1 files changed, 14 insertions, 0 deletions
diff --git a/src/libstddjb/ip4_netmask.c b/src/libstddjb/ip4_netmask.c
new file mode 100644
index 0000000..19f485f
--- /dev/null
+++ b/src/libstddjb/ip4_netmask.c
@@ -0,0 +1,14 @@
+/* ISC license. */
+
+#include <skalibs/uint32.h>
+#include <skalibs/fmtscan.h>
+
+int ip4_netmask (char *ip, uint8_t netmask)
+{
+  uint32_t u ;
+  if (netmask > 32) return 0 ;
+  uint32_unpack_big(ip, &u) ;
+  u &= netmask ? ~((1u << 32 - netmask) - 1) : 0 ;
+  uint32_pack_big(ip, u) ;
+  return 1 ;
+}