libstdc++
any
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1// <experimental/any> -*- C++ -*-
2
3// Copyright (C) 2014-2016 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
44namespace std _GLIBCXX_VISIBILITY(default)
45{
46namespace experimental
47{
48inline 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 if (__rhs.empty())
195 clear();
196 else if (this != &__rhs)
197 {
198 if (!empty())
199 _M_manager(_Op_destroy, this, nullptr);
200 _Arg __arg;
201 __arg._M_any = this;
202 __rhs._M_manager(_Op_clone, &__rhs, &__arg);
203 }
204 return *this;
205 }
206
207 /**
208 * @brief Move assignment operator
209 *
210 * @post @c __rhs.empty() (not guaranteed for other implementations)
211 */
212 any& operator=(any&& __rhs) noexcept
213 {
214 if (__rhs.empty())
215 clear();
216 else if (this != &__rhs)
217 {
218 if (!empty())
219 _M_manager(_Op_destroy, this, nullptr);
220 _Arg __arg;
221 __arg._M_any = this;
222 __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
223 }
224 return *this;
225 }
226
227 /// Store a copy of @p __rhs as the contained object.
228 template<typename _ValueType>
229 enable_if_t<!is_same<any, decay_t<_ValueType>>::value, any&>
230 operator=(_ValueType&& __rhs)
231 {
232 *this = any(std::forward<_ValueType>(__rhs));
233 return *this;
234 }
235
236 // modifiers
237
238 /// If not empty, destroy the contained object.
239 void clear() noexcept
240 {
241 if (!empty())
242 {
243 _M_manager(_Op_destroy, this, nullptr);
244 _M_manager = nullptr;
245 }
246 }
247
248 /// Exchange state with another object.
249 void swap(any& __rhs) noexcept
250 {
251 if (empty() && __rhs.empty())
252 return;
253
254 if (!empty() && !__rhs.empty())
255 {
256 if (this == &__rhs)
257 return;
258
259 any __tmp;
260 _Arg __arg;
261 __arg._M_any = &__tmp;
262 __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
263 __arg._M_any = &__rhs;
264 _M_manager(_Op_xfer, this, &__arg);
265 __arg._M_any = this;
266 __tmp._M_manager(_Op_xfer, &__tmp, &__arg);
267 }
268 else
269 {
270 any* __empty = empty() ? this : &__rhs;
271 any* __full = empty() ? &__rhs : this;
272 _Arg __arg;
273 __arg._M_any = __empty;
274 __full->_M_manager(_Op_xfer, __full, &__arg);
275 }
276 }
277
278 // observers
279
280 /// Reports whether there is a contained object or not.
281 bool empty() const noexcept { return _M_manager == nullptr; }
282
283#if __cpp_rtti
284 /// The @c typeid of the contained object, or @c typeid(void) if empty.
285 const type_info& type() const noexcept
286 {
287 if (empty())
288 return typeid(void);
289 _Arg __arg;
290 _M_manager(_Op_get_type_info, this, &__arg);
291 return *__arg._M_typeinfo;
292 }
293#endif
294
295 template<typename _Tp>
296 static constexpr bool __is_valid_cast()
297 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; }
298
299 private:
300 enum _Op {
301 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer
302 };
303
304 union _Arg
305 {
306 void* _M_obj;
307 const std::type_info* _M_typeinfo;
308 any* _M_any;
309 };
310
311 void (*_M_manager)(_Op, const any*, _Arg*);
312 _Storage _M_storage;
313
314 template<typename _Tp>
315 friend void* __any_caster(const any* __any);
316
317 // Manage in-place contained object.
318 template<typename _Tp>
319 struct _Manager_internal
320 {
321 static void
322 _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
323
324 template<typename _Up>
325 static void
326 _S_create(_Storage& __storage, _Up&& __value)
327 {
328 void* __addr = &__storage._M_buffer;
329 ::new (__addr) _Tp(std::forward<_Up>(__value));
330 }
331 };
332
333 // Manage external contained object.
334 template<typename _Tp>
335 struct _Manager_external
336 {
337 static void
338 _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
339
340 template<typename _Up>
341 static void
342 _S_create(_Storage& __storage, _Up&& __value)
343 {
344 __storage._M_ptr = new _Tp(std::forward<_Up>(__value));
345 }
346 };
347 };
348
349 /// Exchange the states of two @c any objects.
350 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); }
351
352 /**
353 * @brief Access the contained object.
354 *
355 * @tparam _ValueType A const-reference or CopyConstructible type.
356 * @param __any The object to access.
357 * @return The contained object.
358 * @throw bad_any_cast If <code>
359 * __any.type() != typeid(remove_reference_t<_ValueType>)
360 * </code>
361 */
362 template<typename _ValueType>
363 inline _ValueType any_cast(const any& __any)
364 {
365 static_assert(any::__is_valid_cast<_ValueType>(),
366 "Template argument must be a reference or CopyConstructible type");
367 auto __p = any_cast<add_const_t<remove_reference_t<_ValueType>>>(&__any);
368 if (__p)
369 return *__p;
370 __throw_bad_any_cast();
371 }
372
373 /**
374 * @brief Access the contained object.
