WKBWriter does not match Spatialite's AsBinary()

[GoogleCodeExporter]

I think there's an error in WKBWriter.

WKBWriter writer = new WKBWriter(ByteOrder.LittleEndian, false, true, false);
IPoint pt = new Point(1, 1, 1);
byte[] wkb = writer.Write(pt); // It's a shame I have to do this.

byte[] b = db.Query("SELECT AsBinary(ST_GeomFromText('POINTZ(1 1 1)', 4326))");

bool equality = wkb.Equals(b);

equality is false.

wkb[4] is 128 while b[4] is 0

Original issue reported on code.google.com by kjeremy@gmail.com on 14 Dec 2012 at 12:37

[GoogleCodeExporter]

I'm thinking it's because of this segment:

            //Modify WKB Geometry type
            var intGeometryType = (uint)geometryType & 0xff;
            if ((HandleOrdinates & Ordinates.Z) == Ordinates.Z)
            {
                intGeometryType += 1000;
                intGeometryType |= 0x80000000;
            }

I haven't seen anything about the |= in any of my google searches on WKB.

Original comment by kjeremy@gmail.com on 14 Dec 2012 at 1:24

[GoogleCodeExporter]

You are aware that there are special SpatiaLite reader/writer classes?

The flag 0x80000000 is from the EWKB definition used within PostGIS.
Need to check.

Original comment by felix.ob...@netcologne.de on 14 Dec 2012 at 12:11

• Changed state: Started

[GoogleCodeExporter]

Addendum:
> WKBWriter writer = new WKBWriter(ByteOrder.LittleEndian, false, true, false);
> IPoint pt = new Point(1, 1, 1);
> byte[] wkb = writer.Write(pt); // It's a shame I have to do this.

Why not use
var wkb = new Point(1, 1, 1).AsBinary() /*.ToBinary()*/;

If that is not suitable, you can write yourself some extension method like
public static byte[] AsBinary(this IGeometry self, IBinaryWriter<?> writer)
{
    return writer.Write(self);
}

One more question:
Have you tried SpatiaLite's wkb parsing functions? Do they fail?

Original comment by felix.ob...@netcologne.de on 14 Dec 2012 at 12:28

[GoogleCodeExporter]

Hi Felix,

In order for the WKB to capture the Z value I can't use AsBinary directly... I 
have to pass in true for emitZ to the WKBWriter.  Otherwise the geometry type 
is represented as 1 instead of 1001 in the WKB.

Spatialite fails to parse the output of that unless I zero out byte[4].  If I 
call AsBinary() and try to insert into the database it fails because my 
geometry needs to be XYZ in my database.  AsBinary() works fine for inserting 
XY points.  As soon as I need to deal with XYZ it fails.

There are special SpatiaLite readers/writers in NetTopologySuite?  If 
WKBWriter/Reader are for EWKB why are they not EWKBWriter/Reader?

Original comment by kjeremy@gmail.com on 14 Dec 2012 at 2:45

[GoogleCodeExporter]

The Writer doesn't appear to be in the 1.12.1 tarball.

Original comment by kjeremy@gmail.com on 14 Dec 2012 at 2:54

[GoogleCodeExporter]

Ok I see the issue with not being able to find the writer.  It's not in 
NetTopologySuite.Net.VS2010.sln but appears to be in 
NetTopologySuite.VS2010.sln which was not what I had built because I lack 
Silverlight etc.  Can I just copy those projects into the other solution and 
build?

Original comment by kjeremy@gmail.com on 14 Dec 2012 at 3:05

[GoogleCodeExporter]

Their only (non-Framework) reference is to GeoAPI (iirc), so you should be able 
to do that.

Original comment by felix.ob...@netcologne.de on 14 Dec 2012 at 3:09

[GoogleCodeExporter]

Thank you! I added the project to the MonoDroid solution and it worked so I'll 
close the issue out.  I do think the WKB classes should be renamed to EWKB 
though.

Original comment by kjeremy@gmail.com on 14 Dec 2012 at 7:12

[GoogleCodeExporter]

@kjeremy:
Could you please test if fixing WKBWriter with attached patchfile solves the 
issue.
Thanks

Original comment by felix.ob...@netcologne.de on 19 Dec 2012 at 11:24

Attachments:

• strict.patch

[GoogleCodeExporter]

Patch applied some time ago, no more complaints, seems to work

Original comment by felix.ob...@netcologne.de on 24 Jun 2013 at 11:51

• Changed state: Fixed