libstdc++-v3/include/experimental/any

   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 <= 201103L
  35 # include <bits/c++14_warning.h>
  36 #else
  37
  38 #include <typeinfo>
  39 #include <new>
  40 #include <utility>
  41 #include <type_traits>
  42 #include <experimental/bits/lfts_config.h>
  43
  44 namespace std _GLIBCXX_VISIBILITY(default)
  45 {
  46 _GLIBCXX_BEGIN_NAMESPACE_VERSION
  47
  48 namespace experimental
  49 {
  50 inline namespace fundamentals_v1
  51 {
  52   /**
  53    * @defgroup any Type-safe container of any type
  54    * @ingroup experimental
  55    *
  56    * A type-safe container for single values of value types, as
  57    * described in n3804 "Any Library Proposal (Revision 3)".
  58    *
  59    * @{
  60    */
  61
  62 #define __cpp_lib_experimental_any 201411
  63
  64   /**
  65    *  @brief Exception class thrown by a failed @c any_cast
  66    *  @ingroup exceptions
  67    */
  68   class bad_any_cast : public bad_cast
  69   {
  70   public:
  71     virtual const char* what() const noexcept { return "bad any_cast"; }
  72   };
  73
  74   [[gnu::noreturn]] inline void __throw_bad_any_cast()
  75   {
  76 #if __cpp_exceptions
  77     throw bad_any_cast{};
  78 #else
  79     __builtin_abort();
  80 #endif
  81   }
  82
  83   /**
  84    *  @brief A type-safe container of any type.
  85    *
  86    *  An @c any object's state is either empty or it stores a contained object
  87    *  of CopyConstructible type.
  88    */
  89   class any
  90   {
  91     // Holds either pointer to a heap object or the contained object itself.
  92     union _Storage
  93     {
  94       // This constructor intentionally doesn't initialize anything.
  95       _Storage() = default;
  96
  97       // Prevent trivial copies of this type, buffer might hold a non-POD.
  98       _Storage(const _Storage&) = delete;
  99       _Storage& operator=(const _Storage&) = delete;
 100
 101       void* _M_ptr;
 102       aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer;
 103     };
 104
 105     template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>,
 106              bool _Fits = (sizeof(_Tp) <= sizeof(_Storage))
 107                           && (alignof(_Tp) <= alignof(_Storage))>
 108       using _Internal = std::integral_constant<bool, _Safe::value && _Fits>;
 109
 110     template<typename _Tp>
 111       struct _Manager_internal; // uses small-object optimization
 112
 113     template<typename _Tp>
 114       struct _Manager_external; // creates contained object on the heap
 115
 116     template<typename _Tp>
 117       using _Manager = conditional_t<_Internal<_Tp>::value,
 118                                      _Manager_internal<_Tp>,
 119                                      _Manager_external<_Tp>>;
 120
 121     template<typename _Tp, typename _Decayed = decay_t<_Tp>>
 122       using _Decay = enable_if_t<!is_same<_Decayed, any>::value, _Decayed>;
 123
 124   public:
 125     // construct/destruct
 126
 127     /// Default constructor, creates an empty object.
 128     any() noexcept : _M_manager(nullptr) { }
 129
 130     /// Copy constructor, copies the state of @p __other
 131     any(const any& __other)
 132     {
 133       if (__other.empty())
 134         _M_manager = nullptr;
 135       else
 136         {
 137           _Arg __arg;
 138           __arg._M_any = this;
 139           __other._M_manager(_Op_clone, &__other, &__arg);
 140         }
 141     }
 142
 143     /**
 144      * @brief Move constructor, transfer the state from @p __other
 145      *
 146      * @post @c __other.empty() (this postcondition is a GNU extension)
 147      */
 148     any(any&& __other) noexcept
 149     {
 150       if (__other.empty())
 151         _M_manager = nullptr;
 152       else
 153         {
 154           _Arg __arg;
 155           __arg._M_any = this;
 156           __other._M_manager(_Op_xfer, &__other, &__arg);
 157         }
 158     }
 159
 160     /// Construct with a copy of @p __value as the contained object.
