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 !__is_std_span<remove_cvref_t<_Range>>::value && // 210 ranges::contiguous_range<_Range> && // 211 ranges::sized_range<_Range> && // 212 (ranges::borrowed_range<_Range> || is_const_v<_ElementType>) && // 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) noexcept 298 : __data_{__other.data()} {} 299 300 template <__span_array_convertible<element_type> _OtherElementType> 301 _LIBCPP_HIDE_FROM_ABI constexpr explicit span(const span<_OtherElementType, dynamic_extent>& __other) noexcept 302 : __data_{__other.data()} { 303 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Extent == __other.size(), "size mismatch in span's constructor (other span)"); 304 } 305 306 template <size_t _Count> 307 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept { 308 static_assert(_Count <= _Extent, "span<T, N>::first<Count>(): Count out of range"); 309 return span<element_type, _Count>{data(), _Count}; 310 } 311 312 template <size_t _Count> 313 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept { 314 static_assert(_Count <= _Extent, "span<T, N>::last<Count>(): Count out of range"); 315 return span<element_type, _Count>{data() + size() - _Count, _Count}; 316 } 317 318 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept { 319 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::first(count): count out of range"); 320 return {data(), __count}; 321 } 322 323 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept { 324 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T, N>::last(count): count out of range"); 325 return {data() + size() - __count, __count}; 326 } 327 328 template <size_t _Offset, size_t _Count = dynamic_extent> 329 _LIBCPP_HIDE_FROM_ABI constexpr auto 330 subspan() const noexcept -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset> { 331 static_assert(_Offset <= _Extent, "span<T, N>::subspan<Offset, Count>(): Offset out of range"); 332 static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset, 333 "span<T, N>::subspan<Offset, Count>(): Offset + Count out of range"); 334 335 using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>; 336 return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 337 } 338 339 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> 340 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept { 341 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T, N>::subspan(offset, count): offset out of range"); 342 if (__count == dynamic_extent) 343 return {data() + __offset, size() - __offset}; 344 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 345 __count <= size() - __offset, "span<T, N>::subspan(offset, count): offset + count out of range"); 346 return {data() + __offset, __count}; 347 } 348 349 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return _Extent; } 350 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); } 351 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return _Extent == 0; } 352 353 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept { 354 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T, N>::operator[](index): index out of range"); 355 return __data_[__idx]; 356 } 357 358# if _LIBCPP_STD_VER >= 26 359 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const { 360 if (__index >= size()) 361 std::__throw_out_of_range("span"); 362 return __data_[__index]; 363 } 364# endif 365 366 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept { 367 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::front() on empty span"); 368 return __data_[0]; 369 } 370 371 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept { 372 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T, N>::back() on empty span"); 373 return __data_[size() - 1]; 374 } 375 376 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; } 377 378 // [span.iter], span iterator support 379 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept { 380# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 381 return std::__make_bounded_iter(data(), data(), data() + size()); 382# else 383 return iterator(data()); 384# endif 385 } 386 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept { 387# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 388 return std::__make_bounded_iter(data() + size(), data(), data() + size()); 389# else 390 return iterator(data() + size()); 391# endif 392 } 393 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 394 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 395 396 _LIBCPP_HIDE_FROM_ABI span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept { 397 return span<const byte, _Extent * sizeof(element_type)>{reinterpret_cast<const byte*>(data()), size_bytes()}; 398 } 399 400 _LIBCPP_HIDE_FROM_ABI span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept { 401 return span<byte, _Extent * sizeof(element_type)>{reinterpret_cast<byte*>(data()), size_bytes()}; 