1 // Utilities for representing and manipulating ranges -*- C++ -*-
2
3 // Copyright (C) 2019-2021 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24
25 /** @file bits/ranges_util.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{ranges}
28 */
29
30 #ifndef _RANGES_UTIL_H
31 #define _RANGES_UTIL_H 1
32
33 #if __cplusplus > 201703L
34 # include <bits/ranges_base.h>
35
36 #ifdef __cpp_lib_ranges
_GLIBCXX_VISIBILITY(default)37 namespace std _GLIBCXX_VISIBILITY(default)
38 {
39 _GLIBCXX_BEGIN_NAMESPACE_VERSION
40 namespace ranges
41 {
42 // C++20 24.5 [range.utility] Range utilities
43
44 namespace __detail
45 {
46 template<typename _Range>
47 concept __simple_view = view<_Range> && range<const _Range>
48 && same_as<iterator_t<_Range>, iterator_t<const _Range>>
49 && same_as<sentinel_t<_Range>, sentinel_t<const _Range>>;
50
51 template<typename _It>
52 concept __has_arrow = input_iterator<_It>
53 && (is_pointer_v<_It> || requires(_It __it) { __it.operator->(); });
54
55 template<typename _Tp, typename _Up>
56 concept __not_same_as
57 = !same_as<remove_cvref_t<_Tp>, remove_cvref_t<_Up>>;
58 } // namespace __detail
59
60 /// The ranges::view_interface class template
61 template<typename _Derived>
62 requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
63 class view_interface : public view_base
64 {
65 private:
66 constexpr _Derived& _M_derived() noexcept
67 {
68 static_assert(derived_from<_Derived, view_interface<_Derived>>);
69 static_assert(view<_Derived>);
70 return static_cast<_Derived&>(*this);
71 }
72
73 constexpr const _Derived& _M_derived() const noexcept
74 {
75 static_assert(derived_from<_Derived, view_interface<_Derived>>);
76 static_assert(view<_Derived>);
77 return static_cast<const _Derived&>(*this);
78 }
79
80 public:
81 constexpr bool
82 empty() requires forward_range<_Derived>
83 { return ranges::begin(_M_derived()) == ranges::end(_M_derived()); }
84
85 constexpr bool
86 empty() const requires forward_range<const _Derived>
87 { return ranges::begin(_M_derived()) == ranges::end(_M_derived()); }
88
89 constexpr explicit
90 operator bool() requires requires { ranges::empty(_M_derived()); }
91 { return !ranges::empty(_M_derived()); }
92
93 constexpr explicit
94 operator bool() const requires requires { ranges::empty(_M_derived()); }
95 { return !ranges::empty(_M_derived()); }
96
97 constexpr auto
98 data() requires contiguous_iterator<iterator_t<_Derived>>
99 { return to_address(ranges::begin(_M_derived())); }
100
101 constexpr auto
102 data() const
103 requires range<const _Derived>
104 && contiguous_iterator<iterator_t<const _Derived>>
105 { return to_address(ranges::begin(_M_derived())); }
106
107 constexpr auto
108 size()
109 requires forward_range<_Derived>
110 && sized_sentinel_for<sentinel_t<_Derived>, iterator_t<_Derived>>
111 { return ranges::end(_M_derived()) - ranges::begin(_M_derived()); }
112
113 constexpr auto
114 size() const
115 requires forward_range<const _Derived>
116 && sized_sentinel_for<sentinel_t<const _Derived>,
117 iterator_t<const _Derived>>
118 { return ranges::end(_M_derived()) - ranges::begin(_M_derived()); }
119
120 constexpr decltype(auto)
