libstdc++
any
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00001 // <experimental/any> -*- C++ -*-
00002 
00003 // Copyright (C) 2014-2016 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       if (__rhs.empty())
00195         clear();
00196       else if (this != &__rhs)
00197         {
00198           if (!empty())
00199             _M_manager(_Op_destroy, this, nullptr);
00200           _Arg __arg;
00201           __arg._M_any = this;
00202           __rhs._M_manager(_Op_clone, &__rhs, &__arg);
00203         }
00204       return *this;
00205     }
00206 
00207     /**
00208      * @brief Move assignment operator
00209      *
00210      * @post @c __rhs.empty() (not guaranteed for other implementations)
00211      */
00212     any& operator=(any&& __rhs) noexcept
00213     {
00214       if (__rhs.empty())
00215         clear();
00216       else if (this != &__rhs)
00217         {
00218           if (!empty())
00219             _M_manager(_Op_destroy, this, nullptr);
00220           _Arg __arg;
00221           __arg._M_any = this;
00222           __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
00223         }
00224       return *this;
00225     }
00226 
00227     /// Store a copy of @p __rhs as the contained object.
00228     template<typename _ValueType>
00229       enable_if_t<!is_same<any, decay_t<_ValueType>>::value, any&>
00230       operator=(_ValueType&& __rhs)
00231       {
00232         *this = any(std::forward<_ValueType>(__rhs));
00233         return *this;
00234       }
00235 
00236     // modifiers
00237 
00238     /// If not empty, destroy the contained object.
00239     void clear() noexcept
00240     {
00241       if (!empty())
00242       {
00243         _M_manager(_Op_destroy, this, nullptr);
00244         _M_manager = nullptr;
00245       }
00246     }
00247 
00248     /// Exchange state with another object.
00249     void swap(any& __rhs) noexcept
00250     {
00251       if (empty() && __rhs.empty())
00252         return;
00253 
00254       if (!empty() && !__rhs.empty())
00255         {
00256           if (this == &__rhs)
00257             return;
00258 
00259           any __tmp;
00260           _Arg __arg;
00261           __arg._M_any = &__tmp;
00262           __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
00263           __arg._M_any = &__rhs;
00264           _M_manager(_Op_xfer, this, &__arg);
00265           __arg._M_any = this;
00266           __tmp._M_manager(_Op_xfer, &__tmp, &__arg);
00267         }
00268       else
00269         {
00270           any* __empty = empty() ? this : &__rhs;
00271           any* __full = empty() ? &__rhs : this;
00272           _Arg __arg;
00273           __arg._M_any = __empty;
00274           __full->_M_manager(_Op_xfer, __full, &__arg);
00275         }
00276     }
00277 
00278     // observers
00279 
00280     /// Reports whether there is a contained object or not.
00281     bool empty() const noexcept { return _M_manager == nullptr; }
00282 
00283 #if __cpp_rtti
00284     /// The @c typeid of the contained object, or @c typeid(void) if empty.
00285     const type_info& type() const noexcept
00286     {
00287       if (empty())
00288         return typeid(void);
00289       _Arg __arg;
00290       _M_manager(_Op_get_type_info, this, &__arg);
00291       return *__arg._M_typeinfo;
00292     }
00293 #endif
00294 
00295     template<typename _Tp>
00296       static constexpr bool __is_valid_cast()
00297       { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; }
00298 
00299   private:
00300     enum _Op {
00301         _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer
00302     };
00303 
00304     union _Arg
00305     {
00306         void* _M_obj;
00307         const std::type_info* _M_typeinfo;
00308         any* _M_any;
00309     };
00310 
00311     void (*_M_manager)(_Op, const any*, _Arg*);
00312     _Storage _M_storage;
00313 
00314     template<typename _Tp>
00315       friend void* __any_caster(const any* __any);
00316 
00317     // Manage in-place contained object.
00318     template<typename _Tp>
00319       struct _Manager_internal
00320       {
00321         static void
00322         _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
00323 
00324         template<typename _Up>
00325           static void
00326           _S_create(_Storage& __storage, _Up&& __value)
00327           {
00328             void* __addr = &__storage._M_buffer;
00329             ::new (__addr) _Tp(std::forward<_Up>(__value));
00330           }
00331       };
00332 
00333     // Manage external contained object.
00334     template<typename _Tp>
00335       struct _Manager_external
00336       {
00337         static void
00338         _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
00339 
00340         template<typename _Up>
00341           static void
00342           _S_create(_Storage& __storage, _Up&& __value)
00343           {
00344             __storage._M_ptr = new _Tp(std::forward<_Up>(__value));
00345           }
00346       };
00347   };
00348 
00349   /// Exchange the states of two @c any objects.
00350   inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); }
00351 
00352   /**
00353    * @brief Access the contained object.
00354    *
00355    * @tparam  _ValueType  A const-reference or CopyConstructible type.
00356    * @param   __any       The object to access.
00357    * @return  The contained object.
00358    * @throw   bad_any_cast If <code>
00359    *          __any.type() != typeid(remove_reference_t<_ValueType>)
00360    *          </code>
00361    */
00362   template<typename _ValueType>
00363     inline _ValueType any_cast(const any& __any)
00364     {
00365       static_assert(any::__is_valid_cast<_ValueType>(),
00366           "Template argument must be a reference or CopyConstructible type");
00367       auto __p = any_cast<add_const_t<remove_reference_t<_ValueType>>>(&__any);
00368       if (__p)
00369         return *__p;
00370       __throw_bad_any_cast();
00371     }
00372 
00373   /**
00374    * @brief Access the contained object.
00375    *
00376    * @tparam  _ValueType  A reference or CopyConstructible type.