402 } 403 404private: 405 pointer __data_; 406}; 407 408template <typename _Tp> 409class _LIBCPP_TEMPLATE_VIS span<_Tp, dynamic_extent> { 410public: 411 // constants and types 412 using element_type = _Tp; 413 using value_type = remove_cv_t<_Tp>; 414 using size_type = size_t; 415 using difference_type = ptrdiff_t; 416 using pointer = _Tp*; 417 using const_pointer = const _Tp*; 418 using reference = _Tp&; 419 using const_reference = const _Tp&; 420# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 421 using iterator = __bounded_iter<pointer>; 422# else 423 using iterator = __wrap_iter<pointer>; 424# endif 425 using reverse_iterator = std::reverse_iterator<iterator>; 426 427 static constexpr size_type extent = dynamic_extent; 428 429 // [span.cons], span constructors, copy, assignment, and destructor 430 _LIBCPP_HIDE_FROM_ABI constexpr span() noexcept : __data_{nullptr}, __size_{0} {} 431 432# if _LIBCPP_STD_VER >= 26 433 _LIBCPP_HIDE_FROM_ABI constexpr span(std::initializer_list<value_type> __il) 434 requires is_const_v<element_type> 435 : __data_{__il.begin()}, __size_{__il.size()} {} 436# endif 437 438 constexpr span(const span&) noexcept = default; 439 constexpr span& operator=(const span&) noexcept = default; 440 441 template <__span_compatible_iterator<element_type> _It> 442 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, size_type __count) 443 : __data_{std::to_address(__first)}, __size_{__count} {} 444 445 template <__span_compatible_iterator<element_type> _It, __span_compatible_sentinel_for<_It> _End> 446 _LIBCPP_HIDE_FROM_ABI constexpr span(_It __first, _End __last) 447 : __data_(std::to_address(__first)), __size_(__last - __first) { 448 _LIBCPP_ASSERT_VALID_INPUT_RANGE(__last - __first >= 0, "invalid range in span's constructor (iterator, sentinel)"); 449 } 450 451 template <size_t _Sz> 452 _LIBCPP_HIDE_FROM_ABI constexpr span(type_identity_t<element_type> (&__arr)[_Sz]) noexcept 453 : __data_{__arr}, __size_{_Sz} {} 454 455 template <__span_array_convertible<element_type> _OtherElementType, size_t _Sz> 456 _LIBCPP_HIDE_FROM_ABI constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept 457 : __data_{__arr.data()}, __size_{_Sz} {} 458 459 template <class _OtherElementType, size_t _Sz> 460 requires __span_array_convertible<const _OtherElementType, element_type> 461 _LIBCPP_HIDE_FROM_ABI constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept 462 : __data_{__arr.data()}, __size_{_Sz} {} 463 464 template <__span_compatible_range<element_type> _Range> 465 _LIBCPP_HIDE_FROM_ABI constexpr span(_Range&& __r) : __data_(ranges::data(__r)), __size_{ranges::size(__r)} {} 466 467 template <__span_array_convertible<element_type> _OtherElementType, size_t _OtherExtent> 468 _LIBCPP_HIDE_FROM_ABI constexpr span(const span<_OtherElementType, _OtherExtent>& __other) noexcept 469 : __data_{__other.data()}, __size_{__other.size()} {} 470 471 template <size_t _Count> 472 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> first() const noexcept { 473 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::first<Count>(): Count out of range"); 474 return span<element_type, _Count>{data(), _Count}; 475 } 476 477 template <size_t _Count> 478 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> last() const noexcept { 479 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count <= size(), "span<T>::last<Count>(): Count out of range"); 480 return span<element_type, _Count>{data() + size() - _Count, _Count}; 481 } 482 483 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept { 484 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::first(count): count out of range"); 485 return {data(), __count}; 486 } 487 488 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept { 489 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__count <= size(), "span<T>::last(count): count out of range"); 490 return {data() + size() - __count, __count}; 491 } 492 493 template <size_t _Offset, size_t _Count = dynamic_extent> 494 _LIBCPP_HIDE_FROM_ABI constexpr span<element_type, _Count> subspan() const noexcept { 495 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Offset <= size(), "span<T>::subspan<Offset, Count>(): Offset out of range"); 496 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(_Count == dynamic_extent || _Count <= size() - _Offset, 497 "span<T>::subspan<Offset, Count>(): Offset + Count out of range"); 498 return span<element_type, _Count>{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 499 } 500 501 constexpr span<element_type, dynamic_extent> _LIBCPP_HIDE_FROM_ABI 502 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept { 503 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__offset <= size(), "span<T>::subspan(offset, count): offset out of range"); 504 if (__count == dynamic_extent) 505 return {data() + __offset, size() - __offset}; 