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_CHUNK_BY_VIEW_H
11#define _LIBCPP___RANGES_CHUNK_BY_VIEW_H
12
13#include <__algorithm/ranges_adjacent_find.h>
14#include <__assert>
15#include <__concepts/constructible.h>
16#include <__config>
17#include <__functional/bind_back.h>
18#include <__functional/invoke.h>
19#include <__iterator/concepts.h>
20#include <__iterator/default_sentinel.h>
21#include <__iterator/iterator_traits.h>
22#include <__iterator/next.h>
23#include <__iterator/prev.h>
24#include <__memory/addressof.h>
25#include <__ranges/access.h>
26#include <__ranges/all.h>
27#include <__ranges/concepts.h>
28#include <__ranges/movable_box.h>
29#include <__ranges/non_propagating_cache.h>
30#include <__ranges/range_adaptor.h>
31#include <__ranges/reverse_view.h>
32#include <__ranges/subrange.h>
33#include <__ranges/view_interface.h>
34#include <__type_traits/conditional.h>
35#include <__type_traits/decay.h>
36#include <__type_traits/is_nothrow_constructible.h>
37#include <__type_traits/is_object.h>
38#include <__utility/forward.h>
39#include <__utility/in_place.h>
40#include <__utility/move.h>
41
42#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
43# pragma GCC system_header
44#endif
45
46_LIBCPP_PUSH_MACROS
47#include <__undef_macros>
48
49_LIBCPP_BEGIN_NAMESPACE_STD
50
51#if _LIBCPP_STD_VER >= 23
52
53namespace ranges {
54
55template <forward_range _View, indirect_binary_predicate<iterator_t<_View>, iterator_t<_View>> _Pred>
56 requires view<_View> && is_object_v<_Pred>
57class _LIBCPP_ABI_LLVM18_NO_UNIQUE_ADDRESS chunk_by_view : public view_interface<chunk_by_view<_View, _Pred>> {
58 _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
59 _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Pred> __pred_;
60
61 // We cache the result of begin() to allow providing an amortized O(1).
62 using _Cache _LIBCPP_NODEBUG = __non_propagating_cache<iterator_t<_View>>;
63 _Cache __cached_begin_;
64
65 class __iterator;
66
67 _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_View> __find_next(iterator_t<_View> __current) {
68 // Note: this duplicates a check in `optional` but provides a better error message.
69 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
70 __pred_.__has_value(), "Trying to call __find_next() on a chunk_by_view that does not have a valid predicate.");
71 auto __reversed_pred = [this]<class _Tp, class _Up>(_Tp&& __x, _Up&& __y) -> bool {
72 return !std::invoke(*__pred_, std::forward<_Tp>(__x), std::forward<_Up>(__y));
73 };
74 return ranges::next(
75 ranges::adjacent_find(__current, ranges::end(__base_), __reversed_pred), 1, ranges::end(__base_));
76 }
77
78 _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_View> __find_prev(iterator_t<_View> __current)
79 requires bidirectional_range<_View>
80 {
81 // Attempting to decrement a begin iterator is a no-op (`__find_prev` would return the same argument given to it).
82 _LIBCPP_ASSERT_PEDANTIC(__current != ranges::begin(__base_), "Trying to call __find_prev() on a begin iterator.");
83 // Note: this duplicates a check in `optional` but provides a better error message.
84 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
85 __pred_.__has_value(), "Trying to call __find_prev() on a chunk_by_view that does not have a valid predicate.");
86
87 auto __first = ranges::begin(__base_);
88 reverse_view __reversed{subrange{__first, __current}};
89 auto __reversed_pred = [this]<class _Tp, class _Up>(_Tp&& __x, _Up&& __y) -> bool {
90 return !std::invoke(*__pred_, std::forward<_Up>(__y), std::forward<_Tp>(__x));
91 };
92 return ranges::prev(ranges::adjacent_find(__reversed, __reversed_pred).base(), 1, std::move(__first));
93 }
94
95public:
96 _LIBCPP_HIDE_FROM_ABI chunk_by_view()
97 requires default_initializable<_View> && default_initializable<_Pred>
98 = default;
99
100 _LIBCPP_HIDE_FROM_ABI constexpr explicit chunk_by_view(_View __base, _Pred __pred)
101 : __base_(std::move(__base)), __pred_(in_place, std::move(__pred)) {}
102
103 _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
104 requires copy_constructible<_View>
105 {
106 return __base_;
107 }
108
109 _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
110
111 _LIBCPP_HIDE_FROM_ABI constexpr const _Pred& pred() const { return *__pred_; }
112
113 _LIBCPP_HIDE_FROM_ABI constexpr __iterator begin() {
114 // Note: this duplicates a check in `optional` but provides a better error message.
