133 lines
4.1 KiB
EmacsLisp
133 lines
4.1 KiB
EmacsLisp
;;; rfc1843.el --- HZ (RFC 1843) decoding -*- lexical-binding:t -*-
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;; Copyright (C) 1998-2024 Free Software Foundation, Inc.
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;; Author: Shenghuo Zhu <zsh@cs.rochester.edu>
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;; Keywords: news HZ HZ+ mail i18n
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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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;; HZ (RFC 1843) decoding. HZ is a data format for exchanging files
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;; of arbitrarily mixed Chinese and ASCII characters.
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;;
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;; Test:
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;; (rfc1843-decode-string "~{<:Ky2;S{#,NpJ)l6HK!#~}")
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;;; Code:
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(eval-when-compile (require 'cl-lib))
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(defvar rfc1843-word-regexp
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"~\\({\\([\041-\167][\041-\176]\\| \\)+\\)\\(~}\\|$\\)")
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(defvar rfc1843-word-regexp-strictly
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"~\\({\\([\041-\167][\041-\176]\\)+\\)\\(~}\\|$\\)")
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(defvar rfc1843-hzp-word-regexp
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"~\\({\\([\041-\167][\041-\176]\\| \\)+\\|\
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[<>]\\([\041-\175][\041-\176]\\| \\)+\\)\\(~}\\|$\\)")
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(defvar rfc1843-hzp-word-regexp-strictly
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"~\\({\\([\041-\167][\041-\176]\\)+\\|\
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[<>]\\([\041-\175][\041-\176]\\)+\\)\\(~}\\|$\\)")
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(defcustom rfc1843-decode-loosely nil
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"Loosely check HZ encoding if non-nil.
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When it is set non-nil, only buffers or strings with strictly
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HZ-encoded are decoded."
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:type 'boolean
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:group 'mime)
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(defcustom rfc1843-decode-hzp t
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"HZ+ decoding support if non-nil.
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HZ+ specification (also known as HZP) is to provide a standardized
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7-bit representation of mixed Big5, GB, and ASCII text for convenient
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e-mail transmission, news posting, etc."
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:type 'boolean
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:group 'mime)
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(defcustom rfc1843-newsgroups-regexp "chinese\\|hz"
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"Regexp of newsgroups in which might be HZ encoded."
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:type 'regexp
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:group 'mime)
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(defun rfc1843-decode-region (from to)
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"Decode HZ in the region between FROM and TO."
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(interactive "r")
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(let (str firstc)
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(save-excursion
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(goto-char from)
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(if (or rfc1843-decode-loosely
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(re-search-forward (if rfc1843-decode-hzp
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rfc1843-hzp-word-regexp-strictly
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rfc1843-word-regexp-strictly) to t))
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(save-restriction
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(narrow-to-region from to)
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(goto-char (point-min))
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(while (re-search-forward (if rfc1843-decode-hzp
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rfc1843-hzp-word-regexp
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rfc1843-word-regexp) (point-max) t)
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(setq str (buffer-substring-no-properties
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(match-beginning 1)
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(match-end 1)))
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(setq firstc (aref str 0))
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(insert (decode-coding-string
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(rfc1843-decode
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(prog1
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(substring str 1)
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(delete-region (match-beginning 0) (match-end 0)))
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firstc)
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(if (eq firstc ?{) 'cn-gb-2312 'cn-big5))))
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(goto-char (point-min))
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(while (search-forward "~" (point-max) t)
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(cond ((eq (char-after) ?\n)
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(delete-char -1)
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(delete-char 1))
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((eq (char-after) ?~)
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(delete-char 1)))))))))
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(defun rfc1843-decode-string (string)
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"Decode HZ STRING and return the results."
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(let ((m enable-multibyte-characters))
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(with-temp-buffer
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(when m
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(set-buffer-multibyte 'to))
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(insert string)
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(inline
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(rfc1843-decode-region (point-min) (point-max)))
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(buffer-string))))
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(defun rfc1843-decode (word &optional firstc)
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"Decode HZ WORD and return it."
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(let ((i -1) (s (substring word 0)) v)
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(if (or (not firstc) (eq firstc ?{))
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(while (< (cl-incf i) (length s))
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(if (eq (setq v (aref s i)) ? ) nil
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(aset s i (+ 128 v))))
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(while (< (cl-incf i) (length s))
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(if (eq (setq v (aref s i)) ? ) nil
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(setq v (+ (* 94 v) (aref s (1+ i)) -3135))
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(aset s i (+ (/ v 157) (if (eq firstc ?<) 201 161)))
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(setq v (% v 157))
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(aset s (cl-incf i) (+ v (if (< v 63) 64 98))))))
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s))
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(provide 'rfc1843)
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;;; rfc1843.el ends here
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