Re: [Qemu-devel] [RFC][PATCH] signrom: Speed up checksum calculation

[Paolo Bonzini]

On 01/23/2012 07:38 PM, Jan Kiszka wrote:
>   nums=`od -A n -t u1 -v -N $size "$1"`
> -for i in ${nums}; do
> -    # add each byte's value to sum
> -    sum=`expr \( $sum + $i \) % 256`
> -done
> -
> -sum=$(( (256 - $sum) % 256 ))

We have a bashism here, so why not do

  sum=$(( ($sum + $i) % 256 ))

and do the same with a one-line patch (two line if you change the header 
to #!/bin/bash)?  It should be just as fast as awk.

Paolo