port-has-port-position? port-has-set-port-position!?
close-port call-with-port
open-bytevector-input-port make-custom-binary-input-port get-u8
port-has-port-position? port-has-set-port-position!?
close-port call-with-port
open-bytevector-input-port make-custom-binary-input-port get-u8