#ifndef PROTOCOL_H
#define PROTOCOL_H
///////////////////////////////////////////////////////////////
//  protocol.h - define protocol class                       //
//  ver 1.1                                                  //
//                                                           //
//  this is all the client knows about the protocol, e.g.,   //
//  the language                                             //
///////////////////////////////////////////////////////////////


// design note:
// ------------
// Protocol class hierarchies (sometimes called homeomorphic
// class structures) consist of an abstract base class and
// usually a single layer of derived classes.  The base class
// provides a language, or protocol, for client access to all
// the derived classes.  Clients know only the protocol, but
// not any of the details which distinguish one class from
// another.
//
// The derived classes provide all of the real functionality.
// The client code, however, does not need to know how any of
// the derived classes do their business.
//
// In this demonstration the member functions getInt() and
// putInt() are pure virtual functions so protocol class is an
// abstract base class.
//
// No protocol objects can be created.  Only objects of derived
// classes which give definitions for both the pure virtual
// functions are concrete and can create objects.
//
// However, since the make_d1() and make_d2() protocol member
// functions are static they don't need objects to invoke them.
// Client code can do that with the syntax protocol::make_d1(),
// etc.  So, we can invoke static members of an abstract class.
// We do just that in the client code in protocol.cpp


//                          +-----------+
//                          | protocol  |
//                          +-----+-----+
//                                |
//                               / \
//                 +--------------+--------------+
//                 |              |              |
//           +-----+-----+  +-----+-----+  +-----+-----+
//           | derived1  |  | derived2  |  | more der  |
//           +-----------+  +-----------+  +-----------+

//

///////////////////////////////////////////////////////////////
//  build process                                            //
///////////////////////////////////////////////////////////////
//  Required files:                                          //
//    protocol.h, derived1.cpp derived2.cpp                  //
//                                                           //
//  To build in integrated environment:                      //
//    - create Win32 Dynamic-Link Library project            //
//      named dynLL                                          //
//    - protocol.h, derived1.cpp and derived2.cpp            //
//    - build                                                //
///////////////////////////////////////////////////////////////


#ifdef IN_DLL
  #define DLL_DECL __declspec(dllexport)
#else
  #define DLL_DECL __declspec(dllimport)
#endif

class protocol {

  public:
    virtual int getInt() = 0;
    virtual void putInt(int) = 0;
    virtual void kill() = 0;
    static DLL_DECL protocol* make_d1();
    static DLL_DECL protocol* make_d2();
};
#endif