Adding SpringMobilityModel to adjust positions of nodes in large
topologies

Inspired by http://en.wikipedia.org/wiki/Force-based_algorithms_%28graph_drawing%29
diff --git a/utils/spring-mobility-helper.cc b/utils/spring-mobility-helper.cc
new file mode 100644
index 0000000..5e4b4f6
--- /dev/null
+++ b/utils/spring-mobility-helper.cc
@@ -0,0 +1,51 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2006, 2007 INRIA
+ *
+ * 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: Alexander Afanasyev <alexander.afanasyev@ucla.edu>
+ */
+
+#include "spring-mobility-helper.h"
+#include "spring-mobility-model.h"
+
+namespace ns3 {
+
+void
+SpringMobilityHelper::InstallSprings (Ptr<Node> node1, Ptr<Node> node2)
+{
+  Ptr<SpringMobilityModel> model1, model2;
+  model1 = node1->GetObject<SpringMobilityModel> ();
+  model2 = node2->GetObject<SpringMobilityModel> ();
+  
+  NS_ASSERT (model1 != 0 && model2 != 0);
+
+  model1->AddSpring (model2);
+  model2->AddSpring (model1);
+}
+
+void
+SpringMobilityHelper::InstallSprings (TopologyReader::ConstLinksIterator first, 
+				      TopologyReader::ConstLinksIterator end)
+{
+  for (; first != end; first++)
+    {
+      InstallSprings (first->GetFromNode (), 
+		      first->GetToNode ());
+    }
+}
+
+} // namespace ns3
+