libstdc++
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00001 // <experimental/any> -*- C++ -*- 00002 00003 // Copyright (C) 2014-2019 Free Software Foundation, Inc. 00004 // 00005 // This file is part of the GNU ISO C++ Library. This library is free 00006 // software; you can redistribute it and/or modify it under the 00007 // terms of the GNU General Public License as published by the 00008 // Free Software Foundation; either version 3, or (at your option) 00009 // any later version. 00010 00011 // This library is distributed in the hope that it will be useful, 00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of 00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00014 // GNU General Public License for more details. 00015 00016 // Under Section 7 of GPL version 3, you are granted additional 00017 // permissions described in the GCC Runtime Library Exception, version 00018 // 3.1, as published by the Free Software Foundation. 00019 00020 // You should have received a copy of the GNU General Public License and 00021 // a copy of the GCC Runtime Library Exception along with this program; 00022 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see 00023 // <http://www.gnu.org/licenses/>. 00024 00025 /** @file experimental/any 00026 * This is a TS C++ Library header. 00027 */ 00028 00029 #ifndef _GLIBCXX_EXPERIMENTAL_ANY 00030 #define _GLIBCXX_EXPERIMENTAL_ANY 1 00031 00032 #pragma GCC system_header 00033 00034 #if __cplusplus >= 201402L 00035 00036 #include <typeinfo> 00037 #include <new> 00038 #include <utility> 00039 #include <type_traits> 00040 #include <experimental/bits/lfts_config.h> 00041 00042 namespace std _GLIBCXX_VISIBILITY(default) 00043 { 00044 _GLIBCXX_BEGIN_NAMESPACE_VERSION 00045 00046 namespace experimental 00047 { 00048 inline namespace fundamentals_v1 00049 { 00050 /** 00051 * @defgroup any Type-safe container of any type 00052 * @ingroup experimental 00053 * 00054 * A type-safe container for single values of value types, as 00055 * described in n3804 "Any Library Proposal (Revision 3)". 00056 * 00057 * @{ 00058 */ 00059 00060 #define __cpp_lib_experimental_any 201411 00061 00062 /** 00063 * @brief Exception class thrown by a failed @c any_cast 00064 * @ingroup exceptions 00065 */ 00066 class bad_any_cast : public bad_cast 00067 { 00068 public: 00069 virtual const char* what() const noexcept { return "bad any_cast"; } 00070 }; 00071 00072 [[gnu::noreturn]] inline void __throw_bad_any_cast() 00073 { 00074 #if __cpp_exceptions 00075 throw bad_any_cast{}; 00076 #else 00077 __builtin_abort(); 00078 #endif 00079 } 00080 00081 /** 00082 * @brief A type-safe container of any type. 00083 * 00084 * An @c any object's state is either empty or it stores a contained object 00085 * of CopyConstructible type. 00086 */ 00087 class any 00088 { 00089 // Holds either pointer to a heap object or the contained object itself. 00090 union _Storage 00091 { 00092 // This constructor intentionally doesn't initialize anything. 00093 _Storage() = default; 00094 00095 // Prevent trivial copies of this type, buffer might hold a non-POD. 00096 _Storage(const _Storage&) = delete; 00097 _Storage& operator=(const _Storage&) = delete; 00098 00099 void* _M_ptr; 00100 aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer; 00101 }; 00102 00103 template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>, 00104 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage)) 00105 && (alignof(_Tp) <= alignof(_Storage))> 00106 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>; 00107 00108 template<typename _Tp> 00109 struct _Manager_internal; // uses small-object optimization 00110 00111 template<typename _Tp> 00112 struct _Manager_external; // creates contained object on the heap 00113 00114 template<typename _Tp> 00115 using _Manager = conditional_t<_Internal<_Tp>::value, 00116 _Manager_internal<_Tp>, 00117 _Manager_external<_Tp>>; 00118 00119 template<typename _Tp, typename _Decayed = decay_t<_Tp>> 00120 using _Decay = enable_if_t<!is_same<_Decayed, any>::value, _Decayed>; 00121 00122 public: 00123 // construct/destruct 00124 00125 /// Default constructor, creates an empty object. 