1 #include "hweight.h"
2 
hweight8(uint8_t w)3 unsigned int hweight8(uint8_t w)
4 {
5 	unsigned int res = w - ((w >> 1) & 0x55);
6 
7 	res = (res & 0x33) + ((res >> 2) & 0x33);
8 	return (res + (res >> 4)) & 0x0F;
9 }
10 
hweight32(uint32_t w)11 unsigned int hweight32(uint32_t w)
12 {
13 	unsigned int res = w - ((w >> 1) & 0x55555555);
14 
15 	res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
16 	res = (res + (res >> 4)) & 0x0F0F0F0F;
17 	res = res + (res >> 8);
18 	return (res + (res >> 16)) & 0x000000FF;
19 }
20 
hweight64(uint64_t w)21 unsigned int hweight64(uint64_t w)
22 {
23 #if BITS_PER_LONG == 32
24 	return hweight32((unsigned int)(w >> 32)) + hweight32((unsigned int)w);
25 #else
26 	uint64_t res = w - ((w >> 1) & 0x5555555555555555ULL);
27 	res = (res & 0x3333333333333333ULL) + ((res >> 2) & 0x3333333333333333ULL);
28 	res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0FULL;
29 	res = res + (res >> 8);
30 	res = res + (res >> 16);
31 	return (res + (res >> 32)) & 0x00000000000000FFULL;
32 #endif
33 }
34