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 <__config> 131#include <__debug> 132#include <__iterator/concepts.h> 133#include <__iterator/wrap_iter.h> 134#include <__ranges/concepts.h> 135#include <__ranges/data.h> 136#include <__ranges/enable_borrowed_range.h> 137#include <__ranges/enable_view.h> 138#include <__ranges/size.h> 139#include <array> // for array 140#include <cstddef> // for byte 141#include <iterator> // for iterators 142#include <limits> 143#include <type_traits> // for remove_cv, etc 144#include <version> 145 146#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 147#pragma GCC system_header 148#endif 149 150_LIBCPP_PUSH_MACROS 151#include <__undef_macros> 152 153_LIBCPP_BEGIN_NAMESPACE_STD 154 155#if _LIBCPP_STD_VER > 17 156 157inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max(); 158template <typename _Tp, size_t _Extent = dynamic_extent> class span; 159 160 161template <class _Tp> 162struct __is_std_array : false_type {}; 163 164template <class _Tp, size_t _Sz> 165struct __is_std_array<array<_Tp, _Sz>> : true_type {}; 166 167template <class _Tp> 168struct __is_std_span : false_type {}; 169 170template <class _Tp, size_t _Sz> 171struct __is_std_span<span<_Tp, _Sz>> : true_type {}; 172 173#if !defined(_LIBCPP_HAS_NO_RANGES) 174template <class _Range, class _ElementType> 175concept __span_compatible_range = 176 ranges::contiguous_range<_Range> && 177 ranges::sized_range<_Range> && 178 (ranges::borrowed_range<_Range> || is_const_v<_ElementType>) && 179 !__is_std_span<remove_cvref_t<_Range>>::value && 180 !__is_std_array<remove_cvref_t<_Range>>::value && 181 !is_array_v<remove_cvref_t<_Range>> && 182 is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>>(*)[], _ElementType(*)[]>; 183#endif 184 185template <typename _Tp, size_t _Extent> 186class _LIBCPP_TEMPLATE_VIS span { 187public: 188// constants and types 189 using element_type = _Tp; 190 using value_type = remove_cv_t<_Tp>; 191 using size_type = size_t; 192 using difference_type = ptrdiff_t; 193 using pointer = _Tp *; 194 using const_pointer = const _Tp *; 195 using reference = _Tp &; 196 using const_reference = const _Tp &; 197#if (_LIBCPP_DEBUG_LEVEL == 2) || defined(_LIBCPP_ABI_SPAN_POINTER_ITERATORS) 198 using iterator = pointer; 199#else 200 using iterator = __wrap_iter<pointer>; 201#endif 202 using reverse_iterator = _VSTD::reverse_iterator<iterator>; 203 204 static constexpr size_type extent = _Extent; 205 206// [span.cons], span constructors, copy, assignment, and destructor 207 template <size_t _Sz = _Extent, enable_if_t<_Sz == 0, nullptr_t> = nullptr> 208 _LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr} {} 209 210 constexpr span (const span&) noexcept = default; 211 constexpr span& operator=(const span&) noexcept = default; 212 213#if !defined(_LIBCPP_HAS_NO_RANGES) 214 template <class _It, 215 enable_if_t<contiguous_iterator<_It> && 216 is_convertible_v<remove_reference_t<iter_reference_t<_It>>(*)[], element_type (*)[]>, 217 nullptr_t> = nullptr> 218 _LIBCPP_INLINE_VISIBILITY 219 constexpr explicit span(_It __first, size_type __count) 220 : __data{_VSTD::to_address(__first)} { 221 (void)__count; 222 _LIBCPP_ASSERT(_Extent == __count, "size mismatch in span's constructor (iterator, len)"); 223 } 224 225 template < 226 class _It, class _End, 227 enable_if_t<is_convertible_v<remove_reference_t<iter_reference_t<_It> > (*)[], element_type (*)[]> && 228 contiguous_iterator<_It> && sized_sentinel_for<_End, _It> && !is_convertible_v<_End, size_t>, 229 nullptr_t> = nullptr> 230 _LIBCPP_INLINE_VISIBILITY 231 constexpr explicit span(_It __first, _End __last) : __data{_VSTD::to_address(__first)} { 232 (void)__last; 233 _LIBCPP_ASSERT((__last - __first >= 0), "invalid range in span's constructor (iterator, sentinel)"); 234 _LIBCPP_ASSERT(__last - __first == _Extent, 235 "invalid range in span's constructor (iterator, sentinel): last - first != extent"); 236 } 237#endif 238 239 _LIBCPP_INLINE_VISIBILITY constexpr span(type_identity_t<element_type> (&__arr)[_Extent]) noexcept : __data{__arr} {} 240 241 template <class _OtherElementType, 242 enable_if_t<is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr> 243 _LIBCPP_INLINE_VISIBILITY 244 constexpr span(array<_OtherElementType, _Extent>& __arr) noexcept : __data{__arr.data()} {} 245 246 template <class _OtherElementType, 247 enable_if_t<is_convertible_v<const _OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr> 