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_JOIN_VIEW_H
11#define _LIBCPP___RANGES_JOIN_VIEW_H
12
13#include <__concepts/constructible.h>
14#include <__concepts/convertible_to.h>
15#include <__concepts/copyable.h>
16#include <__concepts/derived_from.h>
17#include <__concepts/equality_comparable.h>
18#include <__config>
19#include <__iterator/concepts.h>
20#include <__iterator/iter_move.h>
21#include <__iterator/iter_swap.h>
22#include <__iterator/iterator_traits.h>
23#include <__iterator/iterator_with_data.h>
24#include <__iterator/segmented_iterator.h>
25#include <__ranges/access.h>
26#include <__ranges/all.h>
27#include <__ranges/concepts.h>
28#include <__ranges/empty.h>
29#include <__ranges/non_propagating_cache.h>
30#include <__ranges/range_adaptor.h>
31#include <__ranges/view_interface.h>
32#include <__type_traits/maybe_const.h>
33#include <__utility/forward.h>
34#include <optional>
35#include <type_traits>
36
37#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
38#  pragma GCC system_header
39#endif
40
41_LIBCPP_BEGIN_NAMESPACE_STD
42
43// Note: `join_view` is still marked experimental because there is an ABI-breaking change that affects `join_view` in
44// the pipeline (https://isocpp.org/files/papers/D2770R0.html).
45// TODO: make `join_view` non-experimental once D2770 is implemented.
46#if _LIBCPP_STD_VER > 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
47
48namespace ranges {
49  template<class>
50  struct __join_view_iterator_category {};
51
52  template<class _View>
53    requires is_reference_v<range_reference_t<_View>> &&
54             forward_range<_View> &&
55             forward_range<range_reference_t<_View>>
56  struct __join_view_iterator_category<_View> {
57    using _OuterC = typename iterator_traits<iterator_t<_View>>::iterator_category;
58    using _InnerC = typename iterator_traits<iterator_t<range_reference_t<_View>>>::iterator_category;
59
60    using iterator_category = _If<
61      derived_from<_OuterC, bidirectional_iterator_tag> && derived_from<_InnerC, bidirectional_iterator_tag> &&
62        common_range<range_reference_t<_View>>,
63      bidirectional_iterator_tag,
64      _If<
65        derived_from<_OuterC, forward_iterator_tag> && derived_from<_InnerC, forward_iterator_tag>,
66        forward_iterator_tag,
67        input_iterator_tag
68      >
69    >;
70  };
71
72  template<input_range _View>
73    requires view<_View> && input_range<range_reference_t<_View>>
74  class join_view
75    : public view_interface<join_view<_View>> {
76  private:
77    using _InnerRange = range_reference_t<_View>;
78
79    template<bool> struct __iterator;
80
81    template<bool> struct __sentinel;
82
83    template <class>
84    friend struct std::__segmented_iterator_traits;
85
86    static constexpr bool _UseCache = !is_reference_v<_InnerRange>;
87    using _Cache = _If<_UseCache, __non_propagating_cache<remove_cvref_t<_InnerRange>>, __empty_cache>;
88    _LIBCPP_NO_UNIQUE_ADDRESS _Cache __cache_;
89    _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
90
91  public:
92    _LIBCPP_HIDE_FROM_ABI
93    join_view() requires default_initializable<_View> = default;
94
95    _LIBCPP_HIDE_FROM_ABI
96    constexpr explicit join_view(_View __base)
97      : __base_(std::move(__base)) {}
98
99    _LIBCPP_HIDE_FROM_ABI
100    constexpr _View base() const& requires copy_constructible<_View> { return __base_; }
101
102    _LIBCPP_HIDE_FROM_ABI
103    constexpr _View base() && { return std::move(__base_); }
104
105    _LIBCPP_HIDE_FROM_ABI
106    constexpr auto begin() {
107      constexpr bool __use_const = __simple_view<_View> &&
108                                   is_reference_v<range_reference_t<_View>>;
109      return __iterator<__use_const>{*this, ranges::begin(__base_)};
