Re: [PATCH] dracut-functions: fun. vercmp optimized; credits go to Victor Lowther

[Harald Hoyer <harald-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On 06/09/2010 05:29 PM, Amadeusz Żołnowski wrote:
> ---
>   dracut-functions |   23 ++++++++++++-----------
>   1 files changed, 12 insertions(+), 11 deletions(-)
>
> diff --git a/dracut-functions b/dracut-functions
> index fbac282..500e3ae 100755
> --- a/dracut-functions
> +++ b/dracut-functions
> @@ -27,19 +27,20 @@ strstr() { [[ $1 =~ $2 ]]; }
>   # Version comparision function.  Returns result similar to C strcmp,
>   # but instead of -1 is 2.  Function assumes version scheme like does
>   # Linux kernel.
> +# $1<  $2 ->  2
> +# $1 = $2 ->  0
> +# $1>  $2 ->  1
> +# To remember it easy, ask the question: Which argument is greater? ;-)
>   vercmp() {
> -    local n1 n2 i=1
> -
> -    while true
> -    do
> -        n1=$(echo $1 | cut -d'.' -f$i)
> -        n2=$(echo $2 | cut -d'.' -f$i)
> -
> -        [[ ! $n1&&  ! $n2 ]]&&  return 0
> -        [[ $n1 -lt $n2 ]]&&  return 2
> -        [[ $n1 -gt $n2 ]]&&  return 1
> -
> -        ((i++))
> +    local i n1=(${1//./ }) n2=(${2//./ })
> +
> +    for ((i=0; ; i++))
> +    do
> +        [[ ${n1[i]}&&  ! ${n2[i]} ]]&&  return 1
> +        [[ ! ${n1[i]}&&  ${n2[i]} ]]&&  return 2
> +        [[ ${n1[i]}&&  ${n2[i]} ]] || return 0
> +        ((${n1[i]}>  ${n2[i]}))&&  return 1
> +        ((${n1[i]}<  ${n2[i]}))&&  return 2
>       done
>   }
>

pushed