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#if __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS) 148# include <__cxx03/span> 149#else 150# include <__assert> 151# include <__concepts/convertible_to.h> 152# include <__concepts/equality_comparable.h> 153# include <__config> 154# include <__cstddef/byte.h> 155# include <__cstddef/ptrdiff_t.h> 156# include <__fwd/array.h> 157# include <__fwd/span.h> 158# include <__iterator/bounded_iter.h> 159# include <__iterator/concepts.h> 160# include <__iterator/iterator_traits.h> 161# include <__iterator/reverse_iterator.h> 162# include <__iterator/wrap_iter.h> 163# include <__memory/pointer_traits.h> 164# include <__ranges/concepts.h> 165# include <__ranges/data.h> 166# include <__ranges/enable_borrowed_range.h> 167# include <__ranges/enable_view.h> 168# include <__ranges/size.h> 169# include <__type_traits/integral_constant.h> 170# include <__type_traits/is_array.h> 171# include <__type_traits/is_const.h> 172# include <__type_traits/is_convertible.h> 173# include <__type_traits/is_integral.h> 174# include <__type_traits/is_same.h> 175# include <__type_traits/remove_const.h> 176# include <__type_traits/remove_cv.h> 177# include <__type_traits/remove_cvref.h> 178# include <__type_traits/remove_reference.h> 179# include <__type_traits/type_identity.h> 180# include <__utility/forward.h> 181# include <initializer_list> 182# include <stdexcept> 183# include <version> 184 185// standard-mandated includes 186 187// [iterator.range] 188# include <__iterator/access.h> 189# include <__iterator/data.h> 190# include <__iterator/empty.h> 191# include <__iterator/reverse_access.h> 192# include <__iterator/size.h> 193 194# if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 195# pragma GCC system_header 196# endif 197 198_LIBCPP_PUSH_MACROS 199# include <__undef_macros> 200 201_LIBCPP_BEGIN_NAMESPACE_STD 202 203# if _LIBCPP_STD_VER >= 20 204 205template <class _Tp> 206struct __is_std_span : false_type {}; 207 208template <class _Tp, size_t _Sz> 209struct __is_std_span<span<_Tp, _Sz>> : true_type {}; 210 211template <class _Range, class _ElementType> 212concept __span_compatible_range = 213 !__is_std_span<remove_cvref_t<_Range>>::value && // 214 ranges::contiguous_range<_Range> && // 215 ranges::sized_range<_Range> && // 216 (ranges::borrowed_range<_Range> || is_const_v<_ElementType>) && // 217 !__is_std_array_v<remove_cvref_t<_Range>> && // 218 !is_array_v<remove_cvref_t<_Range>> && // 219 is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>> (*)[], _ElementType (*)[]>; 220 221template <class _From, class _To> 222concept __span_array_convertible = is_convertible_v<_From (*)[], _To (*)[]>; 223 224template <class _It, class _Tp> 225concept __span_compatible_iterator = 226 contiguous_iterator<_It> && __span_array_convertible<remove_reference_t<iter_reference_t<_It>>, _Tp>; 227 228template <class _Sentinel, class _It> 229concept __span_compatible_sentinel_for = sized_sentinel_for<_Sentinel, _It> && !is_convertible_v<_Sentinel, size_t>; 230 231template <typename _Tp, size_t _Extent> 232class _LIBCPP_TEMPLATE_VIS span { 233public: 234 // constants and types 235 using element_type = _Tp; 236 using value_type = remove_cv_t<_Tp>; 237 using size_type = size_t; 238 using difference_type = ptrdiff_t; 239 using pointer = _Tp*; 240 using const_pointer = const _Tp*; 241 using reference = _Tp&; 242 using const_reference = const _Tp&; 243# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 244 using iterator = __bounded_iter<pointer>; 245# else 246 using iterator = __wrap_iter<pointer>; 247# endif 248 using reverse_iterator = std::reverse_iterator<iterator>; 249 250 static constexpr size_type extent = _Extent; 251 252 // [span.cons], span constructors, copy, assignment, and destructor 253 template <size_t _Sz = _Extent> 254 requires(_Sz == 0) 255 _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr} {} 256 257# if _LIBCPP_STD_VER >= 26 258 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(std::initializer_list<value_type> __il) 259 requires is_const_v<element_type> 260 : __data_{__il.begin()} { 261 _LIBCPP_ASSERT_VALID_INPUT_RANGE( 262 _Extent == __il.size(), "Size mismatch in span's constructor _Extent != __il.size()."); 263 } 264# endif 265 266 constexpr span(const span&) noexcept = default; 267 constexpr span& operator=(const span&) noexcept = default; 268 269 template <__span_compatible_iterator<element_type> _It> 270 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, size_type __count) : __data_{std::to_address(__first)} { 271 (void)__count; 272 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __count, "size mismatch in span's constructor (iterator, len)"); 273 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__count == 0 || std::to_address(__first) != nullptr, 274 "passed nullptr with non-zero length in span's constructor (iterator, len)"); 275 } 276 277 template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End> 278 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_It __first, _End __last) : __data_{std::to_address(__first)} { 279 // [span.cons]/10 280 // Throws: When and what last - first throws. 