diff mbox

[4/6] utils: add fls()

Message ID 1418343756-2886-5-git-send-email-kaber@trash.net
State Accepted
Delegated to: Pablo Neira
Headers show

Commit Message

Patrick McHardy Dec. 12, 2014, 12:22 a.m. UTC 
Signed-off-by: Patrick McHardy <kaber@trash.net>
---
 include/utils.h | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)
diff mbox

Patch

diff --git a/include/utils.h b/include/utils.h
index 15b2e39..45cb5a7 100644
--- a/include/utils.h
+++ b/include/utils.h
@@ -76,6 +76,43 @@ 
 	(void) (&_max1 == &_max2);		\
 	_max1 > _max2 ? _max1 : _max2; })
 
+
+/**
+ * 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;
+}
+
 extern void __memory_allocation_error(const char *filename, uint32_t line) __noreturn;
 
 #define memory_allocation_error()		\