util: New function popcount().

[openvswitch] / lib / util.h

diff --git a/lib/util.h b/lib/util.h
index 57527fcc686edbfcedcf5149ecf369a69e123758..a8d86657325287b6c64b033491f4e6a8d0f5197b 100644 (file)
--- a/lib/util.h
+++ b/lib/util.h
@@ -17,6 +17,7 @@
 #ifndef UTIL_H
 #define UTIL_H 1
 
+#include <limits.h>
 #include <stdarg.h>
 #include <stdbool.h>
 #include <stddef.h>
@@ -103,6 +104,14 @@ 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
@@ -236,6 +245,7 @@ void ignore(bool x OVS_UNUSED);
 int log_2_floor(uint32_t);
 int log_2_ceil(uint32_t);
 int ctz(uint32_t);
+int popcount(uint32_t);
 
 bool is_all_zeros(const uint8_t *, size_t);
 bool is_all_ones(const uint8_t *, size_t);