At Tue, 14 Jan 2003 11:47:58 -0500,
Paul Davis wrote:
>
> >> that said, i think it would be great if this found its way into libasound.
> >
> >is the below code ok?
> >
> >int snd_pcm_wait_many(snd_pcm_t **handles, int num_handles, int timeout)
> >{
> > struct pollfd *pfds;
> > int i, err;
> > pfds = (struct pollfd *)alloca(sizeof(*pfds) * num_handles);
> > if (! pfds)
> > reutrn -ENOMEM;
> > for (i = 0; i < num_handles; i++) {
> > err = snd_pcm_poll_descriptors(handles[i], &pfds[i], 1);
> > assert(err == 1);
> > }
> > err = poll(pfds, num_handles, timeout);
> > if (err < 0)
> > return -errno;
> > return err > 0 ? 1 : 0;
> >}
>
> this isn't even close. the function in question waits until each and
> every handle is ready. that means reentering poll over and over again
> until each handle is ready, making sure to only poll on the handles
> that are not yet ready (because otherwise poll returns immediately).
>
> the semantics are not "wait for any one many", its "wait for all or an
> error".
ah, now got the meaning. so, something like that...
// set up pfds...
...
for (;;) {
err = poll(pfds, num_handles, timeout);
if (err < 0)
return -errno;
else if (err == 0)
return 0;
i = 0;
while (i < num_handles) {
if (pfds[i].revents & POLLOUT) {
num_handles--;
memmove(pfds + i + 1, pfds + i,
sizeof(*pfds) * (num_handles - i));
} else
i++;
}
}
return 1;
Takashi
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