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/usr/include/c++/13/experimental/any
$ cat -n /usr/include/c++/13/experimental/any 1 // <experimental/any> -*- C++ -*- 2 3 // Copyright (C) 2014-2023 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 experimental/any 26 * This is a TS C++ Library header. 27 * @ingroup libfund-ts 28 */ 29 30 #ifndef _GLIBCXX_EXPERIMENTAL_ANY 31 #define _GLIBCXX_EXPERIMENTAL_ANY 1 32 33 #pragma GCC system_header 34 35 #include <bits/requires_hosted.h> // experimental is currently omitted 36 37 #if __cplusplus >= 201402L 38 39 #include <typeinfo> 40 #include <new> 41 #include <type_traits> 42 #include <bits/move.h> 43 #include <experimental/bits/lfts_config.h> 44 45 namespace std _GLIBCXX_VISIBILITY(default) 46 { 47 _GLIBCXX_BEGIN_NAMESPACE_VERSION 48 49 namespace experimental 50 { 51 inline namespace fundamentals_v1 52 { 53 /** 54 * @defgroup any Type-safe container of any type 55 * @ingroup libfund-ts 56 * 57 * A type-safe container for single values of value types, as 58 * described in n3804 "Any Library Proposal (Revision 3)". 59 * 60 * @{ 61 */ 62 63 #define __cpp_lib_experimental_any 201411 64 65 /** 66 * @brief Exception class thrown by a failed @c any_cast 67 * @ingroup exceptions 68 */ 69 class bad_any_cast : public bad_cast 70 { 71 public: 72 virtual const char* what() const noexcept { return "bad any_cast"; } 73 }; 74 75 /// @cond undocumented 76 [[gnu::noreturn]] inline void __throw_bad_any_cast() 77 { 78 #if __cpp_exceptions 79 throw bad_any_cast{}; 80 #else 81 __builtin_abort(); 82 #endif 83 } 84 /// @endcond 85 86 /** 87 * @brief A type-safe container of any type. 88 * 89 * An @c any object's state is either empty or it stores a contained object 90 * of CopyConstructible type. 91 */ 92 class any 93 { 94 // Holds either pointer to a heap object or the contained object itself. 95 union _Storage 96 { 97 // This constructor intentionally doesn't initialize anything. 98 _Storage() = default; 99 100 // Prevent trivial copies of this type, buffer might hold a non-POD. 101 _Storage(const _Storage&) = delete; 102 _Storage& operator=(const _Storage&) = delete; 103 104 void* _M_ptr; 105 aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer; 106 }; 107 108 template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>, 109 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage)) 110 && (alignof(_Tp) <= alignof(_Storage))> 111 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>; 112 113 template<typename _Tp> 114 struct _Manager_internal; // uses small-object optimization 115 116 template<typename _Tp> 117 struct _Manager_external; // creates contained object on the heap 118 119 template<typename _Tp> 120 using _Manager = __conditional_t<_Internal<_Tp>::value, 121 _Manager_internal<_Tp>, 122 _Manager_external<_Tp>>; 123 124 template<typename _Tp, typename _Decayed = decay_t<_Tp>> 125 using _Decay = enable_if_t<!is_same<_Decayed, any>::value, _Decayed>; 126 127 public: 128 // construct/destruct 129 130 /// Default constructor, creates an empty object. 131 any() noexcept : _M_manager(nullptr) { } 132 133 /// Copy constructor, copies the state of @p __other 134 any(const any& __other) 135 { 136 if (__other.empty()) 137 _M_manager = nullptr; 138 else 139 { 140 _Arg __arg; 141 __arg._M_any = this; 142 __other._M_manager(_Op_clone, &__other, &__arg); 143 } 144 } 145 146 /** 147 * @brief Move constructor, transfer the state from @p __other 148 * 149 * @post @c __other.empty() (this postcondition is a GNU extension) 150 */ 151 any(any&& __other) noexcept 152 { 153 if (__other.empty()) 154 _M_manager = nullptr; 155 else 156 { 157 _Arg __arg; 158 __arg._M_any = this; 159 __other._M_manager(_Op_xfer, &__other, &__arg); 160 } 161 } 162 163 /// Construct with a copy of @p __value as the contained object. 