public override IGeometry Read(Stream stream)
{
// MySQL stores geometry values using the first 4 bytes to indicate the SRID
// followed by the WKB representation of the value; see:
// https://dev.mysql.com/doc/refman/5.7/en/gis-data-formats.html#gis-wkb-format
using (var reader1 = new BinaryReader(stream))
{
int srid = -1;
try
{
srid = reader1.ReadInt32();
}
catch
{
// Ignored
}
if (srid == 0)
{
srid = -1;
}
using (var reader2 = new BiEndianBinaryReader(stream))
{
var geometry = Read(reader2);
geometry.SRID = srid;
return(geometry);
}
}
}
private static TGeometry ConvertFromProviderCore(MySqlGeometry v)
{
using var memoryStream = new MemoryStream(v.Value);
// MySQL starts it's spatial data with a 4 byte SRID, that is unexpected by WKBReader.
var biEndianBinaryReader = new BiEndianBinaryReader(memoryStream);
var srid = biEndianBinaryReader.ReadUInt32();
var geometryServices = _geometryServiceses.GetOrAdd(
srid,
b => new NtsGeometryServices(
NtsGeometryServices.Instance.DefaultCoordinateSequenceFactory,
NtsGeometryServices.Instance.DefaultPrecisionModel,
(int)b));
var reader = new WKBReader(geometryServices);
var geometry = reader.Read(memoryStream);
return((TGeometry)geometry);
}
