libstdc++
|
00001 // <experimental/any> -*- C++ -*- 00002 00003 // Copyright (C) 2014-2017 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 <= 201103L 00035 # include <bits/c++14_warning.h> 00036 #else 00037 00038 #include <typeinfo> 00039 #include <new> 00040 #include <utility> 00041 #include <type_traits> 00042 #include <experimental/bits/lfts_config.h> 00043 00044 namespace std _GLIBCXX_VISIBILITY(default) 00045 { 00046 namespace experimental 00047 { 00048 inline namespace fundamentals_v1 00049 { 00050 _GLIBCXX_BEGIN_NAMESPACE_VERSION 00051 00052 /** 00053 * @defgroup any Type-safe container of any type 00054 * @ingroup experimental 00055 * 00056 * A type-safe container for single values of value types, as 00057 * described in n3804 "Any Library Proposal (Revision 3)". 00058 * 00059 * @{ 00060 */ 00061 00062 #define __cpp_lib_experimental_any 201411 00063 00064 /** 00065 * @brief Exception class thrown by a failed @c any_cast 00066 * @ingroup exceptions 00067 */ 00068 class bad_any_cast : public bad_cast 00069 { 00070 public: 00071 virtual const char* what() const noexcept { return "bad any_cast"; } 00072 }; 00073 00074 [[gnu::noreturn]] inline void __throw_bad_any_cast() 00075 { 00076 #if __cpp_exceptions 00077 throw bad_any_cast{}; 00078 #else 00079 __builtin_abort(); 00080 #endif 00081 } 00082 00083 /** 00084 * @brief A type-safe container of any type. 00085 * 00086 * An @c any object's state is either empty or it stores a contained object 00087 * of CopyConstructible type. 00088 */ 00089 class any 00090 { 00091 // Holds either pointer to a heap object or the contained object itself. 00092 union _Storage 00093 { 00094 // This constructor intentionally doesn't initialize anything. 00095 _Storage() = default; 00096 00097 // Prevent trivial copies of this type, buffer might hold a non-POD. 00098 _Storage(const _Storage&) = delete; 00099 _Storage& operator=(const _Storage&) = delete; 00100 00101 void* _M_ptr; 00102 aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer; 00103 }; 00104 00105 template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>, 00106 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage)) 00107 && (alignof(_Tp) <= alignof(_Storage))> 00108 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>; 00109 00110 template<typename _Tp> 00111 struct _Manager_internal; // uses small-object optimization 00112 00113 template<typename _Tp> 00114 struct _Manager_external; // creates contained object on the heap 00115 00116 template<typename _Tp> 00117 using _Manager = conditional_t<_Internal<_Tp>::value, 00118 _Manager_internal<_Tp>, 00119 _Manager_external<_Tp>>; 00120 00121 template<typename _Tp, typename _Decayed = decay_t<_Tp>> 00122 using _Decay = enable_if_t<!is_same<_Decayed, any>::value, _Decayed>; 00123 00124 public: 00125 // construct/destruct 00126 00127 /// Default constructor, creates an empty object. 00128 any() noexcept : _M_manager(nullptr) { } 00129 00130 /// Copy constructor, copies the state of @p __other 00131 any(const any& __other) 00132 { 00133 if (__other.empty()) 00134 _M_manager = nullptr; 00135 else 00136 { 00137 _Arg __arg; 00138 __arg._M_any = this; 00139 __other._M_manager(_Op_clone, &__other, &__arg); 00140 } 00141 } 00142 00143 /** 00144 * @brief Move constructor, transfer the state from @p __other 00145 * 00146 * @post @c __other.empty() (this postcondition is a GNU extension) 00147 */ 00148 any(any&& __other) noexcept 00149 { 00150 if (__other.empty()) 00151 _M_manager = nullptr; 00152 else 00153 { 00154 _Arg __arg; 00155 __arg._M_any = this; 00156 __other._M_manager(_Op_xfer, &__other, &__arg); 00157 } 00158 } 00159 00160 /// Construct with a copy of @p __value as the contained object. 