typename __unwrapped_reverse_subrange<remove_cvref_t<_Range>>::type>
165 requires __is_sized_reverse_subrange<remove_cvref_t<_Range>>
166 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const
167 noexcept(noexcept(_UnwrappedSubrange(__range.end().base(), __range.begin().base(), __range.size())))
168 -> decltype(_UnwrappedSubrange(__range.end().base(), __range.begin().base(), __range.size())) {
169 return _UnwrappedSubrange(__range.end().base(), __range.begin().base(), __range.size());
170 }
171
172 template <class _Range,
173 class _UnwrappedSubrange = typename __unwrapped_reverse_subrange<remove_cvref_t<_Range>>::type>
174 requires __is_unsized_reverse_subrange<remove_cvref_t<_Range>>
175 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const
176 noexcept(noexcept(_UnwrappedSubrange(__range.end().base(), __range.begin().base())))
177 -> decltype(_UnwrappedSubrange(__range.end().base(), __range.begin().base())) {
178 return _UnwrappedSubrange(__range.end().base(), __range.begin().base());
179 }
180
181 template <class _Range>
182 requires(!__is_reverse_view<remove_cvref_t<_Range>> && !__is_sized_reverse_subrange<remove_cvref_t<_Range>> &&
183 !__is_unsized_reverse_subrange<remove_cvref_t<_Range>>)
184 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range) const noexcept(noexcept(reverse_view{
185 std::forward<_Range>(__range)})) -> decltype(reverse_view{std::forward<_Range>(__range)}) {
186 return reverse_view{std::forward<_Range>(__range)};
187 }
188};
189} // namespace __reverse
190
191inline namespace __cpo {
192inline constexpr auto reverse = __reverse::__fn{};
193} // namespace __cpo
194} // namespace views
195} // namespace ranges
196
197#endif // _LIBCPP_STD_VER >= 20
198
199_LIBCPP_END_NAMESPACE_STD
200
201_LIBCPP_POP_MACROS
202
203#endif // _LIBCPP___RANGES_REVERSE_VIEW_H
204