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 #ifndef _LIBCPP___RANGES_JOIN_VIEW_H
10 #define _LIBCPP___RANGES_JOIN_VIEW_H
11 
12 #include <__concepts/constructible.h>
13 #include <__concepts/convertible_to.h>
14 #include <__concepts/copyable.h>
15 #include <__concepts/derived_from.h>
16 #include <__concepts/equality_comparable.h>
17 #include <__config>
18 #include <__iterator/concepts.h>
19 #include <__iterator/iter_move.h>
20 #include <__iterator/iter_swap.h>
21 #include <__iterator/iterator_traits.h>
22 #include <__ranges/access.h>
23 #include <__ranges/all.h>
24 #include <__ranges/concepts.h>
25 #include <__ranges/non_propagating_cache.h>
26 #include <__ranges/range_adaptor.h>
27 #include <__ranges/view_interface.h>
28 #include <__utility/forward.h>
29 #include <optional>
30 #include <type_traits>
31 
32 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
33 #  pragma GCC system_header
34 #endif
35 
36 _LIBCPP_BEGIN_NAMESPACE_STD
37 
38 #if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
39 
40 namespace ranges {
41   template<class>
42   struct __join_view_iterator_category {};
43 
44   template<class _View>
45     requires is_reference_v<range_reference_t<_View>> &&
46              forward_range<_View> &&
47              forward_range<range_reference_t<_View>>
48   struct __join_view_iterator_category<_View> {
49     using _OuterC = typename iterator_traits<iterator_t<_View>>::iterator_category;
50     using _InnerC = typename iterator_traits<iterator_t<range_reference_t<_View>>>::iterator_category;
51 
52     using iterator_category = _If<
53       derived_from<_OuterC, bidirectional_iterator_tag> && derived_from<_InnerC, bidirectional_iterator_tag> &&
54         common_range<range_reference_t<_View>>,
55       bidirectional_iterator_tag,
56       _If<
57         derived_from<_OuterC, forward_iterator_tag> && derived_from<_InnerC, forward_iterator_tag>,
58         forward_iterator_tag,
59         input_iterator_tag
60       >
61     >;
62   };
63 
64   template<input_range _View>
65     requires view<_View> && input_range<range_reference_t<_View>>
66   class join_view
67     : public view_interface<join_view<_View>> {
68   private:
69     using _InnerRange = range_reference_t<_View>;
70 
71     template<bool> struct __iterator;
72     template<bool> struct __sentinel;
73 
74     static constexpr bool _UseCache = !is_reference_v<_InnerRange>;
75     using _Cache = _If<_UseCache, __non_propagating_cache<remove_cvref_t<_InnerRange>>, __empty_cache>;
76     _LIBCPP_NO_UNIQUE_ADDRESS _Cache __cache_;
77     _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
78 
79   public:
80     _LIBCPP_HIDE_FROM_ABI
81     join_view() requires default_initializable<_View> = default;
82 
83     _LIBCPP_HIDE_FROM_ABI
84     constexpr explicit join_view(_View __base)
85       : __base_(std::move(__base)) {}
86 
87     _LIBCPP_HIDE_FROM_ABI
88     constexpr _View base() const& requires copy_constructible<_View> { return __base_; }
89 
90     _LIBCPP_HIDE_FROM_ABI
91     constexpr _View base() && { return std::move(__base_); }
92 
93     _LIBCPP_HIDE_FROM_ABI
94     constexpr auto begin() {
95       constexpr bool __use_const = __simple_view<_View> &&
96                                    is_reference_v<range_reference_t<_View>>;
97       return __iterator<__use_const>{*this, ranges::begin(__base_)};
98     }
99 
100     template<class _V2 = _View>
101     _LIBCPP_HIDE_FROM_ABI
102     constexpr auto begin() const
103       requires input_range<const _V2> &&
104                is_reference_v<range_reference_t<const _V2>>
105     {
106       return __iterator<true>{*this, ranges::begin(__base_)};
107     }
108 
109     _LIBCPP_HIDE_FROM_ABI
110     constexpr auto end() {
111       if constexpr (forward_range<_View> &&
112                     is_reference_v<_InnerRange> &&
113                     forward_range<_InnerRange> &&
114                     common_range<_View> &&
115                     common_range<_InnerRange>)
116         return __iterator<__simple_view<_View>>{*this, ranges::end(__base_)};
117       else
118         return __sentinel<__simple_view<_View>>{*this};
119     }
120 
121     template<class _V2 = _View>
122     _LIBCPP_HIDE_FROM_ABI
123     constexpr auto end() const
124       requires input_range<const _V2> &&
