oop is nothing magic. its simply much nicer to do in c++ than in c..
but if you want to use templates, you would have to code a preprocessor to preprocess your files before c to implement it..
there is no way to do them in c, except writing the code manually for all different possible types:D
and oop is not slow actually. really not. compilers are aware that people will use it and that they want it fast..:D