[PD] Modifying "dsp chain" live !!!

[Miller Puckette]

HI all,

I'm unclear why you'd want to do this... if it's to change parameters to
DSP objects, that's better done by storing them as state variables; example,
lop~ cutoff frequency change.

cheers
Miller

On Fri, Nov 16, 2001 at 01:42:16AM +0100, Yves Degoyon wrote:
> hi list, hi miller,
> 
> I've made a little patch to enable externs
> to modify the dsp chain while the dsp processing
> is running... this avoids to restart dsp processing
> when a parameter is changed, this is illustrated 
> by the "spigot~" extern attached.
> 
> Without this patch, I had to restart dsp processing
> and all other dsp objects got interrupted.
> That was really annoying !!!
> 
> What was made basically was adding the following code :
> 
> d_ugen.c :
> 
> ################################################
>     /* function to dynamically change dsp functions parameters
>        arguments are :
>        f : pointer to your dsp function
>        rank : rank of the argument to change
>        value : new value of this parameter
> 
>        QUITE DANGEROUS !!! no checking is possible 
>        because the number of arguments is not stored in dsp_chain 
>        Copyleft ydegoyon at free.fr */
> void dsp_mod(t_perfroutine f, int rank, int value )
> {
>     va_list ap;
>     t_int *pdsp_chain = dsp_chain;
>     t_int i;
> 
>     while ( pdsp_chain ){
>        if ( *pdsp_chain == (t_int)f ){
>           *(pdsp_chain+rank) = value;
>           post ( "dsp_mod : warning : modifying dsp chain, better know what you're doing!!!!" );
>           break;
>        }
>        pdsp_chain++;
>     }
> }
> ################################################
> 
> This function has to be exported in m_pd.h :
> 
> ################################################
> EXTERN void dsp_mod(t_perfroutine f, int rank, int value);
> ################################################
> 
> An example of use is available in spigot~.c attached.
> 
> This is really dangerous to use this, 
> because it enables an extern to transform
> dsp_chain into a mess,
> so use it with care !!!
> 
> Cheers,
> 
> Yves Degoyon.
> 
> PS : it seems to be patch day, so I don't deliver this as a patch
> for incremental reasons ( I've applied some patches myself ).