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$ cat -n /usr/include/c++/11/span 1 // Components for manipulating non-owning sequences of objects -*- C++ -*- 2 3 // Copyright (C) 2019-2021 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 <array> 42 #include <cstddef> 43 #include <bits/stl_iterator.h> 44 #include <bits/ranges_base.h> 45 46 #if __cpp_lib_concepts 47 namespace 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<std::array<_Tp, _Num>> : true_type { }; 71 72 template<size_t _Extent> 73 class __extent_storage 74 { 75 public: 76 constexpr 77 __extent_storage(size_t) noexcept 78 { } 79 80 static constexpr size_t 81 _M_extent() noexcept 82 { return _Extent; } 83 }; 84 85 template<> 86 class __extent_storage<dynamic_extent> 87 { 88 public: 89 constexpr 90 __extent_storage(size_t __extent) noexcept 91 : _M_extent_value(__extent) 92 { } 93 94 constexpr size_t 95 _M_extent() const noexcept 96 { return this->_M_extent_value; } 97 98 private: 99 size_t _M_extent_value; 100 }; 101 } // namespace __detail 102 103 template<typename _Type, size_t _Extent = dynamic_extent> 104 class span 105 { 106 template<size_t _Offset, size_t _Count> 107 static constexpr size_t 108 _S_subspan_extent() 109 { 110 if constexpr (_Count != dynamic_extent) 111 return _Count; 112 else if constexpr (extent != dynamic_extent) 113 return _Extent - _Offset; 114 else 115 return dynamic_extent; 116 } 117 118 // _GLIBCXX_RESOLVE_LIB_DEFECTS 119 // 3255. span's array constructor is too strict 120 template<typename _Tp, size_t _ArrayExtent> 121 requires (_Extent == dynamic_extent || _ArrayExtent == _Extent) 122 using __is_compatible_array = __is_array_convertible<_Type, _Tp>; 123 124 template<typename _Ref> 125 using __is_compatible_ref 126 = __is_array_convertible<_Type, remove_reference_t<_Ref>>; 127 128 public: 129 // member types 130 using element_type = _Type; 131 using value_type = remove_cv_t<_Type>; 132 using size_type = size_t; 133 using difference_type = ptrdiff_t; 134 using pointer = _Type*; 135 using const_pointer = const _Type*; 136 using reference = element_type&; 137 using const_reference = const element_type&; 138 using iterator = __gnu_cxx::__normal_iterator<pointer, span>; 139 using reverse_iterator = std::reverse_iterator<iterator>; 140 141 // member constants 142 static constexpr size_t extent = _Extent; 143 144 // constructors, copy and assignment 145 146 constexpr 147 span() noexcept 148 requires ((_Extent + 1u) <= 1u) 149 : _M_ptr(nullptr), _M_extent(0) 150 { } 151 152 template<contiguous_iterator _It> 153 requires __is_compatible_ref<iter_reference_t<_It>>::value 154 constexpr explicit(extent != dynamic_extent) 155 span(_It __first, size_type __count) 156 noexcept 157 : _M_ptr(std::to_address(__first)), _M_extent(__count) 158 { 159 if constexpr (_Extent != dynamic_extent) 160 { 161 __glibcxx_assert(__count == _Extent); 162 } 163 __glibcxx_requires_valid_range(__first, __first + __count); 164 } 165 166 template<contiguous_iterator _It, sized_sentinel_for<_It> _End> 167 requires __is_compatible_ref<iter_reference_t<_It>>::value 168 && (!is_convertible_v<_End, size_type>) 169 constexpr explicit(extent != dynamic_extent) 170 span(_It __first, _End __last) 171 noexcept(noexcept(__last - __first)) 172 : _M_ptr(std::to_address(__first)), 173 _M_extent(static_cast<size_type>(__last - __first)) 174 { 175 if constexpr (_Extent != dynamic_extent) 176 { 177 __glibcxx_assert((__last - __first) == _Extent); 178 } 179 __glibcxx_requires_valid_range(__first, __last); 180 } 181 182 template<size_t _ArrayExtent> 183 requires (_Extent == dynamic_extent || _ArrayExtent == _Extent) 184 constexpr 185 span(type_identity_t<element_type> (&__arr)[_ArrayExtent]) noexcept 186 : span(static_cast<pointer>(__arr), _ArrayExtent) 187 { } 188 189 template<typename _Tp, size_t _ArrayExtent> 190 requires __is_compatible_array<_Tp, _ArrayExtent>::value 191 constexpr 192 span(array<_Tp, _ArrayExtent>& __arr) noexcept 193 : span(static_cast<pointer>(__arr.data()), _ArrayExtent) 194 { } 195 196 template<typename _Tp, size_t _ArrayExtent> 197 requires __is_compatible_array<const _Tp, _ArrayExtent>::value 198 constexpr 199 span(const array<_Tp, _ArrayExtent>& __arr) noexcept 200 : span(static_cast<pointer>(__arr.data()), _ArrayExtent) 201 { } 202 203 template<typename _Range> 204 requires (!