--- /dev/null
+;;; hex-util.el --- Functions to encode/decode hexadecimal string.
+
+;; Copyright (C) 1999, 2001-2016 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 of the License, 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. If not, see <http://www.gnu.org/licenses/>.
+
+;;; 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)
+
+;;; hex-util.el ends here