audio_callback:PaStreamCallback   xtlang

(bind-func audio_callback:PaStreamCallback
  (let ((time 0)
        (nchan 2) ;; assume stereo
        (idx 0))
    (lambda (input output frameCount timeInfo statusFlags userData)
      (doloop (i frameCount)
        (doloop (j nchan)
          (set! idx (+ (* i nchan) j))
          ;; fill the output buffer with repeated values from our dsp
          ;; closure (no input in this version, but that's easy to do)
          (pset! (convert output float*)
                 idx
                 (dsp 0.0 time j null)))
        (set! time (+ time 1)))
      ;; to ensure the callback continues to be called
      paContinue)))