 161     template <typename _ValueType, typename _Tp = _Decay<_ValueType>,
 162               typename _Mgr = _Manager<_Tp>,
 163               typename enable_if<is_constructible<_Tp, _ValueType&&>::value,
 164                                  bool>::type = true>
 165       any(_ValueType&& __value)
 166       : _M_manager(&_Mgr::_S_manage)
 167       {
 168         _Mgr::_S_create(_M_storage, std::forward<_ValueType>(__value));
 169         static_assert(is_copy_constructible<_Tp>::value,
 170                       "The contained object must be CopyConstructible");
 171       }
 172
 173     /// Construct with a copy of @p __value as the contained object.
 174     template <typename _ValueType, typename _Tp = _Decay<_ValueType>,
 175               typename _Mgr = _Manager<_Tp>,
 176               typename enable_if<!is_constructible<_Tp, _ValueType&&>::value,
 177                                  bool>::type = false>
 178       any(_ValueType&& __value)
 179       : _M_manager(&_Mgr::_S_manage)
 180       {
 181         _Mgr::_S_create(_M_storage, __value);
 182         static_assert(is_copy_constructible<_Tp>::value,
 183                       "The contained object must be CopyConstructible");
 184       }
 185
 186     /// Destructor, calls @c clear()
 187     ~any() { clear(); }
 188
 189     // assignments
 190
 191     /// Copy the state of another object.
 192     any& operator=(const any& __rhs)
 193     {
 194       *this = any(__rhs);
 195       return *this;
 196     }
 197
 198     /**
 199      * @brief Move assignment operator
 200      *
 201      * @post @c __rhs.empty() (not guaranteed for other implementations)
 202      */
 203     any& operator=(any&& __rhs) noexcept
 204     {
 205       if (__rhs.empty())
 206         clear();
 207       else if (this != &__rhs)
 208         {
 209           clear();
 210           _Arg __arg;
 211           __arg._M_any = this;
 212           __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
 213         }
 214       return *this;
 215     }
 216
 217     /// Store a copy of @p __rhs as the contained object.
 218     template<typename _ValueType>
 219       enable_if_t<!is_same<any, decay_t<_ValueType>>::value, any&>
 220       operator=(_ValueType&& __rhs)
 221       {
 222         *this = any(std::forward<_ValueType>(__rhs));
 223         return *this;
 224       }
 225
 226     // modifiers
 227
 228     /// If not empty, destroy the contained object.
 229     void clear() noexcept
 230     {
 231       if (!empty())
 232       {
 233         _M_manager(_Op_destroy, this, nullptr);
 234         _M_manager = nullptr;
 235       }
 236     }
 237
 238     /// Exchange state with another object.
 239     void swap(any& __rhs) noexcept
 240     {
 241       if (empty() && __rhs.empty())
 242         return;
 243
 244       if (!empty() && !__rhs.empty())
 245         {
 246           if (this == &__rhs)
 247             return;
 248
 249           any __tmp;
 250           _Arg __arg;
 251           __arg._M_any = &__tmp;
 252           __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
 253           __arg._M_any = &__rhs;
 254           _M_manager(_Op_xfer, this, &__arg);
 255           __arg._M_any = this;
 256           __tmp._M_manager(_Op_xfer, &__tmp, &__arg);
 257         }
 258       else
 259         {
 260           any* __empty = empty() ? this : &__rhs;
 261           any* __full = empty() ? &__rhs : this;
 262           _Arg __arg;
 263           __arg._M_any = __empty;
 264           __full->_M_manager(_Op_xfer, __full, &__arg);
 265         }
 266     }
 267
 268     // observers
 269
 270     /// Reports whether there is a contained object or not.
 271     bool empty() const noexcept { return _M_manager == nullptr; }
 272
 273 #if __cpp_rtti
 274     /// The @c typeid of the contained object, or @c typeid(void) if empty.
