Looks good, thanks.
Ethan
On Fri, Jul 20, 2012 at 4:25 PM, Ben Pfaff <b...@nicira.com> wrote:
> It's probably easier to understand
> x = zero_rightmost_1bit(x);
> than
> x &= x - 1;
>
> Signed-off-by: Ben Pfaff <b...@nicira.com>
> ---
> lib/util.h | 8 ++++++++
> ofproto/ofproto-dpif.c | 4 ++--
> tests/test-classifier.c | 2 +-
> 3 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/lib/util.h b/lib/util.h
> index ef464ea..ca1d566 100644
> --- a/lib/util.h
> +++ b/lib/util.h
> @@ -103,6 +103,14 @@ rightmost_1bit(uintmax_t x)
> return x & -x;
> }
>
> +/* Returns 'x' with its rightmost 1-bit changed to a zero (e.g. 01011000 =>
> + * 01010000), or 0 if 'x' is 0. */
> +static inline uintmax_t
> +zero_rightmost_1bit(uintmax_t x)
> +{
> + return x & (x - 1);
> +}
> +
> #ifndef MIN
> #define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
> #endif
> diff --git a/ofproto/ofproto-dpif.c b/ofproto/ofproto-dpif.c
> index 44cbd17..e21a6a2 100644
> --- a/ofproto/ofproto-dpif.c
> +++ b/ofproto/ofproto-dpif.c
> @@ -5930,7 +5930,7 @@ add_mirror_actions(struct action_xlate_ctx *ctx, const
> struct flow *orig_flow)
> m = ofproto->mirrors[mirror_mask_ffs(mirrors) - 1];
>
> if (!vlan_is_mirrored(m, vlan)) {
> - mirrors &= mirrors - 1;
> + mirrors = zero_rightmost_1bit(mirrors);
> continue;
> }
>
> @@ -5960,7 +5960,7 @@ update_mirror_stats(struct ofproto_dpif *ofproto,
> mirror_mask_t mirrors,
> return;
> }
>
> - for (; mirrors; mirrors &= mirrors - 1) {
> + for (; mirrors; mirrors = zero_rightmost_1bit(mirrors)) {
> struct ofmirror *m;
>
> m = ofproto->mirrors[mirror_mask_ffs(mirrors) - 1];
> diff --git a/tests/test-classifier.c b/tests/test-classifier.c
> index d4a524d..3ee6ddb 100644
> --- a/tests/test-classifier.c
> +++ b/tests/test-classifier.c
> @@ -769,7 +769,7 @@ count_ones(unsigned long int x)
> int n = 0;
>
> while (x) {
> - x &= x - 1;
> + x = zero_rightmost_1bit(x);
> n++;
> }
>
> --
> 1.7.2.5
>
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