base64.el

;; fixed base64-decode-region that works with any number of characters (not just modulo 4)
(defun base64-decode ()
  (interactive)
  (when mark-active
    (let* ((first (region-beginning))
           (last  (region-end))
           (s (buffer-substring first last))
           (slen (length s))
           (srem (% slen 4))
           (adjust (if (zerop srem)
                       ""
                     (make-string (- 4 srem) ?=)))
           (s (concat s adjust)))
      (save-excursion
        (delete-region first last)
        (goto-char first)
        (insert (base64-decode-string s))))))