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 explicit(extent != dynamic_extent) span(std::initializer_list<value_type> il); // Since C++26 72 constexpr span(const span& other) noexcept = default; 73 template <class OtherElementType, size_t OtherExtent> 74 constexpr explicit(Extent != dynamic_extent) span(const span<OtherElementType, OtherExtent>& s) noexcept; 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 at(size_type idx) const; // since C++26 97 constexpr reference front() const; 98 constexpr reference back() const; 99 constexpr pointer data() const noexcept; 100 101 // [span.iterators], span iterator support 102 constexpr iterator begin() const noexcept; 103 constexpr iterator end() const noexcept; 104 constexpr reverse_iterator rbegin() const noexcept; 105 constexpr reverse_iterator rend() const noexcept; 106 107private: 108 pointer data_; // exposition only 109 size_type size_; // exposition only 110}; 111 112template<class It, class EndOrSize> 113 span(It, EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>; 114 115template<class T, size_t N> 116 span(T (&)[N]) -> span<T, N>; 117 118template<class T, size_t N> 119 span(array<T, N>&) -> span<T, N>; 120 121template<class T, size_t N> 122 span(const array<T, N>&) -> span<const T, N>; 123 124template<class R> 125 span(R&&) -> span<remove_reference_t<ranges::range_reference_t<R>>>; 126 127} // namespace std 128 129*/ 130 131#include <__assert> // all public C++ headers provide the assertion handler 132#include <__config> 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 <__type_traits/is_convertible.h> 145#include <__type_traits/remove_cvref.h> 146#include <__type_traits/remove_reference.h> 147#include <__type_traits/type_identity.h> 148#include <__utility/forward.h> 149#include <array> // for array 150#include <cstddef> // for byte 151#include <stdexcept> 152#include <version> 153 154// standard-mandated includes 155 156// [iterator.range] 157#include <__iterator/access.h> 158#include <__iterator/data.h> 159#include <__iterator/empty.h> 160#include <__iterator/reverse_access.h> 161#include <__iterator/size.h> 162 163#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 164# pragma GCC system_header 165#endif 166 167_LIBCPP_PUSH_MACROS 168#include <__undef_macros> 169 170_LIBCPP_BEGIN_NAMESPACE_STD 171 172#if _LIBCPP_STD_VER >= 20 173 174template <class _Tp> 175struct __is_std_array : false_type {}; 176 177template <class _Tp, size_t _Sz> 178struct __is_std_array<array<_Tp, _Sz>> : true_type {}; 179 180template <class _Tp> 181struct __is_std_span : false_type {}; 182 183template <class _Tp, size_t _Sz> 184struct __is_std_span<span<_Tp, _Sz>> : true_type {}; 185 186template <class _Range, class _ElementType> 187concept __span_compatible_range = 188 ranges::contiguous_range<_Range> && // 189 ranges::sized_range<_Range> && // 190 (ranges::borrowed_range<_Range> || is_const_v<_ElementType>)&& // 191 !__is_std_span<remove_cvref_t<_Range>>::value && // 192 !__is_std_array<remove_cvref_t<_Range>>::value && // 193 !is_array_v<remove_cvref_t<_Range>> && // 194 is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>> (*)[], _ElementType (*)[]>; 195 196template <class _From, class _To> 197concept __span_array_convertible = is_convertible_v<_From (*)[], _To (*)[]>; 198 199template <class _It, class _Tp> 200concept __span_compatible_iterator = 201 contiguous_iterator<_It> && __span_array_convertible<remove_reference_t<iter_reference_t<_It>>, _Tp>; 202 203template <class _Sentinel, class _It> 204concept __span_compatible_sentinel_for = sized_sentinel_for<_Sentinel, _It> && !is_convertible_v<_Sentinel, size_t>; 205 206template <typename _Tp, size_t _Extent> 207class _LIBCPP_TEMPLATE_VIS span { 208public: 209 // constants and types 210 using element_type = _Tp; 211 using value_type = remove_cv_t<_Tp>; 212 using size_type = size_t; 213 using difference_type = ptrdiff_t; 214 using pointer = _Tp*; 215 using const_pointer = const _Tp*; 216 using reference = _Tp&; 217 using const_reference = const _Tp&; 218# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 219 using iterator = __bounded_iter<pointer>; 220# else 221 using iterator = __wrap_iter<pointer>; 222# endif 223 using reverse_iterator = std::reverse_iterator<iterator>; 224 225 static constexpr size_type extent = _Extent; 226 227 // [span.cons], span constructors, copy, assignment, and destructor 228 template <size_t _Sz = _Extent> 229 requires(_Sz == 0) 230 _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr} {} 231 232# if _LIBCPP_STD_VER >= 26 233 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(std::initializer_list<value_type> __il) 234 requires is_const_v<element_type> 235 : __data_{__il.begin()} { 236 _LIBCPP_ASSERT_VALID_INPUT_RANGE( 237 _Extent == __il.size(), "Size mismatch in span's constructor _Extent != __il.size()."); 238 } 239# endif 240 241 constexpr span(const span&) noexcept = default; 242 constexpr span& operator=(const span&) noexcept = default; 243 244 template <__span_compatible_iterator<element_type> _It> 245 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, size_type __count) : __data_{std::to_address(__first)} { 246 (void)__count; 247 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __count, "size mismatch in span's constructor (iterator, len)"); 248 } 249 250 template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End> 251 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, _End __last) : __data_{std::to_address(__first)} { 252 // [span.cons]/10 253 // Throws: When and what last - first throws. 