110    }
111
112    template<class _V2 = _View>
113    _LIBCPP_HIDE_FROM_ABI
114    constexpr auto begin() const
115      requires input_range<const _V2> &&
116               is_reference_v<range_reference_t<const _V2>>
117    {
118      return __iterator<true>{*this, ranges::begin(__base_)};
119    }
120
121    _LIBCPP_HIDE_FROM_ABI
122    constexpr auto end() {
123      if constexpr (forward_range<_View> &&
124                    is_reference_v<_InnerRange> &&
125                    forward_range<_InnerRange> &&
126                    common_range<_View> &&
127                    common_range<_InnerRange>)
128        return __iterator<__simple_view<_View>>{*this, ranges::end(__base_)};
129      else
130        return __sentinel<__simple_view<_View>>{*this};
131    }
132
133    template<class _V2 = _View>
134    _LIBCPP_HIDE_FROM_ABI
135    constexpr auto end() const
136      requires input_range<const _V2> &&
137               is_reference_v<range_reference_t<const _V2>>
138    {
139      using _ConstInnerRange = range_reference_t<const _View>;
140      if constexpr (forward_range<const _View> &&
141                    is_reference_v<_ConstInnerRange> &&
142                    forward_range<_ConstInnerRange> &&
143                    common_range<const _View> &&
144                    common_range<_ConstInnerRange>) {
145        return __iterator<true>{*this, ranges::end(__base_)};
146      } else {
147        return __sentinel<true>{*this};
148      }
149    }
150  };
151
152  template<input_range _View>
153    requires view<_View> && input_range<range_reference_t<_View>>
154  template<bool _Const>
155  struct join_view<_View>::__sentinel {
156  template<bool>
157    friend struct __sentinel;
158
159  private:
160    using _Parent = __maybe_const<_Const, join_view<_View>>;
161    using _Base = __maybe_const<_Const, _View>;
162    sentinel_t<_Base> __end_ = sentinel_t<_Base>();
163
164  public:
165    _LIBCPP_HIDE_FROM_ABI
166    __sentinel() = default;
167
168    _LIBCPP_HIDE_FROM_ABI
169    constexpr explicit __sentinel(_Parent& __parent)
170      : __end_(ranges::end(__parent.__base_)) {}
171
172    _LIBCPP_HIDE_FROM_ABI
173    constexpr __sentinel(__sentinel<!_Const> __s)
174      requires _Const && convertible_to<sentinel_t<_View>, sentinel_t<_Base>>
175      : __end_(std::move(__s.__end_)) {}
176
177    template<bool _OtherConst>
178      requires sentinel_for<sentinel_t<_Base>, iterator_t<__maybe_const<_OtherConst, _View>>>
179    _LIBCPP_HIDE_FROM_ABI
180    friend constexpr bool operator==(const __iterator<_OtherConst>& __x, const __sentinel& __y) {
181      return __x.__outer_ == __y.__end_;
182    }
183  };
184
185  // https://reviews.llvm.org/D142811#inline-1383022
186  // To simplify the segmented iterator traits specialization,
187  // make the iterator `final`
188  template<input_range _View>
189    requires view<_View> && input_range<range_reference_t<_View>>
190  template<bool _Const>
191  struct join_view<_View>::__iterator final
192    : public __join_view_iterator_category<__maybe_const<_Const, _View>> {
193
194    template<bool>
195    friend struct __iterator;
196
197    template <class>
198    friend struct std::__segmented_iterator_traits;
199
200    static constexpr bool __is_join_view_iterator = true;
201
202  private:
203    using _Parent = __maybe_const<_Const, join_view<_View>>;
204    using _Base = __maybe_const<_Const, _View>;
205    using _Outer = iterator_t<_Base>;
206    using _Inner = iterator_t<range_reference_t<_Base>>;
207    using _InnerRange = range_reference_t<_View>;
208
209    static constexpr bool __ref_is_glvalue = is_reference_v<range_reference_t<_Base>>;
210
211  public:
212    _Outer __outer_ = _Outer();
213
214  private:
215    optional<_Inner> __inner_;
