1;;; rfc1843.el --- HZ (rfc1843) decoding
2
3;; Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004,
4;;   2005, 2006, 2007 Free Software Foundation, Inc.
5
6;; Author: Shenghuo Zhu <zsh@cs.rochester.edu>
7;; Keywords: news HZ HZ+ mail i18n
8
9;; This file is part of GNU Emacs.
10
11;; GNU Emacs is free software; you can redistribute it and/or modify
12;; it under the terms of the GNU General Public License as published
13;; by the Free Software Foundation; either version 2, or (at your
14;; option) any later version.
15
16;; GNU Emacs is distributed in the hope that it will be useful, but
17;; WITHOUT ANY WARRANTY; without even the implied warranty of
18;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
19;; General Public License for more details.
20
21;; You should have received a copy of the GNU General Public License
22;; along with GNU Emacs; see the file COPYING.  If not, write to the
23;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
24;; Boston, MA 02110-1301, USA.
25
26;;; Commentary:
27
28;; Usage:
29;; (require 'rfc1843)
30;; (rfc1843-gnus-setup)
31;;
32;; Test:
33;; (rfc1843-decode-string  "~{<:Ky2;S{#,NpJ)l6HK!#~}")
34
35;;; Code:
36
37(eval-when-compile (require 'cl))
38(require 'mm-util)
39
40(defvar gnus-decode-encoded-word-function)
41(defvar gnus-decode-header-function)
42(defvar gnus-newsgroup-name)
43
44(defvar rfc1843-word-regexp
45  "~\\({\\([\041-\167][\041-\176]\\| \\)+\\)\\(~}\\|$\\)")
46
47(defvar rfc1843-word-regexp-strictly
48  "~\\({\\([\041-\167][\041-\176]\\)+\\)\\(~}\\|$\\)")
49
50(defvar rfc1843-hzp-word-regexp
51  "~\\({\\([\041-\167][\041-\176]\\| \\)+\\|\
52\[<>]\\([\041-\175][\041-\176]\\| \\)+\\)\\(~}\\|$\\)")
53
54(defvar rfc1843-hzp-word-regexp-strictly
55  "~\\({\\([\041-\167][\041-\176]\\)+\\|\
56\[<>]\\([\041-\175][\041-\176]\\)+\\)\\(~}\\|$\\)")
57
58(defcustom rfc1843-decode-loosely nil
59  "Loosely check HZ encoding if non-nil.
60When it is set non-nil, only buffers or strings with strictly
61HZ-encoded are decoded."
62  :type 'boolean
63  :group 'mime)
64
65(defcustom rfc1843-decode-hzp t
66  "HZ+ decoding support if non-nil.
67HZ+ specification (also known as HZP) is to provide a standardized
687-bit representation of mixed Big5, GB, and ASCII text for convenient
69e-mail transmission, news posting, etc.
70The document of HZ+ 0.78 specification can be found at
71ftp://ftp.math.psu.edu/pub/simpson/chinese/hzp/hzp.doc"
72  :type 'boolean
73  :group 'mime)
74
75(defcustom rfc1843-newsgroups-regexp "chinese\\|hz"
76  "Regexp of newsgroups in which might be HZ encoded."
77  :type 'string
78  :group 'mime)
79
80(defun rfc1843-decode-region (from to)
81  "Decode HZ in the region between FROM and TO."
