1// Components for manipulating non-owning sequences of objects -*- C++ -*- 2 3// Copyright (C) 2019-2020 Free Software Foundation, Inc. 4// 5// This file is part of the GNU ISO C++ Library. This library is free 6// software; you can redistribute it and/or modify it under the 7// terms of the GNU General Public License as published by the 8// Free Software Foundation; either version 3, or (at your option) 9// any later version. 10 11// This library is distributed in the hope that it will be useful, 12// but WITHOUT ANY WARRANTY; without even the implied warranty of 13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14// GNU General Public License for more details. 15 16// Under Section 7 of GPL version 3, you are granted additional 17// permissions described in the GCC Runtime Library Exception, version 18// 3.1, as published by the Free Software Foundation. 19 20// You should have received a copy of the GNU General Public License and 21// a copy of the GCC Runtime Library Exception along with this program; 22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 23// <http://www.gnu.org/licenses/>. 24 25/** @file span 26 * This is a Standard C++ Library header. 27 */ 28 29// 30// P0122 span library 31// Contributed by ThePhD 32// 33 34#ifndef _GLIBCXX_SPAN 35#define _GLIBCXX_SPAN 1 36 37#pragma GCC system_header 38 39#if __cplusplus > 201703L 40 41#include <type_traits> 42#include <array> 43#include <bits/stl_iterator.h> 44#include <bits/range_access.h> 45 46#if __cpp_lib_concepts 47namespace std _GLIBCXX_VISIBILITY(default) 48{ 49_GLIBCXX_BEGIN_NAMESPACE_VERSION 50 51#define __cpp_lib_span 202002L 52 53 inline constexpr size_t dynamic_extent = static_cast<size_t>(-1); 54 55 template<typename _Type, size_t _Extent> 56 class span; 57 58 namespace __detail 59 { 60 template<typename _Tp> 61 struct __is_std_span : false_type { }; 62 63 template<typename _Tp, size_t _Num> 64 struct __is_std_span<span<_Tp, _Num>> : true_type { }; 65 66 template<typename _Tp> 67 struct __is_std_array : false_type { }; 68 69 template<typename _Tp, size_t _Num> 70 struct __is_std_array<_GLIBCXX_STD_C::array<_Tp, _Num>> : true_type { }; 71 72#ifdef _GLIBCXX_DEBUG 73 template<typename _Tp, size_t _Num> 74 struct __is_std_array<__debug::array<_Tp, _Num>> : true_type { }; 75#endif 76 77 template<size_t _Extent> 78 class __extent_storage 79 { 80 public: 81 constexpr 82 __extent_storage(size_t) noexcept 83 { } 84 85 static constexpr size_t 86 _M_extent() noexcept 87 { return _Extent; } 88 }; 89 90 template<> 91 class __extent_storage<dynamic_extent> 92 { 93 public: 94 constexpr 95 __extent_storage(size_t __extent) noexcept 96 : _M_extent_value(__extent) 97 { } 98 99 constexpr size_t 100 _M_extent() const noexcept 101 { return this->_M_extent_value; } 102 103 private: 104 size_t _M_extent_value; 105 }; 106 } // namespace __detail 107 108 template<typename _Type, size_t _Extent = dynamic_extent> 109 class span 110 { 111 template<size_t _Offset, size_t _Count> 112 static constexpr size_t 113 _S_subspan_extent() 114 { 115 if constexpr (_Count != dynamic_extent) 116 return _Count; 117 else if constexpr (extent != dynamic_extent) 118 return _Extent - _Offset; 119 else 120 return dynamic_extent; 121 } 122 123 // _GLIBCXX_RESOLVE_LIB_DEFECTS 124 // 3255. span's array constructor is too strict 125 template<typename _Tp, size_t _ArrayExtent> 126 requires (_Extent == dynamic_extent || _ArrayExtent == _Extent) 127 using __is_compatible_array = __is_array_convertible<_Type, _Tp>; 128 129 template<typename _Ref> 130 using __is_compatible_ref 131 = __is_array_convertible<_Type, remove_reference_t<_Ref>>; 132 133 public: 134 // member types 135 using element_type = _Type; 136 using value_type = remove_cv_t<_Type>; 137 using size_type = size_t; 138 using difference_type = ptrdiff_t; 139 using pointer = _Type*; 140 using const_pointer = const _Type*; 141 using reference = element_type&; 142 using const_reference = const element_type&; 143 using iterator = __gnu_cxx::__normal_iterator<pointer, span>; 144 using reverse_iterator = std::reverse_iterator<iterator>; 145 146 // member constants 147 static constexpr size_t extent = _Extent; 148 149 // constructors, copy and assignment 150 151 constexpr 152 span() noexcept 153 requires ((_Extent + 1u) <= 1u) 154 : _M_extent(0), _M_ptr(nullptr) 155 { } 156 157 template<contiguous_iterator _It> 158 requires __is_compatible_ref<iter_reference_t<_It>>::value 159 constexpr explicit(extent != dynamic_extent) 160 span(_It __first, size_type __count) 161 noexcept 162 : _M_extent(__count), _M_ptr(std::to_address(__first)) 163 { 164 if constexpr (_Extent != dynamic_extent) 165 { 166 __glibcxx_assert(__count == _Extent); 167 } 168 __glibcxx_requires_valid_range(__first, __first + __count); 169 } 170 171 template<contiguous_iterator _It, sized_sentinel_for<_It> _End> 172 requires __is_compatible_ref<iter_reference_t<_It>>::value 173 && (!is_convertible_v<_End, size_type>) 174 constexpr explicit(extent != dynamic_extent) 175 span(_It __first, _End __last) 176 noexcept(noexcept(__last - __first)) 177 : _M_extent(static_cast<size_type>(__last - __first)), 178 _M_ptr(std::to_address(__first)) 179 { 180 if constexpr (_Extent != dynamic_extent) 181 { 182 __glibcxx_assert((__last - __first) == _Extent); 183 } 184 __glibcxx_requires_valid_range(__first, __last); 185 } 186 187 template<size_t _ArrayExtent> 188 requires (_Extent == dynamic_extent || _ArrayExtent == _Extent) 189 constexpr 190 span(type_identity_t<element_type> (&__arr)[_ArrayExtent]) noexcept 191 : span(static_cast<pointer>(__arr), _ArrayExtent) 192 { } 193 194 template<typename _Tp, size_t _ArrayExtent> 195 requires __is_compatible_array<_Tp, _ArrayExtent>::value 196 constexpr 197 span(array<_Tp, _ArrayExtent>& __arr) noexcept 198 : span(static_cast<pointer>(__arr.data()), _ArrayExtent) 199 { } 200 201 template<typename _Tp, size_t _ArrayExtent> 202 requires __is_compatible_array<const _Tp, _ArrayExtent>::value 203 constexpr 204 span(const array<_Tp, _ArrayExtent>& __arr) noexcept 205 : span(static_cast<pointer>(__arr.data()), _ArrayExtent) 206 { } 207 208 template<typename _Range> 209 requires (!__detail::__is_std_span<remove_cvref_t<_Range>>::value) 210 && (!__detail::__is_std_array<remove_cvref_t<_Range>>::value) 211 && (!is_array_v<remove_cvref_t<_Range>>) 212 && ranges::contiguous_range<_Range> && ranges::sized_range<_Range> 213 && (ranges::borrowed_range<_Range> || is_const_v<element_type>) 214 && __is_compatible_ref<ranges::range_reference_t<_Range>>::value 215 constexpr explicit(extent != dynamic_extent) 216 span(_Range&& __range) 217 noexcept(noexcept(ranges::data(__range)) 218 && noexcept(ranges::size(__range))) 219 : span(ranges::data(__range), ranges::size(__range)) 