1// Core algorithmic facilities -*- C++ -*-
2
3// Copyright (C) 2020-2025 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_algobase.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{algorithm}
28 */
29
30#ifndef _RANGES_ALGOBASE_H
31#define _RANGES_ALGOBASE_H 1
32
33#if __cplusplus > 201703L
34
35#include <compare>
36#include <bits/stl_iterator_base_funcs.h>
37#include <bits/stl_iterator.h>
38#include <bits/ranges_base.h> // ranges::begin, ranges::range etc.
39#include <bits/invoke.h> // __invoke
40#include <bits/cpp_type_traits.h> // __is_byte
41#include <bits/stl_algobase.h> // __memcmp
42
43#if __cpp_lib_concepts
44namespace std _GLIBCXX_VISIBILITY(default)
45{
46_GLIBCXX_BEGIN_NAMESPACE_VERSION
47namespace ranges
48{
49 namespace __detail
50 {
51 template<typename _Tp>
52 constexpr inline bool __is_normal_iterator = false;
53
54 template<typename _Iterator, typename _Container>
55 constexpr inline bool
56 __is_normal_iterator<__gnu_cxx::__normal_iterator<_Iterator,
57 _Container>> = true;
58
59 template<typename _Tp>
60 constexpr inline bool __is_reverse_iterator = false;
61
62 template<typename _Iterator>
63 constexpr inline bool
64 __is_reverse_iterator<reverse_iterator<_Iterator>> = true;
65
66 template<typename _Tp>
67 constexpr inline bool __is_move_iterator = false;
68
69 template<typename _Iterator>
70 constexpr inline bool
71 __is_move_iterator<move_iterator<_Iterator>> = true;
72 } // namespace __detail
73
74#if __glibcxx_ranges_iota >= 202202L // C++ >= 23
75 template<typename _Out, typename _Tp>
76 struct out_value_result
77 {
78 [[no_unique_address]] _Out out;
79 [[no_unique_address]] _Tp value;
80
81 template<typename _Out2, typename _Tp2>
82 requires convertible_to<const _Out&, _Out2>
83 && convertible_to<const _Tp&, _Tp2>
84 constexpr
85 operator out_value_result<_Out2, _Tp2>() const &
86 { return {out, value}; }
87
88 template<typename _Out2, typename _Tp2>
89 requires convertible_to<_Out, _Out2>
90 && convertible_to<_Tp, _Tp2>
91 constexpr
92 operator out_value_result<_Out2, _Tp2>() &&
93 { return {std::move(out), std::move(value)}; }
94 };
95#endif // __glibcxx_ranges_iota
96
97 struct __equal_fn
98 {
99 template<input_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
100 input_iterator _Iter2, sentinel_for<_Iter2> _Sent2,
101 typename _Pred = ranges::equal_to,
102 typename _Proj1 = identity, typename _Proj2 = identity>
103 requires indirectly_comparable<_Iter1, _Iter2, _Pred, _Proj1, _Proj2>
104 constexpr bool
105 operator()(_Iter1 __first1, _Sent1 __last1,
106 _Iter2 __first2, _Sent2 __last2, _Pred __pred = {},
107 _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const
108 {
109 // TODO: implement more specializations to at least have parity with
110 // std::equal.
111 if constexpr (__detail::__is_normal_iterator<_Iter1>
112 && same_as<_Iter1, _Sent1>)
113 return (*this)(__first1.base(), __last1.base(),
114 std::move(__first2), std::move(__last2),
115 std::move(__pred),
116 std::move(__proj1), std::move(__proj2));
117 else if constexpr (__detail::__is_normal_iterator<_Iter2>
118 && same_as<_Iter2, _Sent2>)
119 return (*this)(std::move(__first1), std::move(__last1),
120 __first2.base(), __last2.base(),
121 std::move(__pred),
122 std::move(__proj1), std::move(__proj2));
123 else if constexpr (sized_sentinel_for<_Sent1, _Iter1>
124 && sized_sentinel_for<_Sent2, _Iter2>)
125 {
126 auto __d1 = ranges::distance(__first1, __last1);
127 auto __d2 = ranges::distance(__first2, __last2);
128 if (__d1 != __d2)
129 return false;
130
131 using _ValueType1 = iter_value_t<_Iter1>;
132 constexpr bool __use_memcmp
133 = ((is_integral_v<_ValueType1> || is_pointer_v<_ValueType1>)
134 && __memcmpable<_Iter1, _Iter2>::__value
135 && is_same_v<_Pred, ranges::equal_to>
136 && is_same_v<_Proj1, identity>
137 && is_same_v<_Proj2, identity>);
138 if constexpr (__use_memcmp)
139 {