00161 template <typename _ValueType, typename _Tp = _Decay<_ValueType>, 00162 typename _Mgr = _Manager<_Tp>, 00163 typename enable_if<is_constructible<_Tp, _ValueType&&>::value, 00164 bool>::type = true> 00165 any(_ValueType&& __value) 00166 : _M_manager(&_Mgr::_S_manage) 00167 { 00168 _Mgr::_S_create(_M_storage, std::forward<_ValueType>(__value)); 00169 static_assert(is_copy_constructible<_Tp>::value, 00170 "The contained object must be CopyConstructible"); 00171 } 00172 00173 /// Construct with a copy of @p __value as the contained object. 00174 template <typename _ValueType, typename _Tp = _Decay<_ValueType>, 00175 typename _Mgr = _Manager<_Tp>, 00176 typename enable_if<!is_constructible<_Tp, _ValueType&&>::value, 00177 bool>::type = false> 00178 any(_ValueType&& __value) 00179 : _M_manager(&_Mgr::_S_manage) 00180 { 00181 _Mgr::_S_create(_M_storage, __value); 00182 static_assert(is_copy_constructible<_Tp>::value, 00183 "The contained object must be CopyConstructible"); 00184 } 00185 00186 /// Destructor, calls @c clear() 00187 ~any() { clear(); } 00188 00189 // assignments 00190 00191 /// Copy the state of another object. 00192 any& operator=(const any& __rhs) 00193 { 00194 *this = any(__rhs); 00195 return *this; 00196 } 00197 00198 /** 00199 * @brief Move assignment operator 00200 * 00201 * @post @c __rhs.empty() (not guaranteed for other implementations) 00202 */ 00203 any& operator=(any&& __rhs) noexcept 00204 { 00205 if (__rhs.empty()) 00206 clear(); 00207 else if (this != &__rhs) 00208 { 00209 clear(); 00210 _Arg __arg; 00211 __arg._M_any = this; 00212 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 00213 } 00214 return *this; 00215 } 00216 00217 /// Store a copy of @p __rhs as the contained object. 00218 template<typename _ValueType> 00219 enable_if_t<!is_same<any, decay_t<_ValueType>>::value, any&> 00220 operator=(_ValueType&& __rhs) 00221 { 00222 *this = any(std::forward<_ValueType>(__rhs)); 00223 return *this; 00224 } 00225 00226 // modifiers 00227 00228 /// If not empty, destroy the contained object. 00229 void clear() noexcept 00230 { 00231 if (!empty()) 00232 { 00233 _M_manager(_Op_destroy, this, nullptr); 00234 _M_manager = nullptr; 00235 } 00236 } 00237 00238 /// Exchange state with another object. 00239 void swap(any& __rhs) noexcept 00240 { 00241 if (empty() && __rhs.empty()) 00242 return; 00243 00244 if (!empty() && !__rhs.empty()) 00245 { 00246 if (this == &__rhs) 00247 return; 00248 00249 any __tmp; 00250 _Arg __arg; 00251 __arg._M_any = &__tmp; 00252 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 00253 __arg._M_any = &__rhs; 00254 _M_manager(_Op_xfer, this, &__arg); 00255 __arg._M_any = this; 00256 __tmp._M_manager(_Op_xfer, &__tmp, &__arg); 00257 } 00258 else 00259 { 00260 any* __empty = empty() ? this : &__rhs; 00261 any* __full = empty() ? &__rhs : this; 00262 _Arg __arg; 00263 __arg._M_any = __empty; 00264 __full->_M_manager(_Op_xfer, __full, &__arg); 00265 } 00266 } 00267 00268 // observers 00269 00270 /// Reports whether there is a contained object or not. 00271 bool empty() const noexcept { return _M_manager == nullptr; } 00272 00273 #if __cpp_rtti 00274 /// The @c typeid of the contained object, or @c typeid(void) if empty. 