1// <experimental/any> -*- C++ -*- 2 3// Copyright (C) 2014-2017 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{ 44namespace experimental 45{ 46inline namespace fundamentals_v1 47{ 48_GLIBCXX_BEGIN_NAMESPACE_VERSION 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 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 void* __any_caster(const any* __any); 304 305 // Manage in-place contained object. 306 template<typename _Tp> 307 struct _Manager_internal 308 { 309 static void 310 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 311 312 template<typename _Up> 313 static void 314 _S_create(_Storage& __storage, _Up&& __value) 315 { 316 void* __addr = &__storage._M_buffer; 317 ::new (__addr) _Tp(std::forward<_Up>(__value)); 318 } 319 }; 320 321 // Manage external contained object. 322 template<typename _Tp> 323 struct _Manager_external 324 { 325 static void 326 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 327 328 template<typename _Up> 329 static void 330 _S_create(_Storage& __storage, _Up&& __value) 331 { 332 __storage._M_ptr = new _Tp(std::forward<_Up>(__value)); 333 } 334 }; 335 }; 336 337 /// Exchange the states of two @c any objects. 338 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); } 339 340 /** 341 * @brief Access the contained object. 342 * 343 * @tparam _ValueType A const-reference or CopyConstructible type. 344 * @param __any The object to access. 345 * @return The contained object. 346 * @throw bad_any_cast If <code> 347 * __any.type() != typeid(remove_reference_t<_ValueType>) 348 * </code> 349 */ 350 template<typename _ValueType> 351 inline _ValueType any_cast(const any& __any) 352 { 353 static_assert(any::__is_valid_cast<_ValueType>(), 354 "Template argument must be a reference or CopyConstructible type"); 355 auto __p = any_cast<add_const_t<remove_reference_t<_ValueType>>>(&__any); 356 if (__p) 357 return *__p; 358 __throw_bad_any_cast(); 359 } 360 361 /** 362 * @brief Access the contained object. 363 * 364 * @tparam _ValueType A reference or CopyConstructible type. 365 * @param __any The object to access. 366 * @return The contained object. 367 * @throw bad_any_cast If <code> 368 * __any.type() != typeid(remove_reference_t<_ValueType>) 369 * </code> 370 * 371 * @{ 372 */ 373 template<typename _ValueType> 374 inline _ValueType any_cast(any& __any) 375 { 376 static_assert(any::__is_valid_cast<_ValueType>(), 377 "Template argument must be a reference or CopyConstructible type"); 378 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 379 if (__p) 380 return *__p; 381 __throw_bad_any_cast(); 382 } 383 384 template<typename _ValueType, 385 typename enable_if<!is_move_constructible<_ValueType>::value 386 || is_lvalue_reference<_ValueType>::value, 387 bool>::type = true> 388 inline _ValueType any_cast(any&& __any) 389 { 390 static_assert(any::__is_valid_cast<_ValueType>(), 391 "Template argument must be a reference or CopyConstructible type"); 392 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 393 if (__p) 394 return *__p; 395 __throw_bad_any_cast(); 396 } 397 398 template<typename _ValueType, 399 typename enable_if<is_move_constructible<_ValueType>::value 400 && !is_lvalue_reference<_ValueType>::value, 401 bool>::type = false> 402 inline _ValueType any_cast(any&& __any) 403 { 404 static_assert(any::__is_valid_cast<_ValueType>(), 405 "Template argument must be a reference or CopyConstructible type"); 406 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 407 if (__p) 408 return std::move(*__p); 409 __throw_bad_any_cast(); 410 } 411 // @} 412 413 template<typename _Tp> 414 void* __any_caster(const any* __any) 415 { 416 struct _None { }; 417 using _Up = decay_t<_Tp>; 418 using _Vp = conditional_t<is_copy_constructible<_Up>::value, _Up, _None>; 419 if (__any->_M_manager != &any::_Manager<_Vp>::_S_manage) 420 return nullptr; 421 any::_Arg __arg; 422 __any->_M_manager(any::_Op_access, __any, &__arg); 423 return __arg._M_obj; 424 } 425 426 /** 427 * @brief Access the contained object. 428 * 429 * @tparam _ValueType The type of the contained object. 430 * @param __any A pointer to the object to access. 431 * @return The address of the contained object if <code> 432 * __any != nullptr && __any.type() == typeid(_ValueType) 433 * </code>, otherwise a null pointer. 434 * 435 * @{ 436 */ 437 template<typename _ValueType> 438 inline const _ValueType* any_cast(const any* __any) noexcept 439 { 440 if (__any) 441 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 442 return nullptr; 443 } 444 445 template<typename _ValueType> 446 inline _ValueType* any_cast(any* __any) noexcept 447 { 448 if (__any) 449 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 450 return nullptr; 451 } 452 // @} 453 454 template<typename _Tp> 455 void 456 any::_Manager_internal<_Tp>:: 457 _S_manage(_Op __which, const any* __any, _Arg* __arg) 458 { 459 // The contained object is in _M_storage._M_buffer 460 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer); 461 switch (__which) 462 { 463 case _Op_access: 464 __arg->_M_obj = const_cast<_Tp*>(__ptr); 465 break; 466 case _Op_get_type_info: 467#if __cpp_rtti 468 __arg->_M_typeinfo = &typeid(_Tp); 469#endif 470 break; 471 case _Op_clone: 472 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr); 473 __arg->_M_any->_M_manager = __any->_M_manager; 474 break; 475 case _Op_destroy: 476 __ptr->~_Tp(); 477 break; 478 case _Op_xfer: 479 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp 480 (std::move(*const_cast<_Tp*>(__ptr))); 481 __ptr->~_Tp(); 482 __arg->_M_any->_M_manager = __any->_M_manager; 483 const_cast<any*>(__any)->_M_manager = nullptr; 484 break; 485 } 486 } 487 488 template<typename _Tp> 489 void 490 any::_Manager_external<_Tp>:: 491 _S_manage(_Op __which, const any* __any, _Arg* __arg) 492 { 493 // The contained object is *_M_storage._M_ptr 494 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr); 495 switch (__which) 496 { 497 case _Op_access: 498 __arg->_M_obj = const_cast<_Tp*>(__ptr); 499 break; 500 case _Op_get_type_info: 501#if __cpp_rtti 502 __arg->_M_typeinfo = &typeid(_Tp); 503#endif 504 break; 505 case _Op_clone: 506 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr); 507 __arg->_M_any->_M_manager = __any->_M_manager; 508 break; 509 case _Op_destroy: 510 delete __ptr; 511 break; 512 case _Op_xfer: 513 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr; 514 __arg->_M_any->_M_manager = __any->_M_manager; 515 const_cast<any*>(__any)->_M_manager = nullptr; 516 break; 517 } 518 } 519 520 // @} group any 521_GLIBCXX_END_NAMESPACE_VERSION 522} // namespace fundamentals_v1 523} // namespace experimental 524} // namespace std 525 526#endif // C++14 527 528#endif // _GLIBCXX_EXPERIMENTAL_ANY 529