Fast integer to decimal conversion

Question

Given an (unsigned) integer, what is the generally fastest way to convert it into a string that contains its decimal representation?

The naïve way of doing that

Answer 1

The generally fastest way is to index into a big enough array of pointers to strings. One array lookup, one pointer dereference. It's heavy on memory usage, though... That's the nature of engineering tradeoffs. How fast is fast enough?