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486 lines
17 KiB
EmacsLisp
486 lines
17 KiB
EmacsLisp
;;; nxml-rap.el --- low-level support for random access parsing for nXML mode
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;; Copyright (C) 2003-2004, 2007-2012 Free Software Foundation, Inc.
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;; Author: James Clark
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;; Keywords: 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 <http://www.gnu.org/licenses/>.
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;;; Commentary:
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;; This uses xmltok.el to do XML parsing. The fundamental problem is
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;; how to handle changes. We don't want to maintain a complete parse
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;; tree. We also don't want to reparse from the start of the document
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;; on every keystroke. However, it is not possible in general to
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;; parse an XML document correctly starting at a random point in the
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;; middle. The main problems are comments, CDATA sections and
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;; processing instructions: these can all contain things that are
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;; indistinguishable from elements. Literals in the prolog are also a
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;; problem. Attribute value literals are not a problem because
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;; attribute value literals cannot contain less-than signs.
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;;
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;; Our strategy is to keep track of just the problematic things.
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;; Specifically, we keep track of all comments, CDATA sections and
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;; processing instructions in the instance. We do this by marking all
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;; except the first character of these with a non-nil nxml-inside text
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;; property. The value of the nxml-inside property is comment,
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;; cdata-section or processing-instruction. The first character does
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;; not have the nxml-inside property so we can find the beginning of
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;; the construct by looking for a change in a text property value
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;; (Emacs provides primitives for this). We use text properties
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;; rather than overlays, since the implementation of overlays doesn't
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;; look like it scales to large numbers of overlays in a buffer.
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;;
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;; We don't in fact track all these constructs, but only track them in
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;; some initial part of the instance. The variable `nxml-scan-end'
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;; contains the limit of where we have scanned up to for them.
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;;
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;; Thus to parse some random point in the file we first ensure that we
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;; have scanned up to that point. Then we search backwards for a
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;; <. Then we check whether the < has an nxml-inside property. If it
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;; does we go backwards to first character that does not have an
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;; nxml-inside property (this character must be a <). Then we start
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;; parsing forward from the < we have found.
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;;
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;; The prolog has to be parsed specially, so we also keep track of the
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;; end of the prolog in `nxml-prolog-end'. The prolog is reparsed on
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;; every change to the prolog. This won't work well if people try to
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;; edit huge internal subsets. Hopefully that will be rare.
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;;
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;; We keep track of the changes by adding to the buffer's
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;; after-change-functions hook. Scanning is also done as a
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;; prerequisite to fontification by adding to fontification-functions
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;; (in the same way as jit-lock). This means that scanning for these
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;; constructs had better be quick. Fortunately it is. Firstly, the
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;; typical proportion of comments, CDATA sections and processing
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;; instructions is small relative to other things. Secondly, to scan
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;; we just search for the regexp <[!?].
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;;
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;; One problem is unclosed comments, processing instructions and CDATA
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;; sections. Suppose, for example, we encounter a <!-- but there's no
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;; matching -->. This is not an unexpected situation if the user is
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;; creating a comment. It is not helpful to treat the whole of the
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;; file starting from the <!-- onwards as a single unclosed comment
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;; token. Instead we treat just the <!-- as a piece of not well-formed
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;; markup and continue. The problem is that if at some later stage a
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;; --> gets added to the buffer after the unclosed <!--, we will need
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;; to reparse the buffer starting from the <!--. We need to keep
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;; track of these reparse dependencies; they are called dependent
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;; regions in the code.
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;;; Code:
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(require 'xmltok)
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(require 'nxml-util)
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(defvar nxml-prolog-end nil
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"Integer giving position following end of the prolog.")
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(make-variable-buffer-local 'nxml-prolog-end)
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(defvar nxml-scan-end nil
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"Marker giving position up to which we have scanned.
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nxml-scan-end must be >= nxml-prolog-end. Furthermore, nxml-scan-end
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must not be an inside position in the following sense. A position is
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inside if the following character is a part of, but not the first
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character of, a CDATA section, comment or processing instruction.
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Furthermore all positions >= nxml-prolog-end and < nxml-scan-end that
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are inside positions must have a non-nil `nxml-inside' property whose
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value is a symbol specifying what it is inside. Any characters with a
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non-nil `fontified' property must have position < nxml-scan-end and
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the correct face. Dependent regions must also be established for any
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unclosed constructs starting before nxml-scan-end.
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There must be no `nxml-inside' properties after nxml-scan-end.")
