ACE Tutorial 015
Building a protocol stream


And now the implementation of the Protocol_Stream. There are more lines of code here than we've seen so far but it still isn't complicated. The basic idea is to construct the ACE_Stream with our set of protocol objects that will manipulate the data. Our primary concern in this file is to get everything in the correct order!

// $Id: page12.html,v 1.4 1998/10/27 19:05:55 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.
*/
class Protocol_Task : public ACE_Task<ACE_MT_SYNCH>
{
public:

    typedef ACE_Task<ACE_MT_SYNCH> inherited;

        // A choice of concurrency strategies is offered by the
        // constructor.  In most cases it makes sense to set this to
        // zero and let things proceed serially.  You might have a
        // need, however, for some of your tasks to have their own thread.
    Protocol_Task( int _thr_count );

    ~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);

        // If you choose to activate the task then this method will be
        // doing all of the work.
    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);

        // Just let us know if we're active or not.
    int is_active(void)
        {
            return this->thr_count() != 0;
        }

        // Tasks on the writter (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);

private:
    int desired_thr_count_;
};

#endif // PROTOCOL_TASK_H


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