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> 131#include <__config> 132#include <__debug> 133#include <__iterator/concepts.h> 134#include <__iterator/wrap_iter.h> 135#include <__ranges/concepts.h> 136#include <__ranges/data.h> 137#include <__ranges/enable_borrowed_range.h> 138#include <__ranges/enable_view.h> 139#include <__ranges/size.h> 140#include <array> // for array 141#include <cstddef> // for byte 142#include <iterator> // for iterators 143#include <limits> 144#include <type_traits> // for remove_cv, etc 145#include <version> 146 147#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 148# pragma GCC system_header 149#endif 150 151_LIBCPP_PUSH_MACROS 152#include <__undef_macros> 153 154_LIBCPP_BEGIN_NAMESPACE_STD 155 156#if _LIBCPP_STD_VER > 17 157 158inline constexpr size_t dynamic_extent = numeric_limits<size_t>::max(); 159template <typename _Tp, size_t _Extent = dynamic_extent> class span; 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_INCOMPLETE_RANGES) 174// This is a temporary workaround until we ship <ranges> -- we've unfortunately been 175// shipping <span> before its API was finalized, and we used to provide a constructor 176// from container types that had the requirements below. To avoid breaking code that 177// has started relying on the range-based constructor until we ship all of <ranges>, 178// we emulate the constructor requirements like this. 179template <class _Range, class _ElementType> 180concept __span_compatible_range = 181 !__is_std_span<remove_cvref_t<_Range>>::value && 182 !__is_std_array<remove_cvref_t<_Range>>::value && 183 !is_array_v<remove_cvref_t<_Range>> && 184 requires (_Range&& __r) { 185 data(std::forward<_Range>(__r)); 186 size(std::forward<_Range>(__r)); 187 } && 188 is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>>(*)[], _ElementType(*)[]>; 189#else 190template <class _Range, class _ElementType> 191concept __span_compatible_range = 192 ranges::contiguous_range<_Range> && 193 ranges::sized_range<_Range> && 194 (ranges::borrowed_range<_Range> || is_const_v<_ElementType>) && 195 !__is_std_span<remove_cvref_t<_Range>>::value && 196 !__is_std_array<remove_cvref_t<_Range>>::value && 197 !is_array_v<remove_cvref_t<_Range>> && 198 is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>>(*)[], _ElementType(*)[]>; 199#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 200 201template <typename _Tp, size_t _Extent> 202class _LIBCPP_TEMPLATE_VIS span { 203public: 204// constants and types 205 using element_type = _Tp; 206 using value_type = remove_cv_t<_Tp>; 207 using size_type = size_t; 208 using difference_type = ptrdiff_t; 209 using pointer = _Tp *; 210 using const_pointer = const _Tp *; 211 using reference = _Tp &; 212 using const_reference = const _Tp &; 213#if (_LIBCPP_DEBUG_LEVEL == 2) || defined(_LIBCPP_ABI_SPAN_POINTER_ITERATORS) 214 using iterator = pointer; 215#else 216 using iterator = __wrap_iter<pointer>; 217#endif 218 using reverse_iterator = _VSTD::reverse_iterator<iterator>; 219 220 static constexpr size_type extent = _Extent; 221 222// [span.cons], span constructors, copy, assignment, and destructor 223 template <size_t _Sz = _Extent, enable_if_t<_Sz == 0, nullptr_t> = nullptr> 224 _LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr} {} 225 226 constexpr span (const span&) noexcept = default; 227 constexpr span& operator=(const span&) noexcept = default; 228 229 template <class _It, 230 enable_if_t<contiguous_iterator<_It> && 231 is_convertible_v<remove_reference_t<iter_reference_t<_It>>(*)[], element_type (*)[]>, 232 nullptr_t> = nullptr> 233 _LIBCPP_INLINE_VISIBILITY 234 constexpr explicit span(_It __first, size_type __count) 235 : __data{_VSTD::to_address(__first)} { 236 (void)__count; 237 _LIBCPP_ASSERT(_Extent == __count, "size mismatch in