| Thomas Chou | 29e9e29 | 2010-03-20 07:05:46 +0800 | [diff] [blame] | 1 | #ifndef _ASM_GENERIC_BITOPS_FFS_H_ |
| 2 | #define _ASM_GENERIC_BITOPS_FFS_H_ |
| 3 | |
| 4 | /** |
| 5 | * ffs - find first bit set |
| 6 | * @x: the word to search |
| 7 | * |
| 8 | * This is defined the same way as |
| 9 | * the libc and compiler builtin ffs routines, therefore |
| 10 | * differs in spirit from the above ffz (man ffs). |
| 11 | */ |
| 12 | static inline int ffs(int x) |
| 13 | { |
| 14 | int r = 1; |
| 15 | |
| 16 | if (!x) |
| 17 | return 0; |
| 18 | if (!(x & 0xffff)) { |
| 19 | x >>= 16; |
| 20 | r += 16; |
| 21 | } |
| 22 | if (!(x & 0xff)) { |
| 23 | x >>= 8; |
| 24 | r += 8; |
| 25 | } |
| 26 | if (!(x & 0xf)) { |
| 27 | x >>= 4; |
| 28 | r += 4; |
| 29 | } |
| 30 | if (!(x & 3)) { |
| 31 | x >>= 2; |
| 32 | r += 2; |
| 33 | } |
| 34 | if (!(x & 1)) { |
| 35 | x >>= 1; |
| 36 | r += 1; |
| 37 | } |
| 38 | return r; |
| 39 | } |
| 40 | |
| 41 | #endif /* _ASM_GENERIC_BITOPS_FFS_H_ */ |