140 if (const size_t __len = (__last1 - __first1))
141 return !std::__memcmp(__first1, __first2, __len);
142 return true;
143 }
144 else
145 {
146 for (; __first1 != __last1; ++__first1, (void)++__first2)
147 if (!(bool)std::__invoke(__pred,
148 std::__invoke(__proj1, *__first1),
149 std::__invoke(__proj2, *__first2)))
150 return false;
151 return true;
152 }
153 }
154 else
155 {
156 for (; __first1 != __last1 && __first2 != __last2;
157 ++__first1, (void)++__first2)
158 if (!(bool)std::__invoke(__pred,
159 std::__invoke(__proj1, *__first1),
160 std::__invoke(__proj2, *__first2)))
161 return false;
162 return __first1 == __last1 && __first2 == __last2;
163 }
164 }
165
166 template<input_range _Range1, input_range _Range2,
167 typename _Pred = ranges::equal_to,
168 typename _Proj1 = identity, typename _Proj2 = identity>
169 requires indirectly_comparable<iterator_t<_Range1>, iterator_t<_Range2>,
170 _Pred, _Proj1, _Proj2>
171 constexpr bool
172 operator()(_Range1&& __r1, _Range2&& __r2, _Pred __pred = {},
173 _Proj1 __proj1 = {}, _Proj2 __proj2 = {}) const
174 {
175 // _GLIBCXX_RESOLVE_LIB_DEFECTS
176 // 3560. ranges::equal [...] should short-circuit for sized_ranges
177 if constexpr (sized_range<_Range1>)
178 if constexpr (sized_range<_Range2>)
179 if (ranges::distance(__r1) != ranges::distance(__r2))
180 return false;
181
182 return (*this)(ranges::begin(__r1), ranges::end(__r1),
183 ranges::begin(__r2), ranges::end(__r2),
184 std::move(__pred),
185 std::move(__proj1), std::move(__proj2));
186 }
187 };
188
189 inline constexpr __equal_fn equal{};
190
191namespace __detail
192{
193 template<bool _IsMove, typename _OutIter, typename _InIter>
194 [[__gnu__::__always_inline__]]
195 constexpr void
196 __assign_one(_OutIter& __out, _InIter& __in)
197 {
198 if constexpr (_IsMove)
199 *__out = ranges::iter_move(__in);
200 else
201 *__out = *__in;
202 }
203} // namespace __detail
204
205 template<typename _Iter, typename _Out>
206 struct in_out_result
207 {
208 [[no_unique_address]] _Iter in;
209 [[no_unique_address]] _Out out;
210
211 template<typename _Iter2, typename _Out2>
212 requires convertible_to<const _Iter&, _Iter2>
213 && convertible_to<const _Out&, _Out2>
214 constexpr
215 operator in_out_result<_Iter2, _Out2>() const &
216 { return {in, out}; }
217
218 template<typename _Iter2, typename _Out2>
219 requires convertible_to<_Iter, _Iter2>
220 && convertible_to<_Out, _Out2>
221 constexpr
222 operator in_out_result<_Iter2, _Out2>() &&
223 { return {std::move(in), std::move(out)}; }
224 };
225
226 template<typename _Iter, typename _Out>
227 using copy_result = in_out_result<_Iter, _Out>;
228
229 template<typename _Iter, typename _Out>
230 using move_result = in_out_result<_Iter, _Out>;
231
232 template<typename _Iter1, typename _Iter2>
233 using move_backward_result = in_out_result<_Iter1, _Iter2>;
234
235 template<typename _Iter1, typename _Iter2>
236 using copy_backward_result = in_out_result<_Iter1, _Iter2>;
237
238 template<bool _IsMove,
239 bidirectional_iterator _Iter, sentinel_for<_Iter> _Sent,
240 bidirectional_iterator _Out>
241 requires (_IsMove
242 ? indirectly_movable<_Iter, _Out>
243 : indirectly_copyable<_Iter, _Out>)
244 constexpr __conditional_t<_IsMove,
245 move_backward_result<_Iter, _Out>,
246 copy_backward_result<_Iter, _Out>>
247 __copy_or_move_backward(_Iter __first, _Sent __last, _Out __result);
248
249 template<bool _IsMove,
250 input_iterator _Iter, sentinel_for<_Iter> _Sent,
251 weakly_incrementable _Out>
252 requires (_IsMove
253 ? indirectly_movable<_Iter, _Out>
254 : indirectly_copyable<_Iter, _Out>)
255 constexpr __conditional_t<_IsMove,
256 move_result<_Iter, _Out>,
257 copy_result<_Iter, _Out>>
258 __copy_or_move(_Iter __first, _Sent __last, _Out __result)
259 {
260 // TODO: implement more specializations to be at least on par with
261 // std::copy/std::move.
