diff options
| author | Akinobu Mita <mita@miraclelinux.com> | 2006-03-26 01:39:09 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-26 08:57:10 -0800 |
| commit | 136abb32d6b4acf196425fb3968ebb368d84280e (patch) | |
| tree | 48f0f127f204569b4484bac6ab014f8ca36f7477 | |
| parent | 176d8b0c2709e764d491e63a0c1b3a3e1459fcf8 (diff) | |
[PATCH] bitops: generic fls()
This patch introduces the C-language equivalent of the function: int fls(int
x);
In include/asm-generic/bitops/fls.h
This code largely copied from: include/linux/bitops.h
Signed-off-by: Akinobu Mita <mita@miraclelinux.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
| -rw-r--r-- | include/asm-generic/bitops/fls.h | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/include/asm-generic/bitops/fls.h b/include/asm-generic/bitops/fls.h new file mode 100644 index 000000000000..850859bc5069 --- /dev/null +++ b/include/asm-generic/bitops/fls.h @@ -0,0 +1,41 @@ +#ifndef _ASM_GENERIC_BITOPS_FLS_H_ +#define _ASM_GENERIC_BITOPS_FLS_H_ + +/** + * fls - find last (most-significant) bit set + * @x: the word to search + * + * This is defined the same way as ffs. + * Note fls(0) = 0, fls(1) = 1, fls(0x80000000) = 32. + */ + +static inline int fls(int x) +{ + int r = 32; + + if (!x) + return 0; + if (!(x & 0xffff0000u)) { + x <<= 16; + r -= 16; + } + if (!(x & 0xff000000u)) { + x <<= 8; + r -= 8; + } + if (!(x & 0xf0000000u)) { + x <<= 4; + r -= 4; + } + if (!(x & 0xc0000000u)) { + x <<= 2; + r -= 2; + } + if (!(x & 0x80000000u)) { + x <<= 1; + r -= 1; + } + return r; +} + +#endif /* _ASM_GENERIC_BITOPS_FLS_H_ */ |