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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> "<A HREF="../../../ace/Svc_Handler.h">ace/Svc_Handler.h</A>"
<font color=blue>#if !defined</font> (<font color=purple>ACE_LACKS_PRAGMA_ONCE</font>)
<font color=blue># pragma</font> <font color=purple>once</font>
<font color=blue>#endif</font> <font color=red>/* ACE_LACKS_PRAGMA_ONCE */</font>
<font color=blue>#include</font> "<A HREF="../../../ace/SOCK_Stream.h">ace/SOCK_Stream.h</A>"
<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 client</font>
<font color=red>// connection.</font>
int open (void *);
<font color=red>// Called when it's time for us to be deleted. We take care of</font>
<font color=red>// removing ourselves from the reactor and shutting down the peer()</font>
<font color=red>// 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 use</font>
<font color=red>// 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 code.</font>
<font color=red>// That's our signal that it's time to begin the 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 requirements.</font>
<font color=red>// We use a local Protocol_Stream object to take care of those</font>
<font color=red>// details. For us, I/O then just becomes a matter of interacting</font>
<font color=red>// 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>
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