Find a line (and column) of xml_node in rapidxml

Question

From what I could understand in the docs I deducted every xml_node knows it's position in the source text. What I'd like to do is to retrieve LINE and COLUMN for given xml_node<>*:

    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 << "My first node is: <" << main->name() << ">\n";
    cout << "   located at line " << main->?????() << ", column " << main->?????() << "\n";

How should I retrieve those offsets? Could I somehow crawl from the main->name() pointer back to the beginning of the document? But how can I access the document string from xml_document<> doc to compare offsets?

Answer 1

Let's say you parse a simple xml document in a string.

char xml[] = "<hello/><world/>"

doc.parse(xml);

RapidXML will insert null terminators (and maybe make other mods to the "document", so it might look like this now:

char xml[] = "<hello\000\000<world\000\000";

If you than ask for the name() of the 'hello' node, it returns a pointer to the 'h' in your xml array. You can just subtract the base of the array to get an offset.

int offset = node->name() - &xml[0];

Obviously this isn't line and character. To get that, you'd need to count the number of newlines between the offset and the array start. (but maybe do this on a 'clean' version of the xml data, as RapidXML might well mangle newline sequences in the processed version..