00275 const type_info& type() const noexcept 00276 { 00277 if (empty()) 00278 return typeid(void); 00279 _Arg __arg; 00280 _M_manager(_Op_get_type_info, this, &__arg); 00281 return *__arg._M_typeinfo; 00282 } 00283 #endif 00284 00285 template<typename _Tp> 00286 static constexpr bool __is_valid_cast() 00287 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; } 00288 00289 private: 00290 enum _Op { 00291 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer 00292 }; 00293 00294 union _Arg 00295 { 00296 void* _M_obj; 00297 const std::type_info* _M_typeinfo; 00298 any* _M_any; 00299 }; 00300 00301 void (*_M_manager)(_Op, const any*, _Arg*); 00302 _Storage _M_storage; 00303 00304 template<typename _Tp> 00305 friend void* __any_caster(const any* __any); 00306 00307 // Manage in-place contained object. 00308 template<typename _Tp> 00309 struct _Manager_internal 00310 { 00311 static void 00312 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 00313 00314 template<typename _Up> 00315 static void 00316 _S_create(_Storage& __storage, _Up&& __value) 00317 { 00318 void* __addr = &__storage._M_buffer; 00319 ::new (__addr) _Tp(std::forward<_Up>(__value)); 00320 } 00321 }; 00322 00323 // Manage external contained object. 00324 template<typename _Tp> 00325 struct _Manager_external 00326 { 00327 static void 00328 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 00329 00330 template<typename _Up> 00331 static void 00332 _S_create(_Storage& __storage, _Up&& __value) 00333 { 00334 __storage._M_ptr = new _Tp(std::forward<_Up>(__value)); 00335 } 00336 }; 00337 }; 00338 00339 /// Exchange the states of two @c any objects. 00340 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); } 00341 00342 /** 00343 * @brief Access the contained object. 00344 * 00345 * @tparam _ValueType A const-reference or CopyConstructible type. 00346 * @param __any The object to access. 00347 * @return The contained object. 00348 * @throw bad_any_cast If <code> 00349 * __any.type() != typeid(remove_reference_t<_ValueType>) 00350 * </code> 00351 */ 00352 template<typename _ValueType> 00353 inline _ValueType any_cast(const any& __any) 00354 { 00355 static_assert(any::__is_valid_cast<_ValueType>(), 00356 "Template argument must be a reference or CopyConstructible type"); 00357 auto __p = any_cast<add_const_t<remove_reference_t<_ValueType>>>(&__any); 00358 if (__p) 00359 return *__p; 00360 __throw_bad_any_cast(); 00361 } 00362 00363 /** 00364 * @brief Access the contained object. 00365 * 00366 * @tparam _ValueType A reference or CopyConstructible type. 00367 * @param __any The object to access. 00368 * @return The contained object. 00369 * @throw bad_any_cast If <code> 00370 * __any.type() != typeid(remove_reference_t<_ValueType>) 00371 * </code> 00372 * 00373 * @{ 00374 */ 00375 template<typename _ValueType> 00376 inline _ValueType any_cast(any& __any) 00377 { 00378 static_assert(any::__is_valid_cast<_ValueType>(), 00379 "Template argument must be a reference or CopyConstructible type"); 00380 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 00381 if (__p) 00382 return *__p; 00383 __throw_bad_any_cast(); 00384 } 00385 00386 template<typename _ValueType, 00387 typename enable_if<!is_move_constructible<_ValueType>::value 00388 || is_lvalue_reference<_ValueType>::value, 00389 bool>::type = true> 00390 inline _ValueType any_cast(any&& __any) 00391 { 00392 static_assert(any::__is_valid_cast<_ValueType>(), 00393 "Template argument must be a reference or CopyConstructible type"); 00394 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 00395 if (__p) 00396 return *__p; 00397 __throw_bad_any_cast(); 00398 } 00399 00400 template<typename _ValueType, 00401 typename enable_if<is_move_constructible<_ValueType>::value 00402 && !is_lvalue_reference<_ValueType>::value, 00403 bool>::type = false> 00404 inline _ValueType any_cast(any&& __any) 00405 { 00406 static_assert(any::__is_valid_cast<_ValueType>(), 