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Arnaldo Carvalho de Melofb720142010-04-30 19:31:12 -03001#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
10unsigned 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
19unsigned 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}