164 template <typename _ValueType, typename _Tp = _Decay<_ValueType>, 165 typename _Mgr = _Manager<_Tp>, 166 typename enable_if<is_constructible<_Tp, _ValueType&&>::value, 167 bool>::type = true> 168 any(_ValueType&& __value) 169 : _M_manager(&_Mgr::_S_manage) 170 { 171 _Mgr::_S_create(_M_storage, std::forward<_ValueType>(__value)); 172 static_assert(is_copy_constructible<_Tp>::value, 173 "The contained object must be CopyConstructible"); 174 } 175 176 /// Construct with a copy of @p __value as the contained object. 177 template <typename _ValueType, typename _Tp = _Decay<_ValueType>, 178 typename _Mgr = _Manager<_Tp>, 179 typename enable_if<!is_constructible<_Tp, _ValueType&&>::value, 180 bool>::type = false> 181 any(_ValueType&& __value) 182 : _M_manager(&_Mgr::_S_manage) 183 { 184 _Mgr::_S_create(_M_storage, __value); 185 static_assert(is_copy_constructible<_Tp>::value, 186 "The contained object must be CopyConstructible"); 187 } 188 189 /// Destructor, calls @c clear() 190 ~any() { clear(); } 191 192 // assignments 193 194 /// Copy the state of another object. 195 any& operator=(const any& __rhs) 196 { 197 *this = any(__rhs); 198 return *this; 199 } 200 201 /** 202 * @brief Move assignment operator 203 * 204 * @post @c __rhs.empty() (not guaranteed for other implementations) 205 */ 206 any& operator=(any&& __rhs) noexcept 207 { 208 if (__rhs.empty()) 209 clear(); 210 else if (this != &__rhs) 211 { 212 clear(); 213 _Arg __arg; 214 __arg._M_any = this; 215 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 216 } 217 return *this; 218 } 219 220 /// Store a copy of @p __rhs as the contained object. 221 template<typename _ValueType> 222 enable_if_t<!is_same<any, decay_t<_ValueType>>::value, any&> 223 operator=(_ValueType&& __rhs) 224 { 225 *this = any(std::forward<_ValueType>(__rhs)); 226 return *this; 227 } 228 229 // modifiers 230 231 /// If not empty, destroy the contained object. 232 void clear() noexcept 233 { 234 if (!empty()) 235 { 236 _M_manager(_Op_destroy, this, nullptr); 237 _M_manager = nullptr; 238 } 239 } 240 241 /// Exchange state with another object. 242 void swap(any& __rhs) noexcept 243 { 244 if (empty() && __rhs.empty()) 245 return; 246 247 if (!empty() && !__rhs.empty()) 248 { 249 if (this == &__rhs) 250 return; 251 252 any __tmp; 253 _Arg __arg; 254 __arg._M_any = &__tmp; 255 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 256 __arg._M_any = &__rhs; 257 _M_manager(_Op_xfer, this, &__arg); 258 __arg._M_any = this; 259 __tmp._M_manager(_Op_xfer, &__tmp, &__arg); 260 } 261 else 262 { 263 any* __empty = empty() ? this : &__rhs; 264 any* __full = empty() ? &__rhs : this; 265 _Arg __arg; 266 __arg._M_any = __empty; 267 __full->_M_manager(_Op_xfer, __full, &__arg); 268 } 269 } 270 271 // observers 272 273 /// Reports whether there is a contained object or not. 274 _GLIBCXX_NODISCARD bool empty() const noexcept { return _M_manager == nullptr; } 275 276 #if __cpp_rtti 277 /// The @c typeid of the contained object, or @c typeid(void) if empty. 278 const type_info& type() const noexcept 279 { 280 if (empty()) 281 return typeid(void); 282 _Arg __arg; 283 _M_manager(_Op_get_type_info, this, &__arg); 284 return *__arg._M_typeinfo; 285 } 286 #endif 287 288 template<typename _Tp> 289 static constexpr bool __is_valid_cast() 290 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; } 291 292 private: 293 enum _Op { 294 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer 295 }; 296 297 union _Arg 298 { 299 void* _M_obj; 300 const std::type_info* _M_typeinfo; 301 any* _M_any; 302 }; 303 304 void (*_M_manager)(_Op, const any*, _Arg*); 305 _Storage _M_storage; 306 307 template<typename _Tp> 308 friend enable_if_t<is_object<_Tp>::value, void*> 309 __any_caster(const any* __any); 310 311 // Manage in-place contained object. 