Extract number with given probabilities in C

Let's say I have an array probabilities = [0.1, 0.2, ..., 0.1, 0.4] of n elements. These are floating point values, not weights.

How do I extract a random integer from 1 to n with the given probabilities in Ansi C?

probabilities = [0.1, 0.2, 0.1, 0.15, 0.05, 0.1, 0.4]
extract_random_integer(probabilities)