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_SUBRANGE_H
10 #define _LIBCPP___RANGES_SUBRANGE_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/different_from.h>
17 #include <__config>
18 #include <__debug>
19 #include <__iterator/advance.h>
20 #include <__iterator/concepts.h>
21 #include <__iterator/incrementable_traits.h>
22 #include <__iterator/iterator_traits.h>
23 #include <__ranges/access.h>
24 #include <__ranges/concepts.h>
25 #include <__ranges/dangling.h>
26 #include <__ranges/enable_borrowed_range.h>
27 #include <__ranges/size.h>
28 #include <__ranges/view_interface.h>
29 #include <__tuple>
30 #include <__utility/move.h>
31 #include <type_traits>
32 
33 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
34 #pragma GCC system_header
35 #endif
36 
37 _LIBCPP_BEGIN_NAMESPACE_STD
38 
39 #if !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
40 
41 namespace ranges {
42   template<class _From, class _To>
43   concept __uses_nonqualification_pointer_conversion =
44     is_pointer_v<_From> && is_pointer_v<_To> &&
45     !convertible_to<remove_pointer_t<_From>(*)[], remove_pointer_t<_To>(*)[]>;
46 
47   template<class _From, class _To>
48   concept __convertible_to_non_slicing =
49     convertible_to<_From, _To> &&
50     !__uses_nonqualification_pointer_conversion<decay_t<_From>, decay_t<_To>>;
51 
52   template<class _Tp>
53   concept __pair_like =
54     !is_reference_v<_Tp> && requires(_Tp __t) {
55       typename tuple_size<_Tp>::type; // Ensures `tuple_size<T>` is complete.
56       requires derived_from<tuple_size<_Tp>, integral_constant<size_t, 2>>;
57       typename tuple_element_t<0, remove_const_t<_Tp>>;
58       typename tuple_element_t<1, remove_const_t<_Tp>>;
59       { _VSTD::get<0>(__t) } -> convertible_to<const tuple_element_t<0, _Tp>&>;
60       { _VSTD::get<1>(__t) } -> convertible_to<const tuple_element_t<1, _Tp>&>;
61     };
62 
63   template<class _Pair, class _Iter, class _Sent>
64   concept __pair_like_convertible_from =
65     !range<_Pair> && __pair_like<_Pair> &&
66     constructible_from<_Pair, _Iter, _Sent> &&
67     __convertible_to_non_slicing<_Iter, tuple_element_t<0, _Pair>> &&
68     convertible_to<_Sent, tuple_element_t<1, _Pair>>;
69 
70   enum class _LIBCPP_ENUM_VIS subrange_kind : bool { unsized, sized };
71 
72   template<input_or_output_iterator _Iter, sentinel_for<_Iter> _Sent = _Iter,
73            subrange_kind _Kind = sized_sentinel_for<_Sent, _Iter>
74              ? subrange_kind::sized
75              : subrange_kind::unsized>
76     requires (_Kind == subrange_kind::sized || !sized_sentinel_for<_Sent, _Iter>)
77   class _LIBCPP_TEMPLATE_VIS subrange
78     : public view_interface<subrange<_Iter, _Sent, _Kind>>
79   {
80   private:
81     static constexpr bool _StoreSize = (_Kind == subrange_kind::sized && !sized_sentinel_for<_Sent, _Iter>);
82     static constexpr bool _MustProvideSizeAtConstruction = !_StoreSize; // just to improve compiler diagnostics
83     struct _Empty { constexpr _Empty(auto) noexcept { } };
84     using _Size = conditional_t<_StoreSize, make_unsigned_t<iter_difference_t<_Iter>>, _Empty>;
85     [[no_unique_address]] _Iter __begin_ = _Iter();
86     [[no_unique_address]] _Sent __end_ = _Sent();
87     [[no_unique_address]] _Size __size_ = 0;
88 
89   public:
90     _LIBCPP_HIDE_FROM_ABI
91     subrange() requires default_initializable<_Iter> = default;
92 
93     _LIBCPP_HIDE_FROM_ABI
94     constexpr subrange(__convertible_to_non_slicing<_Iter> auto __iter, _Sent __sent)
95       requires _MustProvideSizeAtConstruction
96       : __begin_(_VSTD::move(__iter)), __end_(_VSTD::move(__sent))
97     { }
