[Python-Dev] Base-96 (original) (raw)

Guido van Rossum guido at python.org
Sat Aug 2 20:57:37 CEST 2008

On Sat, Aug 2, 2008 at 10:37 AM, Josiah Carlson <josiah.carlson at gmail.com> wrote:

On Sat, Aug 2, 2008 at 10:09 AM, "Martin v. Löwis" <martin at v.loewis.de> wrote:

Josiah Carlson wrote:

The standard high-bit-density encoding past base-64 is base-85 (http://en.wikipedia.org/wiki/Ascii85), which encodes 4 binary bytes as 5 ascii bytes, versus 3 binary bytes as 4 ascii bytes. It works, is an RFC somewhere,

RFC 1924, published on April 1, 1996, to shorten the representation of IPv6 addresses, so that you can write ssh '4)+k&C#VzJ4br>0wv%Yp' instead of having to write ssh 1080:0:0:0:8:800:200C:417A Most notably, section 7 (implementation issues) points out Many current processors do not find 128 bit integer arithmetic, as required for this technique, a trivial operation. This is not considered a serious drawback in the representation, but a flaw of the processor designs. For arbitrary-sized data, you'd have to give up 128-bit arithmetic, of course, and represent the input data to encode as a long integer. Regards, Martin P.S. Just in case it isn't clear: I would oppose any specific proposal to add this Ascii85 algorithm to the standard library. It would sound like we don't have any real problems to solve.

Same here.

Original intent (encoding IPV6 addresses) != current usefulness (a more efficient ascii encoding of binary data).

That was an April Fool's RFC.

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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