1// <experimental/any> -*- C++ -*- 2 3// Copyright (C) 2014-2019 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 */ 28 29#ifndef _GLIBCXX_EXPERIMENTAL_ANY 30#define _GLIBCXX_EXPERIMENTAL_ANY 1 31 32#pragma GCC system_header 33 34#if __cplusplus >= 201402L 35 36#include <typeinfo> 37#include <new> 38#include <utility> 39#include <type_traits> 40#include <experimental/bits/lfts_config.h> 41 42namespace std _GLIBCXX_VISIBILITY(default) 43{ 44_GLIBCXX_BEGIN_NAMESPACE_VERSION 45 46namespace experimental 47{ 48inline namespace fundamentals_v1 49{ 50 /** 51 * @defgroup any Type-safe container of any type 52 * @ingroup experimental 53 * 54 * A type-safe container for single values of value types, as 55 * described in n3804 "Any Library Proposal (Revision 3)". 56 * 57 * @{ 58 */ 59 60#define __cpp_lib_experimental_any 201411 61 62 /** 63 * @brief Exception class thrown by a failed @c any_cast 64 * @ingroup exceptions 65 */ 66 class bad_any_cast : public bad_cast 67 { 68 public: 69 virtual const char* what() const noexcept { return "bad any_cast"; } 70 }; 71 72 [[gnu::noreturn]] inline void __throw_bad_any_cast() 73 { 74#if __cpp_exceptions 75 throw bad_any_cast{}; 76#else 77 __builtin_abort(); 78#endif 79 } 80 81 /** 82 * @brief A type-safe container of any type. 83 * 84 * An @c any object's state is either empty or it stores a contained object 85 * of CopyConstructible type. 86 */ 87 class any 88 { 89 // Holds either pointer to a heap object or the contained object itself. 90 union _Storage 91 { 92 // This constructor intentionally doesn't initialize anything. 93 _Storage() = default; 94 95 // Prevent trivial copies of this type, buffer might hold a non-POD. 96 _Storage(const _Storage&) = delete; 97 _Storage& operator=(const _Storage&) = delete; 98 99 void* _M_ptr; 100 aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer; 101 }; 102 103 template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>, 104 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage)) 105 && (alignof(_Tp) <= alignof(_Storage))> 106 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>; 107 108 template<typename _Tp> 109 struct _Manager_internal; // uses small-object optimization 110 111 template<typename _Tp> 112 struct _Manager_external; // creates contained object on the heap 113 114 template<typename _Tp> 115 using _Manager = conditional_t<_Internal<_Tp>::value, 116 _Manager_internal<_Tp>, 117 _Manager_external<_Tp>>; 118 119 template<typename _Tp, typename _Decayed = decay_t<_Tp>> 120 using _Decay = enable_if_t<!is_same<_Decayed, any>::value, _Decayed>; 121 122 public: 123 // construct/destruct 124 125 /// Default constructor, creates an empty object. 126 any() noexcept : _M_manager(nullptr) { } 127 128 /// Copy constructor, copies the state of @p __other 129 any(const any& __other) 130 { 131 if (__other.empty()) 132 _M_manager = nullptr; 133 else 134 { 135 _Arg __arg; 136 __arg._M_any = this; 137 __other._M_manager(_Op_clone, &__other, &__arg); 138 } 139 } 140 141 /** 142 * @brief Move constructor, transfer the state from @p __other 143 * 144 * @post @c __other.empty() (this postcondition is a GNU extension) 145 */ 146 any(any&& __other) noexcept 147 { 148 if (__other.empty()) 149 _M_manager = nullptr; 150 else 151 { 152 _Arg __arg; 153 __arg._M_any = this; 154 __other._M_manager(_Op_xfer, &__other, &__arg); 155 } 156 } 157 158 /// Construct with a copy of @p __value as the contained object. 159 template <typename _ValueType, typename _Tp = _Decay<_ValueType>, 160 typename _Mgr = _Manager<_Tp>, 161 typename enable_if<is_constructible<_Tp, _ValueType&&>::value, 162 bool>::type = true> 163 any(_ValueType&& __value) 164 : _M_manager(&_Mgr::_S_manage) 165 { 166 _Mgr::_S_create(_M_storage, std::forward<_ValueType>(__value)); 167 static_assert(is_copy_constructible<_Tp>::value, 168 "The contained object must be CopyConstructible"); 169 } 170 171 /// Construct with a copy of @p __value as the contained object. 