I wonder where the time's eaten up? Vinod got something like four orders of magnitude performance with ns_uuencode over Tcl code he poached from some library somewhere (he had to fix ns_uuencode first).
It's possible that unencoding is expending a lot of time, too, which could be fixed by hacking up an ns_uudecode.
Of course, I also kinda take Jon's comment to heart.
