CODEWITHSUNDEEP
xmlc++11boost
SteveH
SteveH

Reputation: 263

How to find a node in a XML file most efficiently (C++)?

I have a XML file might contain thousands of nodes like below.

<?xml version="1.0" encoding="utf-8"?>
<root>
    <node>
        <id>0</id>
        <value>data</value>
    </node>
    <node>
        <id>1</id>
        <value>data</value>
    </node>
    <node>
        <id>2</id>
        <value>data</value>
    </node>
</<root>

Each node has its "id" which guarantees be not duplicated to each other and possibly there are gaps between them. My question is what is most efficient way by using boost to search a certain node by using node's id?

Thanks.

UPDATE This is the way I did

property_tree::wptree   ptree; // has been loaded somewhere

auto nodes = ptree.get_child(L"root");

bool bFound = false;

for (auto& itr : nodes)
{
    auto & rec = itr.second;
    int id = rec.get<int>(L"id", -1);
    if (id == nodeId)
    {
        bFound = true;
        // found it 
        //  get other values
        break;
    }
}

I do not think scanning whole the file to find an item is efficient.

Upvotes: 0

Views: 860

Answers (1)

sehe
sehe

Reputation: 393759

I've used LibXml2 with the TextReader interface.

You can continue doing xmlReaderRead and checking whether a pattern matches (xmlPatterncompile and xmlPatternMatch to see when a node is matched.

You can even get the full "DOM subtree" at that point, so you have the best of both worlds.

CAVEAT: libxml++'s wrapper of xmlReaderExpand() and similar accessors¹ are documented to leak memory. I've fixed this in our local code base. I might publish a librarified version of that on github given enough interest and permission.

All in all, this nets the same kind of interface as .NET's XpathReader: What ever happened to XPathReader

¹ so TextReader::expand()

Upvotes: 2

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