d88-jwa@byse.nada.kth.se (Jon W{tte) (03/25/91)
The previously suggested way of using arithmetic coding for
uuencode-style data encoding into printable characters seems
cool, but a simple "base 85" mapping from four bytes to five
chars (such as used by atob) and vice versa does the trick
with _very_ close to optimal performance. The problem is;
it requires longword modulo and/or division, which has to be
simulated on weaker processors (such as 68000 or (yukk !)
8086)
The mapping of four bytes to six characters (as used in many
popular formats like uuencode and binhex) clearly is a waste,
though. (Hmm... it's faster on those weak processors... But
an extra cycle compared to 20% higher transfer time is worth
it :-)
Happy hacking,
h+@nada.kth.se
Jon W{tte
--
"The IM-IV file manager chapter documents zillions of calls, all of which
seem to do almost the same thing and none of which seem to do what I want
them to do." -- Juri Munkki in comp.sys.mac.programmer