| Jens Axboe | 51aa2da | 2013-01-21 10:55:02 -0700 | [diff] [blame] | 1 | #include "hweight.h" |
| 2 | |
| 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 | |
| 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 | } |
| Jens Axboe | def823d | 2013-01-21 12:28:23 -0700 | [diff] [blame^] | 20 | |
| 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) & 0x5555555555555555ul); |
| 27 | res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul); |
| 28 | res = (res + (res >> 4)) & 0x0F0F0F0F0F0F0F0Ful; |
| 29 | res = res + (res >> 8); |
| 30 | res = res + (res >> 16); |
| 31 | return (res + (res >> 32)) & 0x00000000000000FFul; |
| 32 | #endif |
| 33 | } |