Re: [PATCH JGIT] Computation of average could overflow

From: Shawn O. Pearce <spearce@spearce.org>
Date: Apr 27, 2009, 23:17 UTC
Message-ID: <20090427231757.GM23604@spearce.org>
In-Reply-To: <366BBB1215D0AB4B8A153AF047A2878002FCE7E7@dewdfe18.wdf.sap.corp>

"Sohn, Matthias" <matthias.sohn@sap.com> wrote:

Show 7 quoted lines

> The code computes the average of two integers using either division or
> signed right shift, and then uses the result as the
> index of an array. If the values being averaged are very large, this can
> overflow (resulting in the computation of a negative
> average). Assuming that the result is intended to be nonnegative, you
> can use an unsigned right shift instead. In other
> words, rather that using (low+high)/2, use (low+high) >>> 1

Thanks, applied.  But your patch was line wrapped.  I had to unwrap
it by hand.  Please try to configure your MUA not to line wrap
patches when it sends them.  :-|

>  .../src/org/spearce/jgit/dircache/DirCache.java    |    2 +-
>  .../src/org/spearce/jgit/lib/Tree.java             |    2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)

-- 
Shawn.