AVC_e00 driver failing to read correctly

[anguscarr]

I have an issue with reading e00 files correctly using ogr.

I am using polygon coverages parsed into e00 files by ESRI tools. I assume the e00 files are correctly formatted.

For example, I can import data using the ESRI stack of tools, or with avcimport, and get the correct topology in the resultant coverage, as viewed in QGIS.

When I use ogr2ogr or QGIS to read from the e00 file directly, it fails, producing incorrect data, but no error message.

Later in QGIS, it is failing to view the table. My imagination suggests that's probably a follow-on from ogr closing the file or something like that.

I will try to generate the smallest possible test case to generate the error. One polygon, exported to e00.

avcimport worked fine on the e00 to produce the correct output.

The polygons have arcs with negative index numbers, which (according to the docs on  http://avce00.maptools.org/docs/v7_e00_cover.html#PAL means they are to be reversed as they are added to the polygon. I see no evidence that this takes place when I browse through http://trac.osgeo.org/gdal/browser/trunk/gdal/ogr/ogrsf_frmts/avc

and look for issues in the e00 files.

The ogr code suggests that it is looking for the arcs in a list, but it doesn't explicitly check for "negativeness".

The test case for autotesting the e00 code does not test reading PAL, as the e00 file was not built for polygon topology, as far as I can tell.

I will investigate further, and try to provide a test case.