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/usr/include/c++/11/experimental/any
$ cat -n /usr/include/c++/11/experimental/any 1 // <experimental/any> -*- C++ -*- 2 3 // Copyright (C) 2014-2021 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 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 #if __cplusplus >= 201402L 36 37 #include <typeinfo> 38 #include <new> 39 #include <utility> 40 #include <type_traits> 41 #include <experimental/bits/lfts_config.h> 42 43 namespace std _GLIBCXX_VISIBILITY(default) 44 { 45 _GLIBCXX_BEGIN_NAMESPACE_VERSION 46 47 namespace experimental 48 { 49 inline namespace fundamentals_v1 50 { 51 /** 52 * @defgroup any Type-safe container of any type 53 * @ingroup libfund-ts 54 * 55 * A type-safe container for single values of value types, as 56 * described in n3804 "Any Library Proposal (Revision 3)". 57 * 58 * @{ 59 */ 60 61 #define __cpp_lib_experimental_any 201411 62 63 /** 64 * @brief Exception class thrown by a failed @c any_cast 65 * @ingroup exceptions 66 */ 67 class bad_any_cast : public bad_cast 68 { 69 public: 70 virtual const char* what() const noexcept { return "bad any_cast"; } 71 }; 72 73 /// @cond undocumented 74 [[gnu::noreturn]] inline void __throw_bad_any_cast() 75 { 76 #if __cpp_exceptions 77 throw bad_any_cast{}; 78 #else 79 __builtin_abort(); 80 #endif 81 } 82 /// @endcond 83 84 /** 85 * @brief A type-safe container of any type. 86 * 87 * An @c any object's state is either empty or it stores a contained object 88 * of CopyConstructible type. 89 */ 90 class any 91 { 92 // Holds either pointer to a heap object or the contained object itself. 93 union _Storage 94 { 95 // This constructor intentionally doesn't initialize anything. 96 _Storage() = default; 97 98 // Prevent trivial copies of this type, buffer might hold a non-POD. 99 _Storage(const _Storage&) = delete; 100 _Storage& operator=(const _Storage&) = delete; 101 102 void* _M_ptr; 103 aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer; 104 }; 105 106 template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>, 107 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage)) 108 && (alignof(_Tp) <= alignof(_Storage))> 109 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>; 110 111 template<typename _Tp> 112 struct _Manager_internal; // uses small-object optimization 113 114 template<typename _Tp> 115 struct _Manager_external; // creates contained object on the heap 116 117 template<typename _Tp> 118 using _Manager = conditional_t<_Internal<_Tp>::value, 119 _Manager_internal<_Tp>, 120 _Manager_external<_Tp>>; 121 122 template<typename _Tp, typename _Decayed = decay_t<_Tp>> 123 using _Decay = enable_if_t<!is_same<_Decayed, any>::value, _Decayed>; 124 125 public: 126 // construct/destruct 127 128 /// Default constructor, creates an empty object. 129 any() noexcept : _M_manager(nullptr) { } 130 131 /// Copy constructor, copies the state of @p __other 132 any(const any& __other) 133 { 134 if (__other.empty()) 135 _M_manager = nullptr; 136 else 137 { 138 _Arg __arg; 139 __arg._M_any = this; 140 __other._M_manager(_Op_clone, &__other, &__arg); 141 } 142 } 143 144 /** 145 * @brief Move constructor, transfer the state from @p __other 146 * 147 * @post @c __other.empty() (this postcondition is a GNU extension) 148 */ 149 any(any&& __other) noexcept 150 { 151 if (__other.empty()) 152 _M_manager = nullptr; 153 else 154 { 155 _Arg __arg; 156 __arg._M_any = this; 157 __other._M_manager(_Op_xfer, &__other, &__arg); 158 } 159 } 160 161 /// Construct with a copy of @p __value as the contained object. 