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(make-variable-buffer-local 'nxml-scan-end)
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(defsubst nxml-get-inside (pos)
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(get-text-property pos 'nxml-inside))
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(defsubst nxml-clear-inside (start end)
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(nxml-debug-clear-inside start end)
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(remove-text-properties start end '(nxml-inside nil)))
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(defsubst nxml-set-inside (start end type)
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(nxml-debug-set-inside start end)
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(put-text-property start end 'nxml-inside type))
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(defun nxml-inside-end (pos)
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"Return the end of the inside region containing POS.
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Return nil if the character at POS is not inside."
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(if (nxml-get-inside pos)
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(or (next-single-property-change pos 'nxml-inside)
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(point-max))
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nil))
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(defun nxml-inside-start (pos)
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"Return the start of the inside region containing POS.
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Return nil if the character at POS is not inside."
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(if (nxml-get-inside pos)
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(or (previous-single-property-change (1+ pos) 'nxml-inside)
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(point-min))
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nil))
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;;; Change management
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(defun nxml-scan-after-change (start end)
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"Restore `nxml-scan-end' invariants after a change.
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The change happened between START and END.
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Return position after which lexical state is unchanged.
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END must be > `nxml-prolog-end'. START must be outside
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any 'inside' regions and at the beginning of a token."
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(if (>= start nxml-scan-end)
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nxml-scan-end
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(let ((inside-remove-start start)
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xmltok-errors
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xmltok-dependent-regions)
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(while (or (when (xmltok-forward-special (min end nxml-scan-end))
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(when (memq xmltok-type
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'(comment
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cdata-section
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processing-instruction))
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(nxml-clear-inside inside-remove-start
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(1+ xmltok-start))
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(nxml-set-inside (1+ xmltok-start)
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(point)
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xmltok-type)
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(setq inside-remove-start (point)))
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(if (< (point) (min end nxml-scan-end))
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t
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(setq end (point))
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nil))
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;; The end of the change was inside but is now outside.
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;; Imagine something really weird like
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;; <![CDATA[foo <!-- bar ]]> <![CDATA[ stuff --> <!-- ]]> -->
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;; and suppose we deleted "<![CDATA[f"
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(let ((inside-end (nxml-inside-end end)))
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(when inside-end
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(setq end inside-end)
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t))))
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(nxml-clear-inside inside-remove-start end)
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(nxml-clear-dependent-regions start end)
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(nxml-mark-parse-dependent-regions))
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(when (> end nxml-scan-end)
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(set-marker nxml-scan-end end))
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end))
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;; n-s-p only called from nxml-mode.el, where this variable is defined.
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(defvar nxml-prolog-regions)
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(defun nxml-scan-prolog ()
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(goto-char (point-min))
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(let (xmltok-dtd
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xmltok-errors
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xmltok-dependent-regions)
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(setq nxml-prolog-regions (xmltok-forward-prolog))
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(setq nxml-prolog-end (point))
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(nxml-clear-inside (point-min) nxml-prolog-end)
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(nxml-clear-dependent-regions (point-min) nxml-prolog-end)
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(nxml-mark-parse-dependent-regions))
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(when (< nxml-scan-end nxml-prolog-end)
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(set-marker nxml-scan-end nxml-prolog-end)))
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;;; Dependent regions
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(defun nxml-adjust-start-for-dependent-regions (start end pre-change-length)
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(let ((overlays (overlays-in (1- start) start))
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(adjusted-start start))
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(while overlays
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(let* ((overlay (car overlays))
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(ostart (overlay-start overlay)))
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(when (and (eq (overlay-get overlay 'category) 'nxml-dependent)
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(< ostart adjusted-start))
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(let ((funargs (overlay-get overlay 'nxml-funargs)))
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(when (apply (car funargs)
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(append (list start
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end
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pre-change-length
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ostart
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(overlay-end overlay))
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(cdr funargs)))
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(setq adjusted-start ostart)))))
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(setq overlays (cdr overlays)))
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adjusted-start))
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(defun nxml-mark-parse-dependent-regions ()
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(while xmltok-dependent-regions
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(apply 'nxml-mark-parse-dependent-region
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(car xmltok-dependent-regions))
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(setq xmltok-dependent-regions
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(cdr xmltok-dependent-regions))))
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(defun nxml-mark-parse-dependent-region (fun start end &rest args)
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(let ((overlay (make-overlay start end nil t t)))
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(overlay-put overlay 'category 'nxml-dependent)
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(overlay-put overlay 'nxml-funargs (cons fun args))))
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(put 'nxml-dependent 'evaporate t)
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(defun nxml-clear-dependent-regions (start end)
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(let ((overlays (overlays-in start end)))
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(while overlays
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(let* ((overlay (car overlays))
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(category (overlay-get overlay 'category)))
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(when (and (eq category 'nxml-dependent)
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(<= start (overlay-start overlay)))
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(delete-overlay overlay)))
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(setq overlays (cdr overlays)))))
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;;; Random access parsing
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(defun nxml-token-after ()
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"Return the position after the token containing the char after point.
