How to retrieve cart contents for pushing to payments processor?

[ajuniper]

I'm currently putting together a payment processor and it requires the cart contents to be pushed to it as part of a form post.  I've looked through the other payment processors and none of them seem to do this, they only say something like "sitename order ref 1" or similar.

I had a quick look at the database structure and concluded that it's not simple to retrieve - are there any good examples of how to do this?  All I need is description/price/quantity for each item in the order and a shipping total.

Thanks,
Andy