1// <any> -*- C++ -*-
2
3// Copyright (C) 2014-2018 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 include/any
26 * This is a Standard C++ Library header.
27 */
28
29#ifndef _GLIBCXX_ANY
30#define _GLIBCXX_ANY 1
31
32#pragma GCC system_header
33
34#if __cplusplus >= 201703L
35
36#include <typeinfo>
37#include <new>
38#include <utility>
39#include <type_traits>
40
41namespace std _GLIBCXX_VISIBILITY(default)
42{
43_GLIBCXX_BEGIN_NAMESPACE_VERSION
44
45 /**
46 * @addtogroup utilities
47 * @{
48 */
49
50 /**
51 * @brief Exception class thrown by a failed @c any_cast
52 * @ingroup exceptions
53 */
54 class bad_any_cast : public bad_cast
55 {
56 public:
57 virtual const char* what() const noexcept { return "bad any_cast"; }
58 };
59
60 [[gnu::noreturn]] inline void __throw_bad_any_cast()
61 {
62#if __cpp_exceptions
63 throw bad_any_cast{};
64#else
65 __builtin_abort();
66#endif
67 }
68
69#define __cpp_lib_any 201603
70
71 /**
72 * @brief A type-safe container of any type.
73 *
74 * An @c any object's state is either empty or it stores a contained object
75 * of CopyConstructible type.
76 */
77 class any
78 {
79 // Holds either pointer to a heap object or the contained object itself.
80 union _Storage
81 {
82 constexpr _Storage() : _M_ptr{nullptr} {}
83
84 // Prevent trivial copies of this type, buffer might hold a non-POD.
85 _Storage(const _Storage&) = delete;
86 _Storage& operator=(const _Storage&) = delete;
87
88 void* _M_ptr;
89 aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer;
90 };
91
92 template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>,
93 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage))
94 && (alignof(_Tp) <= alignof(_Storage))>
95 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>;
96
97 template<typename _Tp>
98 struct _Manager_internal; // uses small-object optimization
99
100 template<typename _Tp>
101 struct _Manager_external; // creates contained object on the heap
102
103 template<typename _Tp>
104 using _Manager = conditional_t<_Internal<_Tp>::value,
105 _Manager_internal<_Tp>,
106 _Manager_external<_Tp>>;
107
108 template<typename _Tp, typename _Decayed = decay_t<_Tp>>
109 using _Decay = enable_if_t<!is_same<_Decayed, any>::value, _Decayed>;
110
111 /// Emplace with an object created from @p __args as the contained object.
112 template <typename _Tp, typename... _Args,
113 typename _Mgr = _Manager<_Tp>>
114 void __do_emplace(_Args&&... __args)
115 {
116 reset();
117 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...);
118 _M_manager = &_Mgr::_S_manage;
119 }
120
121 /// Emplace with an object created from @p __il and @p __args as
122 /// the contained object.
123 template <typename _Tp, typename _Up, typename... _Args,
124 typename _Mgr = _Manager<_Tp>>
125 void __do_emplace(initializer_list<_Up> __il, _Args&&... __args)
126 {
127 reset();
128 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...);
129 _M_manager = &_Mgr::_S_manage;
130 }
131
132 public:
133 // construct/destruct
134
135 /// Default constructor, creates an empty object.
136 constexpr any() noexcept : _M_manager(nullptr) { }
137
138 /// Copy constructor, copies the state of @p __other
139 any(const any& __other)
140 {
141 if (!__other.has_value())
142 _M_manager = nullptr;
143 else
144 {
145 _Arg __arg;
146 __arg._M_any = this;
147 __other._M_manager(_Op_clone, &__other, &__arg);
148 }
149 }
150
151 /**
152 * @brief Move constructor, transfer the state from @p __other
153 *
154 * @post @c !__other.has_value() (this postcondition is a GNU extension)
155 */
156 any(any&& __other) noexcept
157 {
158 if (!__other.has_value())
159 _M_manager = nullptr;
160 else
161 {
162 _Arg __arg;
163 __arg._M_any = this;
164 __other._M_manager(_Op_xfer, &__other, &__arg);
165 }
166 }
167
168 template <typename _Res, typename _Tp, typename... _Args>
169 using __any_constructible =
170 enable_if<__and_<is_copy_constructible<_Tp>,
171 is_constructible<_Tp, _Args...>>::value,
172 _Res>;
173
174 template <typename _Tp, typename... _Args>
175 using __any_constructible_t =
176 typename __any_constructible<bool, _Tp, _Args...>::type;
177
178 /// Construct with a copy of @p __value as the contained object.