254 [[maybe_unused]] auto __dist = __last - __first; 255 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__dist >= 0, "invalid range in span's constructor (iterator, sentinel)"); 256 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 257 __dist == _Extent, "invalid range in span's constructor (iterator, sentinel): last - first != extent"); 258 } 259 260 _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Extent]) noexcept : __data_{__arr} {} 261 262 template <__span_array_convertible<element_type> _OtherElementType> 263 _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Extent>& __arr) noexcept : __data_{__arr.data()} {} 264 265 template <class _OtherElementType> 266 requires __span_array_convertible<const _OtherElementType, element_type> 267 _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Extent>& __arr) noexcept 268 : __data_{__arr.data()} {} 269 270 template <__span_compatible_range<element_type> _Range> 271 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_Range&& __r) : __data_{ranges::data(__r)} { 272 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(ranges::size(__r) == _Extent, "size mismatch in span's constructor (range)"); 273 } 274 275 template <__span_array_convertible<element_type> _OtherElementType> 276 _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _Extent>& __other) : __data_{__other.data()} {} 277 278 template <__span_array_convertible<element_type> _OtherElementType> 279 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(const span<_OtherElementType, dynamic_extent>& __other) noexcept 280 : __data_{__other.data()} { 281 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __other.size(), "size mismatch in span's constructor (other span)"); 282 } 283 284 template <size_t _Count> 285 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept { 286 static_assert(_Count <= _Extent, "span<T, N>::first<Count>(): Count out of range"); 287 return span<element_type, _Count>{data(), _Count}; 288 } 289 290 template <size_t _Count> 291 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept { 292 static_assert(_Count <= _Extent, "span<T, N>::last<Count>(): Count out of range"); 293 return span<element_type, _Count>{data() + size() - _Count, _Count}; 294 } 295 296 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept { 297 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::first(count): count out of range"); 298 return {data(), __count}; 299 } 300 301 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept { 302 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::last(count): count out of range"); 303 return {data() + size() - __count, __count}; 304 } 305 306 template <size_t _Offset, size_t _Count = dynamic_extent> 307 _LIBCPP_HIDE_FROM_ABI constexpr auto subspan() const noexcept 308 -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset> { 309 static_assert(_Offset <= _Extent, "span<T, N>::subspan<Offset, Count>(): Offset out of range"); 310 static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset, 311 "span<T, N>::subspan<Offset, Count>(): Offset + Count out of range"); 312 313 using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>; 314 return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 315 } 316 317 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> 318 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept { 319 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T, N>::subspan(offset, count): offset out of range"); 320 if (__count == dynamic_extent) 321 return {data() + __offset, size() - __offset}; 322 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 323 __count <= size() - __offset, "span<T, N>::subspan(offset, count): offset + count out of range"); 324 return {data() + __offset, __count}; 325 } 326 327 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return _Extent; } 328 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); } 329 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return _Extent == 0; } 330 331 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept { 332 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T, N>::operator[](index): index out of range"); 333 return __data_[__idx]; 334 } 335 336# if _LIBCPP_STD_VER >= 26 337 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const { 338 if (__index >= size()) 339 std::__throw_out_of_range("span"); 