Use const where possible.
diff --git a/ndn-cpp/encoding/WireFormat.hpp b/ndn-cpp/encoding/WireFormat.hpp
index d9811cd..f09ae22 100644
--- a/ndn-cpp/encoding/WireFormat.hpp
+++ b/ndn-cpp/encoding/WireFormat.hpp
@@ -15,10 +15,10 @@
   
 class WireFormat {
 public:
-  virtual void encodeName(Name &name, std::vector<unsigned char> &output);
+  virtual void encodeName(const Name &name, std::vector<unsigned char> &output);
   virtual void decodeName(Name &name, const unsigned char *input, unsigned int inputLength);
 
-  virtual void encodeInterest(Interest &interest, std::vector<unsigned char> &output);
+  virtual void encodeInterest(const Interest &interest, std::vector<unsigned char> &output);
   virtual void decodeInterest(Interest &interest, const unsigned char *input, unsigned int inputLength);
 
   // etc. for each type of object.