[Python-Dev] Base-96

[Guido van Rossum]

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/)