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;;;; GNU Anubis -- an outgoing mail processor and the SMTP tunnel.
;;;; Copyright (C) 2003 The Anubis Team.
;;;;
;;;; GNU Anubis is free software; you can redistribute it and/or modify
;;;; it under the terms of the GNU General Public License as published by
;;;; the Free Software Foundation; either version 2 of the License, or
;;;; (at your option) any later version.
;;;;
;;;; GNU Anubis is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;;; GNU General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU General Public License
;;;; along with GNU Anubis; if not, write to the Free Software
;;;; Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
;;;;
;;;; GNU Anubis is released under the GPL with the additional exemption that
;;;; compiling, linking, and/or using OpenSSL is allowed.
(define (rot-13 text)
"Encode the text using ROT-13 method"
(let ((length (string-length text)))
(do ((i 0 (1+ i)))
((>= i length) text)
(let ((c (string-ref text i)))
(cond
((char-lower-case? c)
(string-set! text i
(integer->char
(+ 97 (modulo (+ (- (char->integer c) 97) 13) 26)))))
((char-upper-case? c)
(string-set! text i
(integer->char
(+ 65 (modulo (+ (- (char->integer c) 65) 13) 26))))))))))
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