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72 lines
2.4 KiB
EmacsLisp
72 lines
2.4 KiB
EmacsLisp
;;; hex-util.el --- Functions to encode/decode hexadecimal string -*- lexical-binding: t -*-
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;; Copyright (C) 1999, 2001-2019 Free Software Foundation, Inc.
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;; Author: Shuhei KOBAYASHI <shuhei@aqua.ocn.ne.jp>
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;; Keywords: data
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary:
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;;; Code:
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(eval-when-compile
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(defmacro hex-char-to-num (chr)
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`(let ((chr ,chr))
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(cond
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((and (<= ?a chr)(<= chr ?f)) (+ (- chr ?a) 10))
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((and (<= ?A chr)(<= chr ?F)) (+ (- chr ?A) 10))
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((and (<= ?0 chr)(<= chr ?9)) (- chr ?0))
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(t (error "Invalid hexadecimal digit `%c'" chr)))))
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(defmacro num-to-hex-char (num)
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`(aref "0123456789abcdef" ,num)))
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(defun decode-hex-string (string)
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"Decode hexadecimal STRING to octet string."
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(let* ((len (length string))
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(dst (make-string (/ len 2) 0))
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(idx 0)(pos 0))
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(while (< pos len)
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;; logior and lsh are not byte-coded.
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;; (aset dst idx (logior (lsh (hex-char-to-num (aref string pos)) 4)
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;; (hex-char-to-num (aref string (1+ pos)))))
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(aset dst idx (+ (* (hex-char-to-num (aref string pos)) 16)
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(hex-char-to-num (aref string (1+ pos)))))
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(setq idx (1+ idx)
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pos (+ 2 pos)))
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dst))
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(defun encode-hex-string (string)
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"Encode octet STRING to hexadecimal string."
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(let* ((len (length string))
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(dst (make-string (* len 2) 0))
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(idx 0)(pos 0))
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(while (< pos len)
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;; logand and lsh are not byte-coded.
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;; (aset dst idx (num-to-hex-char (logand (lsh (aref string pos) -4) 15)))
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(aset dst idx (num-to-hex-char (/ (aref string pos) 16)))
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(setq idx (1+ idx))
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;; (aset dst idx (num-to-hex-char (logand (aref string pos) 15)))
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(aset dst idx (num-to-hex-char (% (aref string pos) 16)))
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(setq idx (1+ idx)
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pos (1+ pos)))
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dst))
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(provide 'hex-util)
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;;; hex-util.el ends here
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