220 { 221 if constexpr (extent != dynamic_extent) 222 { 223 __glibcxx_assert(ranges::size(__range) == extent); 224 } 225 } 226 227 constexpr 228 span(const span&) noexcept = default; 229 230 template<typename _OType, size_t _OExtent> 231 requires (_Extent == dynamic_extent || _OExtent == dynamic_extent 232 || _Extent == _OExtent) 233 && (__is_array_convertible<_Type, _OType>::value) 234 constexpr 235 explicit(extent != dynamic_extent && _OExtent == dynamic_extent) 236 span(const span<_OType, _OExtent>& __s) noexcept 237 : _M_extent(__s.size()), _M_ptr(__s.data()) 238 { 239 if constexpr (extent != dynamic_extent) 240 { 241 __glibcxx_assert(__s.size() == extent); 242 } 243 } 244 245 ~span() noexcept = default; 246 247 constexpr span& 248 operator=(const span&) noexcept = default; 249 250 // observers 251 252 constexpr size_type 253 size() const noexcept 254 { return this->_M_extent._M_extent(); } 255 256 constexpr size_type 257 size_bytes() const noexcept 258 { return this->_M_extent._M_extent() * sizeof(element_type); } 259 260 [[nodiscard]] constexpr bool 261 empty() const noexcept 262 { return size() == 0; } 263 264 // element access 265 266 constexpr reference 267 front() const noexcept 268 { 269 __glibcxx_assert(!empty()); 270 return *this->_M_ptr; 271 } 272 273 constexpr reference 274 back() const noexcept 275 { 276 __glibcxx_assert(!empty()); 277 return *(this->_M_ptr + (size() - 1)); 278 } 279 280 constexpr reference 281 operator[](size_type __idx) const noexcept 282 { 283 __glibcxx_assert(__idx < size()); 284 return *(this->_M_ptr + __idx); 285 } 286 287 constexpr pointer 288 data() const noexcept 289 { return this->_M_ptr; } 290 291 // iterator support 292 293 constexpr iterator 294 begin() const noexcept 295 { return iterator(this->_M_ptr); } 296 297 constexpr iterator 298 end() const noexcept 299 { return iterator(this->_M_ptr + this->size()); } 300 301 constexpr reverse_iterator 302 rbegin() const noexcept 303 { return reverse_iterator(this->end()); } 304 305 constexpr reverse_iterator 306 rend() const noexcept 307 { return reverse_iterator(this->begin()); } 308 309 // subviews 310 311 template<size_t _Count> 312 constexpr span<element_type, _Count> 313 first() const noexcept 314 { 315 if constexpr (_Extent == dynamic_extent) 316 __glibcxx_assert(_Count <= size()); 317 else 318 static_assert(_Count <= extent); 319 using _Sp = span<element_type, _Count>; 320 return _Sp{ this->data(), _Count }; 321 } 322 323 constexpr span<element_type, dynamic_extent> 324 first(size_type __count) const noexcept 325 { 326 __glibcxx_assert(__count <= size()); 327 return { this->data(), __count }; 328 } 329 330 template<size_t _Count> 331 constexpr span<element_type, _Count> 332 last() const noexcept 333 { 334 if constexpr (_Extent == dynamic_extent) 335 __glibcxx_assert(_Count <= size()); 336 else 337 static_assert(_Count <= extent); 338 using _Sp = span<element_type, _Count>; 339 return _Sp{ this->data() + (this->size() - _Count), _Count }; 340 } 341 342 constexpr span<element_type, dynamic_extent> 343 last(size_type __count) const noexcept 344 { 345 __glibcxx_assert(__count <= size()); 346 return { this->data() + (this->size() - __count), __count }; 347 } 348 349 template<size_t _Offset, size_t _Count = dynamic_extent> 350 constexpr auto 351 subspan() const noexcept 352 -> span<element_type, _S_subspan_extent<_Offset, _Count>()> 