I want to use the unix crypt function in an OpenCL program. Does something like that already exist or will I have to translate it on my own?
You've probably found an answer by now, but in case anyone else comes here from a search, John The Ripper is open source and has OpenCL acceleration for several hashing algorithms, including the 3DES used in BSD crypt().
https://github.com/magnumripper/JohnTheRipper/tree/bleeding-jumbo/src/opencl