Allow waiting for playback to finish #41
Description
I wrote a simple playback program that streams audio from a file to cpal, and then exits. When the number of samples is small enough (this happened to me for 44100 samples, one second of mono audio), all of the samples can be passed to append_data in one step. So the application dumped all of its data into the buffer, called voice.play(), and exited before the audio even had a chance to begin to play.
Therefore, it would be useful to have a method to poll whether playback is complete, or a method that blocks until this is the case.