Re: [PATCH] Add a birdview-on-the-source-code section to the user manual

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi,

On Wed, 9 May 2007, Daniel Barkalow wrote:

> On Wed, 9 May 2007, Johannes Schindelin wrote:
> 
> > > To be honest, I wouldn't even be *thinking* about the endianity of SHA-1
> > > octet representation (you don't usually really deal with the hash as
> > > with a number, so expecting to have it in native endianity is not very
> > > natural; you just deal with it as with a data blob) and the
> > > "(big-endian)" would only confuse me and get me thinking about "huh, do
> > > they swap the bytes, or wait, they don't, ...?!".
> > > 
> > > But that's maybe just me.
> > 
> > But then, maybe it is just me? I got it completely wrong the first time, 
> > fully expecting the calculations to be carried out in host endianness for 
> > performance reasons.
> 
> I think the Mozilla implementation carries out calculations in host 
> endianness, and transfers data from the input to the internal state and 
> >from the internal state to the final hash with shifts and masks.
> 
> Which calculations are you seeing that involve byte order?

None. I only suspected them to be carried out in byte order. From what I 
know, there are some shifts involved, which might or might not be helped 
by 32-bit arithmetic.

I did not really look into it.

>From my prior debugging experiences on Intel, though, I automatically 
looked for the least significant bytes at the beginning of those "sha1" 
variables, and came up empty.

Ciao,
Dscho