lisp/rot13.el

   1 ;;; rot13.el --- display a buffer in rot13.
   2
   3 ;; Copyright (C) 1988 Free Software Foundation, Inc.
   4
   5 ;; Author: Howard Gayle:
   6 ;; Maintainer: FSF
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26
  27 ;; The single entry point, `rot13-other-window', performs a Caesar cipher
  28 ;; encrypt/decrypt on the current buffer and displays the result in another
  29 ;; window.  Rot13 encryption is sometimes used on USENET as a read-at-your-
  30 ;; own-risk wrapper for material some might consider offensive, such as
  31 ;; ethnic humor.
  32 ;;
  33 ;; Written by Howard Gayle.
  34 ;; This hack is mainly to show off the char table stuff.
  35
  36 ;;; Code:
  37
  38 (defvar rot13-display-table
  39   (let ((table (make-display-table))
  40         (i 0))
  41     (while (< i 26)
  42       (aset table (+ i ?a) (vector (+ (% (+ i 13) 26) ?a)))
  43       (aset table (+ i ?A) (vector (+ (% (+ i 13) 26) ?A)))
  44       (setq i (1+ i)))
  45     table)
  46   "Char table for rot 13 display.")
  47
  48 ;;;###autoload
  49 (defun rot13-other-window ()
  50   "Display current buffer in rot 13 in another window.
  51 To terminate the rot13 display, delete that window."
  52   (interactive)
  53   (let ((w (display-buffer (current-buffer) t)))
  54     (set-window-display-table w rot13-display-table)))
  55
  56 ;;;###autoload
  57 (defun toggle-rot13-mode ()
  58   "Toggle the use of rot 13 encoding for the current window."
  59   (interactive)
  60   (if (eq (window-display-table (selected-window)) rot13-display-table)
  61       (set-window-display-table (selected-window) nil)
  62     (if (null (window-display-table (selected-window)))
  63         (set-window-display-table (selected-window) rot13-display-table))))
  64
  65 (provide 'rot13)
  66
  67 ;;; rot13.el ends here