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