162 template <typename _ValueType, typename _Tp = _Decay<_ValueType>, 163 typename _Mgr = _Manager<_Tp>, 164 typename enable_if<is_constructible<_Tp, _ValueType&&>::value, 165 bool>::type = true> 166 any(_ValueType&& __value) 167 : _M_manager(&_Mgr::_S_manage) 168 { 169 _Mgr::_S_create(_M_storage, std::forward<_ValueType>(__value)); 170 static_assert(is_copy_constructible<_Tp>::value, 171 "The contained object must be CopyConstructible"); 172 } 173 174 /// Construct with a copy of @p __value as the contained object. 175 template <typename _ValueType, typename _Tp = _Decay<_ValueType>, 176 typename _Mgr = _Manager<_Tp>, 177 typename enable_if<!is_constructible<_Tp, _ValueType&&>::value, 178 bool>::type = false> 179 any(_ValueType&& __value) 180 : _M_manager(&_Mgr::_S_manage) 181 { 182 _Mgr::_S_create(_M_storage, __value); 183 static_assert(is_copy_constructible<_Tp>::value, 184 "The contained object must be CopyConstructible"); 185 } 186 187 /// Destructor, calls @c clear() 188 ~any() { clear(); } 189 190 // assignments 191 192 /// Copy the state of another object. 193 any& operator=(const any& __rhs) 194 { 195 *this = any(__rhs); 196 return *this; 197 } 198 199 /** 200 * @brief Move assignment operator 201 * 202 * @post @c __rhs.empty() (not guaranteed for other implementations) 203 */ 204 any& operator=(any&& __rhs) noexcept 205 { 206 if (__rhs.empty()) 207 clear(); 208 else if (this != &__rhs) 209 { 210 clear(); 211 _Arg __arg; 212 __arg._M_any = this; 213 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 214 } 215 return *this; 216 } 217 218 /// Store a copy of @p __rhs as the contained object. 219 template<typename _ValueType> 220 enable_if_t<!is_same<any, decay_t<_ValueType>>::value, any&> 221 operator=(_ValueType&& __rhs) 222 { 223 *this = any(std::forward<_ValueType>(__rhs)); 224 return *this; 225 } 226 227 // modifiers 228 229 /// If not empty, destroy the contained object. 230 void clear() noexcept 231 { 232 if (!empty()) 233 { 234 _M_manager(_Op_destroy, this, nullptr); 235 _M_manager = nullptr; 236 } 237 } 238 239 /// Exchange state with another object. 240 void swap(any& __rhs) noexcept 241 { 242 if (empty() && __rhs.empty()) 243 return; 244 245 if (!empty() && !__rhs.empty()) 246 { 247 if (this == &__rhs) 248 return; 249 250 any __tmp; 251 _Arg __arg; 252 __arg._M_any = &__tmp; 253 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 254 __arg._M_any = &__rhs; 255 _M_manager(_Op_xfer, this, &__arg); 256 __arg._M_any = this; 257 __tmp._M_manager(_Op_xfer, &__tmp, &__arg); 258 } 259 else 260 { 261 any* __empty = empty() ? this : &__rhs; 262 any* __full = empty() ? &__rhs : this; 263 _Arg __arg; 264 __arg._M_any = __empty; 265 __full->_M_manager(_Op_xfer, __full, &__arg); 266 } 267 } 268 269 // observers 270 271 /// Reports whether there is a contained object or not. 272 _GLIBCXX_NODISCARD bool empty() const noexcept { return _M_manager == nullptr; } 273 274 #if __cpp_rtti 275 /// The @c typeid of the contained object, or @c typeid(void) if empty. 276 const type_info& type() const noexcept 277 { 278 if (empty()) 279 return typeid(void); 280 _Arg __arg; 281 _M_manager(_Op_get_type_info, this, &__arg); 282 return *__arg._M_typeinfo; 283 } 284 #endif 285 286 template<typename _Tp> 287 static constexpr bool __is_valid_cast() 288 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; } 289 290 private: 291 enum _Op { 292 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer 293 }; 294 295 union _Arg 296 { 297 void* _M_obj; 298 const std::type_info* _M_typeinfo; 299 any* _M_any; 300 }; 301 302 void (*_M_manager)(_Op, const any*, _Arg*); 303 _Storage _M_storage; 304 305 template<typename _Tp> 306 friend enable_if_t<is_object<_Tp>::value, void*> 307 __any_caster(const any* __any); 308 309 // Manage in-place contained object. 