draft of audio HAL API

audio_hal.rs

pub struct DeviceInfo {
  id   : i32, 
  name : [u8; 64],
  num_input_channels  : usize, 
  num_output_channels : usize, 
}

pub trait Stream {
  fn start(self, sample_rate : usize, buffer_size : usize) -> Self; 
  fn stop(self) -> Self;
}
struct StreamParameters {
  pub num_ins : usize, 
  pub num_outs : usize, 
  pub sample_rate : usize, 
  pub buffer_size : usize, 
}
pub trait Device { 
  type SampleRateIter : Iterator<usize>; 
  type BufferSizeIter : Iterator<usize>;
  type DeviceInfoIter : Iterator<DeviceInfo>;
  type StreamHandle   : Stream; 
  
  fn devices() -> Self::DeviceInfoIter;
  fn sample_rates(d : &DeviceInfo) -> Self::SampleRateIter;
  fn buffer_sizes(d : &DeviceInfo) -> Self::DeviceInfoIter; 
  
  fn default_input() -> &DeviceInfo;
  fn default_output() ->&DeviceInfo; 
  
  fn open_input_stream (
    params : StreamParameters,
    input : Option<DeviceInfo>, 
    output : Option<DeviceInfo>, 
    callback : CbkFn) -> (Self::StreamHandle, StreamParameters);
}