libstdc++
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00001 // <experimental/any> -*- C++ -*- 00002 00003 // Copyright (C) 2014-2015 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 00043 namespace std _GLIBCXX_VISIBILITY(default) 00044 { 00045 namespace experimental 00046 { 00047 inline namespace fundamentals_v1 00048 { 00049 _GLIBCXX_BEGIN_NAMESPACE_VERSION 00050 00051 /** 00052 * @defgroup any Type-safe container of any type 00053 * @ingroup experimental 00054 * 00055 * A type-safe container for single values of value types, as 00056 * described in n3804 "Any Library Proposal (Revision 3)". 00057 * 00058 * @{ 00059 */ 00060 00061 #define __cpp_lib_experimental_any 201411 00062 00063 /** 00064 * @brief Exception class thrown by a failed @c any_cast 00065 * @ingroup exceptions 00066 */ 00067 class bad_any_cast : public bad_cast 00068 { 00069 public: 00070 virtual const char* what() const noexcept { return "bad any_cast"; } 00071 }; 00072 00073 [[gnu::noreturn]] inline void __throw_bad_any_cast() 00074 { 00075 #if __cpp_exceptions 00076 throw bad_any_cast{}; 00077 #else 00078 __builtin_abort(); 00079 #endif 00080 } 00081 00082 /** 00083 * @brief A type-safe container of any type. 00084 * 00085 * An @c any object's state is either empty or it stores a contained object 00086 * of CopyConstructible type. 00087 */ 00088 class any 00089 { 00090 // Holds either pointer to a heap object or the contained object itself. 00091 union _Storage 00092 { 00093 void* _M_ptr; 00094 std::aligned_storage<sizeof(_M_ptr), sizeof(_M_ptr)>::type _M_buffer; 00095 }; 00096 00097 template<typename _Tp, typename _Safe = is_trivially_copyable<_Tp>, 00098 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage))> 00099 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>; 00100 00101 template<typename _Tp> 00102 struct _Manager_internal; // uses small-object optimization 00103 00104 template<typename _Tp> 00105 struct _Manager_external; // creates contained object on the heap 00106 00107 template<typename _Tp> 00108 using _Manager = conditional_t<_Internal<_Tp>::value, 00109 _Manager_internal<_Tp>, 00110 _Manager_external<_Tp>>; 00111 00112 template<typename _Tp, typename _Decayed = decay_t<_Tp>> 00113 using _Decay = enable_if_t<!is_same<_Decayed, any>::value, _Decayed>; 00114 00115 public: 00116 // construct/destruct 00117 00118 /// Default constructor, creates an empty object. 00119 any() noexcept : _M_manager(nullptr) { } 00120 00121 /// Copy constructor, copies the state of @p __other 00122 any(const any& __other) : _M_manager(__other._M_manager) 00123 { 00124 if (!__other.empty()) 00125 { 00126 _Arg __arg; 00127 __arg._M_any = this; 00128 _M_manager(_Op_clone, &__other, &__arg); 00129 } 00130 } 00131 00132 /** 00133 * @brief Move constructor, transfer the state from @p __other 00134 * 00135 * @post @c __other.empty() (not guaranteed for other implementations) 00136 */ 00137 any(any&& __other) noexcept 00138 : _M_manager(__other._M_manager), 00139 _M_storage(__other._M_storage) 00140 { __other._M_manager = nullptr; } 00141 00142 /// Construct with a copy of @p __value as the contained object. 00143 template <typename _ValueType, typename _Tp = _Decay<_ValueType>, 00144 typename _Mgr = _Manager<_Tp>> 00145 any(_ValueType&& __value) 00146 : _M_manager(&_Mgr::_S_manage), 00147 _M_storage(_Mgr::_S_create(std::forward<_ValueType>(__value))) 00148 { 00149 static_assert(is_copy_constructible<_Tp>::value, 00150 "The contained object must be CopyConstructible"); 00151 } 00152 00153 /// Destructor, calls @c clear() 00154 ~any() { clear(); } 00155 00156 // assignments 00157 00158 /// Copy the state of 00159 any& operator=(const any& __rhs) 00160 { 00161 any(__rhs).swap(*this); 00162 return *this; 00163 } 00164 00165 /** 00166 * @brief Move assignment operator 00167 * 00168 * @post @c __rhs.empty() (not guaranteed for other implementations) 00169 */ 00170 any& operator=(any&& __rhs) noexcept 00171 { 00172 any(std::move(__rhs)).swap(*this); 00173 return *this; 00174 } 00175 00176 /// Store a copy of @p __rhs as the contained object. 00177 template<typename _ValueType> 00178 any& operator=(_ValueType&& __rhs) 00179 { 00180 any(std::forward<_ValueType>(__rhs)).swap(*this); 00181 return *this; 00182 } 00183 00184 // modifiers 00185 00186 /// If not empty, destroy the contained object. 00187 void clear() noexcept 00188 { 00189 if (!empty()) 00190 { 00191 _M_manager(_Op_destroy, this, nullptr); 00192 _M_manager = nullptr; 00193 } 00194 } 00195 00196 /// Exchange state with another object. 00197 void swap(any& __rhs) noexcept 00198 { 00199 std::swap(_M_manager, __rhs._M_manager); 00200 std::swap(_M_storage, __rhs._M_storage); 00201 } 00202 00203 // observers 00204 00205 /// Reports whether there is a contained object or not. 00206 bool empty() const noexcept { return _M_manager == nullptr; } 00207 00208 #if __cpp_rtti 00209 /// The @c typeid of the contained object, or @c typeid(void) if empty. 00210 const type_info& type() const noexcept 00211 { 00212 if (empty()) 00213 return typeid(void); 00214 _Arg __arg; 00215 _M_manager(_Op_get_type_info, this, &__arg); 00216 return *__arg._M_typeinfo; 00217 } 00218 #endif 00219 00220 template<typename _Tp> 00221 static constexpr bool __is_valid_cast() 00222 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; } 00223 00224 private: 00225 enum _Op { _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy }; 00226 00227 union _Arg 00228 { 00229 void* _M_obj; 00230 const std::type_info* _M_typeinfo; 00231 any* _M_any; 00232 }; 00233 00234 void (*_M_manager)(_Op, const any*, _Arg*); 00235 _Storage _M_storage; 00236 00237 template<typename _Tp> 00238 friend void* __any_caster(const any* __any) 00239 { 00240 if (__any->_M_manager != &_Manager<decay_t<_Tp>>::_S_manage) 00241 return nullptr; 00242 _Arg __arg; 00243 __any->_M_manager(_Op_access, __any, &__arg); 00244 return __arg._M_obj; 00245 } 00246 00247 // Manage in-place contained object. 00248 template<typename _Tp> 00249 struct _Manager_internal 00250 { 00251 static void 00252 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 00253 00254 template<typename _Up> 00255 static _Storage 00256 _S_create(_Up&& __value) 00257 { 00258 _Storage __storage; 00259 void* __addr = &__storage._M_buffer; 00260 ::new (__addr) _Tp(std::forward<_Up>(__value)); 00261 return __storage; 00262 } 00263 00264 template<typename _Alloc, typename _Up> 00265 static _Storage 00266 _S_alloc(const _Alloc&, _Up&& __value) 00267 { 00268 return _S_create(std::forward<_Up>(__value)); 00269 } 00270 }; 00271 00272 // Manage external contained object. 00273 template<typename _Tp> 00274 struct _Manager_external 00275 { 00276 static void 00277 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 00278 00279 template<typename _Up> 00280 static _Storage 00281 _S_create(_Up&& __value) 00282 { 00283 _Storage __storage; 00284 __storage._M_ptr = new _Tp(std::forward<_Up>(__value)); 00285 return __storage; 00286 } 00287 }; 00288 }; 00289 00290 /// Exchange the states of two @c any objects. 00291 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); } 00292 00293 /** 00294 * @brief Access the contained object. 00295 * 00296 * @tparam _ValueType A const-reference or CopyConstructible type. 00297 * @param __any The object to access. 00298 * @return The contained object. 