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

[Thomas Jericke <tjericke@...>]

On 05/23/2013 01:28 PM, Satz Klauer wrote:
> Hi,
>
> I have a pointer to some user data available during initialisation,
> means before the LUA-script is started. This pointer has to be
> available during execution of the script, since it is a multithreaded,
> explicitely linked shared library environment I can't use just a
> global variable that stores these data.
>
> So when a C-function is called out of a running LUA-script I need to
> access these user data. Since the C-function is always defined as
>
> 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!

Is this pointer once per lua_State? If this is the case you can use a 
dirty trick that I do and store it in the *ud of the Lua state.

main() {
    sometype* mypointer;
    lua_State L = lua_newstate(someallocfunction, mypointer);

    lua_pushcfunction(L, my_lua_called_c_fct);
    lua_setglobal(L, "my_c_function");

    lua_loadbuffer(L, "my_c_function()", 15, "");
    lua_call(L, 0, 0);
}

int my_lua_called_c_fct(lua_State *L) {
   sometype* mypointer;
   lua_getallocf(L, (void**)&mypointer);
   DoSomeStuff(mypointer);
}

It's a trick but its as I see it the fastest and easiest way to store a 
pointer in L.

--
Thomas