Re: metatable and c++ assistance/thoughts

[Philippe Lhoste <PhiLho@...>]

Kevin Baca wrote:
> You said you were using a *light* userdata.

No, he states "A relatively lightweight way to do this", ie. he uses 
heavy userdata (or using his own words "full user data") but lighten it 
(with helium balloon?), or rather its use.

> The boxpointer macros create a *heavy* userdata.
>
> You can't receive a gc event on a table and the only way to receive a gc
> event on a userdata is if it's a heavy userdata.
>
> -Kevin
>
> > -----Original Message-----
> > From: lua-bounces@bazar2.conectiva.com.br 
> > [mailto:lua-bounces@bazar2.conectiva.com.br] On Behalf Of 
> > Robert Sadedin
> > Sent: Monday, October 18, 2004 11:30 PM
> > To: lua@bazar2.conectiva.com.br
> > Subject: RE: metatable and c++ assistance/thoughts
> >
> > Thanks Kevin.  That's what I'm doing, except I'm not using 
> > the macros, 
> > rather calling the methods directly.
> >
> > Am I missing something, or wouldn't it be nice to be able to 
> > garbage collect 
> > a table from c++ as well as userdata?
> >
> > >The only way to receive a __gc event on a user data is to 
> > make it a full
> > >user data with a metatable that contains a __gc metamethod.
> > >
> > >A relatively lightweight way to do this is to use Lua's 
> > "boxpointer" set
> > >of macros.
> > >
> > ><code>
> > >     lua_boxpointer( L, my_pointer);
> > >     lua_newtable( L );
> > >     lua_pushstring( L, "__gc" );
> > >     lua_pushcfunction( L, myGCFunction );
> > >     lua_settable( L, -3 );
> > >     lua_setmetatable( L, -2 );
> > ></code>
> > >
> > ><code>
> > >int myGCFunction( lua_State* L )
> > >{
> > >     MyData* my_pointer = ( MyData* ) lua_unboxpointer( L, 1 )
> > >
> > >     delete my_pointer;
> > >}
> > ></code>
> > >
> > >-Kevin

--
Philippe Lhoste
--  (near) Paris -- France
--  Professional programmer and amateur artist
--  http://Phi.Lho.free.fr
--  --  --  --  --  --  --  --  --  --  --  --