helper: Add LFID route calculation

Loop-Free In-port Dependent (LFID) route calculation provides a set of loop-free paths.

Basically porting the existing code from https://github.com/schneiderklaus/ndnSIM-routing

Refs: #4985
Change-Id: I1ab25e729851cf2233c3b99be715ba0159cca0c7
diff --git a/helper/lfid/fib-nexthop.cpp b/helper/lfid/fib-nexthop.cpp
new file mode 100644
index 0000000..dc3b069
--- /dev/null
+++ b/helper/lfid/fib-nexthop.cpp
@@ -0,0 +1,83 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/**
+ * Copyright (c) 2019 Klaus Schneider, The University of Arizona
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation;
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ * Author: Klaus Schneider <klaus@cs.arizona.edu>
+ */
+
+#include "fib-nexthop.hpp"
+
+#include <boost/functional/hash.hpp>
+#include <ostream>
+
+namespace ns3 {
+namespace ndn {
+
+constexpr int NODE_ID_LIMIT = 1000;
+
+FibNextHop::FibNextHop(int cost, int nhId, int costDelta, NextHopType type)
+{
+  NS_ABORT_UNLESS(cost > 0 && cost <= MAX_COST);
+  NS_ABORT_UNLESS(nhId >= 0 && nhId <= NODE_ID_LIMIT);
+
+  this->m_nhId = nhId;
+  this->m_cost = cost;
+  this->m_type = type;
+  this->m_costDelta = costDelta;
+}
+
+std::ostream&
+operator<<(std::ostream& os, const NextHopType& type)
+{
+  switch (type) {
+  case NextHopType::DOWNWARD:
+    return os << "DOWNWARD";
+  case NextHopType::UPWARD:
+    return os << "UPWARD";
+  case NextHopType::DISABLED:
+    return os << "DISABLED";
+  }
+  return os << static_cast<int>(type);
+}
+
+std::ostream&
+operator<<(std::ostream& os, const FibNextHop& a)
+{
+  return os << "Id: " << a.getNexthopId() << ", cost: " << a.m_cost << ", type: " << a.m_type;
+}
+
+} // namespace ndn
+} // namespace ns-3
+
+namespace std {
+
+using ns3::ndn::FibNextHop;
+
+template <>
+struct hash<FibNextHop> {
+  size_t
+  operator()(const FibNextHop& k) const
+  {
+    // Combine hash via boost library
+    std::size_t seed = 0;
+    boost::hash_combine(seed, k.getNexthopId());
+    boost::hash_combine(seed, k.getCost());
+
+    return seed;
+  }
+};
+
+}