Implement ffsl() and ffsll() using the compiler builtin __builtin_ctzl

now that all archs use at least gcc4.
ffsl() and ffsll() are now part of POSIX.
OK deraadt@, input from miod@ and jsg@

1 files changed, 17 insertions, 0 deletions

diff --git a/src/lib/libc/string/ffsl.c b/src/lib/libc/string/ffsl.c
new file mode 100644
index 0000000000..182318c3d6
--- /dev/null
+++ b/src/lib/libc/string/ffsl.c
@@ -0,0 +1,17 @@
+/*      $OpenBSD: ffsl.c,v 1.1 2025/10/24 11:30:06 claudio Exp $        */
+
+/*
+ * Public domain.
+ * Written by Claudio Jeker.
+ */
+
+#include <strings.h>
+
+/*
+ * ffs -- find the first (least significant) bit set
+ */
+int
+ffsl(long mask)
+{
+        return (mask ? __builtin_ctzl(mask) + 1 : 0);
+}