--- /dev/null
+;;; rfc1843.el --- HZ (rfc1843) decoding
+
+;; Copyright (C) 1998-2016 Free Software Foundation, Inc.
+
+;; Author: Shenghuo Zhu <zsh@cs.rochester.edu>
+;; Keywords: news HZ HZ+ mail i18n
+
+;; 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:
+
+;; Usage:
+;; (require 'rfc1843)
+;; (rfc1843-gnus-setup)
+;;
+;; Test:
+;; (rfc1843-decode-string "~{<:Ky2;S{#,NpJ)l6HK!#~}")
+
+;;; Code:
+
+(eval-when-compile (require 'cl))
+(require 'mm-util)
+
+(defvar gnus-decode-encoded-word-function)
+(defvar gnus-decode-header-function)
+(defvar gnus-newsgroup-name)
+
+(defvar rfc1843-word-regexp
+ "~\\({\\([\041-\167][\041-\176]\\| \\)+\\)\\(~}\\|$\\)")
+
+(defvar rfc1843-word-regexp-strictly
+ "~\\({\\([\041-\167][\041-\176]\\)+\\)\\(~}\\|$\\)")
+
+(defvar rfc1843-hzp-word-regexp
+ "~\\({\\([\041-\167][\041-\176]\\| \\)+\\|\
+[<>]\\([\041-\175][\041-\176]\\| \\)+\\)\\(~}\\|$\\)")
+
+(defvar rfc1843-hzp-word-regexp-strictly
+ "~\\({\\([\041-\167][\041-\176]\\)+\\|\
+[<>]\\([\041-\175][\041-\176]\\)+\\)\\(~}\\|$\\)")
+
+(defcustom rfc1843-decode-loosely nil
+ "Loosely check HZ encoding if non-nil.
+When it is set non-nil, only buffers or strings with strictly
+HZ-encoded are decoded."
+ :type 'boolean
+ :group 'mime)
+
+(defcustom rfc1843-decode-hzp t
+ "HZ+ decoding support if non-nil.
+HZ+ specification (also known as HZP) is to provide a standardized
+7-bit representation of mixed Big5, GB, and ASCII text for convenient
+e-mail transmission, news posting, etc.
+The document of HZ+ 0.78 specification can be found at
+ftp://ftp.math.psu.edu/pub/simpson/chinese/hzp/hzp.doc"
+ :type 'boolean
+ :group 'mime)
+
+(defcustom rfc1843-newsgroups-regexp "chinese\\|hz"
+ "Regexp of newsgroups in which might be HZ encoded."
+ :type 'string
+ :group 'mime)
+
+(defun rfc1843-decode-region (from to)
+ "Decode HZ in the region between FROM and TO."
+ (interactive "r")
+ (let (str firstc)
+ (save-excursion
+ (goto-char from)
+ (if (or rfc1843-decode-loosely
+ (re-search-forward (if rfc1843-decode-hzp
+ rfc1843-hzp-word-regexp-strictly
+ rfc1843-word-regexp-strictly) to t))
+ (save-restriction
+ (narrow-to-region from to)
+ (goto-char (point-min))
+ (while (re-search-forward (if rfc1843-decode-hzp
+ rfc1843-hzp-word-regexp
+ rfc1843-word-regexp) (point-max) t)
+ ;;; Text with extents may cause XEmacs crash
+ (setq str (buffer-substring-no-properties
+ (match-beginning 1)
+ (match-end 1)))
+ (setq firstc (aref str 0))
+ (insert (mm-decode-coding-string
+ (rfc1843-decode
+ (prog1
+ (substring str 1)
+ (delete-region (match-beginning 0) (match-end 0)))
+ firstc)
+ (if (eq firstc ?{) 'cn-gb-2312 'cn-big5))))
+ (goto-char (point-min))
+ (while (search-forward "~" (point-max) t)
+ (cond ((eq (char-after) ?\n)
+ (delete-char -1)
+ (delete-char 1))
+ ((eq (char-after) ?~)
+ (delete-char 1)))))))))
+
+(defun rfc1843-decode-string (string)
+ "Decode HZ STRING and return the results."
+ (let ((m (mm-multibyte-p)))
+ (with-temp-buffer
+ (when m
+ (mm-enable-multibyte))
+ (insert string)
+ (inline
+ (rfc1843-decode-region (point-min) (point-max)))
+ (buffer-string))))
+
+(defun rfc1843-decode (word &optional firstc)
+ "Decode HZ WORD and return it."
+ (let ((i -1) (s (substring word 0)) v)
+ (if (or (not firstc) (eq firstc ?{))
+ (while (< (incf i) (length s))
+ (if (eq (setq v (aref s i)) ? ) nil
+ (aset s i (+ 128 v))))
+ (while (< (incf i) (length s))
+ (if (eq (setq v (aref s i)) ? ) nil
+ (setq v (+ (* 94 v) (aref s (1+ i)) -3135))
+ (aset s i (+ (/ v 157) (if (eq firstc ?<) 201 161)))
+ (setq v (% v 157))
+ (aset s (incf i) (+ v (if (< v 63) 64 98))))))
+ s))
+
+(autoload 'mail-header-parse-content-type "mail-parse")
+(autoload 'message-narrow-to-head "message")
+(declare-function message-fetch-field "message" (header &optional not-all))
+
+(defun rfc1843-decode-article-body ()
+ "Decode HZ encoded text in the article body."
+ (if (string-match (concat "\\<\\(" rfc1843-newsgroups-regexp "\\)\\>")
+ (or gnus-newsgroup-name ""))
+ (save-excursion
+ (save-restriction
+ (message-narrow-to-head)
+ (let* ((inhibit-point-motion-hooks t)
+ (case-fold-search t)
+ (ct (message-fetch-field "Content-Type" t))
+ (ctl (and ct (mail-header-parse-content-type ct))))
+ (if (and ctl (not (string-match "/" (car ctl))))
+ (setq ctl nil))
+ (goto-char (point-max))
+ (widen)
+ (forward-line 1)
+ (narrow-to-region (point) (point-max))
+ (when (or (not ctl)
+ (equal (car ctl) "text/plain"))
+ (rfc1843-decode-region (point) (point-max))))))))
+
+(defvar gnus-decode-header-methods)
+(defvar gnus-decode-encoded-word-methods)
+
+(defun rfc1843-gnus-setup ()
+ "Setup HZ decoding for Gnus."
+ (require 'gnus-art)
+ (require 'gnus-sum)
+ (add-hook 'gnus-article-decode-hook 'rfc1843-decode-article-body t)
+ (setq gnus-decode-encoded-word-function
+ 'gnus-multi-decode-encoded-word-string
+ gnus-decode-header-function
+ 'gnus-multi-decode-header
+ gnus-decode-encoded-word-methods
+ (nconc gnus-decode-encoded-word-methods
+ (list
+ (cons (concat "\\<\\(" rfc1843-newsgroups-regexp "\\)\\>")
+ 'rfc1843-decode-string)))
+ gnus-decode-header-methods
+ (nconc gnus-decode-header-methods
+ (list
+ (cons (concat "\\<\\(" rfc1843-newsgroups-regexp "\\)\\>")
+ 'rfc1843-decode-region)))))
+
+(provide 'rfc1843)
+
+;;; rfc1843.el ends here
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