Re: Understanding pack format

From: Duy Nguyen <pclouds@gmail.com>
Date: Nov 2, 2018, 16:00 UTC
Message-ID: <CACsJy8DFUeEddSa2z4VTSqhaUBJ4+SUf8xvjh6iWY2Phhh96iQ@mail.gmail.com>
In-Reply-To: <xmqqlg6covi6.fsf@gitster-ct.c.googlers.com>

On Fri, Nov 2, 2018 at 7:19 AM Junio C Hamano <gitster@pobox.com> wrote:

Show 10 quoted lines

>
> Farhan Khan <khanzf@gmail.com> writes:
>
> > ...Where is this in the git code? That might
> > serve as a good guide.
>
> There are two major codepaths.  One is used at runtime, giving us
> random access into the packfile with the help with .idx file.  The
> other is used when receiving a new packstream to create an .idx
> file.

The third path is copying/reusing objects in builtin/pack-objects.c::write_reuse_object(). Since it's mostly encoding the header of new objects in pack, it could also be a good starting point. Then you can move to write_no_reuse_object() and get how the data is encoded, deltified or not (yeah not parsed, but I think it's more or less the same thing conceptually).

-- 
Duy