In my living room, there's a TV, with a computer connected to it.
In that computer, there's a DVD-ROM player, a hard disk, and a card
with a TV output.
On that hard disk, there's
Debian with xine to view DVDs
When I originally put it there, I would pick up the keyboard to do
some user input. This works, but a keyboard is klunky. So, instead, I've
been working on jsxine, a little application that does not much more
than open a window, and tell xine to play a DVD there, but use the
joystick for UI[
1]. My 'joystick' is a
Logitech
Wingman Gamepad Extreme, which has a cable long enough for me to be able
to use it comfortably from the couch, so I can use it as a sort of
remote control.
The current version has quite some things hardcoded: button 0 is
'select', button 5 is 'eject', button 6 'previous chapter', button 7
'next chapter', and button 8 is 'start or stop playing'. The primary two
axes move around in the DVD menu; and other stuff is not yet
implemented. This layout, of course, makes a lot of sense on this
particular gamepad, but I doubt it does on other joystick devices. And
since I want this to eventually be useful for other people, too, I
recognized that I would need some way to configure things.
My initial stab at configuration would create a hash table of
available actions, read out a configuration file, and then find the
appropriate function pointer in the hash table. While this works, it has
one rather important downside: adding a configurable action would
requrie another item in the hash table; this would eventually make the
hash table horribly long. So I thought, why not use the configuration
value to ask the dynamic linker to get me a function pointer?
With a little help from
my
friends, that's exactly what I did. Proof-of-concept code:
#include <dlfcn.h>
#include <stdio.h>
int function()
printf("In function!\n");
int main(int argc, char**argv)
int (*funcptr)(void);
void* handle;
printf("foo\n");
handle = dlopen(NULL, RTLD_NOW);
funcptr = dlsym(handle, "function");
funcptr();
return 0;
Compile with
cc -ldl -rdynamic. Et voila, that gets you an
application which can do a lookup of function names at run time.
Long live C.
Of course, there's a bit of a danger in the above example. A
user could just write a config file that has things like 'open' and/or
'write' as arguments, or the like. One should make sure that it can be
obvious from the function name that it does indeed define an action; for
example, by giving them a common prefix, and prepending that prefix to
the function name before handing the name off to dlsym().
But other than that, this seems to work. It apparently also is
documented in the FreeBSD documentation on dlopen(), so maybe it's not
as much a hack as I thought...
Oh well.
Note that on GNU systems, you can also put a
#define
_GNU_SOURCE before the
#include <dlfcn.h>, you can
drop the
dlopen() call and go straight to dlsym(), with
RTLD_DEFAULT as the handle.
[1] Yes, I could have done a Xine
plugin. I didn't want to. This is as much a project to produce
something useful as it is a project to hack and have fun.
I've been talking serial consoles with a couple of the other guys at work:
how nice they are to have for machines in the datacenter, how annoying it
is that vPro
serial-over-LAN doesn't seem to be robust (yet?), and how serial
access concentrators are lung-and-kidney expensive (especially when you've
got 50-some racks to outfit).
This discussion, combined with my ongoing embedded-hardware-fascination
lust for a SheevaPlug
appears to have spurred my brain into coming up with a Brilliant Idea: tie
a SheevaPlug to a pile of USB to serial adapters and use that as your
per-rack serial concentrator. Imagine: faffenheimer, a dedicated server
you manage for a customer, and located in rack 27 of your DC, has just crashed, and
you'd like to know WTF has happened rather than just blindly reboot, but
you're in the office 15 minutes away from the DC floor, and the customer's
going to want that machine back up and running pretty quickly.
I visited Seoul last week to represent the Open Source Initiative (OSI) at
an open source conference and to sign a Memorandum of Understanding (MOU)
with the 
SOCOP is working on a number of activities related to open source,
including:
One really nice feature of maven is the dependency resolution stuff
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detect a number of problems with your dependencies. It can detect
libraries you use but haven't declared in your POM, but work through
transitive dependencies. This can cause build problems when you remove
the library that was dragging in the undeclared dependency. It can also
work out which dependencies you are no longer using, but have a declared
dependency.
I ve been working on a fun little project lately, trying to make a simple VoIP client which can be used on an Android device. It was fairly straightforward to port 
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I stumbled on a blog entry saying that 
A short review of Kleiber and Zeileis' excellent Applied Econometrics
with R is now out at the (online)
After I spent time working on 
And, as I suggested 
Go get the code at the