[vtkusers] VTK XML File Format, Only read Header

[Henry Lehmann]

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Hello,

i try to only read which point/cell arrays are available in, for
example, an .vti file. I dont want to read the entire file.
I use the following code:

vtkNew<vtkXMLImageDataReader> reader;
reader->SetFileName("abc.vti");
vtkDataArraySelection* point_sel = reader->GetPointDataArraySelection();
//reader->Update();
int n0 = point_sel->GetNumberOfArrays();
int n1 = reader->GetNumberOfPointArrays();
int n2 = reader->GetNumberOfCellArrays();
cout << n0 << endl;
cout << n1 << endl;
cout << n2 << endl;

The output is

0
0
0

but there are 2 point arrays in the file. When removing the comment
and invoking Update() the arrays are shown.

How can i get information of the arrays without reading the whole
file, like Update() does?

Best regards,
Henry

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