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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%">
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!
<HR>
<PRE>
<font color=red>// $Id$</font>
<font color=blue>#include</font> "<font color=green>Protocol_Stream.h</font>"
<font color=blue>#include</font> "<font color=green>Protocol_Task.h</font>"
<font color=blue>#include</font> "<font color=green>Xmit.h</font>"
<font color=blue>#include</font> "<font color=green>Recv.h</font>"
<font color=blue>#include</font> "<font color=green>Compressor.h</font>"
<font color=blue>#include</font> "<font color=green>Crypt.h</font>"
<font color=blue>#include</font> "<font color=green>ace/Stream_Modules.h</font>"
<font color=red>/* You can choose at compile time to include/exclude the protocol
pieces.
*/</font>
<font color=blue>#define</font> <font color=purple>ENABLE_COMPRESSION</font>
<font color=blue>#define</font> <font color=purple>ENABLE_ENCRYPTION</font>
<font color=red>// The usual typedefs to make things easier to type.</font>
typedef ACE_Module<ACE_MT_SYNCH> Module;
typedef ACE_Thru_Task<ACE_MT_SYNCH> Thru_Task;
<font color=red>/* Do-nothing constructor and destructor
*/</font>
<font color=#008888>Protocol_Stream::Protocol_Stream</font>( void )
{
;
}
<font color=#008888>Protocol_Stream::~Protocol_Stream</font>( void )
{
;
}
<font color=red>/* Even opening the stream is rather simple. The important thing to
rememer is that the modules you push onto the stream first will be
at the tail (eg -- most downstream) end of things when you're
done.
*/</font>
int <font color=#008888>Protocol_Stream::open</font>( ACE_SOCK_Stream & _peer, Protocol_Task * _reader )
{
<font color=red>// Initialize our peer() to read/write the socket we're given</font>
peer_.set_handle( _peer.get_handle() );
<font color=red>// Construct (and remember) the Recv object so that we can</font>
<font color=red>// read from the peer().</font>
recv_ = new Recv( peer() );
<font color=red>// Add the transmit and receive tasks to the head of the</font>
<font color=red>// stream. As we add more modules these will get pushed</font>
<font color=red>// downstream and end up nearest the tail by the time we're</font>
<font color=red>// done.</font>
if( stream().push( new Module( "<font color=green>Xmit/Recv</font>", new Xmit( peer() ), recv_ ) ) == -1 )
{
ACE_ERROR_RETURN ((LM_ERROR, "<font color=green>%p\n</font>", "<font color=green>stream().push( xmit/recv )</font>"), -1);
}
<font color=red>// Add any other protocol tasks to the stream. Each one is</font>
<font color=red>// added at the head. The net result is that Xmit/Recv are at </font>
<font color=red>// the tail.</font>
if( this->open() == -1 )
{
return(-1);
}
<font color=red>// If a reader task was provided then push that in as the</font>
<font color=red>// upstream side of the next-to-head module. Any data read</font>
<font color=red>// from the peer() will be sent through here last. Server</font>
<font color=red>// applications will typically use this task to do the actual</font>
<font color=red>// processing of data.</font>
<font color=red>// Note the use of Thru_Task. Since a module must always have </font>
<font color=red>// a pair of tasks we use this on the writter side as a no-op.</font>
if( _reader )
{
if( stream().push( new Module( "<font color=green>Reader</font>", new Thru_Task(), _reader ) ) == -1 )
{
ACE_ERROR_RETURN ((LM_ERROR, "<font color=green>%p\n</font>", "<font color=green>stream().push( reader )</font>"), -1);
}
}
return(0);
}
<font color=red>/* Add the necessary protocol objects to the stream. The way we're
pushing things on we will encrypt the data before compressing it.
*/</font>
int <font color=#008888>Protocol_Stream::open</font>(void)
{
<font color=blue>#if defined</font>(<font color=purple>ENABLE_COMPRESSION</font>)
if( stream().push( new Module( "<font color=green>compress</font>", new Compressor(), new Compressor() ) ) == -1 )
{
ACE_ERROR_RETURN ((LM_ERROR, "<font color=green>%p\n</font>", "<font color=green>stream().push( comprssor )</font>"), -1);
}
<font color=blue>#endif</font> <font color=red>// ENABLE_COMPRESSION</font>
<font color=blue>#if defined</font>(<font color=purple>ENABLE_ENCRYPTION</font>)
if( stream().push( new Module( "<font color=green>crypt</font>", new Crypt(), new Crypt() ) ) == -1 )
{
ACE_ERROR_RETURN ((LM_ERROR, "<font color=green>%p\n</font>", "<font color=green>stream().push( crypt )</font>"), -1);
}
<font color=blue>#endif</font> <font color=red>// ENABLE_ENCRYPTION</font>
return( 0 );
}
<font color=red>// Closing the Protocol_Stream is as simple as closing the ACE_Stream.</font>
int <font color=#008888>Protocol_Stream::close</font>(void)
{
return stream().close();
}
<font color=red>// Simply pass the data directly to the ACE_Stream.</font>
int <font color=#008888>Protocol_Stream::put</font>(ACE_Message_Block * & _message, ACE_Time_Value * _timeout )
{
return stream().put(_message,_timeout);
}
<font color=red>/* Tell the Recv module to read some data from the peer and pass it
upstream. Servers will typically use this method in a
handle_input() method to tell the stream to get a client's request.
*/</font>
int <font color=#008888>Protocol_Stream::get</font>(void)
{
<font color=red>// If there is no Recv module, we're in big trouble!</font>
if( ! recv_ )
{
ACE_ERROR_RETURN ((LM_ERROR, "<font color=green>(%P|%t) No Recv object!\n</font>"), -1);
}
<font color=red>// This tells the Recv module to go to it's peer() and read</font>
<font color=red>// some data. Once read, that data will be pushed upstream.</font>
<font color=red>// If there is a reader object then it will have a chance to</font>
<font color=red>// process the data. If not, the received data will be</font>
<font color=red>// available in the message queue of the stream head's reader</font>
<font color=red>// object (eg -- stream().head()->reader()->msg_queue()) and</font>
<font color=red>// can be read with our other get() method below.</font>
if( recv_->get() == -1 )
{
ACE_ERROR_RETURN ((LM_ERROR, "<font color=green>(%P|%t) Cannot queue read request\n</font>"), -1);
}
<font color=red>// For flexibility I've added an error() method to tell us if</font>
<font color=red>// something bad has happened to the Recv object.</font>
if( recv_->error() )
{
ACE_ERROR_RETURN ((LM_ERROR, "<font color=green>(%P|%t) Recv object error!\n</font>"), -1);
}
return(0);
}
<font color=red>/* Take a message block off of the stream head reader's message
queue. If the queue is empty, use get() to read from the peer.
This is most often used by client applications. Servers will
generaly insert a reader that will prevent the data from getting
all the way upstream to the head.
*/</font>
int <font color=#008888>Protocol_Stream::get</font>(ACE_Message_Block * & _response, ACE_Time_Value * _timeout )
{
if( stream().head()->reader()->msg_queue()->is_empty() )
{
if( this->get() == -1 )
{
ACE_ERROR_RETURN ((LM_ERROR, "<font color=green>(%P|%t) Cannot get data into the stream.\n</font>"), -1);
}
}
return stream().head()->reader()->getq(_response,_timeout);
}
</PRE>
<P><HR WIDTH="100%">
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