Re: Why SHA are 40 bytes? (aka looking for flames)

["Jon Smirl" <jonsmirl@gmail.com>]

On 4/21/07, Marco Costalba <mcostalba@gmail.com> wrote:
> Well, why to store always the full length SHA?

When Shawn gets done with full compression the SHAs would get stored
in the packfile once  and then be replaced with a token generated from
the compression algorithm. Compression tokens are designed to use the
minimal number of bits depending on frequency of occurrence.

This doesn't happen with the current compression code since it doesn't
have a global dictionary.

There are many other things that would benefit from a global
dictionary. For example when working on the Mozilla repository the
Mozilla license has gone through four major revisions. Each of these
licenses is in the repository thousands of times. Making a copy of
each license to a global dictionary and then replacing them with a
token would yield megabytes of savings in the pack.

I would think that it is better to wait for a general compression
solution rather than do a specific one for SHAs.

-- 
Jon Smirl
jonsmirl@gmail.com