Boost C++ Libraries

boost/serialization/void_cast.hpp

#ifndef  BOOST_SERIALIZATION_VOID_CAST_HPP
#define BOOST_SERIALIZATION_VOID_CAST_HPP

// MS compatible compilers support #pragma once
#if defined(_MSC_VER) && (_MSC_VER >= 1020)
# pragma once
#endif

/////////1/////////2/////////3/////////4/////////5/////////6/////////7/////////8
// void_cast.hpp:   interface for run-time casting of void pointers.

// (C) Copyright 2002 Robert Ramey - http://www.rrsd.com . 
// Use, modification and distribution is subject to 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)
// gennadiy.rozental@tfn.com

//  See http://www.boost.org for updates, documentation, and revision history.

#include <boost/smart_cast.hpp>
#include <boost/serialization/singleton.hpp>
#include <boost/serialization/force_include.hpp>
#include <boost/serialization/type_info_implementation.hpp>
#include <boost/serialization/config.hpp>
#include <boost/serialization/force_include.hpp>
#include <boost/config/abi_prefix.hpp> // must be the last header

#ifdef BOOST_MSVC
#  pragma warning(push)
#  pragma warning(disable : 4251 4231 4660 4275)
#endif

namespace boost { 
namespace serialization { 

BOOST_SERIALIZATION_DECL(BOOST_PP_EMPTY()) class extended_type_info;

// Given a void *, assume that it really points to an instance of one type
// and alter it so that it would point to an instance of a related type.
// Return the altered pointer. If there exists no sequence of casts that
// can transform from_type to to_type, return a NULL.  

BOOST_SERIALIZATION_DECL(void const *)
void_upcast(
    extended_type_info const & derived,  
    extended_type_info const & base, 
    void const * const t
);

inline void *
void_upcast(
    extended_type_info const & derived,
    extended_type_info const & base,
    void * const t 
){
    return const_cast<void*>(void_upcast(
        derived, 
        base, 
        const_cast<void const *>(t)
    ));
}

BOOST_SERIALIZATION_DECL(void const *)
void_downcast(
    extended_type_info const & derived,  
    extended_type_info const & base, 
    void const * const t
);

inline void *
void_downcast(
    extended_type_info const & derived,
    extended_type_info const & base,
    void * const t 
){
    return const_cast<void*>(void_downcast(
        derived, 
        base, 
        const_cast<void const *>(t)
    ));
}

namespace void_cast_detail {

class BOOST_SERIALIZATION_DECL(BOOST_PP_EMPTY()) void_caster
{
    friend struct void_caster_compare ;
    friend 
    BOOST_SERIALIZATION_DECL(void const *)
    boost::serialization::void_upcast(
        extended_type_info const & derived,
        extended_type_info const & base,
        void const * const
    );
    friend 
    BOOST_SERIALIZATION_DECL(void const *)  
    boost::serialization::void_downcast(
        extended_type_info const & derived,
        extended_type_info const & base,
        void const * const
    );
    // Data members
    const extended_type_info & m_derived;
    const extended_type_info & m_base;
    // each derived class must re-implement these;
    virtual void const * upcast(void const * const t) const = 0;
    virtual void const * downcast(void const * const t) const = 0;
    // cw 8.3 requires this!!
    void_caster& operator=(void_caster const &);
protected:
    void
    static_register() const;
    void
    static_unregister() const;
public:
    // Constructor
    void_caster(
        extended_type_info const & derived,
        extended_type_info const & base
    );
    virtual ~void_caster(){};
    bool operator==(const void_caster & rhs) const;
};

template <class Derived, class Base>
class void_caster_primitive : 
    public void_caster
{
    virtual void const * downcast(void const * const t) const {
        const Derived * d = boost::smart_cast<const Derived *, const Base *>(
            static_cast<const Base *>(t)
        );
        return d;
    }
    virtual void const * upcast(void const * const t) const {
        const Base * b = boost::smart_cast<const Base *, const Derived *>(
            static_cast<const Derived *>(t)
        );
        return b;
    }
public:
    BOOST_DLLEXPORT void_caster_primitive() BOOST_USED;
    ~void_caster_primitive();
};

template <class Derived, class Base>
BOOST_DLLEXPORT void_caster_primitive<Derived, Base>::void_caster_primitive() :
    void_caster( 
        type_info_implementation<Derived>::type::get_const_instance(), 
        type_info_implementation<Base>::type::get_const_instance()
    )
{
    static_register();
}

template <class Derived, class Base>
void_caster_primitive<Derived, Base>::~void_caster_primitive(){
    static_unregister();
}

} // void_cast_detail 

// Register a base/derived pair.  This indicates that it is possible
// to upcast a void pointer from Derived to Base and downcast a
// void pointer from Base to Derived.  Note bogus arguments to workaround
// bug in msvc 6.0
template<class Derived, class Base>
BOOST_DLLEXPORT 
inline const void_cast_detail::void_caster & void_cast_register(
    const Derived * dnull, 
    const Base * bnull
) BOOST_USED;

template<class Derived, class Base>
BOOST_DLLEXPORT 
inline const void_cast_detail::void_caster & void_cast_register(
    Derived const * /* dnull = NULL */, 
    Base const * /* bnull = NULL */
){
    return singleton<void_cast_detail::void_caster_primitive<
        Derived, Base
    > >::get_const_instance();
}

} // namespace serialization
} // namespace boost

#ifdef BOOST_MSVC  
#  pragma warning(pop)  
#endif

#include <boost/config/abi_suffix.hpp> // pops abi_suffix.hpp pragmas

#endif // BOOST_SERIALIZATION_VOID_CAST_HPP