TYPEMAP
SVGLibRSVG *  T_OBJECT

OUTPUT
T_OBJECT
        sv_setref_pv($arg, CLASS, (void*)$var);

INPUT
T_OBJECT
        if (sv_isobject($arg) && SvTYPE(SvRV($arg)) == SVt_PVMG)
        {
          IV tmp = SvIV((SV*)SvRV($arg));
          $var = INT2PTR($type, tmp);
        }
        else
          Perl_croak(aTHX_ \"${Package}::$func_name(): $var is not a blessed SV reference\");