115 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
116 __pred_.__has_value(), "Trying to call begin() on a chunk_by_view that does not have a valid predicate.");
117
118 auto __first = ranges::begin(__base_);
119 if (!__cached_begin_.__has_value()) {
120 __cached_begin_.__emplace(__find_next(current: __first));
121 }
122 return {*this, std::move(__first), *__cached_begin_};
123 }
124
125 _LIBCPP_HIDE_FROM_ABI constexpr auto end() {
126 if constexpr (common_range<_View>) {
127 return __iterator{*this, ranges::end(__base_), ranges::end(__base_)};
128 } else {
129 return default_sentinel;
130 }
131 }
132};
133
134template <class _Range, class _Pred>
135chunk_by_view(_Range&&, _Pred) -> chunk_by_view<views::all_t<_Range>, _Pred>;
136
137template <forward_range _View, indirect_binary_predicate<iterator_t<_View>, iterator_t<_View>> _Pred>
138 requires view<_View> && is_object_v<_Pred>
139class chunk_by_view<_View, _Pred>::__iterator {
140 friend chunk_by_view;
141
142 chunk_by_view* __parent_ = nullptr;
143 _LIBCPP_NO_UNIQUE_ADDRESS iterator_t<_View> __current_ = iterator_t<_View>();
144 _LIBCPP_NO_UNIQUE_ADDRESS iterator_t<_View> __next_ = iterator_t<_View>();
145
146 _LIBCPP_HIDE_FROM_ABI constexpr __iterator(
147 chunk_by_view& __parent, iterator_t<_View> __current, iterator_t<_View> __next)
148 : __parent_(std::addressof(__parent)), __current_(__current), __next_(__next) {}
149
150public:
151 using value_type = subrange<iterator_t<_View>>;
152 using difference_type = range_difference_t<_View>;
153 using iterator_category = input_iterator_tag;
154 using iterator_concept = conditional_t<bidirectional_range<_View>, bidirectional_iterator_tag, forward_iterator_tag>;
155
156 _LIBCPP_HIDE_FROM_ABI __iterator() = default;
157
158 _LIBCPP_HIDE_FROM_ABI constexpr value_type operator*() const {
159 // If the iterator is at end, this would return an empty range which can be checked by the calling code and doesn't
160 // necessarily lead to a bad access.
161 _LIBCPP_ASSERT_PEDANTIC(__current_ != __next_, "Trying to dereference past-the-end chunk_by_view iterator.");
162 return {__current_, __next_};
163 }
164
165 _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator++() {
166 // Attempting to increment an end iterator is a no-op (`__find_next` would return the same argument given to it).
167 _LIBCPP_ASSERT_PEDANTIC(__current_ != __next_, "Trying to increment past end chunk_by_view iterator.");
168 __current_ = __next_;
169 __next_ = __parent_->__find_next(__current_);
170 return *this;
171 }
172
173 _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator++(int) {
174 auto __tmp = *this;
175 ++*this;
176 return __tmp;
177 }
178
179 _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator--()
180 requires bidirectional_range<_View>
181 {
182 __next_ = __current_;
183 __current_ = __parent_->__find_prev(__next_);
184 return *this;
185 }
186
187 _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator--(int)
188 requires bidirectional_range<_View>
189 {
190 auto __tmp = *this;
191 --*this;
192 return __tmp;
193 }
194
195 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator& __x, const __iterator& __y) {
196 return __x.__current_ == __y.__current_;
197 }
198
199 _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator& __x, default_sentinel_t) {
200 return __x.__current_ == __x.__next_;
201 }
202};
203
204namespace views {
205namespace __chunk_by {
206struct __fn {
207 template <class _Range, class _Pred>
208 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Pred&& __pred) const
209 noexcept(noexcept(/**/ chunk_by_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))))
210 -> decltype(/*--*/ chunk_by_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))) {
211 return /*-------------*/ chunk_by_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred));
212 }
213
214 template <class _Pred>
215 requires constructible_from<decay_t<_Pred>, _Pred>
216 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Pred&& __pred) const
217 noexcept(is_nothrow_constructible_v<decay_t<_Pred>, _Pred>) {
218 return __pipeable(std::__bind_back(*this, std::forward<_Pred>(__pred)));
219 }
220};
221} // namespace __chunk_by
222
223inline namespace __cpo {
224inline constexpr auto chunk_by = __chunk_by::__fn{};
225} // namespace __cpo
226} // namespace views
227} // namespace ranges
228
229#endif // _LIBCPP_STD_VER >= 23
230
231_LIBCPP_END_NAMESPACE_STD
232
233_LIBCPP_POP_MACROS
234
235#endif // _LIBCPP___RANGES_CHUNK_BY_VIEW_H
236