00377    * @param   __any       The object to access.
00378    * @return  The contained object.
00379    * @throw   bad_any_cast If <code>
00380    *          __any.type() != typeid(remove_reference_t<_ValueType>)
00381    *          </code>
00382    *
00383    * @{
00384    */
00385   template<typename _ValueType>
00386     inline _ValueType any_cast(any& __any)
00387     {
00388       static_assert(any::__is_valid_cast<_ValueType>(),
00389           "Template argument must be a reference or CopyConstructible type");
00390       auto __p = any_cast<remove_reference_t<_ValueType>>(&__any);
00391       if (__p)
00392         return *__p;
00393       __throw_bad_any_cast();
00394     }
00395 
00396   template<typename _ValueType,
00397            typename enable_if<!is_move_constructible<_ValueType>::value
00398                               || is_lvalue_reference<_ValueType>::value,
00399                               bool>::type = true>
00400     inline _ValueType any_cast(any&& __any)
00401     {
00402       static_assert(any::__is_valid_cast<_ValueType>(),
00403           "Template argument must be a reference or CopyConstructible type");
00404       auto __p = any_cast<remove_reference_t<_ValueType>>(&__any);
00405       if (__p)
00406         return *__p;
00407       __throw_bad_any_cast();
00408     }
00409 
00410   template<typename _ValueType,
00411            typename enable_if<is_move_constructible<_ValueType>::value
00412                               && !is_lvalue_reference<_ValueType>::value,
00413                               bool>::type = false>
00414     inline _ValueType any_cast(any&& __any)
00415     {
00416       static_assert(any::__is_valid_cast<_ValueType>(),
00417           "Template argument must be a reference or CopyConstructible type");
00418       auto __p = any_cast<remove_reference_t<_ValueType>>(&__any);
00419       if (__p)
00420         return std::move(*__p);
00421       __throw_bad_any_cast();
00422     }
00423   // @}
00424 
00425   template<typename _Tp>
00426     void* __any_caster(const any* __any)
00427     {
00428       struct _None { };
00429       using _Up = decay_t<_Tp>;
00430       using _Vp = conditional_t<is_copy_constructible<_Up>::value, _Up, _None>;
00431       if (__any->_M_manager != &any::_Manager<_Vp>::_S_manage)
00432         return nullptr;
00433       any::_Arg __arg;
00434       __any->_M_manager(any::_Op_access, __any, &__arg);
00435       return __arg._M_obj;
00436     }
00437 
00438   /**
00439    * @brief Access the contained object.
00440    *
00441    * @tparam  _ValueType  The type of the contained object.
00442    * @param   __any       A pointer to the object to access.
00443    * @return  The address of the contained object if <code>
00444    *          __any != nullptr && __any.type() == typeid(_ValueType)
00445    *          </code>, otherwise a null pointer.
00446    *
00447    * @{
00448    */
00449   template<typename _ValueType>
00450     inline const _ValueType* any_cast(const any* __any) noexcept
00451     {
00452       if (__any)
00453         return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
00454       return nullptr;
00455     }
00456 
00457   template<typename _ValueType>
00458     inline _ValueType* any_cast(any* __any) noexcept
00459     {
00460       if (__any)
00461         return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
00462       return nullptr;
00463     }
00464   // @}
00465 
00466   template<typename _Tp>
00467     void
00468     any::_Manager_internal<_Tp>::
00469     _S_manage(_Op __which, const any* __any, _Arg* __arg)
00470     {
00471       // The contained object is in _M_storage._M_buffer
00472       auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer);
00473       switch (__which)
00474       {
00475       case _Op_access:
00476         __arg->_M_obj = const_cast<_Tp*>(__ptr);
00477         break;
00478       case _Op_get_type_info:
00479 #if __cpp_rtti
00480         __arg->_M_typeinfo = &typeid(_Tp);
00481 #endif
00482         break;
00483       case _Op_clone:
00484         ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr);
00485         __arg->_M_any->_M_manager = __any->_M_manager;
00486         break;
00487       case _Op_destroy:
00488         __ptr->~_Tp();
00489         break;
00490       case _Op_xfer:
00491         ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr);
00492         __ptr->~_Tp();
00493         __arg->_M_any->_M_manager = __any->_M_manager;
00494         const_cast<any*>(__any)->_M_manager = nullptr;
00495         break;
00496       }
00497     }
00498 
00499   template<typename _Tp>
00500     void
00501     any::_Manager_external<_Tp>::
00502     _S_manage(_Op __which, const any* __any, _Arg* __arg)
00503     {
00504       // The contained object is *_M_storage._M_ptr
00505       auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr);
00506       switch (__which)
00507       {
00508       case _Op_access:
00509         __arg->_M_obj = const_cast<_Tp*>(__ptr);
00510         break;
00511       case _Op_get_type_info:
00512 #if __cpp_rtti
00513         __arg->_M_typeinfo = &typeid(_Tp);
00514 #endif
00515         break;
00516       case _Op_clone:
00517         __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr);
00518         __arg->_M_any->_M_manager = __any->_M_manager;
00519         break;
00520       case _Op_destroy:
00521         delete __ptr;
00522         break;
00523       case _Op_xfer:
00524         __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr;
00525         __arg->_M_any->_M_manager = __any->_M_manager;
00526         const_cast<any*>(__any)->_M_manager = nullptr;
00527         break;
00528       }
00529     }
00530 
00531   // @} group any
00532 _GLIBCXX_END_NAMESPACE_VERSION
00533 } // namespace fundamentals_v1
00534 } // namespace experimental
00535 } // namespace std
00536 
00537 #endif // C++14
00538 
00539 #endif // _GLIBCXX_EXPERIMENTAL_ANY