Ming-Lun "Allen" Chou

There are already lots of well-known and popular libraries out there that provide mutices. But I wanted to try implementing it myself for the sake of just making it. Hey, it’s summer session at DigiPen and I don’t have to work on any school game projects. This means I can do whatever programming exercise I want during this time

My implementation relies on “Windows.h”, which already provides mutex objects. But hey, it’s summer session! Besides, I actually find my interface design more intuitive and easier to use, so I might end up using it in my next game project.

Below is the interface for the Mutex class. It has a default constructor, a copy constructor and a destructor. It also has an assignment operator. Finally, it defines the very two operations a mutex object has: lock and unlock.

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I introduced how to build your own C++ delegates in the previous post. Now I’m going to show you the first practical (and probably the most common) usage of delegates: signal/event systems.

To clarify the terminology, the mapping between the system I’m going to show here and the terms in the Observer Pattern is as follows: a signal object is a subject object, and a delegate that listens to a signal object is an obeserver object that observes a subject object. The basic idea here is that the listeners that are interested in a specific signal object get invoked when the signal object dispatches. This is a very useful pattern in engine design, which can be used to eliminate busy waiting conditions, because the observers are informed passively as opposed to actively querying the subject for new information (this can be wasting CPU cycles if there is no actual data update).

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My second semester at DigiPen has almost come to an end. For the project of this semester, we are required to write our code in strict C, no fancy C++ stuff like generics and polymorphism. In order to get around this limitation, our team used a technique described in this post to mimic object-orientation in C.

I’m planning on starting building our team’s new game engine early in this summer to prepare for the upcoming fall semester. This time, of course, we’re allowed to write code in C++.

The first thing I’m planning on building is the event system, which is basically a framework with event dispatchers and event listener functions. But things turned out to be more complicated than I thought. In ActionScript, Java, and C#, the only functions we can define are strictly member functions, functions that are defined in a class body. Even the “main” function is simply the constructor of a document class or a public static void function inside a class. So we don’t have to worry about whether an event listener function is a member function or not.

In C++, however, not everything is object-oriented. A function can be an ordinary function defined in global scope or a member function defined in a class (or struct) body. The invocation to both types of functions are different, so we cannot treat them as equal: we cannot assign them to the same type of function pointer. But I want to treat them equally, so that I can register ordinary functions and member functions of the same signature to the same event dispatcher. This leads me to the research of function delegates.

For now, I’m just going to discuss the fundamental difference between ordinary functions and member functions. I’m also going to point out the difference between function pointers versus member function pointers.

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