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_SPAN
11#define _LIBCPP_SPAN
12
13/*
14 span synopsis
15
16namespace std {
17
18// constants
19inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max();
20
21template<class T>
22 concept integral-constant-like = // exposition only, since C++26
23 is_integral_v<decltype(T::value)> &&
24 !is_same_v<bool, remove_const_t<decltype(T::value)>> &&
25 convertible_to<T, decltype(T::value)> &&
26 equality_comparable_with<T, decltype(T::value)> &&
27 bool_constant<T() == T::value>::value &&
28 bool_constant<static_cast<decltype(T::value)>(T()) == T::value>::value;
29
30template<class T>
31 constexpr size_t maybe-static-ext = dynamic_extent; // exposition only, since C++26
32template<integral-constant-like T>
33 constexpr size_t maybe-static-ext<T> = {T::value};
34
35// [views.span], class template span
36template <class ElementType, size_t Extent = dynamic_extent>
37 class span;
38
39template<class ElementType, size_t Extent>
40 inline constexpr bool ranges::enable_view<span<ElementType, Extent>> = true;
41
42template<class ElementType, size_t Extent>
43 inline constexpr bool ranges::enable_borrowed_range<span<ElementType, Extent>> = true;
44
45// [span.objectrep], views of object representation
46template <class ElementType, size_t Extent>
47 span<const byte, ((Extent == dynamic_extent) ? dynamic_extent :
48 (sizeof(ElementType) * Extent))> as_bytes(span<ElementType, Extent> s) noexcept;
49
50template <class ElementType, size_t Extent>
51 span< byte, ((Extent == dynamic_extent) ? dynamic_extent :
52 (sizeof(ElementType) * Extent))> as_writable_bytes(span<ElementType, Extent> s) noexcept;
53
54
55template <class ElementType, size_t Extent = dynamic_extent>
56class span {
57public:
58 // constants and types
59 using element_type = ElementType;
60 using value_type = remove_cv_t<ElementType>;
61 using size_type = size_t;
62 using difference_type = ptrdiff_t;
63 using pointer = element_type*;
64 using const_pointer = const element_type*;
65 using reference = element_type&;
66 using const_reference = const element_type&;
67 using iterator = implementation-defined;
68 using reverse_iterator = std::reverse_iterator<iterator>;
69 static constexpr size_type extent = Extent;
70
71 // [span.cons], span constructors, copy, assignment, and destructor
72 constexpr span() noexcept;
73 template <class It>
74 constexpr explicit(Extent != dynamic_extent) span(It first, size_type count);
75 template <class It, class End>
76 constexpr explicit(Extent != dynamic_extent) span(It first, End last);
77 template <size_t N>
78 constexpr span(type_identity_t<element_type> (&arr)[N]) noexcept;
79 template <size_t N>
80 constexpr span(array<value_type, N>& arr) noexcept;
81 template <size_t N>
82 constexpr span(const array<value_type, N>& arr) noexcept;
83 template<class R>
84 constexpr explicit(Extent != dynamic_extent) span(R&& r);
85 constexpr explicit(extent != dynamic_extent) span(std::initializer_list<value_type> il); // Since C++26
86 constexpr span(const span& other) noexcept = default;
87 template <class OtherElementType, size_t OtherExtent>
88 constexpr explicit(Extent != dynamic_extent) span(const span<OtherElementType, OtherExtent>& s) noexcept;
89 constexpr span& operator=(const span& other) noexcept = default;
90
91 // [span.sub], span subviews
92 template <size_t Count>
93 constexpr span<element_type, Count> first() const;
94 template <size_t Count>
95 constexpr span<element_type, Count> last() const;
96 template <size_t Offset, size_t Count = dynamic_extent>
97 constexpr span<element_type, see below> subspan() const;
98
99 constexpr span<element_type, dynamic_extent> first(size_type count) const;
100 constexpr span<element_type, dynamic_extent> last(size_type count) const;
101 constexpr span<element_type, dynamic_extent> subspan(size_type offset, size_type count = dynamic_extent) const;
102
103 // [span.obs], span observers
104 constexpr size_type size() const noexcept;
105 constexpr size_type size_bytes() const noexcept;
106 [[nodiscard]] constexpr bool empty() const noexcept;
107
108 // [span.elem], span element access
109 constexpr reference operator[](size_type idx) const;
110 constexpr reference at(size_type idx) const; // since C++26
111 constexpr reference front() const;
112 constexpr reference back() const;
113 constexpr pointer data() const noexcept;
114
115 // [span.iterators], span iterator support
116 constexpr iterator begin() const noexcept;
117 constexpr iterator end() const noexcept;
118 constexpr reverse_iterator rbegin() const noexcept;
119 constexpr reverse_iterator rend() const noexcept;
120
121private:
122 pointer data_; // exposition only
123 size_type size_; // exposition only
124};
125
126template<class It, class EndOrSize>
127 span(It, EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>; // until C++26
128template<class It, class EndOrSize>
129 span(It, EndOrSize) -> span<remove_reference_t<iter_reference_t<It>>, maybe-static-ext<EndOrSize>>; // since C++26
130
131template<class T, size_t N>
132 span(T (&)[N]) -> span<T, N>;
133
134template<class T, size_t N>
135 span(array<T, N>&) -> span<T, N>;
136
137template<class T, size_t N>
138 span(const array<T, N>&) -> span<const T, N>;