172 template <typename _ValueType, typename _Tp = _Decay<_ValueType>, 173 typename _Mgr = _Manager<_Tp>, 174 typename enable_if<!is_constructible<_Tp, _ValueType&&>::value, 175 bool>::type = false> 176 any(_ValueType&& __value) 177 : _M_manager(&_Mgr::_S_manage) 178 { 179 _Mgr::_S_create(_M_storage, __value); 180 static_assert(is_copy_constructible<_Tp>::value, 181 "The contained object must be CopyConstructible"); 182 } 183 184 /// Destructor, calls @c clear() 185 ~any() { clear(); } 186 187 // assignments 188 189 /// Copy the state of another object. 190 any& operator=(const any& __rhs) 191 { 192 *this = any(__rhs); 193 return *this; 194 } 195 196 /** 197 * @brief Move assignment operator 198 * 199 * @post @c __rhs.empty() (not guaranteed for other implementations) 200 */ 201 any& operator=(any&& __rhs) noexcept 202 { 203 if (__rhs.empty()) 204 clear(); 205 else if (this != &__rhs) 206 { 207 clear(); 208 _Arg __arg; 209 __arg._M_any = this; 210 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 211 } 212 return *this; 213 } 214 215 /// Store a copy of @p __rhs as the contained object. 216 template<typename _ValueType> 217 enable_if_t<!is_same<any, decay_t<_ValueType>>::value, any&> 218 operator=(_ValueType&& __rhs) 219 { 220 *this = any(std::forward<_ValueType>(__rhs)); 221 return *this; 222 } 223 224 // modifiers 225 226 /// If not empty, destroy the contained object. 227 void clear() noexcept 228 { 229 if (!empty()) 230 { 231 _M_manager(_Op_destroy, this, nullptr); 232 _M_manager = nullptr; 233 } 234 } 235 236 /// Exchange state with another object. 237 void swap(any& __rhs) noexcept 238 { 239 if (empty() && __rhs.empty()) 240 return; 241 242 if (!empty() && !__rhs.empty()) 243 { 244 if (this == &__rhs) 245 return; 246 247 any __tmp; 248 _Arg __arg; 249 __arg._M_any = &__tmp; 250 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 251 __arg._M_any = &__rhs; 252 _M_manager(_Op_xfer, this, &__arg); 253 __arg._M_any = this; 254 __tmp._M_manager(_Op_xfer, &__tmp, &__arg); 255 } 256 else 257 { 258 any* __empty = empty() ? this : &__rhs; 259 any* __full = empty() ? &__rhs : this; 260 _Arg __arg; 261 __arg._M_any = __empty; 262 __full->_M_manager(_Op_xfer, __full, &__arg); 263 } 264 } 265 266 // observers 267 268 /// Reports whether there is a contained object or not. 269 _GLIBCXX_NODISCARD bool empty() const noexcept { return _M_manager == nullptr; } 270 271#if __cpp_rtti 272 /// The @c typeid of the contained object, or @c typeid(void) if empty. 273 const type_info& type() const noexcept 274 { 275 if (empty()) 276 return typeid(void); 277 _Arg __arg; 278 _M_manager(_Op_get_type_info, this, &__arg); 279 return *__arg._M_typeinfo; 280 } 281#endif 282 283 template<typename _Tp> 284 static constexpr bool __is_valid_cast() 285 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; } 286 287 private: 288 enum _Op { 289 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer 290 }; 291 292 union _Arg 293 { 294 void* _M_obj; 295 const std::type_info* _M_typeinfo; 296 any* _M_any; 297 }; 298 299 void (*_M_manager)(_Op, const any*, _Arg*); 300 _Storage _M_storage; 301 302 template<typename _Tp> 303 friend enable_if_t<is_object<_Tp>::value, void*> 304 __any_caster(const any* __any); 305 306 // Manage in-place contained object. 