Re: overloading registrations
[
Date Prev][
Date Next][
Thread Prev][
Thread Next]
[
Date Index]
[
Thread Index]
- Subject: Re: overloading registrations
- From: Diego Nehab <diego@...>
- Date: 2001年4月25日 19:03:04 -0300 (EST)
Hi,
> What I would like to do is to overload a registration of a c function.
>
> What I would like to write in c is something like:
>
> int myhandler( lua_State* L )
> {
> int n_returns = 0;
> if(strcmp(lua_tostring(L,0),"foo")==0)
> {
> ... do stuff for function foo
> }
> else if(strcmp(lua_tostring(L,0),"fun")==0)
> {
> ... do stuff for function fun
> }
> return n_returns; /* would be set by something above
> }
>
> So I envision lua_tostring(L,0) retrieving something analogous to what
> argv[0] is in the parameters to a program - the program name. That way
> I could write the following registrations:
>
> lua_register(L,"foo",myhandler);
> lua_register(L,"fun",myhandler);
You can do that with C closures as follows (untested code):
int myhandler( lua_State* L )
{
int n_returns = 0;
/* get 'personality' from closure value */
const char *name = lua_tostring(L, -1);
if(strcmp(name,"foo")==0) {
... do stuff for function foo
} else if(strcmp(name,"fun")==0) {
... do stuff for function fun
}
return n_returns; /* would be set by something above
}
/* define global "foo" */
lua_pushstring(L, "foo");
lua_pushcclosure(L, myhandler, 1);
lua_setglobal(L, "foo")
/* define global "fun" */
lua_pushstring(L, "fun");
lua_pushcclosure(L, myhandler, 1);
lua_setglobal(L, "fun")
Whenever a C closure is called, it receives the values enclosed as it's
last parameters. Thus, the two functions defined above will receive
different closure values as their last parameter, enabling the C
implementation to distinguish between the "foo" and "fun" personalities.
Regards,
Diego.