From: Nicolas Pitre <nico@cam.org>
Date: Thu, 19 Oct 2006 14:17:21 GMT
Subject: Re: [PATCH] reduce delta head inflated size
Message-ID: <Pine.LNX.4.64.0610191012090.1971@xanadu.home>
In-Reply-To: <118833cc0610190649o484afdc8lb871d4b3c5361166@mail.gmail.com>

On Thu, 19 Oct 2006, Morten Welinder wrote:

> On 10/18/06, Nicolas Pitre <nico@cam.org> wrote:
> > Supposing that both the base and result sizes were both full size 64-bit
> > values, their encoding would occupy only 9.2 bytes each.  Therefore
> > inflating 64 bytes is way overkill.  Limit it to 20 bytes instead which
> > should be plenty enough for a couple years to come.
> 
> 2^63 ~ 9.2e18
> 
> Thus one signed 64-bit number can take up 1 sign + 19 digits + 1 nul.
> That's 21 bytes.

No.  In this case the value is kept binary, with bits spread over 
consecutive bytes but with the MSB indicating continuation on the next 
byte.

This means 64 bits / 7 bits per byte = 9.1 bytes, hence 10.  Then there 
are 2 of those values that makes 20 bytes.


Nicolas