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___ITERATOR_ITERATOR_TRAITS_H 11 #define _LIBCPP___ITERATOR_ITERATOR_TRAITS_H 12 13 #include <__config> 14 #include <__iterator/incrementable_traits.h> 15 #include <__iterator/readable_traits.h> 16 #include <concepts> 17 #include <type_traits> 18 19 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER) 20 # pragma GCC system_header 21 #endif 22 23 _LIBCPP_BEGIN_NAMESPACE_STD 24 25 #if _LIBCPP_STD_VER > 17 26 27 template <class _Tp> 28 using __with_reference = _Tp&; 29 30 template <class _Tp> 31 concept __can_reference = requires { 32 typename __with_reference<_Tp>; 33 }; 34 35 template <class _Tp> 36 concept __dereferenceable = requires(_Tp& __t) { 37 { *__t } -> __can_reference; // not required to be equality-preserving 38 }; 39 40 // [iterator.traits] 41 template<__dereferenceable _Tp> 42 using iter_reference_t = decltype(*declval<_Tp&>()); 43 44 #endif // _LIBCPP_STD_VER > 17 45 46 template <class _Iter> 47 struct _LIBCPP_TEMPLATE_VIS iterator_traits; 48 49 struct _LIBCPP_TEMPLATE_VIS input_iterator_tag {}; 50 struct _LIBCPP_TEMPLATE_VIS output_iterator_tag {}; 51 struct _LIBCPP_TEMPLATE_VIS forward_iterator_tag : public input_iterator_tag {}; 52 struct _LIBCPP_TEMPLATE_VIS bidirectional_iterator_tag : public forward_iterator_tag {}; 53 struct _LIBCPP_TEMPLATE_VIS random_access_iterator_tag : public bidirectional_iterator_tag {}; 54 #if _LIBCPP_STD_VER > 17 55 struct _LIBCPP_TEMPLATE_VIS contiguous_iterator_tag : public random_access_iterator_tag {}; 56 #endif 57 58 template <class _Iter> 59 struct __iter_traits_cache { 60 using type = _If< 61 __is_primary_template<iterator_traits<_Iter> >::value, 62 _Iter, 63 iterator_traits<_Iter> 64 >; 65 }; 66 template <class _Iter> 67 using _ITER_TRAITS = typename __iter_traits_cache<_Iter>::type; 68 69 struct __iter_concept_concept_test { 70 template <class _Iter> 71 using _Apply = typename _ITER_TRAITS<_Iter>::iterator_concept; 72 }; 73 struct __iter_concept_category_test { 74 template <class _Iter> 75 using _Apply = typename _ITER_TRAITS<_Iter>::iterator_category; 76 }; 77 struct __iter_concept_random_fallback { 78 template <class _Iter> 79 using _Apply = __enable_if_t< 80 __is_primary_template<iterator_traits<_Iter> >::value, 81 random_access_iterator_tag 82 >; 83 }; 84 85 template <class _Iter, class _Tester> struct __test_iter_concept 86 : _IsValidExpansion<_Tester::template _Apply, _Iter>, 87 _Tester 88 { 89 }; 90 91 template <class _Iter> 92 struct __iter_concept_cache { 93 using type = _Or< 94 __test_iter_concept<_Iter, __iter_concept_concept_test>, 95 __test_iter_concept<_Iter, __iter_concept_category_test>, 96 __test_iter_concept<_Iter, __iter_concept_random_fallback> 97 >; 98 }; 99 100 template <class _Iter> 101 using _ITER_CONCEPT = typename __iter_concept_cache<_Iter>::type::template _Apply<_Iter>; 102 103 104 template <class _Tp> 105 struct __has_iterator_typedefs 106 { 107 private: 108 template <class _Up> static false_type __test(...); 109 template <class _Up> static true_type __test(typename __void_t<typename _Up::iterator_category>::type* = 0, 110 typename __void_t<typename _Up::difference_type>::type* = 0, 111 typename __void_t<typename _Up::value_type>::type* = 0, 112 typename __void_t<typename _Up::reference>::type* = 0, 113 typename __void_t<typename _Up::pointer>::type* = 0); 114 public: 115 static const bool value = decltype(__test<_Tp>(0,0,0,0,0))::value; 116 }; 117 118 119 template <class _Tp> 120 struct __has_iterator_category 121 { 122 private: 123 template <class _Up> static false_type __test(...); 124 template <class _Up> static true_type __test(typename _Up::iterator_category* = nullptr); 125 public: 126 static const bool value = decltype(__test<_Tp>(nullptr))::value; 127 }; 128 129 template <class _Tp> 130 struct __has_iterator_concept 131 { 132 private: 133 template <class _Up> static false_type __test(...); 134 template <class _Up> static true_type __test(typename _Up::iterator_concept* = nullptr); 135 public: 136 static const bool value = decltype(__test<_Tp>(nullptr))::value; 137 }; 138 139 #if _LIBCPP_STD_VER > 17 140 141 // The `cpp17-*-iterator` exposition-only concepts have very similar names to the `Cpp17*Iterator` named requirements 142 // from `[iterator.cpp17]`. To avoid confusion between the two, the exposition-only concepts have been banished to 143 // a "detail" namespace indicating they have a niche use-case. 144 namespace __iterator_traits_detail { 145 template<class _Ip> 146 concept __cpp17_iterator = 147 requires(_Ip __i) { 148 { *__i } -> __can_reference; 149 { ++__i } -> same_as<_Ip&>; 150 { *__i++ } -> __can_reference; 151 } && 152 copyable<_Ip>; 153 154 template<class _Ip> 155 concept __cpp17_input_iterator = 156 __cpp17_iterator<_Ip> && 157 equality_comparable<_Ip> && 158 requires(_Ip __i) { 159 typename incrementable_traits<_Ip>::difference_type; 160 typename indirectly_readable_traits<_Ip>::value_type; 161 typename common_reference_t<iter_reference_t<_Ip>&&, 162 typename indirectly_readable_traits<_Ip>::value_type&>; 163 typename common_reference_t<decltype(*__i++)&&, 164 typename indirectly_readable_traits<_Ip>::value_type&>; 165 requires signed_integral<typename incrementable_traits<_Ip>::difference_type>; 166 }; 167 168 template<class _Ip> 169 concept __cpp17_forward_iterator = 170 __cpp17_input_iterator<_Ip> && 171 constructible_from<_Ip> && 172 is_lvalue_reference_v<iter_reference_t<_Ip>> && 173 same_as<remove_cvref_t<iter_reference_t<_Ip>>, 174 typename indirectly_readable_traits<_Ip>::value_type> && 175 requires(_Ip __i) { 176 { __i++ } -> convertible_to<_Ip const&>; 177 { *__i++ } -> same_as<iter_reference_t<_Ip>>; 178 }; 179 180 template<class _Ip> 181 concept __cpp17_bidirectional_iterator = 182 __cpp17_forward_iterator<_Ip> && 183 requires(_Ip __i) { 184 { --__i } -> same_as<_Ip&>; 185 { __i-- } -> convertible_to<_Ip const&>; 186 { *__i-- } -> same_as<iter_reference_t<_Ip>>; 187 }; 188 189 template<class _Ip> 190 concept __cpp17_random_access_iterator = 191 __cpp17_bidirectional_iterator<_Ip> && 192 totally_ordered<_Ip> && 193 requires(_Ip __i, typename incrementable_traits<_Ip>::difference_type __n) { 194 { __i += __n } -> same_as<_Ip&>; 195 { __i -= __n } -> same_as<_Ip&>; 196 { __i + __n } -> same_as<_Ip>; 197 { __n + __i } -> same_as<_Ip>; 198 { __i - __n } -> same_as<_Ip>; 199 { __i - __i } -> same_as<decltype(__n)>; // NOLINT(misc-redundant-expression) ; This is llvm.org/PR54114 200 { __i[__n] } -> convertible_to<iter_reference_t<_Ip>>; 201 }; 202 } // namespace __iterator_traits_detail 203 204 template<class _Ip> 205 concept __has_member_reference = requires { typename _Ip::reference; }; 206 207 template<class _Ip> 208 concept __has_member_pointer = requires { typename _Ip::pointer; }; 209 210 template<class _Ip> 211 concept __has_member_iterator_category = requires { typename _Ip::iterator_category; }; 212 213 template<class _Ip> 214 concept __specifies_members = requires { 215 typename _Ip::value_type; 216 typename _Ip::difference_type; 217 requires __has_member_reference<_Ip>; 218 requires __has_member_iterator_category<_Ip>; 219 }; 220 221 template<class> 222 struct __iterator_traits_member_pointer_or_void { 223 using type = void; 224 }; 225 226 template<__has_member_pointer _Tp> 227 struct __iterator_traits_member_pointer_or_void<_Tp> { 228 using type = typename _Tp::pointer; 229 }; 230 231 template<class _Tp> 232 concept __cpp17_iterator_missing_members = 233 !