Hi and pushing existing UserData from pointer

[Chris Camacho <c.camacho@...>]

Hi all!

First off nice language! nice and light, reasonably fast and yet small, 
without being crippled....

I'm wrapping a library and have a good portion done, I've used user 
data, so that I have newly created objects from the C library collected 
by lua's GC (nice!)

All is working well as I'm just creating new instances and returning 
them, basically very much like this 
http://lua-users.org/wiki/UserDataExample

I can set up from lua a callback by having a kind of callback proxy in C 
which actually receives the callback and then runs the appropriate lua 
function

The Lua call back function needs to receive some references to userdata 
objects that are already in existence and all I have for them is the C 
pointer to the structure I've wrapped.

At the moment I can see different return values from different lua 
callback functions but I cannot send them useful information!

heres what I have after trying many different things, (as a result its a 
mess!)
I can pass a number as a parameter and all works as it should



void* d; // temp will live in void* data with other stuff

int CollFunc(cpShape *a, cpShape *b, cpContact *contacts, int 
numContacts, cpFloat normal_coef, void *data) {

  lua_getglobal(d,data);  // routine name will be inside struct pointer 
to callback data
//   lua_pushlightuserdata(d, a);
  lua_pushvalue(d,(void*)a);
 luaL_getmetatable(d, "cpShape"); // luaL_pushUDfromPointer((void*)a)!
 lua_setmetatable(d, -2);
//   lua_pushlightuserdata(d, b);


  lua_pcall(d, 1, 1, 0);


  int r=lua_toboolean(d,1);
lua_pop(d,1);

  return r;

}


Is there any way to make a new userdata that is a reference to an
already allocated userdata from just a C pointer?

I did google but couldn't really find too much
(I will do a quick wiki page on this once I understand how to do it...)

Best
Chris

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