248 _LIBCPP_INLINE_VISIBILITY 249 constexpr span(const array<_OtherElementType, _Extent>& __arr) noexcept : __data{__arr.data()} {} 250 251#if !defined(_LIBCPP_HAS_NO_RANGES) 252 template <__span_compatible_range<element_type> _Range> 253 _LIBCPP_INLINE_VISIBILITY 254 constexpr explicit span(_Range&& __r) : __data{ranges::data(__r)} { 255 _LIBCPP_ASSERT(ranges::size(__r) == _Extent, "size mismatch in span's constructor (range)"); 256 } 257#endif 258 259 template <class _OtherElementType> 260 _LIBCPP_INLINE_VISIBILITY 261 constexpr span(const span<_OtherElementType, _Extent>& __other, 262 enable_if_t< 263 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, 264 nullptr_t> = nullptr) 265 : __data{__other.data()} {} 266 267 template <class _OtherElementType> 268 _LIBCPP_INLINE_VISIBILITY 269 constexpr explicit span(const span<_OtherElementType, dynamic_extent>& __other, 270 enable_if_t< 271 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, 272 nullptr_t> = nullptr) noexcept 273 : __data{__other.data()} { _LIBCPP_ASSERT(_Extent == __other.size(), "size mismatch in span's constructor (other span)"); } 274 275 276// ~span() noexcept = default; 277 278 template <size_t _Count> 279 _LIBCPP_INLINE_VISIBILITY 280 constexpr span<element_type, _Count> first() const noexcept 281 { 282 static_assert(_Count <= _Extent, "Count out of range in span::first()"); 283 return span<element_type, _Count>{data(), _Count}; 284 } 285 286 template <size_t _Count> 287 _LIBCPP_INLINE_VISIBILITY 288 constexpr span<element_type, _Count> last() const noexcept 289 { 290 static_assert(_Count <= _Extent, "Count out of range in span::last()"); 291 return span<element_type, _Count>{data() + size() - _Count, _Count}; 292 } 293 294 _LIBCPP_INLINE_VISIBILITY 295 constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept 296 { 297 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)"); 298 return {data(), __count}; 299 } 300 301 _LIBCPP_INLINE_VISIBILITY 302 constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept 303 { 304 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)"); 305 return {data() + size() - __count, __count}; 306 } 307 308 template <size_t _Offset, size_t _Count = dynamic_extent> 309 _LIBCPP_INLINE_VISIBILITY 310 constexpr auto subspan() const noexcept 311 -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset> 312 { 313 static_assert(_Offset <= _Extent, "Offset out of range in span::subspan()"); 314 static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset, "Offset + count out of range in span::subspan()"); 315 316 using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>; 317 return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 318 } 319 320 321 _LIBCPP_INLINE_VISIBILITY 322 constexpr span<element_type, dynamic_extent> 323 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept 324 { 325 _LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)"); 326 _LIBCPP_ASSERT(__count <= size() || __count == dynamic_extent, "Count out of range in span::subspan(offset, count)"); 327 if (__count == dynamic_extent) 328 return {data() + __offset, size() - __offset}; 329 _LIBCPP_ASSERT(__count <= size() - __offset, "Offset + count out of range in span::subspan(offset, count)"); 330 return {data() + __offset, __count}; 331 } 332 333 _LIBCPP_INLINE_VISIBILITY constexpr size_type size() const noexcept { return _Extent; } 334 _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); } 335 [[nodiscard]] _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return _Extent == 0; } 336 337 _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept 338 { 339 _LIBCPP_ASSERT(__idx < size(), "span<T,N>[] index out of bounds"); 340 return __data[__idx]; 341 } 342 343 _LIBCPP_INLINE_VISIBILITY constexpr reference front() const noexcept 344 { 345 _LIBCPP_ASSERT(!empty(), "span<T, N>::front() on empty span"); 346 return __data[0]; 347 } 348 349 _LIBCPP_INLINE_VISIBILITY constexpr reference back() const noexcept 350 { 351 _LIBCPP_ASSERT(!empty(), "span<T, N>::back() on empty span"); 352 return __data[size()-1]; 353 } 354 355 _LIBCPP_INLINE_VISIBILITY constexpr pointer data() const noexcept { return __data; } 356 357// [span.iter], span iterator support 358 _LIBCPP_INLINE_VISIBILITY constexpr iterator begin() const noexcept { return iterator(data()); } 359 _LIBCPP_INLINE_VISIBILITY constexpr iterator end() const noexcept { return