179 template <typename _ValueType, typename _Tp = _Decay<_ValueType>,
180 typename _Mgr = _Manager<_Tp>,
181 __any_constructible_t<_Tp, _ValueType&&> = true,
182 enable_if_t<!__is_in_place_type<_Tp>::value, bool> = true>
183 any(_ValueType&& __value)
184 : _M_manager(&_Mgr::_S_manage)
185 {
186 _Mgr::_S_create(_M_storage, std::forward<_ValueType>(__value));
187 }
188
189 /// Construct with a copy of @p __value as the contained object.
190 template <typename _ValueType, typename _Tp = _Decay<_ValueType>,
191 typename _Mgr = _Manager<_Tp>,
192 enable_if_t<__and_<is_copy_constructible<_Tp>,
193 __not_<is_constructible<_Tp, _ValueType&&>>,
194 __not_<__is_in_place_type<_Tp>>>::value,
195 bool> = false>
196 any(_ValueType&& __value)
197 : _M_manager(&_Mgr::_S_manage)
198 {
199 _Mgr::_S_create(_M_storage, __value);
200 }
201
202 /// Construct with an object created from @p __args as the contained object.
203 template <typename _ValueType, typename... _Args,
204 typename _Tp = _Decay<_ValueType>,
205 typename _Mgr = _Manager<_Tp>,
206 __any_constructible_t<_Tp, _Args&&...> = false>
207 explicit
208 any(in_place_type_t<_ValueType>, _Args&&... __args)
209 : _M_manager(&_Mgr::_S_manage)
210 {
211 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...);
212 }
213
214 /// Construct with an object created from @p __il and @p __args as
215 /// the contained object.
216 template <typename _ValueType, typename _Up, typename... _Args,
217 typename _Tp = _Decay<_ValueType>,
218 typename _Mgr = _Manager<_Tp>,
219 __any_constructible_t<_Tp, initializer_list<_Up>,
220 _Args&&...> = false>
221 explicit
222 any(in_place_type_t<_ValueType>,
223 initializer_list<_Up> __il, _Args&&... __args)
224 : _M_manager(&_Mgr::_S_manage)
225 {
226 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...);
227 }
228
229 /// Destructor, calls @c reset()
230 ~any() { reset(); }
231
232 // assignments
233
234 /// Copy the state of another object.
235 any& operator=(const any& __rhs)
236 {
237 *this = any(__rhs);
238 return *this;
239 }
240
241 /**
242 * @brief Move assignment operator
243 *
244 * @post @c !__rhs.has_value() (not guaranteed for other implementations)
245 */
246 any& operator=(any&& __rhs) noexcept
247 {
248 if (!__rhs.has_value())
249 reset();
250 else if (this != &__rhs)
251 {
252 reset();
253 _Arg __arg;
254 __arg._M_any = this;
255 __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
256 }
257 return *this;
258 }
259
260 /// Store a copy of @p __rhs as the contained object.
261 template<typename _ValueType>
262 enable_if_t<is_copy_constructible<_Decay<_ValueType>>::value, any&>
263 operator=(_ValueType&& __rhs)
264 {
265 *this = any(std::forward<_ValueType>(__rhs));
266 return *this;
267 }
268
269 /// Emplace with an object created from @p __args as the contained object.
270 template <typename _ValueType, typename... _Args>
271 typename __any_constructible<_Decay<_ValueType>&,
272 _Decay<_ValueType>, _Args&&...>::type
273 emplace(_Args&&... __args)
274 {
275 __do_emplace<_Decay<_ValueType>>(std::forward<_Args>(__args)...);
276 any::_Arg __arg;
277 this->_M_manager(any::_Op_access, this, &__arg);
278 return *static_cast<_Decay<_ValueType>*>(__arg._M_obj);
279 }
280
281 /// Emplace with an object created from @p __il and @p __args as
282 /// the contained object.
283 template <typename _ValueType, typename _Up, typename... _Args>
284 typename __any_constructible<_Decay<_ValueType>&,
285 _Decay<_ValueType>,
286 initializer_list<_Up>,
287 _Args&&...>::type
288 emplace(initializer_list<_Up> __il, _Args&&... __args)
289 {
290 __do_emplace<_Decay<_ValueType>, _Up>(__il,
291 std::forward<_Args>(__args)...);
292 any::_Arg __arg;
293 this->_M_manager(any::_Op_access, this, &__arg);
294 return *static_cast<_Decay<_ValueType>*>(__arg._M_obj);
295 }
296
297 // modifiers
298
299 /// If not empty, destroy the contained object.
300 void reset() noexcept
301 {
302 if (has_value())
303 {
304 _M_manager(_Op_destroy, this, nullptr);
305 _M_manager = nullptr;
306 }
307 }
308
309 /// Exchange state with another object.
