Saturday, 21 February 2009

Fibers, at last!

As I'm recently doing Windows programming again after some 10 years of a pause, I keep learning about new things. One of them are fibers. Come again? What's that??

A fiber, as the name implies, is a piece of a thread. More precisely, a fiber is a unit of execution within a thread that can be scheduled by the application rather than by the kernel. *

So fibers are just user space threads, aka cooperative multitasking, which I knew since the stone-age DOS times and which weren't supposed to be cool at all!

It were native kernel threads which were supposed to be cool back then! But I must admit that in the past as I was working with cooperative multitasking in a rather big, multithreading system, I was quite happy with it! It gave a nice, predicatble feel to the system; you just new at what times what threads are supposed to run! The sole problem was (of course) that a long running user task couls block all the system. But then we moved on to native threads and I forgot about cooperative multitasking.

But something has changed since then: first, as it was already said, Windows has got it, although allegedly only as a good-enough implementation to support the SQL-Server (fibers have severe restrictions on the kinds of Win32 API’s they can call!). Second, Oracle 10g has got it too, I cite**:

Fiber model support
- An extension of the thread support already in place since Oracle7. Users may now run the database in fiber mode, which employs Oracle-scheduled fibers instead of O/S scheduled threads.
- For CPU intensive apps, this will provide a performance boost and reduce CPU utilization.

Moreover, recently I discovered a fiber library for Windows XP to remedy the unsufficient native Windows fibers support named FiberPool***. And then there are Green Threads (user space level, cooperative multitasking threads) in Java's JVM for some time now! The recent Windows 7 beta has introduced User Mode Scheduled Threads (UMS Threads)**** , which are like Win32 Fibers, as they can be scheduled by hand, but are backed by real bona-fide kernel level threads! Sounds rather interesting!

So at last it's the old, good cooperative mutitasking rediscovered? There's a growing evidence! Will be the ol' good times of DSET maybe back then Stefan?

* Johnson M. Hart: Windows System Programming Third Edition, Addison Wesley 2004

Wednesday, 18 February 2009

C++ Server Pages

In my prevoius blogs I wondered if there is/could be a C++ implementation of the Java's Servlet interface(s)*, and recently a friendly fellow blogger** pointed out to me that there already is one, viz the CPPSERV:!

Can you see C++ it its logo?

I cite*:

CPPSERV is a web application server that provides Servlet-like API and JSP-like functionality to C++ programmers.
CSP (C++ Server pages), the JSP equivalent for CPPSERV, are currently implemented as a precompiler that converts CSP source to C++ source of a servlet, which, in turn needs to be compiled into CPPSERV servlet
Current CSP implementation supports basic parsing, as well as compile-time taglibs.

Well, that's it! Or perhaps not? What we have is the equivalent of the Java's JSPs, which generally suck, and standing alone are too week a framework for serious work. But hey, it's not that bad, as we have got some choices: the CPPSERV for the oldskool JSP-like programming, the late Bobcat for more of the same, or the Wt framework*** for more modern, GWT-like work!

And with some discipline (I mean the model 1 ;-))) servlets, do you remember???) it's possible to get working application in C++ quickly! And all that Java frameworks out there are only trying to hide the JSP processing model, and they aren't that beautiful themselves. So for smaller things a JSP-like solution will be probably sufficient, and for more modern applications (including AJAX support) I'd choose the Wt framework.

There remains the question of the OO-Relational mapping, an the creators of CPPSERV suggest using their SPTK classes****, but it seems to be only a JDBC-like DB access layer. I suppose, I'd rather take Qt's DB classes for that, but on the other side, they are somehow heavyweight. But the OO-Relational thing for C++ is a different question in itself. But JDBC style access isn't that horrible either, and in a whole I think there are some viable options for C++ web applications out there!

Now I guess, I should try out the 2 frameworks, but ... ehm ... you know, so little time, so many books...

PS (07 Oct. 2009): meanwhile I have detected two another C++ and C "Servlets". Well they aren't really Servlets, but are rather one step back on the evolutionary path, and are somehow JSP-equivalent. The first of them is named KLone and allows you to include C scripts in the HTML page in the exact JSP manner. The other is GWAN - it's free and it allows you to write "servlet" scripts in C, which will be executed by the server and generate the HTML output - so in this case we are almost there, except for the very limited set of functions you can use in the script. Nonetheless, very interesting!

* see:
** Gavino, unfortunately his profile isn't available :-(((, but nonetheless, thanks bloke!
*** The Wt-framework ("witty" -
**** SPTK: mainly a GUI framework, but it has some DB access support as well: