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<HTML>
<HEAD>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<META NAME="Author" CONTENT="James CE Johnson">
<TITLE>ACE Tutorial 015</TITLE>
</HEAD>
<BODY TEXT="#000000" BGCOLOR="#FFFFFF" LINK="#000FFF" VLINK="#FF0F0F">
<CENTER><B><FONT SIZE=+2>ACE Tutorial 015</FONT></B></CENTER>
<CENTER><B><FONT SIZE=+2>Building a protocol stream</FONT></B></CENTER>
<P>
<HR WIDTH="100%">
The Handler object is our event handler. You can use either
ACE_Event_Handler or ACE_Svc_Handler<> for the baseclass. I generally
prefer the latter since it takes care of some housekeeping that I
would otherwise be responsible for.
<P>
The class declaration is taken almost exactly from a previous
tutorial. A good design will have a simple handler object that will
collect data from the peer and pass it along to another object for
processing. Again, keep it simple and delegate authority.
<HR>
<PRE>
<font color=red>// $Id$</font>
<font color=blue>#ifndef</font> <font color=purple>HANDLER_H</font>
<font color=blue>#define</font> <font color=purple>HANDLER_H</font>
<font color=blue>#include</font> "<font color=green>ace/Svc_Handler.h</font>"
<font color=blue>#if !defined</font> (<font color=purple>ACE_LACKS_PRAGMA_ONCE</font>)
# pragma once
<font color=blue>#endif</font> <font color=red>/* ACE_LACKS_PRAGMA_ONCE */</font>
<font color=blue>#include</font> "<font color=green>ace/SOCK_Stream.h</font>"
<font color=blue>#include</font> "<font color=green>Protocol_Stream.h</font>"
<font color=red>/* Just your basic event handler. We use ACE_Svc_Handler<> as a
baseclass so that it can maintain the peer() and other details for
us. We're not going to activate() this object, so we can get away
with the NULL synch choice.
*/</font>
class Handler : public ACE_Svc_Handler < ACE_SOCK_STREAM, ACE_NULL_SYNCH >
{
public:
Handler(void);
~Handler(void);
<font color=red>// Called by the acceptor when we're created in response to a</font>
<font color=red>// client connection.</font>
int open (void *);
<font color=red>// Called when it's time for us to be deleted. We take care</font>
<font color=red>// of removing ourselves from the reactor and shutting down</font>
<font color=red>// the peer() connectin.</font>
void destroy (void);
<font color=red>// Called when it's time for us to go away. There are subtle</font>
<font color=red>// differences between destroy() and close() so don't try to</font>
<font color=red>// use either for all cases.</font>
int close (u_long);
protected:
<font color=red>// Respond to peer() activity.</font>
int handle_input (ACE_HANDLE);
<font color=red>// This will be called when handle_input() returns a failure</font>
<font color=red>// code. That's our signal that it's time to begin the</font>
<font color=red>// shutdown process.</font>
int handle_close(ACE_HANDLE, ACE_Reactor_Mask _mask);
private:
<font color=red>// Like the Client, we have to abide by the protocol</font>
<font color=red>// requirements. We use a local Protocol_Stream object to</font>
<font color=red>// take care of those details. For us, I/O then just becomes</font>
<font color=red>// a matter of interacting with the stream.</font>
Protocol_Stream stream_;
Protocol_Stream & stream(void)
{
return this->stream_;
}
};
<font color=blue>#endif</font> <font color=red>// HANDLER_H</font>
</PRE>
<P><HR WIDTH="100%">
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