Re: Calling the same function over and over again from C

[Rici Lake <lua@...>]

Try just leaving the function on the stack, and use lua_pushvalue() to 
make a copy of it.

If this is inconvenient, perhaps because the per-frame call happens in 
a callback, you can create the callback with the function as an 
upvalue.


On 23-Jul-05, at 6:30 AM, Framework Studios: Hugo wrote:

> Hi all!
>  
> I was just wondering if there is a way to speed-up calling the same 
> function over and over again from C++ to LUA.
>  
> My point is, let's say we want to call the function "PerFrame()" (just 
> for sake of argument), it would be something like:
>  
>     lua_pushstring(VM, "PerFrame");
>     lua_gettable(VM, LUA_GLOBALSINDEX);
>     lua_call(VM, 0, 0);
>  
> The first two lines are to seek a pointer to the actual function on 
> the stack. It seems rather slow to have to convert the string 
> to function every call. Is there a way to simply get whatever is on 
> the stack (eg. a function) and push it onto the stack later on?
>  
> I'm thinking something like this:
>  
> Only one time we do:
>  
>     lua_pushstring(VM, "PerFrame");
>     lua_gettable(VM, LUA_GLOBALSINDEX);
>  
> followed by something like:
>  
>     PerFrameFunction = lua_getfromstack(VM, 1);    // so I made up 
> "lua_getfromstack" here...
>  
> ...and per-frame we do something like:
>  
>     lua_pushtostack(VM, PerFrameFunction);
>     lua_call(VM, 0, 0);
>  
> It would be nice to be able to do the same for a function in a table 
> whilst reserving 'self'.
>  
> Did I miss how to do this or isn't it possible (yet? :) with LUA?
>  
>         Thanks,
>                     Hugo
>