__specifies_members<_Tp> && 234 __iterator_traits_detail::__cpp17_iterator<_Tp>; 235 236 template<class _Tp> 237 concept __cpp17_input_iterator_missing_members = 238 __cpp17_iterator_missing_members<_Tp> && 239 __iterator_traits_detail::__cpp17_input_iterator<_Tp>; 240 241 // Otherwise, `pointer` names `void`. 242 template<class> 243 struct __iterator_traits_member_pointer_or_arrow_or_void { using type = void; }; 244 245 // [iterator.traits]/3.2.1 246 // If the qualified-id `I::pointer` is valid and denotes a type, `pointer` names that type. 247 template<__has_member_pointer _Ip> 248 struct __iterator_traits_member_pointer_or_arrow_or_void<_Ip> { using type = typename _Ip::pointer; }; 249 250 // Otherwise, if `decltype(declval<I&>().operator->())` is well-formed, then `pointer` names that 251 // type. 252 template<class _Ip> 253 requires requires(_Ip& __i) { __i.operator->(); } && (!__has_member_pointer<_Ip>) 254 struct __iterator_traits_member_pointer_or_arrow_or_void<_Ip> { 255 using type = decltype(declval<_Ip&>().operator->()); 256 }; 257 258 // Otherwise, `reference` names `iter-reference-t<I>`. 259 template<class _Ip> 260 struct __iterator_traits_member_reference { using type = iter_reference_t<_Ip>; }; 261 262 // [iterator.traits]/3.2.2 263 // If the qualified-id `I::reference` is valid and denotes a type, `reference` names that type. 264 template<__has_member_reference _Ip> 265 struct __iterator_traits_member_reference<_Ip> { using type = typename _Ip::reference; }; 266 267 // [iterator.traits]/3.2.3.4 268 // input_iterator_tag 269 template<class _Ip> 270 struct __deduce_iterator_category { 271 using type = input_iterator_tag; 272 }; 273 274 // [iterator.traits]/3.2.3.1 275 // `random_access_iterator_tag` if `I` satisfies `cpp17-random-access-iterator`, or otherwise 276 template<__iterator_traits_detail::__cpp17_random_access_iterator _Ip> 277 struct __deduce_iterator_category<_Ip> { 278 using type = random_access_iterator_tag; 279 }; 280 281 // [iterator.traits]/3.2.3.2 282 // `bidirectional_iterator_tag` if `I` satisfies `cpp17-bidirectional-iterator`, or otherwise 283 template<__iterator_traits_detail::__cpp17_bidirectional_iterator _Ip> 284 struct __deduce_iterator_category<_Ip> { 285 using type = bidirectional_iterator_tag; 286 }; 287 288 // [iterator.traits]/3.2.3.3 289 // `forward_iterator_tag` if `I` satisfies `cpp17-forward-iterator`, or otherwise 290 template<__iterator_traits_detail::__cpp17_forward_iterator _Ip> 291 struct __deduce_iterator_category<_Ip> { 292 using type = forward_iterator_tag; 293 }; 294 295 template<class _Ip> 296 struct __iterator_traits_iterator_category : __deduce_iterator_category<_Ip> {}; 297 298 // [iterator.traits]/3.2.3 299 // If the qualified-id `I::iterator-category` is valid and denotes a type, `iterator-category` names 300 // that type. 301 template<__has_member_iterator_category _Ip> 302 struct __iterator_traits_iterator_category<_Ip> { 303 using type = typename _Ip::iterator_category; 304 }; 305 306 // otherwise, it names void. 307 template<class> 308 struct __iterator_traits_difference_type { using type = void; }; 309 310 // If the qualified-id `incrementable_traits<I>::difference_type` is valid and denotes a type, then 311 // `difference_type` names that type; 312 template<class _Ip> 313 requires requires { typename incrementable_traits<_Ip>::difference_type; } 314 struct __iterator_traits_difference_type<_Ip> { 315 using type = typename incrementable_traits<_Ip>::difference_type; 316 }; 317 318 // [iterator.traits]/3.4 319 // Otherwise, `iterator_traits<I>` has no members by any of the above names. 