[ovs-dev] [classifier-opt 22/28] util: New function zero_rightmost_1bit().
Ben Pfaff
blp at nicira.com
Fri Jul 20 23:25:19 UTC 2012
It's probably easier to understand
x = zero_rightmost_1bit(x);
than
x &= x - 1;
Signed-off-by: Ben Pfaff <blp at 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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