From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Shawn O. Pearce" <spearce@spearce.org>
Subject: Re: Why SHA are 40 bytes? (aka looking for flames)
Date: Mon, 23 Apr 2007 22:30:35 -0400
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Cc: Nicolas Pitre <nico@cam.org>, Marco Costalba <mcostalba@gmail.com>,
	Jon Smirl <jonsmirl@gmail.com>,
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To: "H. Peter Anvin" <hpa@zytor.com>
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"H. Peter Anvin" <hpa@zytor.com> wrote:
> Nicolas Pitre wrote:
> >
> >Object names aren't 40 bytes.  They are 20 bytes.
> >It  is their hex representation that takes 40 bytes.
> >
> 
> Sure, but that's the way they're stored in *most* git objects, in 
> particular in commit objects.

But OBJ_TREE occurs more often, and its 20 bytes binary for a SHA-1
in those.  They are only ASCII hex in OBJ_COMMIT and OBJ_TAG.

If Nico and I ever get pack v4 done, all SHA-1s drop to 24 bytes
worst case, or 20 + (4 * n_references) best case.  Typically we
found that n_references was large enough, frequently enough, that
we shaved 5% or so off linux-2.6.git.  And I don't think that's
including the 20 * n_objects saved out of the .idx files...

-- 
Shawn.