From: Nicolas Pitre <nico@cam.org>
Date: Sun, 22 Apr 2007 13:27:13 GMT
Subject: Re: Why SHA are 40 bytes? (aka looking for flames)
Message-ID: <alpine.LFD.0.98.0704220925420.28339@xanadu.home>
In-Reply-To: <e5bfff550704211006t59cb49h179685d694a1d75a@mail.gmail.com>

On Sat, 21 Apr 2007, Marco Costalba wrote:

> On 4/21/07, Jon Smirl <jonsmirl@gmail.com> wrote:
> > On 4/21/07, Marco Costalba <mcostalba@gmail.com> wrote:
> > > Well, why to store always the full length SHA?
> > 
> > When Shawn gets done with full compression the SHAs would get stored
> > in the packfile once  and then be replaced with a token generated from
> > the compression algorithm. Compression tokens are designed to use the
> > minimal number of bits depending on frequency of occurrence.
> > 
> 
> Currently in Lunux tree there are about 445.424 objects (git
> count-objects -v), if each object has his 40 bytes name it is about
> 20MB to store sha *once*, probably with no real disambiguate need to
> be that much.

Object names aren't 40 bytes.  They are 20 bytes.

It  is their hex representation that takes 40 bytes.


Nicolas