262 using __detail::__is_move_iterator;
263 using __detail::__is_reverse_iterator;
264 using __detail::__is_normal_iterator;
265 if constexpr (__is_move_iterator<_Iter> && same_as<_Iter, _Sent>)
266 {
267 auto [__in, __out]
268 = ranges::__copy_or_move<true>(std::move(__first).base(),
269 std::move(__last).base(),
270 std::move(__result));
271 return {move_iterator{std::move(__in)}, std::move(__out)};
272 }
273 else if constexpr (__is_reverse_iterator<_Iter> && same_as<_Iter, _Sent>
274 && __is_reverse_iterator<_Out>)
275 {
276 auto [__in,__out]
277 = ranges::__copy_or_move_backward<_IsMove>(std::move(__last).base(),
278 std::move(__first).base(),
279 std::move(__result).base());
280 return {reverse_iterator{std::move(__in)},
281 reverse_iterator{std::move(__out)}};
282 }
283 else if constexpr (__is_normal_iterator<_Iter> && same_as<_Iter, _Sent>)
284 {
285 auto [__in,__out]
286 = ranges::__copy_or_move<_IsMove>(__first.base(), __last.base(),
287 std::move(__result));
288 return {decltype(__first){__in}, std::move(__out)};
289 }
290 else if constexpr (__is_normal_iterator<_Out>)
291 {
292 auto [__in,__out]
293 = ranges::__copy_or_move<_IsMove>(std::move(__first), __last, __result.base());
294 return {std::move(__in), decltype(__result){__out}};
295 }
296 else if constexpr (sized_sentinel_for<_Sent, _Iter>)
297 {
298 if (!std::__is_constant_evaluated())
299 {
300 if constexpr (__memcpyable<_Out, _Iter>::__value)
301 {
302 using _ValueTypeI = iter_value_t<_Iter>;
303 auto __num = __last - __first;
304 if (__num > 1) [[likely]]
305 __builtin_memmove(__result, __first,
306 sizeof(_ValueTypeI) * __num);
307 else if (__num == 1)
308 __detail::__assign_one<_IsMove>(__result, __first);
309 return {__first + __num, __result + __num};
310 }
311 }
312
313 for (auto __n = __last - __first; __n > 0; --__n)
314 {
315 __detail::__assign_one<_IsMove>(__result, __first);
316 ++__first;
317 ++__result;
318 }
319 return {std::move(__first), std::move(__result)};
320 }
321 else
322 {
323 while (__first != __last)
324 {
325 __detail::__assign_one<_IsMove>(__result, __first);
326 ++__first;
327 ++__result;
328 }
329 return {std::move(__first), std::move(__result)};
330 }
331 }
332
333 struct __copy_fn
334 {
335 template<input_iterator _Iter, sentinel_for<_Iter> _Sent,
336 weakly_incrementable _Out>
337 requires indirectly_copyable<_Iter, _Out>
338 constexpr copy_result<_Iter, _Out>
339 operator()(_Iter __first, _Sent __last, _Out __result) const
340 {
341 return ranges::__copy_or_move<false>(std::move(__first),
342 std::move(__last),
343 std::move(__result));
344 }
345
346 template<input_range _Range, weakly_incrementable _Out>
347 requires indirectly_copyable<iterator_t<_Range>, _Out>
348 constexpr copy_result<borrowed_iterator_t<_Range>, _Out>
349 operator()(_Range&& __r, _Out __result) const
350 {
351 return (*this)(ranges::begin(__r), ranges::end(__r),
352 std::move(__result));
353 }
354 };
355
356 inline constexpr __copy_fn copy{};
357
358 struct __move_fn
359 {
360 template<input_iterator _Iter, sentinel_for<_Iter> _Sent,
361 weakly_incrementable _Out>
362 requires indirectly_movable<_Iter, _Out>
363 constexpr move_result<_Iter, _Out>
364 operator()(_Iter __first, _Sent __last, _Out __result) const
365 {
366 return ranges::__copy_or_move<true>(std::move(__first),
367 std::move(__last),
368 std::move(__result));
369 }
370
371 template<input_range _Range, weakly_incrementable _Out>
372 requires indirectly_movable<iterator_t<_Range>, _Out>
373 constexpr move_result<borrowed_iterator_t<_Range>, _Out>
374 operator()(_Range&& __r, _Out __result) const
375 {
376 return (*this)(ranges::begin(__r), ranges::end(__r),
377 std::move(__result));
378 }
379 };
380
381 inline constexpr __move_fn move{};
382
383 template<bool _IsMove,
384 bidirectional_iterator _Iter, sentinel_for<_Iter> _Sent,
385 bidirectional_iterator _Out>
386 requires (_IsMove
387 ? indirectly_movable<_Iter, _Out>
388 : indirectly_copyable<_Iter, _Out>)
389 constexpr __conditional_t<_IsMove,
390 move_backward_result<_Iter, _Out>,
391 copy_backward_result<_Iter, _Out>>
392 __copy_or_move_backward(_Iter __first, _Sent __last, _Out __result)
393 {
394 // TODO: implement more specializations to be at least on par with
395 // std::copy_backward/std::move_backward.
