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+;; @(#) xml.el --- XML parser
+
+;; Copyright (C) 2000 Free Software Foundation, Inc.
+
+;; Author: Emmanuel Briot  <briot@gnat.com>
+;; Maintainer: Emmanuel Briot <briot@gnat.com>
+;; Keywords: xml
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 2, or (at your option)
+;; any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING.  If not, write to the
+;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
+
+;;; Commentary:
+
+;; This file contains a full XML parser. It parses a file, and returns a list
+;; that can be used internally by any other lisp file.
+;; See some example in todo.el
+
+;;; FILE FORMAT
+
+;; It does not parse the DTD, if present in the XML file, but knows how to
+;; ignore it. The XML file is assumed to be well-formed. In case of error, the
+;; parsing stops and the XML file is shown where the parsing stopped.
+;;
+;; It also knows how to ignore comments, as well as the special ?xml? tag
+;; in the XML file.
+;;
+;; The XML file should have the following format:
+;;    <node1 attr1="name1" attr2="name2" ...> value
+;;       <node2 attr3="name3" attr4="name4"> value2 </node2>
+;;       <node3 attr5="name5" attr6="name6"> value3 </node3>
+;;    </node1>
+;; Of course, the name of the nodes and attributes can be anything. There can
+;; be any number of attributes (or none), as well as any number of children
+;; below the nodes.
+;;
+;; There can be only top level node, but with any number of children below.
+
+;;; LIST FORMAT
+
+;; The functions `xml-parse-file' and `xml-parse-tag' return a list with
+;; the following format:
+;;
+;;    xml-list   ::= (node node ...)
+;;    node       ::= (tag_name attribute-list . child_node_list)
+;;    child_node_list ::= child_node child_node ...
+;;    child_node ::= node | string
+;;    tag_name   ::= string
+;;    attribute_list ::= (("attribute" . "value") ("attribute" . "value") ...)
+;;                       | nil
+;;    string     ::= "..."
+;;
+;; Since XML is case insensitive, tag_name is always converted to lower-cases.
+;; tag_name is then converted to a symbol (this is not a string, so that the
+;; list takes less space in memory and is faster to traverse).
+;;
+;; Some macros are provided to ease the parsing of this list
+
+;;; Code:
+
+;;*******************************************************************
+;;**
+;;**  Macros to parse the list
+;;**
+;;*******************************************************************
+
+(defmacro xml-node-name       (node)
+  "Return the tag associated with NODE.
+The tag is a lower-case symbol."
+  (list 'car node))
+
+(defmacro xml-node-attributes (node)
+  "Return the list of attributes of NODE.
+The list can be nil."
+  (list 'nth 1 node))
+
+(defmacro xml-node-children   (node)
+  "Return the list of children of NODE.
+This is a list of nodes, and it can be nil."
+  (list 'cddr node))
+
+(defun xml-get-children (node child-name)
+  "Return the children of NODE whose tag is CHILD-NAME.
+CHILD-NAME should be a lower case symbol."
+  (let ((children (xml-node-children node))
+	match)
+    (while children
+      (if (car children)
+	  (if (equal (xml-node-name (car children)) child-name)
+	      (set 'match (append match (list (car children))))))
+      (set 'children (cdr children)))
+    match))
+
+(defun xml-get-attribute (node attribute)
+  "Get from NODE the value of ATTRIBUTE.
+An empty string is returned if the attribute was not found."
+  (if (xml-node-attributes node)
+      (let ((value (assoc attribute (xml-node-attributes node))))
+	(if value
+	    (cdr value)
+	  ""))
+    ""))
+
+;;*******************************************************************
+;;**
+;;**  Creating the list
+;;**
+;;*******************************************************************
+
+(defun xml-parse-file (file &optional parse-dtd)
+  "Parse the well-formed XML FILE.
+Returns the top node with all its children.
+If PARSE-DTD is non-nil, the DTD is parsed rather than skipped."
+  (find-file file)
+  (let ((xml (xml-parse-region (point-min)
+			       (point-max)
+			       (current-buffer)
+			       parse-dtd)))
+    (kill-buffer (current-buffer))
+    xml))
+
+(defun xml-parse-region (beg end &optional buffer parse-dtd)
+  "Parse the region from BEG to END in BUFFER.
+If BUFFER is nil, it defaults to the current buffer.
+Returns the XML list for the region, or raises an error if the region
+is not a well-formed XML file.
