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[emacs.git] / lisp / rot13.el
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1 ;;; rot13.el --- display a buffer in rot13.
3 ;; Copyright (C) 1988 Free Software Foundation, Inc.
5 ;; Author: Howard Gayle:
6 ;; Maintainer: FSF
8 ;; This file is part of GNU Emacs.
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.
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.
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.
25 ;;; Commentary:
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.
33 ;; Written by Howard Gayle.
34 ;; This hack is mainly to show off the char table stuff.
36 ;;; Code:
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.")
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)))
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))))
65 (provide 'rot13)
67 ;;; rot13.el ends here