lisp/hex-util.el

   1 ;;; hex-util.el --- Functions to encode/decode hexadecimal string.
   2
   3 ;; Copyright (C) 1999, 2001, 2002, 2003, 2004,
   4 ;;   2005, 2006, 2007, 2008 Free Software Foundation, Inc.
   5
   6 ;; Author: Shuhei KOBAYASHI <shuhei@aqua.ocn.ne.jp>
   7 ;; Keywords: data
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software; you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation; either version 3, or (at your option)
  14 ;; any later version.
  15
  16 ;; GNU Emacs 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 GNU Emacs; see the file COPYING.  If not, write to the
  23 ;; 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