Efficient, best way to copy a bitmap context?

Question

I have a bitmap context (iPhone/iOS) I am using for offscreen drawing prior to formal rending to a UIView. I'd like to make a copy of the bitmap context prior to performing drawing operations (and ultimately render) in the event I need to do a revert.

I haven't found a Quartz API that allows me to easily copy a bitmap context, but maybe my eyesight is failing me. I have an 'it works' solution, but it's feel dirty to leave it that way :).

Any recommendations? What is the easiest, most efficient way to do this?