310 template<typename _Tp> 311 struct _Manager_internal 312 { 313 static void 314 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 315 316 template<typename _Up> 317 static void 318 _S_create(_Storage& __storage, _Up&& __value) 319 { 320 void* __addr = &__storage._M_buffer; 321 ::new (__addr) _Tp(std::forward<_Up>(__value)); 322 } 323 }; 324 325 // Manage external contained object. 326 template<typename _Tp> 327 struct _Manager_external 328 { 329 static void 330 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 331 332 template<typename _Up> 333 static void 334 _S_create(_Storage& __storage, _Up&& __value) 335 { 336 __storage._M_ptr = new _Tp(std::forward<_Up>(__value)); 337 } 338 }; 339 }; 340 341 /// Exchange the states of two @c any objects. 342 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); } 343 344 /** 345 * @brief Access the contained object. 346 * 347 * @tparam _ValueType A const-reference or CopyConstructible type. 348 * @param __any The object to access. 349 * @return The contained object. 350 * @throw bad_any_cast If <code> 351 * __any.type() != typeid(remove_reference_t<_ValueType>) 352 * </code> 353 */ 354 template<typename _ValueType> 355 inline _ValueType any_cast(const any& __any) 356 { 357 static_assert(any::__is_valid_cast<_ValueType>(), 358 "Template argument must be a reference or CopyConstructible type"); 359 auto __p = any_cast<add_const_t<remove_reference_t<_ValueType>>>(&__any); 360 if (__p) 361 return *__p; 362 __throw_bad_any_cast(); 363 } 364 365 /** 366 * @brief Access the contained object. 367 * 368 * @tparam _ValueType A reference or CopyConstructible type. 369 * @param __any The object to access. 370 * @return The contained object. 371 * @throw bad_any_cast If <code> 372 * __any.type() != typeid(remove_reference_t<_ValueType>) 373 * </code> 374 * 375 * @{ 376 */ 377 template<typename _ValueType> 378 inline _ValueType any_cast(any& __any) 379 { 380 static_assert(any::__is_valid_cast<_ValueType>(), 381 "Template argument must be a reference or CopyConstructible type"); 382 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 383 if (__p) 384 return *__p; 385 __throw_bad_any_cast(); 386 } 387 388 template<typename _ValueType, 389 typename enable_if<!is_move_constructible<_ValueType>::value 390 || is_lvalue_reference<_ValueType>::value, 391 bool>::type = true> 392 inline _ValueType any_cast(any&& __any) 393 { 394 static_assert(any::__is_valid_cast<_ValueType>(), 395 "Template argument must be a reference or CopyConstructible type"); 396 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 397 if (__p) 398 return *__p; 399 __throw_bad_any_cast(); 400 } 401 402 template<typename _ValueType, 403 typename enable_if<is_move_constructible<_ValueType>::value 404 && !is_lvalue_reference<_ValueType>::value, 405 bool>::type = false> 406 inline _ValueType any_cast(any&& __any) 407 { 408 static_assert(any::__is_valid_cast<_ValueType>(), 409 "Template argument must be a reference or CopyConstructible type"); 410 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 411 if (__p) 412 return std::move(*__p); 413 __throw_bad_any_cast(); 414 } 415 /// @} 416 417 /// @cond undocumented 418 template<typename _Tp> 419 enable_if_t<is_object<_Tp>::value, void*> 420 __any_caster(const any* __any) 421 { 422 // any_cast<T> returns non-null if __any->type() == typeid(T) and 423 // typeid(T) ignores cv-qualifiers so remove them: 424 using _Up = remove_cv_t<_Tp>; 425 // The contained value has a decayed type, so if decay_t<U> is not U, 426 // then it's not possible to have a contained value of type U. 427 using __does_not_decay = is_same<decay_t<_Up>, _Up>; 428 // Only copy constructible types can be used for contained values. 429 using __is_copyable = is_copy_constructible<_Up>; 430 // If the type _Tp could never be stored in an any we don't want to 431 // instantiate _Manager<_Tp>, so use _Manager<any::_Op> instead, which 432 // is explicitly specialized and has a no-op _S_manage function. 