216    _Parent *__parent_ = nullptr;
217
218    _LIBCPP_HIDE_FROM_ABI
219    constexpr void __satisfy() {
220      for (; __outer_ != ranges::end(__parent_->__base_); ++__outer_) {
221        auto&& __inner = [&]() -> auto&& {
222          if constexpr (__ref_is_glvalue)
223            return *__outer_;
224          else
225            return __parent_->__cache_.__emplace_from([&]() -> decltype(auto) { return *__outer_; });
226        }();
227        __inner_ = ranges::begin(__inner);
228        if (*__inner_ != ranges::end(__inner))
229          return;
230      }
231
232      if constexpr (__ref_is_glvalue)
233        __inner_.reset();
234    }
235
236    _LIBCPP_HIDE_FROM_ABI constexpr __iterator(_Parent* __parent, _Outer __outer, _Inner __inner)
237      : __outer_(std::move(__outer)), __inner_(std::move(__inner)), __parent_(__parent) {}
238
239  public:
240    using iterator_concept = _If<
241      __ref_is_glvalue && bidirectional_range<_Base> && bidirectional_range<range_reference_t<_Base>> &&
242          common_range<range_reference_t<_Base>>,
243      bidirectional_iterator_tag,
244      _If<
245        __ref_is_glvalue && forward_range<_Base> && forward_range<range_reference_t<_Base>>,
246        forward_iterator_tag,
247        input_iterator_tag
248      >
249    >;
250
251    using value_type = range_value_t<range_reference_t<_Base>>;
252
253    using difference_type = common_type_t<
254      range_difference_t<_Base>, range_difference_t<range_reference_t<_Base>>>;
255
256    _LIBCPP_HIDE_FROM_ABI
257    __iterator() requires default_initializable<_Outer> = default;
258
259    _LIBCPP_HIDE_FROM_ABI
260    constexpr __iterator(_Parent& __parent, _Outer __outer)
261      : __outer_(std::move(__outer))
262      , __parent_(std::addressof(__parent)) {
263      __satisfy();
264    }
265
266    _LIBCPP_HIDE_FROM_ABI
267    constexpr __iterator(__iterator<!_Const> __i)
268      requires _Const &&
269               convertible_to<iterator_t<_View>, _Outer> &&
270               convertible_to<iterator_t<_InnerRange>, _Inner>
271      : __outer_(std::move(__i.__outer_))
272      , __inner_(std::move(__i.__inner_))
273      , __parent_(__i.__parent_) {}
274
275    _LIBCPP_HIDE_FROM_ABI
276    constexpr decltype(auto) operator*() const {
277      return **__inner_;
278    }
279
280    _LIBCPP_HIDE_FROM_ABI
281    constexpr _Inner operator->() const
282      requires __has_arrow<_Inner> && copyable<_Inner>
283    {
284      return *__inner_;
285    }
286
287    _LIBCPP_HIDE_FROM_ABI
288    constexpr __iterator& operator++() {
289      auto&& __inner = [&]() -> auto&& {
290        if constexpr (__ref_is_glvalue)
291          return *__outer_;
292        else
293          return *__parent_->__cache_;
294      }();
295      if (++*__inner_ == ranges::end(__inner)) {
296        ++__outer_;
297        __satisfy();
298      }
299      return *this;
300    }
301
302    _LIBCPP_HIDE_FROM_ABI
303    constexpr void operator++(int) {
304      ++*this;
305    }
306
307    _LIBCPP_HIDE_FROM_ABI
308    constexpr __iterator operator++(int)
309      requires __ref_is_glvalue &&
310               forward_range<_Base> &&
311               forward_range<range_reference_t<_Base>>
312    {
313      auto __tmp = *this;
314      ++*this;
315      return __tmp;
316    }
317
318    _LIBCPP_HIDE_FROM_ABI
319    constexpr __iterator& operator--()
320      requires __ref_is_glvalue &&
321               bidirectional_range<_Base> &&
322               bidirectional_range<range_reference_t<_Base>> &&
323               common_range<range_reference_t<_Base>>
324    {
325      if (__outer_ == ranges::end(__parent_->__base_))
326        __inner_ = ranges::end(*--__outer_);
327
328      // Skip empty inner ranges when going backwards.
