Author: James CE Johnson

ACE Tutorial 015
Building a protocol stream

A quick look at the Protocol_Task header...

    // page12.html,v 1.12 1999/04/03 21:56:30 jcej Exp

    #ifndef PROTOCOL_TASK_H
    #define PROTOCOL_TASK_H

    #include "ace/Task.h"

    #if !defined (ACE_LACKS_PRAGMA_ONCE)
    # pragma once
    #endif /* ACE_LACKS_PRAGMA_ONCE */

    /* A typical ACE_Task<> derivative that adds a few things appropriate
       to protocol stacks.  To keep things a little simpler, we prevent
       activation of the task and just borrow the thread of control from
       the calling method in all cases.
    */
    class Protocol_Task : public ACE_Task<ACE_MT_SYNCH>
    {
    public:
      typedef ACE_Task<ACE_MT_SYNCH> inherited;

      Protocol_Task (void);

      ~Protocol_Task (void);

      // open() is invoked when the task is inserted into the stream.
      virtual int open (void *arg);

      // close() is invoked when the stream is closed (flags will be set
      // to '1') and when the svc() method exits (flags will be '0').
      virtual int close (u_long flags);

      // As data travels through the stream, the put() method of each task
      // is invoked to keep the data moving along.
      virtual int put (ACE_Message_Block *message,
                       ACE_Time_Value *timeout);

      // We're obligated to provide this signature even though we won't be
      // allowing this object to be activated.
      virtual int svc (void);

    protected:

      // Called by put() or svc() as necessary to process a block of data.
      int process (ACE_Message_Block *message,
                   ACE_Time_Value *timeout);

      // Tasks on the writer (downstream) side of the stream are called
      // upon to send() data that will ultimately go to the peer.
      virtual int send (ACE_Message_Block *message,
                        ACE_Time_Value *timeout);

      // Tasks on the reader (upstream) side will be receiving data that
      // came from the peer.
      virtual int recv (ACE_Message_Block *message,
                        ACE_Time_Value *timeout);

    };

    #endif /* PROTOCOL_TASK_H */

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