path: root/src/stable/variant.h

/*
 * Copyright (C) 2007-2023 Xagasoft, All rights reserved.
 *
 * This file is part of the libbu++ library and is released under the
 * terms of the license contained in the file LICENSE.
 */

#ifndef BU_VARIANT_H
#define BU_VARIANT_H

//#include <bu/string.h>
#include <typeinfo>
// #include <bu/formatter.h>

#ifndef NULL
#define NULL (0L)
#endif

#include "bu/exceptionbase.h"

namespace Bu
{
    class String;
    class Formatter;
    class Variant;
    /** @cond DEVEL */
    template<class t> class VariantType;

    class VariantTypeRoot
    {
    public:
        VariantTypeRoot();
        virtual ~VariantTypeRoot();

        virtual const std::type_info &getType() const=0;
        virtual VariantTypeRoot *clone() const=0;
        virtual void format( Bu::Formatter &f ) const=0;
        virtual const void *rawData() const=0;
    };

    template<class t>
    class VariantType : public VariantTypeRoot
    {
        friend class Variant;
    private:
        VariantType()
        {
        }

        VariantType( const t &d ) : 
            data( d )
        {
        }

        VariantType( const VariantType<t> &vt ) :
            data( vt.data )
        {
        }

        virtual ~VariantType()
        {
        }

    public:
        t &getData()
        {
            return data;
        }
        
        const t &getData() const
        {
            return data;
        }

        virtual void format( Formatter &f ) const
        {
            f << data;
        }
        
        virtual const void *rawData() const
        {
            return &data;
        }

        virtual const std::type_info &getType() const
        {
            return typeid( data );
        }

        VariantType<t> operator=( const t &rhs )
        {
            data = rhs;

            return *this;
        }

        virtual VariantTypeRoot *clone() const
        {
            return new VariantType<t>( *this );
        }

    private:
        t data;
    };
    /** @endcond */

    /**
     * Store any data type and access it safely.  Variant gives you a way to
     * pass arbitrary data types around without having to worry about what
     * type a variable is.  It allows code to be easily extended and to manage
     * data without having to know what type it is ahead of time.
     *
     * Because of the generic method that this class was implemented it may seem
     * to have some drawbacks compared to other Variant classes you may have
     * seen, however it is fairly easy to get it to do just about anything you
     * may need.  It is also very low overhead.  On most compilers the class
     * itself has only 3 words of overhead + the size of the variable you store
     * in it.  And, since many parts of it are templatized they can often be
     * optimized quite a bit.
     */
    class Variant
    {
    friend Bu::Formatter &operator<<( Bu::Formatter &f, const Variant &v );
    public:
        Variant();
        Variant( const Variant &v );
        Variant( const char *t );
        template<class t>
        Variant( const t &v ) :
            pCore( new VariantType<t>() )
        {
            (*dynamic_cast<VariantType<t> *>(pCore)) = v;
        }
        virtual ~Variant();

        Bu::String toString() const;
        bool isSet() const;
        const std::type_info &getType() const;

        Variant &operator=( const Variant &rhs );

        template<class t>
        Variant &operator=( const t &rhs )
        {
            if( pCore ) // && pCore->getType() != typeid(t) )
            {
                delete pCore;
                pCore = NULL;
            }
            pCore = new VariantType<t>();
            (*dynamic_cast<VariantType<t> *>(pCore)) = rhs;
            return *this;
        }

        template<class t>
        t &get()
        {
            if( !pCore )
            {
                throw Bu::ExceptionBase("No data!");
            }
            if( pCore->getType() != typeid(t) )
            {
                throw Bu::ExceptionBase("Invalid type conversion.");
            }
            return dynamic_cast<VariantType<t> *>(pCore)->getData();
        }
        
        template<class t>
        t &get() const
        {
            if( !pCore )
            {
                throw Bu::ExceptionBase("No data!");
            }
            if( pCore->getType() != typeid(t) )
            {
                throw Bu::ExceptionBase("Invalid type conversion.");
            }
            return dynamic_cast<VariantType<t> *>(pCore)->getData();
        }

        template<class t>
        t &cast() const
        {
            if( !pCore )
            {
                throw Bu::ExceptionBase("No data!");
            }

            t *p = dynamic_cast<t *>(pCore->rawData());
            if( p == NULL )
                throw Bu::ExceptionBase("Invalid type conversion.");

            return *p;
        }
        
        template<class t>
        void set( const t &val )
        {
            if( pCore && pCore->getType() != typeid(t) )
            {
                delete pCore;
                pCore = NULL;
            }
            pCore = new VariantType<t>();
            (*dynamic_cast<VariantType<t> *>(pCore)) = val;
        }

        template<class t>
        bool isType() const
        {
            return pCore->getType() == typeid(t);
        }

        template<class t>
        operator t()
        {
            if( !pCore )
            {
                throw Bu::ExceptionBase("No data!");
            }
            if( pCore->getType() != typeid(t) )
            {
                throw Bu::ExceptionBase("Invalid type conversion.");
            }
            return dynamic_cast<VariantType<t> *>(pCore)->getData();
        }
        
        template<class t>
        operator t() const
        {
            if( !pCore )
            {
                throw Bu::ExceptionBase("No data!");
            }
            if( pCore->getType() != typeid(t) )
            {
                throw Bu::ExceptionBase("Invalid type conversion.");
            }
            return dynamic_cast<VariantType<t> *>(pCore)->getData();
        }

    private:
        VariantTypeRoot *pCore;
    };
/*
    template<class t>
    Bu::Formatter &operator<<( Bu::Formatter &f, const VariantType<t> &vt )
    {
        return f << vt.getData;
    }*/

    Bu::Formatter &operator<<( Bu::Formatter &f, const Variant &v );
};

#endif