Re: Hand over global userdata to LUA-called C-function

[Owen Shepherd <owen.shepherd@...>]

Satz Klauer wrote:
> int my_lua_called_c_fct(lua_State *L)
>
> there seems to be "L" where I could get these user data from. But how
> can I put the data to "L" during initialisation and how can I retrieve
> them within that function?
>
> These are some configuration-data that are required to execute
> my_lua_called_c_fct()...
>
> Thanks!


Normally you would stash the userdata in the registry table. Two options exist for this; the first is to use a string key and retrieve it with code along the lines of:
   lua_pushliteral(L, "mykey");
   lua_gettable(L, LUA_REGISTRYINDEX);
   MyType* data = "" lua_touserdata(L, -1);

Another alternative, slightly faster (because you don't have to intern the string each time) is to use a light user data pointed at a glo
bal constant for the key:
   static const char* mykey = "This string is completely ignored";
   ...
   lua_pushlightuserdata(L, mykey);
   lua_gettable(L, LUA_REGISTRYINDEX);
   MyType* data = "" lua_touserdata(L, -1);


The registry table is a table that is global to the interpreter (and not normally visible to script)