iterator(data() + size()); } 360 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 361 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 362 363 _LIBCPP_INLINE_VISIBILITY span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept 364 { return span<const byte, _Extent * sizeof(element_type)>{reinterpret_cast<const byte *>(data()), size_bytes()}; } 365 366 _LIBCPP_INLINE_VISIBILITY span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept 367 { return span<byte, _Extent * sizeof(element_type)>{reinterpret_cast<byte *>(data()), size_bytes()}; } 368 369private: 370 pointer __data; 371 372}; 373 374 375template <typename _Tp> 376class _LIBCPP_TEMPLATE_VIS span<_Tp, dynamic_extent> { 377private: 378 379public: 380// constants and types 381 using element_type = _Tp; 382 using value_type = remove_cv_t<_Tp>; 383 using size_type = size_t; 384 using difference_type = ptrdiff_t; 385 using pointer = _Tp *; 386 using const_pointer = const _Tp *; 387 using reference = _Tp &; 388 using const_reference = const _Tp &; 389#if (_LIBCPP_DEBUG_LEVEL == 2) || defined(_LIBCPP_ABI_SPAN_POINTER_ITERATORS) 390 using iterator = pointer; 391#else 392 using iterator = __wrap_iter<pointer>; 393#endif 394 using reverse_iterator = _VSTD::reverse_iterator<iterator>; 395 396 static constexpr size_type extent = dynamic_extent; 397 398// [span.cons], span constructors, copy, assignment, and destructor 399 _LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr}, __size{0} {} 400 401 constexpr span (const span&) noexcept = default; 402 constexpr span& operator=(const span&) noexcept = default; 403 404#if !defined(_LIBCPP_HAS_NO_RANGES) 405 template <class _It, 406 enable_if_t<contiguous_iterator<_It> && 407 is_convertible_v<remove_reference_t<iter_reference_t<_It> > (*)[], element_type (*)[]>, 408 nullptr_t> = nullptr> 409 _LIBCPP_INLINE_VISIBILITY 410 constexpr span(_It __first, size_type __count) 411 : __data{_VSTD::to_address(__first)}, __size{__count} {} 412 413 template < 414 class _It, class _End, 415 enable_if_t<is_convertible_v<remove_reference_t<iter_reference_t<_It> > (*)[], element_type (*)[]> && 416 contiguous_iterator<_It> && sized_sentinel_for<_End, _It> && !is_convertible_v<_End, size_t>, 417 nullptr_t> = nullptr> 418 _LIBCPP_INLINE_VISIBILITY 419 constexpr span(_It __first, _End __last) 420 : __data(_VSTD::to_address(__first)), __size(__last - __first) {} 421#endif 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 <class _OtherElementType, size_t _Sz, 428 enable_if_t<is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr> 429 _LIBCPP_INLINE_VISIBILITY 430 constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {} 431 432 template <class _OtherElementType, size_t _Sz, 433 enable_if_t<is_convertible_v<const _OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr> 434 _LIBCPP_INLINE_VISIBILITY 435 constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {} 436 437#if !defined(_LIBCPP_HAS_NO_RANGES) 438 template <__span_compatible_range<element_type> _Range> 439 _LIBCPP_INLINE_VISIBILITY 440 constexpr span(_Range&& __r) : __data(ranges::data(__r)), __size{ranges::size(__r)} {} 441# endif 442 443 template <class _OtherElementType, size_t _OtherExtent> 444 _LIBCPP_INLINE_VISIBILITY 445 constexpr span(const span<_OtherElementType, _OtherExtent>& __other, 446 enable_if_t< 447 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, 448 nullptr_t> = nullptr) noexcept 449 : __data{__other.data()}, __size{__other.size()} {} 450 451// ~span() noexcept = default; 452 453 template <size_t _Count> 454 _LIBCPP_INLINE_VISIBILITY 455 constexpr span<element_type, _Count> first() const noexcept 456 { 457 _LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::first()"); 458 return span<element_type, _Count>{data(), _Count}; 459 } 460 461 template <size_t _Count> 462 _LIBCPP_INLINE_VISIBILITY 463 constexpr span<element_type, _Count> last() const noexcept 464 { 465 _LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::last()"); 466 return span<element_type, _Count>{data() + size() - _Count, _Count}; 467 } 468 469 _LIBCPP_INLINE_VISIBILITY 470 constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept 471 { 472 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)"); 473 return {data(), __count}; 474 } 475 476 _LIBCPP_INLINE_VISIBILITY 477 constexpr span<element_type, dynamic_extent> last (size_type __count) const noexcept 478 { 479 