307 template<typename _Tp> 308 struct _Manager_internal 309 { 310 static void 311 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 312 313 template<typename _Up> 314 static void 315 _S_create(_Storage& __storage, _Up&& __value) 316 { 317 void* __addr = &__storage._M_buffer; 318 ::new (__addr) _Tp(std::forward<_Up>(__value)); 319 } 320 }; 321 322 // Manage external contained object. 323 template<typename _Tp> 324 struct _Manager_external 325 { 326 static void 327 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 328 329 template<typename _Up> 330 static void 331 _S_create(_Storage& __storage, _Up&& __value) 332 { 333 __storage._M_ptr = new _Tp(std::forward<_Up>(__value)); 334 } 335 }; 336 }; 337 338 /// Exchange the states of two @c any objects. 339 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); } 340 341 /** 342 * @brief Access the contained object. 343 * 344 * @tparam _ValueType A const-reference or CopyConstructible type. 345 * @param __any The object to access. 346 * @return The contained object. 347 * @throw bad_any_cast If <code> 348 * __any.type() != typeid(remove_reference_t<_ValueType>) 349 * </code> 350 */ 351 template<typename _ValueType> 352 inline _ValueType any_cast(const any& __any) 353 { 354 static_assert(any::__is_valid_cast<_ValueType>(), 355 "Template argument must be a reference or CopyConstructible type"); 356 auto __p = any_cast<add_const_t<remove_reference_t<_ValueType>>>(&__any); 357 if (__p) 358 return *__p; 359 __throw_bad_any_cast(); 360 } 361 362 /** 363 * @brief Access the contained object. 364 * 365 * @tparam _ValueType A reference or CopyConstructible type. 366 * @param __any The object to access. 367 * @return The contained object. 368 * @throw bad_any_cast If <code> 369 * __any.type() != typeid(remove_reference_t<_ValueType>) 370 * </code> 371 * 372 * @{ 373 */ 374 template<typename _ValueType> 375 inline _ValueType any_cast(any& __any) 376 { 377 static_assert(any::__is_valid_cast<_ValueType>(), 378 "Template argument must be a reference or CopyConstructible type"); 379 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 380 if (__p) 381 return *__p; 382 __throw_bad_any_cast(); 383 } 384 385 template<typename _ValueType, 386 typename enable_if<!is_move_constructible<_ValueType>::value 387 || is_lvalue_reference<_ValueType>::value, 388 bool>::type = true> 389 inline _ValueType any_cast(any&& __any) 390 { 391 static_assert(any::__is_valid_cast<_ValueType>(), 392 "Template argument must be a reference or CopyConstructible type"); 393 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 394 if (__p) 395 return *__p; 396 __throw_bad_any_cast(); 397 } 398 399 template<typename _ValueType, 400 typename enable_if<is_move_constructible<_ValueType>::value 401 && !is_lvalue_reference<_ValueType>::value, 402 bool>::type = false> 403 inline _ValueType any_cast(any&& __any) 404 { 405 static_assert(any::__is_valid_cast<_ValueType>(), 406 "Template argument must be a reference or CopyConstructible type"); 407 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 408 if (__p) 409 return std::move(*__p); 410 __throw_bad_any_cast(); 411 } 412 /// @} 413 414 /// @cond undocumented 415 template<typename _Tp> 416 enable_if_t<is_object<_Tp>::value, void*> 417 __any_caster(const any* __any) 418 { 419 // any_cast<T> returns non-null if __any->type() == typeid(T) and 420 // typeid(T) ignores cv-qualifiers so remove them: 421 using _Up = remove_cv_t<_Tp>; 422 // The contained value has a decayed type, so if decay_t<U> is not U, 423 // then it's not possible to have a contained value of type U. 424 using __does_not_decay = is_same<decay_t<_Up>, _Up>; 425 // Only copy constructible types can be used for contained values. 426 using __is_copyable = is_copy_constructible<_Up>; 427 // If the type _Tp could never be stored in an any we don't want to 428 // instantiate _Manager<_Tp>, so use _Manager<any::_Op> instead, which 429 // is explicitly specialized and has a no-op _S_manage function. 