82  (interactive "r")
83  (let (str firstc)
84    (save-excursion
85      (goto-char from)
86      (if (or rfc1843-decode-loosely
87	      (re-search-forward (if rfc1843-decode-hzp
88				     rfc1843-hzp-word-regexp-strictly
89				   rfc1843-word-regexp-strictly) to t))
90	  (save-restriction
91	    (narrow-to-region from to)
92	    (goto-char (point-min))
93	    (while (re-search-forward (if rfc1843-decode-hzp
94					  rfc1843-hzp-word-regexp
95					rfc1843-word-regexp) (point-max) t)
96	      ;;; Text with extents may cause XEmacs crash
97	      (setq str (buffer-substring-no-properties
98			 (match-beginning 1)
99			 (match-end 1)))
100	      (setq firstc (aref str 0))
101	      (insert (mm-decode-coding-string
102		       (rfc1843-decode
103			(prog1
104			    (substring str 1)
105			  (delete-region (match-beginning 0) (match-end 0)))
106			firstc)
107		       (if (eq firstc ?{) 'cn-gb-2312 'cn-big5))))
108	    (goto-char (point-min))
109	    (while (search-forward "~" (point-max) t)
110	      (cond ((eq (char-after) ?\n)
111		     (delete-char -1)
112		     (delete-char 1))
113		    ((eq (char-after) ?~)
114		     (delete-char 1)))))))))
115
116(defun rfc1843-decode-string (string)
117  "Decode HZ STRING and return the results."
118  (let ((m (mm-multibyte-p)))
119    (with-temp-buffer
120      (when m
121	(mm-enable-multibyte))
122      (insert string)
123      (inline
124	(rfc1843-decode-region (point-min) (point-max)))
125      (buffer-string))))
126
127(defun rfc1843-decode (word &optional firstc)
128  "Decode HZ WORD and return it."
129  (let ((i -1) (s (substring word 0)) v)
130    (if (or (not firstc) (eq firstc ?{))
131	(while (< (incf i) (length s))
132	  (if (eq (setq v (aref s i)) ? ) nil
133	    (aset s i (+ 128 v))))
134      (while (< (incf i) (length s))
135	(if (eq (setq v (aref s i)) ? ) nil
136	  (setq v (+ (* 94 v) (aref s (1+ i)) -3135))
137	  (aset s i (+ (/ v 157) (if (eq firstc ?<) 201 161)))
138	  (setq v (% v 157))
139	  (aset s (incf i) (+ v (if (< v 63) 64 98))))))
140    s))
141
142(defun rfc1843-decode-article-body ()
143  "Decode HZ encoded text in the article body."
144  (if (string-match (concat "\\<\\(" rfc1843-newsgroups-regexp "\\)\\>")
145		    (or gnus-newsgroup-name ""))
146      (save-excursion
147	(save-restriction
148	  (message-narrow-to-head)
149	  (let* ((inhibit-point-motion-hooks t)
150		 (case-fold-search t)
151		 (ct (message-fetch-field "Content-Type" t))
152		 (ctl (and ct (mail-header-parse-content-type ct))))
153	    (if (and ctl (not (string-match "/" (car ctl))))
154		(setq ctl nil))
155	    (goto-char (point-max))
156	    (widen)
157	    (forward-line 1)
158	    (narrow-to-region (point) (point-max))
159	    (when (or (not ctl)
160		      (equal (car ctl) "text/plain"))
161	      (rfc1843-decode-region (point) (point-max))))))))
162
163(defvar rfc1843-old-gnus-decode-header-function  nil)
164(defvar gnus-decode-header-methods)
165(defvar gnus-decode-encoded-word-methods)
166
167(defun rfc1843-gnus-setup ()
168  "Setup HZ decoding for Gnus."
169  (require 'gnus-art)
170  (require 'gnus-sum)
171  (add-hook 'gnus-article-decode-hook 'rfc1843-decode-article-body t)
172  (setq gnus-decode-encoded-word-function
173	'gnus-multi-decode-encoded-word-string
174	gnus-decode-header-function
175	'gnus-multi-decode-header
176	gnus-decode-encoded-word-methods
177	(nconc gnus-decode-encoded-word-methods
178	       (list
179		(cons (concat "\\<\\(" rfc1843-newsgroups-regexp "\\)\\>")
180		      'rfc1843-decode-string)))
181	gnus-decode-header-methods
182	(nconc gnus-decode-header-methods
183	       (list
184		(cons (concat "\\<\\(" rfc1843-newsgroups-regexp "\\)\\>")
185		      'rfc1843-decode-region)))))
186
187(provide 'rfc1843)
188
189;;; arch-tag: 5149c301-a6ca-4731-9c9d-ba616e2cb687
190;;; rfc1843.el ends here
191