Early last month, I set out to add support for JSON into our game engine. To my surprise, it turned out to be a fun and rewarding adventure.
JSON is a very nice format that is fairly easy to parse. Its feature set is small and well defined, including:
- explicit values for null, true, and false
- numbers (integers and floating-point)
- strings
- arrays
- hash tables
This feature set is perfect for configuration files, stylesheets, etc. In the past, I have used XML for these sort of things, but JSON is much more direct and compact.
Initially, I reached for an external library to wrap, just as we have done for many of the other file formats we support, namely: PNG, XML, FBX, and OGG. Of course, when it comes to external libraries, your mileage will vary. For example, we use TinyXML 2, as the basis for our XML library; it was a real pleasure to use — a very straightforward, well designed interface. The FBX SDK, on the other hand, is pretty atrocious.
Unfortunately, I wasn’t very satisfied when it came to JSON. Many of the C++ JSON libraries out there make use of STL and/or Boost, dependencies we have striven to avoid. Eventually I settled on RapidJSON due to its high praise on the web; however, about half way through my wrapper implementation, I concluded that its interface is not as clean and “wrappable” as I had originally thought it to be.
After some reflection, I decided that the best way forward was to roll my own. I found that rolling your own is an excellent decision for a few reasons:
First, the JSON format is relatively small, unambiguous, and well documented. This allows you to focus on the architecture and interface of your wrapper. I found the experience both valuable and refreshing.
Second, you are able to employ the use of your native data structures. Naturally, this is a great way to test your functionality and interface. In the case of Sauce, I was able to leverage the following Core structures: String, Vector, Array, and HashMap.
Last, but not least, I found it to be a whole lot of fun! It’s been a while since I’ve done anything like implementing a format encoder and decoder. Hopefully when you’re finished, you feel the same.
After I finished our JSON library, I converted our config files from XML to JSON with very little effort. The result is that our config files are more compact than they were with XML, and now we have the utilities required for future development. Overall, I feel it was well worth the time and effort.