utils: Adding content store trace helper class (thanks to Xiaoyan Hu)
diff --git a/utils/tracers/ndn-cs-tracer.h b/utils/tracers/ndn-cs-tracer.h
new file mode 100644
index 0000000..5b057f7
--- /dev/null
+++ b/utils/tracers/ndn-cs-tracer.h
@@ -0,0 +1,121 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+/*
+ * Copyright (c) 2011-2012 University of California, Los Angeles
+ *
+ * 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: Xiaoyan Hu <x......u@gmail.com>
+ *         Alexander Afanasyev <alexander.afanasyev@ucla.edu>
+ */
+
+#ifndef CCNX_CS_TRACER_H
+#define CCNX_CS_TRACER_H
+
+#include "ns3/ptr.h"
+#include "ns3/simple-ref-count.h"
+
+namespace ns3 {
+
+class Node;
+class Packet;
+
+namespace ndn {
+
+class InterestHeader;
+class ContentObjectHeader;
+
+/**
+ * @brief Base class for content store tracers (CacheHits and CacheMisses)
+ */
+class CsTracer : public SimpleRefCount<CsTracer>
+{
+public:
+  /**
+   * @brief Trace constructor that attaches to the node using node pointer
+   * @param node  pointer to the node
+   */
+  CsTracer (Ptr<Node> node);
+
+  /**
+   * @brief Trace constructor that attaches to the node using node name
+   * @param nodeName  name of the node registered using Names::Add
+   */
+  CsTracer (const std::string &node);
+
+  /**
+   * @brief Destructor
+   */
+  virtual ~CsTracer ();
+
+  /**
+   * @brief Print head of the trace (e.g., for post-processing)
+   *
+   * @param os reference to output stream
+   */
+  virtual void
+  PrintHeader (std::ostream &os) const = 0;
+
+  /**
+   * @brief Print current trace data
+   *
+   * @param os reference to output stream
+   */
+  virtual void
+  Print (std::ostream &os) const = 0;
+  
+protected:
+  void
+  Connect ();
+
+  virtual void 
+  CacheHits (std::string context,
+  Ptr<const InterestHeader>, Ptr<const ContentObjectHeader>) = 0;
+  
+  virtual void 
+  CacheMisses (std::string context,
+  Ptr<const InterestHeader>) = 0;
+
+protected:
+  std::string m_node;
+  Ptr<Node> m_nodePtr;
+
+  struct Stats
+  {
+    inline void Reset ()
+    {
+      m_cacheHits   = 0;
+      m_cacheMisses = 0;
+    }
+    double m_cacheHits;
+    double m_cacheMisses;
+  };
+};
+
+/**
+ * @brief Helper to dump the trace to an output stream
+ */
+inline std::ostream&
+operator << (std::ostream &os, const CsTracer &tracer)
+{
+  os << "# ";
+  tracer.PrintHeader (os);
+  os << "\n";
+  tracer.Print (os);
+  return os;
+}
+
+} // namespace ndn
+} // namespace ns3
+
+#endif // CCNX_CS_TRACER_H