<!-- page10.html,v 1.16 2003/08/19 15:08:26 schmidt Exp --> <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 so finally we come to the Protocol_Stream. That, after all, is the focus of the entire tutorial but it took us half of the day to get here! <P> The Protocol_Stream uses an ACE_Stream to move an ACE_Message_Block through a series of tasks. Each task in the stream is responsible for performing some operation on the data in the message block. That is the nature of a protocol stream (or "stack" if you prefer). In this stream, the data is compressed and encrypted* on its way between peers. We also allow users of the stream to install a reader task to handle data that percolates up from the peer. As you saw a page or two ago, this is most useful for a server. <P> <font size=-1>*Again, I just pretend to do these things. It would take another day or two to go through any sort of reasonable encryption or compression!</font> <P> Before we get into the code, here's a picture that's shows what's going on here. <P><center><img src="stream.gif"></center></p> <HR> <PRE> <font color=red>// page10.html,v 1.16 2003/08/19 15:08:26 schmidt Exp</font> <font color=blue>#ifndef</font> <font color=purple>PROTOCOL_STREAM_H</font> <font color=blue>#define</font> <font color=purple>PROTOCOL_STREAM_H</font> <font color=blue>#include</font> "<A HREF="../../../ace/SOCK_Stream.h">ace/SOCK_Stream.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/Stream.h">ace/Stream.h</A>" <font color=red>// Shorthand for the stream.</font> typedef ACE_Stream<ACE_MT_SYNCH> Stream; <font color=red>// Forward references to cut down on the number of <font color=blue>#include</font>s</font> class ACE_Message_Block; class Recv; class Protocol_Task; <font color=red>/* The Protocol_Stream provides a tidy interface to an ACE_Stream setup to process a data block through a series of protocol stages. */</font> class Protocol_Stream { public: Protocol_Stream (void); ~Protocol_Stream (void); <font color=red>// Provide the stream with an ACE_SOCK_Stream on which it can</font> <font color=red>// communicate. If _reader is non-null, it will be added as the</font> <font color=red>// reader task just below the stream head so that it can process</font> <font color=red>// data read from the peer.</font> int open (ACE_SOCK_Stream &peer, Protocol_Task *reader = 0); <font color=red>// Close the stream. All of the tasks & modules will also be</font> <font color=red>// closed.</font> int close (void); <font color=red>// putting data onto the stream will pass it through all protocol</font> <font color=red>// levels and send it to the peer.</font> int put (ACE_Message_Block *&message, ACE_Time_Value *timeout = 0); <font color=red>// get will cause the Recv task (at the tail of the stream) to read</font> <font color=red>// some data from the peer and pass it upstream. The message block</font> <font color=red>// is then taken from the stream reader task's message queue.</font> int get (ACE_Message_Block *&response, ACE_Time_Value *timeout = 0); <font color=red>// Tell the Recv task to read some data and send it upstream. The</font> <font color=red>// data will pass through the protocol tasks and be queued into the</font> <font color=red>// stream head reader task's message queue. If you've installed a</font> <font color=red>// _reader in open() then that task's recv() method will see the</font> <font color=red>// message and may consume it instead of passing it to the stream</font> <font color=red>// head for queueing.</font> int get (void); ACE_SOCK_Stream &peer (void) { return this->peer_; } private: <font color=red>// Our peer connection</font> ACE_SOCK_Stream peer_; <font color=red>// The stream managing the various protocol tasks</font> Stream stream_; <font color=red>// A task which is capable of receiving data on a socket.</font> <font color=red>// Note that this is only useful by client-side applications.</font> Recv *recv_; Stream &stream (void) { return this->stream_; } <font color=red>// Install the protocol tasks into the stream.</font> int open (void); }; <font color=blue>#endif</font> <font color=red>/* PROTOCOL_STREAM_H */</font> </PRE> <P><HR WIDTH="100%"> <CENTER>[<A HREF="../online-tutorials.html">Tutorial Index</A>] [<A HREF="page11.html">Continue This Tutorial</A>]</CENTER>