Hi again, I'm back with this callback problem quick summary: a jack client have to set a callback so the jack server can call it when the client is supposed to do something. Here, the callback call is supposed to trigger some scheme code execution.
Today I tried a different approach: writing the callback in C, and then calling
back to scheme from this function.
> // C part
> extern int process (jack_nframes_t);
>
> int callback(jack_nframes_t nframes, void* arg)
> {
> int i;
> printf("callback\n");
> for (i = 0 ; i < nframes ; i++) {
> process(now);
> now++;
> }
> return 0;
> }
> ;; Scheme part
> (define-external (process (unsigned-long now)) int
> (display now)(newline)
> now)
A manual call to callback shows the expected behaviour : printing callback, and
then the successive values of now.
> (define callback
> (foreign-safe-lambda int "callback" jack_nframes (c-pointer void) ))
> (callback 5 #f)
Now, if I let the jack server do the job ...
> ((foreign-lambda*
> void ()
> "jack_set_process_callback(client, callback, NULL);"))
>
> (jack_activate client)
this is what I get :
> Error: call of non-procedure: #<unspecified>
>
> Call history:
>
> client.scm:58: display
> client.scm:58: newline
> client.scm:71: jack_activate
> ##sys#gc
> g2930
> client.scm:72: jack_deactivate
> client.scm:74: jack_client_close
> ##sys#implicit-exit-handler <--
And there I am, completely lost. Any clue ?
thanks for reading
tom
#include <jack/jack.h>
#include "chicken.h"
extern int process (jack_nframes_t);
extern unsigned long int now;
int callback(jack_nframes_t nframes, void* arg)
{
int i;
printf("callback\n");
for (i = 0 ; i < nframes ; i++) {
process(now);
now++;
}
return 0;
}
client.scm
Description: Binary data
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