Re: Understanding Binary Deltas within Packfile

From: Duy Nguyen <pclouds@gmail.com>
Date: Mar 20, 2018, 19:12 UTC
Message-ID: <CACsJy8ChV5sXV7N0+N0y9ehO56UCJ8fuqjFbHbbnez35P5af4g@mail.gmail.com>
In-Reply-To: <751c0493-435c-4a98-4d1c-e3d6677c62d8@arlut.utexas.edu>

On Tue, Mar 20, 2018 at 7:34 PM, Luke Robison <robison@arlut.utexas.edu> wrote:

Show 20 quoted lines

> On 3/20/2018 11:03 AM, Duy Nguyen wrote:
>>
>> On Tue, Mar 20, 2018 at 4:43 PM, Luke Robison <robison@arlut.utexas.edu>
>> wrote:
>>>
>>> Is there any documentation of the contents of the binary delta datain a
>>> packfile, and how to interpret them?  I found
>>>
>>> https://github.com/git/git/blob/master/Documentation/technical/pack-format.txt
>>> documenting the packfile itself, but the "compressed delta data" seems
>>> largely undocumented.  The source code of
>>> https://github.com/git/git/blob/master/diff-delta.c is pretty dense.
>>
>> The output is consumed by patch_delta()  in patch-delta.c if I'm not
>> mistaken. This function is less than 100 lines, probably much easier
>> to see the delta format.
>
> Thank you, that was much easier to read, and I've got my prototype working
> now.  I also found this site to be quite helpful:
> http://stefan.saasen.me/articles/git-clone-in-haskell-from-the-bottom-up/#delta_encoding

By the way, I forgot to add, if you want to improve pack-format.txt (since you study it anyway), patches are always welcome.

-- 
Duy