+If PARSE-DTD is non-nil, the DTD is parsed rather than skipped,
+and returned as the first element of the list"
+  (let (xml result dtd)
+    (save-excursion
+      (if buffer
+	  (set-buffer buffer))
+      (goto-char beg)
+      (while (< (point) end)
+	(if (search-forward "<" end t)
+	    (progn
+	      (forward-char -1)
+	      (if (null xml)
+		  (progn
+		    (set 'result (xml-parse-tag end parse-dtd))
+		    (cond
+		     ((listp (car result))
+		      (set 'dtd (car result))
+		      (add-to-list 'xml (cdr result)))
+		     (t
+		      (add-to-list 'xml result))))
+
+		;;  translation of rule [1] of XML specifications
+		(error "XML files can have only one toplevel tag.")))
+	  (goto-char end)))
+      (if parse-dtd
+	  (cons dtd (reverse xml))
+	(reverse xml)))))
+
+
+(defun xml-parse-tag (end &optional parse-dtd)
+  "Parse the tag that is just in front of point.
+The end tag must be found before the position END in the current buffer.
+If PARSE-DTD is non-nil, the DTD of the document, if any, is parsed and
+returned as the first element in the list.
+Returns one of:
+   - a list : the matching node
+   - nil    : the point is not looking at a tag.
+   - a cons cell: the first element is the DTD, the second is the node"
+  (cond
+   ;; Processing instructions (like the <?xml version="1.0"?> tag at the
+   ;; beginning of a document)
+   ((looking-at "<\\?")
+    (search-forward "?>" end)
+    (skip-chars-forward " \t\n")
+    (xml-parse-tag end))
+   ;;  Character data (CDATA) sections, in which no tag should be interpreted
+   ((looking-at "<!\\[CDATA\\[")
+    (let ((pos (match-end 0)))
+      (unless (search-forward "]]>" end t)
+	(error "CDATA section does not end anywhere in the document"))
+      (buffer-substring-no-properties pos (match-beginning 0))))
+   ;;  DTD for the document
+   ((looking-at "<!DOCTYPE")
+    (let (dtd)
+      (if parse-dtd
+	  (set 'dtd (xml-parse-dtd end))
+	(xml-skip-dtd end))
+      (skip-chars-forward " \t\n")
+      (if dtd
+	  (cons dtd (xml-parse-tag end))
+	(xml-parse-tag end))))
+   ;;  skip comments
+   ((looking-at "<!--")
+    (search-forward "-->" end)
+    (skip-chars-forward " \t\n")
+    (xml-parse-tag end))
+   ;;  end tag
+   ((looking-at "</")
+    '())
+   ;;  opening tag
+   ((looking-at "<\\([^/> \t]+\\)")
+    (let* ((node-name (match-string 1))
+	   (children (list (intern (downcase node-name))))
+	   pos)
+      (goto-char (match-end 1))
+
+      ;; parses the attribute list
+      (set 'children (append children (list (xml-parse-attlist end))))
+
+      ;; is this an empty element ?
+      (if (looking-at "/>")
+	  (progn
+	    (forward-char 2)
+	    (skip-chars-forward " \t\n")
+	    (append children '("")))
+
+	;; is this a valid start tag ?
+	(if (= (char-after) ?>)
+	    (progn
+	      (forward-char 1)
+	      (skip-chars-forward " \t\n")
+	      (while (not (looking-at (concat "</" node-name ">")))
+		(cond
+		 ((looking-at "</")
+		  (error (concat
+			  "XML: invalid syntax -- invalid end tag (expecting "
+			  node-name
+			  ")")))
+		 ((= (char-after) ?<)
+		  (set 'children (append children (list (xml-parse-tag end)))))
+		 (t
+		  (set 'pos (point))
+		  (search-forward "<" end)
+		  (forward-char -1)
+		  (let ((string (buffer-substring-no-properties pos (point)))
+			(pos 0))
+		    
+		    ;; Clean up the string (no newline characters)
+		    ;; Not done, since as per XML specifications, the XML processor
+		    ;; should always pass the whole string to the application.
+		    ;; 	    (while (string-match "\\s +" string pos)
+		    ;; 	      (set 'string (replace-match " " t t string))
+		    ;; 	      (set 'pos (1+ (match-beginning 0))))
+		    
+		    (set 'children (append children
+					   (list (xml-substitute-special string))))))))
+	      (goto-char (match-end 0))
+	      (skip-chars-forward " \t\n")
+	      (if (> (point) end)
+		  (error "XML: End tag for %s not found before end of region."
