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authorAkinobu Mita <mita@miraclelinux.com>2006-03-26 01:39:12 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-26 08:57:11 -0800
commit09020adb61416c4307de35941a9725a5e33d9beb (patch)
tree1bce6f1c62a2960e1442913f93727980ec1dfa0b
parent6d29ea23da033f46ac4ab359d46650a7f7474611 (diff)
[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>
-rw-r--r--include/asm-generic/bitops/ffs.h41
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_ */