// <experimental/any> -*- C++ -*- // Copyright (C) 2014-2020 Free Software Foundation, Inc. // // This file is part of the GNU ISO C++ Library. This library is free // software; you can redistribute it and/or modify it under the // terms of the GNU General Public License as published by the // Free Software Foundation; either version 3, or (at your option) // any later version. // This library is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // Under Section 7 of GPL version 3, you are granted additional // permissions described in the GCC Runtime Library Exception, version // 3.1, as published by the Free Software Foundation. // You should have received a copy of the GNU General Public License and // a copy of the GCC Runtime Library Exception along with this program; // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see // <http://www.gnu.org/licenses/>. /** @file experimental/any * This is a TS C++ Library header. * @ingroup libfund-ts */ #ifndef _GLIBCXX_EXPERIMENTAL_ANY #define _GLIBCXX_EXPERIMENTAL_ANY 1 #pragma GCC system_header #if __cplusplus >= 201402L #include <typeinfo> #include <new> #include <utility> #include <type_traits> #include <experimental/bits/lfts_config.h> namespace std _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION namespace experimental { inline namespace fundamentals_v1 { /** * @defgroup any Type-safe container of any type * @ingroup libfund-ts * * A type-safe container for single values of value types, as * described in n3804 "Any Library Proposal (Revision 3)". * * @{ */ #define __cpp_lib_experimental_any 201411 /** * @brief Exception class thrown by a failed @c any_cast * @ingroup exceptions */ class bad_any_cast : public bad_cast { public: virtual const char* what() const noexcept { return "bad any_cast"; } }; /// @cond undocumented [[gnu::noreturn]] inline void __throw_bad_any_cast() { #if __cpp_exceptions throw bad_any_cast{}; #else __builtin_abort(); #endif } /// @endcond /** * @brief A type-safe container of any type. * * An @c any object's state is either empty or it stores a contained object * of CopyConstructible type. */ class any { // Holds either pointer to a heap object or the contained object itself. union _Storage { // This constructor intentionally doesn't initialize anything. _Storage() = default; // Prevent trivial copies of this type, buffer might hold a non-POD. _Storage(const _Storage&) = delete; _Storage& operator=(const _Storage&) = delete; void* _M_ptr; aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer; }; template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>, bool _Fits = (sizeof(_Tp) <= sizeof(_Storage)) && (alignof(_Tp) <= alignof(_Storage))> using _Internal = std::integral_constant<bool, _Safe::value && _Fits>; template<typename _Tp> struct _Manager_internal; // uses small-object optimization template<typename _Tp> struct _Manager_external; // creates contained object on the heap template<typename _Tp> using _Manager = conditional_t<_Internal<_Tp>::value, _Manager_internal<_Tp>, _Manager_external<_Tp>>; template<typename _Tp, typename _Decayed = decay_t<_Tp>> using _Decay = enable_if_t<!is_same<_Decayed, any>::value, _Decayed>; public: // construct/destruct /// Default constructor, creates an empty object. any() noexcept : _M_manager(nullptr) { } /// Copy constructor, copies the state of @p __other any(const any& __other) { if (__other.empty()) _M_manager = nullptr; else { _Arg __arg; __arg._M_any = this; __other._M_manager(_Op_clone, &__other, &__arg); } } /** * @brief Move constructor, transfer the state from @p __other * * @post @c __other.empty() (this postcondition is a GNU extension) */ any(any&& __other) noexcept { if (__other.empty()) _M_manager = nullptr; else { _Arg __arg; __arg._M_any = this; __other._M_manager(_Op_xfer, &__other, &__arg); } } /// Construct with a copy of @p __value as the contained object. template <typename _ValueType, typename _Tp = _Decay<_ValueType>, typename _Mgr = _Manager<_Tp>, typename enable_if<is_constructible<_Tp, _ValueType&&>::value, bool>::type = true> any(_ValueType&& __value) : _M_manager(&_Mgr::_S_manage) { _Mgr::_S_create(_M_storage, std::forward<_ValueType>(__value)); static_assert(is_copy_constructible<_Tp>::value, "The contained object must be CopyConstructible"); } /// Construct with a copy of @p __value as the contained object. template <typename _ValueType, typename _Tp = _Decay<_ValueType>, typename _Mgr = _Manager<_Tp>, typename enable_if<!is_constructible<_Tp, _ValueType&&>::value, bool>::type = false> any(_ValueType&& __value) : _M_manager(&_Mgr::_S_manage) { _Mgr::_S_create(_M_storage, __value); static_assert(is_copy_constructible<_Tp>::value, "The contained object must be CopyConstructible"); } /// Destructor, calls @c clear() ~any() { clear(); } // assignments /// Copy the state of another object. any& operator=(const any& __rhs) { *this = any(__rhs); return *this; } /** * @brief Move assignment operator * * @post @c __rhs.empty() (not guaranteed for other implementations) */ any& operator=(any&& __rhs) noexcept { if (__rhs.empty()) clear(); else if (this != &__rhs) { clear(); _Arg __arg; __arg._M_any = this; __rhs._M_manager(_Op_xfer, &__rhs, &__arg); } return *this; } /// Store a copy of @p __rhs as the contained object. template<typename _ValueType> enable_if_t<!is_same<any, decay_t<_ValueType>>::value, any&> operator=(_ValueType&& __rhs) { *this = any(std::forward<_ValueType>(__rhs)); return *this; } // modifiers /// If not empty, destroy the contained object. void clear() noexcept { if (!empty()) { _M_manager(_Op_destroy, this, nullptr); _M_manager = nullptr; } } /// Exchange state with another object. void swap(any& __rhs) noexcept { if (empty() && __rhs.empty()) return; if (!empty() && !__rhs.empty()) { if (this == &__rhs) return; any __tmp; _Arg __arg; __arg._M_any = &__tmp; __rhs._M_manager(_Op_xfer, &__rhs, &__arg); __arg._M_any = &__rhs; _M_manager(_Op_xfer, this, &__arg); __arg._M_any = this; __tmp._M_manager(_Op_xfer, &__tmp, &__arg); } else { any* __empty = empty() ? this : &__rhs; any* __full = empty() ? &__rhs : this; _Arg __arg; __arg._M_any = __empty; __full->_M_manager(_Op_xfer, __full, &__arg); } } // observers /// Reports whether there is a contained object or not. _GLIBCXX_NODISCARD bool empty() const noexcept { return _M_manager == nullptr; } #if __cpp_rtti /// The @c typeid of the contained object, or @c typeid(void) if empty. const type_info& type() const noexcept { if (empty()) return typeid(void); _Arg __arg; _M_manager(_Op_get_type_info, this, &__arg); return *__arg._M_typeinfo; } #endif template<typename _Tp> static constexpr bool __is_valid_cast() { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; } private: enum _Op { _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer }; union _Arg { void* _M_obj; const std::type_info* _M_typeinfo; any* _M_any; }; void (*_M_manager)(_Op, const any*, _Arg*); _Storage _M_storage; template<typename _Tp> friend enable_if_t<is_object<_Tp>::value, void*> __any_caster(const any* __any); // Manage in-place contained object. template<typename _Tp> struct _Manager_internal { static void _S_manage(_Op __which, const any* __anyp, _Arg* __arg); template<typename _Up> static void _S_create(_Storage& __storage, _Up&& __value) { void* __addr = &__storage._M_buffer; ::new (__addr) _Tp(std::forward<_Up>(__value)); } }; // Manage external contained object. template<typename _Tp> struct _Manager_external { static void _S_manage(_Op __which, const any* __anyp, _Arg* __arg); template<typename _Up> static void _S_create(_Storage& __storage, _Up&& __value) { __storage._M_ptr = new _Tp(std::forward<_Up>(__value)); } }; }; /// Exchange the states of two @c any objects. inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); } /** * @brief Access the contained object. * * @tparam _ValueType A const-reference or CopyConstructible type. * @param __any The object to access. * @return The contained object. * @throw bad_any_cast If <code> * __any.type() != typeid(remove_reference_t<_ValueType>) * </code> */ template<typename _ValueType> inline _ValueType any_cast(const any& __any) { static_assert(any::__is_valid_cast<_ValueType>(), "Template argument must be a reference or CopyConstructible type"); auto __p = any_cast<add_const_t<remove_reference_t<_ValueType>>>(&__any); if (__p) return *__p; __throw_bad_any_cast(); } /** * @brief Access the contained object. * * @tparam _ValueType A reference or CopyConstructible type. * @param __any The object to access. * @return The contained object. * @throw bad_any_cast If <code> * __any.type() != typeid(remove_reference_t<_ValueType>) * </code> * * @{ */ template<typename _ValueType> inline _ValueType any_cast(any& __any) { static_assert(any::__is_valid_cast<_ValueType>(), "Template argument must be a reference or CopyConstructible type"); auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); if (__p) return *__p; __throw_bad_any_cast(); } template<typename _ValueType, typename enable_if<!is_move_constructible<_ValueType>::value || is_lvalue_reference<_ValueType>::value, bool>::type = true> inline _ValueType