00126 any() noexcept : _M_manager(nullptr) { } 00127 00128 /// Copy constructor, copies the state of @p __other 00129 any(const any& __other) 00130 { 00131 if (__other.empty()) 00132 _M_manager = nullptr; 00133 else 00134 { 00135 _Arg __arg; 00136 __arg._M_any = this; 00137 __other._M_manager(_Op_clone, &__other, &__arg); 00138 } 00139 } 00140 00141 /** 00142 * @brief Move constructor, transfer the state from @p __other 00143 * 00144 * @post @c __other.empty() (this postcondition is a GNU extension) 00145 */ 00146 any(any&& __other) noexcept 00147 { 00148 if (__other.empty()) 00149 _M_manager = nullptr; 00150 else 00151 { 00152 _Arg __arg; 00153 __arg._M_any = this; 00154 __other._M_manager(_Op_xfer, &__other, &__arg); 00155 } 00156 } 00157 00158 /// Construct with a copy of @p __value as the contained object. 00159 template <typename _ValueType, typename _Tp = _Decay<_ValueType>, 00160 typename _Mgr = _Manager<_Tp>, 00161 typename enable_if<is_constructible<_Tp, _ValueType&&>::value, 00162 bool>::type = true> 00163 any(_ValueType&& __value) 00164 : _M_manager(&_Mgr::_S_manage) 00165 { 00166 _Mgr::_S_create(_M_storage, std::forward<_ValueType>(__value)); 00167 static_assert(is_copy_constructible<_Tp>::value, 00168 "The contained object must be CopyConstructible"); 00169 } 00170 00171 /// Construct with a copy of @p __value as the contained object. 00172 template <typename _ValueType, typename _Tp = _Decay<_ValueType>, 00173 typename _Mgr = _Manager<_Tp>, 00174 typename enable_if<!is_constructible<_Tp, _ValueType&&>::value, 00175 bool>::type = false> 00176 any(_ValueType&& __value) 00177 : _M_manager(&_Mgr::_S_manage) 00178 { 00179 _Mgr::_S_create(_M_storage, __value); 00180 static_assert(is_copy_constructible<_Tp>::value, 00181 "The contained object must be CopyConstructible"); 00182 } 00183 00184 /// Destructor, calls @c clear() 00185 ~any() { clear(); } 00186 00187 // assignments 00188 00189 /// Copy the state of another object. 00190 any& operator=(const any& __rhs) 00191 { 00192 *this = any(__rhs); 00193 return *this; 00194 } 00195 00196 /** 00197 * @brief Move assignment operator 00198 * 00199 * @post @c __rhs.empty() (not guaranteed for other implementations) 00200 */ 00201 any& operator=(any&& __rhs) noexcept 00202 { 00203 if (__rhs.empty()) 00204 clear(); 00205 else if (this != &__rhs) 00206 { 00207 clear(); 00208 _Arg __arg; 00209 __arg._M_any = this; 00210 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 00211 } 00212 return *this; 00213 } 00214 00215 /// Store a copy of @p __rhs as the contained object. 00216 template<typename _ValueType> 00217 enable_if_t<!is_same<any, decay_t<_ValueType>>::value, any&> 00218 operator=(_ValueType&& __rhs) 00219 { 00220 *this = any(std::forward<_ValueType>(__rhs)); 00221 return *this; 00222 } 00223 00224 // modifiers 00225 00226 /// If not empty, destroy the contained object. 00227 void clear() noexcept 00228 { 00229 if (!empty()) 00230 { 00231 _M_manager(_Op_destroy, this, nullptr); 00232 _M_manager = nullptr; 00233 } 00234 } 00235 00236 /// Exchange state with another object. 00237 void swap(any& __rhs) noexcept 00238 { 00239 if (empty() && __rhs.empty()) 00240 return; 00241 00242 if (!empty() && !__rhs.empty()) 00243 { 00244 if (this == &__rhs) 00245 return; 00246 00247 any __tmp; 00248 _Arg __arg; 00249 __arg._M_any = &__tmp; 00250 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 00251 __arg._M_any = &__rhs; 00252 _M_manager(_Op_xfer, this, &__arg); 00253 __arg._M_any = this; 00254 __tmp._M_manager(_Op_xfer, &__tmp, &__arg); 00255 } 00256 else 00257 { 00258 any* __empty = empty() ? this : &__rhs; 00259 any* __full = empty() ? &__rhs : this; 00260 _Arg __arg; 00261 __arg._M_any = __empty; 00262 __full->_M_manager(_Op_xfer, __full, &__arg); 00263 } 00264 } 00265 00266 // observers 00267 00268 /// Reports whether there is a contained object or not. 00269 _GLIBCXX_NODISCARD bool empty() const noexcept { return _M_manager == nullptr; } 00270 00271 #if __cpp_rtti 00272 /// The @c typeid of the contained object, or @c typeid(void) if empty. 