329      while (*__inner_ == ranges::begin(*__outer_)) {
330        __inner_ = ranges::end(*--__outer_);
331      }
332
333      --*__inner_;
334      return *this;
335    }
336
337    _LIBCPP_HIDE_FROM_ABI
338    constexpr __iterator operator--(int)
339      requires __ref_is_glvalue &&
340               bidirectional_range<_Base> &&
341               bidirectional_range<range_reference_t<_Base>> &&
342               common_range<range_reference_t<_Base>>
343    {
344      auto __tmp = *this;
345      --*this;
346      return __tmp;
347    }
348
349    _LIBCPP_HIDE_FROM_ABI
350    friend constexpr bool operator==(const __iterator& __x, const __iterator& __y)
351      requires __ref_is_glvalue &&
352               equality_comparable<iterator_t<_Base>> &&
353               equality_comparable<iterator_t<range_reference_t<_Base>>>
354    {
355      return __x.__outer_ == __y.__outer_ && __x.__inner_ == __y.__inner_;
356    }
357
358    _LIBCPP_HIDE_FROM_ABI
359    friend constexpr decltype(auto) iter_move(const __iterator& __i)
360      noexcept(noexcept(ranges::iter_move(*__i.__inner_)))
361    {
362      return ranges::iter_move(*__i.__inner_);
363    }
364
365    _LIBCPP_HIDE_FROM_ABI
366    friend constexpr void iter_swap(const __iterator& __x, const __iterator& __y)
367      noexcept(noexcept(ranges::iter_swap(*__x.__inner_, *__y.__inner_)))
368      requires indirectly_swappable<_Inner>
369    {
370      return ranges::iter_swap(*__x.__inner_, *__y.__inner_);
371    }
372  };
373
374  template<class _Range>
375  explicit join_view(_Range&&) -> join_view<views::all_t<_Range>>;
376
377namespace views {
378namespace __join_view {
379struct __fn : __range_adaptor_closure<__fn> {
380  template<class _Range>
381  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI
382  constexpr auto operator()(_Range&& __range) const
383    noexcept(noexcept(join_view<all_t<_Range&&>>(std::forward<_Range>(__range))))
384    -> decltype(      join_view<all_t<_Range&&>>(std::forward<_Range>(__range)))
385    { return          join_view<all_t<_Range&&>>(std::forward<_Range>(__range)); }
386};
387} // namespace __join_view
388inline namespace __cpo {
389  inline constexpr auto join = __join_view::__fn{};
390} // namespace __cpo
391} // namespace views
392} // namespace ranges
393
394template <class _JoinViewIterator>
395  requires(_JoinViewIterator::__is_join_view_iterator &&
396           ranges::common_range<typename _JoinViewIterator::_Parent> &&
397           __is_cpp17_random_access_iterator<typename _JoinViewIterator::_Outer>::value &&
398           __is_cpp17_random_access_iterator<typename _JoinViewIterator::_Inner>::value)
399struct __segmented_iterator_traits<_JoinViewIterator> {
400
401  using __segment_iterator =
402      _LIBCPP_NODEBUG __iterator_with_data<typename _JoinViewIterator::_Outer, typename _JoinViewIterator::_Parent*>;
403  using __local_iterator = typename _JoinViewIterator::_Inner;
404
405  // TODO: Would it make sense to enable the optimization for other iterator types?
406
407  static constexpr _LIBCPP_HIDE_FROM_ABI __segment_iterator __segment(_JoinViewIterator __iter) {
408      if (ranges::empty(__iter.__parent_->__base_))
409        return {};
410      if (!__iter.__inner_.has_value())
411        return __segment_iterator(--__iter.__outer_, __iter.__parent_);
412      return __segment_iterator(__iter.__outer_, __iter.__parent_);
413  }
414
415  static constexpr _LIBCPP_HIDE_FROM_ABI __local_iterator __local(_JoinViewIterator __iter) {
416      if (ranges::empty(__iter.__parent_->__base_))
417        return {};
418      if (!__iter.__inner_.has_value())
419        return ranges::end(*--__iter.__outer_);
420      return *__iter.__inner_;
421  }
422
423  static constexpr _LIBCPP_HIDE_FROM_ABI __local_iterator __begin(__segment_iterator __iter) {
424      return ranges::begin(*__iter.__get_iter());
425  }
426
427  static constexpr _LIBCPP_HIDE_FROM_ABI __local_iterator __end(__segment_iterator __iter) {
428      return ranges::end(*__iter.__get_iter());
429  }
430
431  static constexpr _LIBCPP_HIDE_FROM_ABI _JoinViewIterator
432  __compose(__segment_iterator __seg_iter, __local_iterator __local_iter) {
433      return _JoinViewIterator(
434          std::move(__seg_iter).__get_data(), std::move(__seg_iter).__get_iter(), std::move(__local_iter));
435  }
436};
437
438#endif // #if _LIBCPP_STD_VER > 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
439
440_LIBCPP_END_NAMESPACE_STD
441
442#endif // _LIBCPP___RANGES_JOIN_VIEW_H
443