Introduce Delegation and DelegationList

DelegationList will become the payload structure of ForwardingHint
and LinkContent in a later commit.

refs #4055

Change-Id: If29a39c47b779aafdd4aebb104092403f28e6653
diff --git a/src/delegation.hpp b/src/delegation.hpp
new file mode 100644
index 0000000..4e73ebe
--- /dev/null
+++ b/src/delegation.hpp
@@ -0,0 +1,70 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2013-2017 Regents of the University of California.
+ *
+ * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
+ *
+ * ndn-cxx library is free software: you can redistribute it and/or modify it under the
+ * terms of the GNU Lesser General Public License as published by the Free Software
+ * Foundation, either version 3 of the License, or (at your option) any later version.
+ *
+ * ndn-cxx library is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.
+ *
+ * You should have received copies of the GNU General Public License and GNU Lesser
+ * General Public License along with ndn-cxx, e.g., in COPYING.md file.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
+ */
+
+#ifndef NDN_DELEGATION_HPP
+#define NDN_DELEGATION_HPP
+
+#include "name.hpp"
+
+namespace ndn {
+
+/** \brief represents a delegation
+ *  \sa https://named-data.net/doc/ndn-tlv/link.html
+ */
+struct Delegation
+{
+  uint64_t preference;
+  Name name;
+};
+
+bool
+operator==(const Delegation& lhs, const Delegation& rhs);
+
+inline bool
+operator!=(const Delegation& lhs, const Delegation& rhs)
+{
+  return !(lhs == rhs);
+}
+
+bool
+operator<(const Delegation& lhs, const Delegation& rhs);
+
+bool
+operator<=(const Delegation& lhs, const Delegation& rhs);
+
+inline bool
+operator>(const Delegation& lhs, const Delegation& rhs)
+{
+  return !(lhs <= rhs);
+}
+
+inline bool
+operator>=(const Delegation& lhs, const Delegation& rhs)
+{
+  return !(lhs < rhs);
+}
+
+std::ostream&
+operator<<(std::ostream& os, const Delegation& del);
+
+} // namespace ndn
+
+#endif // NDN_DELEGATION_HPP