125                is_reference_v<range_reference_t<const _V2>>
126     {
127       using _ConstInnerRange = range_reference_t<const _View>;
128       if constexpr (forward_range<const _View> &&
129                     is_reference_v<_ConstInnerRange> &&
130                     forward_range<_ConstInnerRange> &&
131                     common_range<const _View> &&
132                     common_range<_ConstInnerRange>) {
133         return __iterator<true>{*this, ranges::end(__base_)};
134       } else {
135         return __sentinel<true>{*this};
136       }
137     }
138   };
139 
140   template<input_range _View>
141     requires view<_View> && input_range<range_reference_t<_View>>
142   template<bool _Const> struct join_view<_View>::__sentinel {
143     template<bool> friend struct __sentinel;
144 
145   private:
146     using _Parent = __maybe_const<_Const, join_view>;
147     using _Base = __maybe_const<_Const, _View>;
148     sentinel_t<_Base> __end_ = sentinel_t<_Base>();
149 
150   public:
151     _LIBCPP_HIDE_FROM_ABI
152     __sentinel() = default;
153 
154     _LIBCPP_HIDE_FROM_ABI
155     constexpr explicit __sentinel(_Parent& __parent)
156       : __end_(ranges::end(__parent.__base_)) {}
157 
158     _LIBCPP_HIDE_FROM_ABI
159     constexpr __sentinel(__sentinel<!_Const> __s)
160       requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
161       : __end_(std::move(__s.__end_)) {}
162 
163     template<bool _OtherConst>
164       requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
165     _LIBCPP_HIDE_FROM_ABI
166     friend constexpr bool operator==(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
167       return __x.__outer_ == __y.__end_;
168     }
169   };
170 
171   template<input_range _View>
172     requires view<_View> && input_range<range_reference_t<_View>>
173   template<bool _Const> struct join_view<_View>::__iterator
174     : public __join_view_iterator_category<__maybe_const<_Const, _View>> {
175 
176     template<bool> friend struct __iterator;
177 
178   private:
179     using _Parent = __maybe_const<_Const, join_view>;
180     using _Base = __maybe_const<_Const, _View>;
181     using _Outer = iterator_t<_Base>;
182     using _Inner = iterator_t<range_reference_t<_Base>>;
183 
184     static constexpr bool __ref_is_glvalue = is_reference_v<range_reference_t<_Base>>;
185 
186   public:
187     _Outer __outer_ = _Outer();
188 
189   private:
190     optional<_Inner> __inner_;
191     _Parent *__parent_ = nullptr;
192 
193     _LIBCPP_HIDE_FROM_ABI
194     constexpr void __satisfy() {
195       for (; __outer_ != ranges::end(__parent_->__base_); ++__outer_) {
196         auto&& __inner = [&]() -> auto&& {
197           if constexpr (__ref_is_glvalue)
198             return *__outer_;
199           else
200             return __parent_->__cache_.__emplace_from([&]() -> decltype(auto) { return *__outer_; });
201         }();
202         __inner_ = ranges::begin(__inner);
203         if (*__inner_ != ranges::end(__inner))
204           return;
205       }
206 
207       if constexpr (__ref_is_glvalue)
208         __inner_.reset();
209     }
210 
211   public:
212     using iterator_concept = _If<
213       __ref_is_glvalue && bidirectional_range<_Base> && bidirectional_range<range_reference_t<_Base>> &&
214           common_range<range_reference_t<_Base>>,
215       bidirectional_iterator_tag,
216       _If<
217         __ref_is_glvalue && forward_range<_Base> && forward_range<range_reference_t<_Base>>,
218         forward_iterator_tag,
219         input_iterator_tag
220       >
221     >;
222 
223     using value_type = range_value_t<range_reference_t<_Base>>;
224 
225     using difference_type = common_type_t<
226       range_difference_t<_Base>, range_difference_t<range_reference_t<_Base>>>;
227 
228     _LIBCPP_HIDE_FROM_ABI
229     __iterator() requires default_initializable<_Outer> = default;
230 
231     _LIBCPP_HIDE_FROM_ABI
232     constexpr __iterator(_Parent& __parent, _Outer __outer)
233       : __outer_(std::move(__outer))
234       , __parent_(std::addressof(__parent)) {
235       __satisfy();
236     }
237 
238     _LIBCPP_HIDE_FROM_ABI
239     constexpr __iterator(__iterator<!_Const> __i)
240       requires _Const &&
241                convertible_to<iterator_t<_View>, _Outer> &&