506 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS( 507 __count <= size() - __offset, "span<T>::subspan(offset, count): offset + count out of range"); 508 return {data() + __offset, __count}; 509 } 510 511 _LIBCPP_HIDE_FROM_ABI constexpr size_type size() const noexcept { return __size_; } 512 _LIBCPP_HIDE_FROM_ABI constexpr size_type size_bytes() const noexcept { return __size_ * sizeof(element_type); } 513 [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr bool empty() const noexcept { return __size_ == 0; } 514 515 _LIBCPP_HIDE_FROM_ABI constexpr reference operator[](size_type __idx) const noexcept { 516 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(__idx < size(), "span<T>::operator[](index): index out of range"); 517 return __data_[__idx]; 518 } 519 520# if _LIBCPP_STD_VER >= 26 521 _LIBCPP_HIDE_FROM_ABI constexpr reference at(size_type __index) const { 522 if (__index >= size()) 523 std::__throw_out_of_range("span"); 524 return __data_[__index]; 525 } 526# endif 527 528 _LIBCPP_HIDE_FROM_ABI constexpr reference front() const noexcept { 529 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::front() on empty span"); 530 return __data_[0]; 531 } 532 533 _LIBCPP_HIDE_FROM_ABI constexpr reference back() const noexcept { 534 _LIBCPP_ASSERT_VALID_ELEMENT_ACCESS(!empty(), "span<T>::back() on empty span"); 535 return __data_[size() - 1]; 536 } 537 538 _LIBCPP_HIDE_FROM_ABI constexpr pointer data() const noexcept { return __data_; } 539 540 // [span.iter], span iterator support 541 _LIBCPP_HIDE_FROM_ABI constexpr iterator begin() const noexcept { 542# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 543 return std::__make_bounded_iter(data(), data(), data() + size()); 544# else 545 return iterator(data()); 546# endif 547 } 548 _LIBCPP_HIDE_FROM_ABI constexpr iterator end() const noexcept { 549# ifdef _LIBCPP_ABI_BOUNDED_ITERATORS 550 return std::__make_bounded_iter(data() + size(), data(), data() + size()); 551# else 552 return iterator(data() + size()); 553# endif 554 } 555 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 556 _LIBCPP_HIDE_FROM_ABI constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 557 558 _LIBCPP_HIDE_FROM_ABI span<const byte, dynamic_extent> __as_bytes() const noexcept { 559 return {reinterpret_cast<const byte*>(data()), size_bytes()}; 560 } 561 562 _LIBCPP_HIDE_FROM_ABI span<byte, dynamic_extent> __as_writable_bytes() const noexcept { 563 return {reinterpret_cast<byte*>(data()), size_bytes()}; 564 } 565 566private: 567 pointer __data_; 568 size_type __size_; 569}; 570 571template <class _Tp, size_t _Extent> 572inline constexpr bool ranges::enable_borrowed_range<span<_Tp, _Extent> > = true; 573 574template <class _ElementType, size_t _Extent> 575inline constexpr bool ranges::enable_view<span<_ElementType, _Extent>> = true; 576 577// as_bytes & as_writable_bytes 578template <class _Tp, size_t _Extent> 579_LIBCPP_HIDE_FROM_ABI auto as_bytes(span<_Tp, _Extent> __s) noexcept { 580 return __s.__as_bytes(); 581} 582 583template <class _Tp, size_t _Extent> 584 requires(!is_const_v<_Tp>) 585_LIBCPP_HIDE_FROM_ABI auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept { 586 return __s.__as_writable_bytes(); 587} 588 589# if _LIBCPP_STD_VER >= 26 590template <class _Tp> 591concept __integral_constant_like = 592 is_integral_v<decltype(_Tp::value)> && !is_same_v<bool, remove_const_t<decltype(_Tp::value)>> && 593 convertible_to<_Tp, decltype(_Tp::value)> && equality_comparable_with<_Tp, decltype(_Tp::value)> && 594 bool_constant<_Tp() == _Tp::value>::value && 595 bool_constant<static_cast<decltype(_Tp::value)>(_Tp()) == _Tp::value>::value; 596 597template <class _Tp> 598inline constexpr size_t __maybe_static_ext = dynamic_extent; 599 600template <__integral_constant_like _Tp> 601inline constexpr size_t __maybe_static_ext<_Tp> = {_Tp::value}; 602 603template <contiguous_iterator _It, class _EndOrSize> 604span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>, __maybe_static_ext<_EndOrSize>>; 605# else 606template <contiguous_iterator _It, class _EndOrSize> 607span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>; 608# endif 609 610template <class _Tp, size_t _Sz> 611span(_Tp (&)[_Sz]) -> span<_Tp, _Sz>; 612 613template <class _Tp, size_t _Sz> 614span(array<_Tp, _Sz>&) -> span<_Tp, _Sz>; 615 616template <class _Tp, size_t _Sz> 617span(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>; 618 619template <ranges::contiguous_range _Range> 620span(_Range&&) -> span<remove_reference_t<ranges::range_reference_t<_Range>>>; 621 622#endif // _LIBCPP_STD_VER >= 20 623 624_LIBCPP_END_NAMESPACE_STD 625 626_LIBCPP_POP_MACROS 627 628#if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20 629# include <array> 630# include <concepts> 631# include <functional> 632# include <iterator> 633# include <type_traits> 634#endif 635 636#endif // _LIBCPP_SPAN 637