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_LAZY_SPLIT_VIEW_H
11 #define _LIBCPP___RANGES_LAZY_SPLIT_VIEW_H
12 
13 #include <__algorithm/ranges_find.h>
14 #include <__algorithm/ranges_mismatch.h>
15 #include <__assert>
16 #include <__concepts/constructible.h>
17 #include <__concepts/convertible_to.h>
18 #include <__concepts/derived_from.h>
19 #include <__config>
20 #include <__functional/bind_back.h>
21 #include <__functional/ranges_operations.h>
22 #include <__iterator/concepts.h>
23 #include <__iterator/default_sentinel.h>
24 #include <__iterator/incrementable_traits.h>
25 #include <__iterator/indirectly_comparable.h>
26 #include <__iterator/iter_move.h>
27 #include <__iterator/iter_swap.h>
28 #include <__iterator/iterator_traits.h>
29 #include <__memory/addressof.h>
30 #include <__ranges/access.h>
31 #include <__ranges/all.h>
32 #include <__ranges/concepts.h>
33 #include <__ranges/non_propagating_cache.h>
34 #include <__ranges/range_adaptor.h>
35 #include <__ranges/single_view.h>
36 #include <__ranges/subrange.h>
37 #include <__ranges/view_interface.h>
38 #include <__type_traits/conditional.h>
39 #include <__type_traits/decay.h>
40 #include <__type_traits/is_nothrow_constructible.h>
41 #include <__type_traits/maybe_const.h>
42 #include <__type_traits/remove_reference.h>
43 #include <__utility/forward.h>
44 #include <__utility/move.h>
45 
46 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
47 #  pragma GCC system_header
48 #endif
49 
50 _LIBCPP_PUSH_MACROS
51 #include <__undef_macros>
52 
53 _LIBCPP_BEGIN_NAMESPACE_STD
54 
55 #if _LIBCPP_STD_VER >= 20
56 
57 namespace ranges {
58 
59 template <auto>
60 struct __require_constant;
61 
62 template <class _Range>
63 concept __tiny_range = sized_range<_Range> && requires {
64   typename __require_constant<remove_reference_t<_Range>::size()>;
65 } && (remove_reference_t<_Range>::size() <= 1);
66 
67 template <input_range _View, forward_range _Pattern>
68   requires view<_View> && view<_Pattern> &&
69            indirectly_comparable<iterator_t<_View>, iterator_t<_Pattern>, ranges::equal_to> &&
70            (forward_range<_View> || __tiny_range<_Pattern>)
71 class lazy_split_view : public view_interface<lazy_split_view<_View, _Pattern>> {
72   _LIBCPP_NO_UNIQUE_ADDRESS _View __base_       = _View();
73   _LIBCPP_NO_UNIQUE_ADDRESS _Pattern __pattern_ = _Pattern();
74 
75   using _MaybeCurrent = _If<!forward_range<_View>, __non_propagating_cache<iterator_t<_View>>, __empty_cache>;
76   _LIBCPP_NO_UNIQUE_ADDRESS _MaybeCurrent __current_ = _MaybeCurrent();
77 
78   template <bool>
79   struct __outer_iterator;
80   template <bool>
81   struct __inner_iterator;
82 
83 public:
84   _LIBCPP_HIDE_FROM_ABI lazy_split_view()
85     requires default_initializable<_View> && default_initializable<_Pattern>
86   = default;
87 
88   _LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23 lazy_split_view(_View __base, _Pattern __pattern)
89       : __base_(std::move(__base)), __pattern_(std::move(__pattern)) {}
90 
91   template <input_range _Range>
92     requires constructible_from<_View, views::all_t<_Range>> &&
93                  constructible_from<_Pattern, single_view<range_value_t<_Range>>>
94   _LIBCPP_HIDE_FROM_ABI constexpr _LIBCPP_EXPLICIT_SINCE_CXX23 lazy_split_view(_Range&& __r, range_value_t<_Range> __e)
95       : __base_(views::all(std::forward<_Range>(__r))), __pattern_(views::single(std::move(__e))) {}
96 
97   _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
98     requires copy_constructible<_View>
99   {
100     return __base_;
101   }
102   _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
103 
104   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() {
105     if constexpr (forward_range<_View>) {
106       return __outer_iterator < __simple_view<_View> && __simple_view < _Pattern >> {*this, ranges::begin(__base_)};
107     } else {
108       __current_.__emplace(ranges::begin(__base_));
109       return __outer_iterator<false>{*this};
110     }
111   }
112 
113   _LIBCPP_HIDE_FROM_ABI constexpr auto begin() const
114     requires forward_range<_View> && forward_range<const _View>
115   {
116     return __outer_iterator<true>{*this, ranges::begin(__base_)};
117   }
118 
119   _LIBCPP_HIDE_FROM_ABI constexpr auto end()
120     requires forward_range<_View> && common_range<_View>
121   {