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)"); 480 return {data() + size() - __count, __count}; 481 } 482 483 template <size_t _Offset, size_t _Count = dynamic_extent> 484 _LIBCPP_INLINE_VISIBILITY 485 constexpr span<element_type, _Count> subspan() const noexcept 486 { 487 _LIBCPP_ASSERT(_Offset <= size(), "Offset out of range in span::subspan()"); 488 _LIBCPP_ASSERT(_Count == dynamic_extent || _Count <= size() - _Offset, "Offset + count out of range in span::subspan()"); 489 return span<element_type, _Count>{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 490 } 491 492 constexpr span<element_type, dynamic_extent> 493 _LIBCPP_INLINE_VISIBILITY 494 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept 495 { 496 _LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)"); 497 _LIBCPP_ASSERT(__count <= size() || __count == dynamic_extent, "count out of range in span::subspan(offset, count)"); 498 if (__count == dynamic_extent) 499 return {data() + __offset, size() - __offset}; 500 _LIBCPP_ASSERT(__count <= size() - __offset, "Offset + count out of range in span::subspan(offset, count)"); 501 return {data() + __offset, __count}; 502 } 503 504 _LIBCPP_INLINE_VISIBILITY constexpr size_type size() const noexcept { return __size; } 505 _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return __size * sizeof(element_type); } 506 [[nodiscard]] _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return __size == 0; } 507 508 _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept 509 { 510 _LIBCPP_ASSERT(__idx < size(), "span<T>[] index out of bounds"); 511 return __data[__idx]; 512 } 513 514 _LIBCPP_INLINE_VISIBILITY constexpr reference front() const noexcept 515 { 516 _LIBCPP_ASSERT(!empty(), "span<T>[].front() on empty span"); 517 return __data[0]; 518 } 519 520 _LIBCPP_INLINE_VISIBILITY constexpr reference back() const noexcept 521 { 522 _LIBCPP_ASSERT(!empty(), "span<T>[].back() on empty span"); 523 return __data[size()-1]; 524 } 525 526 527 _LIBCPP_INLINE_VISIBILITY constexpr pointer data() const noexcept { return __data; } 528 529// [span.iter], span iterator support 530 _LIBCPP_INLINE_VISIBILITY constexpr iterator begin() const noexcept { return iterator(data()); } 531 _LIBCPP_INLINE_VISIBILITY constexpr iterator end() const noexcept { return iterator(data() + size()); } 532 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 533 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 534 535 _LIBCPP_INLINE_VISIBILITY span<const byte, dynamic_extent> __as_bytes() const noexcept 536 { return {reinterpret_cast<const byte *>(data()), size_bytes()}; } 537 538 _LIBCPP_INLINE_VISIBILITY span<byte, dynamic_extent> __as_writable_bytes() const noexcept 539 { return {reinterpret_cast<byte *>(data()), size_bytes()}; } 540 541private: 542 pointer __data; 543 size_type __size; 544}; 545 546#if !defined(_LIBCPP_HAS_NO_RANGES) 547template <class _Tp, size_t _Extent> 548inline constexpr bool ranges::enable_borrowed_range<span<_Tp, _Extent> > = true; 549 550template <class _ElementType, size_t _Extent> 551inline constexpr bool ranges::enable_view<span<_ElementType, _Extent>> = true; 552#endif // !defined(_LIBCPP_HAS_NO_RANGES) 553 554// as_bytes & as_writable_bytes 555template <class _Tp, size_t _Extent> 556_LIBCPP_INLINE_VISIBILITY 557auto as_bytes(span<_Tp, _Extent> __s) noexcept 558-> decltype(__s.__as_bytes()) 559{ return __s.__as_bytes(); } 560 561template <class _Tp, size_t _Extent> 562_LIBCPP_INLINE_VISIBILITY 563auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept 564-> enable_if_t<!is_const_v<_Tp>, decltype(__s.__as_writable_bytes())> 565{ return __s.__as_writable_bytes(); } 566 567#if !defined(_LIBCPP_HAS_NO_RANGES) 568// Deduction guides 569template<contiguous_iterator _It, class _EndOrSize> 570 span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>; 571#endif 572 573template<class _Tp, size_t _Sz> 574 span(_Tp (&)[_Sz]) -> span<_Tp, _Sz>; 575 576template<class _Tp, size_t _Sz> 577 span(array<_Tp, _Sz>&) -> span<_Tp, _Sz>; 578 579template<class _Tp, size_t _Sz> 580 span(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>; 581 582#if !defined(_LIBCPP_HAS_NO_RANGES) 583template<ranges::contiguous_range _Range> 584 span(_Range&&) -> span<remove_reference_t<ranges::range_reference_t<_Range>>>; 585#endif 586 587#endif // _LIBCPP_STD_VER > 17 588 589_LIBCPP_END_NAMESPACE_STD 590 591_LIBCPP_POP_MACROS 592 593#endif // _LIBCPP_SPAN 594