David Cumps

Design Patterns - Decorator Pattern

CumpsD — Sun, 29 Jun 2008 19:42:00 GMT

Following up on the Observer/Event Pattern, it’s time for the third pattern, the Decorator Pattern.

The definition: "Attach additional responsibilities to an object dynamically. Decorators provide a flexible alternative to subclassing for extending functionality."

Design Patterns - Observer/Event Pattern

CumpsD — Fri, 27 Jun 2008 15:16:00 GMT

Yesterday I described the Observer Pattern and mentioned that the .NET CLR provides this functionality through events and delegates.

Let’s have a look on how to implement this right now.

Design Patterns - Observer Pattern

CumpsD — Thu, 26 Jun 2008 19:21:00 GMT

Yesterday we saw the Strategy Pattern. Today I want to talk about the Observer Pattern.

First, the definition again: "Define a one-to-many dependency between objects so that when one object changes state, all its dependents are notified and updated automatically."

Design Patterns - Strategy Pattern

CumpsD — Wed, 25 Jun 2008 11:50:00 GMT

The first pattern I want to talk about is the Strategy pattern, which always reminds me about the Command & Conquer games so I’ll simply use it as an example :)

First of all, the definition: "Define a family of algorithms, encapsulate each one, and make them interchangeable. Strategy lets the algorithm vary independently from clients that use it."

I’m bad at remembering definitions or trying to imagine what they really mean, so let’s just go ahead and try to create something and learn as we go, eventually we’ll end up implementing the Strategy pattern and you’ll 'get it' for the rest of your life, without a definition.

Obfuscation - Making Reverse Engineering Harder

CumpsD — Sat, 29 Sep 2007 15:51:00 GMT

In a previous article I have demonstrated how easy it is to decompile and reverse engineer .NET assemblies using Reflector and Reflexil. I've also shown that applying a strong name to your assembly does not protect your code from reverse engineering. So, what else is left?

A technique called obfuscating goes a long way in keeping your source code safe. An obfuscator will mangle your code, without changing the actual result, to make it increasingly harder for someone to decompile your code and actually understand it.

Party Game Guitar Hero for PC

CumpsD — Sat, 22 Sep 2007 22:35:00 GMT

Ever heard of the very popular game for the PlayStation 2, called Guitar Hero? Until recently, I only vaguely picked it up here and there, but not being a big PlayStation gamer, I never payed much attention. That is, until today. A friend of mine gave me a link to Frets On Fire, which claims to be the PC variant of Guitar Hero. Seeing it was free, I downloaded it and gave it a try, and I have to admit, it's addictive!

Allow me to give you a small introduction on this game.

Efficient Compound Index Usage

CumpsD — Thu, 20 Sep 2007 09:57:00 GMT

Today I was made aware by Filip, a colleague of mine, about the importance of columns used in a where clause with a compound index. I decided to investigate this a bit more in detail, with proper profiling and comparisons on a large data set.

String Concatenation vs Memory Allocation

CumpsD — Sun, 16 Sep 2007 17:37:00 GMT

Over the years, plenty has been written about string performance, lots of comparisons between String.Concat and StringBuilder. Today I decided to do some of my own research into the subject and contribute to the knowledge already out there. More specifically, I'll be taking a look at the memory usage for various concatenation methods and compiler optimizations used to generate the IL.

The test scenario I defined consists out of several methods, each returning the same string. The string I created is supposed to resemble a real-life scenario. I identified five different ways of concatenating strings for my test. I will be taking a look at the numbers when calling each method once and inside a very small loop of 50 calls, which is another real-life number in my case.

Code Signing as Reverse Engineering Protection

CumpsD — Sat, 15 Sep 2007 21:29:00 GMT

In my last post I spoke about reverse engineering .NET assemblies upon which Gregory asked how to protect his code against it.

Initially I thought signing an assembly would be the easiest way to prevent this, and my first tests confirmed this. I signed the CrackMe from my previous post and tried modifying it again, unsuccessfully.

But in the end Code Signing your assembly proved to be useless against reverse engineering.

Reverse Engineering with Reflector and Reflexil

CumpsD — Thu, 06 Sep 2007 21:32:00 GMT

I've always been a big fan of Reflector, allowing me to have a look in assemblies to learn new things, debug in case of problems and provide usefull information when creating bug reports. Combined with the Reflexil Add-in it's now easy to also modify assemblies yourself.

To demonstrate this, I've created a small CrackMe sample program, which consists out of nothing more then a simple password check. This is how it looks when opened in Reflector, with Reflexil displaying the IL code below it.

Open-Source Disk Encryption

CumpsD — Tue, 04 Sep 2007 19:06:00 GMT

Are you concerned about the confidentiality of your files? Take a look at TrueCrypt, a great tool to create encrypted volumes.

Temporary Break - Request for Subjects

CumpsD — Thu, 23 Aug 2007 21:37:00 GMT

After 21 days of posting something daily, I need a little break, for several reasons:

I 'm running out of subjects which I can use for short first-impressing posts. Please leave some comments with subjects you find interesting, perhaps I'll find them interesting as well! :)

Booting for Lazy People - Wake On LAN

CumpsD — Wed, 22 Aug 2007 22:05:00 GMT

Wake Up!

Not you... The computer!

Just had some fun enabling Wake On LAN on one of my computers. A great technology for the lazy people among us, you simply sit in your chair and realize you need to access some other computer in your house, but sadly enough it isn't powered on. The fit among us might simply walk to the machine and boot it, but I'd rather open up some program, hit a button and with some magic the machine starts up.

Explorer Bug, Long Path, damaged directories

CumpsD — Tue, 21 Aug 2007 22:06:00 GMT

Long ago, I found something strange in Windows Explorer, which I wanted to retry on Vista today.

In Explorer, first create a very big directory tree, consisting out of small directory names. Now, from the bottom, rename these directories to about 100 characters.

When you reached the top, try browsing the tree, after some directories it won't allow you to open the directory anymore. You can't select it, it will jump back, you can't rename that one, you can't delete the entire tree at once.

The Selfish Side of Social Bookmarking

CumpsD — Mon, 20 Aug 2007 22:05:00 GMT

Social bookmarking, one of the Web 2.0 hypes, allows you to share links with each other. This great video from Common Craft very clearly explains what social bookmarking is all about. While this is very useful, there’s also a selfish advantage to it.