Deep Copy an XML via TinyXML

问题

I am using tinyxml.

How do I duplicate or create a copy of an existing XMLDocument?

http://www.grinninglizard.com/tinyxmldocs/classTiXmlDocument.html#a4e8c1498a76dcde7191c683e1220882

I went through this link that says using Clone to replicate a node. But this is protected and I do not want to go for deriving a class out of this and the like.

I also do not want to save the existing XMLDocument to a file and then making another XMLDocument object read the file to have a copy of it.

I am also not able to perform a deep copy using memcpy because I am unaware of the size of the entire XML.

I also do not want to having two objects being used one after the other like:

XMLDocumentObj1 = add_some_data

XMLDocumentObj2 = add_the_same_data, and so on

The primary reason I want a second copy is that, the first might be modified by different sections of the code, while the same copy is being 'read' at multiple places. I need to ensure that there occur no errors when XMLDocument is read, because there are chances that this might have been modified in the background by a running thread, and I get no program crashes.

回答1:

Here is something I wrote to do a deep copy. It takes the source node and copies it under the destination node, children and all. Memory is taken from the destination node's context. Hopefully, it's a start in the right direction for you.

void CopyNode(tinyxml2::XMLNode *p_dest_parent, const tinyxml2::XMLNode *p_src)
{
    // Protect from evil
    if (p_dest_parent == NULL || p_src == NULL)
    {
        return;
    }

    // Get the document context where new memory will be allocated from
    tinyxml2::XMLDocument *p_doc = p_dest_parent->GetDocument();

    // Make the copy
    tinyxml2::XMLNode *p_copy = p_src->ShallowClone(p_doc);
    if (p_copy == NULL)
    {
        // Error handling required (e.g. throw)
        return;
    }

    // Add this child
    p_dest_parent->InsertEndChild(p_copy);

    // Add the grandkids
    for (const tinyxml2::XMLNode *p_node = p_src->FirstChild(); p_node != NULL; p_node = p_node->NextSibling())
    {
        CopyNode(p_copy, p_node);
    }
}

回答2:

I found this and i think this may help you.

https://github.com/leethomason/tinyxml2/blob/master/xmltest.cpp

const char* pub = "<?xml version='1.0'?> <element><sub/></element> <!--comment--> <!DOCTYPE>";
XMLDocument doc;
doc.Parse( pub );

XMLDocument clone;
for( const XMLNode* node=doc.FirstChild(); node; node=node->NextSibling() ) {
    XMLNode* copy = node->ShallowClone( &clone );
    clone.InsertEndChild( copy );
}

clone.Print();

int count=0;
const XMLNode* a=clone.FirstChild();
const XMLNode* b=doc.FirstChild();
for( ; a && b; a=a->NextSibling(), b=b->NextSibling() ) {
    ++count;
    XMLTest( "Clone and Equal", true, a->ShallowEqual( b ));
}
XMLTest( "Clone and Equal", 4, count );

来源：https://stackoverflow.com/questions/30230111/deep-copy-an-xml-via-tinyxml

标签

c++

xml

tinyxml