1;;; hex-util.el --- Functions to encode/decode hexadecimal string.
2
3;; Copyright (C) 1999, 2001, 2002, 2003, 2004,
4;;   2005, 2006, 2007 Free Software Foundation, Inc.
5
6;; Author: Shuhei KOBAYASHI <shuhei@aqua.ocn.ne.jp>
7;; Keywords: data
8
9;; This file is part of FLIM (Faithful Library about Internet Message).
10
11;; This program is free software; you can redistribute it and/or
12;; modify it under the terms of the GNU General Public License as
13;; published by the Free Software Foundation; either version 2, or
14;; (at your option) any later version.
15
16;; This program is distributed in the hope that it will be useful,
17;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
19;; GNU General Public License for more details.
20
21;; You should have received a copy of the GNU General Public License
22;; along with this program; see the file COPYING.  If not, write to
23;; the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
24;; Boston, MA 02110-1301, USA.
25
26;;; Commentary:
27
28;;; Code:
29
30(eval-when-compile
31  (defmacro hex-char-to-num (chr)
32    (` (let ((chr (, chr)))
33	 (cond
34	  ((and (<= ?a chr)(<= chr ?f)) (+ (- chr ?a) 10))
35	  ((and (<= ?A chr)(<= chr ?F)) (+ (- chr ?A) 10))
36	  ((and (<= ?0 chr)(<= chr ?9)) (- chr ?0))
37	  (t (error "Invalid hexadecimal digit `%c'" chr))))))
38  (defmacro num-to-hex-char (num)
39    (` (aref "0123456789abcdef" (, num)))))
40
41(defun decode-hex-string (string)
42  "Decode hexadecimal STRING to octet string."
43  (let* ((len (length string))
44	 (dst (make-string (/ len 2) 0))
45	 (idx 0)(pos 0))
46    (while (< pos len)
47;;; logior and lsh are not byte-coded.
48;;;  (aset dst idx (logior (lsh (hex-char-to-num (aref string pos)) 4)
49;;; 			    (hex-char-to-num (aref string (1+ pos)))))
50      (aset dst idx (+ (* (hex-char-to-num (aref string pos)) 16)
51		       (hex-char-to-num (aref string (1+ pos)))))
52      (setq idx (1+ idx)
53	    pos (+ 2 pos)))
54    dst))
55
56(defun encode-hex-string (string)
57  "Encode octet STRING to hexadecimal string."
58  (let* ((len (length string))
59	 (dst (make-string (* len 2) 0))
60	 (idx 0)(pos 0))
61    (while (< pos len)
62;;; logand and lsh are not byte-coded.
63;;;  (aset dst idx (num-to-hex-char (logand (lsh (aref string pos) -4) 15)))
64      (aset dst idx (num-to-hex-char (/ (aref string pos) 16)))
65      (setq idx (1+ idx))
66;;;  (aset dst idx (num-to-hex-char (logand (aref string pos) 15)))
67      (aset dst idx (num-to-hex-char (% (aref string pos) 16)))
68      (setq idx (1+ idx)
69	    pos (1+ pos)))
70    dst))
71
72(provide 'hex-util)
73
74;;; arch-tag: fe8aaa79-6c86-400e-813f-5a8cc4cb3859
75;;; hex-util.el ends here
76