121 front() requires forward_range<_Derived>
122 {
123 __glibcxx_assert(!empty());
124 return *ranges::begin(_M_derived());
125 }
126
127 constexpr decltype(auto)
128 front() const requires forward_range<const _Derived>
129 {
130 __glibcxx_assert(!empty());
131 return *ranges::begin(_M_derived());
132 }
133
134 constexpr decltype(auto)
135 back()
136 requires bidirectional_range<_Derived> && common_range<_Derived>
137 {
138 __glibcxx_assert(!empty());
139 return *ranges::prev(ranges::end(_M_derived()));
140 }
141
142 constexpr decltype(auto)
143 back() const
144 requires bidirectional_range<const _Derived>
145 && common_range<const _Derived>
146 {
147 __glibcxx_assert(!empty());
148 return *ranges::prev(ranges::end(_M_derived()));
149 }
150
151 template<random_access_range _Range = _Derived>
152 constexpr decltype(auto)
153 operator[](range_difference_t<_Range> __n)
154 { return ranges::begin(_M_derived())[__n]; }
155
156 template<random_access_range _Range = const _Derived>
157 constexpr decltype(auto)
158 operator[](range_difference_t<_Range> __n) const
159 { return ranges::begin(_M_derived())[__n]; }
160 };
161
162 namespace __detail
163 {
164 template<class _From, class _To>
165 concept __convertible_to_non_slicing = convertible_to<_From, _To>
166 && !(is_pointer_v<decay_t<_From>> && is_pointer_v<decay_t<_To>>
167 && __not_same_as<remove_pointer_t<decay_t<_From>>,
168 remove_pointer_t<decay_t<_To>>>);
169
170 template<typename _Tp>
171 concept __pair_like
172 = !is_reference_v<_Tp> && requires(_Tp __t)
173 {
174 typename tuple_size<_Tp>::type;
175 requires derived_from<tuple_size<_Tp>, integral_constant<size_t, 2>>;
176 typename tuple_element_t<0, remove_const_t<_Tp>>;
177 typename tuple_element_t<1, remove_const_t<_Tp>>;
178 { get<0>(__t) } -> convertible_to<const tuple_element_t<0, _Tp>&>;
179 { get<1>(__t) } -> convertible_to<const tuple_element_t<1, _Tp>&>;
180 };
181
182 template<typename _Tp, typename _Up, typename _Vp>
183 concept __pair_like_convertible_from
184 = !range<_Tp> && __pair_like<_Tp>
185 && constructible_from<_Tp, _Up, _Vp>
186 && __convertible_to_non_slicing<_Up, tuple_element_t<0, _Tp>>
187 && convertible_to<_Vp, tuple_element_t<1, _Tp>>;
188
189 } // namespace __detail
190
191 enum class subrange_kind : bool { unsized, sized };
192
193 /// The ranges::subrange class template
194 template<input_or_output_iterator _It, sentinel_for<_It> _Sent = _It,
195 subrange_kind _Kind = sized_sentinel_for<_Sent, _It>
196 ? subrange_kind::sized : subrange_kind::unsized>
197 requires (_Kind == subrange_kind::sized || !sized_sentinel_for<_Sent, _It>)
198 class subrange : public view_interface<subrange<_It, _Sent, _Kind>>
199 {
200 private:
201 // XXX: gcc complains when using constexpr here
202 static const bool _S_store_size
203 = _Kind == subrange_kind::sized && !sized_sentinel_for<_Sent, _It>;
204
205 _It _M_begin = _It();
206 [[no_unique_address]] _Sent _M_end = _Sent();
207
208 using __size_type
209 = __detail::__make_unsigned_like_t<iter_difference_t<_It>>;
210
211 template<typename, bool = _S_store_size>
212 struct _Size
213 { };
214
215 template<typename _Tp>
