Add inline fls() function for linux

1 files changed, 31 insertions, 0 deletions

diff --git a/netifd.h b/netifd.h
index b70b73c..77c8719 100644
--- a/netifd.h
+++ b/netifd.h
@@ -30,4 +30,35 @@ extern bool config_init;
 int avl_strcmp(const void *k1, const void *k2, void *ptr);
 void config_init_interfaces(const char *name);
 
+#ifdef __linux__
+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;
+}
+#endif
+
 #endif