[cairo] finding the size of a cairo surface

[L A]

I am trying to modify a piece of code that was written for
cairo_image_surfaces. I would like to use cairo directfb surfaces
instead of image surfaces (for hw accel) and I am trying to avoid
changing the API. The issue is the size of the surface. How can I
replace cairo_image_surface_get_width/height calls?

Thanks
Levent