00273 const type_info& type() const noexcept 00274 { 00275 if (empty()) 00276 return typeid(void); 00277 _Arg __arg; 00278 _M_manager(_Op_get_type_info, this, &__arg); 00279 return *__arg._M_typeinfo; 00280 } 00281 #endif 00282 00283 template<typename _Tp> 00284 static constexpr bool __is_valid_cast() 00285 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; } 00286 00287 private: 00288 enum _Op { 00289 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer 00290 }; 00291 00292 union _Arg 00293 { 00294 void* _M_obj; 00295 const std::type_info* _M_typeinfo; 00296 any* _M_any; 00297 }; 00298 00299 void (*_M_manager)(_Op, const any*, _Arg*); 00300 _Storage _M_storage; 00301 00302 template<typename _Tp> 00303 friend enable_if_t<is_object<_Tp>::value, void*> 00304 __any_caster(const any* __any); 00305 00306 // Manage in-place contained object. 00307 template<typename _Tp> 00308 struct _Manager_internal 00309 { 00310 static void 00311 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 00312 00313 template<typename _Up> 00314 static void 00315 _S_create(_Storage& __storage, _Up&& __value) 00316 { 00317 void* __addr = &__storage._M_buffer; 00318 ::new (__addr) _Tp(std::forward<_Up>(__value)); 00319 } 00320 }; 00321 00322 // Manage external contained object. 00323 template<typename _Tp> 00324 struct _Manager_external 00325 { 00326 static void 00327 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 00328 00329 template<typename _Up> 00330 static void 00331 _S_create(_Storage& __storage, _Up&& __value) 00332 { 00333 __storage._M_ptr = new _Tp(std::forward<_Up>(__value)); 00334 } 00335 }; 00336 }; 00337 00338 /// Exchange the states of two @c any objects. 00339 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); } 00340 00341 /** 00342 * @brief Access the contained object. 00343 * 00344 * @tparam _ValueType A const-reference or CopyConstructible type. 00345 * @param __any The object to access. 00346 * @return The contained object. 00347 * @throw bad_any_cast If <code> 00348 * __any.type() != typeid(remove_reference_t<_ValueType>) 00349 * </code> 00350 */ 00351 template<typename _ValueType> 00352 inline _ValueType any_cast(const any& __any) 00353 { 00354 static_assert(any::__is_valid_cast<_ValueType>(), 00355 "Template argument must be a reference or CopyConstructible type"); 00356 auto __p = any_cast<add_const_t<remove_reference_t<_ValueType>>>(&__any); 00357 if (__p) 00358 return *__p; 00359 __throw_bad_any_cast(); 00360 } 00361 00362 /** 00363 * @brief Access the contained object. 00364 * 00365 * @tparam _ValueType A reference or CopyConstructible type. 00366 * @param __any The object to access. 00367 * @return The contained object. 00368 * @throw bad_any_cast If <code> 00369 * __any.type() != typeid(remove_reference_t<_ValueType>) 00370 * </code> 00371 * 00372 * @{ 00373 */ 00374 template<typename _ValueType> 00375 inline _ValueType any_cast(any& __any) 00376 { 00377 static_assert(any::__is_valid_cast<_ValueType>(), 00378 "Template argument must be a reference or CopyConstructible type"); 00379 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 00380 if (__p) 00381 return *__p; 00382 __throw_bad_any_cast(); 00383 } 00384 00385 template<typename _ValueType, 00386 typename enable_if<!is_move_constructible<_ValueType>::value 00387 || is_lvalue_reference<_ValueType>::value, 00388 bool>::type = true> 00389 inline _ValueType any_cast(any&& __any) 00390 { 00391 static_assert(any::__is_valid_cast<_ValueType>(), 00392 "Template argument must be a reference or CopyConstructible type"); 00393 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 00394 if (__p) 00395 return *__p; 00396 __throw_bad_any_cast(); 00397 } 00398 00399 template<typename _ValueType, 00400 typename enable_if<is_move_constructible<_ValueType>::value 00401 && !is_lvalue_reference<_ValueType>::value, 00402 bool>::type = false> 00403 inline _ValueType any_cast(any&& __any) 00404 { 00405 static_assert(any::__is_valid_cast<_ValueType>(), 00406 "Template argument must be a reference or CopyConstructible type"); 00407 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 00408 if (__p) 00409 return std::move(*__p); 00410 __throw_bad_any_cast(); 00411 } 00412 // @} 00413 00414 /// @cond undocumented 00415 template<typename _Tp> 00416 enable_if_t<is_object<_Tp>::value, void*> 00417 __any_caster(const any* __any) 00418 { 00419 // any_cast<T> returns non-null if __any->type() == typeid(T) and 00420 // typeid(T) ignores cv-qualifiers so remove them: 00421 using _Up = remove_cv_t<_Tp>; 00422 // The contained value has a decayed type, so if decay_t<U> is not U, 00423 // then it's not possible to have a contained value of type U. 00424 using __does_not_decay = is_same<decay_t<_Up>, _Up>; 00425 // Only copy constructible types can be used for contained values. 