CODEWITHSUNDEEP
c++xmlpugixml
nurabha
nurabha

Reputation: 1212

Saving sub-tree of PUGI XML tree in a pugi xml_node

In a function, I use pugi to first load an XML file. I then traverse the child xml nodes of the tree and push some of the child xml nodes (objects of type xml_node) to a vector of xml_node. But as soon as I exit this function, the original XML tree structure object loaded from the XML file is deleted causing elements in vector of xml nodes to become invalid.

Below is a sample code(written quickly) to show this:

#include "pugixml.hpp"
#include <vector>

void ProcessXmlDeferred(  std::vector<pugi::xml_node> const &subTrees )
{
   for( auto & const node: subTrees)
   {
       // parse each xml_node node
   }
}

void IntermedProcXml( pugi::xml_node const &node)
{
   // parse node
}

std::vector<pugi::xml_node> BuildSubTrees(pugi::xml_node const & node )
{
  std::vector<pugi::xml_node> subTrees;

  pugi::xml_node temp = node.child("L1");
  subTrees.push_back( temp );

  temp = node.child.child("L2");
  subTrees.push_back( temp );

  temp = node.child.child.child("L3");
  subTrees.push_back( temp );

  return subTrees;
}

void LoadAndProcessDoc( const char* fileNameWithPath, std::vector<pugi::xml_node> & subTrees )
{
    pugi::xml_document doc;
    pugi::xml_parse_result result = doc.load( fileNameWithPath );

    subTrees = BuildSubTrees( result.child("TOP") );
    IntermedProcXml( result.child("CENTRE") );

    // Local pugi objects("doc" and "result") destroyed at exit of this 
    // function invalidating contents of xml nodes inside vector "subTrees"
}


int main()
{
    char fileName[] = "myFile.xml";
    std::vector<pugi::xml_node> myXmlSubTrees;  

    // Load XML file and return vector of XML sub-tree's for later parsing
    LoadAndProcessDoc( fileName, myXmlSubTrees );

    // At this point, the contents of xml node's inside the vector  
    // "myXmlSubTrees" are no longer valid and thus are unsafe to use

    // ....
    // Lots of intermediate code
    // ....

    // This function tries to process vector whose xml nodes 
    // are invalid and thus throws errors
    ProcessXmlDeferred( myXmlSubTrees );

    return 0;
}

I therefore need a way to save/copy/clone/move sub-tree's(xml nodes) of my original XML tree such that I can safely parse them at a later point even after the original XML root tree object is deleted. How to do this in pugi ?

Upvotes: 1

Views: 1567

Answers (1)

zeuxcg
zeuxcg

Reputation: 9404

Just pass the ownership of the xml_document object to the caller.

You can either do it by forcing the caller to supply an xml_document object (add a xml_document& argument to the function), or by returning a shared_ptr<xml_document> or unique_ptr<xml_document> from the function alongside the node vector.

Upvotes: 1

Related Questions