139
140template<class R>
141 span(R&&) -> span<remove_reference_t<ranges::range_reference_t<R>>>;
142
143} // namespace std
144
145*/
146
147#if __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
148# include <__cxx03/__config>
149#else
150# include <__assert>
151# include <__concepts/convertible_to.h>
152# include <__concepts/equality_comparable.h>
153# include <__config>
154# include <__cstddef/byte.h>
155# include <__cstddef/ptrdiff_t.h>
156# include <__fwd/array.h>
157# include <__fwd/span.h>
158# include <__iterator/bounded_iter.h>
159# include <__iterator/concepts.h>
160# include <__iterator/iterator_traits.h>
161# include <__iterator/reverse_iterator.h>
162# include <__iterator/wrap_iter.h>
163# include <__memory/pointer_traits.h>
164# include <__ranges/concepts.h>
165# include <__ranges/data.h>
166# include <__ranges/enable_borrowed_range.h>
167# include <__ranges/enable_view.h>
168# include <__ranges/size.h>
169# include <__type_traits/integral_constant.h>
170# include <__type_traits/is_array.h>
171# include <__type_traits/is_const.h>
172# include <__type_traits/is_convertible.h>
173# include <__type_traits/is_integral.h>
174# include <__type_traits/is_same.h>
175# include <__type_traits/remove_const.h>
176# include <__type_traits/remove_cv.h>
177# include <__type_traits/remove_cvref.h>
178# include <__type_traits/remove_reference.h>
179# include <__type_traits/type_identity.h>
180# include <__utility/forward.h>
181# include <initializer_list>
182# include <stdexcept>
183# include <version>
184
185// standard-mandated includes
186
187// [iterator.range]
188# include <__iterator/access.h>
189# include <__iterator/data.h>
190# include <__iterator/empty.h>
191# include <__iterator/reverse_access.h>
192# include <__iterator/size.h>
193
194# if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
195# pragma GCC system_header
196# endif
197
198_LIBCPP_PUSH_MACROS
199# include <__undef_macros>
200
201_LIBCPP_BEGIN_NAMESPACE_STD
202
203# if _LIBCPP_STD_VER >= 20
204
205template <class _Tp>
206struct __is_std_span : false_type {};
207
208template <class _Tp, size_t _Sz>
209struct __is_std_span<span<_Tp, _Sz>> : true_type {};
210
211template <class _Range, class _ElementType>
212concept __span_compatible_range =
213 !__is_std_span<remove_cvref_t<_Range>>::value && //
214 ranges::contiguous_range<_Range> && //
215 ranges::sized_range<_Range> && //
216 (ranges::borrowed_range<_Range> || is_const_v<_ElementType>) && //
217 !__is_std_array_v<remove_cvref_t<_Range>> && //
218 !is_array_v<remove_cvref_t<_Range>> && //
219 is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>> (*)[], _ElementType (*)[]>;
220
221template <class _From, class _To>
222concept __span_array_convertible = is_convertible_v<_From (*)[], _To (*)[]>;
223
224template <class _It, class _Tp>
225concept __span_compatible_iterator =
226 contiguous_iterator<_It> && __span_array_convertible<remove_reference_t<iter_reference_t<_It>>, _Tp>;
227
228template <class _Sentinel, class _It>
229concept __span_compatible_sentinel_for = sized_sentinel_for<_Sentinel, _It> && !is_convertible_v<_Sentinel, size_t>;
230
231template <typename _Tp, size_t _Extent>
232class span {
233public:
234 // constants and types
235 using element_type = _Tp;
236 using value_type = remove_cv_t<_Tp>;
237 using size_type = size_t;
238 using difference_type = ptrdiff_t;
239 using pointer = _Tp*;
240 using const_pointer = const _Tp*;
241 using reference = _Tp&;
242 using const_reference = const _Tp&;
243# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
244 using iterator = __bounded_iter<pointer>;
245# else
246 using iterator = __wrap_iter<pointer>;
247# endif
248 using reverse_iterator = std::reverse_iterator<iterator>;
249
250 static constexpr size_type extent = _Extent;
251
252 // [span.cons], span constructors, copy, assignment, and destructor
253 template <size_t _Sz = _Extent>
254 requires(_Sz == 0)
255 _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr} {}
256
257# if _LIBCPP_STD_VER >= 26
258 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(std::initializer_list<value_type> __il)
259 requires is_const_v<element_type>
260 : __data_{__il.begin()} {
261 _LIBCPP_ASSERT_VALID_INPUT_RANGE(
262 _Extent == __il.size(), "Size mismatch in span's constructor _Extent != __il.size().");
263 }
264# endif
265
266 constexpr span(const span&) noexcept = default;
267 constexpr span& operator=(const span&) noexcept = default;
268
269 template <__span_compatible_iterator<element_type> _It>
270 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, size_type __count) : __data_{std::to_address(__first)} {
271 (void)__count;
272 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __count, "size mismatch in span's constructor (iterator, len)");
273 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__count == 0 || std::to_address(__first) != nullptr,
274 "passed nullptr with non-zero length in span's constructor (iterator, len)");
275 }
276
277 template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End>
278 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, _End __last) : __data_{std::to_address(__first)} {
279 // [span.cons]/10
280 // Throws: When and what last - first throws.
