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#include <__assert> 148#include <__concepts/convertible_to.h> 149#include <__concepts/equality_comparable.h> 150#include <__config> 151#include <__cstddef/byte.h> 152#include <__cstddef/ptrdiff_t.h> 153#include <__fwd/array.h> 154#include <__fwd/span.h> 155#include <__iterator/bounded_iter.h> 156#include <__iterator/concepts.h> 157#include <__iterator/iterator_traits.h> 158#include <__iterator/reverse_iterator.h> 159#include <__iterator/wrap_iter.h> 160#include <__memory/pointer_traits.h> 161#include <__ranges/concepts.h> 162#include <__ranges/data.h> 163#include <__ranges/enable_borrowed_range.h> 164#include <__ranges/enable_view.h> 165#include <__ranges/size.h> 166#include <__type_traits/integral_constant.h> 167#include <__type_traits/is_array.h> 168#include <__type_traits/is_const.h> 169#include <__type_traits/is_convertible.h> 170#include <__type_traits/is_integral.h> 171#include <__type_traits/is_same.h> 172#include <__type_traits/remove_const.h> 173#include <__type_traits/remove_cv.h> 174#include <__type_traits/remove_cvref.h> 175#include <__type_traits/remove_reference.h> 176#include <__type_traits/type_identity.h> 177#include <__utility/forward.h> 178#include <initializer_list> 179#include <stdexcept> 180#include <version> 181 182// standard-mandated includes 183 184// [iterator.range] 185#include <__iterator/access.h> 186#include <__iterator/data.h> 187#include <__iterator/empty.h> 188#include <__iterator/reverse_access.h> 189#include <__iterator/size.h> 190 191#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 192# pragma GCC system_header 193#endif 194 195_LIBCPP_PUSH_MACROS 196#include <__undef_macros> 197 198_LIBCPP_BEGIN_NAMESPACE_STD 199 200#if _LIBCPP_STD_VER >= 20 201 202template <class _Tp> 203struct __is_std_span : false_type {}; 204 205template <class _Tp, size_t _Sz> 206struct __is_std_span<span<_Tp, _Sz>> : true_type {}; 207 208template <class _Range, class _ElementType> 209concept __span_compatible_range = 210 !__is_std_span<remove_cvref_t<_Range>>::value && // 211 ranges::contiguous_range<_Range> && // 212 ranges::sized_range<_Range> && // 213 (ranges::borrowed_range<_Range> || is_const_v<_ElementType>) && // 214 !__is_std_array_v<remove_cvref_t<_Range>> && // 215 !is_array_v<remove_cvref_t<_Range>> && // 216 is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>> (*)[], _ElementType (*)[]>; 217 218template <class _From, class _To> 219concept __span_array_convertible = is_convertible_v<_From (*)[], _To (*)[]>; 220 221template <class _It, class _Tp> 222concept __span_compatible_iterator = 223 contiguous_iterator<_It> && __span_array_convertible<remove_reference_t<iter_reference_t<_It>>, _Tp>; 224 225template <class _Sentinel, class _It> 226concept __span_compatible_sentinel_for = sized_sentinel_for<_Sentinel, _It> && !is_convertible_v<_Sentinel, size_t>; 227 228template <typename _Tp, size_t _Extent> 229class _LIBCPP_TEMPLATE_VIS span { 230public: 231 // constants and types 232 using element_type = _Tp; 233 using value_type = remove_cv_t<_Tp>; 234 using size_type = size_t; 235 using difference_type = ptrdiff_t; 236 using pointer = _Tp*; 237 using const_pointer = const _Tp*; 238 using reference = _Tp&; 239 using const_reference = const _Tp&; 240# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 241 using iterator = __bounded_iter<pointer>; 242# else 243 using iterator = __wrap_iter<pointer>; 244# endif 245 using reverse_iterator = std::reverse_iterator<iterator>; 246 247 static constexpr size_type extent = _Extent; 248 249 // [span.cons], span constructors, copy, assignment, and destructor 250 template <size_t _Sz = _Extent> 251 requires(_Sz == 0) 252 _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr} {} 253 254# if _LIBCPP_STD_VER >= 26 255 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(std::initializer_list<value_type> __il) 256 requires is_const_v<element_type> 257 : __data_{__il.begin()} { 258 _LIBCPP_ASSERT_VALID_INPUT_RANGE( 259 _Extent == __il.size(), "Size mismatch in span's constructor _Extent != __il.size()."); 260 } 261# endif 262 263 constexpr span(const span&) noexcept = default; 264 constexpr span& operator=(const span&) noexcept = default; 265 266 template <__span_compatible_iterator<element_type> _It> 267 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, size_type __count) : __data_{std::to_address(__first)} { 268 (void)__count; 269 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __count, "size mismatch in span's constructor (iterator, len)"); 270 } 271 272 template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End> 273 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, _End __last) : __data_{std::to_address(__first)} { 274 // [span.cons]/10 275 // Throws: When and what last - first throws. 