sound.rs

extern crate cpal; 

use cpal::{EventLoop, StreamData, UnknownTypeOutputBuffer};

fn main() {

  let event_loop = EventLoop::new();

  let device = cpal::default_output_device().expect("no output device available");
  let format = device.default_output_format().unwrap();
  let stream_id = event_loop.build_output_stream(&device, &format).unwrap();
  event_loop.play_stream(stream_id);

  let mut samples_written: u64 = 0;

  event_loop.run(move |_stream_id, stream_data| {
    let mut buffer = if let StreamData::Output{buffer} = stream_data {
      if let UnknownTypeOutputBuffer::F32(buffer) = buffer {
        buffer
      } else {
        panic!("got non f32 buffer");
      }
    } else {
      panic!("got StreamData::Input, which we didn't request.");
    };

    for elem in buffer.iter_mut() {
      let time = (samples_written / format.channels as u64) as f32 / format.sample_rate.0 as f32;

      let t = time / (1.0/220.0) % 1.0;

      if t < 0.5 {
        *elem = 0.4;
      } else {
        *elem = -0.4; 
      }      
      
      samples_written+=1;
    }
  });
  
}