Merge from emacs--rel--22
[bpt/emacs.git] / lisp / nxml / nxml-enc.el
1 ;;; nxml-enc.el --- XML encoding auto-detection
2
3 ;; Copyright (C) 2003, 2007, 2008 Free Software Foundation, Inc.
4
5 ;; Author: James Clark
6 ;; Keywords: XML
7
8 ;; This file is part of GNU Emacs.
9
10 ;; GNU Emacs is free software; you can redistribute it and/or modify
11 ;; it under the terms of the GNU General Public License as published by
12 ;; the Free Software Foundation; either version 3, or (at your option)
13 ;; any later version.
14
15 ;; GNU Emacs is distributed in the hope that it will be useful,
16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 ;; GNU General Public License for more details.
19
20 ;; You should have received a copy of the GNU General Public License
21 ;; along with GNU Emacs; see the file COPYING. If not, write to the
22 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
23 ;; Boston, MA 02110-1301, USA.
24
25 ;;; Commentary:
26
27 ;; User entry points are nxml-start-auto-coding and
28 ;; nxml-stop-auto-coding. This is separate from nxml-mode, because
29 ;; this cannot be autoloaded. It may use
30 ;; `xmltok-get-declared-encoding-position' which can be autoloaded.
31 ;; It's separate from rng-auto.el so it can be byte-compiled, and
32 ;; because it provides independent, useful functionality.
33
34 ;;; Code:
35
36 (defvar nxml-file-name-ignore-case
37 (memq system-type '(vax-vms windows-nt)))
38
39 (defvar nxml-cached-file-name-auto-coding-regexp nil)
40 (defvar nxml-cached-auto-mode-alist nil)
41
42 (defun nxml-file-name-auto-coding-regexp ()
43 "Return regexp for filenames for which XML auto-coding should be done."
44 (if (eq auto-mode-alist nxml-cached-auto-mode-alist)
45 nxml-cached-file-name-auto-coding-regexp
46 (let ((alist auto-mode-alist)
47 (case-fold-search nxml-file-name-ignore-case)
48 regexps)
49 (setq nxml-cached-auto-mode-alist alist)
50 (while alist
51 (when (eq (cdar alist) 'nxml-mode)
52 (setq regexps (cons (caar alist) regexps)))
53 (setq alist (cdr alist)))
54 (setq nxml-cached-file-name-auto-coding-regexp
55 (if (null (cdr regexps))
56 (car regexps)
57 (mapconcat (lambda (r)
58 (concat "\\(?:" r "\\)"))
59 regexps
60 "\\|"))))))
61
62 (defvar nxml-non-xml-set-auto-coding-function nil
63 "The function that `set-auto-coding-function' should call for non-XML files.")
64 (defun nxml-set-auto-coding (file-name size)
65 (if (let ((case-fold-search nxml-file-name-ignore-case)
66 (regexp (nxml-file-name-auto-coding-regexp)))
67 (and regexp
68 (string-match regexp file-name)))
69 (nxml-set-xml-coding file-name size)
70 (and nxml-non-xml-set-auto-coding-function
71 (funcall nxml-non-xml-set-auto-coding-function file-name size))))
72
73 (defun nxml-set-xml-coding (file-name size)
74 "Function to use as `set-auto-coding-function' when file is known to be XML."
75 (nxml-detect-coding-system (+ (point) (min size 1024))))
76
77 (declare-function xmltok-get-declared-encoding-position "xmltok"
78 (&optional limit)) ; autoloaded
79
80 (defun nxml-detect-coding-system (limit)
81 (if (< limit (+ (point) 2))
82 (if (eq (char-after) 0) 'no-conversion 'utf-8)
83 (let ((first-two-chars (list (char-after)
84 (char-after (1+ (point))))))
85 (cond ((equal first-two-chars '(#xFE #xFF))
86 (and (coding-system-p 'utf-16-be) 'utf-16-be))
87 ((equal first-two-chars '(#xFF #xFE))
88 (and (coding-system-p 'utf-16-le) 'utf-16-le))
89 ((memq 0 first-two-chars)
90 ;; Certainly not well-formed XML;
91 ;; perhaps UTF-16 without BOM.
