netcdf driver cannot read netcdf-4 files with UBYTE data

[etourigny]

Files that are of unsigned byte data type in the NC4 (netcdf-4) format are incorrectly read. To reproduce do the following

$ gdal_translate -of netcdf -co FORMAT=NC4 byte.tif byte.nc
$ gdalinfo -checksum byte.nc
[...]
ERROR 1: netCDF scanline fetch failed: #-60 (NetCDF: Numeric conversion not representable)
ERROR 1: byte.nc, band 1: IReadBlock failed at X offset 0, Y offset 0
ERROR 1: GetBlockRef failed at X block offset 0, Y block offset 0
ERROR 3: Checksum value couldn't be computed due to I/O read error.

  Checksum=0

The problem does not appear when files are saved in netcdf-4 classic format, because it uses NC_BYTE and not NC_UBYTE.

Also, metadata (such as missval) is not supported if a variable is not stored in NC_UBYTE type.

GDAL_netCDF: NCDFGetAttr unsupported type 7 for attribute _FillValue

[etourigny]

patch for autotest

[etourigny]

patch that fixes 2 bugs

[etourigny]

Attached patches to test and fix the 2 bugs found - waiting to commit before 1.10-RC2 is voted.

[Even Rouault]

You can still commit that in trunk for now. And backport later if appropriate

[etourigny]

ok - I guess this will not impact 1.10 release, even if rc2 is not promoted to final? I will backport to 1.10 after that. thanks

[Even Rouault]

If another rc is needed, it will be based on 1.10 branch, not trunk, so commits in trunk are OK.

[etourigny]

committed to trunk in r25919 and r25920 . Will backport to 1.10 after release and then close this ticket

[etourigny]

backported to 1.10 (r25967 and r25968)