281 [[maybe_unused]] auto __dist = __last - __first;
282 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__dist >= 0, "invalid range in span's constructor (iterator, sentinel)");
283 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
284 __dist == _Extent, "invalid range in span's constructor (iterator, sentinel): last - first != extent");
285 }
286
287 _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Extent]) noexcept : __data_{__arr} {}
288
289 template <__span_array_convertible<element_type> _OtherElementType>
290 _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Extent>& __arr) noexcept : __data_{__arr.data()} {}
291
292 template <class _OtherElementType>
293 requires __span_array_convertible<const _OtherElementType, element_type>
294 _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Extent>& __arr) noexcept
295 : __data_{__arr.data()} {}
296
297 template <__span_compatible_range<element_type> _Range>
298 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_Range&& __r) : __data_{ranges::data(__r)} {
299 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(ranges::size(__r) == _Extent, "size mismatch in span's constructor (range)");
300 }
301
302 template <__span_array_convertible<element_type> _OtherElementType>
303 _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _Extent>& __other) noexcept
304 : __data_{__other.data()} {}
305
306 template <__span_array_convertible<element_type> _OtherElementType>
307 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(const span<_OtherElementType, dynamic_extent>& __other) noexcept
308 : __data_{__other.data()} {
309 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __other.size(), "size mismatch in span's constructor (other span)");
310 }
311
312 template <size_t _Count>
313 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept {
314 static_assert(_Count <= _Extent, "span<T, N>::first<Count>(): Count out of range");
315 return span<element_type, _Count>{data(), _Count};
316 }
317
318 template <size_t _Count>
319 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept {
320 static_assert(_Count <= _Extent, "span<T, N>::last<Count>(): Count out of range");
321 return span<element_type, _Count>{data() + size() - _Count, _Count};
322 }
323
324 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept {
325 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::first(count): count out of range");
326 return {data(), __count};
327 }
328
329 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept {
330 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::last(count): count out of range");
331 return {data() + size() - __count, __count};
332 }
333
334 template <size_t _Offset, size_t _Count = dynamic_extent>
335 _LIBCPP_HIDE_FROM_ABI constexpr auto
336 subspan() const noexcept -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset> {
337 static_assert(_Offset <= _Extent, "span<T, N>::subspan<Offset, Count>(): Offset out of range");
338 static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset,
339 "span<T, N>::subspan<Offset, Count>(): Offset + Count out of range");
340
341 using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>;
342 return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
343 }
344
345 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent>
346 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept {
347 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T, N>::subspan(offset, count): offset out of range");
348 if (__count == dynamic_extent)
349 return {data() + __offset, size() - __offset};
350 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
351 __count <= size() - __offset, "span<T, N>::subspan(offset, count): offset + count out of range");
352 return {data() + __offset, __count};
353 }
354
355 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return _Extent; }
356 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); }
357 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return _Extent == 0; }
358
359 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept {
360 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T, N>::operator[](index): index out of range");
361 return __data_[__idx];
362 }
363
364# if _LIBCPP_STD_VER >= 26
365 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const {
366 if (__index >= size())
367 std::__throw_out_of_range("span");
368 return __data_[__index];
369 }
370# endif
371
372 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept {
373 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::front() on empty span");
374 return __data_[0];
375 }
376
377 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept {
378 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::back() on empty span");
379 return __data_[size() - 1];
380 }
381
382 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; }
383
384 // [span.iter], span iterator support
385 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept {
386# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
387 return std::__make_bounded_iter(data(), data(), data() + size());
388# else
389 return iterator(data());
390# endif
391 }