375 *
376 * @tparam _ValueType A reference or CopyConstructible type.
377 * @param __any The object to access.
378 * @return The contained object.
379 * @throw bad_any_cast If <code>
380 * __any.type() != typeid(remove_reference_t<_ValueType>)
381 * </code>
382 *
383 * @{
384 */
385 template<typename _ValueType>
386 inline _ValueType any_cast(any& __any)
387 {
388 static_assert(any::__is_valid_cast<_ValueType>(),
389 "Template argument must be a reference or CopyConstructible type");
390 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any);
391 if (__p)
392 return *__p;
393 __throw_bad_any_cast();
394 }
395
396 template<typename _ValueType,
397 typename enable_if<!is_move_constructible<_ValueType>::value
398 || is_lvalue_reference<_ValueType>::value,
399 bool>::type = true>
400 inline _ValueType any_cast(any&& __any)
401 {
402 static_assert(any::__is_valid_cast<_ValueType>(),
403 "Template argument must be a reference or CopyConstructible type");
404 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any);
405 if (__p)
406 return *__p;
407 __throw_bad_any_cast();
408 }
409
410 template<typename _ValueType,
411 typename enable_if<is_move_constructible<_ValueType>::value
412 && !is_lvalue_reference<_ValueType>::value,
413 bool>::type = false>
414 inline _ValueType any_cast(any&& __any)
415 {
416 static_assert(any::__is_valid_cast<_ValueType>(),
417 "Template argument must be a reference or CopyConstructible type");
418 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any);
419 if (__p)
420 return std::move(*__p);
421 __throw_bad_any_cast();
422 }
423 // @}
424
425 template<typename _Tp>
426 void* __any_caster(const any* __any)
427 {
428 struct _None { };
429 using _Up = decay_t<_Tp>;
430 using _Vp = conditional_t<is_copy_constructible<_Up>::value, _Up, _None>;
431 if (__any->_M_manager != &any::_Manager<_Vp>::_S_manage)
432 return nullptr;
433 any::_Arg __arg;
434 __any->_M_manager(any::_Op_access, __any, &__arg);
435 return __arg._M_obj;
436 }
437
438 /**
439 * @brief Access the contained object.
440 *
441 * @tparam _ValueType The type of the contained object.
442 * @param __any A pointer to the object to access.
443 * @return The address of the contained object if <code>
444 * __any != nullptr && __any.type() == typeid(_ValueType)
445 * </code>, otherwise a null pointer.
446 *
447 * @{
448 */
449 template<typename _ValueType>
450 inline const _ValueType* any_cast(const any* __any) noexcept
451 {
452 if (__any)
453 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
454 return nullptr;
455 }
456
457 template<typename _ValueType>
458 inline _ValueType* any_cast(any* __any) noexcept
459 {
460 if (__any)
461 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
462 return nullptr;
463 }
464 // @}
465
466 template<typename _Tp>
467 void
468 any::_Manager_internal<_Tp>::
469 _S_manage(_Op __which, const any* __any, _Arg* __arg)
470 {
471 // The contained object is in _M_storage._M_buffer
472 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer);
473 switch (__which)
474 {
475 case _Op_access:
476 __arg->_M_obj = const_cast<_Tp*>(__ptr);
477 break;
478 case _Op_get_type_info:
479#if __cpp_rtti
480 __arg->_M_typeinfo = &typeid(_Tp);
481#endif
482 break;
483 case _Op_clone:
484 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr);
485 __arg->_M_any->_M_manager = __any->_M_manager;
486 break;
487 case _Op_destroy:
488 __ptr->~_Tp();
489 break;
490 case _Op_xfer:
491 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr);
492 __ptr->~_Tp();
493 __arg->_M_any->_M_manager = __any->_M_manager;
494 const_cast<any*>(__any)->_M_manager = nullptr;
495 break;
496 }
497 }
498
499 template<typename _Tp>
500 void
501 any::_Manager_external<_Tp>::
502 _S_manage(_Op __which, const any* __any, _Arg* __arg)
503 {
504 // The contained object is *_M_storage._M_ptr
505 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr);
506 switch (__which)
507 {
508 case _Op_access:
509 __arg->_M_obj = const_cast<_Tp*>(__ptr);
510 break;
511 case _Op_get_type_info:
512#if __cpp_rtti
513 __arg->_M_typeinfo = &typeid(_Tp);
514#endif
515 break;
516 case _Op_clone:
517 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr);
518 __arg->_M_any->_M_manager = __any->_M_manager;
519 break;
520 case _Op_destroy:
521 delete __ptr;
522 break;
523 case _Op_xfer:
524 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr;
525 __arg->_M_any->_M_manager = __any->_M_manager;
526 const_cast<any*>(__any)->_M_manager = nullptr;
527 break;
528 }
529 }
530
531 // @} group any
532_GLIBCXX_END_NAMESPACE_VERSION
533} // namespace fundamentals_v1
534} // namespace experimental
535} // namespace std
536
537#endif // C++14
538
539#endif // _GLIBCXX_EXPERIMENTAL_ANY