Re: A look at some alternative PACK file encodings

From: Jon Smirl <jonsmirl@gmail.com>
Date: 2006-09-07 22:57:02
On 7 Sep 2006 05:07:56 -0400, linux@horizon.com <linux@horizon.com> 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.

-- 
Jon Smirl
jonsmirl@gmail.com
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Received on Thu Sep 07 22:58:05 2006

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