any_cast(any&& __any) { static_assert(any::__is_valid_cast<_ValueType>(), "Template argument must be a reference or CopyConstructible type"); auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); if (__p) return *__p; __throw_bad_any_cast(); } template<typename _ValueType, typename enable_if<is_move_constructible<_ValueType>::value && !is_lvalue_reference<_ValueType>::value, bool>::type = false> inline _ValueType any_cast(any&& __any) { static_assert(any::__is_valid_cast<_ValueType>(), "Template argument must be a reference or CopyConstructible type"); auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); if (__p) return std::move(*__p); __throw_bad_any_cast(); } // @} /// @cond undocumented template<typename _Tp> enable_if_t<is_object<_Tp>::value, void*> __any_caster(const any* __any) { // any_cast<T> returns non-null if __any->type() == typeid(T) and // typeid(T) ignores cv-qualifiers so remove them: using _Up = remove_cv_t<_Tp>; // The contained value has a decayed type, so if decay_t<U> is not U, // then it's not possible to have a contained value of type U. using __does_not_decay = is_same<decay_t<_Up>, _Up>; // Only copy constructible types can be used for contained values. using __is_copyable = is_copy_constructible<_Up>; // If the type _Tp could never be stored in an any we don't want to // instantiate _Manager<_Tp>, so use _Manager<any::_Op> instead, which // is explicitly specialized and has a no-op _S_manage function. using _Vp = conditional_t<__and_<__does_not_decay, __is_copyable>::value, _Up, any::_Op>; // First try comparing function addresses, which works without RTTI if (__any->_M_manager == &any::_Manager<_Vp>::_S_manage #if __cpp_rtti || __any->type() == typeid(_Tp) #endif ) { any::_Arg __arg; __any->_M_manager(any::_Op_access, __any, &__arg); return __arg._M_obj; } return nullptr; } // This overload exists so that std::any_cast<void(*)()>(a) is well-formed. template<typename _Tp> enable_if_t<!is_object<_Tp>::value, _Tp*> __any_caster(const any*) noexcept { return nullptr; } /// @endcond /** * @brief Access the contained object. * * @tparam _ValueType The type of the contained object. * @param __any A pointer to the object to access. * @return The address of the contained object if <code> * __any != nullptr && __any.type() == typeid(_ValueType) * </code>, otherwise a null pointer. * * @{ */ template<typename _ValueType> inline const _ValueType* any_cast(const any* __any) noexcept { if (__any) return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); return nullptr; } template<typename _ValueType> inline _ValueType* any_cast(any* __any) noexcept { if (__any) return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); return nullptr; } // @} template<typename _Tp> void any::_Manager_internal<_Tp>:: _S_manage(_Op __which, const any* __any, _Arg* __arg) { // The contained object is in _M_storage._M_buffer auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer); switch (__which) { case _Op_access: __arg->_M_obj = const_cast<_Tp*>(__ptr); break; case _Op_get_type_info: #if __cpp_rtti __arg->_M_typeinfo = &typeid(_Tp); #endif break; case _Op_clone: ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr); __arg->_M_any->_M_manager = __any->_M_manager; break; case _Op_destroy: __ptr->~_Tp(); break; case _Op_xfer: ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp (std::move(*const_cast<_Tp*>(__ptr))); __ptr->~_Tp(); __arg->_M_any->_M_manager = __any->_M_manager; const_cast<any*>(__any)->_M_manager = nullptr; break; } } template<typename _Tp> void any::_Manager_external<_Tp>:: _S_manage(_Op __which, const any* __any, _Arg* __arg) { // The contained object is *_M_storage._M_ptr auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr); switch (__which) { case _Op_access: __arg->_M_obj = const_cast<_Tp*>(__ptr); break; case _Op_get_type_info: #if __cpp_rtti __arg->_M_typeinfo = &typeid(_Tp); #endif break; case _Op_clone: __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr); __arg->_M_any->_M_manager = __any->_M_manager; break; case _Op_destroy: delete __ptr; break; case _Op_xfer: __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr; __arg->_M_any->_M_manager = __any->_M_manager; const_cast<any*>(__any)->_M_manager = nullptr; break; } } // Dummy specialization used by __any_caster. template<> struct any::_Manager_internal<any::_Op> { static void _S_manage(_Op, const any*, _Arg*) { } }; // @} group any } // namespace fundamentals_v1 } // namespace experimental _GLIBCXX_END_NAMESPACE_VERSION } // namespace std #endif // C++14 #endif // _GLIBCXX_EXPERIMENTAL_ANY