430 using _Vp = conditional_t<__and_<__does_not_decay, __is_copyable>::value, 431 _Up, any::_Op>; 432 // First try comparing function addresses, which works without RTTI 433 if (__any->_M_manager == &any::_Manager<_Vp>::_S_manage 434#if __cpp_rtti 435 || __any->type() == typeid(_Tp) 436#endif 437 ) 438 { 439 any::_Arg __arg; 440 __any->_M_manager(any::_Op_access, __any, &__arg); 441 return __arg._M_obj; 442 } 443 return nullptr; 444 } 445 446 // This overload exists so that std::any_cast<void(*)()>(a) is well-formed. 447 template<typename _Tp> 448 enable_if_t<!is_object<_Tp>::value, _Tp*> 449 __any_caster(const any*) noexcept 450 { return nullptr; } 451 /// @endcond 452 453 /** 454 * @brief Access the contained object. 455 * 456 * @tparam _ValueType The type of the contained object. 457 * @param __any A pointer to the object to access. 458 * @return The address of the contained object if <code> 459 * __any != nullptr && __any.type() == typeid(_ValueType) 460 * </code>, otherwise a null pointer. 461 * 462 * @{ 463 */ 464 template<typename _ValueType> 465 inline const _ValueType* any_cast(const any* __any) noexcept 466 { 467 if (__any) 468 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 469 return nullptr; 470 } 471 472 template<typename _ValueType> 473 inline _ValueType* any_cast(any* __any) noexcept 474 { 475 if (__any) 476 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 477 return nullptr; 478 } 479 /// @} 480 481 template<typename _Tp> 482 void 483 any::_Manager_internal<_Tp>:: 484 _S_manage(_Op __which, const any* __any, _Arg* __arg) 485 { 486 // The contained object is in _M_storage._M_buffer 487 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer); 488 switch (__which) 489 { 490 case _Op_access: 491 __arg->_M_obj = const_cast<_Tp*>(__ptr); 492 break; 493 case _Op_get_type_info: 494#if __cpp_rtti 495 __arg->_M_typeinfo = &typeid(_Tp); 496#endif 497 break; 498 case _Op_clone: 499 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr); 500 __arg->_M_any->_M_manager = __any->_M_manager; 501 break; 502 case _Op_destroy: 503 __ptr->~_Tp(); 504 break; 505 case _Op_xfer: 506 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp 507 (std::move(*const_cast<_Tp*>(__ptr))); 508 __ptr->~_Tp(); 509 __arg->_M_any->_M_manager = __any->_M_manager; 510 const_cast<any*>(__any)->_M_manager = nullptr; 511 break; 512 } 513 } 514 515 template<typename _Tp> 516 void 517 any::_Manager_external<_Tp>:: 518 _S_manage(_Op __which, const any* __any, _Arg* __arg) 519 { 520 // The contained object is *_M_storage._M_ptr 521 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr); 522 switch (__which) 523 { 524 case _Op_access: 525 __arg->_M_obj = const_cast<_Tp*>(__ptr); 526 break; 527 case _Op_get_type_info: 528#if __cpp_rtti 529 __arg->_M_typeinfo = &typeid(_Tp); 530#endif 531 break; 532 case _Op_clone: 533 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr); 534 __arg->_M_any->_M_manager = __any->_M_manager; 535 break; 536 case _Op_destroy: 537 delete __ptr; 538 break; 539 case _Op_xfer: 540 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr; 541 __arg->_M_any->_M_manager = __any->_M_manager; 542 const_cast<any*>(__any)->_M_manager = nullptr; 543 break; 544 } 545 } 546 547 // Dummy specialization used by __any_caster. 548 template<> 549 struct any::_Manager_internal<any::_Op> 550 { 551 static void 552 _S_manage(_Op, const any*, _Arg*) { } 553 }; 554 555 /// @} group any 556} // namespace fundamentals_v1 557} // namespace experimental 558 559_GLIBCXX_END_NAMESPACE_VERSION 560} // namespace std 561 562#endif // C++14 563 564#endif // _GLIBCXX_EXPERIMENTAL_ANY 565