396 using __detail::__is_reverse_iterator;
397 using __detail::__is_normal_iterator;
398 if constexpr (__is_reverse_iterator<_Iter> && same_as<_Iter, _Sent>
399 && __is_reverse_iterator<_Out>)
400 {
401 auto [__in,__out]
402 = ranges::__copy_or_move<_IsMove>(std::move(__last).base(),
403 std::move(__first).base(),
404 std::move(__result).base());
405 return {reverse_iterator{std::move(__in)},
406 reverse_iterator{std::move(__out)}};
407 }
408 else if constexpr (__is_normal_iterator<_Iter> && same_as<_Iter, _Sent>)
409 {
410 auto [__in,__out]
411 = ranges::__copy_or_move_backward<_IsMove>(__first.base(),
412 __last.base(),
413 std::move(__result));
414 return {decltype(__first){__in}, std::move(__out)};
415 }
416 else if constexpr (__is_normal_iterator<_Out>)
417 {
418 auto [__in,__out]
419 = ranges::__copy_or_move_backward<_IsMove>(std::move(__first),
420 std::move(__last),
421 __result.base());
422 return {std::move(__in), decltype(__result){__out}};
423 }
424 else if constexpr (sized_sentinel_for<_Sent, _Iter>)
425 {
426 if (!std::__is_constant_evaluated())
427 {
428 if constexpr (__memcpyable<_Out, _Iter>::__value)
429 {
430 using _ValueTypeI = iter_value_t<_Iter>;
431 auto __num = __last - __first;
432 __result -= __num;
433 if (__num > 1) [[likely]]
434 __builtin_memmove(__result, __first,
435 sizeof(_ValueTypeI) * __num);
436 else if (__num == 1)
437 __detail::__assign_one<_IsMove>(__result, __first);
438 return {__first + __num, __result};
439 }
440 }
441
442 auto __lasti = ranges::next(__first, __last);
443 auto __tail = __lasti;
444
445 for (auto __n = __last - __first; __n > 0; --__n)
446 {
447 --__tail;
448 --__result;
449 __detail::__assign_one<_IsMove>(__result, __tail);
450 }
451 return {std::move(__lasti), std::move(__result)};
452 }
453 else
454 {
455 auto __lasti = ranges::next(__first, __last);
456 auto __tail = __lasti;
457
458 while (__first != __tail)
459 {
460 --__tail;
461 --__result;
462 __detail::__assign_one<_IsMove>(__result, __tail);
463 }
464 return {std::move(__lasti), std::move(__result)};
465 }
466 }
467
468 struct __copy_backward_fn
469 {
470 template<bidirectional_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
471 bidirectional_iterator _Iter2>
472 requires indirectly_copyable<_Iter1, _Iter2>
473 constexpr copy_backward_result<_Iter1, _Iter2>
474 operator()(_Iter1 __first, _Sent1 __last, _Iter2 __result) const
475 {
476 return ranges::__copy_or_move_backward<false>(std::move(__first),
477 std::move(__last),
478 std::move(__result));
479 }
480
481 template<bidirectional_range _Range, bidirectional_iterator _Iter>
482 requires indirectly_copyable<iterator_t<_Range>, _Iter>
483 constexpr copy_backward_result<borrowed_iterator_t<_Range>, _Iter>
484 operator()(_Range&& __r, _Iter __result) const
485 {
486 return (*this)(ranges::begin(__r), ranges::end(__r),
487 std::move(__result));
488 }
489 };
490
491 inline constexpr __copy_backward_fn copy_backward{};
492
493 struct __move_backward_fn
494 {
495 template<bidirectional_iterator _Iter1, sentinel_for<_Iter1> _Sent1,
496 bidirectional_iterator _Iter2>
497 requires indirectly_movable<_Iter1, _Iter2>
498 constexpr move_backward_result<_Iter1, _Iter2>
499 operator()(_Iter1 __first, _Sent1 __last, _Iter2 __result) const
500 {
501 return ranges::__copy_or_move_backward<true>(std::move(__first),
502 std::move(__last),
503 std::move(__result));
504 }
505
506 template<bidirectional_range _Range, bidirectional_iterator _Iter>
507 requires indirectly_movable<iterator_t<_Range>, _Iter>
