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 span(const span& other) noexcept = default; 72 template <class OtherElementType, size_t OtherExtent> 73 constexpr explicit(Extent != dynamic_extent) span(const span<OtherElementType, OtherExtent>& s) noexcept; 74 ~span() noexcept = default; 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 front() const; 97 constexpr reference back() const; 98 constexpr pointer data() const noexcept; 99 100 // [span.iterators], span iterator support 101 constexpr iterator begin() const noexcept; 102 constexpr iterator end() const noexcept; 103 constexpr reverse_iterator rbegin() const noexcept; 104 constexpr reverse_iterator rend() const noexcept; 105 106private: 107 pointer data_; // exposition only 108 size_type size_; // exposition only 109}; 110 111template<class It, class EndOrSize> 112 span(It, EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>; 113 114template<class T, size_t N> 115 span(T (&)[N]) -> span<T, N>; 116 117template<class T, size_t N> 118 span(array<T, N>&) -> span<T, N>; 119 120template<class T, size_t N> 121 span(const array<T, N>&) -> span<const T, N>; 122 123template<class R> 124 span(R&&) -> span<remove_reference_t<ranges::range_reference_t<R>>>; 125 126} // namespace std 127 128*/ 129 130#include <__assert> // all public C++ headers provide the assertion handler 131#include <__config> 132#include <__debug> 133#include <__fwd/span.h> 134#include <__iterator/concepts.h> 135#include <__iterator/iterator_traits.h> 136#include <__iterator/wrap_iter.h> 137#include <__memory/pointer_traits.h> 138#include <__ranges/concepts.h> 139#include <__ranges/data.h> 140#include <__ranges/enable_borrowed_range.h> 141#include <__ranges/enable_view.h> 142#include <__ranges/size.h> 143#include <__utility/forward.h> 144#include <array> // for array 145#include <cstddef> // for byte 146#include <iterator> // TODO: Remove this include 147#include <limits> 148#include <type_traits> // for remove_cv, etc 149#include <version> 150 151#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 152# pragma GCC system_header 153#endif 154 155_LIBCPP_PUSH_MACROS 156#include <__undef_macros> 157 158_LIBCPP_BEGIN_NAMESPACE_STD 159 160#if _LIBCPP_STD_VER > 17 161 162template <class _Tp> 163struct __is_std_array : false_type {}; 164 165template <class _Tp, size_t _Sz> 166struct __is_std_array<array<_Tp, _Sz>> : true_type {}; 167 168template <class _Tp> 169struct __is_std_span : false_type {}; 170 171template <class _Tp, size_t _Sz> 172struct __is_std_span<span<_Tp, _Sz>> : true_type {}; 173 174#if defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 175// This is a temporary workaround until we ship <ranges> -- we've unfortunately been 176// shipping <span> before its API was finalized, and we used to provide a constructor 177// from container types that had the requirements below. To avoid breaking code that 178// has started relying on the range-based constructor until we ship all of <ranges>, 179// we emulate the constructor requirements like this. 180template <class _Range, class _ElementType> 181concept __span_compatible_range = 182 !__is_std_span<remove_cvref_t<_Range>>::value && 183 !__is_std_array<remove_cvref_t<_Range>>::value && 184 !is_array_v<remove_cvref_t<_Range>> && 185 requires (_Range&& __r) { 186 data(std::forward<_Range>(__r)); 187 size(std::forward<_Range>(__r)); 188 } && 189 is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>>(*)[], _ElementType(*)[]>; 190#else 191template <class _Range, class _ElementType> 192concept __span_compatible_range = 193 ranges::contiguous_range<_Range> && 194 ranges::sized_range<_Range> && 195 (ranges::borrowed_range<_Range> || is_const_v<_ElementType>) && 196 !