Getting URL of current swf

I know I have seen the answer to this question before, but I can not seem to find it. I even thought it was on this site. Well anyway, how do you get the url of the where the current swf is located. Say test.swf is on www.kirupa.com. In test.swf how do you get the url www.kirupa.com? If I remember right there is a very very simple answer. :S

Thanks!