98 
99     _LIBCPP_HIDE_FROM_ABI
100     constexpr subrange(__convertible_to_non_slicing<_Iter> auto __iter, _Sent __sent,
101                        make_unsigned_t<iter_difference_t<_Iter>> __n)
102       requires (_Kind == subrange_kind::sized)
103       : __begin_(_VSTD::move(__iter)), __end_(_VSTD::move(__sent)), __size_(__n)
104     {
105       if constexpr (sized_sentinel_for<_Sent, _Iter>)
106         _LIBCPP_ASSERT((__end_ - __begin_) == static_cast<iter_difference_t<_Iter>>(__n),
107           "std::ranges::subrange was passed an invalid size hint");
108     }
109 
110     template<__different_from<subrange> _Range>
111       requires borrowed_range<_Range> &&
112                __convertible_to_non_slicing<iterator_t<_Range>, _Iter> &&
113                convertible_to<sentinel_t<_Range>, _Sent>
114     _LIBCPP_HIDE_FROM_ABI
115     constexpr subrange(_Range&& __range)
116       requires (!_StoreSize)
117       : subrange(ranges::begin(__range), ranges::end(__range))
118     { }
119 
120     template<__different_from<subrange> _Range>
121       requires borrowed_range<_Range> &&
122                __convertible_to_non_slicing<iterator_t<_Range>, _Iter> &&
123                convertible_to<sentinel_t<_Range>, _Sent>
124     _LIBCPP_HIDE_FROM_ABI
125     constexpr subrange(_Range&& __range)
126       requires _StoreSize && sized_range<_Range>
127       : subrange(__range, ranges::size(__range))
128     { }
129 
130     template<borrowed_range _Range>
131       requires __convertible_to_non_slicing<iterator_t<_Range>, _Iter> &&
132                convertible_to<sentinel_t<_Range>, _Sent>
133     _LIBCPP_HIDE_FROM_ABI
134     constexpr subrange(_Range&& __range, make_unsigned_t<iter_difference_t<_Iter>> __n)
135       requires (_Kind == subrange_kind::sized)
136       : subrange(ranges::begin(__range), ranges::end(__range), __n)
137     { }
138 
139     template<__different_from<subrange> _Pair>
140       requires __pair_like_convertible_from<_Pair, const _Iter&, const _Sent&>
141     _LIBCPP_HIDE_FROM_ABI
142     constexpr operator _Pair() const {
143       return _Pair(__begin_, __end_);
144     }
145 
146     _LIBCPP_HIDE_FROM_ABI
147     constexpr _Iter begin() const requires copyable<_Iter> {
148       return __begin_;
149     }
150 
151     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Iter begin() requires (!copyable<_Iter>) {
152       return _VSTD::move(__begin_);
153     }
154 
155     _LIBCPP_HIDE_FROM_ABI
156     constexpr _Sent end() const {
157       return __end_;
158     }
159 
160     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const {
161       return __begin_ == __end_;
162     }
163 
164     _LIBCPP_HIDE_FROM_ABI
165     constexpr make_unsigned_t<iter_difference_t<_Iter>> size() const
166       requires (_Kind == subrange_kind::sized)
167     {
168       if constexpr (_StoreSize)
169         return __size_;
170       else
171         return _VSTD::__to_unsigned_like(__end_ - __begin_);
172     }
173 
174     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr subrange next(iter_difference_t<_Iter> __n = 1) const&
175       requires forward_iterator<_Iter>
176     {
177       auto __tmp = *this;
178       __tmp.advance(__n);
179       return __tmp;
180     }
181 
182     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr subrange next(iter_difference_t<_Iter> __n = 1) && {
183       advance(__n);
184       return _VSTD::move(*this);
185     }
186 
187     [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr subrange prev(iter_difference_t<_Iter> __n = 1) const
188       requires bidirectional_iterator<_Iter>
189     {
190       auto __tmp = *this;
