| 1 | ;;; hex-util.el --- Functions to encode/decode hexadecimal string. |
| 2 | |
| 3 | ;; Copyright (C) 1999, 2001-2014 Free Software Foundation, Inc. |
| 4 | |
| 5 | ;; Author: Shuhei KOBAYASHI <shuhei@aqua.ocn.ne.jp> |
| 6 | ;; Keywords: data |
| 7 | |
| 8 | ;; This file is part of GNU Emacs. |
| 9 | |
| 10 | ;; GNU Emacs is free software: you can redistribute it and/or modify |
| 11 | ;; it under the terms of the GNU General Public License as published by |
| 12 | ;; the Free Software Foundation, either version 3 of the License, or |
| 13 | ;; (at your option) any later version. |
| 14 | |
| 15 | ;; GNU Emacs is distributed in the hope that it will be useful, |
| 16 | ;; but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 17 | ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 18 | ;; GNU General Public License for more details. |
| 19 | |
| 20 | ;; You should have received a copy of the GNU General Public License |
| 21 | ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. |
| 22 | |
| 23 | ;;; Commentary: |
| 24 | |
| 25 | ;;; Code: |
| 26 | |
| 27 | (eval-when-compile |
| 28 | (defmacro hex-char-to-num (chr) |
| 29 | `(let ((chr ,chr)) |
| 30 | (cond |
| 31 | ((and (<= ?a chr)(<= chr ?f)) (+ (- chr ?a) 10)) |
| 32 | ((and (<= ?A chr)(<= chr ?F)) (+ (- chr ?A) 10)) |
| 33 | ((and (<= ?0 chr)(<= chr ?9)) (- chr ?0)) |
| 34 | (t (error "Invalid hexadecimal digit `%c'" chr))))) |
| 35 | (defmacro num-to-hex-char (num) |
| 36 | `(aref "0123456789abcdef" ,num))) |
| 37 | |
| 38 | (defun decode-hex-string (string) |
| 39 | "Decode hexadecimal STRING to octet string." |
| 40 | (let* ((len (length string)) |
| 41 | (dst (make-string (/ len 2) 0)) |
| 42 | (idx 0)(pos 0)) |
| 43 | (while (< pos len) |
| 44 | ;; logior and lsh are not byte-coded. |
| 45 | ;; (aset dst idx (logior (lsh (hex-char-to-num (aref string pos)) 4) |
| 46 | ;; (hex-char-to-num (aref string (1+ pos))))) |
| 47 | (aset dst idx (+ (* (hex-char-to-num (aref string pos)) 16) |
| 48 | (hex-char-to-num (aref string (1+ pos))))) |
| 49 | (setq idx (1+ idx) |
| 50 | pos (+ 2 pos))) |
| 51 | dst)) |
| 52 | |
| 53 | (defun encode-hex-string (string) |
| 54 | "Encode octet STRING to hexadecimal string." |
| 55 | (let* ((len (length string)) |
| 56 | (dst (make-string (* len 2) 0)) |
| 57 | (idx 0)(pos 0)) |
| 58 | (while (< pos len) |
| 59 | ;; logand and lsh are not byte-coded. |
| 60 | ;; (aset dst idx (num-to-hex-char (logand (lsh (aref string pos) -4) 15))) |
| 61 | (aset dst idx (num-to-hex-char (/ (aref string pos) 16))) |
| 62 | (setq idx (1+ idx)) |
| 63 | ;; (aset dst idx (num-to-hex-char (logand (aref string pos) 15))) |
| 64 | (aset dst idx (num-to-hex-char (% (aref string pos) 16))) |
| 65 | (setq idx (1+ idx) |
| 66 | pos (1+ pos))) |
| 67 | dst)) |
| 68 | |
| 69 | (provide 'hex-util) |
| 70 | |
| 71 | ;;; hex-util.el ends here |