00299 * @throw bad_any_cast If <code> 00300 * __any.type() != typeid(remove_reference_t<_ValueType>) 00301 * </code> 00302 */ 00303 template<typename _ValueType> 00304 inline _ValueType any_cast(const any& __any) 00305 { 00306 static_assert(any::__is_valid_cast<_ValueType>(), 00307 "Template argument must be a reference or CopyConstructible type"); 00308 auto __p = any_cast<add_const_t<remove_reference_t<_ValueType>>>(&__any); 00309 if (__p) 00310 return *__p; 00311 __throw_bad_any_cast(); 00312 } 00313 00314 /** 00315 * @brief Access the contained object. 00316 * 00317 * @tparam _ValueType A reference or CopyConstructible type. 00318 * @param __any The object to access. 00319 * @return The contained object. 00320 * @throw bad_any_cast If <code> 00321 * __any.type() != typeid(remove_reference_t<_ValueType>) 00322 * </code> 00323 * 00324 * @{ 00325 */ 00326 template<typename _ValueType> 00327 inline _ValueType any_cast(any& __any) 00328 { 00329 static_assert(any::__is_valid_cast<_ValueType>(), 00330 "Template argument must be a reference or CopyConstructible type"); 00331 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 00332 if (__p) 00333 return *__p; 00334 __throw_bad_any_cast(); 00335 } 00336 00337 template<typename _ValueType> 00338 inline _ValueType any_cast(any&& __any) 00339 { 00340 static_assert(any::__is_valid_cast<_ValueType>(), 00341 "Template argument must be a reference or CopyConstructible type"); 00342 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 00343 if (__p) 00344 return *__p; 00345 __throw_bad_any_cast(); 00346 } 00347 // @} 00348 00349 /** 00350 * @brief Access the contained object. 00351 * 00352 * @tparam _ValueType The type of the contained object. 00353 * @param __any A pointer to the object to access. 00354 * @return The address of the contained object if <code> 00355 * __any != nullptr && __any.type() == typeid(_ValueType) 00356 * </code>, otherwise a null pointer. 00357 * 00358 * @{ 00359 */ 00360 template<typename _ValueType> 00361 inline const _ValueType* any_cast(const any* __any) noexcept 00362 { 00363 if (__any) 00364 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 00365 return nullptr; 00366 } 00367 00368 template<typename _ValueType> 00369 inline _ValueType* any_cast(any* __any) noexcept 00370 { 00371 if (__any) 00372 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 00373 return nullptr; 00374 } 00375 // @} 00376 00377 template<typename _Tp> 00378 void 00379 any::_Manager_internal<_Tp>:: 00380 _S_manage(_Op __which, const any* __any, _Arg* __arg) 00381 { 00382 // The contained object is in _M_storage._M_buffer 00383 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer); 00384 switch (__which) 00385 { 00386 case _Op_access: 00387 __arg->_M_obj = const_cast<_Tp*>(__ptr); 00388 break; 00389 case _Op_get_type_info: 00390 #if __cpp_rtti 00391 __arg->_M_typeinfo = &typeid(_Tp); 00392 #endif 00393 break; 00394 case _Op_clone: 00395 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr); 00396 break; 00397 case _Op_destroy: 00398 __ptr->~_Tp(); 00399 break; 00400 } 00401 } 00402 00403 template<typename _Tp> 00404 void 00405 any::_Manager_external<_Tp>:: 00406 _S_manage(_Op __which, const any* __any, _Arg* __arg) 00407 { 00408 // The contained object is *_M_storage._M_ptr 00409 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr); 00410 switch (__which) 00411 { 00412 case _Op_access: 00413 __arg->_M_obj = const_cast<_Tp*>(__ptr); 00414 break; 00415 case _Op_get_type_info: 00416 #if __cpp_rtti 00417 __arg->_M_typeinfo = &typeid(_Tp); 00418 #endif 00419 break; 00420 case _Op_clone: 00421 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr); 00422 break; 00423 case _Op_destroy: 00424 delete __ptr; 00425 break; 00426 } 00427 } 00428 00429 // @} group any 00430 _GLIBCXX_END_NAMESPACE_VERSION 00431 } // namespace fundamentals_v1 00432 } // namespace experimental 00433 } // namespace std 00434 00435 #endif // C++14 00436 00437 #endif // _GLIBCXX_EXPERIMENTAL_ANY