353 { 354 if constexpr (_Extent == dynamic_extent) 355 { 356 __glibcxx_assert(_Offset <= size()); 357 } 358 else 359 static_assert(_Offset <= extent); 360 361 using _Sp = span<element_type, _S_subspan_extent<_Offset, _Count>()>; 362 363 if constexpr (_Count == dynamic_extent) 364 return _Sp{ this->data() + _Offset, this->size() - _Offset }; 365 else 366 { 367 if constexpr (_Extent == dynamic_extent) 368 { 369 __glibcxx_assert(_Count <= size()); 370 __glibcxx_assert(_Count <= (size() - _Offset)); 371 } 372 else 373 { 374 static_assert(_Count <= extent); 375 static_assert(_Count <= (extent - _Offset)); 376 } 377 return _Sp{ this->data() + _Offset, _Count }; 378 } 379 } 380 381 constexpr span<element_type, dynamic_extent> 382 subspan(size_type __offset, size_type __count = dynamic_extent) const 383 noexcept 384 { 385 __glibcxx_assert(__offset <= size()); 386 if (__count == dynamic_extent) 387 __count = this->size() - __offset; 388 else 389 { 390 __glibcxx_assert(__count <= size()); 391 __glibcxx_assert(__offset + __count <= size()); 392 } 393 return {this->data() + __offset, __count}; 394 } 395 396 private: 397 [[no_unique_address]] __detail::__extent_storage<extent> _M_extent; 398 pointer _M_ptr; 399 }; 400 401 // deduction guides 402 403 template<typename _Type, size_t _ArrayExtent> 404 span(_Type(&)[_ArrayExtent]) -> span<_Type, _ArrayExtent>; 405 406 template<typename _Type, size_t _ArrayExtent> 407 span(array<_Type, _ArrayExtent>&) -> span<_Type, _ArrayExtent>; 408 409 template<typename _Type, size_t _ArrayExtent> 410 span(const array<_Type, _ArrayExtent>&) 411 -> span<const _Type, _ArrayExtent>; 412 413 template<contiguous_iterator _Iter, typename _End> 414 span(_Iter, _End) 415 -> span<remove_reference_t<iter_reference_t<_Iter>>>; 416 417 template<ranges::contiguous_range _Range> 418 span(_Range &&) 419 -> span<remove_reference_t<ranges::range_reference_t<_Range&>>>; 420 421 template<typename _Type, size_t _Extent> 422 inline 423 span<const byte, _Extent == dynamic_extent 424 ? dynamic_extent : _Extent * sizeof(_Type)> 425 as_bytes(span<_Type, _Extent> __sp) noexcept 426 { 427 auto data = reinterpret_cast<const byte*>(__sp.data()); 428 auto size = __sp.size_bytes(); 429 constexpr auto extent = _Extent == dynamic_extent 430 ? dynamic_extent : _Extent * sizeof(_Type); 431 return span<const byte, extent>{data, size}; 432 } 433 434 template<typename _Type, size_t _Extent> 435 requires (!is_const_v<_Type>) 436 inline 437 span<byte, _Extent == dynamic_extent 438 ? dynamic_extent : _Extent * sizeof(_Type)> 439 as_writable_bytes(span<_Type, _Extent> __sp) noexcept 440 { 441 auto data = reinterpret_cast<byte*>(__sp.data()); 442 auto size = __sp.size_bytes(); 443 constexpr auto extent = _Extent == dynamic_extent 444 ? dynamic_extent : _Extent * sizeof(_Type); 445 return span<byte, extent>{data, size}; 446 } 447 448 namespace ranges 449 { 450 // Opt-in to borrowed_range concept 451 template<typename _ElementType, size_t _Extent> 452 inline constexpr bool 453 enable_borrowed_range<span<_ElementType, _Extent>> = true; 454 455 // Opt-in to view concept 456 template<typename _ElementType, size_t _Extent> 457 inline constexpr bool 458 enable_view<span<_ElementType, _Extent>> = true; 459 } 460_GLIBCXX_END_NAMESPACE_VERSION 461} // namespace std 462#endif // concepts 463#endif // C++20 464#endif // _GLIBCXX_SPAN 465