ACE Tutorial 015

ACE Tutorial 015 Building a protocol stream

The Protocol_Task implementation takes care of the open(), close(), put() and svc() methods so that derivatives can concentrate on the send() and recv() methods. After a while you find that most ACE_Task<> derivatives look very similar in the four basic methods and only need one or two additional to do any real work.


// page13.html,v 1.16 2003/08/19 15:08:26 schmidt Exp

#include "Protocol_Task.h"
#include "ace/ACE.h"

// Construct the object and remember the thread count.
Protocol_Task::Protocol_Task(void)
{
    ;
}

Protocol_Task::~Protocol_Task(void)
{
    ;
}

int Protocol_Task::open(void *arg)
{
  ACE_UNUSED_ARG(arg);

  return(0);
}

int Protocol_Task::close(u_long flags)
{
    ACE_UNUSED_ARG(flags);
    return 0;
}

/* When a message is put() onto the task, it's time to process() some data.
*/
int Protocol_Task::put(ACE_Message_Block *message,ACE_Time_Value *timeout)
{
    return this->process(message,timeout);
}

/* Return an error since we don't want the task to ever be activated.
 */
int Protocol_Task::svc(void)
{
    return -1;
}

/* There's nothing really magic about process().  We just decide if
   we're moving data upstream or downstream and invoke the appropriate
   virtual function to handle it.
*/
int Protocol_Task::process(ACE_Message_Block * message, ACE_Time_Value *timeout)
{
    if( this->is_writer() )
    {
        return this->send(message,timeout);
    }

    return this->recv(message,timeout);
}

/* We must insist that derivatives provide a meaningful overload for
   these methods.  It's fairly common for ACE object methods to return
   an error when an overload is expected but the method cannot be
   safely made pure virtual.
 */

int Protocol_Task::send(ACE_Message_Block *message,
                        ACE_Time_Value *timeout)
{
    ACE_UNUSED_ARG(message);
    ACE_UNUSED_ARG(timeout);
    return -1;
}

int Protocol_Task::recv(ACE_Message_Block * message,
                        ACE_Time_Value *timeout)
{
    ACE_UNUSED_ARG(message);
    ACE_UNUSED_ARG(timeout);
    return -1;
}

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