This is a implementation of bas64encoding in plain lua.

lua is, like most languages, slow in string concatination.
We had a discussion about that at ccc hamburg, so we have
the idea to test this encoding with a hashmap to try, if
this is faster than encoding straid ahead to test performace.
So already encoded 3 bytes can loaded from hashmap insteed of
recoding it again (which is expensive).

We tried this code on a 200kb /dev/random file and 1Mb linux
c code (krypto part). The random file is slower on the memoized
function - of course. But on c code, it is more than 2 times
faster.

Future ideas are to make it in a module and a weak hashmap
to reduce memory consumtion.

Happy hacking.