Subject: Re: A look at some alternative PACK file encodings

From: A Large Angry SCM <[email-masked]>
Date: Thu, 07 Sep 2006 10:22:54 -0700

Jon Smirl wrote:
> On 7 Sep 2006 05:07:56 -0400, [email-masked] <[email-masked]> wrote:
>> > Support for 'thin' packs would pretty much require mixing IDs and
>> > (relative) offsets in the same pack file.
>>
>> An alternative would be to create a small "placeholder" object that
>> just gives an ID, then refer to it by offset.
>>
>> That would avoid the need for an id/offset bit with every offset,
>> and possibly save more space if the same object was referenced
>> multiple times.
>>
>> And it just seems simpler.
> 
> There are 2 million objects in the Mozilla pack. This table would take:
> 2M *  (20b (sha)  + 10b(object index/overhead) = 60MB
> This 60MB is pretty much incompressible and increases download time.
> 
> Much better if storage of the sha1s can be totally eliminated and
> replaced by something smaller. Alternatively this map could be
> stripped for transmission and rebuilt locally.
> 

You've lost me. What are you attempting to do again?