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
  22 ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  23
  24 ;;; Commentary:
  25
  26 ;; The single entry point, `rot13-other-window', performs a Caesar cipher
  27 ;; encrypt/decrypt on the current buffer and displays the result in another
  28 ;; window.  Rot13 encryption is sometimes used on USENET as a read-at-your-
  29 ;; own-risk wrapper for material some might consider offensive, such as
  30 ;; ethnic humor.
  31 ;;
  32 ;; Written by Howard Gayle.
  33 ;; This hack is mainly to show off the char table stuff.
  34
  35 ;;; Code:
  36
  37 (defvar rot13-display-table
  38   (let ((table (make-display-table))
  39         (i 0))
  40     (while (< i 26)
  41       (aset table (+ i ?a) (vector (+ (% (+ i 13) 26) ?a)))
  42       (aset table (+ i ?A) (vector (+ (% (+ i 13) 26) ?A)))
  43       (setq i (1+ i)))
  44     table)
  45   "Char table for rot 13 display.")
  46
  47 ;;;###autoload
  48 (defun rot13-other-window ()
  49   "Display current buffer in rot 13 in another window.
  50 To terminate the rot13 display, delete that window."
  51   (interactive)
  52   (let ((w (display-buffer (current-buffer) t)))
  53     (set-window-display-table w rot13-display-table)))
  54
  55 ;;;###autoload
  56 (defun toggle-rot13-mode ()
  57   "Toggle the use of rot 13 encoding for the current window."
  58   (interactive)
  59   (if (eq (window-display-table (selected-window)) rot13-display-table)
  60       (set-window-display-table (selected-window) nil)
  61     (if (null (window-display-table (selected-window)))
  62         (set-window-display-table (selected-window) rot13-display-table))))
  63
  64 (provide 'rot13)
  65
  66 ;;; rot13.el ends here