[gdal-dev] replacing a dataset in C++

[Michael Sumner]

Hello, I have a question about safely re-casting a dataset to another, I
want to use Multidim to re-orient an MDArray as a classic 2D raster. I was
a bit surprised that this works (I just overwrite poSrcDS with the
classic form):

I'm passing in 'osFilename', 'osArrayName' and two dimension indexes
'index_x' and 'index_y', the first "Open()" line is a literal copy from
vrtdataset.cpp:


//  I've removed all the nullptr checks from this code
auto poSrcDS = std::unique_ptr<GDALDataset, GDALDatasetUniquePtrReleaser>(
         GDALDataset::Open(osFilename, GDAL_OF_RASTER |
GDAL_OF_VERBOSE_ERROR,
                          aosAllowedDrivers.List(), aosOpenOptions.List(),
                          nullptr));
// now open in mdim mode, and get the specified MDArray in Classic form
with index_x,index_y
auto poMDimDS = std::unique_ptr<GDALDataset>(GDALDataset::Open(osFilename,
GDAL_OF_MULTIDIM_RASTER));
auto poMdimGroup = poMDimDS->GetRootGroup();
auto poArrayDS = poMdimGroup->OpenMDArrayFromFullname(osFilename);
auto poClassicDS = poArrayDS->AsClassicDataset(index_x, index_y);

// FIXME how to safely swap poSrcDS with poClassicDS
poSrcDS = std::unique_ptr<GDALDataset,
GDALDatasetUniquePtrReleaser>(poClassicDS);

My question is about the last line where poClassic "replaces" poSrcDS: what
am I responsible for to make that safe?

Thanks!


-- 
Michael Sumner
Research Software Engineer
Australian Antarctic Division
Hobart, Australia
e-mail: mdsumner at gmail.com
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