diff options
author | Akinobu Mita <mita@miraclelinux.com> | 2006-03-26 11:39:12 +0200 |
---|---|---|
committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-03-26 18:57:11 +0200 |
commit | 09020adb61416c4307de35941a9725a5e33d9beb (patch) | |
tree | 1bce6f1c62a2960e1442913f93727980ec1dfa0b /include | |
parent | [PATCH] bitops: generic sched_find_first_bit() (diff) | |
download | linux-09020adb61416c4307de35941a9725a5e33d9beb.tar.xz linux-09020adb61416c4307de35941a9725a5e33d9beb.zip |
[PATCH] bitops: generic ffs()
This patch introduces the C-language equivalent of the function: int ffs(int
x);
In include/asm-generic/bitops/ffs.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>
Diffstat (limited to 'include')
-rw-r--r-- | include/asm-generic/bitops/ffs.h | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/include/asm-generic/bitops/ffs.h b/include/asm-generic/bitops/ffs.h new file mode 100644 index 000000000000..fbbb43af7dc0 --- /dev/null +++ b/include/asm-generic/bitops/ffs.h @@ -0,0 +1,41 @@ +#ifndef _ASM_GENERIC_BITOPS_FFS_H_ +#define _ASM_GENERIC_BITOPS_FFS_H_ + +/** + * ffs - find first bit set + * @x: the word to search + * + * This is defined the same way as + * the libc and compiler builtin ffs routines, therefore + * differs in spirit from the above ffz (man ffs). + */ +static inline int ffs(int x) +{ + int r = 1; + + if (!x) + return 0; + if (!(x & 0xffff)) { + x >>= 16; + r += 16; + } + if (!(x & 0xff)) { + x >>= 8; + r += 8; + } + if (!(x & 0xf)) { + x >>= 4; + r += 4; + } + if (!(x & 3)) { + x >>= 2; + r += 2; + } + if (!(x & 1)) { + x >>= 1; + r += 1; + } + return r; +} + +#endif /* _ASM_GENERIC_BITOPS_FFS_H_ */ |