span's constructor (iterator, len)"); 238 } 239 240 template < 241 class _It, class _End, 242 enable_if_t<is_convertible_v<remove_reference_t<iter_reference_t<_It> > (*)[], element_type (*)[]> && 243 contiguous_iterator<_It> && sized_sentinel_for<_End, _It> && !is_convertible_v<_End, size_t>, 244 nullptr_t> = nullptr> 245 _LIBCPP_INLINE_VISIBILITY 246 constexpr explicit span(_It __first, _End __last) : __data{_VSTD::to_address(__first)} { 247 (void)__last; 248 _LIBCPP_ASSERT((__last - __first >= 0), "invalid range in span's constructor (iterator, sentinel)"); 249 _LIBCPP_ASSERT(__last - __first == _Extent, 250 "invalid range in span's constructor (iterator, sentinel): last - first != extent"); 251 } 252 253 _LIBCPP_INLINE_VISIBILITY constexpr span(type_identity_t<element_type> (&__arr)[_Extent]) noexcept : __data{__arr} {} 254 255 template <class _OtherElementType, 256 enable_if_t<is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr> 257 _LIBCPP_INLINE_VISIBILITY 258 constexpr span(array<_OtherElementType, _Extent>& __arr) noexcept : __data{__arr.data()} {} 259 260 template <class _OtherElementType, 261 enable_if_t<is_convertible_v<const _OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr> 262 _LIBCPP_INLINE_VISIBILITY 263 constexpr span(const array<_OtherElementType, _Extent>& __arr) noexcept : __data{__arr.data()} {} 264 265#if defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 266 template <class _Container> 267 requires __span_compatible_range<_Container, element_type> 268 _LIBCPP_INLINE_VISIBILITY 269 constexpr explicit span(_Container& __c) : __data{std::data(__c)} { 270 _LIBCPP_ASSERT(std::size(__c) == _Extent, "size mismatch in span's constructor (range)"); 271 } 272 template <class _Container> 273 requires __span_compatible_range<const _Container, element_type> 274 _LIBCPP_INLINE_VISIBILITY 275 constexpr explicit span(const _Container& __c) : __data{std::data(__c)} { 276 _LIBCPP_ASSERT(std::size(__c) == _Extent, "size mismatch in span's constructor (range)"); 277 } 278#else 279 template <__span_compatible_range<element_type> _Range> 280 _LIBCPP_INLINE_VISIBILITY 281 constexpr explicit span(_Range&& __r) : __data{ranges::data(__r)} { 282 _LIBCPP_ASSERT(ranges::size(__r) == _Extent, "size mismatch in span's constructor (range)"); 283 } 284#endif 285 286 template <class _OtherElementType> 287 _LIBCPP_INLINE_VISIBILITY 288 constexpr span(const span<_OtherElementType, _Extent>& __other, 289 enable_if_t< 290 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, 291 nullptr_t> = nullptr) 292 : __data{__other.data()} {} 293 294 template <class _OtherElementType> 295 _LIBCPP_INLINE_VISIBILITY 296 constexpr explicit span(const span<_OtherElementType, dynamic_extent>& __other, 297 enable_if_t< 298 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, 299 nullptr_t> = nullptr) noexcept 300 : __data{__other.data()} { _LIBCPP_ASSERT(_Extent == __other.size(), "size mismatch in span's constructor (other span)"); } 301 302 303// ~span() noexcept = default; 304 305 template <size_t _Count> 306 _LIBCPP_INLINE_VISIBILITY 307 constexpr span<element_type, _Count> first() const noexcept 308 { 309 static_assert(_Count <= _Extent, "Count out of range in span::first()"); 310 return span<element_type, _Count>{data(), _Count}; 311 } 312 313 template <size_t _Count> 314 _LIBCPP_INLINE_VISIBILITY 315 constexpr span<element_type, _Count> last() const noexcept 316 { 317 static_assert(_Count <= _Extent, "Count out of range in span::last()"); 318 return span<element_type, _Count>{data() + size() - _Count, _Count}; 319 } 320 321 _LIBCPP_INLINE_VISIBILITY 322 constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept 323 { 324 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)"); 325 return {data(), __count}; 326 } 327 328 _LIBCPP_INLINE_VISIBILITY 329 constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept 330 { 331 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)"); 332 return {data() + size() - __count, __count}; 333 } 334 335 template <size_t _Offset, size_t _Count = dynamic_extent> 336 _LIBCPP_INLINE_VISIBILITY 337 constexpr auto subspan() const noexcept 338 -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset> 339 { 340 static_assert(_Offset <= _Extent, "Offset out of range in span::subspan()"); 341 static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset, "Offset + count out of range in span::subspan()"); 342 343 using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>; 344 return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 345 } 346 347 348 _LIBCPP_INLINE_VISIBILITY 349 constexpr span<element_type, dynamic_extent> 350 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept 351 { 352 _LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)"); 353 _LIBCPP_ASSERT(__count <= size() || __count == dynamic_extent, "Count out of range in span::subspan(offset, count)"); 354 if (__count == dynamic_extent) 355 return {data() + __offset, size() - __offset}; 356 _LIBCPP_ASSERT(__count <= size() - __offset, "Offset + count out of range in span::subspan(offset, count)"); 357 return {data() + __offset, __count}; 358 } 359 360 _LIBCPP_INLINE_VISIBILITY constexpr size_type size() const noexcept { return _Extent; } 361 _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); } 362 [[nodiscard]] _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return _Extent == 0; } 363 364 _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept 365 { 366 _LIBCPP_ASSERT(__idx < size(), "span<T,N>[] index out of bounds"); 367 return __data[__idx]; 368 } 369 370 _LIBCPP_INLINE_VISIBILITY constexpr reference front() const noexcept 371 { 372 _LIBCPP_ASSERT(!empty(), "span<T, N>::front() on empty span"); 373 return __data[0]; 374 } 375 376 _LIBCPP_INLINE_VISIBILITY constexpr reference back() const noexcept 377 { 378 _LIBCPP_ASSERT(!empty(), "span<T, N>::back() on empty span"); 379 return __data[size()-1]; 380 } 381 382 _LIBCPP_INLINE_VISIBILITY constexpr pointer data() const noexcept { return __data; } 383 384// [span.iter], span iterator support 385 _LIBCPP_INLINE_VISIBILITY constexpr iterator begin() const noexcept { return iterator(data()); } 386 _LIBCPP_INLINE_VISIBILITY constexpr iterator end() const noexcept { return iterator(data() + size()); } 387 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 388 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 389 390 _LIBCPP_INLINE_VISIBILITY span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept 391 { return span<const byte, _Extent * sizeof(element_type)>{reinterpret_cast<const byte *>(data()), size_bytes()}; } 392 393 _LIBCPP_INLINE_VISIBILITY span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept 394 { return span<byte, _Extent * sizeof(element_type)>{reinterpret_cast<byte *>(data()), size_bytes()}; } 395 396private: 397 pointer __data; 398 399}; 400 401 402template <typename _Tp> 403class _LIBCPP_TEMPLATE_VIS span<_Tp, dynamic_extent> { 404private: 405 406public: 407// constants and types 408 using element_type = _Tp; 409 using value_type = remove_cv_t<_Tp>; 410 using size_type = size_t; 411 using difference_type = ptrdiff_t; 412 using pointer = _Tp *; 413 using const_pointer = const _Tp *; 414 using reference = _Tp &; 415 using const_reference = const _Tp &; 416#if (_LIBCPP_DEBUG_LEVEL == 2) || defined(_LIBCPP_ABI_SPAN_POINTER_ITERATORS) 417 using iterator = pointer; 418#else 419 using iterator = __wrap_iter<pointer>; 420#endif 421 using reverse_iterator = _VSTD::reverse_iterator<iterator>; 422 423 static constexpr size_type extent = dynamic_extent; 424 425// [span.cons], span