[Gdal-dev] Free OGRGeometry?

[Frank Warmerdam]

On 11/25/05, Craig Miller <craig.miller at spatialminds.com> wrote:
> I'm trying to set a spatial filter, but am having difficulty determining how
> I am supposed to create and free OGRGeometry correctly.  In ogr2ogr the
> spatial filter doesn't appear to be freed.  In my code, this is causing a
> memory leak.  What is the best way to allocate/deallocate OGRGeometry?
>
> In ogr2ogr it done like this:
>
> // inside of main()
> // Declared
> OGRGeometry *poSpatialFilter = NULL;
>
> // Initialized
> OGRLinearRing  oRing;
>
> oRing.addPoint( atof(papszArgv[iArg+1]), atof(papszArgv[iArg+2]) );
> oRing.addPoint( atof(papszArgv[iArg+1]), atof(papszArgv[iArg+4]) );
> oRing.addPoint( atof(papszArgv[iArg+3]), atof(papszArgv[iArg+4]) );
> oRing.addPoint( atof(papszArgv[iArg+3]), atof(papszArgv[iArg+2]) );
> oRing.addPoint( atof(papszArgv[iArg+1]), atof(papszArgv[iArg+2]) );
>
> poSpatialFilter = new OGRPolygon();
> ((OGRPolygon *) poSpatialFilter)->addRing( &oRing );
>
> // Used
> if( poSpatialFilter != NULL )
>         poLayer->SetSpatialFilter( poSpatialFilter );
>
> // Freed?

Craig,

The most direct way is "delete poSpatialFilter;" after
the SetSpatialFilter() call.  The SetSpatialFilter() method
will copy the geometry it is passed.  You could also just
put the OGRPolygon on the stack.

Finally, there is now a SetSpatialFilterRect() method on the
OGRLayer that looks like:

    virtual void        SetSpatialFilterRect( double dfMinX, double dfMinY,
                                              double dfMaxX, double dfMaxY );

Along with simplicity, the other advantage of calling this method is
that it will be certain to recognise the special case for a bounding
rectangle query (as opposed to a more complex polygon intersection).

Best regards,
--
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent