libstdc++
any
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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>
43 
44 namespace std _GLIBCXX_VISIBILITY(default)
45 {
46 namespace experimental
47 {
48 inline namespace fundamentals_v1
49 {
50 _GLIBCXX_BEGIN_NAMESPACE_VERSION
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
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
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 _GLIBCXX_END_NAMESPACE_VERSION
524 } // namespace fundamentals_v1
525 } // namespace experimental
526 } // namespace std
527 
528 #endif // C++14
529 
530 #endif // _GLIBCXX_EXPERIMENTAL_ANY
const type_info & type() const noexcept
The typeid of the contained object, or typeid(void) if empty.
Definition: any:275
_ValueType * any_cast(any *__any) noexcept
Access the contained object.
Definition: any:448
any(any &&__other) noexcept
Move constructor, transfer the state from __other.
Definition: any:148
void clear() noexcept
If not empty, destroy the contained object.
Definition: any:229
any(_ValueType &&__value)
Construct with a copy of __value as the contained object.
Definition: any:165
is_lvalue_reference
Definition: type_traits:389
any & operator=(any &&__rhs) noexcept
Move assignment operator.
Definition: any:203
ISO C++ entities toplevel namespace is std.
~any()
Destructor, calls clear()
Definition: any:187
any() noexcept
Default constructor, creates an empty object.
Definition: any:128
Thrown during incorrect typecasting.If you attempt an invalid dynamic_cast expression, an instance of this class (or something derived from this class) is thrown.
Definition: typeinfo:187
any(const any &__other)
Copy constructor, copies the state of __other.
Definition: any:131
virtual const char * what() const noexcept
Definition: any:71
bool empty() const noexcept
Reports whether there is a contained object or not.
Definition: any:271
any & operator=(const any &__rhs)
Copy the state of another object.
Definition: any:192
enable_if_t<!is_same< any, decay_t< _ValueType > >::value, any & > operator=(_ValueType &&__rhs)
Store a copy of __rhs as the contained object.
Definition: any:220
A type-safe container of any type.
Definition: any:89
void swap(any &__rhs) noexcept
Exchange state with another object.
Definition: any:239
Part of RTTI.
Definition: typeinfo:88
Exception class thrown by a failed any_cast.
Definition: any:68