Kyoto Cabinet: is there a way to do a search for nearest key?

I'd love to be able to use one of Kyoto Cabinet's tree datastructures, but I need the ability to return the nearest key.

Ie I h开发者_开发技巧ave

1,100
3,500
7,1000

And given 2, I'd return 1.

Is this possible? If not, what is a lightweight, high speed alternative turned to do exactly this?

Thanks

Kyoto Cabinet has Cursor and you can find bigger, equal or lower key using Cursor in TreeDB.