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<HTML>
<HEAD>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<META NAME="Author" CONTENT="Bob McWhirter">
<TITLE>ACE Tutorial 014</TITLE>
</HEAD>
<BODY TEXT="#000000" BGCOLOR="#FFFFFF" LINK="#000FFF" VLINK="#FF0F0F">
<CENTER><B><FONT SIZE=+2>ACE Tutorial 014</FONT></B></CENTER>
<CENTER><B><FONT SIZE=+2>ACE_Stream Tutorial, Of Sorts</FONT></B></CENTER>
<P>
<HR WIDTH="100%">
<P>
As stated in the comments below, the default action of the task at the
stream tail is to treat any received data as an error. In our
implementation it will often happen that data gets through to
the tail. How, then, do we handle this without creating an
error condition? Simple: Create a custom Task for use as the
stream tail that doesn't consider it an error to receive data.
<P>
Read on...
<P>
<HR WIDTH="100%"><PRE>
// $Id$
// EndTask.h
//
// Tutorial regarding a way to use ACE_Stream.
//
// written by bob mcwhirter (bob@netwrench.com)
//
//
#ifndef ENDTASK_H
#define ENDTASK_H
#include "Task.h"
// When you setup a Stream and push your modules on,
// there are two additional modules that go unseen
// by the user.
//
// The Stream pushes on a Stream_Head in front of
// your first module, and a Stream_Tail behind your
// last module.
//
// If your put() a message to the Stream Tail, it
// assumes you did so in error. This simple EndTask
// class allows you to push a message to it and just
// have it safely Go Away.
//
// All this Task does is release the Message_Block
// and return 0. It's a suitable black-hole.
class EndTask : public Task
{
public:
typedef Task inherited;
EndTask(const char *nameOfTask) :
inherited(nameOfTask, 0) {
// when we get open()'d, it with 0 threads
// since there is actually no processing to do.
cerr << __LINE__ << " " << __FILE__ << endl;
};
virtual int open(void *)
{
cerr << __LINE__ << " " << __FILE__ << endl;
return 0;
}
virtual int open(void)
{
cerr << __LINE__ << " " << __FILE__ << endl;
return 0;
}
virtual ~EndTask(void) {
};
virtual int put(ACE_Message_Block *message,
ACE_Time_Value *timeout) {
cerr << __LINE__ << " " << __FILE__ << endl;
ACE_UNUSED_ARG(timeout);
// we don't have anything to do, so
// release() the message.
ACE_DEBUG ((LM_DEBUG, "(%P|%t) %s EndTask::put() -- releasing Message_Block\n", this->nameOfTask()));
message->release();
return 0;
};
};
#endif // ENDTASK_H
</PRE>
<P><HR WIDTH="100%">
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