122     return __outer_iterator < __simple_view<_View> && __simple_view < _Pattern >> {*this, ranges::end(__base_)};
123   }
124 
125   _LIBCPP_HIDE_FROM_ABI constexpr auto end() const {
126     if constexpr (forward_range<_View> && forward_range<const _View> && common_range<const _View>) {
127       return __outer_iterator<true>{*this, ranges::end(__base_)};
128     } else {
129       return default_sentinel;
130     }
131   }
132 
133 private:
134   template <class>
135   struct __outer_iterator_category {};
136 
137   template <forward_range _Tp>
138   struct __outer_iterator_category<_Tp> {
139     using iterator_category = input_iterator_tag;
140   };
141 
142   template <bool _Const>
143   struct __outer_iterator : __outer_iterator_category<__maybe_const<_Const, _View>> {
144   private:
145     template <bool>
146     friend struct __inner_iterator;
147     friend __outer_iterator<true>;
148 
149     using _Parent = __maybe_const<_Const, lazy_split_view>;
150     using _Base   = __maybe_const<_Const, _View>;
151 
152     _Parent* __parent_                                 = nullptr;
153     using _MaybeCurrent                                = _If<forward_range<_View>, iterator_t<_Base>, __empty_cache>;
154     _LIBCPP_NO_UNIQUE_ADDRESS _MaybeCurrent __current_ = _MaybeCurrent();
155     bool __trailing_empty_                             = false;
156 
157     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto& __current() noexcept {
158       if constexpr (forward_range<_View>) {
159         return __current_;
160       } else {
161         return *__parent_->__current_;
162       }
163     }
164 
165     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr const auto& __current() const noexcept {
166       if constexpr (forward_range<_View>) {
167         return __current_;
168       } else {
169         return *__parent_->__current_;
170       }
171     }
172 
173     // Workaround for the GCC issue that doesn't allow calling `__parent_->__base_` from friend functions (because
174     // `__base_` is private).
175     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto& __parent_base() const noexcept { return __parent_->__base_; }
176 
177   public:
178     // using iterator_category = inherited;
179     using iterator_concept = conditional_t<forward_range<_Base>, forward_iterator_tag, input_iterator_tag>;
180     using difference_type  = range_difference_t<_Base>;
181 
182     struct value_type : view_interface<value_type> {
183     private:
184       __outer_iterator __i_ = __outer_iterator();
185 
186     public:
187       _LIBCPP_HIDE_FROM_ABI value_type() = default;
188       _LIBCPP_HIDE_FROM_ABI constexpr explicit value_type(__outer_iterator __i) : __i_(std::move(__i)) {}
189 
190       _LIBCPP_HIDE_FROM_ABI constexpr __inner_iterator<_Const> begin() const { return __inner_iterator<_Const>{__i_}; }
191       _LIBCPP_HIDE_FROM_ABI constexpr default_sentinel_t end() const noexcept { return default_sentinel; }
192     };
193 
194     _LIBCPP_HIDE_FROM_ABI __outer_iterator() = default;
195 
196     _LIBCPP_HIDE_FROM_ABI constexpr explicit __outer_iterator(_Parent& __parent)
197       requires(!forward_range<_Base>)
198         : __parent_(std::addressof(__parent)) {}
199 
200     _LIBCPP_HIDE_FROM_ABI constexpr __outer_iterator(_Parent& __parent, iterator_t<_Base> __current)
201       requires forward_range<_Base>
202         : __parent_(std::addressof(__parent)), __current_(std::move(__current)) {}
203 
204     _LIBCPP_HIDE_FROM_ABI constexpr __outer_iterator(__outer_iterator<!_Const> __i)
205       requires _Const && convertible_to<iterator_t<_View>, iterator_t<_Base>>
206         : __parent_(__i.__parent_), __current_(std::move(__i.__current_)) {}
207 
208     _LIBCPP_HIDE_FROM_ABI constexpr value_type operator*() const { return value_type{*this}; }
209 
210     _LIBCPP_HIDE_FROM_ABI constexpr __outer_iterator& operator++() {
211       const auto __end = ranges::end(__parent_->__base_);
212       if (__current() == __end) {
213         __trailing_empty_ = false;
214         return *this;
215       }
216 
217       const auto [__pbegin, __pend] = ranges::subrange{__parent_->__pattern_};
218       if (__pbegin == __pend) {
219         // Empty pattern: split on every element in the input range
220         ++__current();
221 
222       } else if constexpr (__tiny_range<_Pattern>) {
223         // One-element pattern: we can use `ranges::find`.
