Simple POSIX Semaphore Library for Windows

dandenongs 1889

I had a recent need to control access of one of my programs to a hardware device – basically the hardware can only handle a certain number of simultaneous connections before it starts returning garbage. POSIX semaphores are a really elegant way of handling this as you just create a semaphore and then put a semi_wait call before every critical code section and a sem_post call at the end of the critical code. This way you can control the number of simultaneous calls of the critical code no matter how many parallel processes or threads are running.

The only problem with POSIX semaphores is they are not natively supported on Windows (Windows has a entirely different semaphore system). Since my program is cross-platform I wanted a simple Windows-compatible POSIX semaphore library I could just drop in on my Windows builds and avoid a whole series of #ifdef #else conditionals. I managed to find a full Windows POSIX thread library (libpthread), but it was way more complex than what I needed and it does not build on Windows XP (I unfortunately still need to support Windows XP/2003). I was able to use the library as a starting point for making a very simple POSIX semaphore library. My cut-down library provides a simple drop in replacement for all the POSIX semaphore functions on Windows and just requires the inclusion of the header file in any project you might want to use it in. It is not identical to semaphores on linux, but it does the job.

You can download the simple windows semaphore library from my github repository. I hope it is of help for someone else.

Leave a Reply

Your email address will not be published. Required fields are marked *