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Sets up the variables `xmltok-type', `xmltok-start',
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`xmltok-name-end', `xmltok-name-colon', `xmltok-attributes',
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`xmltok-namespace-attributes' in the same was as does
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`xmltok-forward'. The prolog will be treated as a single token with
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type `prolog'."
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(let ((pos (point)))
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(if (< pos nxml-prolog-end)
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(progn
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(setq xmltok-type 'prolog
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xmltok-start (point-min))
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(min nxml-prolog-end (point-max)))
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(nxml-ensure-scan-up-to-date)
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(if (nxml-get-inside pos)
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(save-excursion
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(nxml-move-outside-backwards)
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(xmltok-forward)
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(point))
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(save-excursion
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(if (or (eq (char-after) ?<)
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(search-backward "<"
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(max (point-min) nxml-prolog-end)
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t))
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(nxml-move-outside-backwards)
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(goto-char (if (<= (point-min) nxml-prolog-end)
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nxml-prolog-end
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(or (nxml-inside-end (point-min))
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(point-min)))))
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(while (and (nxml-tokenize-forward)
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(<= (point) pos)))
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(point))))))
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(defun nxml-token-before ()
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"Return the position after the token containing the char before point.
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Sets variables like `nxml-token-after'."
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(if (/= (point-min) (point))
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(save-excursion
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(goto-char (1- (point)))
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(nxml-token-after))
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(setq xmltok-start (point))
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(setq xmltok-type nil)
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(point)))
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(defun nxml-tokenize-forward ()
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(let (xmltok-dependent-regions
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xmltok-errors)
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(when (and (xmltok-forward)
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(> (point) nxml-scan-end))
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(cond ((memq xmltok-type '(comment
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cdata-section
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processing-instruction))
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(nxml-with-unmodifying-text-property-changes
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(nxml-set-inside (1+ xmltok-start) (point) xmltok-type)))
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(xmltok-dependent-regions
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(nxml-mark-parse-dependent-regions)))
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(set-marker nxml-scan-end (point)))
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xmltok-type))
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(defun nxml-move-tag-backwards (bound)
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"Move point backwards outside any 'inside' regions or tags.
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Point will not move past `nxml-prolog-end'.
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Point will either be at BOUND or a '<' character starting a tag
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outside any 'inside' regions. Ignores dependent regions.
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As a precondition, point must be >= BOUND."
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(nxml-move-outside-backwards)
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(when (not (equal (char-after) ?<))
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(if (search-backward "<" bound t)
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(progn
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(nxml-move-outside-backwards)
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(when (not (equal (char-after) ?<))
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(search-backward "<" bound t)))
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(goto-char bound))))
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(defun nxml-move-outside-backwards ()
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"Move point to first character of the containing special thing.
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Leave point unmoved if it is not inside anything special."
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(let ((start (nxml-inside-start (point))))
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(when start
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(goto-char (1- start))
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(when (nxml-get-inside (point))
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(error "Char before inside-start at %s had nxml-inside property %s"
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(point)
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(nxml-get-inside (point)))))))
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(defun nxml-ensure-scan-up-to-date ()
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(let ((pos (point)))
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(when (< nxml-scan-end pos)
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(save-excursion
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(goto-char nxml-scan-end)
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(let (xmltok-errors
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xmltok-dependent-regions)
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(while (when (xmltok-forward-special pos)
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(when (memq xmltok-type
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'(comment
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processing-instruction
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cdata-section))
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(nxml-with-unmodifying-text-property-changes
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(nxml-set-inside (1+ xmltok-start)
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(point)
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xmltok-type)))
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(if (< (point) pos)
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t
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(setq pos (point))
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nil)))
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(nxml-clear-dependent-regions nxml-scan-end pos)
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(nxml-mark-parse-dependent-regions)
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(set-marker nxml-scan-end pos))))))
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;;; Element scanning
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(defun nxml-scan-element-forward (from &optional up)
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"Scan forward from FROM over a single balanced element.