224         __current() = ranges::find(std::move(__current()), __end, *__pbegin);
225         if (__current() != __end) {
226           // Make sure we point to after the separator we just found.
227           ++__current();
228           if (__current() == __end)
229             __trailing_empty_ = true;
230         }
231 
232       } else {
233         // General case for n-element pattern.
234         do {
235           const auto [__b, __p] = ranges::mismatch(__current(), __end, __pbegin, __pend);
236           if (__p == __pend) {
237             __current() = __b;
238             if (__current() == __end) {
239               __trailing_empty_ = true;
240             }
241             break; // The pattern matched; skip it.
242           }
243         } while (++__current() != __end);
244       }
245 
246       return *this;
247     }
248 
249     _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator++(int) {
250       if constexpr (forward_range<_Base>) {
251         auto __tmp = *this;
252         ++*this;
253         return __tmp;
254 
255       } else {
256         ++*this;
257       }
258     }
259 
260     _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __outer_iterator& __x, const __outer_iterator& __y)
261       requires forward_range<_Base>
262     {
263       return __x.__current_ == __y.__current_ && __x.__trailing_empty_ == __y.__trailing_empty_;
264     }
265 
266     _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __outer_iterator& __x, default_sentinel_t) {
267       _LIBCPP_ASSERT_NON_NULL(__x.__parent_ != nullptr, "Cannot call comparison on a default-constructed iterator.");
268       return __x.__current() == ranges::end(__x.__parent_base()) && !__x.__trailing_empty_;
269     }
270   };
271 
272   template <class>
273   struct __inner_iterator_category {};
274 
275   template <forward_range _Tp>
276   struct __inner_iterator_category<_Tp> {
277     using iterator_category =
278         _If< derived_from<typename iterator_traits<iterator_t<_Tp>>::iterator_category, forward_iterator_tag>,
279              forward_iterator_tag,
280              typename iterator_traits<iterator_t<_Tp>>::iterator_category >;
281   };
282 
283   template <bool _Const>
284   struct __inner_iterator : __inner_iterator_category<__maybe_const<_Const, _View>> {
285   private:
286     using _Base = __maybe_const<_Const, _View>;
287     // Workaround for a GCC issue.
288     static constexpr bool _OuterConst = _Const;
289     __outer_iterator<_Const> __i_     = __outer_iterator<_OuterConst>();
290     bool __incremented_               = false;
291 
292     // Note: these private functions are necessary because GCC doesn't allow calls to private members of `__i_` from
293     // free functions that are friends of `inner-iterator`.
