1// <any> -*- C++ -*-
2
3// Copyright (C) 2014-2020 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 201606L
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 _VTp = decay_t<_Tp>>
109      using _Decay_if_not_any = enable_if_t<!is_same_v<_VTp, any>, _VTp>;
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    template <typename _Res, typename _Tp, typename... _Args>
133      using __any_constructible
134	= enable_if<__and_<is_copy_constructible<_Tp>,
135			   is_constructible<_Tp, _Args...>>::value,
136		    _Res>;
137
138    template <typename _Tp, typename... _Args>
139      using __any_constructible_t
140	= typename __any_constructible<bool, _Tp, _Args...>::type;
141
142    template<typename _VTp, typename... _Args>
143      using __emplace_t
144	= typename __any_constructible<_VTp&, _VTp, _Args...>::type;
145
146  public:
147    // construct/destruct
148
149    /// Default constructor, creates an empty object.
150    constexpr any() noexcept : _M_manager(nullptr) { }
151
152    /// Copy constructor, copies the state of @p __other
153    any(const any& __other)
154    {
155      if (!__other.has_value())
156	_M_manager = nullptr;
157      else
158	{
159	  _Arg __arg;
160	  __arg._M_any = this;
161	  __other._M_manager(_Op_clone, &__other, &__arg);
162	}
163    }
164
165    /**
166     * @brief Move constructor, transfer the state from @p __other
167     *
168     * @post @c !__other.has_value() (this postcondition is a GNU extension)
169     */
170    any(any&& __other) noexcept
171    {
172      if (!__other.has_value())
173	_M_manager = nullptr;
174      else
175	{
176	  _Arg __arg;
177	  __arg._M_any = this;
178	  __other._M_manager(_Op_xfer, &__other, &__arg);
179	}
180    }
181
182    /// Construct with a copy of @p __value as the contained object.
183    template <typename _Tp, typename _VTp = _Decay_if_not_any<_Tp>,
184	      typename _Mgr = _Manager<_VTp>,
185	      enable_if_t<is_copy_constructible<_VTp>::value
186			  && !__is_in_place_type<_VTp>::value, bool> = true>
187      any(_Tp&& __value)
188      : _M_manager(&_Mgr::_S_manage)
189      {
190	_Mgr::_S_create(_M_storage, std::forward<_Tp>(__value));
191      }
192
193    /// Construct with an object created from @p __args as the contained object.
194    template <typename _Tp, typename... _Args, typename _VTp = decay_t<_Tp>,
195	      typename _Mgr = _Manager<_VTp>,
196	      __any_constructible_t<_VTp, _Args&&...> = false>
197      explicit
198      any(in_place_type_t<_Tp>, _Args&&... __args)
199      : _M_manager(&_Mgr::_S_manage)
200      {
201	_Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...);
202      }
203
204    /// Construct with an object created from @p __il and @p __args as
205    /// the contained object.
206    template <typename _Tp, typename _Up, typename... _Args,
207	      typename _VTp = decay_t<_Tp>, typename _Mgr = _Manager<_VTp>,
208	      __any_constructible_t<_VTp, initializer_list<_Up>&,
209				    _Args&&...> = false>
210      explicit
211      any(in_place_type_t<_Tp>, initializer_list<_Up> __il, _Args&&... __args)
212      : _M_manager(&_Mgr::_S_manage)
213      {
214	_Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...);
215      }
216
217    /// Destructor, calls @c reset()
218    ~any() { reset(); }
219
220    // assignments
221
222    /// Copy the state of another object.
223    any&
224    operator=(const any& __rhs)
225    {
226      *this = any(__rhs);
227      return *this;
228    }
229
230    /**
231     * @brief Move assignment operator
232     *
233     * @post @c !__rhs.has_value() (not guaranteed for other implementations)
234     */
235    any&
236    operator=(any&& __rhs) noexcept
237    {
238      if (!__rhs.has_value())
239	reset();
240      else if (this != &__rhs)
241	{
242	  reset();
243	  _Arg __arg;
244	  __arg._M_any = this;
245	  __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
246	}
247      return *this;
248    }
249
250    /// Store a copy of @p __rhs as the contained object.
