[ushi]

Ruby implementation: https://github.com/davetroy/geohash

[jamra]

Why would you link this?

It wraps around a java jar file. I can't study the code to see how it's implemented.

[hydrozen]

I believe by default it uses the C implementation which you can read here: https://github.com/davetroy/geohash/blob/master/ext/geohash_...