No endian safety
The vast majority of devices and machines these days are little-endian, but this extension doesn't consider the possibility of being compiled and run on a big-endian platform. If it is run on a big-endian platform, then lots of unpleasant things could occur, like word array corruption, generated chunks having the wrong byte order, client crashes, and so on and so forth.
Initial tests (with extra hacks to stop client crashes) yield the following results:

Since both disk saves and network sends are little endian, it would probably be best to have some big-endian-specific conversion code to translate little-endian packed byte arrays to/from big-endian in-memory format on the interfaces. This would produce some minor performance loss for big-endian platforms, but I think those are rare enough that nobody should really care.
In the meantime, you should throw an error on compilation for non-little-endian platforms