On 08/31/2004 08:43 PM, Carlo Wood wrote:
On Tue, Aug 31, 2004 at 06:41:36PM -0500, Larry Evans wrote:
I haven't thought deeply about this, but could this message idea and stack of streambuf's be used to implement a part of the upper layers of the OSI model:
http://www.geocities.com/SiliconValley/Monitor/3131/ne/osimodel.html
Well, the idea coming from my work on libcw ... one description of libcw is "An Object Oriented C++ library for networking applications", so yes - the whole idea has always been to be a general though efficient method to deal with networking protocols (the top layer of OSI).
? For example, each layer would correspond to an element in the stack of streambufs, and each streambuf could have a state associated with it. For example, the state could be a complex fsm, as with TCP:
You lost me here. stack elements of streambufs are not related to OSI layers (which even include the hardware?! A horse != cow).
Well, I figured it could be used in the lower layers (the hardware) for that reason, but I figured it might be usable in the higher layers.
Also, I talked about 'messages' (chunks of data) and not about stacked streambufs; mulitple streambufs means copying of data and I am trying
Well, streambufs deal with characters, either wide or regular, depending on a template parameter, I guess. Why couldn't the template parameter indicate a message (a chunk of data) instead of a single character. If you look at: http://cvs.sourceforge.net/viewcvs.py/boost-sandbox/boost-sandbox/boost/io/f... again, you'll see the template parameter is called "Fluid" :) . So I was thinking that maybe, in the case of characters, the fluid would be char or wchar, but in your case, the fluid would be messages.
to talk Jonathan out of that :p. Finally, a TCP statemachine is an ISO layer lower - and a statemachine that would decode a specific protocol would be a layer higher then my 'Message' objects.
OK. Maybe I'm thinking more in the line of a parser which gather's lower level data, chars, into higher level structures (AST nodes), and comparing that to network layers which gather lower level data (TCP/IP) and transform (filter it) into higher level data (whatever the application layer uses), and also does the reverse. In other words, somewhat like Jonathan's dual-use streambufs. I realize this is way beyond what Jonathan had in mind, but I just couldn't help speculating.
indicate the width of the current margin. An example of a streambuf with such a simple state is:
http://cvs.sourceforge.net/viewcvs.py/boost-sandbox/boost-sandbox/boost/io/f...
There is no streambuf on that page.
Sorry. See: http://cvs.sourceforge.net/viewcvs.py/boost-sandbox/boost-sandbox/boost/io/f... for how that class in combination with opipeline_from_streambuf is used to create a filtered stream. I can't remember exactly where the streambuf is created, but I believe it doesn't use any buffers other than that already in the sink.