This is an implementation of Yann Collet's xxHash32 and xxHash64 algorithms (https://github.com/Cyan4973/xxHash). Just include the short xxhash32.h or xxhash64.h header - that's it, no external dependencies !
Performance of my library is usually on par with his original code. His code can be hard to understand due to the massive use of #ifdef, therefore I posted a detailled explanation of the algorithm on my website https://create.stephan-brumme.com/xxhash/ (which is also the main repository; GitHub serves as a mirror only).