Function ad_read 

pub unsafe extern "C" fn ad_read(
    dev: *const ad_rec_t,
    buf: *mut i16,
    max: u32,
) -> i32

Read next block of audio samples while recording; read upto max samples into buf.

Safety

Return # samples actually read (could be 0 since non-blocking); AD_EOF if not recording and no more samples remaining to be read from most recent recording.