Implementing visitor pattern for CCNx message parsing. Needs debugging.

Altering src/network/model/buffer* to support more Iterator features
diff --git a/helper/ccnx-encoding-helper.h b/helper/ccnx-encoding-helper.h
new file mode 100644
index 0000000..90fad22
--- /dev/null
+++ b/helper/ccnx-encoding-helper.h
@@ -0,0 +1,97 @@
+/* -*- Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil -*- */
+/*
+ * Copyright (c) 2011 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: 
+ */
+
+#ifndef _CCNX_ENCODING_HELPER_H_
+#define _CCNX_ENCODING_HELPER_H_
+
+#include <sys/types.h>
+
+#include "ns3/ccnx.h"
+#include "ns3/ptr.h"
+#include "ns3/nstime.h"
+#include "ns3/buffer.h"
+
+namespace ns3 {
+
+namespace Name{ class Components; }
+
+class CcnxInterestHeader;
+class CcnxContentObjectHeader;
+  
+/**
+ * Helper to encode/decode ccnb formatted CCNx message
+ *
+ */
+class CcnxEncodingHelper
+{
+public:
+  static size_t
+  Serialize (Buffer::Iterator start, const CcnxInterestHeader &interest);
+
+  static size_t
+  Serialize (Buffer::Iterator start, const CcnxContentObjectHeader &contentObject);
+
+private:
+  static size_t
+  AppendBlockHeader (Buffer::Iterator start, size_t value, Ccnx::ccn_tt block_type);
+
+  static size_t
+  AppendNumber (Buffer::Iterator start, uint32_t number);
+
+  static size_t
+  AppendCloser (Buffer::Iterator start);
+
+  static size_t
+  AppendNameComponents (Buffer::Iterator start, const Name::Components &name);
+
+  /**
+   * Append a binary timestamp as a BLOB using the ccn binary
+   * Timestamp representation (12-bit fraction).
+   *
+   * @param start start iterator of  the buffer to append to.
+   * @param time - Time object
+   *
+   * @returns written length
+   */
+  static size_t
+  AppendTimestampBlob (Buffer::Iterator start, Time time);
+
+  /**
+   * Append a tagged BLOB
+   *
+   * This is a ccnb-encoded element with containing the BLOB as content
+   *
+   * @param start start iterator of  the buffer to append to.
+   * @param dtag is the element's dtab
+   * @param data points to the binary data
+   * @param size is the size of the data, in bytes
+   *
+   * @returns written length
+   */
+  static size_t
+  AppendTaggedBlob (Buffer::Iterator start, Ccnx::ccn_dtag dtag,
+                    const uint8_t *data, size_t size);
+  
+};
+
+} // namespace ns3
+
+#endif // _CCNX_ENCODING_HELPER_H_
+