It might be worth highlighting this library's existence more in the README:
"For a rich set of API functions which can be used to integrate tc-play functionality into your codebase, please see 'man tcplay 3'. Here is an example of a simple C program to build an encrypted volume using this library. ..."
I'll link some examples at some point, whether that is zulucrypt or the code used in DragonFly or a from-scratch example. I'm reopening so I don't forget about that.
From comment in https://github.com/bwalex/tc-play/issues/18: