Is it possible to edit the existing XML file with TXMLEngine in ROOT?

[p73]

I know that reading and creating XML files is available in ROOT with TXMLEngine. But what if I want to edit the existing XML file? Particularly, I want to add a child to the existing node. How one could reach this?

I tried the following code:

    //some code above
    XMLNodePointer_t generalInfo = findChild( "GeneralInfo", mainNode, xml ); 

    XMLNodePointer_t info = xml->NewChild( generalInfo, 0, "Info" );
    xml->NewAttr( info, 0, "name", "TrainingSignalEvents");
    xml->NewIntAttr( info, "value", 1000 );

    xml->SaveDoc( xmldoc, fileName );

    xml->FreeDoc( xmldoc );
    delete xml; 

Where findChild is function that I wrote to simplify finding of child by name. It worked in this way:

    <Info name="TMVA Release" value="4.2.1 [262657]"/>
    <Info name="ROOT Release" value="6.08/02 [395266]"/>
    <Info name="Creator" value="wolfgang"/>
    <Info name="Date" value="Fri Nov 24 23:49:39 2017"/>
    <Info name="Host" value="Linux wolfgang-IdeaPad-Z585 4.4.0-81-generic #104~14.04.1-Ubuntu SMP Wed Jun 14 12:45:52 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux"/>
    <Info name="Dir" value="/home/wolfgang/BINP/Diploma/Analysis/omega_pi0/Algorithm"/>
    <Info name="Training events" value="28324"/>
    <Info name="TrainingTime" value="1.15905461e+01"/>
    <Info name="AnalysisType" value="Classification"/>
    <Info name="TrainingSignalEvents" value="1000"/>
  </GeneralInfo>

You see that new child Info has been added. But I have two questions here. Is it possible to specify where to place new child? And is it a proper way to add new child in the existing file? I mean just SaveDoc in the end?

UPDATE: One more question. Is it possible to remove single child from the node? If yes, how?

Thanks in advance.

[linev]

Hi,

I guess you asking possibility to modify existing XML file with TXMLEngine?

Yes, it is possible.
Look xmlnewfile.C and xmlreadfile.C macros in tutorials/xml/ directory.
After existing file parsed in xmlreadfile.C macro, you can insert/delete/modify any of it elements and store in new XML file.

Regards,
Sergey

[p73]

Thanks for your early reply. See edit, please.

[linev]

New child node always add to the end of children list.
There is possibility to move child node to the beginning of childs list with
TXMLEngine::AddChildFirst() function. You should do in your code:

XMLNodePointer_t generalInfo = findChild( "GeneralInfo", mainNode, xml ); 

XMLNodePointer_t info = xml->NewChild( generalInfo, 0, "Info" );
xml->NewAttr( info, 0, "name", "TrainingSignalEvents");
xml->NewIntAttr( info, "value", 1000 );

xml->UnlinkNode(info);
xml->AddChildFirst(generalInfo, info); 

xml->SaveDoc( xmldoc, fileName );

xml->FreeDoc( xmldoc );
delete xml; 

Unfortunately, there is no function to insert node somewhere in the middle of children list

[p73]

It is necessary to call UnlinkNode(info) before SaveDoc if I do not want to place new child to the beginning of the parent child list?

[linev]

UnlinkNode(info) required only if you want to move it to some other place.