+			 node-name))
+	      children
+	      )
+
+	  ;;  This was an invalid start tag
+	  (error "XML: Invalid attribute list")
+	  ))))
+   ))
+
+(defun xml-parse-attlist (end)
+  "Return the attribute-list that point is looking at.
+The search for attributes end at the position END in the current buffer.
+Leaves the point on the first non-blank character after the tag."
+  (let ((attlist '())
+	name)
+    (skip-chars-forward " \t\n")
+    (while (looking-at "\\([a-zA-Z_:][a-zA-Z0-9.-_:]*\\)[ \t\n]*=[ \t\n]*")
+      (set 'name (intern (downcase (match-string 1))))
+      (goto-char (match-end 0))
+
+      ;; Do we have a string between quotes (or double-quotes),
+      ;;  or a simple word ?
+      (unless (looking-at "\"\\([^\"]+\\)\"")
+	(unless (looking-at "'\\([^\"]+\\)'")
+	  (error "XML: Attribute values must be given between quotes.")))
+
+      ;; Each attribute must be unique within a given element
+      (if (assoc name attlist)
+	  (error "XML: each attribute must be unique within an element."))
+      
+      (set 'attlist (append attlist
+			    (list (cons name (match-string 1)))))
+      (goto-char (match-end 0))
+      (skip-chars-forward " \t\n")
+      (if (> (point) end)
+	  (error "XML: end of attribute list not found before end of region."))
+      )
+    attlist
+    ))
+
+;;*******************************************************************
+;;**
+;;**  The DTD (document type declaration)
+;;**  The following functions know how to skip or parse the DTD of
+;;**  a document
+;;**
+;;*******************************************************************
+
+(defun xml-skip-dtd (end)
+  "Skip the DTD that point is looking at.
+The DTD must end before the position END in the current buffer.
+The point must be just before the starting tag of the DTD.
+This follows the rule [28] in the XML specifications."
+  (forward-char (length "<!DOCTYPE"))
+  (if (looking-at "[ \t\n]*>")
+      (error "XML: invalid DTD (excepting name of the document)"))
+  (condition-case nil
+      (progn
+	(forward-word 1)  ;; name of the document
+	(skip-chars-forward " \t\n")
+	(if (looking-at "\\[")
+	    (re-search-forward "\\][ \t\n]*>" end)
+	  (search-forward ">" end)))
+    (error (error "XML: No end to the DTD"))))
+
+(defun xml-parse-dtd (end)
+  "Parse the DTD that point is looking at.
+The DTD must end before the position END in the current buffer."
+  (let (dtd type element end-pos)
+    (forward-char (length "<!DOCTYPE"))
+    (skip-chars-forward " \t\n")
+    (if (looking-at ">")
+	(error "XML: invalid DTD (excepting name of the document)"))
+
+    ;;  Get the name of the document
+    (looking-at "\\sw+")
+    (set 'dtd (list 'dtd (match-string-no-properties 0)))
+    (goto-char (match-end 0))
+
+    (skip-chars-forward " \t\n")
+
+    ;;  External DTDs => don't know how to handle them yet
+    (if (looking-at "SYSTEM")
+	(error "XML: Don't know how to handle external DTDs."))
+    
+    (if (not (= (char-after) ?\[))
+	(error "XML: Unknown declaration in the DTD."))
+
+    ;;  Parse the rest of the DTD
+    (forward-char 1)
+    (while (and (not (looking-at "[ \t\n]*\\]"))
+		(<= (point) end))
+      (cond
+
+       ;;  Translation of rule [45] of XML specifications
+       ((looking-at
+	 "[\t \n]*<!ELEMENT[ \t\n]+\\([a-zA-Z0-9.%;]+\\)[ \t\n]+\\([^>]+\\)>")
+
+	(setq element (intern (downcase (match-string-no-properties 1)))
+	      type    (match-string-no-properties 2))
+	(set 'end-pos (match-end 0))
+	
+	;;  Translation of rule [46] of XML specifications
+	(cond
+	 ((string-match "^EMPTY[ \t\n]*$" type)     ;; empty declaration
+	  (set 'type 'empty))
+	 ((string-match "^ANY[ \t\n]*$" type)       ;; any type of contents
+	  (set 'type 'any))
+	 ((string-match "^(\\(.*\\))[ \t\n]*$" type) ;; children ([47])
+	  (set 'type (xml-parse-elem-type (match-string-no-properties 1 type))))
+	 ((string-match "^%[^;]+;[ \t\n]*$" type)   ;; substitution
+	  nil)
+	 (t
+	  (error "XML: Invalid element type in the DTD")))
+
+	;;  rule [45]: the element declaration must be unique
+	(if (assoc element dtd)
+	    (error "XML: elements declaration must be unique in a DTD (<%s>)."
