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+;;; hex-util.el --- Functions to encode/decode hexadecimal string.
+
+;; Copyright (C) 1999, 2001, 2002, 2003, 2004,
+;;   2005, 2006, 2007 Free Software Foundation, Inc.
+
+;; Author: Shuhei KOBAYASHI <shuhei@aqua.ocn.ne.jp>
+;; Keywords: data
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs 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, or (at your option)
+;; any later version.
+
+;; GNU Emacs 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 Emacs; see the file COPYING.  If not, write to the
+;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+;; Boston, MA 02110-1301, USA.
+
+;;; Commentary:
+
+;;; Code:
+
+(eval-when-compile
+  (defmacro hex-char-to-num (chr)
+    `(let ((chr ,chr))
+       (cond
+        ((and (<= ?a chr)(<= chr ?f)) (+ (- chr ?a) 10))
+        ((and (<= ?A chr)(<= chr ?F)) (+ (- chr ?A) 10))
+        ((and (<= ?0 chr)(<= chr ?9)) (- chr ?0))
+        (t (error "Invalid hexadecimal digit `%c'" chr)))))
+  (defmacro num-to-hex-char (num)
+    `(aref "0123456789abcdef" ,num)))
+
+(defun decode-hex-string (string)
+  "Decode hexadecimal STRING to octet string."
+  (let* ((len (length string))
+	 (dst (make-string (/ len 2) 0))
+	 (idx 0)(pos 0))
+    (while (< pos len)
+      ;; logior and lsh are not byte-coded.
+      ;; (aset dst idx (logior (lsh (hex-char-to-num (aref string pos)) 4)
+      ;; 			    (hex-char-to-num (aref string (1+ pos)))))
+      (aset dst idx (+ (* (hex-char-to-num (aref string pos)) 16)
+		       (hex-char-to-num (aref string (1+ pos)))))
+      (setq idx (1+ idx)
+	    pos (+ 2 pos)))
+    dst))
+
+(defun encode-hex-string (string)
+  "Encode octet STRING to hexadecimal string."
+  (let* ((len (length string))
+	 (dst (make-string (* len 2) 0))
+	 (idx 0)(pos 0))
+    (while (< pos len)
+      ;; logand and lsh are not byte-coded.
+      ;; (aset dst idx (num-to-hex-char (logand (lsh (aref string pos) -4) 15)))
+      (aset dst idx (num-to-hex-char (/ (aref string pos) 16)))
+      (setq idx (1+ idx))
+      ;; (aset dst idx (num-to-hex-char (logand (aref string pos) 15)))
+      (aset dst idx (num-to-hex-char (% (aref string pos) 16)))
+      (setq idx (1+ idx)
+	    pos (1+ pos)))
+    dst))
+
+(provide 'hex-util)
+
+;; arch-tag: fe8aaa79-6c86-400e-813f-5a8cc4cb3859
+;;; hex-util.el ends here