Can you be more specific to your problem, coz what gives me impression is you want to reverse string with "null" as a part of string
ActionScript's String class doesn't have a reverse() method, but the Array class does. So you could use String's split() method to split it into characters, Array's reverse() method to reverse them, and Array's join() method to join them back into a reversed String.
As for ASCII NUL characters, they are allowed anywhere inside an ActionScript String. ActionScript doesn't use NUL to terminate a String, like C does.
Adobe Flex SDK Team