+		   (symbol-name element)))
+	
+	;;  Store the element in the DTD
+	(set 'dtd (append dtd (list (list element type))))
+	(goto-char end-pos)
+	)
+
+
+       (t
+	(error "XML: Invalid DTD item"))
+       )
+      )
+
+    ;;  Skip the end of the DTD
+    (search-forward ">" end)
+  dtd
+  ))
+
+
+(defun xml-parse-elem-type (string)
+  "Convert a STRING for an element type into an elisp structure."
+
+  (let (elem modifier)
+    (if (string-match "(\\([^)]+\\))\\([+*?]?\\)" string)
+	(progn
+	  (setq elem     (match-string 1 string)
+		modifier (match-string 2 string))
+	  (if (string-match "|" elem)
+	      (set 'elem (append '(choice)
+			       (mapcar 'xml-parse-elem-type
+				       (split-string elem "|"))))
+	    (if (string-match "," elem)
+		(set 'elem (append '(seq)
+				 (mapcar 'xml-parse-elem-type
+					 (split-string elem ","))))
+	      )))
+      (if (string-match "[ \t\n]*\\([^+*?]+\\)\\([+*?]?\\)" string)
+	  (setq elem     (match-string 1 string)
+		modifier (match-string 2 string))))
+
+      (if (and (stringp elem)
+	       (string= elem "#PCDATA"))
+	  (set 'elem 'pcdata))
+    
+      (cond
+       ((string= modifier "+")
+	(list '+ elem))
+       ((string= modifier "*")
+	(list '* elem))
+       ((string= modifier "?")
+	(list '? elem))
+       (t
+	elem))))
+
+
+;;*******************************************************************
+;;**
+;;**  Substituting special XML sequences
+;;**
+;;*******************************************************************
+
+(defun xml-substitute-special (string)
+  "Return STRING, after subsituting special XML sequences."
+  (while (string-match "&amp;" string)
+    (set 'string (replace-match "&"  t nil string)))
+  (while (string-match "&lt;" string)
+    (set 'string (replace-match "<"  t nil string)))
+  (while (string-match "&gt;" string)
+    (set 'string (replace-match ">"  t nil string)))
+  (while (string-match "&apos;" string)
+    (set 'string (replace-match "'"  t nil string)))
+  (while (string-match "&quot;" string)
+    (set 'string (replace-match "\"" t nil string)))
+  string)
+
+;;*******************************************************************
+;;**
+;;**  Printing a tree.
+;;**  This function is intended mainly for debugging purposes.
+;;**
+;;*******************************************************************
+
+(defun xml-debug-print (xml)
+  (while xml
+    (xml-debug-print-internal (car xml) "")
+    (set 'xml (cdr xml)))
+  )
+
+(defun xml-debug-print-internal (xml &optional indent-string)
+  "Outputs the XML tree in the current buffer.
+The first line indented with INDENT-STRING."
+  (let ((tree xml)
+	attlist)
+    (unless indent-string
+      (set 'indent-string ""))
+    
+    (insert indent-string "<" (symbol-name (xml-node-name tree)))
+    
+    ;;  output the attribute list
+    (set 'attlist (xml-node-attributes tree))
+    (while attlist
+      (insert " ")
+      (insert (symbol-name (caar attlist)) "=\"" (cdar attlist) "\"")
+      (set 'attlist (cdr attlist)))
+    
+    (insert ">")
+    
+    (set 'tree (xml-node-children tree))
+
+    ;;  output the children
+    (while tree
+      (cond
+       ((listp (car tree))
+	(insert "\n")
+	(xml-debug-print-internal (car tree) (concat indent-string "  "))
+	)
+       ((stringp (car tree))
+	(insert (car tree))
+	)
+       (t
+	(error "Invalid XML tree")))
+      (set 'tree (cdr tree))
+     )
+
+    (insert "\n" indent-string
+	    "</" (symbol-name (xml-node-name xml)) ">")
+    ))
+
+(provide 'xml)
+
+;;; xml.el ends here