uri decode base64

Hi All,

uri is base64 encoded from server side (uri encoding done in .net code) as this is a POST done from server. I want to decode base64. Tried below irule but not of help. Anybod who has done base64 decode on f5.

when HTTP_REQUEST {
set tmpUri [string tolower [HTTP::uri]]
set tmpUri2 [URI::decode $tmpUri]
while { $tmpUri2 ne $tmpUri } {
set tmpUri $tmpUri2
set tmpUri2 [URI::decode $tmpUri]
}
}