boost/any.hpp
// See http://www.boost.org/libs/any for Documentation.
#ifndef BOOST_ANY_INCLUDED
#define BOOST_ANY_INCLUDED
// what: variant type boost::any
// who: contributed by Kevlin Henney,
// with features contributed and bugs found by
// Ed Brey, Mark Rodgers, Peter Dimov, and James Curran
// when: July 2001
// where: tested with BCC 5.5, MSVC 6.0, and g++ 2.95
#include <algorithm>
#include <typeinfo>
#include "boost/config.hpp"
#include <boost/type_traits/remove_reference.hpp>
#include <boost/type_traits/is_reference.hpp>
#include <boost/throw_exception.hpp>
#include <boost/static_assert.hpp>
namespace boost
{
class any
{
public: // structors
any()
: content(0)
{
}
template<typename ValueType>
any(const ValueType & value)
: content(new holder<ValueType>(value))
{
}
any(const any & other)
: content(other.content ? other.content->clone() : 0)
{
}
~any()
{
delete content;
}
public: // modifiers
any & swap(any & rhs)
{
std::swap(content, rhs.content);
return *this;
}
template<typename ValueType>
any & operator=(const ValueType & rhs)
{
any(rhs).swap(*this);
return *this;
}
any & operator=(any rhs)
{
rhs.swap(*this);
return *this;
}
public: // queries
bool empty() const
{
return !content;
}
const std::type_info & type() const
{
return content ? content->type() : typeid(void);
}
#ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
private: // types
#else
public: // types (public so any_cast can be non-friend)
#endif
class placeholder
{
public: // structors
virtual ~placeholder()
{
}
public: // queries
virtual const std::type_info & type() const = 0;
virtual placeholder * clone() const = 0;
};
template<typename ValueType>
class holder : public placeholder
{
public: // structors
holder(const ValueType & value)
: held(value)
{
}
public: // queries
virtual const std::type_info & type() const
{
return typeid(ValueType);
}
virtual placeholder * clone() const
{
return new holder(held);
}
public: // representation
ValueType held;
private: // intentionally left unimplemented
holder & operator=(const holder &);
};
#ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS
private: // representation
template<typename ValueType>
friend ValueType * any_cast(any *);
template<typename ValueType>
friend ValueType * unsafe_any_cast(any *);
#else
public: // representation (public so any_cast can be non-friend)
#endif
placeholder * content;
};
class bad_any_cast : public std::bad_cast
{
public:
virtual const char * what() const throw()
{
return "boost::bad_any_cast: "
"failed conversion using boost::any_cast";
}
};
template<typename ValueType>
ValueType * any_cast(any * operand)
{
return operand && operand->type() == typeid(ValueType)
? &static_cast<any::holder<ValueType> *>(operand->content)->held
: 0;
}
template<typename ValueType>
inline const ValueType * any_cast(const any * operand)
{
return any_cast<ValueType>(const_cast<any *>(operand));
}
template<typename ValueType>
ValueType any_cast(any & operand)
{
typedef BOOST_DEDUCED_TYPENAME remove_reference<ValueType>::type nonref;
#ifdef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
// If 'nonref' is still reference type, it means the user has not
// specialized 'remove_reference'.
// Please use BOOST_BROKEN_COMPILER_TYPE_TRAITS_SPECIALIZATION macro
// to generate specialization of remove_reference for your class
// See type traits library documentation for details
BOOST_STATIC_ASSERT(!is_reference<nonref>::value);
#endif
nonref * result = any_cast<nonref>(&operand);
if(!result)
boost::throw_exception(bad_any_cast());
return *result;
}
template<typename ValueType>
inline ValueType any_cast(const any & operand)
{
typedef BOOST_DEDUCED_TYPENAME remove_reference<ValueType>::type nonref;
#ifdef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
// The comment in the above version of 'any_cast' explains when this
// assert is fired and what to do.
BOOST_STATIC_ASSERT(!is_reference<nonref>::value);
#endif
return any_cast<const nonref &>(const_cast<any &>(operand));
}
// Note: The "unsafe" versions of any_cast are not part of the
// public interface and may be removed at any time. They are
// required where we know what type is stored in the any and can't
// use typeid() comparison, e.g., when our types may travel across
// different shared libraries.
template<typename ValueType>
inline ValueType * unsafe_any_cast(any * operand)
{
return &static_cast<any::holder<ValueType> *>(operand->content)->held;
}
template<typename ValueType>
inline const ValueType * unsafe_any_cast(const any * operand)
{
return unsafe_any_cast<ValueType>(const_cast<any *>(operand));
}
}
// Copyright Kevlin Henney, 2000, 2001, 2002. All rights reserved.
//
// Distributed under the Boost Software License, Version 1.0. (See
// accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
#endif