433 using _Vp = conditional_t<__and_<__does_not_decay, __is_copyable>::value, 434 _Up, any::_Op>; 435 // First try comparing function addresses, which works without RTTI 436 if (__any->_M_manager == &any::_Manager<_Vp>::_S_manage 437 #if __cpp_rtti 438 || __any->type() == typeid(_Tp) 439 #endif 440 ) 441 { 442 any::_Arg __arg; 443 __any->_M_manager(any::_Op_access, __any, &__arg); 444 return __arg._M_obj; 445 } 446 return nullptr; 447 } 448 449 // This overload exists so that std::any_cast<void(*)()>(a) is well-formed. 450 template<typename _Tp> 451 enable_if_t<!is_object<_Tp>::value, _Tp*> 452 __any_caster(const any*) noexcept 453 { return nullptr; } 454 /// @endcond 455 456 /** 457 * @brief Access the contained object. 458 * 459 * @tparam _ValueType The type of the contained object. 460 * @param __any A pointer to the object to access. 461 * @return The address of the contained object if <code> 462 * __any != nullptr && __any.type() == typeid(_ValueType) 463 * </code>, otherwise a null pointer. 464 * 465 * @{ 466 */ 467 template<typename _ValueType> 468 inline const _ValueType* any_cast(const any* __any) noexcept 469 { 470 if (__any) 471 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 472 return nullptr; 473 } 474 475 template<typename _ValueType> 476 inline _ValueType* any_cast(any* __any) noexcept 477 { 478 if (__any) 479 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 480 return nullptr; 481 } 482 /// @} 483 484 template<typename _Tp> 485 void 486 any::_Manager_internal<_Tp>:: 487 _S_manage(_Op __which, const any* __any, _Arg* __arg) 488 { 489 // The contained object is in _M_storage._M_buffer 490 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer); 491 switch (__which) 492 { 493 case _Op_access: 494 __arg->_M_obj = const_cast<_Tp*>(__ptr); 495 break; 496 case _Op_get_type_info: 497 #if __cpp_rtti 498 __arg->_M_typeinfo = &typeid(_Tp); 499 #endif 500 break; 501 case _Op_clone: 502 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr); 503 __arg->_M_any->_M_manager = __any->_M_manager; 504 break; 505 case _Op_destroy: 506 __ptr->~_Tp(); 507 break; 508 case _Op_xfer: 509 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp 510 (std::move(*const_cast<_Tp*>(__ptr))); 511 __ptr->~_Tp(); 512 __arg->_M_any->_M_manager = __any->_M_manager; 513 const_cast<any*>(__any)->_M_manager = nullptr; 514 break; 515 } 516 } 517 518 template<typename _Tp> 519 void 520 any::_Manager_external<_Tp>:: 521 _S_manage(_Op __which, const any* __any, _Arg* __arg) 522 { 523 // The contained object is *_M_storage._M_ptr 524 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr); 525 switch (__which) 526 { 527 case _Op_access: 528 __arg->_M_obj = const_cast<_Tp*>(__ptr); 529 break; 530 case _Op_get_type_info: 531 #if __cpp_rtti 532 __arg->_M_typeinfo = &typeid(_Tp); 533 #endif 534 break; 535 case _Op_clone: 536 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr); 537 __arg->_M_any->_M_manager = __any->_M_manager; 538 break; 539 case _Op_destroy: 540 delete __ptr; 541 break; 542 case _Op_xfer: 543 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr; 544 __arg->_M_any->_M_manager = __any->_M_manager; 545 const_cast<any*>(__any)->_M_manager = nullptr; 546 break; 547 } 548 } 549 550 // Dummy specialization used by __any_caster. 551 template<> 552 struct any::_Manager_internal<any::_Op> 553 { 554 static void 555 _S_manage(_Op, const any*, _Arg*) { } 556 }; 557 558 /// @} group any 559 } // namespace fundamentals_v1 560 } // namespace experimental 561 562 _GLIBCXX_END_NAMESPACE_VERSION 563 } // namespace std 564 565 #endif // C++14 566 567 #endif // _GLIBCXX_EXPERIMENTAL_ANY
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