251    template<typename _Tp>
252      enable_if_t<is_copy_constructible<_Decay_if_not_any<_Tp>>::value, any&>
253      operator=(_Tp&& __rhs)
254      {
255	*this = any(std::forward<_Tp>(__rhs));
256	return *this;
257      }
258
259    /// Emplace with an object created from @p __args as the contained object.
260    template <typename _Tp, typename... _Args>
261      __emplace_t<decay_t<_Tp>, _Args...>
262      emplace(_Args&&... __args)
263      {
264	using _VTp = decay_t<_Tp>;
265	__do_emplace<_VTp>(std::forward<_Args>(__args)...);
266	any::_Arg __arg;
267	this->_M_manager(any::_Op_access, this, &__arg);
268	return *static_cast<_VTp*>(__arg._M_obj);
269      }
270
271    /// Emplace with an object created from @p __il and @p __args as
272    /// the contained object.
273    template <typename _Tp, typename _Up, typename... _Args>
274      __emplace_t<decay_t<_Tp>, initializer_list<_Up>&, _Args&&...>
275      emplace(initializer_list<_Up> __il, _Args&&... __args)
276      {
277	using _VTp = decay_t<_Tp>;
278	__do_emplace<_VTp, _Up>(__il, std::forward<_Args>(__args)...);
279	any::_Arg __arg;
280	this->_M_manager(any::_Op_access, this, &__arg);
281	return *static_cast<_VTp*>(__arg._M_obj);
282      }
283
284    // modifiers
285
286    /// If not empty, destroy the contained object.
287    void reset() noexcept
288    {
289      if (has_value())
290      {
291	_M_manager(_Op_destroy, this, nullptr);
292	_M_manager = nullptr;
293      }
294    }
295
296    /// Exchange state with another object.
297    void swap(any& __rhs) noexcept
298    {
299      if (!has_value() && !__rhs.has_value())
300	return;
301
302      if (has_value() && __rhs.has_value())
303	{
304	  if (this == &__rhs)
305	    return;
306
307	  any __tmp;
308	  _Arg __arg;
309	  __arg._M_any = &__tmp;
310	  __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
311	  __arg._M_any = &__rhs;
312	  _M_manager(_Op_xfer, this, &__arg);
313	  __arg._M_any = this;
314	  __tmp._M_manager(_Op_xfer, &__tmp, &__arg);
315	}
316      else
317	{
318	  any* __empty = !has_value() ? this : &__rhs;
319	  any* __full = !has_value() ? &__rhs : this;
320	  _Arg __arg;
321	  __arg._M_any = __empty;
322	  __full->_M_manager(_Op_xfer, __full, &__arg);
323	}
324    }
325
326    // observers
327
328    /// Reports whether there is a contained object or not.
329    bool has_value() const noexcept { return _M_manager != nullptr; }
330
331#if __cpp_rtti
332    /// The @c typeid of the contained object, or @c typeid(void) if empty.
333    const type_info& type() const noexcept
334    {
335      if (!has_value())
336	return typeid(void);
337      _Arg __arg;
338      _M_manager(_Op_get_type_info, this, &__arg);
339      return *__arg._M_typeinfo;
340    }
341#endif
342
343    template<typename _Tp>
344      static constexpr bool __is_valid_cast()
345      { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; }
346
347  private:
348    enum _Op {
349	_Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer
350    };
351
352    union _Arg
353    {
354	void* _M_obj;
355	const std::type_info* _M_typeinfo;
356	any* _M_any;
357    };
358
359    void (*_M_manager)(_Op, const any*, _Arg*);
360    _Storage _M_storage;
361
362    template<typename _Tp>
363      friend void* __any_caster(const any* __any);
364
365    // Manage in-place contained object.
366    template<typename _Tp>
367      struct _Manager_internal
368      {
369	static void
370	_S_manage(_Op __which, const any* __anyp, _Arg* __arg);
371
372	template<typename _Up>
373	  static void
374	  _S_create(_Storage& __storage, _Up&& __value)
375	  {
376	    void* __addr = &__storage._M_buffer;
377	    ::new (__addr) _Tp(std::forward<_Up>(__value));
378	  }
379
380	template<typename... _Args>
381	  static void
382	  _S_create(_Storage& __storage, _Args&&... __args)
383	  {
384	    void* __addr = &__storage._M_buffer;
385	    ::new (__addr) _Tp(std::forward<_Args>(__args)...);
386	  }
387      };
388
389    // Manage external contained object.