00407 "Template argument must be a reference or CopyConstructible type"); 00408 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 00409 if (__p) 00410 return std::move(*__p); 00411 __throw_bad_any_cast(); 00412 } 00413 // @} 00414 00415 template<typename _Tp> 00416 void* __any_caster(const any* __any) 00417 { 00418 struct _None { }; 00419 using _Up = decay_t<_Tp>; 00420 using _Vp = conditional_t<is_copy_constructible<_Up>::value, _Up, _None>; 00421 if (__any->_M_manager != &any::_Manager<_Vp>::_S_manage) 00422 return nullptr; 00423 any::_Arg __arg; 00424 __any->_M_manager(any::_Op_access, __any, &__arg); 00425 return __arg._M_obj; 00426 } 00427 00428 /** 00429 * @brief Access the contained object. 00430 * 00431 * @tparam _ValueType The type of the contained object. 00432 * @param __any A pointer to the object to access. 00433 * @return The address of the contained object if <code> 00434 * __any != nullptr && __any.type() == typeid(_ValueType) 00435 * </code>, otherwise a null pointer. 00436 * 00437 * @{ 00438 */ 00439 template<typename _ValueType> 00440 inline const _ValueType* any_cast(const any* __any) noexcept 00441 { 00442 if (__any) 00443 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 00444 return nullptr; 00445 } 00446 00447 template<typename _ValueType> 00448 inline _ValueType* any_cast(any* __any) noexcept 00449 { 00450 if (__any) 00451 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 00452 return nullptr; 00453 } 00454 // @} 00455 00456 template<typename _Tp> 00457 void 00458 any::_Manager_internal<_Tp>:: 00459 _S_manage(_Op __which, const any* __any, _Arg* __arg) 00460 { 00461 // The contained object is in _M_storage._M_buffer 00462 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer); 00463 switch (__which) 00464 { 00465 case _Op_access: 00466 __arg->_M_obj = const_cast<_Tp*>(__ptr); 00467 break; 00468 case _Op_get_type_info: 00469 #if __cpp_rtti 00470 __arg->_M_typeinfo = &typeid(_Tp); 00471 #endif 00472 break; 00473 case _Op_clone: 00474 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr); 00475 __arg->_M_any->_M_manager = __any->_M_manager; 00476 break; 00477 case _Op_destroy: 00478 __ptr->~_Tp(); 00479 break; 00480 case _Op_xfer: 00481 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp 00482 (std::move(*const_cast<_Tp*>(__ptr))); 00483 __ptr->~_Tp(); 00484 __arg->_M_any->_M_manager = __any->_M_manager; 00485 const_cast<any*>(__any)->_M_manager = nullptr; 00486 break; 00487 } 00488 } 00489 00490 template<typename _Tp> 00491 void 00492 any::_Manager_external<_Tp>:: 00493 _S_manage(_Op __which, const any* __any, _Arg* __arg) 00494 { 00495 // The contained object is *_M_storage._M_ptr 00496 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr); 00497 switch (__which) 00498 { 00499 case _Op_access: 00500 __arg->_M_obj = const_cast<_Tp*>(__ptr); 00501 break; 00502 case _Op_get_type_info: 00503 #if __cpp_rtti 00504 __arg->_M_typeinfo = &typeid(_Tp); 00505 #endif 00506 break; 00507 case _Op_clone: 00508 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr); 00509 __arg->_M_any->_M_manager = __any->_M_manager; 00510 break; 00511 case _Op_destroy: 00512 delete __ptr; 00513 break; 00514 case _Op_xfer: 00515 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr; 00516 __arg->_M_any->_M_manager = __any->_M_manager; 00517 const_cast<any*>(__any)->_M_manager = nullptr; 00518 break; 00519 } 00520 } 00521 00522 // @} group any 00523 _GLIBCXX_END_NAMESPACE_VERSION 00524 } // namespace fundamentals_v1 00525 } // namespace experimental 00526 } // namespace std 00527 00528 #endif // C++14 00529 00530 #endif // _GLIBCXX_EXPERIMENTAL_ANY