310 void swap(any& __rhs) noexcept
311 {
312 if (!has_value() && !__rhs.has_value())
313 return;
314
315 if (has_value() && __rhs.has_value())
316 {
317 if (this == &__rhs)
318 return;
319
320 any __tmp;
321 _Arg __arg;
322 __arg._M_any = &__tmp;
323 __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
324 __arg._M_any = &__rhs;
325 _M_manager(_Op_xfer, this, &__arg);
326 __arg._M_any = this;
327 __tmp._M_manager(_Op_xfer, &__tmp, &__arg);
328 }
329 else
330 {
331 any* __empty = !has_value() ? this : &__rhs;
332 any* __full = !has_value() ? &__rhs : this;
333 _Arg __arg;
334 __arg._M_any = __empty;
335 __full->_M_manager(_Op_xfer, __full, &__arg);
336 }
337 }
338
339 // observers
340
341 /// Reports whether there is a contained object or not.
342 bool has_value() const noexcept { return _M_manager != nullptr; }
343
344#if __cpp_rtti
345 /// The @c typeid of the contained object, or @c typeid(void) if empty.
346 const type_info& type() const noexcept
347 {
348 if (!has_value())
349 return typeid(void);
350 _Arg __arg;
351 _M_manager(_Op_get_type_info, this, &__arg);
352 return *__arg._M_typeinfo;
353 }
354#endif
355
356 template<typename _Tp>
357 static constexpr bool __is_valid_cast()
358 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; }
359
360 private:
361 enum _Op {
362 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer
363 };
364
365 union _Arg
366 {
367 void* _M_obj;
368 const std::type_info* _M_typeinfo;
369 any* _M_any;
370 };
371
372 void (*_M_manager)(_Op, const any*, _Arg*);
373 _Storage _M_storage;
374
375 template<typename _Tp>
376 friend void* __any_caster(const any* __any);
377
378 // Manage in-place contained object.
379 template<typename _Tp>
380 struct _Manager_internal
381 {
382 static void
383 _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
384
385 template<typename _Up>
386 static void
387 _S_create(_Storage& __storage, _Up&& __value)
388 {
389 void* __addr = &__storage._M_buffer;
390 ::new (__addr) _Tp(std::forward<_Up>(__value));
391 }
392
393 template<typename... _Args>
394 static void
395 _S_create(_Storage& __storage, _Args&&... __args)
396 {
397 void* __addr = &__storage._M_buffer;
398 ::new (__addr) _Tp(std::forward<_Args>(__args)...);
399 }
400 };
401
402 // Manage external contained object.
403 template<typename _Tp>
404 struct _Manager_external
405 {
406 static void
407 _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
408
409 template<typename _Up>
410 static void
411 _S_create(_Storage& __storage, _Up&& __value)
412 {
413 __storage._M_ptr = new _Tp(std::forward<_Up>(__value));
414 }
415 template<typename... _Args>
416 static void
417 _S_create(_Storage& __storage, _Args&&... __args)
418 {
419 __storage._M_ptr = new _Tp(std::forward<_Args>(__args)...);
420 }
421 };
422 };
423
424 /// Exchange the states of two @c any objects.
425 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); }
426
427 /// Create an any holding a @c _Tp constructed from @c __args.
428 template <typename _Tp, typename... _Args>
429 any make_any(_Args&&... __args)
430 {
431 return any(in_place_type<_Tp>, std::forward<_Args>(__args)...);
432 }
433
434 /// Create an any holding a @c _Tp constructed from @c __il and @c __args.
435 template <typename _Tp, typename _Up, typename... _Args>
436 any make_any(initializer_list<_Up> __il, _Args&&... __args)
437 {
438 return any(in_place_type<_Tp>, __il, std::forward<_Args>(__args)...);
439 }
440
441 /**
442 * @brief Access the contained object.
443 *
444 * @tparam _ValueType A const-reference or CopyConstructible type.
445 * @param __any The object to access.
446 * @return The contained object.
447 * @throw bad_any_cast If <code>
448 * __any.type() != typeid(remove_reference_t<_ValueType>)
449 * </code>
450 */
451 template<typename _ValueType>
452 inline _ValueType any_cast(const any& __any)
453 {
454 using _Up = remove_cv_t<remove_reference_t<_ValueType>>;
455 static_assert(any::__is_valid_cast<_ValueType>(),
456 "Template argument must be a reference or CopyConstructible type");
457 static_assert(is_constructible_v<_ValueType, const _Up&>,
458 "Template argument must be constructible from a const value.");
459 auto __p = any_cast<_Up>(&__any);
460 if (__p)
461 return static_cast<_ValueType>(*__p);
462 __throw_bad_any_cast();
463 }
464
465 /**
466 * @brief Access the contained object.
467 *
468 * @tparam _ValueType A reference or CopyConstructible type.
469 * @param __any The object to access.
470 * @return The contained object.
