Fons Adriaensen wrote:
> I need some advice on the ALSA sequencer interface. In particular I'd
> like to know if the following code can be safely used inside a real-time
> audio thread, i.e. is it guaranteed not to block ?
>
> snd_seq_event_t *E;
>
> if (snd_seq_event_input_pending (midi_seqh, 1))
> {
> do
> {
> snd_seq_event_input (midi_seqh, &E);
> // handle event E
> }
> while (snd_seq_event_input_pending (midi_seqh, 0));
> }
Looks safe. In theory, some other thread could grab an event before
this loop can read it, but I guess you don't write such code. :-)
However, the canonical way to do this is to use nonblocking mode:
snd_seq_nonblock(midi_seqh, 1);
while ((err = snd_seq_event_input(midi_seqh, &e)) >= 0)
{
// ...
}
// err is -EAGAIN if no more input
HTH
Clemens
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