From mboxrd@z Thu Jan  1 00:00:00 1970
From: Nicolas Pitre <nico@cam.org>
Subject: Re: heads-up: git-index-pack in "next" is broken
Date: Wed, 18 Oct 2006 09:13:04 -0400 (EDT)
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Cc: Junio C Hamano <junkio@cox.net>, git@vger.kernel.org,
	Linus Torvalds <torvalds@osdl.org>
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On Wed, 18 Oct 2006, Johannes Schindelin wrote:

> Hi,
> 
> On Tue, 17 Oct 2006, Junio C Hamano wrote:
> 
> > +/*
> > + * Even if sizeof(union delta_base) == 24 on 64-bit archs, we really want
> > + * to memcmp() only the first 20 bytes.
> > + */
> > +#define UNION_BASE_SZ	20
> 
> Excuse me for joining the game, but why don't you just use the 
> recently introduced hashcmp() for that purpose? AFAIU you do exactly that, 
> you compare hashes.

Yes, and that is what I did originally.

But that could lead to false assumptions (and this thread already proved 
this code has its share of false assumption leads already).  The thing 
is that the memory chunk that is being compared is not always the same 
kind of hash as usually used with hashcmp().  Throughout the code 
hashcmp() is always used with a 20-byte sha1 digest.  In this case it 
can be either a 20-byte sha1 digest, or a long offset value.  And by 
using hashcmp() I would be afraid someone else could assume the hash is 
always a sha1 digest which it is not.


Nicolas