340 return __data_[__index]; 341 } 342# endif 343 344 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept { 345 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::front() on empty span"); 346 return __data_[0]; 347 } 348 349 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept { 350 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::back() on empty span"); 351 return __data_[size() - 1]; 352 } 353 354 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; } 355 356 // [span.iter], span iterator support 357 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept { 358# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 359 return std::__make_bounded_iter(data(), data(), data() + size()); 360# else 361 return iterator(data()); 362# endif 363 } 364 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept { 365# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 366 return std::__make_bounded_iter(data() + size(), data(), data() + size()); 367# else 368 return iterator(data() + size()); 369# endif 370 } 371 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 372 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 373 374 _LIBCPP_HIDE_FROM_ABI 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 } 377 378 _LIBCPP_HIDE_FROM_ABI span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept { 379 return span<byte, _Extent * sizeof(element_type)>{reinterpret_cast<byte*>(data()), size_bytes()}; 380 } 381 382private: 383 pointer __data_; 384}; 385 386template <typename _Tp> 387class _LIBCPP_TEMPLATE_VIS span<_Tp, dynamic_extent> { 388public: 389 // constants and types 390 using element_type = _Tp; 391 using value_type = remove_cv_t<_Tp>; 392 using size_type = size_t; 393 using difference_type = ptrdiff_t; 394 using pointer = _Tp*; 395 using const_pointer = const _Tp*; 396 using reference = _Tp&; 397 using const_reference = const _Tp&; 398# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 399 using iterator = __bounded_iter<pointer>; 400# else 401 using iterator = __wrap_iter<pointer>; 402# endif 403 using reverse_iterator = std::reverse_iterator<iterator>; 404 405 static constexpr size_type extent = dynamic_extent; 406 407 // [span.cons], span constructors, copy, assignment, and destructor 408 _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr}, __size_{0} {} 409 410# if _LIBCPP_STD_VER >= 26 411 _LIBCPP_HIDE_FROM_ABI constexpr span(std::initializer_list<value_type> __il) 412 requires is_const_v<element_type> 413 : __data_{__il.begin()}, __size_{__il.size()} {} 414# endif 415 416 constexpr span(const span&) noexcept = default; 417 constexpr span& operator=(const span&) noexcept = default; 418 419 template <__span_compatible_iterator<element_type> _It> 420 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, size_type __count) 421 : __data_{std::to_address(__first)}, __size_{__count} {} 422 423 template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End> 424 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, _End __last) 425 : __data_(std::to_address(__first)), __size_(__last - __first) { 426 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__last - __first >= 0, "invalid range in span's constructor (iterator, sentinel)"); 427 } 428 429 template <size_t _Sz> 430 _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Sz]) noexcept 431 : __data_{__arr}, __size_{_Sz} {} 432 433 template <__span_array_convertible<element_type> _OtherElementType, size_t _Sz> 434 _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept 435 : __data_{__arr.data()}, __size_{_Sz} {} 436 437 template <class _OtherElementType, size_t _Sz> 438 requires __span_array_convertible<const _OtherElementType, element_type> 439 _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept 440 : __data_{__arr.data()}, __size_{_Sz} {} 441 442 template <__span_compatible_range<element_type> _Range> 443 _LIBCPP_HIDE_FROM_ABI constexpr span(_Range&& __r) : __data_(ranges::data(__r)), __size_{ranges::size(__r)} {} 444 445 template <__span_array_convertible<element_type> _OtherElementType, size_t _OtherExtent> 446 _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _OtherExtent>& __other) noexcept 447 : __data_{__other.data()}, __size_{__other.size()} {} 448 449 template <size_t _Count> 450 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept { 451 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_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_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept { 457 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::last<Count>(): Count out of range"); 458 return span<element_type, _Count>{data() + size() - _Count, _Count}; 459 } 460 461 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept { 462 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::first(count): count out of range"); 463 return {data(), __count}; 464 } 465 466 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept { 467 