392 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept {
393# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
394 return std::__make_bounded_iter(data() + size(), data(), data() + size());
395# else
396 return iterator(data() + size());
397# endif
398 }
399 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
400 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
401
402 _LIBCPP_HIDE_FROM_ABI span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept {
403 return span<const byte, _Extent * sizeof(element_type)>{reinterpret_cast<const byte*>(data()), size_bytes()};
404 }
405
406 _LIBCPP_HIDE_FROM_ABI span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept {
407 return span<byte, _Extent * sizeof(element_type)>{reinterpret_cast<byte*>(data()), size_bytes()};
408 }
409
410private:
411 pointer __data_;
412};
413
414template <typename _Tp>
415class span<_Tp, dynamic_extent> {
416public:
417 // constants and types
418 using element_type = _Tp;
419 using value_type = remove_cv_t<_Tp>;
420 using size_type = size_t;
421 using difference_type = ptrdiff_t;
422 using pointer = _Tp*;
423 using const_pointer = const _Tp*;
424 using reference = _Tp&;
425 using const_reference = const _Tp&;
426# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
427 using iterator = __bounded_iter<pointer>;
428# else
429 using iterator = __wrap_iter<pointer>;
430# endif
431 using reverse_iterator = std::reverse_iterator<iterator>;
432
433 static constexpr size_type extent = dynamic_extent;
434
435 // [span.cons], span constructors, copy, assignment, and destructor
436 _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr}, __size_{0} {}
437
438# if _LIBCPP_STD_VER >= 26
439 _LIBCPP_HIDE_FROM_ABI constexpr span(std::initializer_list<value_type> __il)
440 requires is_const_v<element_type>
441 : __data_{__il.begin()}, __size_{__il.size()} {}
442# endif
443
444 constexpr span(const span&) noexcept = default;
445 constexpr span& operator=(const span&) noexcept = default;
446
447 template <__span_compatible_iterator<element_type> _It>
448 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, size_type __count)
449 : __data_{std::to_address(__first)}, __size_{__count} {
450 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__count == 0 || std::to_address(__first) != nullptr,
451 "passed nullptr with non-zero length in span's constructor (iterator, len)");
452 }
453
454 template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End>
455 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, _End __last)
456 : __data_(std::to_address(__first)), __size_(__last - __first) {
457 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__last - __first >= 0, "invalid range in span's constructor (iterator, sentinel)");
458 }
459
460 template <size_t _Sz>
461 _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Sz]) noexcept
462 : __data_{__arr}, __size_{_Sz} {}
463
464 template <__span_array_convertible<element_type> _OtherElementType, size_t _Sz>
465 _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept
466 : __data_{__arr.data()}, __size_{_Sz} {}
467
468 template <class _OtherElementType, size_t _Sz>
469 requires __span_array_convertible<const _OtherElementType, element_type>
470 _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept
471 : __data_{__arr.data()}, __size_{_Sz} {}
472
473 template <__span_compatible_range<element_type> _Range>
474 _LIBCPP_HIDE_FROM_ABI constexpr span(_Range&& __r) : __data_(ranges::data(__r)), __size_{ranges::size(__r)} {}
475
476 template <__span_array_convertible<element_type> _OtherElementType, size_t _OtherExtent>
477 _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _OtherExtent>& __other) noexcept
478 : __data_{__other.data()}, __size_{__other.size()} {}
479
480 template <size_t _Count>
481 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept {
482 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::first<Count>(): Count out of range");
483 return span<element_type, _Count>{data(), _Count};
484 }
485
486 template <size_t _Count>
487 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept {
488 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::last<Count>(): Count out of range");
489 return span<element_type, _Count>{data() + size() - _Count, _Count};
490 }
491
492 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept {
493 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::first(count): count out of range");
494 return {data(), __count};
495 }
496
497 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept {
498 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::last(count): count out of range");
499 return {data() + size() - __count, __count};
500 }
501
502 template <size_t _Offset, size_t _Count = dynamic_extent>
503 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> subspan() const noexcept {
504 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Offset <= size(), "span<T>::subspan<Offset, Count>(): Offset out of range");
505 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count == dynamic_extent || _Count <= size() - _Offset,
506 "span<T>::subspan<Offset, Count>(): Offset + Count out of range");
