Saturday, July 2, 2011

Crappy week

Caught a cold during the weekend, and I just couldn't get anything done during the week. A few late nights didn't help, either. So, I managed to look at event handling a bit, got some promising ideas, but that's not what I'll be working on just now.

I am going to, instead, work a little more on the resources, wrap that up for now, then move on. I had a few interesting thoughts before, and then someone pointed out that keeping a pointer and a count of times it's been referenced is a lot like having a smart pointer. Boost offers a number of them, of which 'shared_ptr' seemed to be the most appropriate. The way they work is that, so long as I refrain from using regular pointers, I should not have dangling pointers (pointers aimed at a resource I already freed) because the pointers share a counter themselves. Only once all references to a memory address have been lost is the memory freed.

So what I'll do is, when reading a file, create a resource and point to it with a shared pointer. I then store the shared pointer in a map, and key it to a string value (for now, just the name of the file). Then I can have anyone who needs it get a copy of the shared pointer, and keep track of how many people hold pointers to each value. Then instead of using handles to get a pointer (which I didn't do to avoid the problems with naked pointers in the first place), I can use the smart pointer itself.

For now I'll give the cache limited functionality. It can load a pointer, given a string to key it with, and it can produce the pointer, given the key. The other cool thing about smart pointers is that I don't need to worry so much about erasing things just yet. Not only do they not erase the resource until it's not needed by the last reference, but when the last reference to it dies one way or another, it is deleted automatically as well. So no memory leaks. Of course, since the cache holds a reference, the resources won't be freed unless I specifically say so.

The matter of reading a file is still something I'm struggling with. There are several ways of going about it. I'll do the more flexible one for now, and consider how to refactor the code later. What I'll be doing is storing all the code for turning files into resources in one class, the caches to store the resources as another class, and the code to call them in the framework class that holds them both.

There, back in business. And hey, these changes don't even require that I change (too much) my previous code! The file reading code just needs to be updated to provide shared pointers instead of naked pointers. So I should be able to test that the changes don't break anything easily enough.

Anyway, it's been too long without any pretty drawings, so I'm going to be delving into some stuff way off in the future in the next few posts, while I silently toil at the boring backbone stuff.

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