__is_std_span<remove_cvref_t<_Range>>::value && 197 !__is_std_array<remove_cvref_t<_Range>>::value && 198 !is_array_v<remove_cvref_t<_Range>> && 199 is_convertible_v<remove_reference_t<ranges::range_reference_t<_Range>>(*)[], _ElementType(*)[]>; 200#endif // !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 201 202#if defined(_LIBCPP_ENABLE_DEBUG_MODE) || defined(_LIBCPP_ABI_SPAN_POINTER_ITERATORS) 203# define _LIBCPP_SPAN_USE_POINTER_ITERATOR 204#endif 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_SPAN_USE_POINTER_ITERATOR 219 using iterator = pointer; 220#else 221 using iterator = __wrap_iter<pointer>; 222#endif 223 using reverse_iterator = _VSTD::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, enable_if_t<_Sz == 0, nullptr_t> = nullptr> 229 _LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr} {} 230 231 constexpr span (const span&) noexcept = default; 232 constexpr span& operator=(const span&) noexcept = default; 233 234 template <class _It, 235 enable_if_t<contiguous_iterator<_It> && 236 is_convertible_v<remove_reference_t<iter_reference_t<_It>>(*)[], element_type (*)[]>, 237 nullptr_t> = nullptr> 238 _LIBCPP_INLINE_VISIBILITY 239 constexpr explicit span(_It __first, size_type __count) 240 : __data{_VSTD::to_address(__first)} { 241 (void)__count; 242 _LIBCPP_ASSERT(_Extent == __count, "size mismatch in span's constructor (iterator, len)"); 243 } 244 245 template < 246 class _It, class _End, 247 enable_if_t<is_convertible_v<remove_reference_t<iter_reference_t<_It> > (*)[], element_type (*)[]> && 248 contiguous_iterator<_It> && sized_sentinel_for<_End, _It> && !is_convertible_v<_End, size_t>, 249 nullptr_t> = nullptr> 250 _LIBCPP_INLINE_VISIBILITY 251 constexpr explicit span(_It __first, _End __last) : __data{_VSTD::to_address(__first)} { 252 (void)__last; 253 _LIBCPP_ASSERT((__last - __first >= 0), "invalid range in span's constructor (iterator, sentinel)"); 254 _LIBCPP_ASSERT(__last - __first == _Extent, 255 "invalid range in span's constructor (iterator, sentinel): last - first != extent"); 256 } 257 258 _LIBCPP_INLINE_VISIBILITY constexpr span(type_identity_t<element_type> (&__arr)[_Extent]) noexcept : __data{__arr} {} 259 260 template <class _OtherElementType, 261 enable_if_t<is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr> 262 _LIBCPP_INLINE_VISIBILITY 263 constexpr span(array<_OtherElementType, _Extent>& __arr) noexcept : __data{__arr.data()} {} 264 265 template <class _OtherElementType, 266 enable_if_t<is_convertible_v<const _OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr> 267 _LIBCPP_INLINE_VISIBILITY 268 constexpr span(const array<_OtherElementType, _Extent>& __arr) noexcept : __data{__arr.data()} {} 269 270#if defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 271 template <class _Container> 272 requires __span_compatible_range<_Container, element_type> 273 _LIBCPP_INLINE_VISIBILITY 274 constexpr explicit span(_Container& __c) : __data{std::data(__c)} { 275 _LIBCPP_ASSERT(std::size(__c) == _Extent, "size mismatch in span's constructor (range)"); 276 } 277 template <class _Container> 278 requires __span_compatible_range<const _Container, element_type> 279 _LIBCPP_INLINE_VISIBILITY 280 constexpr explicit span(const _Container& __c) : __data{std::data(__c)} { 281 _LIBCPP_ASSERT(std::size(__c) == _Extent, "size mismatch in span's constructor (range)"); 282 } 283#else 284 template <__span_compatible_range<element_type> _Range> 285 _LIBCPP_INLINE_VISIBILITY 