 275     const type_info& type() const noexcept
 276     {
 277       if (empty())
 278         return typeid(void);
 279       _Arg __arg;
 280       _M_manager(_Op_get_type_info, this, &__arg);
 281       return *__arg._M_typeinfo;
 282     }
 283 #endif
 284
 285     template<typename _Tp>
 286       static constexpr bool __is_valid_cast()
 287       { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; }
 288
 289   private:
 290     enum _Op {
 291         _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer
 292     };
 293
 294     union _Arg
 295     {
 296         void* _M_obj;
 297         const std::type_info* _M_typeinfo;
 298         any* _M_any;
 299     };
 300
 301     void (*_M_manager)(_Op, const any*, _Arg*);
 302     _Storage _M_storage;
 303
 304     template<typename _Tp>
 305       friend void* __any_caster(const any* __any);
 306
 307     // Manage in-place contained object.
 308     template<typename _Tp>
 309       struct _Manager_internal
 310       {
 311         static void
 312         _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
 313
 314         template<typename _Up>
 315           static void
 316           _S_create(_Storage& __storage, _Up&& __value)
 317           {
 318             void* __addr = &__storage._M_buffer;
 319             ::new (__addr) _Tp(std::forward<_Up>(__value));
 320           }
 321       };
 322
 323     // Manage external contained object.
 324     template<typename _Tp>
 325       struct _Manager_external
 326       {
 327         static void
 328         _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
 329
 330         template<typename _Up>
 331           static void
 332           _S_create(_Storage& __storage, _Up&& __value)
 333           {
 334             __storage._M_ptr = new _Tp(std::forward<_Up>(__value));
 335           }
 336       };
 337   };
 338
 339   /// Exchange the states of two @c any objects.
 340   inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); }
 341
 342   /**
 343    * @brief Access the contained object.
 344    *
 345    * @tparam  _ValueType  A const-reference or CopyConstructible type.
 346    * @param   __any       The object to access.
 347    * @return  The contained object.
 348    * @throw   bad_any_cast If <code>
 349    *          __any.type() != typeid(remove_reference_t<_ValueType>)
 350    *          </code>
 351    */
 352   template<typename _ValueType>
 353     inline _ValueType any_cast(const any& __any)
 354     {
 355       static_assert(any::__is_valid_cast<_ValueType>(),
 356           "Template argument must be a reference or CopyConstructible type");
 357       auto __p = any_cast<add_const_t<remove_reference_t<_ValueType>>>(&__any);
 358       if (__p)
 359         return *__p;
 360       __throw_bad_any_cast();
 361     }
 362
 363   /**
 364    * @brief Access the contained object.
 365    *
 366    * @tparam  _ValueType  A reference or CopyConstructible type.
 367    * @param   __any       The object to access.
 368    * @return  The contained object.
 369    * @throw   bad_any_cast If <code>
 370    *          __any.type() != typeid(remove_reference_t<_ValueType>)
 371    *          </code>
 372    *
 373    * @{
 374    */
 375   template<typename _ValueType>
 376     inline _ValueType any_cast(any& __any)
 377     {
 378       static_assert(any::__is_valid_cast<_ValueType>(),
 379           "Template argument must be a reference or CopyConstructible type");
 380       auto __p = any_cast<remove_reference_t<_ValueType>>(&__any);
 381       if (__p)
 382         return *__p;
 383       __throw_bad_any_cast();
 384     }
 385
 386   template<typename _ValueType,
 387            typename enable_if<!is_move_constructible<_ValueType>::value
 388                               || is_lvalue_reference<_ValueType>::value,
 389                               bool>::type = true>
 390     inline _ValueType any_cast(any&& __any)
 391     {
 392       static_assert(any::__is_valid_cast<_ValueType>(),
 393           "Template argument must be a reference or CopyConstructible type");
 394       auto __p = any_cast<remove_reference_t<_ValueType>>(&__any);
 395       if (__p)
 396         return *__p;
 397       __throw_bad_any_cast();
 398     }
 399
 400   template<typename _ValueType,
 401            typename enable_if<is_move_constructible<_ValueType>::value
 402                               && !is_lvalue_reference<_ValueType>::value,
 403                               bool>::type = false>
 404     inline _ValueType any_cast(any&& __any)
 405     {
 406       static_assert(any::__is_valid_cast<_ValueType>(),
 407           "Template argument must be a reference or CopyConstructible type");
 408       auto __p = any_cast<remove_reference_t<_ValueType>>(&__any);
 409       if (__p)
 410         return std::move(*__p);
 411       __throw_bad_any_cast();
 412     }
 413   // @}
 414
 415   template<typename _Tp>
 416     void* __any_caster(const any* __any)
 417     {
 418       struct _None { };
 419       using _Up = decay_t<_Tp>;
 420       using _Vp = conditional_t<is_copy_constructible<_Up>::value, _Up, _None>;
 421       if (__any->_M_manager != &any::_Manager<_Vp>::_S_manage)
 422         return nullptr;
 423       any::_Arg __arg;
 424       __any->_M_manager(any::_Op_access, __any, &__arg);
 425       return __arg._M_obj;
 426     }
 427
 428   /**
 429    * @brief Access the contained object.