312 template<typename _Tp> 313 struct _Manager_internal 314 { 315 static void 316 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 317 318 template<typename _Up> 319 static void 320 _S_create(_Storage& __storage, _Up&& __value) 321 { 322 void* __addr = &__storage._M_buffer; 323 ::new (__addr) _Tp(std::forward<_Up>(__value)); 324 } 325 }; 326 327 // Manage external contained object. 328 template<typename _Tp> 329 struct _Manager_external 330 { 331 static void 332 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 333 334 template<typename _Up> 335 static void 336 _S_create(_Storage& __storage, _Up&& __value) 337 { 338 __storage._M_ptr = new _Tp(std::forward<_Up>(__value)); 339 } 340 }; 341 }; 342 343 /// Exchange the states of two @c any objects. 344 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); } 345 346 /** 347 * @brief Access the contained object. 348 * 349 * @tparam _ValueType A const-reference or CopyConstructible type. 350 * @param __any The object to access. 351 * @return The contained object. 352 * @throw bad_any_cast If <code> 353 * __any.type() != typeid(remove_reference_t<_ValueType>) 354 * </code> 355 */ 356 template<typename _ValueType> 357 inline _ValueType any_cast(const any& __any) 358 { 359 static_assert(any::__is_valid_cast<_ValueType>(), 360 "Template argument must be a reference or CopyConstructible type"); 361 auto __p = any_cast<add_const_t<remove_reference_t<_ValueType>>>(&__any); 362 if (__p) 363 return *__p; 364 __throw_bad_any_cast(); 365 } 366 367 /** 368 * @brief Access the contained object. 369 * 370 * @tparam _ValueType A reference or CopyConstructible type. 371 * @param __any The object to access. 372 * @return The contained object. 373 * @throw bad_any_cast If <code> 374 * __any.type() != typeid(remove_reference_t<_ValueType>) 375 * </code> 376 * 377 * @{ 378 */ 379 template<typename _ValueType> 380 inline _ValueType any_cast(any& __any) 381 { 382 static_assert(any::__is_valid_cast<_ValueType>(), 383 "Template argument must be a reference or CopyConstructible type"); 384 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 385 if (__p) 386 return *__p; 387 __throw_bad_any_cast(); 388 } 389 390 template<typename _ValueType, 391 typename enable_if<!is_move_constructible<_ValueType>::value 392 || is_lvalue_reference<_ValueType>::value, 393 bool>::type = true> 394 inline _ValueType any_cast(any&& __any) 395 { 396 static_assert(any::__is_valid_cast<_ValueType>(), 397 "Template argument must be a reference or CopyConstructible type"); 398 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 399 if (__p) 400 return *__p; 401 __throw_bad_any_cast(); 402 } 403 404 template<typename _ValueType, 405 typename enable_if<is_move_constructible<_ValueType>::value 406 && !is_lvalue_reference<_ValueType>::value, 407 bool>::type = false> 408 inline _ValueType any_cast(any&& __any) 409 { 410 static_assert(any::__is_valid_cast<_ValueType>(), 411 "Template argument must be a reference or CopyConstructible type"); 412 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 413 if (__p) 414 return std::move(*__p); 415 __throw_bad_any_cast(); 416 } 417 /// @} 418 419 /// @cond undocumented 420 template<typename _Tp> 421 enable_if_t<is_object<_Tp>::value, void*> 422 __any_caster(const any* __any) 423 { 424 // any_cast<T> returns non-null if __any->type() == typeid(T) and 425 // typeid(T) ignores cv-qualifiers so remove them: 426 using _Up = remove_cv_t<_Tp>; 427 // The contained value has a decayed type, so if decay_t<U> is not U, 428 // then it's not possible to have a contained value of type U. 429 using __does_not_decay = is_same<decay_t<_Up>, _Up>; 430 // Only copy constructible types can be used for contained values. 431 using __is_copyable = is_copy_constructible<_Up>; 432 // If the type _Tp could never be stored in an any we don't want to 433 // instantiate _Manager<_Tp>, so use _Manager<any::_Op> instead, which 434 // is explicitly specialized and has a no-op _S_manage function. 