191       __tmp.advance(-__n);
192       return __tmp;
193     }
194 
195     _LIBCPP_HIDE_FROM_ABI
196     constexpr subrange& advance(iter_difference_t<_Iter> __n) {
197       if constexpr (bidirectional_iterator<_Iter>) {
198         if (__n < 0) {
199           ranges::advance(__begin_, __n);
200           if constexpr (_StoreSize)
201             __size_ += _VSTD::__to_unsigned_like(-__n);
202           return *this;
203         }
204       }
205 
206       auto __d = __n - ranges::advance(__begin_, __n, __end_);
207       if constexpr (_StoreSize)
208         __size_ -= _VSTD::__to_unsigned_like(__d);
209       return *this;
210     }
211   };
212 
213   template<input_or_output_iterator _Iter, sentinel_for<_Iter> _Sent>
214   subrange(_Iter, _Sent) -> subrange<_Iter, _Sent>;
215 
216   template<input_or_output_iterator _Iter, sentinel_for<_Iter> _Sent>
217   subrange(_Iter, _Sent, make_unsigned_t<iter_difference_t<_Iter>>)
218     -> subrange<_Iter, _Sent, subrange_kind::sized>;
219 
220   template<borrowed_range _Range>
221   subrange(_Range&&) -> subrange<iterator_t<_Range>, sentinel_t<_Range>,
222                                  (sized_range<_Range> || sized_sentinel_for<sentinel_t<_Range>, iterator_t<_Range>>)
223                                    ? subrange_kind::sized : subrange_kind::unsized>;
224 
225   template<borrowed_range _Range>
226   subrange(_Range&&, make_unsigned_t<range_difference_t<_Range>>)
227     -> subrange<iterator_t<_Range>, sentinel_t<_Range>, subrange_kind::sized>;
228 
229   template<size_t _Index, class _Iter, class _Sent, subrange_kind _Kind>
230     requires ((_Index == 0 && copyable<_Iter>) || _Index == 1)
231   _LIBCPP_HIDE_FROM_ABI
232   constexpr auto get(const subrange<_Iter, _Sent, _Kind>& __subrange) {
233     if constexpr (_Index == 0)
234       return __subrange.begin();
235     else
236       return __subrange.end();
237   }
238 
239   template<size_t _Index, class _Iter, class _Sent, subrange_kind _Kind>
240     requires (_Index < 2)
241   _LIBCPP_HIDE_FROM_ABI
242   constexpr auto get(subrange<_Iter, _Sent, _Kind>&& __subrange) {
243     if constexpr (_Index == 0)
244       return __subrange.begin();
245     else
246       return __subrange.end();
247   }
248 
249   template<class _Ip, class _Sp, subrange_kind _Kp>
250   inline constexpr bool enable_borrowed_range<subrange<_Ip, _Sp, _Kp>> = true;
251 
252   template<range _Rp>
253   using borrowed_subrange_t = _If<borrowed_range<_Rp>, subrange<iterator_t<_Rp>>, dangling>;
254 } // namespace ranges
255 
256 // [range.subrange.general]
257 
258 using ranges::get;
259 
260 // [ranges.syn]
261 
262 template<class _Ip, class _Sp, ranges::subrange_kind _Kp>
263 struct tuple_size<ranges::subrange<_Ip, _Sp, _Kp>> : integral_constant<size_t, 2> {};
264 
265 template<class _Ip, class _Sp, ranges::subrange_kind _Kp>
266 struct tuple_element<0, ranges::subrange<_Ip, _Sp, _Kp>> {
267   using type = _Ip;
268 };
269 
270 template<class _Ip, class _Sp, ranges::subrange_kind _Kp>
271 struct tuple_element<1, ranges::subrange<_Ip, _Sp, _Kp>> {
272   using type = _Sp;
273 };
274 
275 template<class _Ip, class _Sp, ranges::subrange_kind _Kp>
276 struct tuple_element<0, const ranges::subrange<_Ip, _Sp, _Kp>> {
277   using type = _Ip;
278 };
279 
280 template<class _Ip, class _Sp, ranges::subrange_kind _Kp>
281 struct tuple_element<1, const ranges::subrange<_Ip, _Sp, _Kp>> {
282   using type = _Sp;
283 };
284 
285 #endif // !defined(_LIBCPP_HAS_NO_CONCEPTS) && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
286 
287 _LIBCPP_END_NAMESPACE_STD
288 
289 #endif // _LIBCPP___RANGES_SUBRANGE_H
290