constructors, copy, assignment, and destructor 426 _LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr}, __size{0} {} 427 428 constexpr span (const span&) noexcept = default; 429 constexpr span& operator=(const span&) noexcept = default; 430 431 template <class _It, 432 enable_if_t<contiguous_iterator<_It> && 433 is_convertible_v<remove_reference_t<iter_reference_t<_It> > (*)[], element_type (*)[]>, 434 nullptr_t> = nullptr> 435 _LIBCPP_INLINE_VISIBILITY 436 constexpr span(_It __first, size_type __count) 437 : __data{_VSTD::to_address(__first)}, __size{__count} {} 438 439 template < 440 class _It, class _End, 441 enable_if_t<is_convertible_v<remove_reference_t<iter_reference_t<_It> > (*)[], element_type (*)[]> && 442 contiguous_iterator<_It> && sized_sentinel_for<_End, _It> && !is_convertible_v<_End, size_t>, 443 nullptr_t> = nullptr> 444 _LIBCPP_INLINE_VISIBILITY 445 constexpr span(_It __first, _End __last) 446 : __data(_VSTD::to_address(__first)), __size(__last - __first) {} 447 448 template <size_t _Sz> 449 _LIBCPP_INLINE_VISIBILITY 450 constexpr span(type_identity_t<element_type> (&__arr)[_Sz]) noexcept : __data{__arr}, __size{_Sz} {} 451 452 template <class _OtherElementType, size_t _Sz, 453 enable_if_t<is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr> 454 _LIBCPP_INLINE_VISIBILITY 455 constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {} 456 457 template <class _OtherElementType, size_t _Sz, 458 enable_if_t<is_convertible_v<const _OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr> 459 _LIBCPP_INLINE_VISIBILITY 460 constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {} 461 462#if defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 463 template <class _Container> 464 requires __span_compatible_range<_Container, element_type> 465 _LIBCPP_INLINE_VISIBILITY 466 constexpr span(_Container& __c) : __data(std::data(__c)), __size{std::size(__c)} {} 467 template <class _Container> 468 requires __span_compatible_range<const _Container, element_type> 469 _LIBCPP_INLINE_VISIBILITY 470 constexpr span(const _Container& __c) : __data(std::data(__c)), __size{std::size(__c)} {} 471#else 472 template <__span_compatible_range<element_type> _Range> 473 _LIBCPP_INLINE_VISIBILITY 474 constexpr span(_Range&& __r) : __data(ranges::data(__r)), __size{ranges::size(__r)} {} 475#endif 476 477 template <class _OtherElementType, size_t _OtherExtent> 478 _LIBCPP_INLINE_VISIBILITY 479 constexpr span(const span<_OtherElementType, _OtherExtent>& __other, 480 enable_if_t< 481 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, 482 nullptr_t> = nullptr) noexcept 483 : __data{__other.data()}, __size{__other.size()} {} 484 485// ~span() noexcept = default; 486 487 template <size_t _Count> 488 _LIBCPP_INLINE_VISIBILITY 489 constexpr span<element_type, _Count> first() const noexcept 490 { 491 _LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::first()"); 492 return span<element_type, _Count>{data(), _Count}; 493 } 494 495 template <size_t _Count> 496 _LIBCPP_INLINE_VISIBILITY 497 constexpr span<element_type, _Count> last() const noexcept 498 { 499 _LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::last()"); 500 return span<element_type, _Count>{data() + size() - _Count, _Count}; 501 } 502 503 _LIBCPP_INLINE_VISIBILITY 504 constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept 505 { 506 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)"); 507 return {data(), __count}; 508 } 509 510 _LIBCPP_INLINE_VISIBILITY 511 constexpr span<element_type, dynamic_extent> last (size_type __count) const noexcept 512 { 513 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)"); 514 return {data() + size() - __count, __count}; 515 } 516 517 template <size_t _Offset, size_t _Count = dynamic_extent> 518 _LIBCPP_INLINE_VISIBILITY 