[gdal-dev] [OGR] Questions about the MIF/MID format implementation

[Even Rouault]

Le lundi 19 mai 2014 16:27:33, Pierre Mauduit a écrit :
> Hi list,
> 
> We are currently using GDAL/OGR bindings for Java, and we stumbled upon a
> bug using MIF/MID (where the same code achieves generating TAB with no
> problem at all). While debugging, we reached the following (GeoTools)
> code[1]:
> 
>  if (!driverName.equalsIgnoreCase("georss") &&
>                 !driverName.equalsIgnoreCase("gpx") &&
>                 !driverName.equalsIgnoreCase("sosi") &&
>                 !ogr.LayerCanCreateField(layer)) {
>                 throw new DataSourceException(
>                         "OGR reports it's not possible to create fields on
> this layer");
>             }
> 
> By digging into the MIF/MID and tab code "OGR-side", I discovered that the
> TestCapability method between the two formats is not returning exactly the
> same capabilities. I thought both were very close to each other, so is the
> CreateField capability not supported at MIF/MID side, or is it just a
> missing test ?

Yes looks like the TestCapability() method on the MIF side should also report 
OLCCreateField. CreateField() is necessary implemented since you can create 
MIF/MID files with attributes.

> 
> I tried to recompile a own version of GDAL/OGR returning true for
> CreateField TestCapability in the MIF/MID code, and I was able to correctly
> generate the expected mif file from my application, but I might be wrong in
> the approach, being pretty new to gdal codebase and not a C++ guru.
> 
> Secondly, by reading the code, I found out a weird test[2]: is line #2258
> ever triggered ?

Yep, I guess the second one should read OLCRandomWrite, if we compare with the 
TAB side. Anyway in practice this should be OK since the default value is 
FALSE...

> 
> Thanks in advance for the answers and regards,
> 
> [1]
> https://github.com/geotools/geotools/blob/master/modules/plugin/ogr/ogr-cor
> e/src/main/java/org/geotools/data/ogr/OGRDataStore.java#L194-L198
> 
> [2]
> https://github.com/OSGeo/gdal/blob/trunk/gdal/ogr/ogrsf_frmts/mitab/mitab_m
> iffile.cpp#L2255-L2259
> 
> 
> <https://github.com/geotools/geotools/blob/master/modules/plugin/ogr/ogr-co
> re/src/main/java/org/geotools/data/ogr/OGRDataStore.java#L194-L198>

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