507 return span<element_type, _Count>{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count};
508 }
509
510 constexpr span<element_type, dynamic_extent> _LIBCPP_HIDE_FROM_ABI
511 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept {
512 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T>::subspan(offset, count): offset out of range");
513 if (__count == dynamic_extent)
514 return {data() + __offset, size() - __offset};
515 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(
516 __count <= size() - __offset, "span<T>::subspan(offset, count): offset + count out of range");
517 return {data() + __offset, __count};
518 }
519
520 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return __size_; }
521 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return __size_ * sizeof(element_type); }
522 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return __size_ == 0; }
523
524 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept {
525 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T>::operator[](index): index out of range");
526 return __data_[__idx];
527 }
528
529# if _LIBCPP_STD_VER >= 26
530 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const {
531 if (__index >= size())
532 std::__throw_out_of_range("span");
533 return __data_[__index];
534 }
535# endif
536
537 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept {
538 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::front() on empty span");
539 return __data_[0];
540 }
541
542 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept {
543 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::back() on empty span");
544 return __data_[size() - 1];
545 }
546
547 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; }
548
549 // [span.iter], span iterator support
550 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept {
551# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
552 return std::__make_bounded_iter(data(), data(), data() + size());
553# else
554 return iterator(data());
555# endif
556 }
557 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept {
558# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS
559 return std::__make_bounded_iter(data() + size(), data(), data() + size());
560# else
561 return iterator(data() + size());
562# endif
563 }
564 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); }
565 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); }
566
567 _LIBCPP_HIDE_FROM_ABI span<const byte, dynamic_extent> __as_bytes() const noexcept {
568 return {reinterpret_cast<const byte*>(data()), size_bytes()};
569 }
570
571 _LIBCPP_HIDE_FROM_ABI span<byte, dynamic_extent> __as_writable_bytes() const noexcept {
572 return {reinterpret_cast<byte*>(data()), size_bytes()};
573 }
574
575private:
576 pointer __data_;
577 size_type __size_;
578};
579
580template <class _Tp, size_t _Extent>
581inline constexpr bool ranges::enable_borrowed_range<span<_Tp, _Extent> > = true;
582
583template <class _ElementType, size_t _Extent>
584inline constexpr bool ranges::enable_view<span<_ElementType, _Extent>> = true;
585
586// as_bytes & as_writable_bytes
587template <class _Tp, size_t _Extent>
588_LIBCPP_HIDE_FROM_ABI auto as_bytes(span<_Tp, _Extent> __s) noexcept {
589 return __s.__as_bytes();
590}
591
592template <class _Tp, size_t _Extent>
593 requires(!is_const_v<_Tp>)
594_LIBCPP_HIDE_FROM_ABI auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept {
595 return __s.__as_writable_bytes();
596}
597
598# if _LIBCPP_STD_VER >= 26
599template <class _Tp>
600concept __integral_constant_like =
601 is_integral_v<decltype(_Tp::value)> && !is_same_v<bool, remove_const_t<decltype(_Tp::value)>> &&
602 convertible_to<_Tp, decltype(_Tp::value)> && equality_comparable_with<_Tp, decltype(_Tp::value)> &&
603 bool_constant<_Tp() == _Tp::value>::value &&
604 bool_constant<static_cast<decltype(_Tp::value)>(_Tp()) == _Tp::value>::value;
605
606template <class _Tp>
607inline constexpr size_t __maybe_static_ext = dynamic_extent;
608
609template <__integral_constant_like _Tp>
610inline constexpr size_t __maybe_static_ext<_Tp> = {_Tp::value};
611
612template <contiguous_iterator _It, class _EndOrSize>
613span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>, __maybe_static_ext<_EndOrSize>>;
614# else
615template <contiguous_iterator _It, class _EndOrSize>
616span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>;
617# endif
618
619template <class _Tp, size_t _Sz>
620span(_Tp (&)[_Sz]) -> span<_Tp, _Sz>;
621
622template <class _Tp, size_t _Sz>
623span(array<_Tp, _Sz>&) -> span<_Tp, _Sz>;
624
625template <class _Tp, size_t _Sz>
626span(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>;
627
628template <ranges::contiguous_range _Range>
629span(_Range&&) -> span<remove_reference_t<ranges::range_reference_t<_Range>>>;
630
631# endif // _LIBCPP_STD_VER >= 20
632
633_LIBCPP_END_NAMESPACE_STD
634
635_LIBCPP_POP_MACROS
636
637# if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
638# include <array>
639# include <concepts>
640# include <functional>
641# include <iterator>
642# include <type_traits>
643# endif
644#endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS)
645
646#endif // _LIBCPP_SPAN
647