242                convertible_to<iterator_t<_InnerRange>, _Inner>
243       : __outer_(std::move(__i.__outer_))
244       , __inner_(std::move(__i.__inner_))
245       , __parent_(__i.__parent_) {}
246 
247     _LIBCPP_HIDE_FROM_ABI
248     constexpr decltype(auto) operator*() const {
249       return **__inner_;
250     }
251 
252     _LIBCPP_HIDE_FROM_ABI
253     constexpr _Inner operator->() const
254       requires __has_arrow<_Inner> && copyable<_Inner>
255     {
256       return *__inner_;
257     }
258 
259     _LIBCPP_HIDE_FROM_ABI
260     constexpr __iterator& operator++() {
261       auto&& __inner = [&]() -> auto&& {
262         if constexpr (__ref_is_glvalue)
263           return *__outer_;
264         else
265           return *__parent_->__cache_;
266       }();
267       if (++*__inner_ == ranges::end(__inner)) {
268         ++__outer_;
269         __satisfy();
270       }
271       return *this;
272     }
273 
274     _LIBCPP_HIDE_FROM_ABI
275     constexpr void operator++(int) {
276       ++*this;
277     }
278 
279     _LIBCPP_HIDE_FROM_ABI
280     constexpr __iterator operator++(int)
281       requires __ref_is_glvalue &&
282                forward_range<_Base> &&
283                forward_range<range_reference_t<_Base>>
284     {
285       auto __tmp = *this;
286       ++*this;
287       return __tmp;
288     }
289 
290     _LIBCPP_HIDE_FROM_ABI
291     constexpr __iterator& operator--()
292       requires __ref_is_glvalue &&
293                bidirectional_range<_Base> &&
294                bidirectional_range<range_reference_t<_Base>> &&
295                common_range<range_reference_t<_Base>>
296     {
297       if (__outer_ == ranges::end(__parent_->__base_))
298         __inner_ = ranges::end(*--__outer_);
299 
300       // Skip empty inner ranges when going backwards.
301       while (*__inner_ == ranges::begin(*__outer_)) {
302         __inner_ = ranges::end(*--__outer_);
303       }
304 
305       --*__inner_;
306       return *this;
307     }
308 
309     _LIBCPP_HIDE_FROM_ABI
310     constexpr __iterator operator--(int)
311       requires __ref_is_glvalue &&
312                bidirectional_range<_Base> &&
313                bidirectional_range<range_reference_t<_Base>> &&
314                common_range<range_reference_t<_Base>>
315     {
316       auto __tmp = *this;
317       --*this;
318       return __tmp;
319     }
320 
321     _LIBCPP_HIDE_FROM_ABI
322     friend constexpr bool operator==(const __iterator& __x, const __iterator& __y)
323       requires __ref_is_glvalue &&
324                equality_comparable<iterator_t<_Base>> &&
325                equality_comparable<iterator_t<range_reference_t<_Base>>>
326     {
327       return __x.__outer_ == __y.__outer_ && __x.__inner_ == __y.__inner_;
328     }
329 
330     _LIBCPP_HIDE_FROM_ABI
331     friend constexpr decltype(auto) iter_move(const __iterator& __i)
332       noexcept(noexcept(ranges::iter_move(*__i.__inner_)))
333     {
334       return ranges::iter_move(*__i.__inner_);
335     }
336 
337     _LIBCPP_HIDE_FROM_ABI
338     friend constexpr void iter_swap(const __iterator& __x, const __iterator& __y)
339       noexcept(noexcept(ranges::iter_swap(*__x.__inner_, *__y.__inner_)))
340       requires indirectly_swappable<_Inner>
341     {
342       return ranges::iter_swap(*__x.__inner_, *__y.__inner_);
343     }
344   };
345 
346   template<class _Range>
347   explicit join_view(_Range&&) -> join_view<views::all_t<_Range>>;
348 
349 namespace views {
350 namespace __join_view {
351 struct __fn : __range_adaptor_closure<__fn> {
352   template<class _Range>
353   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
354   constexpr auto operator()(_Range&& __range) const
355     noexcept(noexcept(join_view<all_t<_Range&&>>(std::forward<_Range>(__range))))
356     -> decltype(      join_view<all_t<_Range&&>>(std::forward<_Range>(__range)))
357     { return          join_view<all_t<_Range&&>>(std::forward<_Range>(__range)); }
358 };
359 } // namespace __join_view
360 inline namespace __cpo {
361   inline constexpr auto join = __join_view::__fn{};
362 } // namespace __cpo
363 } // namespace views
364 } // namespace ranges
365 
366 #endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
367 
368 _LIBCPP_END_NAMESPACE_STD
369 
370 #endif // _LIBCPP___RANGES_JOIN_VIEW_H
371