| Arnaldo Carvalho de Melo | fb72014 | 2010-04-30 19:31:12 -0300 | [diff] [blame] | 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 | } |