intersection between circle and rectangle

Hello everyone, Given a circle of radius r and a quad (x0,y0) ( x1,y1) (x2, y2) (x3, y3) what would be the fastest way of determining if they intersect? I have figured out a way using the distance from a line example in the comp.graphics.algorithms faq but it seems rather convoluted. This is basically to provide collision detection in a 2D enviroment for a ball hitting a quad which can be rotated through any angle. Any help would be appreciated. Thankyou for your time.