276 [[maybe_unused]] auto __dist = __last - __first; 277 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__dist >= 0, "invalid range in span's constructor (iterator, sentinel)"); 278 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 279 __dist == _Extent, "invalid range in span's constructor (iterator, sentinel): last - first != extent"); 280 } 281 282 _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Extent]) noexcept : __data_{__arr} {} 283 284 template <__span_array_convertible<element_type> _OtherElementType> 285 _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Extent>& __arr) noexcept : __data_{__arr.data()} {} 286 287 template <class _OtherElementType> 288 requires __span_array_convertible<const _OtherElementType, element_type> 289 _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Extent>& __arr) noexcept 290 : __data_{__arr.data()} {} 291 292 template <__span_compatible_range<element_type> _Range> 293 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_Range&& __r) : __data_{ranges::data(__r)} { 294 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(ranges::size(__r) == _Extent, "size mismatch in span's constructor (range)"); 295 } 296 297 template <__span_array_convertible<element_type> _OtherElementType> 298 _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _Extent>& __other) noexcept 299 : __data_{__other.data()} {} 300 301 template <__span_array_convertible<element_type> _OtherElementType> 302 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(const span<_OtherElementType, dynamic_extent>& __other) noexcept 303 : __data_{__other.data()} { 304 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __other.size(), "size mismatch in span's constructor (other span)"); 305 } 306 307 template <size_t _Count> 308 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept { 309 static_assert(_Count <= _Extent, "span<T, N>::first<Count>(): Count out of range"); 310 return span<element_type, _Count>{data(), _Count}; 311 } 312 313 template <size_t _Count> 314 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept { 315 static_assert(_Count <= _Extent, "span<T, N>::last<Count>(): Count out of range"); 316 return span<element_type, _Count>{data() + size() - _Count, _Count}; 317 } 318 319 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept { 320 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::first(count): count out of range"); 321 return {data(), __count}; 322 } 323 324 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept { 325 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::last(count): count out of range"); 326 return {data() + size() - __count, __count}; 327 } 328 329 template <size_t _Offset, size_t _Count = dynamic_extent> 330 _LIBCPP_HIDE_FROM_ABI constexpr auto 331 subspan() const noexcept -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset> { 332 static_assert(_Offset <= _Extent, "span<T, N>::subspan<Offset, Count>(): Offset out of range"); 333 static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset, 334 "span<T, N>::subspan<Offset, Count>(): Offset + Count out of range"); 335 336 using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>; 337 return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 338 } 339 340 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> 341 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept { 342 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T, N>::subspan(offset, count): offset out of range"); 343 if (__count == dynamic_extent) 344 return {data() + __offset, size() - __offset}; 345 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 346 __count <= size() - __offset, "span<T, N>::subspan(offset, count): offset + count out of range"); 347 return {data() + __offset, __count}; 348 } 349 350 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return _Extent; } 351 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); } 352 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return _Extent == 0; } 353 354 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept { 355 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T, N>::operator[](index): index out of range"); 356 return __data_[__idx]; 357 } 358 359# if _LIBCPP_STD_VER >= 26 360 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const { 361 if (__index >= size()) 362 std::__throw_out_of_range("span"); 363 return __data_[__index]; 364 } 365# endif 366 367 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept { 368 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::front() on empty span"); 369 return __data_[0]; 370 } 371 372 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept { 373 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::back() on empty span"); 374 return __data_[size() - 1]; 375 } 376 377 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; } 378 379 // [span.iter], span iterator support 380 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept { 381# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 382 return std::__make_bounded_iter(data(), data(), data() + size()); 383# else 384 return iterator(data()); 385# endif 386 } 387 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept { 388# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 389 return std::__make_bounded_iter(data() + size(), data(), data() + size()); 390# else 391 return iterator(data() + size()); 392# endif 393 } 394 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 395 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 396 397 _LIBCPP_HIDE_FROM_ABI span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept { 398 return span<const byte, _Extent * sizeof(element_type)>{reinterpret_cast<const byte*>(data()), size_bytes()}; 399 } 400 401 _LIBCPP_HIDE_FROM_ABI span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept { 402 return span<byte, _Extent * sizeof(element_type)>{reinterpret_cast<byte*>(data()), size_bytes()}; 403 } 404 405private: 406 pointer __data_; 407}; 408 409template <typename _Tp> 410class _LIBCPP_TEMPLATE_VIS span<_Tp, dynamic_extent> { 411public: 412 // constants and types 413 using element_type = _Tp; 414 using value_type = remove_cv_t<_Tp>; 415 using size_type = size_t; 416 using difference_type = ptrdiff_t; 417 using pointer = _Tp*; 418 using const_pointer = const _Tp*; 419 using reference = _Tp&; 420 using const_reference = const _Tp&; 421# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 422 using iterator = __bounded_iter<pointer>; 423# else 424 using iterator = __wrap_iter<pointer>; 425# endif 426 using reverse_iterator = std::reverse_iterator<iterator>; 427 428 static constexpr size_type extent = dynamic_extent; 429 430 // [span.cons], span constructors, copy, assignment, and destructor 431 _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr}, __size_{0} {} 432 433# if _LIBCPP_STD_VER >= 26 434 _LIBCPP_HIDE_FROM_ABI constexpr span(std::initializer_list<value_type> __il) 435 requires is_const_v<element_type> 436 : __data_{__il.begin()}, __size_{__il.size()} {} 437# endif 438 439 constexpr span(const span&) noexcept = default; 440 constexpr span& operator=(const span&) noexcept = default; 441 442 template <__span_compatible_iterator<element_type> _It> 443 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, size_type __count) 444 : __data_{std::to_address(__first)}, __size_{__count} {} 445 446 template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End> 447 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, _End __last) 448 : __data_(std::to_address(__first)), __size_(__last - __first) { 449 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__last - __first >= 0, "invalid range in span's constructor (iterator, sentinel)"); 450 } 451 452 template <size_t _Sz> 453 _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Sz]) noexcept 454 : __data_{__arr}, __size_{_Sz} {} 455 456 template <__span_array_convertible<element_type> _OtherElementType, size_t _Sz> 457 _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept 458 : __data_{__arr.data()}, __size_{_Sz} {} 459 460 template <class _OtherElementType, size_t _Sz> 461 requires __span_array_convertible<const _OtherElementType, element_type> 462 _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept 463 : __data_{__arr.data()}, __size_{_Sz} {} 464 465 template <__span_compatible_range<element_type> _Range> 466 _LIBCPP_HIDE_FROM_ABI constexpr span(_Range&& __r) : __data_(ranges::data(__r)), __size_{ranges::size(__r)} {} 467 468 template <__span_array_convertible<element_type> _OtherElementType, size_t _OtherExtent> 469 _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _OtherExtent>& __other) noexcept 470 : __data_{__other.data()}, __size_{__other.size()} {} 471 472 template <size_t _Count> 473 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept { 474 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::first<Count>(): Count out of range"); 475 return span<element_type, _Count>{data(), _Count}; 476 } 477 478 template <size_t _Count> 479 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept { 480 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::last<Count>(): Count out of range"); 481 return span<element_type, _Count>{data() + size() - _Count, _Count}; 482 } 483 484 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept { 485 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::first(count): count out of range"); 486 return {data(), __count}; 487 } 488 489 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept { 490 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::last(count): count out of range"); 491 return {data() + size() - __count, __count}; 492 } 493 494 template <size_t _Offset, size_t _Count = dynamic_extent> 495 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> subspan() const noexcept { 496 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Offset <= size(), "span<T>::subspan<Offset, Count>(): Offset out of range"); 497 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count == dynamic_extent || _Count <= size() - _Offset, 498 "span<T>::subspan<Offset, Count>(): Offset + Count out of range"); 499 return span<element_type, _Count>{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 500 } 501 502 