Fix element number estimation when parsing WKB of GEOMETRYCOLLECTION containing empty geometries

[Kontinuation]

WKBReader will raise ParseException when parsing WKB of GeometryCollection containing multiple empty geometries, such as GEOMETRYCOLLECTION(LINESTRING EMPTY, MULTIPOINT EMPTY). The following code reproduces this problem:

WKTReader wktReader = new WKTReader();
WKBWriter wkbWriter = new WKBWriter();
WKBReader wkbReader = new WKBReader();
Geometry geom = wktReader.read("GEOMETRYCOLLECTION(LINESTRING EMPTY, MULTIPOINT EMPTY)");
byte[] wkb = wkbWriter.write(geom);
wkbReader.read(wkb);

Which yields:

Exception in thread "main" org.locationtech.jts.io.ParseException: null value is too large
	at org.locationtech.jts.io.WKBReader.readNumField(WKBReader.java:198)
	at org.locationtech.jts.io.WKBReader.readGeometryCollection(WKBReader.java:385)
	at org.locationtech.jts.io.WKBReader.readGeometry(WKBReader.java:279)
	at org.locationtech.jts.io.WKBReader.read(WKBReader.java:191)
	at org.locationtech.jts.io.WKBReader.read(WKBReader.java:159)

This PR fixes this problem by estimating the number of geometries in GeometryCollection in a more conservative manner: the minimal length of a WKB geometry is 9 (1 byte order + 4 WKT type + 4 length), we estimate the number of geometries by dividing the length of WKB buffer by 8 instead of 16.

[dr-jts]

Thanks, good catch!

[nenadzdravkovic-tomtom]

Hi @dr-jts , if I may kindly ask - are there any plans to make a release with this fix in near future? I don't see any fixed date on https://github.com/locationtech/jts/milestones.
Thanks!

[dr-jts]

Hi @dr-jts , if I may kindly ask - are there any plans to make a release with this fix in near future?

No firm release date, but will try and get one out over the summer.