ange-ftp-file-size is a compiled Lisp function in `ange-ftp.el'.

(ange-ftp-file-size FILE &optional ASCII-MODE)

Return the size of remote file FILE. Return -1 if can't get it.
If ascii-mode is non-nil, return the size with the extra octets that
need to be inserted, one at the end of each line, to provide correct
end-of-line semantics for a transfer using TYPE=A. The default is nil,
so return the size on the remote host exactly. See RFC 3659.