[ovs-dev] [PATCH] lib/classifier: Fix array splicing.

[Ben Pfaff]

On Sun, May 11, 2014 at 11:55:01PM -0700, Jarno Rajahalme wrote:
> Array splicing was broken when multiple elements were being moved,
> resulting in the priority order being mixed.  This came up when the
> highest priority rule from a subtable was removed and the subtable
> needed to be moved down the priority list by more than one position.
> 
> Signed-off-by: Jarno Rajahalme <jrajahalme at nicira.com>

Can you explain what this function does?  I feel like it should be
obvious (I mean, clearly it's reordering the array), but in fact I'm
having trouble puzzling it out.

> diff --git a/lib/classifier.c b/lib/classifier.c
> index a9046cd..aef57bb 100644
> --- a/lib/classifier.c
> +++ b/lib/classifier.c
> @@ -224,12 +224,14 @@ cls_subtable_cache_splice(struct cls_subtable_entry *to,
>          to = start; start = end; end = temp;
>      }
>      if (to < start) {
> +        /* Move elements [start, end) to (to) one by one. */
>          while (start != end) {
>              struct cls_subtable_entry temp = *start;
>  
> +            /* Shift array by one, making space for the element at 'temp'. */
>              memmove(to + 1, to, (start - to) * sizeof *to);
>              *to = temp;
> -            start++;
> +            start++; to++;
>          }
>      } /* Else nothing to be done. */
>  }
> -- 
> 1.7.10.4
> 
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