+int get_number_of_bits(int bits)
+{
+ /*
+ Counting bits set, Brian Kernighan's way
+
+ Brian Kernighan's method goes through as many iterations as there are set
+ bits. So if we have a 32-bit word with only the high bit set, then it will
+ only go once through the loop.
+
+ Published in 1988, the C Programming Language 2nd Ed. (by Brian W. Kernighan
+ and Dennis M. Ritchie) mentions this in exercise 2-9.
+ First published by Peter Wegner in CACM 3 (1960), 322.
+ */
+
+ int num_bits = 0;
+
+ while (bits)
+ {
+ bits &= bits - 1; // clear the least significant bit set
+ num_bits++;
+ }
+
+ return num_bits;
+}
+