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Improve WKBWriter to write empty polygons with zero rings #623

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merged 1 commit into from
Oct 27, 2020
Merged

Improve WKBWriter to write empty polygons with zero rings #623

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9 changes: 6 additions & 3 deletions modules/core/src/main/java/org/locationtech/jts/io/WKBWriter.java
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Original file line number Diff line number Diff line change
Expand Up @@ -45,9 +45,7 @@
* <ul>
* <li><b>Point</b>: a <code>WKBPoint</code> with <code>NaN</code> ordinate values</li>
* <li><b>LineString</b>: a <code>WKBLineString</code> with zero points</li>
* <li><b>Polygon</b>: currently output as a <code>WKBPolygon</code> with one <code>LinearRing</code> with zero points.
* <i>Note: This is different to other systems. It will change to a <code>WKBPolygon</code> with zero <code>LinearRing</code>s.</i>
* </li>
* <li><b>Polygon</b>: a <code>WKBPolygon</code> with zero rings</li>
* <li><b>Multi geometries</b>: a <code>WKBMulti</code> geometry of appropriate type with zero elements</li>
* <li><b>GeometryCollections</b>: a <code>WKBGeometryCollection</code> with zero elements</li>
* </ul></li>
Expand Down Expand Up @@ -363,6 +361,11 @@ private void writePolygon(Polygon poly, OutStream os) throws IOException
{
writeByteOrder(os);
writeGeometryType(WKBConstants.wkbPolygon, poly, os);
//--- write empty polygons with no rings (OCG extension)
if (poly.isEmpty()) {
writeInt(0, os);
return;
}
writeInt(poly.getNumInteriorRing() + 1, os);
writeCoordinateSequence(poly.getExteriorRing().getCoordinateSequence(), true, os);
for (int i = 0; i < poly.getNumInteriorRing(); i++) {
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32 changes: 28 additions & 4 deletions modules/core/src/test/java/org/locationtech/jts/io/WKBWriterTest.java
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Expand Up @@ -77,16 +77,40 @@ public void testSRID() throws Exception {
}

public void testPointEmpty2D() {
checkWKB("POINT EMPTY", 2, ByteOrderValues.LITTLE_ENDIAN, "0101000000000000000000F87F000000000000F87F" );
checkWKB("POINT EMPTY", 2, "0101000000000000000000F87F000000000000F87F" );
}

public void testPointEmpty3D() {
checkWKB("POINT EMPTY", 3, ByteOrderValues.LITTLE_ENDIAN, "0101000080000000000000F87F000000000000F87F000000000000F87F" );
checkWKB("POINT EMPTY", 3, "0101000080000000000000F87F000000000000F87F000000000000F87F" );
}

void checkWKB(String wkt, int dimension, int byteOrder, String expectedWKBHex) {
public void testPolygonEmpty2DSRID() {
checkWKB("POLYGON EMPTY", 2, ByteOrderValues.LITTLE_ENDIAN, 4326, "0103000020E610000000000000" );
}

public void testPolygonEmpty2D() {
checkWKB("POLYGON EMPTY", 2, "010300000000000000" );
}

public void testPolygonEmpty3D() {
checkWKB("POLYGON EMPTY", 3, "010300008000000000" );
}

void checkWKB(String wkt, int dimension, String expectedWKBHex) {
checkWKB(wkt, dimension, ByteOrderValues.LITTLE_ENDIAN, -1, expectedWKBHex);
}

void checkWKB(String wkt, int dimension, int byteOrder, int srid, String expectedWKBHex) {
Geometry geom = read(wkt);
WKBWriter wkbWriter = new WKBWriter(dimension, byteOrder);

// set SRID if not -1
boolean includeSRID = false;
if (srid >= 0) {
includeSRID = true;
geom.setSRID(srid);
}

WKBWriter wkbWriter = new WKBWriter(dimension, byteOrder, includeSRID);
byte[] wkb = wkbWriter.write(geom);
String wkbHex = WKBWriter.toHex(wkb);

Expand Down