[patch 13/44] generic ffs()

Akinobu Mita
2006-02-01T09:19:59Z

[-- Attachment #1: ffs-bitops.patch --]
[-- Type: text/plain, Size: 1195 bytes --]

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>
include/asm-generic/bitops/ffs.h | 41 +++++++++++++++++++++++++++++++++++++++
1 files changed, 41 insertions(+)

Index: 2.6-git/include/asm-generic/bitops/ffs.h
===================================================================
--- /dev/null
+++ 2.6-git/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_ */

--