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_FILTER_VIEW_H
11 #define _LIBCPP___RANGES_FILTER_VIEW_H
12 
13 #include <__algorithm/ranges_find_if.h>
14 #include <__concepts/constructible.h>
15 #include <__concepts/copyable.h>
16 #include <__concepts/derived_from.h>
17 #include <__concepts/equality_comparable.h>
18 #include <__config>
19 #include <__debug>
20 #include <__functional/bind_back.h>
21 #include <__functional/invoke.h>
22 #include <__functional/reference_wrapper.h>
23 #include <__iterator/concepts.h>
24 #include <__iterator/iter_move.h>
25 #include <__iterator/iter_swap.h>
26 #include <__iterator/iterator_traits.h>
27 #include <__memory/addressof.h>
28 #include <__ranges/access.h>
29 #include <__ranges/all.h>
30 #include <__ranges/concepts.h>
31 #include <__ranges/copyable_box.h>
32 #include <__ranges/non_propagating_cache.h>
33 #include <__ranges/range_adaptor.h>
34 #include <__ranges/view_interface.h>
35 #include <__utility/forward.h>
36 #include <__utility/in_place.h>
37 #include <__utility/move.h>
38 #include <type_traits>
39 
40 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
41 #  pragma GCC system_header
42 #endif
43 
44 _LIBCPP_BEGIN_NAMESPACE_STD
45 
46 #if _LIBCPP_STD_VER > 17
47 
48 namespace ranges {
49   template<input_range _View, indirect_unary_predicate<iterator_t<_View>> _Pred>
50     requires view<_View> && is_object_v<_Pred>
51   class filter_view : public view_interface<filter_view<_View, _Pred>> {
52     _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
53     _LIBCPP_NO_UNIQUE_ADDRESS __copyable_box<_Pred> __pred_;
54 
55     // We cache the result of begin() to allow providing an amortized O(1) begin() whenever
56     // the underlying range is at least a forward_range.
57     static constexpr bool _UseCache = forward_range<_View>;
58     using _Cache = _If<_UseCache, __non_propagating_cache<iterator_t<_View>>, __empty_cache>;
59     _LIBCPP_NO_UNIQUE_ADDRESS _Cache __cached_begin_ = _Cache();
60 
61     class __iterator;
62     class __sentinel;
63 
64   public:
65     _LIBCPP_HIDE_FROM_ABI
66     filter_view() requires default_initializable<_View> && default_initializable<_Pred> = default;
67 
68     _LIBCPP_HIDE_FROM_ABI
filter_view(_View __base,_Pred __pred)69     constexpr filter_view(_View __base, _Pred __pred)
70       : __base_(std::move(__base)), __pred_(in_place, std::move(__pred))
71     { }
72 
73     template<class _Vp = _View>
74     _LIBCPP_HIDE_FROM_ABI
base()75     constexpr _View base() const& requires copy_constructible<_Vp> { return __base_; }
76     _LIBCPP_HIDE_FROM_ABI
base()77     constexpr _View base() && { return std::move(__base_); }
78 
79     _LIBCPP_HIDE_FROM_ABI
pred()80     constexpr _Pred const& pred() const { return *__pred_; }
81 
82     _LIBCPP_HIDE_FROM_ABI
begin()83     constexpr __iterator begin() {
84       _LIBCPP_ASSERT(__pred_.__has_value(), "Trying to call begin() on a filter_view that does not have a valid predicate.");
85       if constexpr (_UseCache) {
86         if (!__cached_begin_.__has_value()) {
87           __cached_begin_.__emplace(ranges::find_if(__base_, std::ref(*__pred_)));
88         }
89         return {*this, *__cached_begin_};
90       } else {
91         return {*this, ranges::find_if(__base_, std::ref(*__pred_))};
92       }
93     }
94 
95     _LIBCPP_HIDE_FROM_ABI
end()96     constexpr auto end() {
97       if constexpr (common_range<_View>)
98         return __iterator{*this, ranges::end(__base_)};
99       else
100         return __sentinel{*this};
101     }
102   };
103 
104   template<class _Range, class _Pred>
105   filter_view(_Range&&, _Pred) -> filter_view<views::all_t<_Range>, _Pred>;
106 
107   template<class _View>
108   struct __filter_iterator_category { };
109 
110   template<forward_range _View>
111   struct __filter_iterator_category<_View> {
112     using _Cat = typename iterator_traits<iterator_t<_View>>::iterator_category;
113     using iterator_category =
114       _If<derived_from<_Cat, bidirectional_iterator_tag>, bidirectional_iterator_tag,
115       _If<derived_from<_Cat, forward_iterator_tag>,       forward_iterator_tag,
116       /* else */                                          _Cat
117     >>;
118   };
119 
120   template<input_range _View, indirect_unary_predicate<iterator_t<_View>> _Pred>
121     requires view<_View> && is_object_v<_Pred>
122   class filter_view<_View, _Pred>::__iterator : public __filter_iterator_category<_View> {
123 
124   public:
125     _LIBCPP_NO_UNIQUE_ADDRESS iterator_t<_View> __current_ = iterator_t<_View>();
126     _LIBCPP_NO_UNIQUE_ADDRESS filter_view* __parent_ = nullptr;
127 
128     using iterator_concept =
129       _If<bidirectional_range<_View>, bidirectional_iterator_tag,
130       _If<forward_range<_View>,       forward_iterator_tag,
131       /* else */                      input_iterator_tag
132     >>;
133     // using iterator_category = inherited;
