1 files changed, 48 insertions, 0 deletions

diff --git a/src/lib/libc/string/ffs.c b/src/lib/libc/string/ffs.c
new file mode 100644
index 0000000000..f1d14096a2
--- /dev/null
+++ b/src/lib/libc/string/ffs.c
@@ -0,0 +1,48 @@
+/*      $OpenBSD: ffs.c,v 1.6 2003/06/11 21:08:16 deraadt Exp $ */
+
+/*
+ * Public domain.
+ * Written by Dale Rahn.
+ */
+
+#if defined(LIBC_SCCS) && !defined(lint)
+static char *rcsid = "$OpenBSD: ffs.c,v 1.6 2003/06/11 21:08:16 deraadt Exp $";
+#endif /* LIBC_SCCS and not lint */
+
+#if !defined(_KERNEL) && !defined(_STANDALONE)
+#include <string.h>
+#else
+#include <lib/libkern/libkern.h>
+#endif
+
+/*
+ * ffs -- vax ffs instruction
+ */
+int
+ffs(int mask)
+{
+        int bit;
+        unsigned int r = mask;
+        static const signed char t[16] = {
+                -28, 1, 2, 1,
+                  3, 1, 2, 1,
+                  4, 1, 2, 1,
+                  3, 1, 2, 1
+        };
+
+        bit = 0;
+        if (!(r & 0xffff)) {
+                bit += 16;
+                r >>= 16;
+        }
+        if (!(r & 0xff)) {
+                bit += 8;
+                r >>= 8;
+        }
+        if (!(r & 0xf)) {
+                bit += 4;
+                r >>= 4;
+        }
+
+        return (bit + t[ r & 0xf ]);
+}