From: A Large Angry SCM Date: Thu, 07 Sep 2006 02:33:06 GMT Subject: Re: A look at some alternative PACK file encodings Message-ID: <44FF84E2.5040201@gmail.com> In-Reply-To: <9e4733910609061759m2aae9e31ja146e309dc449628@mail.gmail.com> Jon Smirl wrote: > On 9/6/06, Nicolas Pitre wrote: >> On Wed, 6 Sep 2006, Jon Smirl wrote: >> >> > Shawn is doing some prototype work on true dictionary based >> > compression. I don't know how far along he is but it has potential for >> > taking 30% off the Mozilla pack. >> >> BTW I'm half-way done with support for deltas which base object is >> referenced with an offset in the pack instead of a hash. It is quite >> messy though since it touches pretty core code all over the place when >> it comes to fetching objects out of a pack. > > Would it help to change all of the references in the pack from sha1 to > encoded relative offsets? Then collect all of the object fetch code > into a single subroutine which would change it algorithm depending on > which type of pack it is operating on. Now the pack wouldn't mix > reference types, they would all be encoded relative or sha1. > Support for 'thin' packs would pretty much require mixing IDs and (relative) offsets in the same pack file.