libcxx/include/__ranges/chunk_by_view.h

   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
  53 namespace ranges {
  54
  55 template <forward_range _View, indirect_binary_predicate<iterator_t<_View>, iterator_t<_View>> _Pred>
  56   requires view<_View> && is_object_v<_Pred>
  57 class _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 = __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
  95 public:
  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(__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
 134 template <class _Range, class _Pred>
 135 chunk_by_view(_Range&&, _Pred) -> chunk_by_view<views::all_t<_Range>, _Pred>;
 136
 137 template <forward_range _View, indirect_binary_predicate<iterator_t<_View>, iterator_t<_View>> _Pred>
 138   requires view<_View> && is_object_v<_Pred>
 139 class 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
 150 public:
 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
 204 namespace views {
 205 namespace __chunk_by {
 206 struct __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
 223 inline namespace __cpo {
 224 inline 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