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347003be DL |
1 | ;;; utf-7.el --- utf-7 coding system |
2 | ||
3 | ;; Copyright (C) 2003 Free Software Foundation, Inc. | |
4 | ||
5 | ;; Author: Dave Love <fx@gnu.org> | |
6 | ;; Keywords: i18n, mail | |
7 | ||
8 | ;; This file is free software; you can redistribute it and/or modify | |
9 | ;; it under the terms of the GNU General Public License as published by | |
10 | ;; the Free Software Foundation; either version 2, or (at your option) | |
11 | ;; any later version. | |
12 | ||
13 | ;; This file is distributed in the hope that it will be useful, | |
14 | ;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
15 | ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
16 | ;; GNU General Public License for more details. | |
17 | ||
18 | ;; You should have received a copy of the GNU General Public License | |
19 | ;; along with GNU Emacs; see the file COPYING. If not, write to | |
20 | ;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
21 | ;; Boston, MA 02111-1307, USA. | |
22 | ||
23 | ;;; Commentary: | |
24 | ||
25 | ;; Defines a coding system for UTF-7, defined in RFC 2152. Non-ASCII | |
26 | ;; segments are encoded as base64-encoded big endian UTF-16. Also | |
27 | ;; defines a variation required for IMAP (RFC 2060). | |
28 | ||
29 | ;; The encoding and decoding was originally taken from Jon K Hellan's | |
30 | ;; implementation in Gnus, but has been substantially re-done. | |
31 | ||
32 | ;; This probably needs more attention. In particular, it's not | |
33 | ;; completely consistent with iconv's behaviour. It's arguable | |
34 | ;; whether the IMAP version should be a coding system since it's | |
35 | ;; apparently only used for IMAP mailbox names, so it's commented out. | |
36 | ||
37 | ;;; Code: | |
38 | ||
39 | (make-coding-system | |
40 | 'utf-7 0 ?U | |
41 | "UTF-7 encoding of Unicode (RFC 2152)" | |
42 | nil | |
9ef9b28e | 43 | `((safe-chars . ,(coding-system-get 'utf-16be 'safe-chars)) |
347003be DL |
44 | (mime-charset . utf-7) |
45 | (pre-write-conversion . utf-7-pre-write-conversion) | |
46 | (post-read-conversion . utf-7-post-read-conversion))) | |
47 | ||
48 | ;; (make-coding-system | |
49 | ;; 'utf-7-imap 0 ?u | |
50 | ;; "UTF-7 encoding of Unicode, IMAP version (RFC 2060)" | |
51 | ;; nil | |
9ef9b28e | 52 | ;; `((safe-chars . ,(coding-system-get 'utf-16be 'safe-chars)) |
347003be DL |
53 | ;; (pre-write-conversion . utf-7-imap-pre-write-conversion) |
54 | ;; (post-read-conversion . utf-7-imap-post-read-conversion))) | |
55 | ||
56 | (defun utf-7-decode (len imap) | |
57 | "Decode LEN bytes of UTF-7 at point. | |
58 | IMAP non-nil means use the IMAP version." | |
59 | (save-excursion | |
60 | (save-restriction | |
61 | (narrow-to-region (point) (+ (point) len)) | |
62 | (let ((not-esc (if imap "^&" "^+")) | |
63 | (skip-chars (if imap "A-Za-z0-9+," "A-Za-z0-9+/"))) | |
64 | (while (not (eobp)) | |
65 | (skip-chars-forward not-esc) | |
66 | (unless (eobp) | |
67 | (forward-char) | |
68 | (let ((p (point)) | |
69 | (run-length (skip-chars-forward skip-chars))) | |
70 | (if (eq ?- (char-after)) | |
71 | (delete-char 1)) | |
72 | (unless (= run-length 0) ; encoded lone esc-char | |
73 | (let ((pl (mod (- run-length) 4))) | |
74 | (insert-char ?= pl) | |
75 | (if imap | |
76 | (subst-char-in-region p (point) ?, ?/)) | |
77 | (base64-decode-region p (point))) | |
9ef9b28e | 78 | (decode-coding-region p (point) 'utf-16be) |
347003be DL |
79 | (save-excursion |
80 | (goto-char p) | |
81 | (delete-backward-char 1))))))) | |
82 | (- (point-max) (point-min))))) | |
83 | ||
84 | (defun utf-7-post-read-conversion (len) | |
85 | (utf-7-decode len nil)) | |
86 | ||
87 | ;; (defun utf-7-imap-post-read-conversion (len) | |
88 | ;; (utf-7-decode len t)) | |
89 | ||
90 | (defun utf-7-encode (from to imap) | |
91 | "Encode bytes between FROM and TO to UTF-7. | |
92 | ESC and SKIP-CHARS are adjusted for the normal and IMAP versions." | |
93 | (let* ((old-buf (current-buffer)) | |
94 | (esc (if imap ?& ?+)) | |
95 | ;; These are characters which can be encoded asis. | |
96 | (skip-chars (if imap | |
97 | "\t\n\r\x20-\x25\x27-\x7e" ; rfc2060 | |
98 | ;; This includes the rfc2152 optional set. | |
99 | ;; Perhaps it shouldn't (like iconv). | |
100 | "\t\n\r -*,-[]-}")) | |
101 | (not-skip-chars (format "^%s%c" skip-chars esc))) | |
102 | (set-buffer (generate-new-buffer " *temp*")) | |
103 | (if (stringp from) | |
104 | (insert from) | |
105 | (insert-buffer-substring old-buf from to)) | |
106 | (goto-char (point-min)) | |
107 | (while (not (eobp)) | |
108 | (skip-chars-forward skip-chars) | |
109 | (if (eq ?+ (char-after)) | |
110 | (progn (forward-char) | |
111 | (insert ?-)) | |
112 | (unless (eobp) | |
113 | (insert esc) | |
114 | (let ((p (point))) | |
115 | (skip-chars-forward not-skip-chars) | |
116 | (save-restriction | |
117 | ;; encode-coding-region doesn't preserve point | |
118 | (narrow-to-region p (point)) | |
9ef9b28e | 119 | (encode-coding-region p (point-max) 'utf-16be) |
347003be DL |
120 | (base64-encode-region p (point-max)) |
121 | (if imap | |
122 | (subst-char-in-region p (point-max) ?/ ?,)) | |
123 | (goto-char p) | |
124 | ;; As I read the RFC, this isn't correct, but it's | |
125 | ;; consistent with iconv, at least regarding `='. | |
126 | (skip-chars-forward "^= \t\n") | |
127 | (delete-region (point) (point-max)))) | |
128 | (unless (eobp) | |
129 | (insert ?-))))) | |
130 | nil)) | |
131 | ||
132 | (defun utf-7-pre-write-conversion (from to) | |
133 | (utf-7-encode from to nil)) | |
134 | ||
135 | ;; (defun utf-7-imap-pre-write-conversion (from to) | |
136 | ;; (utf-7-encode from to t)) | |
137 | ||
138 | (provide 'utf-7) | |
ab5796a9 MB |
139 | |
140 | ;;; arch-tag: 975ee403-90a4-4286-97d2-4ed1323f4ef9 | |
347003be | 141 | ;;; utf-7.el ends here |