320 template<class> 321 struct __iterator_traits {}; 322 323 // [iterator.traits]/3.1 324 // If `I` has valid ([temp.deduct]) member types `difference-type`, `value-type`, `reference`, and 325 // `iterator-category`, then `iterator-traits<I>` has the following publicly accessible members: 326 template<__specifies_members _Ip> 327 struct __iterator_traits<_Ip> { 328 using iterator_category = typename _Ip::iterator_category; 329 using value_type = typename _Ip::value_type; 330 using difference_type = typename _Ip::difference_type; 331 using pointer = typename __iterator_traits_member_pointer_or_void<_Ip>::type; 332 using reference = typename _Ip::reference; 333 }; 334 335 // [iterator.traits]/3.2 336 // Otherwise, if `I` satisfies the exposition-only concept `cpp17-input-iterator`, 337 // `iterator-traits<I>` has the following publicly accessible members: 338 template<__cpp17_input_iterator_missing_members _Ip> 339 struct __iterator_traits<_Ip> { 340 using iterator_category = typename __iterator_traits_iterator_category<_Ip>::type; 341 using value_type = typename indirectly_readable_traits<_Ip>::value_type; 342 using difference_type = typename incrementable_traits<_Ip>::difference_type; 343 using pointer = typename __iterator_traits_member_pointer_or_arrow_or_void<_Ip>::type; 344 using reference = typename __iterator_traits_member_reference<_Ip>::type; 345 }; 346 347 // Otherwise, if `I` satisfies the exposition-only concept `cpp17-iterator`, then 348 // `iterator_traits<I>` has the following publicly accessible members: 349 template<__cpp17_iterator_missing_members _Ip> 350 struct __iterator_traits<_Ip> { 351 using iterator_category = output_iterator_tag; 352 using value_type = void; 353 using difference_type = typename __iterator_traits_difference_type<_Ip>::type; 354 using pointer = void; 355 using reference = void; 356 }; 357 358 template<class _Ip> 359 struct iterator_traits : __iterator_traits<_Ip> { 360 using __primary_template = iterator_traits; 361 }; 362 363 #else // _LIBCPP_STD_VER > 17 364 365 template <class _Iter, bool> struct __iterator_traits {}; 366 367 template <class _Iter, bool> struct __iterator_traits_impl {}; 368 369 template <class _Iter> 370 struct __iterator_traits_impl<_Iter, true> 371 { 372 typedef typename _Iter::difference_type difference_type; 373 typedef typename _Iter::value_type value_type; 374 typedef typename _Iter::pointer pointer; 375 typedef typename _Iter::reference reference; 376 typedef typename _Iter::iterator_category iterator_category; 377 }; 378 379 template <class _Iter> 380 struct __iterator_traits<_Iter, true> 381 : __iterator_traits_impl 382 < 383 _Iter, 384 is_convertible<typename _Iter::iterator_category, input_iterator_tag>::value || 385 is_convertible<typename _Iter::iterator_category, output_iterator_tag>::value 386 > 387 {}; 388 389 // iterator_traits<Iterator> will only have the nested types if Iterator::iterator_category 390 // exists. Else iterator_traits<Iterator> will be an empty class. This is a 391 // conforming extension which allows some programs to compile and behave as 392 // the client expects instead of failing at compile time. 393 394 template <class _Iter> 395 struct _LIBCPP_TEMPLATE_VIS iterator_traits 396 : __iterator_traits<_Iter, __has_iterator_typedefs<_Iter>::value> { 397 398 using __primary_template = iterator_traits; 399 }; 400 #endif // _LIBCPP_STD_VER > 17 401 402 template<class _Tp> 403 #if _LIBCPP_STD_VER > 17 404 requires is_object_v<_Tp> 405 #endif 406 struct _LIBCPP_TEMPLATE_VIS