My background is in genomics, but I have recently been working with problems related to protein structure. I wrote a few relevant programs in C, building my own PDB file parser from scratch in the process. I didn't worry about making a really robust parser, I just knew that building one myself would be the best way to force myself to really understand the PDB format.

Now that I've gone through this process, I'm looking for something a bit more robust and mature. Are there are any open-source protein structure libraries implemented in C? I was able to find a few on Google, but I had never heard of any of them before and they don't seem to be very mature or stable. A slightly related question: is everyone really doing all of these types of computations using Python? or homebrew code?

PS. I'm essentially looking for a library that includes a PDB file parser, functions for calculating bond angles, bond lengths, torsion angles, surface accessible surface area, etc.