294 
295     _LIBCPP_HIDE_FROM_ABI constexpr bool __is_done() const {
296       _LIBCPP_ASSERT_NON_NULL(__i_.__parent_ != nullptr, "Cannot call comparison on a default-constructed iterator.");
297 
298       auto [__pcur, __pend] = ranges::subrange{__i_.__parent_->__pattern_};
299       auto __end            = ranges::end(__i_.__parent_->__base_);
300 
301       if constexpr (__tiny_range<_Pattern>) {
302         const auto& __cur = __i_.__current();
303         if (__cur == __end)
304           return true;
305         if (__pcur == __pend)
306           return __incremented_;
307 
308         return *__cur == *__pcur;
309 
310       } else {
311         auto __cur = __i_.__current();
312         if (__cur == __end)
313           return true;
314         if (__pcur == __pend)
315           return __incremented_;
316 
317         do {
318           if (*__cur != *__pcur)
319             return false;
320           if (++__pcur == __pend)
321             return true;
322         } while (++__cur != __end);
323 
324         return false;
325       }
326     }
327 
328     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto& __outer_current() noexcept { return __i_.__current(); }
329 
330     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr const auto& __outer_current() const noexcept {
331       return __i_.__current();
332     }
333 
334   public:
335     // using iterator_category = inherited;
336     using iterator_concept = typename __outer_iterator<_Const>::iterator_concept;
337     using value_type       = range_value_t<_Base>;
338     using difference_type  = range_difference_t<_Base>;
339 
340     _LIBCPP_HIDE_FROM_ABI __inner_iterator() = default;
341 
342     _LIBCPP_HIDE_FROM_ABI constexpr explicit __inner_iterator(__outer_iterator<_Const> __i) : __i_(std::move(__i)) {}
343 
344     _LIBCPP_HIDE_FROM_ABI constexpr const iterator_t<_Base>& base() const& noexcept { return __i_.__current(); }
345     _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_Base> base() &&
346       requires forward_range<_View>
347     {
348       return std::move(__i_.__current());
349     }
350 
351     _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator*() const { return *__i_.__current(); }
352 
353     _LIBCPP_HIDE_FROM_ABI constexpr __inner_iterator& operator++() {
354       __incremented_ = true;
355 
356       if constexpr (!forward_range<_Base>) {
357         if constexpr (_Pattern::size() == 0) {
358           return *this;
359         }
360       }
361 
362       ++__i_.__current();
363       return *this;
364     }
365 
366     _LIBCPP_HIDE_FROM_ABI constexpr decltype(auto) operator++(int) {
367       if constexpr (forward_range<_Base>) {
368         auto __tmp = *this;
369         ++*this;
370         return __tmp;
371 
372       } else {
373         ++*this;
374       }
375     }
376 
377     _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __inner_iterator& __x, const __inner_iterator& __y)
378       requires forward_range<_Base>
379     {
380       return __x.__outer_current() == __y.__outer_current();
381     }
382 
383     _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __inner_iterator& __x, default_sentinel_t) {
384       return __x.__is_done();
385     }
386 
387     _LIBCPP_HIDE_FROM_ABI friend constexpr decltype(auto)
388     iter_move(const __inner_iterator& __i) noexcept(noexcept(ranges::iter_move(__i.__outer_current()))) {
389       return ranges::iter_move(__i.__outer_current());
390     }
391 
392     _LIBCPP_HIDE_FROM_ABI friend constexpr void iter_swap(
393         const __inner_iterator& __x,
394         const __inner_iterator& __y) noexcept(noexcept(ranges::iter_swap(__x.__outer_current(), __y.__outer_current())))
395       requires indirectly_swappable<iterator_t<_Base>>
396     {
397       ranges::iter_swap(__x.__outer_current(), __y.__outer_current());
398     }
399   };
400 };
401 
402 template <class _Range, class _Pattern>
403 lazy_split_view(_Range&&, _Pattern&&) -> lazy_split_view<views::all_t<_Range>, views::all_t<_Pattern>>;
404 
405 template <input_range _Range>
406 lazy_split_view(_Range&&, range_value_t<_Range>)
407     -> lazy_split_view<views::all_t<_Range>, single_view<range_value_t<_Range>>>;
408 
409 namespace views {
410 namespace __lazy_split_view {
411 struct __fn {
412   template <class _Range, class _Pattern>
413   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Pattern&& __pattern) const
414       noexcept(noexcept(lazy_split_view(std::forward<_Range>(__range), std::forward<_Pattern>(__pattern))))
415           -> decltype(lazy_split_view(std::forward<_Range>(__range), std::forward<_Pattern>(__pattern))) {
416     return lazy_split_view(std::forward<_Range>(__range), std::forward<_Pattern>(__pattern));
417   }
418 
419   template <class _Pattern>
420     requires constructible_from<decay_t<_Pattern>, _Pattern>
421   [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Pattern&& __pattern) const
422       noexcept(is_nothrow_constructible_v<decay_t<_Pattern>, _Pattern>) {
423     return __range_adaptor_closure_t(std::__bind_back(*this, std::forward<_Pattern>(__pattern)));
424   }
425 };
426 } // namespace __lazy_split_view
427 
428 inline namespace __cpo {
429 inline constexpr auto lazy_split = __lazy_split_view::__fn{};
430 } // namespace __cpo
431 } // namespace views
432 
433 } // namespace ranges
434 
435 #endif // _LIBCPP_STD_VER >= 20
436 
437 _LIBCPP_END_NAMESPACE_STD
438 
439 _LIBCPP_POP_MACROS
440 
441 #endif // _LIBCPP___RANGES_LAZY_SPLIT_VIEW_H
442