134     using value_type = range_value_t<_View>;
135     using difference_type = range_difference_t<_View>;
136 
137     _LIBCPP_HIDE_FROM_ABI
138     __iterator() requires default_initializable<iterator_t<_View>> = default;
139 
140     _LIBCPP_HIDE_FROM_ABI
141     constexpr __iterator(filter_view& __parent, iterator_t<_View> __current)
142       : __current_(std::move(__current)), __parent_(std::addressof(__parent))
143     { }
144 
145     _LIBCPP_HIDE_FROM_ABI
146     constexpr iterator_t<_View> const& base() const& noexcept { return __current_; }
147     _LIBCPP_HIDE_FROM_ABI
148     constexpr iterator_t<_View> base() && { return std::move(__current_); }
149 
150     _LIBCPP_HIDE_FROM_ABI
151     constexpr range_reference_t<_View> operator*() const { return *__current_; }
152     _LIBCPP_HIDE_FROM_ABI
153     constexpr iterator_t<_View> operator->() const
154       requires __has_arrow<iterator_t<_View>> && copyable<iterator_t<_View>>
155     {
156       return __current_;
157     }
158 
159     _LIBCPP_HIDE_FROM_ABI
160     constexpr __iterator& operator++() {
161       __current_ = ranges::find_if(std::move(++__current_), ranges::end(__parent_->__base_),
162                                    std::ref(*__parent_->__pred_));
163       return *this;
164     }
165     _LIBCPP_HIDE_FROM_ABI
166     constexpr void operator++(int) { ++*this; }
167     _LIBCPP_HIDE_FROM_ABI
168     constexpr __iterator operator++(int) requires forward_range<_View> {
169       auto __tmp = *this;
170       ++*this;
171       return __tmp;
172     }
173 
174     _LIBCPP_HIDE_FROM_ABI
175     constexpr __iterator& operator--() requires bidirectional_range<_View> {
176       do {
177         --__current_;
178       } while (!std::invoke(*__parent_->__pred_, *__current_));
179       return *this;
180     }
181     _LIBCPP_HIDE_FROM_ABI
182     constexpr __iterator operator--(int) requires bidirectional_range<_View> {
183       auto tmp = *this;
184       --*this;
185       return tmp;
186     }
187 
188     _LIBCPP_HIDE_FROM_ABI
189     friend constexpr bool operator==(__iterator const& __x, __iterator const& __y)
190       requires equality_comparable<iterator_t<_View>>
191     {
192       return __x.__current_ == __y.__current_;
193     }
194 
195     _LIBCPP_HIDE_FROM_ABI
196     friend constexpr range_rvalue_reference_t<_View> iter_move(__iterator const& __it)
197       noexcept(noexcept(ranges::iter_move(__it.__current_)))
198     {
199       return ranges::iter_move(__it.__current_);
200     }
201 
202     _LIBCPP_HIDE_FROM_ABI
203     friend constexpr void iter_swap(__iterator const& __x, __iterator const& __y)
204       noexcept(noexcept(ranges::iter_swap(__x.__current_, __y.__current_)))
205       requires indirectly_swappable<iterator_t<_View>>
206     {
207       return ranges::iter_swap(__x.__current_, __y.__current_);
208     }
209   };
210 
211   template<input_range _View, indirect_unary_predicate<iterator_t<_View>> _Pred>
212     requires view<_View> && is_object_v<_Pred>
213   class filter_view<_View, _Pred>::__sentinel {
214   public:
215     sentinel_t<_View> __end_ = sentinel_t<_View>();
216 
217     _LIBCPP_HIDE_FROM_ABI
218     __sentinel() = default;
219 
220     _LIBCPP_HIDE_FROM_ABI
221     constexpr explicit __sentinel(filter_view& __parent)
222       : __end_(ranges::end(__parent.__base_))
223     { }
224 
225     _LIBCPP_HIDE_FROM_ABI
226     constexpr sentinel_t<_View> base() const { return __end_; }
227 
228     _LIBCPP_HIDE_FROM_ABI friend constexpr bool
229     operator==(__iterator const& __x, __sentinel const& __y) {
230       return __x.__current_ == __y.__end_;
231     }
232   };
233 
234 namespace views {
235 namespace __filter {
236   struct __fn {
237     template<class _Range, class _Pred>
238     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
239     constexpr auto operator()(_Range&& __range, _Pred&& __pred) const
240       noexcept(noexcept(filter_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))))
241       -> decltype(      filter_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred)))
242       { return          filter_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred)); }
243 
244     template<class _Pred>
245       requires constructible_from<decay_t<_Pred>, _Pred>
246     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
247     constexpr auto operator()(_Pred&& __pred) const
248       noexcept(is_nothrow_constructible_v<decay_t<_Pred>, _Pred>)
249     { return __range_adaptor_closure_t(std::__bind_back(*this, std::forward<_Pred>(__pred))); }
250   };
251 } // namespace __filter
252 
253 inline namespace __cpo {
254   inline constexpr auto filter = __filter::__fn{};
255 } // namespace __cpo
256 } // namespace views
257 
258 } // namespace ranges
259 
260 #endif // _LIBCPP_STD_VER > 17
261 
262 _LIBCPP_END_NAMESPACE_STD
263 
264 #endif // _LIBCPP___RANGES_FILTER_VIEW_H
265