Lua: "Hide" functions

Question

I want to call c functions from lua to change variables defined in C, but I don't want the lua "user" to realize they are functions.

For example, consider an integer and an array created in c:

int c_level = 0;
int c_map[4] = {0,0,0,0}; 

Now the program creates a Lua state and runs this:

set_level(2) --c_level = 2
set_tile(1,23) --c_map[0] = 23

I want them to look like this in the lua script:

L_level = 2
L_map[1] = 23

So, L_level and L_map would be functions defined in C.

L_level 's argument would be "2".

L_map 's arguments are "1" and "23".

Is that possible?.

I can get the lua variables using getglobal, but I wanted to know if I can create some lua functions that look like the ones I showed.

Thanks.

Answer 1

When you set

L_level = 2

you really index the global table _G with the key L_level and set it to 2 . What you can do is to set a meta -table for _G and set the function __newindex to a function, that checks if the key is L_level or L_map and handles these cases differently.

This function can be directly a C-function or a Lua-function, that checks the key and calls a c-function if the name matches one of your tracked names, for example like

setmetatable(_G, {
    __newindex = function (_, k, v)
        if (k == "L_level") then do_setlevel(v)
        elseif (k == "L_map") then do_setmap(v)
        else rawset(_G, k, v)
        endif
    end
})

do_setlevel and do_setmap are in this case global c functions. You can of course do all this completely in C, too.