471 * @throw bad_any_cast If <code>
472 * __any.type() != typeid(remove_reference_t<_ValueType>)
473 * </code>
474 *
475 * @{
476 */
477 template<typename _ValueType>
478 inline _ValueType any_cast(any& __any)
479 {
480 using _Up = remove_cv_t<remove_reference_t<_ValueType>>;
481 static_assert(any::__is_valid_cast<_ValueType>(),
482 "Template argument must be a reference or CopyConstructible type");
483 static_assert(is_constructible_v<_ValueType, _Up&>,
484 "Template argument must be constructible from an lvalue.");
485 auto __p = any_cast<_Up>(&__any);
486 if (__p)
487 return static_cast<_ValueType>(*__p);
488 __throw_bad_any_cast();
489 }
490
491 template<typename _ValueType>
492 inline _ValueType any_cast(any&& __any)
493 {
494 using _Up = remove_cv_t<remove_reference_t<_ValueType>>;
495 static_assert(any::__is_valid_cast<_ValueType>(),
496 "Template argument must be a reference or CopyConstructible type");
497 static_assert(is_constructible_v<_ValueType, _Up>,
498 "Template argument must be constructible from an rvalue.");
499 auto __p = any_cast<_Up>(&__any);
500 if (__p)
501 return static_cast<_ValueType>(std::move(*__p));
502 __throw_bad_any_cast();
503 }
504 // @}
505
506 template<typename _Tp>
507 void* __any_caster(const any* __any)
508 {
509 if constexpr (is_copy_constructible_v<decay_t<_Tp>>)
510 {
511 if (__any->_M_manager == &any::_Manager<decay_t<_Tp>>::_S_manage)
512 {
513 any::_Arg __arg;
514 __any->_M_manager(any::_Op_access, __any, &__arg);
515 return __arg._M_obj;
516 }
517 }
518 return nullptr;
519 }
520
521 /**
522 * @brief Access the contained object.
523 *
524 * @tparam _ValueType The type of the contained object.
525 * @param __any A pointer to the object to access.
526 * @return The address of the contained object if <code>
527 * __any != nullptr && __any.type() == typeid(_ValueType)
528 * </code>, otherwise a null pointer.
529 *
530 * @{
531 */
532 template<typename _ValueType>
533 inline const _ValueType* any_cast(const any* __any) noexcept
534 {
535 if (__any)
536 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
537 return nullptr;
538 }
539
540 template<typename _ValueType>
541 inline _ValueType* any_cast(any* __any) noexcept
542 {
543 if (__any)
544 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
545 return nullptr;
546 }
547 // @}
548
549 template<typename _Tp>
550 void
551 any::_Manager_internal<_Tp>::
552 _S_manage(_Op __which, const any* __any, _Arg* __arg)
553 {
554 // The contained object is in _M_storage._M_buffer
555 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer);
556 switch (__which)
557 {
558 case _Op_access:
559 __arg->_M_obj = const_cast<_Tp*>(__ptr);
560 break;
561 case _Op_get_type_info:
562#if __cpp_rtti
563 __arg->_M_typeinfo = &typeid(_Tp);
564#endif
565 break;
566 case _Op_clone:
567 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr);
568 __arg->_M_any->_M_manager = __any->_M_manager;
569 break;
570 case _Op_destroy:
571 __ptr->~_Tp();
572 break;
573 case _Op_xfer:
574 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp
575 (std::move(*const_cast<_Tp*>(__ptr)));
576 __ptr->~_Tp();
577 __arg->_M_any->_M_manager = __any->_M_manager;
578 const_cast<any*>(__any)->_M_manager = nullptr;
579 break;
580 }
581 }
582
583 template<typename _Tp>
584 void
585 any::_Manager_external<_Tp>::
586 _S_manage(_Op __which, const any* __any, _Arg* __arg)
587 {
588 // The contained object is *_M_storage._M_ptr
589 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr);
590 switch (__which)
591 {
592 case _Op_access:
593 __arg->_M_obj = const_cast<_Tp*>(__ptr);
594 break;
595 case _Op_get_type_info:
596#if __cpp_rtti
597 __arg->_M_typeinfo = &typeid(_Tp);
598#endif
599 break;
600 case _Op_clone:
601 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr);
602 __arg->_M_any->_M_manager = __any->_M_manager;
603 break;
604 case _Op_destroy:
605 delete __ptr;
606 break;
607 case _Op_xfer:
608 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr;
609 __arg->_M_any->_M_manager = __any->_M_manager;
610 const_cast<any*>(__any)->_M_manager = nullptr;
611 break;
612 }
613 }
614
615 /// @}
616
617_GLIBCXX_END_NAMESPACE_VERSION
618} // namespace std
619
620#endif // C++14
621
622#endif // _GLIBCXX_ANY
623