constexpr span<element_type, dynamic_extent> _LIBCPP_HIDE_FROM_ABI 503 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept { 504 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T>::subspan(offset, count): offset out of range"); 505 if (__count == dynamic_extent) 506 return {data() + __offset, size() - __offset}; 507 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 508 __count <= size() - __offset, "span<T>::subspan(offset, count): offset + count out of range"); 509 return {data() + __offset, __count}; 510 } 511 512 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return __size_; } 513 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return __size_ * sizeof(element_type); } 514 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return __size_ == 0; } 515 516 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept { 517 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T>::operator[](index): index out of range"); 518 return __data_[__idx]; 519 } 520 521# if _LIBCPP_STD_VER >= 26 522 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const { 523 if (__index >= size()) 524 std::__throw_out_of_range("span"); 525 return __data_[__index]; 526 } 527# endif 528 529 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept { 530 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::front() on empty span"); 531 return __data_[0]; 532 } 533 534 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept { 535 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::back() on empty span"); 536 return __data_[size() - 1]; 537 } 538 539 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; } 540 541 // [span.iter], span iterator support 542 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept { 543# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 544 return std::__make_bounded_iter(data(), data(), data() + size()); 545# else 546 return iterator(data()); 547# endif 548 } 549 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept { 550# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 551 return std::__make_bounded_iter(data() + size(), data(), data() + size()); 552# else 553 return iterator(data() + size()); 554# endif 555 } 556 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 557 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 558 559 _LIBCPP_HIDE_FROM_ABI span<const byte, dynamic_extent> __as_bytes() const noexcept { 560 return {reinterpret_cast<const byte*>(data()), size_bytes()}; 561 } 562 563 _LIBCPP_HIDE_FROM_ABI span<byte, dynamic_extent> __as_writable_bytes() const noexcept { 564 return {reinterpret_cast<byte*>(data()), size_bytes()}; 565 } 566 567private: 568 pointer __data_; 569 size_type __size_; 570}; 571 572template <class _Tp, size_t _Extent> 573inline constexpr bool ranges::enable_borrowed_range<span<_Tp, _Extent> > = true; 574 575template <class _ElementType, size_t _Extent> 576inline constexpr bool ranges::enable_view<span<_ElementType, _Extent>> = true; 577 578// as_bytes & as_writable_bytes 579template <class _Tp, size_t _Extent> 580_LIBCPP_HIDE_FROM_ABI auto as_bytes(span<_Tp, _Extent> __s) noexcept { 581 return __s.__as_bytes(); 582} 583 584template <class _Tp, size_t _Extent> 585 requires(!is_const_v<_Tp>) 586_LIBCPP_HIDE_FROM_ABI auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept { 587 return __s.__as_writable_bytes(); 588} 589 590# if _LIBCPP_STD_VER >= 26 591template <class _Tp> 592concept __integral_constant_like = 593 is_integral_v<decltype(_Tp::value)> && !is_same_v<bool, remove_const_t<decltype(_Tp::value)>> && 594 convertible_to<_Tp, decltype(_Tp::value)> && equality_comparable_with<_Tp, decltype(_Tp::value)> && 595 bool_constant<_Tp() == _Tp::value>::value && 596 bool_constant<static_cast<decltype(_Tp::value)>(_Tp()) == _Tp::value>::value; 597 598template <class _Tp> 599inline constexpr size_t __maybe_static_ext = dynamic_extent; 600 601template <__integral_constant_like _Tp> 602inline constexpr size_t __maybe_static_ext<_Tp> = {_Tp::value}; 603 604template <contiguous_iterator _It, class _EndOrSize> 605span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>, __maybe_static_ext<_EndOrSize>>; 606# else 607template <contiguous_iterator _It, class _EndOrSize> 608span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>; 609# endif 610 611template <class _Tp, size_t _Sz> 612span(_Tp (&)[_Sz]) -> span<_Tp, _Sz>; 613 614template <class _Tp, size_t _Sz> 615span(array<_Tp, _Sz>&) -> span<_Tp, _Sz>; 616 617template <class _Tp, size_t _Sz> 618span(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>; 619 620template <ranges::contiguous_range _Range> 621span(_Range&&) -> span<remove_reference_t<ranges::range_reference_t<_Range>>>; 622 623#endif // _LIBCPP_STD_VER >= 20 624 625_LIBCPP_END_NAMESPACE_STD 626 627_LIBCPP_POP_MACROS 628 629#if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20 630# include <array> 631# include <concepts> 632# include <functional> 633# include <iterator> 634# include <type_traits> 635#endif 636 637#endif // _LIBCPP_SPAN 638