1 files changed, 26 insertions, 0 deletions
diff --git a/src/libstddjb/ip6_netmask.c b/src/libstddjb/ip6_netmask.c
new file mode 100644
index 0000000..5d8b13e
--- /dev/null
+++ b/src/libstddjb/ip6_netmask.c
@@ -0,0 +1,26 @@
+/* ISC license. */
+
+#include <string.h>
+
+#include <skalibs/uint64.h>
+#include <skalibs/fmtscan.h>
+
+static void apply (char *half, uint8_t netmask)
+{
+  uint64_t u ;
+  uint64_unpack_big(half, &u) ;
+  u &= netmask ? ~((1ull << 64 - netmask) - 1) : 0 ;
+  uint64_pack_big(half, u) ;
+}
+
+int ip6_netmask (char *ip, uint8_t netmask)
+{
+  if (netmask > 128) return 0 ;
+  if (netmask <= 64)
+  {
+    apply(ip, netmask) ;
+    memset(ip + 8, 0, 8) ;
+  }
+  else apply(ip + 8, netmask - 64) ;
+  return 1 ;
+}