281 [[maybe_unused]] auto __dist = __last - __first; 282 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__dist >= 0, "invalid range in span's constructor (iterator, sentinel)"); 283 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 284 __dist == _Extent, "invalid range in span's constructor (iterator, sentinel): last - first != extent"); 285 } 286 287 _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Extent]) noexcept : __data_{__arr} {} 288 289 template <__span_array_convertible<element_type> _OtherElementType> 290 _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Extent>& __arr) noexcept : __data_{__arr.data()} {} 291 292 template <class _OtherElementType> 293 requires __span_array_convertible<const _OtherElementType, element_type> 294 _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Extent>& __arr) noexcept 295 : __data_{__arr.data()} {} 296 297 template <__span_compatible_range<element_type> _Range> 298 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(_Range&& __r) : __data_{ranges::data(__r)} { 299 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(ranges::size(__r) == _Extent, "size mismatch in span's constructor (range)"); 300 } 301 302 template <__span_array_convertible<element_type> _OtherElementType> 303 _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _Extent>& __other) noexcept 304 : __data_{__other.data()} {} 305 306 template <__span_array_convertible<element_type> _OtherElementType> 307 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(const span<_OtherElementType, dynamic_extent>& __other) noexcept 308 : __data_{__other.data()} { 309 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __other.size(), "size mismatch in span's constructor (other span)"); 310 } 311 312 template <size_t _Count> 313 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept { 314 static_assert(_Count <= _Extent, "span<T, N>::first<Count>(): Count out of range"); 315 return span<element_type, _Count>{data(), _Count}; 316 } 317 318 template <size_t _Count> 319 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept { 320 static_assert(_Count <= _Extent, "span<T, N>::last<Count>(): Count out of range"); 321 return span<element_type, _Count>{data() + size() - _Count, _Count}; 322 } 323 324 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept { 325 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::first(count): count out of range"); 326 return {data(), __count}; 327 } 328 329 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept { 330 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::last(count): count out of range"); 331 return {data() + size() - __count, __count}; 332 } 333 334 template <size_t _Offset, size_t _Count = dynamic_extent> 335 _LIBCPP_HIDE_FROM_ABI constexpr auto 336 subspan() const noexcept -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset> { 337 static_assert(_Offset <= _Extent, "span<T, N>::subspan<Offset, Count>(): Offset out of range"); 338 static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset, 339 "span<T, N>::subspan<Offset, Count>(): Offset + Count out of range"); 340 341 using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>; 342 return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 343 } 344 345 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> 346 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept { 347 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T, N>::subspan(offset, count): offset out of range"); 348 if (__count == dynamic_extent) 349 return {data() + __offset, size() - __offset}; 350 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 351 __count <= size() - __offset, "span<T, N>::subspan(offset, count): offset + count out of range"); 352 return {data() + __offset, __count}; 353 } 354 355 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return _Extent; } 356 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); } 357 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return _Extent == 0; } 358 359 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept { 360 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T, N>::operator[](index): index out of range"); 361 return __data_[__idx]; 362 } 363 364# if _LIBCPP_STD_VER >= 26 365 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const { 366 if (__index >= size()) 367 std::__throw_out_of_range("span"); 368 return __data_[__index]; 369 } 370# endif 371 372 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept { 373 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::front() on empty span"); 374 return __data_[0]; 375 } 376 377 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept { 378 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::back() on empty span"); 379 return __data_[size() - 1]; 380 } 381 382 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; } 383 384 // [span.iter], span iterator support 385 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept { 386# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 