xmlutil::Document employes mutexes now to lock data

This is very unlikely to be waterproof, since it's still possible to
hold stale xmlutil::Node objects, but it seems to prevent the crashes
during startup at least.

libs/xmlutil/Document.cpp

@@ -21,8 +21,10 @@ Document::Document(const Document& other) :
 	_xmlDoc(other._xmlDoc)
 {}
 
-Document::~Document() {
-	if (_xmlDoc != NULL) {
+Document::~Document() 
+{
+	if (_xmlDoc != nullptr)
+	{
 		// Free the xml document memory
 		xmlFreeDoc(_xmlDoc);
 	}
@@ -40,7 +42,10 @@ Document Document::create()
 	return Document(doc);
 }
 
-void Document::addTopLevelNode(const std::string& name) {
+void Document::addTopLevelNode(const std::string& name)
+{
+	std::lock_guard<std::mutex> lock(_lock);
+
 	if (!isValid()) {
 		return; // is not Valid, place an assertion here?
 	}
@@ -62,8 +67,10 @@ void Document::addTopLevelNode(const std::string& name) {
 	xmlFree(emptyStr);
 }
 
-Node Document::getTopLevelNode() const {
-	if (!isValid()) {
+Node Document::getTopLevelNode() const
+{
+	if (!isValid())
+	{
 		// Invalid Document, return a NULL node
 		return Node(NULL);
 	}
@@ -73,6 +80,8 @@ Node Document::getTopLevelNode() const {
 
 void Document::importDocument(Document& other, Node& importNode)
 {
+	std::lock_guard<std::mutex> lock(_lock);
+
 	// Locate the top-level node(s) of the other document
 	xml::NodeList topLevelNodes = other.findXPath("/*");
 
@@ -102,27 +111,35 @@ void Document::importDocument(Document& other, Node& importNode)
 	}
 }
 
-void Document::copyNodes(const NodeList& nodeList) {
-	if (!isValid() || _xmlDoc->children == NULL) {
+void Document::copyNodes(const NodeList& nodeList)
+{
+	std::lock_guard<std::mutex> lock(_lock);
+
+	if (!isValid() || _xmlDoc->children == NULL)
+	{
 		return; // is not Valid, place an assertion here?
 	}
 
 	// Copy the child nodes one by one
-	for (std::size_t i = 0; i < nodeList.size(); i++) {
+	for (std::size_t i = 0; i < nodeList.size(); i++)
+	{
 		// Copy the node
 		xmlNodePtr node = xmlCopyNode(nodeList[i].getNodePtr(), 1);
 		// Add this node to the top level node of this document
 		xmlAddChild(xmlDocGetRootElement(_xmlDoc), node);
 	}
 }
 
-bool Document::isValid() const {
-	return _xmlDoc != NULL;
+bool Document::isValid() const
+{
+	return _xmlDoc != nullptr;
 }
 
 // Evaluate an XPath expression and return matching Nodes.
 NodeList Document::findXPath(const std::string& path) const
 {
+	std::lock_guard<std::mutex> lock(_lock);
+
     // Set up the XPath context
     xmlXPathContextPtr context = xmlXPathNewContext(_xmlDoc);
 
@@ -158,7 +175,10 @@ NodeList Document::findXPath(const std::string& path) const
 }
 
 // Saves the file to the disk via xmlSaveFormatFile
-void Document::saveToFile(const std::string& filename) const {
+void Document::saveToFile(const std::string& filename) const
+{
+	std::lock_guard<std::mutex> lock(_lock);
+
 	xmlSaveFormatFile(filename.c_str(), _xmlDoc, 1);
 }
 

libs/xmlutil/Document.h

@@ -1,8 +1,9 @@
-#ifndef DOCUMENT_H_
-#define DOCUMENT_H_
+#pragma once
 
 #include "Node.h"
 
+#include <mutex>
+
 typedef struct _xmlDoc xmlDoc;
 typedef xmlDoc *xmlDocPtr;
 
@@ -23,10 +24,11 @@ namespace xml
 class Document
 {
 private:
-
-    // Contained xmlDocPtr.
+	// Contained xmlDocPtr.
     xmlDocPtr _xmlDoc;
 
+	mutable std::mutex _lock;
+
 public:
     // Construct a Document using the provided xmlDocPtr.
 	Document(xmlDocPtr doc);
@@ -70,5 +72,3 @@ class Document
 };
 
 }
-
-#endif /*DOCUMENT_H_*/