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::last(count): count out of range"); 468 return {data() + size() - __count, __count}; 469 } 470 471 template <size_t _Offset, size_t _Count = dynamic_extent> 472 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> subspan() const noexcept { 473 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Offset <= size(), "span<T>::subspan<Offset, Count>(): Offset out of range"); 474 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count == dynamic_extent || _Count <= size() - _Offset, 475 "span<T>::subspan<Offset, Count>(): Offset + Count out of range"); 476 return span<element_type, _Count>{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 477 } 478 479 constexpr span<element_type, dynamic_extent> _LIBCPP_HIDE_FROM_ABI 480 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept { 481 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T>::subspan(offset, count): offset out of range"); 482 if (__count == dynamic_extent) 483 return {data() + __offset, size() - __offset}; 484 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 485 __count <= size() - __offset, "span<T>::subspan(offset, count): offset + count out of range"); 486 return {data() + __offset, __count}; 487 } 488 489 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return __size_; } 490 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return __size_ * sizeof(element_type); } 491 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return __size_ == 0; } 492 493 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept { 494 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T>::operator[](index): index out of range"); 495 return __data_[__idx]; 496 } 497 498# if _LIBCPP_STD_VER >= 26 499 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const { 500 if (__index >= size()) 501 std::__throw_out_of_range("span"); 502 return __data_[__index]; 503 } 504# endif 505 506 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept { 507 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::front() on empty span"); 508 return __data_[0]; 509 } 510 511 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept { 512 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::back() on empty span"); 513 return __data_[size() - 1]; 514 } 515 516 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; } 517 518 // [span.iter], span iterator support 519 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept { 520# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 521 return std::__make_bounded_iter(data(), data(), data() + size()); 522# else 523 return iterator(data()); 524# endif 525 } 526 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept { 527# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 528 return std::__make_bounded_iter(data() + size(), data(), data() + size()); 529# else 530 return iterator(data() + size()); 531# endif 532 } 533 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 534 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 535 536 _LIBCPP_HIDE_FROM_ABI span<const byte, dynamic_extent> __as_bytes() const noexcept { 537 return {reinterpret_cast<const byte*>(data()), size_bytes()}; 538 } 539 540 _LIBCPP_HIDE_FROM_ABI span<byte, dynamic_extent> __as_writable_bytes() const noexcept { 541 return {reinterpret_cast<byte*>(data()), size_bytes()}; 542 } 543 544private: 545 pointer __data_; 546 size_type __size_; 547}; 548 549template <class _Tp, size_t _Extent> 550inline constexpr bool ranges::enable_borrowed_range<span<_Tp, _Extent> > = true; 551 552template <class _ElementType, size_t _Extent> 553inline constexpr bool ranges::enable_view<span<_ElementType, _Extent>> = true; 554 555// as_bytes & as_writable_bytes 556template <class _Tp, size_t _Extent> 557_LIBCPP_HIDE_FROM_ABI auto as_bytes(span<_Tp, _Extent> __s) noexcept { 558 return __s.__as_bytes(); 559} 560 561template <class _Tp, size_t _Extent> 562 requires(!is_const_v<_Tp>) 563_LIBCPP_HIDE_FROM_ABI auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept { 564 return __s.__as_writable_bytes(); 565} 566 567# if _LIBCPP_STD_VER >= 20 568template <contiguous_iterator _It, class _EndOrSize> 569span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>; 570# endif // _LIBCPP_STD_VER >= 20 571 572template <class _Tp, size_t _Sz> 573span(_Tp (&)[_Sz]) -> span<_Tp, _Sz>; 574 575template <class _Tp, size_t _Sz> 576span(array<_Tp, _Sz>&) -> span<_Tp, _Sz>; 577 578template <class _Tp, size_t _Sz> 579span(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>; 580 581template <ranges::contiguous_range _Range> 582span(_Range&&) -> span<remove_reference_t<ranges::range_reference_t<_Range>>>; 583 584#endif // _LIBCPP_STD_VER >= 20 585 586_LIBCPP_END_NAMESPACE_STD 587 588_LIBCPP_POP_MACROS 589 590#if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20 591# include <concepts> 592# include <functional> 593# include <iterator> 594# include <type_traits> 595#endif 596 597#endif // _LIBCPP_SPAN 598