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 <__functional/not_fn.h>
  20 #include <__functional/reference_wrapper.h>
  21 #include <__iterator/concepts.h>
  22 #include <__iterator/default_sentinel.h>
  23 #include <__iterator/iterator_traits.h>
  24 #include <__iterator/next.h>
  25 #include <__iterator/prev.h>
  26 #include <__memory/addressof.h>
  27 #include <__ranges/access.h>
  28 #include <__ranges/all.h>
  29 #include <__ranges/concepts.h>
  30 #include <__ranges/movable_box.h>
  31 #include <__ranges/non_propagating_cache.h>
  32 #include <__ranges/range_adaptor.h>
  33 #include <__ranges/reverse_view.h>
  34 #include <__ranges/subrange.h>
  35 #include <__ranges/view_interface.h>
  36 #include <__type_traits/conditional.h>
  37 #include <__type_traits/decay.h>
  38 #include <__type_traits/is_nothrow_constructible.h>
  39 #include <__type_traits/is_object.h>
  40 #include <__utility/forward.h>
  41 #include <__utility/in_place.h>
  42 #include <__utility/move.h>
  43
  44 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  45 #  pragma GCC system_header
  46 #endif
  47
  48 _LIBCPP_PUSH_MACROS
  49 #include <__undef_macros>
  50
  51 _LIBCPP_BEGIN_NAMESPACE_STD
  52
  53 #if _LIBCPP_STD_VER >= 23
  54
  55 namespace ranges {
  56
  57 template <forward_range _View, indirect_binary_predicate<iterator_t<_View>, iterator_t<_View>> _Pred>
  58   requires view<_View> && is_object_v<_Pred>
  59 class chunk_by_view : public view_interface<chunk_by_view<_View, _Pred>> {
  60   _LIBCPP_NO_UNIQUE_ADDRESS _View __base_ = _View();
  61   _LIBCPP_NO_UNIQUE_ADDRESS __movable_box<_Pred> __pred_;
  62
  63   // We cache the result of begin() to allow providing an amortized O(1).
  64   using _Cache = __non_propagating_cache<iterator_t<_View>>;
  65   _Cache __cached_begin_;
  66
  67   class __iterator;
  68
  69   _LIBCPP_HIDE_FROM_ABI constexpr iterator_t<_View> __find_next(iterator_t<_View> __current) {
  70     _LIBCPP_ASSERT_UNCATEGORIZED(
  71         __pred_.__has_value(), "Trying to call __find_next() on a chunk_by_view that does not have a valid predicate.");
  72
  73     return ranges::next(ranges::adjacent_find(__current, ranges::end(__base_), std::not_fn(std::ref(*__pred_))),
  74                         1,
  75                         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     _LIBCPP_ASSERT_UNCATEGORIZED(
  82         __current != ranges::begin(__base_), "Trying to call __find_prev() on a begin iterator.");
  83     _LIBCPP_ASSERT_UNCATEGORIZED(
  84         __pred_.__has_value(), "Trying to call __find_prev() on a chunk_by_view that does not have a valid predicate.");
  85
  86     auto __first = ranges::begin(__base_);
  87     reverse_view __reversed{subrange{__first, __current}};
  88     auto __reversed_pred = [this]<class _Tp, class _Up>(_Tp&& __x, _Up&& __y) {
  89       return !std::invoke(*__pred_, std::forward<_Up>(__y), std::forward<_Tp>(__x));
  90     };
  91     return ranges::prev(ranges::adjacent_find(__reversed, __reversed_pred).base(), 1, std::move(__first));
  92   }
  93
  94 public:
  95   _LIBCPP_HIDE_FROM_ABI chunk_by_view()
  96     requires default_initializable<_View> && default_initializable<_Pred>
  97   = default;
  98
  99   _LIBCPP_HIDE_FROM_ABI constexpr explicit chunk_by_view(_View __base, _Pred __pred)
 100       : __base_(std::move(__base)), __pred_(in_place, std::move(__pred)) {}
 101
 102   _LIBCPP_HIDE_FROM_ABI constexpr _View base() const&
 103     requires copy_constructible<_View>
 104   {
 105     return __base_;
 106   }
 107
 108   _LIBCPP_HIDE_FROM_ABI constexpr _View base() && { return std::move(__base_); }
 109
 110   _LIBCPP_HIDE_FROM_ABI constexpr const _Pred& pred() const { return *__pred_; }
 111
 112   _LIBCPP_HIDE_FROM_ABI constexpr __iterator begin() {
 113     _LIBCPP_ASSERT_UNCATEGORIZED(
 114         __pred_.__has_value(), "Trying to call begin() on a chunk_by_view that does not have a valid predicate.");
 115
 116     auto __first = ranges::begin(__base_);
 117     if (!__cached_begin_.__has_value()) {
 118       __cached_begin_.__emplace(__find_next(__first));
 119     }
 120     return {*this, std::move(__first), *__cached_begin_};
 121   }
 122
 123   _LIBCPP_HIDE_FROM_ABI constexpr auto end() {
