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