[Tilecache] Tilenameing when using bounds

[Roeland Douma]

Hi all,

I'm working on a tile expire script that deletes tiles bases on the 
openstreetmap diffs. So we can serve almost live maps.

The problem I'm referring to is when using bounds. (see the source of 
http://tile.openstreetmap.nl ). The tile numbering is different. It starts in 
the topleft corner of the bounds.

How can I convert lon / lat coordinates to the x,y tiles when using bounds?

Thanks in advance for any help,
--Roeland