Oh crap...
I forgot one line in the code. Fixed code below.
DOMNode* pNode = m_pDocument->getDocumentElement()->getFirstChild();
while (pNode) {
if (pNode->getNodeType() == DOM_NODE && equal(pNode->getNodeName(),
"PatchData")) {
DOMNode* pInnerNode = pNode->getFirstChild();
while (pInnerNode) {
if (pInnerNode->getNodeType() == DOM_NODE &&
equal(pInnerNode->getNodeName(), "CbName")) {
if (equal(pInnerNode->getNodeValue(), "your searchstring "))
// Bingo!!! We found it, process node
break; // No need to search for more inner nodes
}
}
pInnerNode = pInnerNode->getNextSibling(); // <-- this one
}
}
pNode = pNode->getNextSibling();
}
/ Erik
> -----Original Message-----
> From: Erik Rydgren
> Sent: den 15 september 2003 10:13
> To: [EMAIL PROTECTED]
> Subject: DOM performance/coding issue
>
> As previously stated it is the getElementsByTagNameNS that is the bad
> boy in your code. What the previous writers didn't explain was why it
is
> so.
>
> The getElementsByTagNameNS operate on ALL nodes in a subtree. It
> therefore has to traverse the whole tree and compare tagnames of ALL
> elements against your string. If your document is large then you'll
get
> the picture. It is as inefficient as doing a tablescan for each
database
> lookup. Of course if you can't do any assumptions how your
datastructure
> looks like, then the getElementsByTagNameNS method is very powerful.
But
> in your case it sounds like you already know how your datastructure
look
> like and therefore you can write more efficient code by doing the
> iteration and comparison yourself.
>
> Something like this (I have used a pseudo function equal to clarify
the
> code):
>
> DOMNode* pNode = m_pDocument->getDocumentElement()->getFirstChild();
> while (pNode) {
> if (pNode->getNodeType() == DOM_NODE && equal(pNode->getNodeName(),
> "PatchData")) {
> DOMNode* pInnerNode = pNode->getFirstChild();
> while (pInnerNode) {
> if (pInnerNode->getNodeType() == DOM_NODE &&
> equal(pInnerNode->getNodeName(), "CbName")) {
> if (equal(pInnerNode->getNodeValue(), "your searchstring "))
> // Bingo!!! We found it, process node
> break; // No need to search for more inner nodes
> }
> }
> }
> }
> pNode = pNode->getNextSibling();
> }
>
> But if you know that you'll never will see other nodes than PatchData
> nodes under the rootnode you don't have to compare tagname for those
> either.
>
> Regards
> Erik Rydgren
> Mandarin FS
> Sweden
>
> > -----Original Message-----
> > From: David Hoffer [mailto:[EMAIL PROTECTED]
> > Sent: den 15 september 2003 00:06
> > To: [EMAIL PROTECTED]
> > Subject: DOM performance/coding issue
> >
> > I have a question about how to effectively parser a large DOM
> document.
> > For
> > example, I have a lot of 'PatchData' elements. I am looking for the
> set
> > of
> > these where the child element 'CbName' matches a certain string.
The
> > following code takes 30 seconds just to loop through the DOMNodeList
> > before
> > it finds the first matching child. How can I make this faster?
> >
> > DOMNodeList* pDOMNodeList =
> > m_pDocument->getDocumentElement()->getElementsByTagNameNS(NULL,
> > L"PatchData");
> >
> > for (int i=0; i<pDOMNodeList->getLength(); i++)
> > {
> > DOMNode* pDOMNode = pDOMNodeList->item(i);
> > DOMNodeList* pDOMNodeList = ((const
> > DOMElement*)pDOMNode)->getElementsByTagNameNS(NULL, L"CbName");
> > pDOMNode = pDOMNodeList->item(0);
> > DOMNode* pChildNode = pDOMNode->getFirstChild();
> > std::wstring wstrTagValue = pChildNode->getNodeValue();
> >
> > if (wcscmp(wstrTagValue.c_str(), m_wstrColorbarName.c_str()) ==
> 0)
> > {
> > // This is one of the ones I want...I spend very little
> time
> > here.
> > }
> >
> > // I spend 30 seconds here, in a loop...
> > }
> >
> > My XML structure is like...
> > <PatchData>
> > <CbName>abc</CbName>
> > <Location>0</Location>
> > <Type>0</Type>
> > <Width>5.15</Width>
> > <Enabled>true</Enabled>
> > </PatchData>
> > <PatchData>
> > <CbName>abc</CbName>
> > <Location>1</Location>
> > <Type>1</Type>
> > <Width>5.25</Width>
> > <Enabled>false</Enabled>
> > </PatchData>
> >
> > -dh
>
>
>
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