Re: Compile-time polymorphism of "interfaces"

Thanks guys for your responses. I am going to look into CRTP and the
adapter pattern. I think I didn't explain myself clearly. Let me try
again.

We have "Port" and "Protocol" classes. We want to re-use the complex
protocol logic on different hardware. To do this, the Protocol has to
be able to call the Port to do a send, and the Port has to be able to
call the Protocol to do a receive. So both of them have to have a
binary interface to the other. We used "interfaces" (pure virtual
functions in base classes) to binary interfaces, but we seem to have a
performance hit.

I think all the information is actually available at compile time...
but I seem to get circular definitions when I try to make templates.

So what we have is sort of like this:

    class Protocol{public: virtual void Receive(BYTE* pbMsg, int iLen)
= 0;};
    class Port{public: virtual void Send(BYTE* pbMsg, int iLen) =
0;};

    class ActualProtocol : public Protocol
    {
    Port* m_pPort;
    public: virtual void Receive(BYTE* pbMsg, int iLen) {
        //just send it back (dummy)
        m_pPort->Send(pbMsg, iLen);
       }
    };

    class ActualPort : public Port
    {
    Protocol* m_pProtocol
    public: virtual void Send(BYTE* pbMsg, int iLen){//physically
write it out }
    void Interrupt() {
       BYTE BytesExtracted[1024];
       int iNumExtracted = 0;
       //extract bytes from hardware....
       m_pProtocol->Receive(BytesExtracted, iNumExtracted);
    }
    };

When I try to think of these as templates I seem to get circular
definitions such as:

template<typename Port>
class Protocol {
       Port& m_rPort;
       public:
           Protocol(Port& rPort):m_rPort(rPort){}

           void Receive(BYTE* pbMsg, int iLen) {
               m_rPort.Send(pbMsg, iLen);
           }
       };

       template<typename Protocol>
       class Port {
              Protocol& m_rProtocol;
              public:
              Port(Protocol& rProtocol):m_rProtocol(rProtocol){}

              void Interrupt() {
                     BYTE BytesExtracted[1024];
                     int iNumExtracted = 0;
                     //extract bytes from hardware....
                     m_rProtocol.Receive(BytesExtracted,
iNumExtracted);
              }

              void Send(BYTE* pbMsg, int iMsgLen){//physically
write it out }
       };

Now if you try to instantiate these, each in terms of the other....
well, I'm not sure how to do that.

Any suggestions?

Thanks

Andy

--
      [ See http://www.gotw.ca/resources/clcm.htm for info about ]
      [ comp.lang.c++.moderated. First time posters: Do this! ]