28 Feb

An Alternative to XML

My new weapon of choice. libconfig is a configuration file parser that supports arrays, named and typed members, selection by path (e.g. cfg.users.[3].name) and more. That is, it has basically all the useful (as in 80% of cases) features of XML and none of the bad. There’s a minimal but well defined structure that will work for most situations and that can be used to enforce e.g. all array items having to be of the same type. There’s no overkill markup so it’s easy to read and write by humans. The library can also write the settings tree into a text file.

The configuration files look like this:

screen = { width = 300; height = 200; }
users = ( { name = "Torgo"; items = [ "Item 1", "Item 2" ]; } );

And in C you would do something like this:

int screen_height = 100;
const char *name;
config_read_file(&cfg, "config");
if (!config_lookup_int(&cfg, "screen.height", &screen_height))
  puts("Using default screen height");
if (config_lookup_string(&cfg, "users.[0].name", &name))

You can also iterate the setting tree without the path for easier array or tree traversal. In all, I would say it involves less work compared to any XML library, especially in C. I like to think it’s a good example of software designed by the same guy who also uses it and not by some external committee.

22 Sep

Introducing My Latest Projects

… Or, How to Procrastinate Productively.


I decided to make one of my current projects open source and post them on Google Code just for fun. The project is a tool chain that I’m using to remake Thrust. In reality, I decided to divide the project into two separate projects: the actual game engine (called klystron) and related tools, and a music editor that uses the engine.

Here are two videos I made a while ago that demonstrate the engine. The first is the music editor (called klystrack) — it’s much less ugly at the moment but the sound synthesis is the same, and that’s what matters:

The sound engine (“Cyd”) is basically a very simple software synthesizer with capabilities comparable to the SID or any 8-bit machine from the 80s. The editor is a fairly standard tracker, much like GoatTracker.

The graphics half of the engine is basically a wrapper around a quite fast collision detection system (pixel-accurate, or it wouldn’t be much good for a thrustlike) built on SDL. It also does background collisions and drawing as well. As you may have guessed, the whole point is to provide a limited but still helpful set of routines that are useful for creating 2D games not unlike what video games were in 1991.

And, here’s a proof I’m actually working on the actual game (the sound effects are created in real time by the sound engine):

A note on Google Code: it’s rather nice. It provides the standard open source development stuff like source control an such but I really like how clean and hassle-free it is. Adding a project takes a minute and after that it’s simply coding and some quick documentation on the project wiki. The project wiki is good example of how simple but elegant the system is: the wiki pages actually exists inside the source control as files, just like your source code.

Go check Google Code out and while you’re at it, contribute on my projects. :)

24 Feb

Google Chart API is pretty cool

I just stumbled upon the Google Chart API and I couldn’t resist playing with it (statistics being a fetish of mine). A few moments later, I came up with some PHP code that uses my stats plugin for WordPress to fetch page views and generates an URL for the Google API (see below for the attached source code).

The main idea behind Google Chart is that the chart is an image and all data for the chart is in the URL. That includes the chart title, size and the data sets. Personally, I think this is a brilliant idea. You can embed the charts anywhere you can use images and best of all, you don’t need to have data anywhere else but in the URL (you don’t even need to duplicate the generated image in your own webspace).
You can also pretty much generate charts by hand if needed.

On the other hand, when using dynamic data fetched from a database, it is a relatively small task to encode the data into the format Google Chart uses. They even provide a Javascript snippet for that (obviously, you might want to do that server-side – see below). Or, you can simply use floating point numbers if you don’t mind long URLs (and I’m not even sure you can always use very long URLs).

For example, below there’s a graph generated from daily visits to this site:

And here is the URL used to get that graph (lines split for convenience):


The above URL has quite Google-like short parameter names but that’s obviously because of technical limitations. The chd parameter is where the data set for the graph is: s:NQGHJsimple encoding : encoded data.

One interesting aspect arises because of the encoding: you need to fit your data set to use the granularity the encoding has. E.g. when using simple encoding and encoding a data set of 0, 4.7 and 244, you have to normalize and remap the data so the data goes from 0 (character A) to 61 (character 9), not from 0 to 244. That may sound horribly inaccurate but remember, nobody measures the charts with a ruler – they look at the numbers for accurate data. And there are more accurate encodings.

I like how the charts look slick. A lot of existing libraries and APIs for similar stuff tend to have less aesthetic appeal. Anti-aliasing does not better stats make but it certainly looks more professional. The API also has nice features such as adding arrows and red X’es on a graph (think an arrow with the caption “stock market crash” – after which the graph plummets), the always useful Venn diagrams (see right) and other usual stuff you’d need.

Anyway, my original point was that Chart is a cool API, is probably easier to use and faster to install than gnuplot or other chart drawing software, is compatible with any browser able to display images and it’s free for everyone to use (the limit is something like 50 thousand views per user per day – and I guess their policy says nothing against caching the charts on your own site). Check it out.

P.S. This is quite obvious but… I predict that in the future, Google will use the accumulated charts for some kind of statistics search. The charts contain text (label, title) so a Google search result might include relevantly labeled graphs. Which is an interesting scenario, considering the Internet is full of lies, kooks and gullible users.