 430    *
 431    * @tparam  _ValueType  The type of the contained object.
 432    * @param   __any       A pointer to the object to access.
 433    * @return  The address of the contained object if <code>
 434    *          __any != nullptr && __any.type() == typeid(_ValueType)
 435    *          </code>, otherwise a null pointer.
 436    *
 437    * @{
 438    */
 439   template<typename _ValueType>
 440     inline const _ValueType* any_cast(const any* __any) noexcept
 441     {
 442       if (__any)
 443         return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
 444       return nullptr;
 445     }
 446
 447   template<typename _ValueType>
 448     inline _ValueType* any_cast(any* __any) noexcept
 449     {
 450       if (__any)
 451         return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
 452       return nullptr;
 453     }
 454   // @}
 455
 456   template<typename _Tp>
 457     void
 458     any::_Manager_internal<_Tp>::
 459     _S_manage(_Op __which, const any* __any, _Arg* __arg)
 460     {
 461       // The contained object is in _M_storage._M_buffer
 462       auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer);
 463       switch (__which)
 464       {
 465       case _Op_access:
 466         __arg->_M_obj = const_cast<_Tp*>(__ptr);
 467         break;
 468       case _Op_get_type_info:
 469 #if __cpp_rtti
 470         __arg->_M_typeinfo = &typeid(_Tp);
 471 #endif
 472         break;
 473       case _Op_clone:
 474         ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr);
 475         __arg->_M_any->_M_manager = __any->_M_manager;
 476         break;
 477       case _Op_destroy:
 478         __ptr->~_Tp();
 479         break;
 480       case _Op_xfer:
 481         ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp
 482           (std::move(*const_cast<_Tp*>(__ptr)));
 483         __ptr->~_Tp();
 484         __arg->_M_any->_M_manager = __any->_M_manager;
 485         const_cast<any*>(__any)->_M_manager = nullptr;
 486         break;
 487       }
 488     }
 489
 490   template<typename _Tp>
 491     void
 492     any::_Manager_external<_Tp>::
 493     _S_manage(_Op __which, const any* __any, _Arg* __arg)
 494     {
 495       // The contained object is *_M_storage._M_ptr
 496       auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr);
 497       switch (__which)
 498       {
 499       case _Op_access:
 500         __arg->_M_obj = const_cast<_Tp*>(__ptr);
 501         break;
 502       case _Op_get_type_info:
 503 #if __cpp_rtti
 504         __arg->_M_typeinfo = &typeid(_Tp);
 505 #endif
 506         break;
 507       case _Op_clone:
 508         __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr);
 509         __arg->_M_any->_M_manager = __any->_M_manager;
 510         break;
 511       case _Op_destroy:
 512         delete __ptr;
 513         break;
 514       case _Op_xfer:
 515         __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr;
 516         __arg->_M_any->_M_manager = __any->_M_manager;
 517         const_cast<any*>(__any)->_M_manager = nullptr;
 518         break;
 519       }
 520     }
 521
 522   // @} group any
 523 } // namespace fundamentals_v1
 524 } // namespace experimental
 525
 526 _GLIBCXX_END_NAMESPACE_VERSION
 527 } // namespace std
 528
 529 #endif // C++14
 530
 531 #endif // _GLIBCXX_EXPERIMENTAL_ANY