* src/xdisp.c (select_frame_for_redisplay): Keep selected_window and
[emacs.git] / lisp / nxml / nxml-enc.el
blobdffea031b97fc98b93666a5c8db708b324178950
1 ;;; nxml-enc.el --- XML encoding auto-detection
3 ;; Copyright (C) 2003, 2007-2012 Free Software Foundation, Inc.
5 ;; Author: James Clark
6 ;; Keywords: XML
8 ;; This file is part of GNU Emacs.
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 of the License, or
13 ;; (at your option) any later version.
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.
20 ;; You should have received a copy of the GNU General Public License
21 ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>.
23 ;;; Commentary:
25 ;; User entry points are nxml-start-auto-coding and
26 ;; nxml-stop-auto-coding. This is separate from nxml-mode, because
27 ;; this cannot be autoloaded. It may use
28 ;; `xmltok-get-declared-encoding-position' which can be autoloaded.
29 ;; It's separate from rng-auto.el so it can be byte-compiled, and
30 ;; because it provides independent, useful functionality.
32 ;;; Code:
34 (defvar nxml-file-name-ignore-case
35 (memq system-type '(windows-nt)))
37 (defvar nxml-cached-file-name-auto-coding-regexp nil)
38 (defvar nxml-cached-auto-mode-alist nil)
40 (defun nxml-file-name-auto-coding-regexp ()
41 "Return regexp for filenames for which XML auto-coding should be done."
42 (if (eq auto-mode-alist nxml-cached-auto-mode-alist)
43 nxml-cached-file-name-auto-coding-regexp
44 (let ((alist auto-mode-alist)
45 (case-fold-search nxml-file-name-ignore-case)
46 regexps)
47 (setq nxml-cached-auto-mode-alist alist)
48 (while alist
49 (when (eq (cdar alist) 'nxml-mode)
50 (setq regexps (cons (caar alist) regexps)))
51 (setq alist (cdr alist)))
52 (setq nxml-cached-file-name-auto-coding-regexp
53 (if (null (cdr regexps))
54 (car regexps)
55 (mapconcat (lambda (r)
56 (concat "\\(?:" r "\\)"))
57 regexps
58 "\\|"))))))
60 (defvar nxml-non-xml-set-auto-coding-function nil
61 "The function that `set-auto-coding-function' should call for non-XML files.")
62 (defun nxml-set-auto-coding (file-name size)
63 (if (let ((case-fold-search nxml-file-name-ignore-case)
64 (regexp (nxml-file-name-auto-coding-regexp)))
65 (and regexp
66 (string-match regexp file-name)))
67 (nxml-set-xml-coding file-name size)
68 (and nxml-non-xml-set-auto-coding-function
69 (funcall nxml-non-xml-set-auto-coding-function file-name size))))
71 (defun nxml-set-xml-coding (file-name size)
72 "Function to use as `set-auto-coding-function' when file is known to be XML."
73 (nxml-detect-coding-system (+ (point) (min size 1024))))
75 (declare-function xmltok-get-declared-encoding-position "xmltok"
76 (&optional limit)) ; autoloaded
78 (defun nxml-detect-coding-system (limit)
79 (if (< limit (+ (point) 2))
80 (if (eq (char-after) 0) 'no-conversion 'utf-8)
81 (let ((first-two-chars (list (char-after)
82 (char-after (1+ (point))))))
83 (cond ((equal first-two-chars '(#xFE #xFF))
84 (and (coding-system-p 'utf-16-be) 'utf-16-be))
85 ((equal first-two-chars '(#xFF #xFE))
86 (and (coding-system-p 'utf-16-le) 'utf-16-le))
87 ((memq 0 first-two-chars)
88 ;; Certainly not well-formed XML;
89 ;; perhaps UTF-16 without BOM.
90 ;; In any case, we can't handle it.
91 ;; no-conversion gives the user a chance to fix it.
92 'no-conversion)
93 ;; There are other things we might try here in the future
94 ;; eg UTF-8 BOM, UTF-16 with no BOM
95 ;; translate to EBCDIC
97 (let ((enc-pos (xmltok-get-declared-encoding-position limit)))
98 (cond ((consp enc-pos)
99 (or (nxml-mime-charset-coding-system
100 (buffer-substring-no-properties (car enc-pos)
101 (cdr enc-pos)))
102 ;; We have an encoding whose name we don't recognize.
103 ;; What to do?
104 ;; raw-text seems the best bet: since we got
105 ;; the XML decl it must be a superset of ASCII,
106 ;; so we don't need to go to no-conversion
107 'raw-text))
108 (enc-pos 'utf-8)
109 ;; invalid XML declaration
110 (t nil))))))))
112 (defun nxml-mime-charset-coding-system (charset)
113 (let ((charset-sym (intern (downcase charset)))
114 (coding-systems (coding-system-list t))
115 coding-system ret)
116 (while (and coding-systems (not ret))
117 (setq coding-system (car coding-systems))
118 (if (eq (coding-system-get coding-system 'mime-charset)
119 charset-sym)
120 (setq ret coding-system)
121 (setq coding-systems (cdr coding-systems))))
122 ret))
124 (defun nxml-start-auto-coding ()
125 "Do encoding auto-detection as specified in the XML standard.
126 Applied to any files that `auto-mode-alist' says should be handled by
127 `nxml-mode'."
128 (interactive)
129 (unless (eq set-auto-coding-function 'nxml-set-auto-coding)
130 (let ((inhibit-quit t))
131 (setq nxml-non-xml-set-auto-coding-function set-auto-coding-function)
132 (setq set-auto-coding-function 'nxml-set-auto-coding))))
134 (defun nxml-stop-auto-coding ()
135 "Stop doing encoding auto-detection as specified in the XML standard."
136 (interactive)
137 (when (eq set-auto-coding-function 'nxml-set-auto-coding)
138 (let ((inhibit-quit t))
139 (setq set-auto-coding-function nxml-non-xml-set-auto-coding-function)
140 (setq nxml-non-xml-set-auto-coding-function nil))))
142 ;; Emacs 22 makes us-ascii an alias for iso-safe without
143 ;; giving it a mime-charset property.
144 (unless (coding-system-get 'us-ascii 'mime-charset)
145 (coding-system-put 'us-ascii 'mime-charset 'us-ascii))
147 (provide 'nxml-enc)
149 ;;; nxml-enc.el ends here