Get child count from rapidxml:xmlnode to get random child node

Question

I can turn my XML document file into rapidxml object:

if(exists("generators.xml")) { //http://stackoverflow.com/a/12774387/607407
    rapidxml::file<> xmlFile("generators.xml"); // Open file, default template is char

    xml_document<> doc;               // character type defaults to char
    doc.parse<0>(xmlFile.data());;    // 0 means default parse flags
    xml_node<> *main = doc.first_node();  //Get the main node that contains everything
    cout << "Name of my first node is: " << doc.first_node()->name() << "\n";

    if(main!=NULL) {
        //Get random child node?
    }
}

I'd like to pick one random child node from the main object. My XML looks like this (version with comments):

<?xml version="1.0" encoding="windows-1250"?>
<Stripes>
  <Generator>
     <stripe h="0,360" s="255,255" l="50,80" width="10,20" />
  </Generator>
  <Generator>
     <loop>
       <stripe h="0,360" s="255,255" l="50,80" width="10,20" />
       <stripe h="0,360" s="255,255" l="0,0" width="10,20" />
     </loop>
  </Generator>
</Stripes>

I want to pick random <Generator> entry. I think getting the child count would be a way to do it:

//Fictional code - **all** methods are fictional!
unsigned int count = node->child_count();
//In real code, `rand` is not a good way to get anything random
xmlnode<> *child = node->childAt(rand(0, count));

How can I get child count and child at offset from rapidxml node?

Answer 1

RapidXML stores the DOM tree using linked lists, which as you'll know are not directly indexable.

So you'd basically need to implement those two methods yourself, by traversing the nodes children. Something like this (untested) code.

int getChildCount(xmlnode<> *n)
{
  int c = 0;
  for (xmlnode<> *child = n->first_node(); child != NULL; child = child->next_sibling())
  {
    c++;
  } 
  return c;
} 

getChildAt is obviously similar.