00426 using __is_copyable = is_copy_constructible<_Up>; 00427 // If the type _Tp could never be stored in an any we don't want to 00428 // instantiate _Manager<_Tp>, so use _Manager<any::_Op> instead, which 00429 // is explicitly specialized and has a no-op _S_manage function. 00430 using _Vp = conditional_t<__and_<__does_not_decay, __is_copyable>::value, 00431 _Up, any::_Op>; 00432 // First try comparing function addresses, which works without RTTI 00433 if (__any->_M_manager == &any::_Manager<_Vp>::_S_manage 00434 #if __cpp_rtti 00435 || __any->type() == typeid(_Tp) 00436 #endif 00437 ) 00438 { 00439 any::_Arg __arg; 00440 __any->_M_manager(any::_Op_access, __any, &__arg); 00441 return __arg._M_obj; 00442 } 00443 return nullptr; 00444 } 00445 00446 // This overload exists so that std::any_cast<void(*)()>(a) is well-formed. 00447 template<typename _Tp> 00448 enable_if_t<!is_object<_Tp>::value, _Tp*> 00449 __any_caster(const any*) noexcept 00450 { return nullptr; } 00451 /// @endcond 00452 00453 /** 00454 * @brief Access the contained object. 00455 * 00456 * @tparam _ValueType The type of the contained object. 00457 * @param __any A pointer to the object to access. 00458 * @return The address of the contained object if <code> 00459 * __any != nullptr && __any.type() == typeid(_ValueType) 00460 * </code>, otherwise a null pointer. 00461 * 00462 * @{ 00463 */ 00464 template<typename _ValueType> 00465 inline const _ValueType* any_cast(const any* __any) noexcept 00466 { 00467 if (__any) 00468 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 00469 return nullptr; 00470 } 00471 00472 template<typename _ValueType> 00473 inline _ValueType* any_cast(any* __any) noexcept 00474 { 00475 if (__any) 00476 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 00477 return nullptr; 00478 } 00479 // @} 00480 00481 template<typename _Tp> 00482 void 00483 any::_Manager_internal<_Tp>:: 00484 _S_manage(_Op __which, const any* __any, _Arg* __arg) 00485 { 00486 // The contained object is in _M_storage._M_buffer 00487 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer); 00488 switch (__which) 00489 { 00490 case _Op_access: 00491 __arg->_M_obj = const_cast<_Tp*>(__ptr); 00492 break; 00493 case _Op_get_type_info: 00494 #if __cpp_rtti 00495 __arg->_M_typeinfo = &typeid(_Tp); 00496 #endif 00497 break; 00498 case _Op_clone: 00499 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr); 00500 __arg->_M_any->_M_manager = __any->_M_manager; 00501 break; 00502 case _Op_destroy: 00503 __ptr->~_Tp(); 00504 break; 00505 case _Op_xfer: 00506 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp 00507 (std::move(*const_cast<_Tp*>(__ptr))); 00508 __ptr->~_Tp(); 00509 __arg->_M_any->_M_manager = __any->_M_manager; 00510 const_cast<any*>(__any)->_M_manager = nullptr; 00511 break; 00512 } 00513 } 00514 00515 template<typename _Tp> 00516 void 00517 any::_Manager_external<_Tp>:: 00518 _S_manage(_Op __which, const any* __any, _Arg* __arg) 00519 { 00520 // The contained object is *_M_storage._M_ptr 00521 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr); 00522 switch (__which) 00523 { 00524 case _Op_access: 00525 __arg->_M_obj = const_cast<_Tp*>(__ptr); 00526 break; 00527 case _Op_get_type_info: 00528 #if __cpp_rtti 00529 __arg->_M_typeinfo = &typeid(_Tp); 00530 #endif 00531 break; 00532 case _Op_clone: 00533 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr); 00534 __arg->_M_any->_M_manager = __any->_M_manager; 00535 break; 00536 case _Op_destroy: 00537 delete __ptr; 00538 break; 00539 case _Op_xfer: 00540 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr; 00541 __arg->_M_any->_M_manager = __any->_M_manager; 00542 const_cast<any*>(__any)->_M_manager = nullptr; 00543 break; 00544 } 00545 } 00546 00547 // Dummy specialization used by __any_caster. 00548 template<> 00549 struct any::_Manager_internal<any::_Op> 00550 { 00551 static void 00552 _S_manage(_Op, const any*, _Arg*) { } 00553 }; 00554 00555 // @} group any 00556 } // namespace fundamentals_v1 00557 } // namespace experimental 00558 00559 _GLIBCXX_END_NAMESPACE_VERSION 00560 } // namespace std 00561 00562 #endif // C++14 00563 00564 #endif // _GLIBCXX_EXPERIMENTAL_ANY