150 lines
5.5 KiB
EmacsLisp
150 lines
5.5 KiB
EmacsLisp
;;; nxml-enc.el --- XML encoding auto-detection -*- lexical-binding:t -*-
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;; Copyright (C) 2003, 2007-2024 Free Software Foundation, Inc.
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;; Author: James Clark
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;; Keywords: text, hypermedia, languages, XML
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;; This file is part of GNU Emacs.
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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
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;; (at your option) any later version.
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;; GNU Emacs is distributed in the hope that it will be useful,
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;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;; GNU General Public License for more details.
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;; You should have received a copy of the GNU General Public License
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;; along with GNU Emacs. If not, see <https://www.gnu.org/licenses/>.
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;;; Commentary:
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;; User entry points are nxml-start-auto-coding and
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;; nxml-stop-auto-coding. This is separate from nxml-mode, because
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;; this cannot be autoloaded. It may use
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;; `xmltok-get-declared-encoding-position' which can be autoloaded.
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;; It's separate from rng-auto.el so it can be byte-compiled, and
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;; because it provides independent, useful functionality.
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;;; Code:
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(defvar nxml-file-name-ignore-case
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(memq system-type '(windows-nt)))
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(defvar nxml-cached-file-name-auto-coding-regexp nil)
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(defvar nxml-cached-auto-mode-alist nil)
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(defun nxml-file-name-auto-coding-regexp ()
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"Return regexp for filenames for which XML auto-coding should be done."
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(if (eq auto-mode-alist nxml-cached-auto-mode-alist)
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nxml-cached-file-name-auto-coding-regexp
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(let ((alist auto-mode-alist)
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(case-fold-search nxml-file-name-ignore-case)
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regexps)
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(setq nxml-cached-auto-mode-alist alist)
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(while alist
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(when (eq (cdar alist) 'nxml-mode)
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(setq regexps (cons (caar alist) regexps)))
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(setq alist (cdr alist)))
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(setq nxml-cached-file-name-auto-coding-regexp
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(if (null (cdr regexps))
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(car regexps)
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(mapconcat (lambda (r)
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(concat "\\(?:" r "\\)"))
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regexps
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"\\|"))))))
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(defvar nxml-non-xml-set-auto-coding-function nil
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"The function that `set-auto-coding-function' should call for non-XML files.")
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(defun nxml-set-auto-coding (file-name size)
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(if (let ((case-fold-search nxml-file-name-ignore-case)
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(regexp (nxml-file-name-auto-coding-regexp)))
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(and regexp
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(string-match regexp file-name)))
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(nxml-set-xml-coding file-name size)
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(and nxml-non-xml-set-auto-coding-function
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(funcall nxml-non-xml-set-auto-coding-function file-name size))))
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(defun nxml-set-xml-coding (_file-name size)
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"Function to use as `set-auto-coding-function' when file is known to be XML."
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(nxml-detect-coding-system (+ (point) (min size 1024))))
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(declare-function xmltok-get-declared-encoding-position "xmltok"
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(&optional limit)) ; autoloaded
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(defun nxml-detect-coding-system (limit)
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(if (< limit (+ (point) 2))
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(if (eq (char-after) 0) 'no-conversion 'utf-8)
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(let ((first-two-chars (list (char-after)
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(char-after (1+ (point))))))
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(cond ((equal first-two-chars '(#xFE #xFF))
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(and (coding-system-p 'utf-16-be) 'utf-16-be))
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((equal first-two-chars '(#xFF #xFE))
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(and (coding-system-p 'utf-16-le) 'utf-16-le))
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((memq 0 first-two-chars)
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;; Certainly not well-formed XML;
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;; perhaps UTF-16 without BOM.
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;; In any case, we can't handle it.
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;; no-conversion gives the user a chance to fix it.
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'no-conversion)
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;; There are other things we might try here in the future
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;; eg UTF-8 BOM, UTF-16 with no BOM
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;; translate to EBCDIC
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(t
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(let ((enc-pos (xmltok-get-declared-encoding-position limit)))
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(cond ((consp enc-pos)
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(or (nxml-mime-charset-coding-system
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(buffer-substring-no-properties (car enc-pos)
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(cdr enc-pos)))
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;; We have an encoding whose name we don't recognize.
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;; What to do?
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;; raw-text seems the best bet: since we got
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;; the XML decl it must be a superset of ASCII,
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;; so we don't need to go to no-conversion
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'raw-text))
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(enc-pos 'utf-8)
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;; invalid XML declaration
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(t nil))))))))
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(defun nxml-mime-charset-coding-system (charset)
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(let ((charset-sym (intern (downcase charset)))
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(coding-systems (coding-system-list t))
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coding-system ret)
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(while (and coding-systems (not ret))
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(setq coding-system (car coding-systems))
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(if (eq (coding-system-get coding-system 'mime-charset)
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charset-sym)
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(setq ret coding-system)
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(setq coding-systems (cdr coding-systems))))
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ret))
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(defun nxml-start-auto-coding ()
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"Do encoding auto-detection as specified in the XML standard.
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Applied to any files that `auto-mode-alist' says should be handled by
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`nxml-mode'."
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(interactive)
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(unless (eq set-auto-coding-function 'nxml-set-auto-coding)
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(let ((inhibit-quit t))
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(setq nxml-non-xml-set-auto-coding-function set-auto-coding-function)
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(setq set-auto-coding-function 'nxml-set-auto-coding))))
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(defun nxml-stop-auto-coding ()
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"Stop doing encoding auto-detection as specified in the XML standard."
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(interactive)
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(when (eq set-auto-coding-function 'nxml-set-auto-coding)
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(let ((inhibit-quit t))
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(setq set-auto-coding-function nxml-non-xml-set-auto-coding-function)
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(setq nxml-non-xml-set-auto-coding-function nil))))
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;; Emacs 22 makes us-ascii an alias for iso-safe without
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;; giving it a mime-charset property.
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(unless (coding-system-get 'us-ascii 'mime-charset)
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(coding-system-put 'us-ascii 'mime-charset 'us-ascii))
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(provide 'nxml-enc)
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;;; nxml-enc.el ends here
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