libstdc++
any
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1 // <experimental/any> -*- C++ -*-
2 
3 // Copyright (C) 2014-2015 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/lfts_config.h>
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  void* _M_ptr;
95  std::aligned_storage<sizeof(_M_ptr), sizeof(_M_ptr)>::type _M_buffer;
96  };
97 
98  template<typename _Tp, typename _Safe = is_trivially_copyable<_Tp>,
99  bool _Fits = (sizeof(_Tp) <= sizeof(_Storage))>
100  using _Internal = std::integral_constant<bool, _Safe::value && _Fits>;
101 
102  template<typename _Tp>
103  struct _Manager_internal; // uses small-object optimization
104 
105  template<typename _Tp>
106  struct _Manager_external; // creates contained object on the heap
107 
108  template<typename _Tp>
109  using _Manager = conditional_t<_Internal<_Tp>::value,
110  _Manager_internal<_Tp>,
111  _Manager_external<_Tp>>;
112 
113  template<typename _Tp, typename _Decayed = decay_t<_Tp>>
114  using _Decay = enable_if_t<!is_same<_Decayed, any>::value, _Decayed>;
115 
116  public:
117  // construct/destruct
118 
119  /// Default constructor, creates an empty object.
120  any() noexcept : _M_manager(nullptr) { }
121 
122  /// Copy constructor, copies the state of @p __other
123  any(const any& __other) : _M_manager(__other._M_manager)
124  {
125  if (!__other.empty())
126  {
127  _Arg __arg;
128  __arg._M_any = this;
129  _M_manager(_Op_clone, &__other, &__arg);
130  }
131  }
132 
133  /**
134  * @brief Move constructor, transfer the state from @p __other
135  *
136  * @post @c __other.empty() (not guaranteed for other implementations)
137  */
138  any(any&& __other) noexcept
139  : _M_manager(__other._M_manager),
140  _M_storage(__other._M_storage)
141  { __other._M_manager = nullptr; }
142 
143  /// Construct with a copy of @p __value as the contained object.
144  template <typename _ValueType, typename _Tp = _Decay<_ValueType>,
145  typename _Mgr = _Manager<_Tp>>
146  any(_ValueType&& __value)
147  : _M_manager(&_Mgr::_S_manage),
148  _M_storage(_Mgr::_S_create(std::forward<_ValueType>(__value)))
149  {
150  static_assert(is_copy_constructible<_Tp>::value,
151  "The contained object must be CopyConstructible");
152  }
153 
154  /// Destructor, calls @c clear()
155  ~any() { clear(); }
156 
157  // assignments
158 
159  /// Copy the state of
160  any& operator=(const any& __rhs)
161  {
162  any(__rhs).swap(*this);
163  return *this;
164  }
165 
166  /**
167  * @brief Move assignment operator
168  *
169  * @post @c __rhs.empty() (not guaranteed for other implementations)
170  */
171  any& operator=(any&& __rhs) noexcept
172  {
173  any(std::move(__rhs)).swap(*this);
174  return *this;
175  }
176 
177  /// Store a copy of @p __rhs as the contained object.
178  template<typename _ValueType>
179  any& operator=(_ValueType&& __rhs)
180  {
181  any(std::forward<_ValueType>(__rhs)).swap(*this);
182  return *this;
183  }
184 
185  // modifiers
186 
187  /// If not empty, destroy the contained object.
188  void clear() noexcept
189  {
190  if (!empty())
191  {
192  _M_manager(_Op_destroy, this, nullptr);
193  _M_manager = nullptr;
194  }
195  }
196 
197  /// Exchange state with another object.
198  void swap(any& __rhs) noexcept
199  {
200  std::swap(_M_manager, __rhs._M_manager);
201  std::swap(_M_storage, __rhs._M_storage);
202  }
203 
204  // observers
205 
206  /// Reports whether there is a contained object or not.
207  bool empty() const noexcept { return _M_manager == nullptr; }
208 
209 #if __cpp_rtti
210  /// The @c typeid of the contained object, or @c typeid(void) if empty.
211  const type_info& type() const noexcept
212  {
213  if (empty())
214  return typeid(void);
215  _Arg __arg;
216  _M_manager(_Op_get_type_info, this, &__arg);
217  return *__arg._M_typeinfo;
218  }
219 #endif
220 
221  template<typename _Tp>
222  static constexpr bool __is_valid_cast()
223  { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; }
224 
225  private:
226  enum _Op { _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy };
227 
228  union _Arg
229  {
230  void* _M_obj;
231  const std::type_info* _M_typeinfo;
232  any* _M_any;
233  };
234 
235  void (*_M_manager)(_Op, const any*, _Arg*);
236  _Storage _M_storage;
237 
238  template<typename _Tp>
239  friend void* __any_caster(const any* __any);
240 
241  // Manage in-place contained object.
242  template<typename _Tp>
243  struct _Manager_internal
244  {
245  static void
246  _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
247 
248  template<typename _Up>
249  static _Storage
250  _S_create(_Up&& __value)
251  {
252  _Storage __storage;
253  void* __addr = &__storage._M_buffer;
254  ::new (__addr) _Tp(std::forward<_Up>(__value));
255  return __storage;
256  }
257 
258  template<typename _Alloc, typename _Up>
259  static _Storage
260  _S_alloc(const _Alloc&, _Up&& __value)
261  {
262  return _S_create(std::forward<_Up>(__value));
263  }
264  };
265 
266  // Manage external contained object.
