Function speex_decoder_ctl 

pub unsafe extern "C" fn speex_decoder_ctl(
    state: *mut c_void,
    request: c_int,
    ptr: *mut c_void,
) -> c_int

Used like the ioctl function to control the encoder parameters

@param state Decoder state @param request ioctl-type request (one of the SPEEX_* macros) @param ptr Data exchanged to-from function @return 0 if no error, -1 if request in unknown, -2 for invalid parameter