A UTF-8 decoder in C99, implemented in 27 lines of code:

Systems with elaborate Unicode support usually confront programmers with a multitude of different functions and macros to process UTF-8 encoded strings, often with different ideas on handling buffer boundaries, state between calls, error conditions, and performance characteristics, making them difficult to use correctly and efficiently. Implementations also tend to be very long and complicated; one popular library has over 500 lines of code just for one version of the decoder. This page presents one that is very easy to use correctly, short, small, fast, and free.