NoData support in GIO

[Andrew.Loughhead at f...]

hi, 

GDAL, or more precisely GDALRasterBand::GetNoDataValue, does not 
currently get the NoData value associated with ESRI grids using 
the GIO / avgridio.dll driver. I'm hoping for a pointer towards 
what needs to be implemented where in order for a NoData value 
to be returned. 

An associated issue is that GDAL seems to disregard the type of 
ESRI grid that is being opened. So the GDALRasterBand member 
eDataType is always set to GDT_Float32. That is appropriate for 
ESRI floating point grids, but not really for integer grids. 

I am struggling to see where to modify GDAL to address these issues 
so would appreciate pointers. I am fairly familiar with the 
avgridio library. 

Thanks
Andrew.