286 constexpr explicit span(_Range&& __r) : __data{ranges::data(__r)} { 287 _LIBCPP_ASSERT(ranges::size(__r) == _Extent, "size mismatch in span's constructor (range)"); 288 } 289#endif 290 291 template <class _OtherElementType> 292 _LIBCPP_INLINE_VISIBILITY 293 constexpr span(const span<_OtherElementType, _Extent>& __other, 294 enable_if_t< 295 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, 296 nullptr_t> = nullptr) 297 : __data{__other.data()} {} 298 299 template <class _OtherElementType> 300 _LIBCPP_INLINE_VISIBILITY 301 constexpr explicit span(const span<_OtherElementType, dynamic_extent>& __other, 302 enable_if_t< 303 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, 304 nullptr_t> = nullptr) noexcept 305 : __data{__other.data()} { _LIBCPP_ASSERT(_Extent == __other.size(), "size mismatch in span's constructor (other span)"); } 306 307 308// ~span() noexcept = default; 309 310 template <size_t _Count> 311 _LIBCPP_INLINE_VISIBILITY 312 constexpr span<element_type, _Count> first() const noexcept 313 { 314 static_assert(_Count <= _Extent, "Count out of range in span::first()"); 315 return span<element_type, _Count>{data(), _Count}; 316 } 317 318 template <size_t _Count> 319 _LIBCPP_INLINE_VISIBILITY 320 constexpr span<element_type, _Count> last() const noexcept 321 { 322 static_assert(_Count <= _Extent, "Count out of range in span::last()"); 323 return span<element_type, _Count>{data() + size() - _Count, _Count}; 324 } 325 326 _LIBCPP_INLINE_VISIBILITY 327 constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept 328 { 329 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)"); 330 return {data(), __count}; 331 } 332 333 _LIBCPP_INLINE_VISIBILITY 334 constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept 335 { 336 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)"); 337 return {data() + size() - __count, __count}; 338 } 339 340 template <size_t _Offset, size_t _Count = dynamic_extent> 341 _LIBCPP_INLINE_VISIBILITY 342 constexpr auto subspan() const noexcept 343 -> span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset> 344 { 345 static_assert(_Offset <= _Extent, "Offset out of range in span::subspan()"); 346 static_assert(_Count == dynamic_extent || _Count <= _Extent - _Offset, "Offset + count out of range in span::subspan()"); 347 348 using _ReturnType = span<element_type, _Count != dynamic_extent ? _Count : _Extent - _Offset>; 349 return _ReturnType{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 350 } 351 352 353 _LIBCPP_INLINE_VISIBILITY 354 constexpr span<element_type, dynamic_extent> 355 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept 356 { 357 _LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)"); 358 _LIBCPP_ASSERT(__count <= size() || __count == dynamic_extent, "Count out of range in span::subspan(offset, count)"); 359 if (__count == dynamic_extent) 360 return {data() + __offset, size() - __offset}; 361 _LIBCPP_ASSERT(__count <= size() - __offset, "Offset + count out of range in span::subspan(offset, count)"); 362 return {data() + __offset, __count}; 363 } 364 365 _LIBCPP_INLINE_VISIBILITY constexpr size_type size() const noexcept { return _Extent; } 366 _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); } 367 [[nodiscard]] _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return _Extent == 0; } 368 369 _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept 370 { 371 _LIBCPP_ASSERT(__idx < size(), "span<T,N>[] index out of bounds"); 372 return __data[__idx]; 373 } 374 375 _LIBCPP_INLINE_VISIBILITY constexpr reference front() const noexcept 376 { 