216 struct _Size<_Tp, true>
217 { _Tp _M_size; };
218
219 [[no_unique_address]] _Size<__size_type> _M_size = {};
220
221 public:
222 subrange() = default;
223
224 constexpr
225 subrange(__detail::__convertible_to_non_slicing<_It> auto __i, _Sent __s)
226 requires (!_S_store_size)
227 : _M_begin(std::move(__i)), _M_end(__s)
228 { }
229
230 constexpr
231 subrange(__detail::__convertible_to_non_slicing<_It> auto __i, _Sent __s,
232 __size_type __n)
233 requires (_Kind == subrange_kind::sized)
234 : _M_begin(std::move(__i)), _M_end(__s)
235 {
236 if constexpr (_S_store_size)
237 _M_size._M_size = __n;
238 }
239
240 template<__detail::__not_same_as<subrange> _Rng>
241 requires borrowed_range<_Rng>
242 && __detail::__convertible_to_non_slicing<iterator_t<_Rng>, _It>
243 && convertible_to<sentinel_t<_Rng>, _Sent>
244 constexpr
245 subrange(_Rng&& __r) requires _S_store_size && sized_range<_Rng>
246 : subrange(__r, ranges::size(__r))
247 { }
248
249 template<__detail::__not_same_as<subrange> _Rng>
250 requires borrowed_range<_Rng>
251 && __detail::__convertible_to_non_slicing<iterator_t<_Rng>, _It>
252 && convertible_to<sentinel_t<_Rng>, _Sent>
253 constexpr
254 subrange(_Rng&& __r) requires (!_S_store_size)
255 : subrange(ranges::begin(__r), ranges::end(__r))
256 { }
257
258 template<borrowed_range _Rng>
259 requires __detail::__convertible_to_non_slicing<iterator_t<_Rng>, _It>
260 && convertible_to<sentinel_t<_Rng>, _Sent>
261 constexpr
262 subrange(_Rng&& __r, __size_type __n)
263 requires (_Kind == subrange_kind::sized)
264 : subrange{ranges::begin(__r), ranges::end(__r), __n}
265 { }
266
267 template<__detail::__not_same_as<subrange> _PairLike>
268 requires __detail::__pair_like_convertible_from<_PairLike, const _It&,
269 const _Sent&>
270 constexpr
271 operator _PairLike() const
272 { return _PairLike(_M_begin, _M_end); }
273
274 constexpr _It
275 begin() const requires copyable<_It>
276 { return _M_begin; }
277
278 [[nodiscard]] constexpr _It
279 begin() requires (!copyable<_It>)
280 { return std::move(_M_begin); }
281
282 constexpr _Sent end() const { return _M_end; }
283
284 constexpr bool empty() const { return _M_begin == _M_end; }
285
286 constexpr __size_type
287 size() const requires (_Kind == subrange_kind::sized)
288 {
289 if constexpr (_S_store_size)
290 return _M_size._M_size;
291 else
292 return __detail::__to_unsigned_like(_M_end - _M_begin);
293 }
294
295 [[nodiscard]] constexpr subrange
296 next(iter_difference_t<_It> __n = 1) const &
297 requires forward_iterator<_It>
298 {
299 auto __tmp = *this;
300 __tmp.advance(__n);
301 return __tmp;
302 }
303
304 [[nodiscard]] constexpr subrange
305 next(iter_difference_t<_It> __n = 1) &&
306 {
307 advance(__n);
308 return std::move(*this);
309 }
310
311 [[nodiscard]] constexpr subrange
312 prev(iter_difference_t<_It> __n = 1) const
313 requires bidirectional_iterator<_It>
314 {
315 auto __tmp = *this;
316 __tmp.advance(-__n);
317 return __tmp;
318 }
319
320 constexpr subrange&
321 advance(iter_difference_t<_It> __n)
322 {
323 // _GLIBCXX_RESOLVE_LIB_DEFECTS
324 // 3433. subrange::advance(n) has UB when n < 0
325 if constexpr (bidirectional_iterator<_It>)
