(cond-expand
  (chicken-6
    (import (scheme base)
            (chicken io)
            (chicken bytevector)
            ))
  (else
    (import (chicken blob)
            (srfi-4))
    (define read-bytevector read-u8vector)
    (define write-bytevector write-u8vector)
    (define bytevector-length blob-size)
    ))