Function requiref 

pub fn requiref(
    state: &mut LuaState,
    modname: &[u8],
    openf: fn(&mut LuaState) -> Result<usize, LuaError>,
    glb: bool,
) -> Result<(), LuaError>

Simplified require: open module modname via openf, register it in package.loaded, and (if glb) in the global table. Leaves the module on top of the stack.

C: LUALIB_API void luaL_requiref(lua_State *L, const char *modname, lua_CFunction openf, int glb)