Jan Hartmann wrote: > On 16-1-2010 16:03, Mateusz Loskot wrote: >> Jan Hartmann wrote: >> >>> Yes, that is clear, thanks. I see that at the moment only raster files >>> are supported. >>> Would it make sense to do this for vector formats too? >>> >> The VSI layer is available to all parts of GDAL and OGR. >> If you scan source code of OGR drivers, you'll find that this feature >> is already used by, for example, GTM driver: >> >> http://trac.osgeo.org/gdal/browser/trunk/gdal/ogr/ogrsf_frmts/gtm/gtm.cpp?rev=17612#L339 >> >> >> IOW, VSI layer is available and not dependant on GDAL or OGR format, >> it's a separate library of common functions. >> >> Best regards, >> > > Does that mean that I can use ogrinfo on a gzipped archive, like > gdalinfo (http://trac.osgeo.org/gdal/wiki/UserDocs/ReadInZip)?
Yes, it does but...as long as OGR driver performs filesystem operations using VSI*L API. The problem is that only few of them use VSI*L. As an example, I just updated OGR GeoJSON driver to use VSI*L API: http://trac.osgeo.org/gdal/changeset/18573 As you can see, it is not a complex task, but may be time consuming and tedious, and requires quite a lot of testing. After these changes are applied, it is possible to (un)gzip GeoJSON datasets: 1) Translate Shapefile to GeoJSON file compressed using GZip: $ ogr2ogr -f GeoJSON /vsigzip/./points.geojson.gz points.shp 2) Read GZip compressed GeoJSON dataset: $ ogrinfo /vsigzip/./points.geojson.gz $ ogrinfo /vsigzip/./points.geojson.gz OGRGeoJSON > This page says: > > "The fact that this new capability is implemented as virtual file > systems imply that it will only work for GDAL drivers supporting the > "large file API"" Apparently, the Wiki needs to be updated. > It would be a nice archive functionality. Yes, indeed. The work requires to step in to each OGR driver directory, grep .cpp files for VSI verify what VSI API is used.driver: For example, OGR Shapefile driver would, in theory, need to get updated VSI calls in about 50 places: $ grep VSI *.cpp | wc -ls 47 I'm quite sure volunteers would be appreciated. Best regards, -- Mateusz Loskot, http://mateusz.loskot.net Charter Member of OSGeo, http://osgeo.org _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