267  template<typename _Tp>
268  struct _Manager_external
269  {
270  static void
271  _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
272 
273  template<typename _Up>
274  static _Storage
275  _S_create(_Up&& __value)
276  {
277  _Storage __storage;
278  __storage._M_ptr = new _Tp(std::forward<_Up>(__value));
279  return __storage;
280  }
281  };
282  };
283 
284  /// Exchange the states of two @c any objects.
285  inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); }
286 
287  /**
288  * @brief Access the contained object.
289  *
290  * @tparam _ValueType A const-reference or CopyConstructible type.
291  * @param __any The object to access.
292  * @return The contained object.
293  * @throw bad_any_cast If <code>
294  * __any.type() != typeid(remove_reference_t<_ValueType>)
295  * </code>
296  */
297  template<typename _ValueType>
298  inline _ValueType any_cast(const any& __any)
299  {
300  static_assert(any::__is_valid_cast<_ValueType>(),
301  "Template argument must be a reference or CopyConstructible type");
302  auto __p = any_cast<add_const_t<remove_reference_t<_ValueType>>>(&__any);
303  if (__p)
304  return *__p;
305  __throw_bad_any_cast();
306  }
307 
308  /**
309  * @brief Access the contained object.
310  *
311  * @tparam _ValueType A reference or CopyConstructible type.
312  * @param __any The object to access.
313  * @return The contained object.
314  * @throw bad_any_cast If <code>
315  * __any.type() != typeid(remove_reference_t<_ValueType>)
316  * </code>
317  *
318  * @{
319  */
320  template<typename _ValueType>
321  inline _ValueType any_cast(any& __any)
322  {
323  static_assert(any::__is_valid_cast<_ValueType>(),
324  "Template argument must be a reference or CopyConstructible type");
325  auto __p = any_cast<remove_reference_t<_ValueType>>(&__any);
326  if (__p)
327  return *__p;
328  __throw_bad_any_cast();
329  }
330 
331  template<typename _ValueType>
332  inline _ValueType any_cast(any&& __any)
333  {
334  static_assert(any::__is_valid_cast<_ValueType>(),
335  "Template argument must be a reference or CopyConstructible type");
336  auto __p = any_cast<remove_reference_t<_ValueType>>(&__any);
337  if (__p)
338  return *__p;
339  __throw_bad_any_cast();
340  }
341  // @}
342 
343  template<typename _Tp>
344  void* __any_caster(const any* __any)
345  {
346  struct _None { };
347  using _Up = decay_t<_Tp>;
348  using _Vp = conditional_t<is_copy_constructible<_Up>::value, _Up, _None>;
349  if (__any->_M_manager != &any::_Manager<_Vp>::_S_manage)
350  return nullptr;
351  any::_Arg __arg;
352  __any->_M_manager(any::_Op_access, __any, &__arg);
353  return __arg._M_obj;
354  }
355 
356  /**
357  * @brief Access the contained object.
358  *
359  * @tparam _ValueType The type of the contained object.
360  * @param __any A pointer to the object to access.
361  * @return The address of the contained object if <code>
362  * __any != nullptr && __any.type() == typeid(_ValueType)
363  * </code>, otherwise a null pointer.
364  *
365  * @{
366  */
367  template<typename _ValueType>
368  inline const _ValueType* any_cast(const any* __any) noexcept
369  {
370  if (__any)
371  return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
372  return nullptr;
373  }
374 
375  template<typename _ValueType>
376  inline _ValueType* any_cast(any* __any) noexcept
377  {
378  if (__any)
379  return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
380  return nullptr;
381  }
382  // @}
383 
384  template<typename _Tp>
385  void
386  any::_Manager_internal<_Tp>::
387  _S_manage(_Op __which, const any* __any, _Arg* __arg)
388  {
389  // The contained object is in _M_storage._M_buffer
390  auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer);
391  switch (__which)
392  {
393  case _Op_access:
394  __arg->_M_obj = const_cast<_Tp*>(__ptr);
395  break;
396  case _Op_get_type_info:
397 #if __cpp_rtti
398  __arg->_M_typeinfo = &typeid(_Tp);
399 #endif
400  break;
401  case _Op_clone:
402  ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr);
403  break;
404  case _Op_destroy:
405  __ptr->~_Tp();
406  break;
407  }
408  }
409 
410  template<typename _Tp>
411  void
412  any::_Manager_external<_Tp>::
413  _S_manage(_Op __which, const any* __any, _Arg* __arg)
414  {
415  // The contained object is *_M_storage._M_ptr
416  auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr);
417  switch (__which)
418  {
419  case _Op_access:
420  __arg->_M_obj = const_cast<_Tp*>(__ptr);
421  break;
422  case _Op_get_type_info:
423 #if __cpp_rtti
424  __arg->_M_typeinfo = &typeid(_Tp);
425 #endif
426  break;
427  case _Op_clone:
428  __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr);
429  break;
430  case _Op_destroy:
431  delete __ptr;
432  break;
433  }
434  }
435 
436  // @} group any
437 _GLIBCXX_END_NAMESPACE_VERSION
438 } // namespace fundamentals_v1
439 } // namespace experimental
440 } // namespace std
441 
442 #endif // C++14
443 
444 #endif // _GLIBCXX_EXPERIMENTAL_ANY