Function lumen_event_value 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn lumen_event_value(
    buf: *mut c_char,
    buf_len: usize,
    out_len: *mut usize,
) -> LumenStatus

Copy the current event’s value (input / change events) into buf. See lumen_event_type for the convention. Thread-safe.