519 constexpr span<element_type, _Count> subspan() const noexcept 520 { 521 _LIBCPP_ASSERT(_Offset <= size(), "Offset out of range in span::subspan()"); 522 _LIBCPP_ASSERT(_Count == dynamic_extent || _Count <= size() - _Offset, "Offset + count out of range in span::subspan()"); 523 return span<element_type, _Count>{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 524 } 525 526 constexpr span<element_type, dynamic_extent> 527 _LIBCPP_INLINE_VISIBILITY 528 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept 529 { 530 _LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)"); 531 _LIBCPP_ASSERT(__count <= size() || __count == dynamic_extent, "count out of range in span::subspan(offset, count)"); 532 if (__count == dynamic_extent) 533 return {data() + __offset, size() - __offset}; 534 _LIBCPP_ASSERT(__count <= size() - __offset, "Offset + count out of range in span::subspan(offset, count)"); 535 return {data() + __offset, __count}; 536 } 537 538 _LIBCPP_INLINE_VISIBILITY constexpr size_type size() const noexcept { return __size; } 539 _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return __size * sizeof(element_type); } 540 [[nodiscard]] _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return __size == 0; } 541 542 _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept 543 { 544 _LIBCPP_ASSERT(__idx < size(), "span<T>[] index out of bounds"); 545 return __data[__idx]; 546 } 547 548 _LIBCPP_INLINE_VISIBILITY constexpr reference front() const noexcept 549 { 550 _LIBCPP_ASSERT(!empty(), "span<T>[].front() on empty span"); 551 return __data[0]; 552 } 553 554 _LIBCPP_INLINE_VISIBILITY constexpr reference back() const noexcept 555 { 556 _LIBCPP_ASSERT(!empty(), "span<T>[].back() on empty span"); 557 return __data[size()-1]; 558 } 559 560 561 _LIBCPP_INLINE_VISIBILITY constexpr pointer data() const noexcept { return __data; } 562 563// [span.iter], span iterator support 564 _LIBCPP_INLINE_VISIBILITY constexpr iterator begin() const noexcept { return iterator(data()); } 565 _LIBCPP_INLINE_VISIBILITY constexpr iterator end() const noexcept { return iterator(data() + size()); } 566 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 567 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 568 569 _LIBCPP_INLINE_VISIBILITY span<const byte, dynamic_extent> __as_bytes() const noexcept 570 { return {reinterpret_cast<const byte *>(data()), size_bytes()}; } 571 572 _LIBCPP_INLINE_VISIBILITY span<byte, dynamic_extent> __as_writable_bytes() const noexcept 573 { return {reinterpret_cast<byte *>(data()), size_bytes()}; } 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_INLINE_VISIBILITY 589auto as_bytes(span<_Tp, _Extent> __s) noexcept 590-> decltype(__s.__as_bytes()) 591{ return __s.__as_bytes(); } 592 593template <class _Tp, size_t _Extent> 594_LIBCPP_INLINE_VISIBILITY 595auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept 596-> enable_if_t<!is_const_v<_Tp>, decltype(__s.__as_writable_bytes())> 597{ return __s.__as_writable_bytes(); } 598 599#if _LIBCPP_STD_VER > 17 600template<contiguous_iterator _It, class _EndOrSize> 601 span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>; 602#endif // _LIBCPP_STD_VER > 17 603 604template<class _Tp, size_t _Sz> 605 span(_Tp (&)[_Sz]) -> span<_Tp, _Sz>; 606 607template<class _Tp, size_t _Sz> 608 span(array<_Tp, _Sz>&) -> span<_Tp, _Sz>; 609 610template<class _Tp, size_t _Sz> 611 span(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>; 612 613#if !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 614template<ranges::contiguous_range _Range> 615 span(_Range&&) -> span<remove_reference_t<ranges::range_reference_t<_Range>>>; 616#endif 617 618#endif // _LIBCPP_STD_VER > 17 619 620_LIBCPP_END_NAMESPACE_STD 621 622_LIBCPP_POP_MACROS 623 624#endif // _LIBCPP_SPAN 625