Re: Implementing call back functions effeciantly

From:

"Chris Thomasson" <xxx@xxx.xxx>

Newsgroups:

comp.lang.c++.moderated

Date:

Thu, 17 Jul 2008 11:33:23 CST

Message-ID:

<g5mtjp$eb$1@aioe.org>

"shiva" <dudeofindia@gmail.com> wrote in message
news:12ed3f3f-251d-4765-a60a-29f38cc1146e@56g2000hsm.googlegroups.com...

Hi All..
I am a novice to C++ and working on one networking project.
In which, some of my application layer functions should be executed
when some event occur in network.

For this, i thought of using callback functions concept.

is it the best way? It will be helpful, if some of you suggest best
way for such implementation.

If callback concept is best, how i use this efficiently.
it will be helpful, if ypu provide some good URL to study.

[...]

Here is a VERY simple and NAIVE approach that you can try:

<crude pseudo-code; typed in the newsreader!>
_______________________________________________________________________

class Network_Connection_Callbacks;

// System-Code
class Network_Connection {
      [...];

  static void Connect(Network_Connection_Callbacks*, [...]);

  void Send(std::size_t, void*);
  void Recv(std::size_t, void*);
};

class Network_Connection_Callbacks {
  virtual void On_Connect(Network_Connection&) = 0;
  virtual void On_Disconnect(Network_Connection&) = 0;
  virtual void On_Send(Network_Connection&, std::size_t, void*) = 0;
  virtual void On_Recv(Network_Connection&, std::size_t, void*) = 0;
public:
  virtual ~Network_Connection_Callbacks() = 0;
};

Network_Connection_Callbacks::~Network_Connection_Callbacks() {}

// Example User-Code
class My_Network_Connection_Handler
  : public Network_Connection_Callbacks {

  void On_Connect(Network_Connection& this_connection) {
      [Handle the new connection...];
  }

  void On_Disconnect(Network_Connection& this_connection) {
      [Handle the disconnection...];
  }

  void On_Send(Network_Connection& this_connection, std::size_t Size, void*
Buf) {
      [Handle the fact that data was sent...];
  }

  void On_Recv(Network_Connection& this_connection, std::size_t Size, void*
Buf) {
      [Handle the fact that data was received...];
  }
};

_______________________________________________________________________

A simple echo server might look like:

class My_Echo_Server : public Network_Connection_Callbacks {
  void On_Connect(Network_Connection& this_connection) {
    this_connection.Send(7, "Repeat");
  }

  void On_Disconnect(Network_Connection& this_connection) {
      [Handle the disconnection...];
  }

  void On_Send(Network_Connection& this_connection, std::size_t Size, void*
Buf) {
    this_connection.Recv(Size, buf);
  }

  void On_Recv(Network_Connection& this_connection, std::size_t Size, void*
Buf) {
    this_connection.Send(Size, Buf);
  }
};

// you could possible start it like
My_Echo_Server* Spawn_Echo_Connection() {
  My_Echo_Server* echo = new My_Echo_Server;
  Network_Connection::Connect(echo, ADDR, PORT);
  return echo;
}

That is about as simple as I can get... Does that even begin to help you?

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