> There is a real need of non-blocking operation, but I now think that
> adding a set_blocking() method is not the right solution. First, as
> said by Charles-Francois: O_NONBLOCK flag has no effect on regular
> files. Second, there is no portable way to declare a file as "non
> blocking": as said by Tim, it is complelty different on Windows (I/O
> Completion ports).

That it's not portable is actually a good reason to add a helper function
or method.