 124     if constexpr (common_range<_View>) {
 125       return __iterator{*this, ranges::end(__base_), ranges::end(__base_)};
 126     } else {
 127       return default_sentinel;
 128     }
 129   }
 130 };
 131
 132 template <class _Range, class _Pred>
 133 chunk_by_view(_Range&&, _Pred) -> chunk_by_view<views::all_t<_Range>, _Pred>;
 134
 135 template <forward_range _View, indirect_binary_predicate<iterator_t<_View>, iterator_t<_View>> _Pred>
 136   requires view<_View> && is_object_v<_Pred>
 137 class chunk_by_view<_View, _Pred>::__iterator {
 138   friend chunk_by_view;
 139
 140   chunk_by_view* __parent_                               = nullptr;
 141   _LIBCPP_NO_UNIQUE_ADDRESS iterator_t<_View> __current_ = iterator_t<_View>();
 142   _LIBCPP_NO_UNIQUE_ADDRESS iterator_t<_View> __next_    = iterator_t<_View>();
 143
 144   _LIBCPP_HIDE_FROM_ABI constexpr __iterator(
 145       chunk_by_view& __parent, iterator_t<_View> __current, iterator_t<_View> __next)
 146       : __parent_(std::addressof(__parent)), __current_(__current), __next_(__next) {}
 147
 148 public:
 149   using value_type        = subrange<iterator_t<_View>>;
 150   using difference_type   = range_difference_t<_View>;
 151   using iterator_category = input_iterator_tag;
 152   using iterator_concept  = conditional_t<bidirectional_range<_View>, bidirectional_iterator_tag, forward_iterator_tag>;
 153
 154   _LIBCPP_HIDE_FROM_ABI __iterator() = default;
 155
 156   _LIBCPP_HIDE_FROM_ABI constexpr value_type operator*() const {
 157     _LIBCPP_ASSERT_UNCATEGORIZED(__current_ != __next_, "Trying to dereference past-the-end chunk_by_view iterator.");
 158     return {__current_, __next_};
 159   }
 160
 161   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator++() {
 162     _LIBCPP_ASSERT_UNCATEGORIZED(__current_ != __next_, "Trying to increment past end chunk_by_view iterator.");
 163     __current_ = __next_;
 164     __next_    = __parent_->__find_next(__current_);
 165     return *this;
 166   }
 167
 168   _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator++(int) {
 169     auto __tmp = *this;
 170     ++*this;
 171     return __tmp;
 172   }
 173
 174   _LIBCPP_HIDE_FROM_ABI constexpr __iterator& operator--()
 175     requires bidirectional_range<_View>
 176   {
 177     __next_    = __current_;
 178     __current_ = __parent_->__find_prev(__next_);
 179     return *this;
 180   }
 181
 182   _LIBCPP_HIDE_FROM_ABI constexpr __iterator operator--(int)
 183     requires bidirectional_range<_View>
 184   {
 185     auto __tmp = *this;
 186     --*this;
 187     return __tmp;
 188   }
 189
 190   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator& __x, const __iterator& __y) {
 191     return __x.__current_ == __y.__current_;
 192   }
 193
 194   _LIBCPP_HIDE_FROM_ABI friend constexpr bool operator==(const __iterator& __x, default_sentinel_t) {
 195     return __x.__current_ == __x.__next_;
 196   }
 197 };
 198
 199 namespace views {
 200 namespace __chunk_by {
 201 struct __fn {
 202   template <class _Range, class _Pred>
 203   _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Range&& __range, _Pred&& __pred) const
 204       noexcept(noexcept(/**/ chunk_by_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))))
 205           -> decltype(/*--*/ chunk_by_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred))) {
 206     return /*-------------*/ chunk_by_view(std::forward<_Range>(__range), std::forward<_Pred>(__pred));
 207   }
 208
 209   template <class _Pred>
 210     requires constructible_from<decay_t<_Pred>, _Pred>
 211   _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Pred&& __pred) const
 212       noexcept(is_nothrow_constructible_v<decay_t<_Pred>, _Pred>) {
 213     return __range_adaptor_closure_t(std::__bind_back(*this, std::forward<_Pred>(__pred)));
 214   }
 215 };
 216 } // namespace __chunk_by
 217
 218 inline namespace __cpo {
 219 inline constexpr auto chunk_by = __chunk_by::__fn{};
 220 } // namespace __cpo
 221 } // namespace views
 222 } // namespace ranges
 223
 224 #endif // _LIBCPP_STD_VER >= 23
 225
 226 _LIBCPP_END_NAMESPACE_STD
 227
 228 _LIBCPP_POP_MACROS
 229
 230 #endif // _LIBCPP___RANGES_CHUNK_BY_VIEW_H