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;;; hex-util.el --- Functions to encode/decode hexadecimal string.
;; Copyright (C) 1999, 2001-2011 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
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