From 09020adb61416c4307de35941a9725a5e33d9beb Mon Sep 17 00:00:00 2001 From: Akinobu Mita Date: Sun, 26 Mar 2006 01:39:12 -0800 Subject: [PATCH] [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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-generic/bitops/ffs.h | 41 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+) create mode 100644 include/asm-generic/bitops/ffs.h diff --git a/include/asm-generic/bitops/ffs.h b/include/asm-generic/bitops/ffs.h new file mode 100644 index 0000000..fbbb43a --- /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_ */ -- 2.7.4