1 files changed, 40 insertions, 0 deletions
diff --git a/contrib/ipfilter/lib/count4bits.c b/contrib/ipfilter/lib/count4bits.c
new file mode 100644
index 0000000..a847388
--- /dev/null
+++ b/contrib/ipfilter/lib/count4bits.c
@@ -0,0 +1,40 @@
+/*	$FreeBSD$	*/
+
+/*
+ * Copyright (C) 2012 by Darren Reed.
+ *
+ * See the IPFILTER.LICENCE file for details on licencing.
+ *
+ * $Id$
+ */
+
+#include "ipf.h"
+
+
+/*
+ * count consecutive 1's in bit mask.  If the mask generated by counting
+ * consecutive 1's is different to that passed, return -1, else return #
+ * of bits.
+ */
+int	count4bits(ip)
+	u_int	ip;
+{
+	int cnt = 0, i, j;
+	u_int ipn;
+
+	ip = ipn = ntohl(ip);
+	for (i = 32; i; i--, ipn *= 2)
+		if (ipn & 0x80000000)
+			cnt++;
+		else
+			break;
+	ipn = 0;
+	for (i = 32, j = cnt; i; i--, j--) {
+		ipn *= 2;
+		if (j > 0)
+			ipn++;
+	}
+	if (ipn == ip)
+		return cnt;
+	return -1;
+}