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fb72014d ACM |
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 | ||
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 | ||
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 | } |