508 constexpr move_backward_result<borrowed_iterator_t<_Range>, _Iter>
509 operator()(_Range&& __r, _Iter __result) const
510 {
511 return (*this)(ranges::begin(__r), ranges::end(__r),
512 std::move(__result));
513 }
514 };
515
516 inline constexpr __move_backward_fn move_backward{};
517
518 template<typename _Iter, typename _Out>
519 using copy_n_result = in_out_result<_Iter, _Out>;
520
521 struct __copy_n_fn
522 {
523 template<input_iterator _Iter, weakly_incrementable _Out>
524 requires indirectly_copyable<_Iter, _Out>
525 constexpr copy_n_result<_Iter, _Out>
526 operator()(_Iter __first, iter_difference_t<_Iter> __n,
527 _Out __result) const
528 {
529 if constexpr (random_access_iterator<_Iter>)
530 {
531 if (__n > 0)
532 return ranges::copy(__first, __first + __n, std::move(__result));
533 }
534 else
535 {
536 for (; __n > 0; --__n, (void)++__result, (void)++__first)
537 *__result = *__first;
538 }
539 return {std::move(__first), std::move(__result)};
540 }
541 };
542
543 inline constexpr __copy_n_fn copy_n{};
544
545 struct __fill_n_fn
546 {
547 template<typename _Out,
548 typename _Tp _GLIBCXX26_DEF_VAL_T(iter_value_t<_Out>)>
549 requires output_iterator<_Out, const _Tp&>
550 constexpr _Out
551 operator()(_Out __first, iter_difference_t<_Out> __n,
552 const _Tp& __value) const
553 {
554 // TODO: implement more specializations to be at least on par with
555 // std::fill_n
556 if (__n <= 0)
557 return __first;
558
559 if constexpr (is_scalar_v<_Tp>)
560 {
561 // TODO: Generalize this optimization to contiguous iterators.
562 if constexpr (is_pointer_v<_Out>
563 // Note that __is_byte already implies !is_volatile.
564 && __is_byte<remove_pointer_t<_Out>>::__value
565 && integral<_Tp>)
566 {
567 if (!std::__is_constant_evaluated())
568 {
569 __builtin_memset(__first,
570 static_cast<unsigned char>(__value),
571 __n);
572 return __first + __n;
573 }
574 }
575
576 const auto __tmp = __value;
577 for (; __n > 0; --__n, (void)++__first)
578 *__first = __tmp;
579 return __first;
580 }
581 else
582 {
583 for (; __n > 0; --__n, (void)++__first)
584 *__first = __value;
585 return __first;
586 }
587 }
588 };
589
590 inline constexpr __fill_n_fn fill_n{};
591
592 struct __fill_fn
593 {
594 template<typename _Out,
595 sentinel_for<_Out> _Sent,
596 typename _Tp _GLIBCXX26_DEF_VAL_T(iter_value_t<_Out>)>
597 requires output_iterator<_Out, const _Tp&>
598 constexpr _Out
599 operator()(_Out __first, _Sent __last, const _Tp& __value) const
600 {
601 // TODO: implement more specializations to be at least on par with
602 // std::fill
603 if constexpr (sized_sentinel_for<_Sent, _Out>)
604 {
605 const auto __len = __last - __first;
606 return ranges::fill_n(std::move(__first), __len, __value);
607 }
608 else if constexpr (is_scalar_v<_Tp>)
609 {
610 const auto __tmp = __value;
611 for (; __first != __last; ++__first)
612 *__first = __tmp;
613 return __first;
614 }
615 else
616 {
617 for (; __first != __last; ++__first)
618 *__first = __value;
619 return __first;
620 }
621 }
622
623 template<typename _Range,
624 typename _Tp _GLIBCXX26_DEF_VAL_T(range_value_t<_Range>)>
625 requires output_range<_Range, const _Tp&>
626 constexpr borrowed_iterator_t<_Range>
627 operator()(_Range&& __r, const _Tp& __value) const
628 {
629 return (*this)(ranges::begin(__r), ranges::end(__r), __value);
630 }
631 };
632
633 inline constexpr __fill_fn fill{};
634}
635_GLIBCXX_END_NAMESPACE_VERSION
636} // namespace std
637#endif // concepts
638#endif // C++20
639#endif // _RANGES_ALGOBASE_H
640