377 _LIBCPP_ASSERT(!empty(), "span<T, N>::front() on empty span"); 378 return __data[0]; 379 } 380 381 _LIBCPP_INLINE_VISIBILITY constexpr reference back() const noexcept 382 { 383 _LIBCPP_ASSERT(!empty(), "span<T, N>::back() on empty span"); 384 return __data[size()-1]; 385 } 386 387 _LIBCPP_INLINE_VISIBILITY constexpr pointer data() const noexcept { return __data; } 388 389// [span.iter], span iterator support 390 _LIBCPP_INLINE_VISIBILITY constexpr iterator begin() const noexcept { 391#ifdef _LIBCPP_SPAN_USE_POINTER_ITERATOR 392 return iterator(data()); 393#else 394 return iterator(this, data()); 395#endif 396 } 397 _LIBCPP_INLINE_VISIBILITY constexpr iterator end() const noexcept { 398#ifdef _LIBCPP_SPAN_USE_POINTER_ITERATOR 399 return iterator(data() + size()); 400#else 401 return iterator(this, data() + size()); 402#endif 403 } 404 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 405 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 406 407 _LIBCPP_INLINE_VISIBILITY span<const byte, _Extent * sizeof(element_type)> __as_bytes() const noexcept 408 { return span<const byte, _Extent * sizeof(element_type)>{reinterpret_cast<const byte *>(data()), size_bytes()}; } 409 410 _LIBCPP_INLINE_VISIBILITY span<byte, _Extent * sizeof(element_type)> __as_writable_bytes() const noexcept 411 { return span<byte, _Extent * sizeof(element_type)>{reinterpret_cast<byte *>(data()), size_bytes()}; } 412 413private: 414 pointer __data; 415 416}; 417 418 419template <typename _Tp> 420class _LIBCPP_TEMPLATE_VIS span<_Tp, dynamic_extent> { 421private: 422 423public: 424// constants and types 425 using element_type = _Tp; 426 using value_type = remove_cv_t<_Tp>; 427 using size_type = size_t; 428 using difference_type = ptrdiff_t; 429 using pointer = _Tp *; 430 using const_pointer = const _Tp *; 431 using reference = _Tp &; 432 using const_reference = const _Tp &; 433#ifdef _LIBCPP_SPAN_USE_POINTER_ITERATOR 434 using iterator = pointer; 435#else 436 using iterator = __wrap_iter<pointer>; 437#endif 438 using reverse_iterator = _VSTD::reverse_iterator<iterator>; 439 440 static constexpr size_type extent = dynamic_extent; 441 442// [span.cons], span constructors, copy, assignment, and destructor 443 _LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr}, __size{0} {} 444 445 constexpr span (const span&) noexcept = default; 446 constexpr span& operator=(const span&) noexcept = default; 447 448 template <class _It, 449 enable_if_t<contiguous_iterator<_It> && 450 is_convertible_v<remove_reference_t<iter_reference_t<_It> > (*)[], element_type (*)[]>, 451 nullptr_t> = nullptr> 452 _LIBCPP_INLINE_VISIBILITY 453 constexpr span(_It __first, size_type __count) 454 : __data{_VSTD::to_address(__first)}, __size{__count} {} 455 456 template < 457 class _It, class _End, 458 enable_if_t<is_convertible_v<remove_reference_t<iter_reference_t<_It> > (*)[], element_type (*)[]> && 459 contiguous_iterator<_It> && sized_sentinel_for<_End, _It> && !is_convertible_v<_End, size_t>, 460 nullptr_t> = nullptr> 461 _LIBCPP_INLINE_VISIBILITY 462 constexpr span(_It __first, _End __last) 463 : __data(_VSTD::to_address(__first)), __size(__last - __first) {} 464 465 template <size_t _Sz> 466 _LIBCPP_INLINE_VISIBILITY 467 constexpr span(type_identity_t<element_type> (&__arr)[_Sz]) noexcept : __data{__arr}, __size{_Sz} {} 468 469 template <class _OtherElementType, size_t _Sz, 470 enable_if_t<is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr> 471 _LIBCPP_INLINE_VISIBILITY 472 constexpr span(array<_OtherElementType, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {} 473 474 template <class _OtherElementType, size_t _Sz, 475 enable_if_t<is_convertible_v<const _OtherElementType(*)[], element_type (*)[]>, nullptr_t> = nullptr> 476 _LIBCPP_INLINE_VISIBILITY 477 constexpr span(const array<_OtherElementType, _Sz>& __arr) noexcept : __data{__arr.data()}, __size{_Sz} {} 478 479#if defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 480 template <class _Container> 481 requires __span_compatible_range<_Container, element_type> 482 _LIBCPP_INLINE_VISIBILITY 483 constexpr span(_Container& __c) : __data(std::data(__c)), __size{std::size(__c)} {} 484 template <class _Container> 485 requires __span_compatible_range<const _Container, element_type> 486 _LIBCPP_INLINE_VISIBILITY 487 constexpr span(const _Container& __c) : __data(std::data(__c)), __size{std::size(__c)} {} 488#else 489 template <__span_compatible_range<element_type> _Range> 490 _LIBCPP_INLINE_VISIBILITY 491 constexpr span(_Range&& __r) : __data(ranges::data(__r)), __size{ranges::size(__r)} {} 492#endif 493 494 template <class _OtherElementType, size_t _OtherExtent> 495 _LIBCPP_INLINE_VISIBILITY 496 constexpr span(const span<_OtherElementType, _OtherExtent>& __other, 497 enable_if_t< 498 is_convertible_v<_OtherElementType(*)[], element_type (*)[]>, 499 nullptr_t> = nullptr) noexcept 500 : __data{__other.data()}, __size{__other.size()} {} 501 502// ~span() noexcept = default; 503 504 template <size_t _Count> 505 _LIBCPP_INLINE_VISIBILITY 506 constexpr span<element_type, _Count> first() const noexcept 507 { 508 _LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::first()"); 509 return span<element_type, _Count>{data(), _Count}; 510 } 511 512 template <size_t _Count> 513 _LIBCPP_INLINE_VISIBILITY 514 constexpr span<element_type, _Count> last() const noexcept 515 { 516 _LIBCPP_ASSERT(_Count <= size(), "Count out of range in span::last()"); 517 return span<element_type, _Count>{data() + size() - _Count, _Count}; 518 } 519 520 _LIBCPP_INLINE_VISIBILITY 521 constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept 522 { 523 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)"); 524 return {data(), __count}; 525 } 526 527 _LIBCPP_INLINE_VISIBILITY 528 constexpr span<element_type, dynamic_extent> last (size_type __count) const noexcept 529 { 530 _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)"); 531 return {data() + size() - __count, __count}; 532 } 533 534 template <size_t _Offset, size_t _Count = dynamic_extent> 535 _LIBCPP_INLINE_VISIBILITY 536 constexpr span<element_type, _Count> subspan() const noexcept 537 { 538 _LIBCPP_ASSERT(_Offset <= size(), "Offset out of range in span::subspan()"); 539 _LIBCPP_ASSERT(_Count == dynamic_extent || _Count <= size() - _Offset, "Offset + count out of range in span::subspan()"); 540 return span<element_type, _Count>{data() + _Offset, _Count == dynamic_extent ? size() - _Offset : _Count}; 541 } 542 543 constexpr span<element_type, dynamic_extent> 544 _LIBCPP_INLINE_VISIBILITY 545 subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept 546 { 547 _LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)"); 548 _LIBCPP_ASSERT(__count <= size() || __count == dynamic_extent, "count out of range in span::subspan(offset, count)"); 549 if (__count == dynamic_extent) 550 return {data() + __offset, size() - __offset}; 551 _LIBCPP_ASSERT(__count <= size() - __offset, "Offset + count out of range in span::subspan(offset, count)"); 552 return {data() + __offset, __count}; 553 } 554 555 _LIBCPP_INLINE_VISIBILITY constexpr size_type size() const noexcept { return __size; } 556 _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return __size * sizeof(element_type); } 557 [[nodiscard]] _LIBCPP_INLINE_VISIBILITY constexpr bool empty() const noexcept { return __size == 0; } 558 559 _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept 560 { 561 _LIBCPP_ASSERT(__idx < size(), "span<T>[] index out of bounds"); 562 return __data[__idx]; 563 } 564 565 _LIBCPP_INLINE_VISIBILITY constexpr reference front() const noexcept 566 { 567 _LIBCPP_ASSERT(!empty(), "span<T>[].front() on empty span"); 568 return __data[0]; 569 } 570 571 _LIBCPP_INLINE_VISIBILITY constexpr reference back() const noexcept 572 { 573 _LIBCPP_ASSERT(!empty(), "span<T>[].back() on empty span"); 574 return __data[size()-1]; 575 } 576 577 578 _LIBCPP_INLINE_VISIBILITY constexpr pointer data() const noexcept { return __data; } 579 580// [span.iter], span iterator support 581 _LIBCPP_INLINE_VISIBILITY constexpr iterator begin() const noexcept { 582#ifdef _LIBCPP_SPAN_USE_POINTER_ITERATOR 583 return iterator(data()); 584#else 585 return iterator(this, data()); 586#endif 587 } 588 _LIBCPP_INLINE_VISIBILITY constexpr iterator end() const noexcept { 589#ifdef _LIBCPP_SPAN_USE_POINTER_ITERATOR 590 return iterator(data() + size()); 591#else 592 return iterator(this, data() + size()); 593#endif 594 } 595 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(end()); } 596 _LIBCPP_INLINE_VISIBILITY constexpr reverse_iterator rend() const noexcept { return reverse_iterator(begin()); } 597 598 _LIBCPP_INLINE_VISIBILITY span<const byte, dynamic_extent> __as_bytes() const noexcept 599 { return {reinterpret_cast<const byte *>(data()), size_bytes()}; } 600 601 _LIBCPP_INLINE_VISIBILITY span<byte, dynamic_extent> __as_writable_bytes() const noexcept 602 { return {reinterpret_cast<byte *>(data()), size_bytes()}; } 603 604private: 605 pointer __data; 606 size_type __size; 607}; 608 609template <class _Tp, size_t _Extent> 610inline constexpr bool ranges::enable_borrowed_range<span<_Tp, _Extent> > = true; 611 612template <class _ElementType, size_t _Extent> 613inline constexpr bool ranges::enable_view<span<_ElementType, _Extent>> = true; 614 615// as_bytes & as_writable_bytes 616template <class _Tp, size_t _Extent> 617_LIBCPP_INLINE_VISIBILITY 618auto as_bytes(span<_Tp, _Extent> __s) noexcept 619-> decltype(__s.__as_bytes()) 620{ return __s.__as_bytes(); } 621 622template <class _Tp, size_t _Extent> 623_LIBCPP_INLINE_VISIBILITY 624auto as_writable_bytes(span<_Tp, _Extent> __s) noexcept 625-> enable_if_t<!is_const_v<_Tp>, decltype(__s.__as_writable_bytes())> 626{ return __s.__as_writable_bytes(); } 627 628#if _LIBCPP_STD_VER > 17 629template<contiguous_iterator _It, class _EndOrSize> 630 span(_It, _EndOrSize) -> span<remove_reference_t<iter_reference_t<_It>>>; 631#endif // _LIBCPP_STD_VER > 17 632 633template<class _Tp, size_t _Sz> 634 span(_Tp (&)[_Sz]) -> span<_Tp, _Sz>; 635 636template<class _Tp, size_t _Sz> 637 span(array<_Tp, _Sz>&) -> span<_Tp, _Sz>; 638 639template<class _Tp, size_t _Sz> 640 span(const array<_Tp, _Sz>&) -> span<const _Tp, _Sz>; 641 642#if defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES) 643template<class _Container> 644 span(_Container&) -> span<typename _Container::value_type>; 645 646template<class _Container> 647 span(const _Container&) -> span<const typename _Container::value_type>; 648#else 649template<ranges::contiguous_range _Range> 650 span(_Range&&) -> span<remove_reference_t<ranges::range_reference_t<_Range>>>; 651#endif 652 653#endif // _LIBCPP_STD_VER > 17 654 655_LIBCPP_END_NAMESPACE_STD 656 657_LIBCPP_POP_MACROS 658 659#endif // _LIBCPP_SPAN 660