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Point must be between tokens. Return the position of the end of
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the tag that ends the element. `xmltok-start' will contain the
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position of the start of the tag. If UP is non-nil, then scan
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past end-tag of element containing point. If no element is
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found, return nil. If a well-formedness error prevents scanning,
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signal an `nxml-scan-error'. Point is not moved."
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(let ((open-tags (and up t))
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found)
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(save-excursion
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(goto-char from)
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(while (cond ((not (nxml-tokenize-forward))
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(when (consp open-tags)
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(nxml-scan-error (cadr open-tags)
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"Start-tag has no end-tag"))
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nil)
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((eq xmltok-type 'start-tag)
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(setq open-tags
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(cons (xmltok-start-tag-qname)
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(cons xmltok-start
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open-tags)))
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t)
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((eq xmltok-type 'end-tag)
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(cond ((not open-tags) nil)
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((not (consp open-tags)) (setq found (point)) nil)
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((not (string= (car open-tags)
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(xmltok-end-tag-qname)))
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(nxml-scan-error (+ 2 xmltok-start)
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"Mismatched end-tag; \
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expected `%s'"
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(car open-tags)))
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((setq open-tags (cddr open-tags)) t)
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(t (setq found (point)) nil)))
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((memq xmltok-type '(empty-element
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partial-empty-element))
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(if open-tags
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t
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(setq found (point))
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nil))
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((eq xmltok-type 'partial-end-tag)
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(cond ((not open-tags) nil)
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((not (consp open-tags)) (setq found (point)) nil)
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((setq open-tags (cddr open-tags)) t)
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(t (setq found (point)) nil)))
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((eq xmltok-type 'partial-start-tag)
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(nxml-scan-error xmltok-start
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"Missing `>'"))
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(t t))))
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found))
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(defun nxml-scan-element-backward (from &optional up bound)
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"Scan backward from FROM over a single balanced element.
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Point must be between tokens. Return the position of the end of
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the tag that starts the element. `xmltok-start' will contain the
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position of the start of the tag. If UP is non-nil, then scan
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past start-tag of element containing point. If BOUND is non-nil,
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then don't scan back past BOUND. If no element is found, return
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nil. If a well-formedness error prevents scanning, signal an
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`nxml-scan-error'. Point is not moved."
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(let ((open-tags (and up t))
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token-end found)
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(save-excursion
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(goto-char from)
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(while (cond ((or (< (point) nxml-prolog-end)
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(not (search-backward "<"
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(max (or bound 0)
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nxml-prolog-end)
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t)))
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(when (and (consp open-tags) (not bound))
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(nxml-scan-error (cadr open-tags)
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"End-tag has no start-tag"))
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nil)
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((progn
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(nxml-move-outside-backwards)
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(save-excursion
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(nxml-tokenize-forward)
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(setq token-end (point)))
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(eq xmltok-type 'end-tag))
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(setq open-tags
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(cons (xmltok-end-tag-qname)
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(cons xmltok-start open-tags)))
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t)
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((eq xmltok-type 'start-tag)
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(cond ((not open-tags) nil)
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((not (consp open-tags))
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(setq found token-end)
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nil)
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((and (car open-tags)
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(not (string= (car open-tags)
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(xmltok-start-tag-qname))))
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(nxml-scan-error (1+ xmltok-start)
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"Mismatched start-tag; \
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expected `%s'"
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(car open-tags)))
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((setq open-tags (cddr open-tags)) t)
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(t (setq found token-end) nil)))
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((memq xmltok-type '(empty-element
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partial-empty-element))
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(if open-tags
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t
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(setq found token-end)
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nil))
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((eq xmltok-type 'partial-end-tag)
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(setq open-tags
|
|
(cons nil (cons xmltok-start open-tags)))
|
|
t)
|
|
((eq xmltok-type 'partial-start-tag)
|
|
;; if we have only a partial-start-tag
|
|
;; then it's unlikely that there's a matching
|
|
;; end-tag, so it's probably not helpful
|
|
;; to treat it as a complete start-tag
|
|
(nxml-scan-error xmltok-start
|
|
"Missing `>'"))
|
|
(t t))))
|
|
found))
|
|
|
|
(defun nxml-scan-error (&rest args)
|
|
(signal 'nxml-scan-error args))
|
|
|
|
(put 'nxml-scan-error
|
|
'error-conditions
|
|
'(error nxml-error nxml-scan-error))
|
|
|
|
(put 'nxml-scan-error
|
|
'error-message
|
|
"Scan over element that is not well-formed")
|
|
|
|
(provide 'nxml-rap)
|
|
|
|
;;; nxml-rap.el ends here
|