sndio sio_onmove not calling back. - audio

Question

I'm trying to write a fullduplex test that copies audio in to audio out. sio_onmove does not get called. I have no idea why. Here's my code so far:
#include <stdio.h>
#include <stdlib.h>
#include <sndio.h>
unsigned char buf[0xffff];
struct sio_hdl *hdl;
void cb(void *arg, int delta) {
int l;
printf("call %d\n", delta);
for(;;) {
l = sio_read(hdl, buf, delta);
if(l==0) break;
sio_write(hdl, buf, l);
}
}
int main(void) {
int m, i;
struct sio_par par;
struct sio_cap cap;
hdl = sio_open("rsnd/0", SIO_PLAY | SIO_REC , 1);
sio_getcap(hdl, &cap);
sio_initpar( &par);
par.bits = cap.enc[0].bits;
par.bps = cap.enc[0].bps;
par.sig = cap.enc[0].sig;
par.le = cap.enc[0].le;
par.msb = cap.enc[0].msb;
par.rchan=cap.rchan[0];
par.pchan=cap.pchan[0];
par.rate =cap.rate[0];
par.appbufsz = 1024;
sio_setpar(hdl, &par);
sio_onmove(hdl, cb, NULL);
sio_start(hdl);
for(;;)
sleep(1);
}
I'm initializing rsnd/0 for recording and play back. The parameters I'm initializing from a getcap call. I'm then setting cb as the callback for onmove. I then start audio. From there I loop forever doing nothing

Answer 1

The sio_onmove() call-back is called either from sio_revents() if non-blocking i/o is used or from blocking sio_read() or sio_write().
As above program calls sleep(1) instead, the call-back is never called.
AFAIU, to do the full-duplex test, you could use blocking i/o (set to 0 last argument of the sio_open() function) and do the following steps:
call sio_initpar() to initialize a sio_par structure, as you do
set your preferred parameters in the sio_par structure
call sio_setpar() to submit them to the device. devices exposed through the server (ex. "snd/0") will accept any parameters, while raw devices (ex. "rsnd/0") pick something close to whatever the hardware supports.
call sio_getpar() to get the parameters the device accepted, this is needed to get the device buffer size
possibly check if they are usable by your program
call sio_start()
prime the play buffer by writing par.bufsz samples with sio_write(). This corresponds to: par.bufsz * par.pchan * par.bps bytes.
At this stage, device starts and you could do the main-loop as with the following pseudo-code:
unsigned char *data;
size_t n, todo, blksz;
blksz = par.round * par.rchan * par.bps;
for (;;) {
/* read one block */
data = buf;
todo = blksz;
while (todo > 0) {
n = sio_read(hdl, data, todo);
if (n == 0)
errx(1, "failed");
todo -= n;
data += n;
}
/* write one block */
n = sio_write(hdl, buf, blksz);
if (n != blksz)
errx(1, "failed");
}
The sio_onmove() call-back is not needed for pure audio programs. It's only useful to synchronize non-audio events (ex video, midi messages) to the audio stream.