435 using _Vp = __conditional_t<__and_<__does_not_decay, __is_copyable>{}, 436 _Up, any::_Op>; 437 // First try comparing function addresses, which works without RTTI 438 if (__any->_M_manager == &any::_Manager<_Vp>::_S_manage 439 #if __cpp_rtti 440 || __any->type() == typeid(_Tp) 441 #endif 442 ) 443 { 444 any::_Arg __arg; 445 __any->_M_manager(any::_Op_access, __any, &__arg); 446 return __arg._M_obj; 447 } 448 return nullptr; 449 } 450 451 // This overload exists so that std::any_cast<void(*)()>(a) is well-formed. 452 template<typename _Tp> 453 enable_if_t<!is_object<_Tp>::value, _Tp*> 454 __any_caster(const any*) noexcept 455 { return nullptr; } 456 /// @endcond 457 458 /** 459 * @brief Access the contained object. 460 * 461 * @tparam _ValueType The type of the contained object. 462 * @param __any A pointer to the object to access. 463 * @return The address of the contained object if <code> 464 * __any != nullptr && __any.type() == typeid(_ValueType) 465 * </code>, otherwise a null pointer. 466 * 467 * @{ 468 */ 469 template<typename _ValueType> 470 inline const _ValueType* any_cast(const any* __any) noexcept 471 { 472 if (__any) 473 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 474 return nullptr; 475 } 476 477 template<typename _ValueType> 478 inline _ValueType* any_cast(any* __any) noexcept 479 { 480 if (__any) 481 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 482 return nullptr; 483 } 484 /// @} 485 486 template<typename _Tp> 487 void 488 any::_Manager_internal<_Tp>:: 489 _S_manage(_Op __which, const any* __any, _Arg* __arg) 490 { 491 // The contained object is in _M_storage._M_buffer 492 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer); 493 switch (__which) 494 { 495 case _Op_access: 496 __arg->_M_obj = const_cast<_Tp*>(__ptr); 497 break; 498 case _Op_get_type_info: 499 #if __cpp_rtti 500 __arg->_M_typeinfo = &typeid(_Tp); 501 #endif 502 break; 503 case _Op_clone: 504 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr); 505 __arg->_M_any->_M_manager = __any->_M_manager; 506 break; 507 case _Op_destroy: 508 __ptr->~_Tp(); 509 break; 510 case _Op_xfer: 511 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp 512 (std::move(*const_cast<_Tp*>(__ptr))); 513 __ptr->~_Tp(); 514 __arg->_M_any->_M_manager = __any->_M_manager; 515 const_cast<any*>(__any)->_M_manager = nullptr; 516 break; 517 } 518 } 519 520 template<typename _Tp> 521 void 522 any::_Manager_external<_Tp>:: 523 _S_manage(_Op __which, const any* __any, _Arg* __arg) 524 { 525 // The contained object is *_M_storage._M_ptr 526 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr); 527 switch (__which) 528 { 529 case _Op_access: 530 __arg->_M_obj = const_cast<_Tp*>(__ptr); 531 break; 532 case _Op_get_type_info: 533 #if __cpp_rtti 534 __arg->_M_typeinfo = &typeid(_Tp); 535 #endif 536 break; 537 case _Op_clone: 538 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr); 539 __arg->_M_any->_M_manager = __any->_M_manager; 540 break; 541 case _Op_destroy: 542 delete __ptr; 543 break; 544 case _Op_xfer: 545 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr; 546 __arg->_M_any->_M_manager = __any->_M_manager; 547 const_cast<any*>(__any)->_M_manager = nullptr; 548 break; 549 } 550 } 551 552 // Dummy specialization used by __any_caster. 553 template<> 554 struct any::_Manager_internal<any::_Op> 555 { 556 static void 557 _S_manage(_Op, const any*, _Arg*) { } 558 }; 559 560 /// @} group any 561 } // namespace fundamentals_v1 562 } // namespace experimental 563 564 _GLIBCXX_END_NAMESPACE_VERSION 565 } // namespace std 566 567 #endif // C++14 568 569 #endif // _GLIBCXX_EXPERIMENTAL_ANY
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