390    template<typename _Tp>
391      struct _Manager_external
392      {
393	static void
394	_S_manage(_Op __which, const any* __anyp, _Arg* __arg);
395
396	template<typename _Up>
397	  static void
398	  _S_create(_Storage& __storage, _Up&& __value)
399	  {
400	    __storage._M_ptr = new _Tp(std::forward<_Up>(__value));
401	  }
402	template<typename... _Args>
403	  static void
404	  _S_create(_Storage& __storage, _Args&&... __args)
405	  {
406	    __storage._M_ptr = new _Tp(std::forward<_Args>(__args)...);
407	  }
408      };
409  };
410
411  /// Exchange the states of two @c any objects.
412  inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); }
413
414  /// Create an any holding a @c _Tp constructed from @c __args.
415  template <typename _Tp, typename... _Args>
416    any make_any(_Args&&... __args)
417    {
418      return any(in_place_type<_Tp>, std::forward<_Args>(__args)...);
419    }
420
421  /// Create an any holding a @c _Tp constructed from @c __il and @c __args.
422  template <typename _Tp, typename _Up, typename... _Args>
423    any make_any(initializer_list<_Up> __il, _Args&&... __args)
424    {
425      return any(in_place_type<_Tp>, __il, std::forward<_Args>(__args)...);
426    }
427
428  /**
429   * @brief Access the contained object.
430   *
431   * @tparam  _ValueType  A const-reference or CopyConstructible type.
432   * @param   __any       The object to access.
433   * @return  The contained object.
434   * @throw   bad_any_cast If <code>
435   *          __any.type() != typeid(remove_reference_t<_ValueType>)
436   *          </code>
437   */
438  template<typename _ValueType>
439    inline _ValueType any_cast(const any& __any)
440    {
441      using _Up = __remove_cvref_t<_ValueType>;
442      static_assert(any::__is_valid_cast<_ValueType>(),
443	  "Template argument must be a reference or CopyConstructible type");
444      static_assert(is_constructible_v<_ValueType, const _Up&>,
445	  "Template argument must be constructible from a const value.");
446      auto __p = any_cast<_Up>(&__any);
447      if (__p)
448	return static_cast<_ValueType>(*__p);
449      __throw_bad_any_cast();
450    }
451
452  /**
453   * @brief Access the contained object.
454   *
455   * @tparam  _ValueType  A reference or CopyConstructible type.
456   * @param   __any       The object to access.
457   * @return  The contained object.
458   * @throw   bad_any_cast If <code>
459   *          __any.type() != typeid(remove_reference_t<_ValueType>)
460   *          </code>
461   *
462   * @{
463   */
464  template<typename _ValueType>
465    inline _ValueType any_cast(any& __any)
466    {
467      using _Up = __remove_cvref_t<_ValueType>;
468      static_assert(any::__is_valid_cast<_ValueType>(),
469	  "Template argument must be a reference or CopyConstructible type");
470      static_assert(is_constructible_v<_ValueType, _Up&>,
471	  "Template argument must be constructible from an lvalue.");
472      auto __p = any_cast<_Up>(&__any);
473      if (__p)
474	return static_cast<_ValueType>(*__p);
475      __throw_bad_any_cast();
476    }
477
478  template<typename _ValueType>
479    inline _ValueType any_cast(any&& __any)
480    {
481      using _Up = __remove_cvref_t<_ValueType>;
482      static_assert(any::__is_valid_cast<_ValueType>(),
483	  "Template argument must be a reference or CopyConstructible type");
484      static_assert(is_constructible_v<_ValueType, _Up>,
485	  "Template argument must be constructible from an rvalue.");
486      auto __p = any_cast<_Up>(&__any);
487      if (__p)
488	return static_cast<_ValueType>(std::move(*__p));
489      __throw_bad_any_cast();
490    }
491  /// @}
492
493  /// @cond undocumented
494  template<typename _Tp>
495    void* __any_caster(const any* __any)
496    {
497      // any_cast<T> returns non-null if __any->type() == typeid(T) and
498      // typeid(T) ignores cv-qualifiers so remove them:
499      using _Up = remove_cv_t<_Tp>;
500      // The contained value has a decayed type, so if decay_t<U> is not U,
501      // then it's not possible to have a contained value of type U:
502      if constexpr (!is_same_v<decay_t<_Up>, _Up>)
503	return nullptr;
504      // Only copy constructible types can be used for contained values:
505      else if constexpr (!is_copy_constructible_v<_Up>)
506	return nullptr;
507      // First try comparing function addresses, which works without RTTI
508      else if (__any->_M_manager == &any::_Manager<_Up>::_S_manage
509#if __cpp_rtti
510	  || __any->type() == typeid(_Tp)
511#endif
512	  )
513	{
514	  any::_Arg __arg;
515	  __any->_M_manager(any::_Op_access, __any, &__arg);
516	  return __arg._M_obj;
517	}
518      return nullptr;
519    }
520  /// @endcond
521
522  /**
523   * @brief Access the contained object.