__detail::__is_std_span<remove_cvref_t<_Range>>::value) 205 && (!__detail::__is_std_array<remove_cvref_t<_Range>>::value) 206 && (!is_array_v<remove_cvref_t<_Range>>) 207 && ranges::contiguous_range<_Range> && ranges::sized_range<_Range> 208 && (ranges::borrowed_range<_Range> || is_const_v<element_type>) 209 && __is_compatible_ref<ranges::range_reference_t<_Range>>::value 210 constexpr explicit(extent != dynamic_extent) 211 span(_Range&& __range) 212 noexcept(noexcept(ranges::data(__range)) 213 && noexcept(ranges::size(__range))) 214 : span(ranges::data(__range), ranges::size(__range)) 215 { 216 if constexpr (extent != dynamic_extent) 217 { 218 __glibcxx_assert(ranges::size(__range) == extent); 219 } 220 } 221 222 constexpr 223 span(const span&) noexcept = default; 224 225 template<typename _OType, size_t _OExtent> 226 requires (_Extent == dynamic_extent || _OExtent == dynamic_extent 227 || _Extent == _OExtent) 228 && (__is_array_convertible<_Type, _OType>::value) 229 constexpr 230 explicit(extent != dynamic_extent && _OExtent == dynamic_extent) 231 span(const span<_OType, _OExtent>& __s) noexcept 232 : _M_extent(__s.size()), _M_ptr(__s.data()) 233 { 234 if constexpr (extent != dynamic_extent) 235 { 236 __glibcxx_assert(__s.size() == extent); 237 } 238 } 239 240 ~span() noexcept = default; 241 242 constexpr span& 243 operator=(const span&) noexcept = default; 244 245 // observers 246 247 constexpr size_type 248 size() const noexcept 249 { return this->_M_extent._M_extent(); } 250 251 constexpr size_type 252 size_bytes() const noexcept 253 { return this->_M_extent._M_extent() * sizeof(element_type); } 254 255 [[nodiscard]] constexpr bool 256 empty() const noexcept 257 { return size() == 0; } 258 259 // element access 260 261 constexpr reference 262 front() const noexcept 263 { 264 __glibcxx_assert(!empty()); 265 return *this->_M_ptr; 266 } 267 268 constexpr reference 269 back() const noexcept 270 { 271 __glibcxx_assert(!empty()); 272 return *(this->_M_ptr + (size() - 1)); 273 } 274 275 constexpr reference 276 operator[](size_type __idx) const noexcept 277 { 278 __glibcxx_assert(__idx < size()); 279 return *(this->_M_ptr + __idx); 280 } 281 282 constexpr pointer 283 data() const noexcept 284 { return this->_M_ptr; } 285 286 // iterator support 287 288 constexpr iterator 289 begin() const noexcept 290 { return iterator(this->_M_ptr); } 291 292 constexpr iterator 293 end() const noexcept 294 { return iterator(this->_M_ptr + this->size()); } 295 296 constexpr reverse_iterator 297 rbegin() const noexcept 298 { return reverse_iterator(this->end()); } 299 300 constexpr reverse_iterator 301 rend() const noexcept 302 { return reverse_iterator(this->begin()); } 303 304 // subviews 305 306 template<size_t _Count> 307 constexpr span<element_type, _Count> 308 first() const noexcept 309 { 310 if constexpr (_Extent == dynamic_extent) 311 __glibcxx_assert(_Count <= size()); 312 else 313 static_assert(_Count <= extent); 314 using _Sp = span<element_type, _Count>; 315 return _Sp{ this->data(), _Count }; 316 } 317 318 constexpr span<element_type, dynamic_extent> 319 first(size_type __count) const noexcept 320 { 321 __glibcxx_assert(__count <= size()); 322 return { this->data(), __count }; 323 } 324 325 template<size_t _Count> 326 constexpr span<element_type, _Count> 327 last() const noexcept 328 { 329 if constexpr (_Extent == dynamic_extent) 330 __glibcxx_assert(_Count <= size()); 331 else 332 static_assert(_Count <= extent); 333 using _Sp = span<element_type, _Count>; 334 return _Sp{ this->data() + (this->size() - _Count), _Count }; 335 } 336 337 constexpr span<element_type, dynamic_extent> 338 last(size_type __count) const noexcept 339 { 340 __glibcxx_assert(__count <= size()); 341 return { this->data() + (this->size() - __count), __count }; 342 } 343 344 template<size_t _Offset, size_t _Count = dynamic_extent> 345 constexpr auto 346 subspan() const noexcept 347 -> span<element_type, _S_subspan_extent<_Offset, _Count>()> 348 { 349 if constexpr (_Extent == dynamic_extent) 350 { 351 __glibcxx_assert(_Offset <= size()); 352 } 353 else 354 static_assert(_Offset <= extent); 355 356 using _Sp = span<element_type, _S_subspan_extent<_Offset, _Count>()>; 357 358 if constexpr (_Count == dynamic_extent) 359 return _Sp{ this->data() + _Offset, this->size() - _Offset }; 360 else 361 { 362 if constexpr (_Extent == dynamic_extent) 363 { 364 __glibcxx_assert(_Count <= size()); 365 __glibcxx_assert(_Count <= (size() - _Offset)); 366 } 367 else 368 { 369 static_assert(_Count <= extent); 370 static_assert(_Count <= (extent - _Offset)); 371 } 372 return _Sp{ this->data() + _Offset, _Count }; 373 } 374 } 375 376 constexpr span<element_type, dynamic_extent> 377 subspan(size_type __offset, size_type __count = dynamic_extent) const 378 noexcept 379 { 380 __glibcxx_assert(__offset <= size()); 381 if (__count == dynamic_extent) 382 __count = this->size() - __offset; 383 else 384 { 385 __glibcxx_assert(__count <= size()); 386 __glibcxx_assert(__offset + __count <= size()); 387 } 388 return {this->data() + __offset, __count}; 389 } 390 391 private: 392 pointer _M_ptr; 393 [[no_unique_address]] __detail::__extent_storage<extent> _M_extent; 394 }; 395 396 // deduction guides 397 398 template<typename _Type, size_t _ArrayExtent> 399 span(_Type(&)[_ArrayExtent]) -> span<_Type, _ArrayExtent>; 400 401 template<typename _Type, size_t _ArrayExtent> 402 span(array<_Type, _ArrayExtent>&) -> span<_Type, _ArrayExtent>; 403 404 template<typename _Type, size_t _ArrayExtent> 405 span(const array<_Type, _ArrayExtent>&) 406 -> span<const _Type, _ArrayExtent>; 407 408 template<contiguous_iterator _Iter, typename _End> 409 span(_Iter, _End) 410 -> span<remove_reference_t<iter_reference_t<_Iter>>>; 411 412 template<ranges::contiguous_range _Range> 413 span(_Range &&) 414 -> span<remove_reference_t<ranges::range_reference_t<_Range&>>>; 415 416 template<typename _Type, size_t _Extent> 417 inline 418 span<const byte, _Extent == dynamic_extent 419 ? dynamic_extent : _Extent * sizeof(_Type)> 420 as_bytes(span<_Type, _Extent> __sp) noexcept 421 { 422 auto data = reinterpret_cast<const byte*>(__sp.data()); 423 auto size = __sp.size_bytes(); 424 constexpr auto extent = _Extent == dynamic_extent 425 ? dynamic_extent : _Extent * sizeof(_Type); 426 return span<const byte, extent>{data, size}; 427 } 428 429 template<typename _Type, size_t _Extent> 430 requires (!is_const_v<_Type>) 431 inline 432 span<byte, _Extent == dynamic_extent 433 ? dynamic_extent : _Extent * sizeof(_Type)> 434 as_writable_bytes(span<_Type, _Extent> __sp) noexcept 435 { 436 auto data = reinterpret_cast<byte*>(__sp.data()); 437 auto size = __sp.size_bytes(); 438 constexpr auto extent = _Extent == dynamic_extent 439 ? dynamic_extent : _Extent * sizeof(_Type); 440 return span<byte, extent>{data, size}; 441 } 442 443 namespace ranges 444 { 445 // Opt-in to borrowed_range concept 446 template<typename _ElementType, size_t _Extent> 447 inline constexpr bool 448 enable_borrowed_range<span<_ElementType, _Extent>> = true; 449 450 // Opt-in to view concept 451 template<typename _ElementType, size_t _Extent> 452 inline constexpr bool 453 enable_view<span<_ElementType, _Extent>> = true; 454 } 455 _GLIBCXX_END_NAMESPACE_VERSION 456 } // namespace std 457 #endif // concepts 458 #endif // C++20 459 #endif // _GLIBCXX_SPAN
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