326 if (__n < 0)
327 {
328 ranges::advance(_M_begin, __n);
329 if constexpr (_S_store_size)
330 _M_size._M_size += __detail::__to_unsigned_like(-__n);
331 return *this;
332 }
333
334 __glibcxx_assert(__n >= 0);
335 auto __d = __n - ranges::advance(_M_begin, __n, _M_end);
336 if constexpr (_S_store_size)
337 _M_size._M_size -= __detail::__to_unsigned_like(__d);
338 return *this;
339 }
340 };
341
342 template<input_or_output_iterator _It, sentinel_for<_It> _Sent>
343 subrange(_It, _Sent) -> subrange<_It, _Sent>;
344
345 template<input_or_output_iterator _It, sentinel_for<_It> _Sent>
346 subrange(_It, _Sent,
347 __detail::__make_unsigned_like_t<iter_difference_t<_It>>)
348 -> subrange<_It, _Sent, subrange_kind::sized>;
349
350 template<borrowed_range _Rng>
351 subrange(_Rng&&)
352 -> subrange<iterator_t<_Rng>, sentinel_t<_Rng>,
353 (sized_range<_Rng>
354 || sized_sentinel_for<sentinel_t<_Rng>, iterator_t<_Rng>>)
355 ? subrange_kind::sized : subrange_kind::unsized>;
356
357 template<borrowed_range _Rng>
358 subrange(_Rng&&,
359 __detail::__make_unsigned_like_t<range_difference_t<_Rng>>)
360 -> subrange<iterator_t<_Rng>, sentinel_t<_Rng>, subrange_kind::sized>;
361
362 template<size_t _Num, class _It, class _Sent, subrange_kind _Kind>
363 requires (_Num < 2)
364 constexpr auto
365 get(const subrange<_It, _Sent, _Kind>& __r)
366 {
367 if constexpr (_Num == 0)
368 return __r.begin();
369 else
370 return __r.end();
371 }
372
373 template<size_t _Num, class _It, class _Sent, subrange_kind _Kind>
374 requires (_Num < 2)
375 constexpr auto
376 get(subrange<_It, _Sent, _Kind>&& __r)
377 {
378 if constexpr (_Num == 0)
379 return __r.begin();
380 else
381 return __r.end();
382 }
383
384 template<input_or_output_iterator _It, sentinel_for<_It> _Sent,
385 subrange_kind _Kind>
386 inline constexpr bool
387 enable_borrowed_range<subrange<_It, _Sent, _Kind>> = true;
388
389 template<range _Range>
390 using borrowed_subrange_t = conditional_t<borrowed_range<_Range>,
391 subrange<iterator_t<_Range>>,
392 dangling>;
393
394 } // namespace ranges
395
396 using ranges::get;
397
398 template<typename _Iter, typename _Sent, ranges::subrange_kind _Kind>
399 struct tuple_size<ranges::subrange<_Iter, _Sent, _Kind>>
400 : integral_constant<size_t, 2>
401 { };
402
403 template<typename _Iter, typename _Sent, ranges::subrange_kind _Kind>
404 struct tuple_element<0, ranges::subrange<_Iter, _Sent, _Kind>>
405 { using type = _Iter; };
406
407 template<typename _Iter, typename _Sent, ranges::subrange_kind _Kind>
408 struct tuple_element<1, ranges::subrange<_Iter, _Sent, _Kind>>
409 { using type = _Sent; };
410
411 template<typename _Iter, typename _Sent, ranges::subrange_kind _Kind>
412 struct tuple_element<0, const ranges::subrange<_Iter, _Sent, _Kind>>
413 { using type = _Iter; };
414
415 template<typename _Iter, typename _Sent, ranges::subrange_kind _Kind>
416 struct tuple_element<1, const ranges::subrange<_Iter, _Sent, _Kind>>
417 { using type = _Sent; };
418
419 _GLIBCXX_END_NAMESPACE_VERSION
420 } // namespace std
421 #endif // library concepts
422 #endif // C++20
423 #endif // _RANGES_UTIL_H
424