524   *
525   * @tparam  _ValueType  The type of the contained object.
526   * @param   __any       A pointer to the object to access.
527   * @return  The address of the contained object if <code>
528   *          __any != nullptr && __any.type() == typeid(_ValueType)
529   *          </code>, otherwise a null pointer.
530   *
531   * @{
532   */
533  template<typename _ValueType>
534    inline const _ValueType* any_cast(const any* __any) noexcept
535    {
536      if constexpr (is_object_v<_ValueType>)
537	if (__any)
538	  return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
539      return nullptr;
540    }
541
542  template<typename _ValueType>
543    inline _ValueType* any_cast(any* __any) noexcept
544    {
545      if constexpr (is_object_v<_ValueType>)
546	if (__any)
547	  return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
548      return nullptr;
549    }
550  /// @}
551
552  template<typename _Tp>
553    void
554    any::_Manager_internal<_Tp>::
555    _S_manage(_Op __which, const any* __any, _Arg* __arg)
556    {
557      // The contained object is in _M_storage._M_buffer
558      auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer);
559      switch (__which)
560      {
561      case _Op_access:
562	__arg->_M_obj = const_cast<_Tp*>(__ptr);
563	break;
564      case _Op_get_type_info:
565#if __cpp_rtti
566	__arg->_M_typeinfo = &typeid(_Tp);
567#endif
568	break;
569      case _Op_clone:
570	::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr);
571	__arg->_M_any->_M_manager = __any->_M_manager;
572	break;
573      case _Op_destroy:
574	__ptr->~_Tp();
575	break;
576      case _Op_xfer:
577	::new(&__arg->_M_any->_M_storage._M_buffer) _Tp
578	  (std::move(*const_cast<_Tp*>(__ptr)));
579	__ptr->~_Tp();
580	__arg->_M_any->_M_manager = __any->_M_manager;
581	const_cast<any*>(__any)->_M_manager = nullptr;
582	break;
583      }
584    }
585
586  template<typename _Tp>
587    void
588    any::_Manager_external<_Tp>::
589    _S_manage(_Op __which, const any* __any, _Arg* __arg)
590    {
591      // The contained object is *_M_storage._M_ptr
592      auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr);
593      switch (__which)
594      {
595      case _Op_access:
596	__arg->_M_obj = const_cast<_Tp*>(__ptr);
597	break;
598      case _Op_get_type_info:
599#if __cpp_rtti
600	__arg->_M_typeinfo = &typeid(_Tp);
601#endif
602	break;
603      case _Op_clone:
604	__arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr);
605	__arg->_M_any->_M_manager = __any->_M_manager;
606	break;
607      case _Op_destroy:
608	delete __ptr;
609	break;
610      case _Op_xfer:
611	__arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr;
612	__arg->_M_any->_M_manager = __any->_M_manager;
613	const_cast<any*>(__any)->_M_manager = nullptr;
614	break;
615      }
616    }
617
618  /// @}
619
620  namespace __detail::__variant
621  {
622    template<typename> struct _Never_valueless_alt; // see <variant>
623
624    // Provide the strong exception-safety guarantee when emplacing an
625    // any into a variant.
626    template<>
627      struct _Never_valueless_alt<std::any>
628      : std::true_type
629      { };
630  }  // namespace __detail::__variant
631
632_GLIBCXX_END_NAMESPACE_VERSION
633} // namespace std
634
635#endif // C++17
636#endif // _GLIBCXX_ANY
637