iterator_traits<_Tp*> 407 { 408 typedef ptrdiff_t difference_type; 409 typedef typename remove_cv<_Tp>::type value_type; 410 typedef _Tp* pointer; 411 typedef _Tp& reference; 412 typedef random_access_iterator_tag iterator_category; 413 #if _LIBCPP_STD_VER > 17 414 typedef contiguous_iterator_tag iterator_concept; 415 #endif 416 }; 417 418 template <class _Tp, class _Up, bool = __has_iterator_category<iterator_traits<_Tp> >::value> 419 struct __has_iterator_category_convertible_to 420 : is_convertible<typename iterator_traits<_Tp>::iterator_category, _Up> 421 {}; 422 423 template <class _Tp, class _Up> 424 struct __has_iterator_category_convertible_to<_Tp, _Up, false> : false_type {}; 425 426 template <class _Tp, class _Up, bool = __has_iterator_concept<_Tp>::value> 427 struct __has_iterator_concept_convertible_to 428 : is_convertible<typename _Tp::iterator_concept, _Up> 429 {}; 430 431 template <class _Tp, class _Up> 432 struct __has_iterator_concept_convertible_to<_Tp, _Up, false> : false_type {}; 433 434 template <class _Tp> 435 struct __is_cpp17_input_iterator : public __has_iterator_category_convertible_to<_Tp, input_iterator_tag> {}; 436 437 template <class _Tp> 438 struct __is_cpp17_forward_iterator : public __has_iterator_category_convertible_to<_Tp, forward_iterator_tag> {}; 439 440 template <class _Tp> 441 struct __is_cpp17_bidirectional_iterator : public __has_iterator_category_convertible_to<_Tp, bidirectional_iterator_tag> {}; 442 443 template <class _Tp> 444 struct __is_cpp17_random_access_iterator : public __has_iterator_category_convertible_to<_Tp, random_access_iterator_tag> {}; 445 446 // __is_cpp17_contiguous_iterator determines if an iterator is known by 447 // libc++ to be contiguous, either because it advertises itself as such 448 // (in C++20) or because it is a pointer type or a known trivial wrapper 449 // around a (possibly fancy) pointer type, such as __wrap_iter<T*>. 450 // Such iterators receive special "contiguous" optimizations in 451 // std::copy and std::sort. 452 // 453 #if _LIBCPP_STD_VER > 17 454 template <class _Tp> 455 struct __is_cpp17_contiguous_iterator : _Or< 456 __has_iterator_category_convertible_to<_Tp, contiguous_iterator_tag>, 457 __has_iterator_concept_convertible_to<_Tp, contiguous_iterator_tag> 458 > {}; 459 #else 460 template <class _Tp> 461 struct __is_cpp17_contiguous_iterator : false_type {}; 462 #endif 463 464 // Any native pointer which is an iterator is also a contiguous iterator. 465 template <class _Up> 466 struct __is_cpp17_contiguous_iterator<_Up*> : true_type {}; 467 468 469 template <class _Iter> 470 class __wrap_iter; 471 472 template <class _Tp> 473 struct __is_exactly_cpp17_input_iterator 474 : public integral_constant<bool, 475 __has_iterator_category_convertible_to<_Tp, input_iterator_tag>::value && 476 !__has_iterator_category_convertible_to<_Tp, forward_iterator_tag>::value> {}; 477 478 template<class _InputIterator> 479 using __iter_value_type = typename iterator_traits<_InputIterator>::value_type; 480 481 template<class _InputIterator> 482 using __iter_key_type = typename remove_const<typename iterator_traits<_InputIterator>::value_type::first_type>::type; 483 484 template<class _InputIterator> 485 using __iter_mapped_type = typename iterator_traits<_InputIterator>::value_type::second_type; 486 487 template<class _InputIterator> 488 using __iter_to_alloc_type = pair< 489 typename add_const<typename iterator_traits<_InputIterator>::value_type::first_type>::type, 490 typename iterator_traits<_InputIterator>::value_type::second_type>; 491 492 _LIBCPP_END_NAMESPACE_STD 493 494 #endif // _LIBCPP___ITERATOR_ITERATOR_TRAITS_H 495