1 #include <linux/bitops.h>
2 
3 /**
4  * hweightN - returns the hamming weight of a N-bit word
5  * @x: the word to weigh
6  *
7  * The Hamming Weight of a number is the total number of bits set in it.
8  */
9 
hweight32(unsigned int w)10 unsigned int hweight32(unsigned int w)
11 {
12 	unsigned int res = w - ((w >> 1) & 0x55555555);
13 	res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
14 	res = (res + (res >> 4)) & 0x0F0F0F0F;
15 	res = res + (res >> 8);
16 	return (res + (res >> 16)) & 0x000000FF;
17 }
18 
hweight64(__u64 w)19 unsigned long hweight64(__u64 w)
20 {
21 #if BITS_PER_LONG == 32
22 	return hweight32((unsigned int)(w >> 32)) + hweight32((unsigned int)w);
23 #elif BITS_PER_LONG == 64
24 	__u64 res = w - ((w >> 1) & 0x5555555555555555ul);
25 	res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
26 	res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful;
27 	res = res + (res >> 8);
28 	res = res + (res >> 16);
29 	return (res + (res >> 32)) & 0x00000000000000FFul;
30 #endif
31 }
32