387 return std::__make_bounded_iter(data(), data(), data() + size()); 388# else 389 return iterator(data()); 390# endif 391 } 392 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept { 393# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 394 return std::__make_bounded_iter(data() + size(), data(), data() + size()); 395# else 396 return iterator(data() + size()); 397# endif 398 } 399 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 400 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 401 402 _LIBCPP_HIDE_FROM_ABI span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept { 403 return span<const byte, _Extent * sizeof(element_type)>{reinterpret_cast<const byte*>(data()), size_bytes()}; 404 } 405 406 _LIBCPP_HIDE_FROM_ABI span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept { 407 return span<byte, _Extent * sizeof(element_type)>{reinterpret_cast<byte*>(data()), size_bytes()}; 408 } 409 410private: 411 pointer __data_; 412}; 413 414template <typename _Tp> 415class _LIBCPP_TEMPLATE_VIS span<_Tp, dynamic_extent> { 416public: 417 // constants and types 418 using element_type = _Tp; 419 using value_type = remove_cv_t<_Tp>; 420 using size_type = size_t; 421 using difference_type = ptrdiff_t; 422 using pointer = _Tp*; 423 using const_pointer = const _Tp*; 424 using reference = _Tp&; 425 using const_reference = const _Tp&; 426# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 427 using iterator = __bounded_iter<pointer>; 428# else 429 using iterator = __wrap_iter<pointer>; 430# endif 431 using reverse_iterator = std::reverse_iterator<iterator>; 432 433 static constexpr size_type extent = dynamic_extent; 434 435 // [span.cons], span constructors, copy, assignment, and destructor 436 _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr}, __size_{0} {} 437 438# if _LIBCPP_STD_VER >= 26 439 _LIBCPP_HIDE_FROM_ABI constexpr span(std::initializer_list<value_type> __il) 440 requires is_const_v<element_type> 441 : __data_{__il.begin()}, __size_{__il.size()} {} 442# endif 443 444 constexpr span(const span&) noexcept = default; 445 constexpr span& operator=(const span&) noexcept = default; 446 447 template <__span_compatible_iterator<element_type> _It> 448 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, size_type __count) 449 : __data_{std::to_address(__first)}, __size_{__count} { 450 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__count == 0 || std::to_address(__first) != nullptr, 451 "passed nullptr with non-zero length in span's constructor (iterator, len)"); 452 } 453 454 template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End> 455 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, _End __last) 456 : __data_(std::to_address(__first)), __size_(__last - __first) { 457 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__last - __first >= 0, "invalid range in span's constructor (iterator, sentinel)"); 458 } 459 460 template <size_t _Sz> 461 _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Sz]) noexcept 462 : __data_{__arr}, __size_{_Sz} {} 463 464 template <__span_array_convertible<element_type> _OtherElementType, size_t _Sz> 465 _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept 466 : __data_{__arr.data()}, __size_{_Sz} {} 467 468 template <class _OtherElementType, size_t _Sz> 469 requires __span_array_convertible<const _OtherElementType, element_type> 470 _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept 471 : __data_{__arr.data()}, __size_{_Sz} {} 472 473 template <__span_compatible_range<element_type> _Range> 474 _LIBCPP_HIDE_FROM_ABI constexpr span(_Range&& __r) : __data_(ranges::data(__r)), __size_{ranges::size(__r)} {} 475 476 template <__span_array_convertible<element_type> _OtherElementType, size_t _OtherExtent> 477 _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _OtherExtent>& __other) noexcept 478 : __data_{__other.data()}, __size_{__other.size()} {} 479 480 template <size_t _Count> 481 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept { 482 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::first<Count>(): Count out of range"); 483 return span<element_type, _Count>{data(), _Count}; 484 } 485 486 template <size_t _Count> 487 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept { 488 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::last<Count>(): Count out of range"); 489 return span<element_type, _Count>{data() + size() - _Count, _Count}; 490 } 491 492 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept { 493 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::first(count): count out of range"); 494 return {data(), __count}; 495 } 496 497 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept { 498 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::last(count): count out of range"); 499 return {data() + size() - __count, __count}; 500 } 501 502 template <size_t _Offset, size_t _Count = dynamic_extent> 503 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> subspan() const noexcept { 504 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Offset <= size(), "span<T>::subspan<Offset, Count>(): Offset out of range"); 505 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count == dynamic_extent || _Count <= size() - _Offset, 506 "span<T>::subspan<Offset, Count>(): Offset + Count out of range"); 507 return span<element_type, _Count>{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 508 } 509 510 constexpr span<element_type, dynamic_extent> _LIBCPP_HIDE_FROM_ABI 511 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept { 512 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T>::subspan(offset, count): offset out of range"); 513 if (__count == dynamic_extent) 514 return {data() + __offset, size() - __offset}; 515 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 516 __count <= size() - __offset, "span<T>::subspan(offset, count): offset + count out of range"); 517 return {data() + __offset, __count}; 518 } 519 520 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return __size_; } 521 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return __size_ * sizeof(element_type); } 522 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return __size_ == 0; } 523 524 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept { 525 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T>::operator[](index): index out of range"); 526 return __data_[__idx]; 527 } 528 529# if _LIBCPP_STD_VER >= 26 530 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const { 531 if (__index >= size()) 532 std::__throw_out_of_range("span"); 533 return __data_[__index]; 534 } 535# endif 536 537 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept { 538 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::front() on empty span"); 539 return __data_[0]; 540 } 541 542 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept { 543 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::back() on empty span"); 544 return __data_[size() - 1]; 545 } 546 547 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; } 548 549 // [span.iter], span iterator support 550 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept { 551# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 552 return std::__make_bounded_iter(data(), data(), data() + size()); 553# else 554 return iterator(data()); 555# endif 556 } 557 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept { 558# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 559 return std::__make_bounded_iter(data() + size(), data(), data() + size()); 560# else 561 return iterator(data() + size()); 562# endif 563 } 564 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 565 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 566 567 _LIBCPP_HIDE_FROM_ABI span<const byte, dynamic_extent> __as_bytes() const noexcept { 568 return {reinterpret_cast<const byte*>(data()), size_bytes()}; 569 } 570 571 _LIBCPP_HIDE_FROM_ABI span<byte, dynamic_extent> __as_writable_bytes() const noexcept { 572 return {reinterpret_cast<byte*>(data()), size_bytes()}; 573 } 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_HIDE_FROM_ABI auto as_bytes(span<_Tp, _Extent> __s) noexcept { 589 return __s.__as_bytes(); 590} 591 592template <class _Tp, size_t _Extent> 593 requires(!is_const_v<_Tp>) 594_LIBCPP_HIDE_FROM_ABI auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept { 595 return __s.__as_writable_bytes(); 596} 597 598# if _LIBCPP_STD_VER >= 26 599template <class _Tp> 600concept __integral_constant_like = 601 is_integral_v<decltype(_Tp::value)> && !is_same_v<bool, remove_const_t<decltype(_Tp::value)>> && 602 convertible_to<_Tp, decltype(_Tp::value)> && equality_comparable_with<_Tp, decltype(_Tp::value)> && 603 bool_constant<_Tp() == _Tp::value>::value && 604 bool_constant<static_cast<decltype(_Tp::value)>(_Tp()) == _Tp::value>::value; 605 606template <class _Tp> 607inline constexpr size_t __maybe_static_ext = dynamic_extent; 608 609template <__integral_constant_like _Tp> 610inline constexpr size_t __maybe_static_ext<_Tp> = {_Tp::value}; 611 612template <contiguous_iterator _It, class _EndOrSize> 613span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>, __maybe_static_ext<_EndOrSize>>; 614# else 615template <contiguous_iterator _It, class _EndOrSize> 616span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>; 617# endif 618 619template <class _Tp, size_t _Sz> 620span(_Tp (&)[_Sz]) -> span<_Tp, _Sz>; 621 622template <class _Tp, size_t _Sz> 623span(array<_Tp, _Sz>&) -> span<_Tp, _Sz>; 624 625template <class _Tp, size_t _Sz> 626span(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>; 627 628template <ranges::contiguous_range _Range> 629span(_Range&&) -> span<remove_reference_t<ranges::range_reference_t<_Range>>>; 630 631# endif // _LIBCPP_STD_VER >= 20 632 633_LIBCPP_END_NAMESPACE_STD 634 635_LIBCPP_POP_MACROS 636 637# if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20 638# include <array> 639# include <concepts> 640# include <functional> 641# include <iterator> 642# include <type_traits> 643# endif 644#endif // __cplusplus < 201103L && defined(_LIBCPP_USE_FROZEN_CXX03_HEADERS) 645 646#endif // _LIBCPP_SPAN 647