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;;;
;;; rot-13.scm
;;;
;;; This file is part of GNU Anubis.
;;; Copyright (C) 2003, 2004, 2007 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 3 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, see <http://www.gnu.org/licenses/>.
(define (rot-13-text input)
"Encode the text using ROT-13 method"
(let* ((text (string-append "" input))
(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))))))))))
(define (rot-13 hdr body . rest)
(let ((rs (lambda (h)
(map (lambda (x)
(if (string-ci=? (car x) "subject")
(cons (car x) (rot-13-text (cdr x)))
x))
h))))
(if (null? rest)
(cons (rs hdr) (rot-13-text body))
(cons (if (member #:subject rest)
(rs hdr)
#t)
(if (member #:body rest)
(rot-13-text body)
#t)))))
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