[gdal-dev] Casting poDS, in IReadBlock and similar places

[Andrew C Aitchison]

I see that in http://www.gdal.org/gdal_drivertut.html the function
JDEMRasterBand::IReadBlock has
      JDEMDataset *poGDS = static_cast<JDEMDataset *>(poDS);
(this is a change from gdal-2.1.3 and earlier where
frmts/jdem/jdemdataset.cpp has
             JDEMDataset *poGDS = (JDEMDataset *) poDS;
).

However, I see that amongst other 2.2.0 drivers, reinterpret_cast
is more common than static_cast and the dods driver has dynamic_cast:

egrep -l "_cast<" ~/gdal2.2.0/gdal-2.2.0/frmts/*/*cpp |\
  xargs grep -A10 ::IReadBlock | egrep "_cast<.*Dataset \*>.*poDS *\);" |\
  sed -e 's=/home/werdna/gdal2.2.0/gdal-2.2.0/frmts/==' | sort -t= -k2

dods/dodsdataset2.cpp-    DODSDataset *poDODS = dynamic_cast<DODSDataset *>(poDS);

blx/blxdataset.cpp-    BLXDataset *poGDS = reinterpret_cast<BLXDataset *>(poDS);
raw/cpgdataset.cpp-    CPGDataset *poGDS = reinterpret_cast<CPGDataset *>( poDS );
raw/cpgdataset.cpp-    CPGDataset *poGDS = reinterpret_cast<CPGDataset *>( poDS );
raw/genbindataset.cpp-    GenBinDataset *poGDS = reinterpret_cast<GenBinDataset *>( poDS );
gsg/gsbgdataset.cpp-    GSBGDataset *poGDS = reinterpret_cast<GSBGDataset *>(poDS);
hdf4/hdf4imagedataset.cpp-    HDF4ImageDataset *poGDS = reinterpret_cast<HDF4ImageDataset *>( poDS );
jp2lura/jp2lurarasterband.cpp-    JP2LuraDataset *poGDS = reinterpret_cast<JP2LuraDataset *>(poDS);
raw/landataset.cpp-    LANDataset *poLAN_DS = reinterpret_cast<LANDataset *>( poDS );
leveller/levellerdataset.cpp-    LevellerDataset *poGDS = reinterpret_cast<LevellerDataset *>( poDS );
ngsgeoid/ngsgeoiddataset.cpp-    NGSGEOIDDataset *poGDS = reinterpret_cast<NGSGEOIDDataset *>( poDS );
nitf/nitfrasterband.cpp-    NITFDataset *poGDS = reinterpret_cast<NITFDataset *>( poDS );
northwood/grcdataset.cpp-    NWT_GRCDataset *poGDS = reinterpret_cast<NWT_GRCDataset *>( poDS );
northwood/grddataset.cpp-    NWT_GRDDataset *poGDS = reinterpret_cast<NWT_GRDDataset *>(poDS);
ozi/ozidataset.cpp-    OZIDataset *poGDS = reinterpret_cast<OZIDataset *>( poDS );
plmosaic/plmosaicdataset.cpp-    PLMosaicDataset* poMOSDS = reinterpret_cast<PLMosaicDataset *>( poDS );
png/pngdataset.cpp-    PNGDataset *poGDS = reinterpret_cast<PNGDataset *>( poDS );
rasterlite/rasterlitedataset.cpp-    RasterliteDataset* poGDS = reinterpret_cast<RasterliteDataset *>( poDS );
rik/rikdataset.cpp-    RIKDataset *poRDS = reinterpret_cast<RIKDataset *>( poDS );
rmf/rmfdataset.cpp-    RMFDataset  *poGDS = reinterpret_cast<RMFDataset *>( poDS );
sgi/sgidataset.cpp-    SGIDataset* poGDS = reinterpret_cast<SGIDataset *>( poDS );
srtmhgt/srtmhgtdataset.cpp-  SRTMHGTDataset* poGDS = reinterpret_cast<SRTMHGTDataset *>( poDS );
terragen/terragendataset.cpp-    TerragenDataset& ds = *reinterpret_cast<TerragenDataset *>( poDS );
usgsdem/usgsdemdataset.cpp-    USGSDEMDataset *poGDS = reinterpret_cast<USGSDEMDataset *>( poDS );
vrt/vrtwarped.cpp-    VRTWarpedDataset *poWDS = reinterpret_cast<VRTWarpedDataset *>( poDS );
webp/webpdataset.cpp-    WEBPDataset* poGDS = reinterpret_cast<WEBPDataset *>( poDS );
xyz/xyzdataset.cpp-    XYZDataset *poGDS = reinterpret_cast<XYZDataset *>( poDS );
zmap/zmapdataset.cpp-    ZMapDataset *poGDS = reinterpret_cast<ZMapDataset *>( poDS );

aaigrid/aaigriddataset.cpp-    AAIGDataset *poODS = static_cast<AAIGDataset *>(poDS);
hdf5/hdf5imagedataset.cpp-    HDF5ImageDataset *poGDS = static_cast<HDF5ImageDataset *>(poDS);
iris/irisdataset.cpp-    IRISDataset *poGDS = static_cast<IRISDataset *>(poDS);
jdem/jdemdataset.cpp-    JDEMDataset *poGDS = static_cast<JDEMDataset *>(poDS);
jpeg/jpgdataset.cpp-    JPGDataset *poJDS = static_cast<JPGDataset *>(poDS);
saga/sagadataset.cpp-    SAGADataset *poGDS = static_cast<SAGADataset *>( poDS );

My C++ is 25 years old and self taught, so I am still learning when to
use static_cast, dynamic_cast and reinterpret_cast (and const_cast).

Can anyone more familiar with modern C++ guide me ?

Thanks,

Andrew C Aitchison