Closed cube root finder implementation

Question

I am looking for a non-iterative function that finds the real roots of cubic polynomials. So, the implementation of something like this . I could write it myself, of course, but if someone already has an implementation and he is not against exchanging it, it will save me within 1-2 hours that I will need to write, at the cost of this person, which will take 30 seconds to insert it here, so that would be great.

Thank.