Stuff reclaimed from old BlobAPI
(bytevector-<encoding>-ref bytevector [ [ start ] end ] )
Returns a newly allocated Scheme string corresponding to the binary value encoded according to encoding beginning at offset n in bytevector and continuing for l bytes.
(bytevector-<encoding>-set! bytevector n v)
Converts v to a binary string encoded according to encoding and places it into bytevector beginning at offset n. Returns the number of bytes encoded.