experimental/any
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// <experimental/any> -*- C++ -*-
// Copyright (C) 2014-2021 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