In order to implement tools such as MuTool, and helpers such as mu-office-lib, we needed a simple cross platform threading library. MuThreads is that library.
It is a very simple interface layer that gives a consistent implementation of Mutexes, Semaphores and Threads that builds both on pthreads and on Windows threads. More platforms may be added in the future.
The interface is described in a single header, ‘mupdf/helpers/mu-threads.h’, and should be self-evident.