92 ;; In any case, we can't handle it.
93 ;; no-conversion gives the user a chance to fix it.
94 'no-conversion)
95 ;; There are other things we might try here in the future
96 ;; eg UTF-8 BOM, UTF-16 with no BOM
97 ;; translate to EBCDIC
98 (t
99 (let ((enc-pos (xmltok-get-declared-encoding-position limit)))
100 (cond ((consp enc-pos)
101 (or (nxml-mime-charset-coding-system
102 (buffer-substring-no-properties (car enc-pos)
103 (cdr enc-pos)))
104 ;; We have an encoding whose name we don't recognize.
105 ;; What to do?
106 ;; raw-text seems the best bet: since we got
107 ;; the XML decl it must be a superset of ASCII,
108 ;; so we don't need to go to no-conversion
109 'raw-text))
110 (enc-pos 'utf-8)
111 ;; invalid XML declaration
112 (t nil))))))))
113
114 (defun nxml-mime-charset-coding-system (charset)
115 (let ((charset-sym (intern (downcase charset)))
116 (coding-systems (coding-system-list t))
117 coding-system ret)
118 (while (and coding-systems (not ret))
119 (setq coding-system (car coding-systems))
120 (if (eq (coding-system-get coding-system 'mime-charset)
121 charset-sym)
122 (setq ret coding-system)
123 (setq coding-systems (cdr coding-systems))))
124 ret))
125
126 (defun nxml-start-auto-coding ()
127 "Do encoding auto-detection as specified in the XML standard.
128 Applied to any files that `auto-mode-alist' says should be handled by
129 `nxml-mode'."
130 (interactive)
131 (unless (eq set-auto-coding-function 'nxml-set-auto-coding)
132 (let ((inhibit-quit t))
133 (setq nxml-non-xml-set-auto-coding-function set-auto-coding-function)
134 (setq set-auto-coding-function 'nxml-set-auto-coding))))
135
136 (defun nxml-stop-auto-coding ()
137 "Stop doing encoding auto-detection as specified in the XML standard."
138 (interactive)
139 (when (eq set-auto-coding-function 'nxml-set-auto-coding)
140 (let ((inhibit-quit t))
141 (setq set-auto-coding-function nxml-non-xml-set-auto-coding-function)
142 (setq nxml-non-xml-set-auto-coding-function nil))))
143
144 (unless (coding-system-p 'us-ascii)
145 (make-coding-system
146 ;; Unicode Emacs uses ?- last time I looked
147 'us-ascii 2 ?-
148 "ISO 2022 based 7-bit encoding for ASCII (MIME:US-ASCII)"
149 '(ascii)
150 '((safe-charsets ascii)
151 (mime-charset . us-ascii))))
152
153 ;; Emacs 21.3.50 makes us-ascii an alias for iso-safe without
154 ;; giving it a mime-charset property.
155 (unless (coding-system-get 'us-ascii 'mime-charset)
156 (coding-system-put 'us-ascii 'mime-charset 'us-ascii))
157
158 ;; Work around bug in Emacs 21.3
159
160 (when (and (coding-system-p 'utf-16-le)
161 (eq (coding-system-get 'utf-16-le 'pre-write-conversion)
162 'utf-16-le-pre-write-conversion))
163 (coding-system-put 'utf-16-le 'pre-write-conversion nil))
164
165 (when (and (coding-system-p 'utf-16-le)
166 (eq (coding-system-get 'utf-16-be 'pre-write-conversion)
167 'utf-16-be-pre-write-conversion))
168 (coding-system-put 'utf-16-be 'pre-write-conversion nil))
169
170 (provide 'nxml-enc)
171
172 ;; arch-tag: c2436247-78f3-418c-8069-85dc5335d083
173 ;;; nxml-enc.el ends here