while ridx != widx:
    # note: it may be faster to copy a batch of messages from shared memory
    # instead of directly accessing individual messages and their fields.
    msg = msgbuf[ ridx ]
    # sanity-check that message id increments monotonically
    lastid = ( lastid + 1 ) & 0xffffffff
    assert msg.id == lastid
    # get 32-bit timestamp (in cycles) from message and unwrap it:
    timestamp_cycles += ( msg.timestamp - timestamp_cycles ) & 0xffffffff
    # convert to timestamp in seconds:
    timestamp = timestamp_cycles / 200e6
    position = msg.position
    force = msg.force
    # consume message and update read pointer
    del msg  # direct access to message forbidden beyond this point
    ridx += 1
    if ridx == NUM_MSGS:
        ridx = 0
    shmem.ridx = ridx
# update user interface
print(f'\ridx=0x{ridx:04x} id=0x{lastid:08x} time={timestamp:08f} position={position:08d} force={force:08d}', end='', flush=True )