security: Added headers for der encoding. Added CertificateExtension and CertificateSubjectDescription.
diff --git a/ndn-cpp/encoding/der/visitor/void-visitor.hpp b/ndn-cpp/encoding/der/visitor/void-visitor.hpp
new file mode 100644
index 0000000..a041c10
--- /dev/null
+++ b/ndn-cpp/encoding/der/visitor/void-visitor.hpp
@@ -0,0 +1,36 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+/**
+ * Copyright (C) 2013 Regents of the University of California.
+ * @author: Yingdi Yu <yingdi@cs.ucla.edu>
+ * @author: Jeff Thompson <jefft0@remap.ucla.edu>
+ * See COPYING for copyright and distribution information.
+ */
+
+#ifndef NDN_DER_VOID_VISITOR_HPP
+#define NDN_DER_VOID_VISITOR_HPP
+
+#include "visitor.hpp"
+
+namespace ndn {
+
+namespace der {
+
+class VoidVisitor
+{
+public:
+ virtual void visit(DerBool&, Any) = 0;
+ virtual void visit(DerInteger&, Any) = 0;
+ virtual void visit(DerPrintableString&, Any) = 0;
+ virtual void visit(DerBitString&, Any) = 0;
+ virtual void visit(DerNull&, Any) = 0;
+ virtual void visit(DerOctetString&, Any) = 0;
+ virtual void visit(DerOid&, Any) = 0;
+ virtual void visit(DerSequence&, Any) = 0;
+ virtual void visit(DerGtime&, Any) = 0;
+};
+
+} // der
+
+}
+
+#endif