Fix for issue #151

If an arc segment is colinear, then the positions are already linear. No need to throw an exception during linearization.

geom/src/main/java/org/geolatte/geom/cga/CircularArcLinearizer.java

@@ -23,7 +23,7 @@ public class CircularArcLinearizer<P extends Position> {
     final private P p1;
     final private P p2;
     final private Circle c;
-    final private boolean isCounterClockwise;
+    final private NumericalMethods.Orientation orientation;
     final private PositionSequenceBuilder<P> builder;
 
     //TODO threshold must become parameter of linearize/linearizeCircle!!
@@ -37,7 +37,7 @@ public CircularArcLinearizer(P p0, P p1, P p2, double threshold) {
         this.p1 = p1;
         this.p2 = p2;
         this.c = new Circle(p0, p1, p2, false);
-        this.isCounterClockwise = NumericalMethods.isCounterClockwise(p0, p1, p2);
+        this.orientation = NumericalMethods.orientation(p0, p1, p2);
         this.builder = variableSized((Class<P>) p0.getClass());
     }
 
@@ -89,23 +89,28 @@ public PositionSequence<P> linearize() {
 
         //now we "walk" from theta, over theta1 to theta2 (or inversely)
         PositionSequenceBuilder<P> builder = variableSized((Class<P>) p0.getClass());
-        if (isCounterClockwise) {
-	        builder.add(p0);
-	        AddPointsBetweenPolarCoordinates(theta0, theta1, p0, p1, angleIncr, builder);
-	        builder.add(p1);
-	        AddPointsBetweenPolarCoordinates(theta1, theta2, p1, p2, angleIncr, builder);
-	        builder.add(p2);
-	        return builder.toPositionSequence();
-        } else {
-        	// If clockwise, we have to do it reverse
-        	builder.add(p2);
-        	AddPointsBetweenPolarCoordinates(theta2, theta1, p2, p1, angleIncr, builder);
-        	builder.add(p1);
-        	AddPointsBetweenPolarCoordinates(theta1, theta0, p1, p0, angleIncr, builder);
-        	builder.add(p0);
-        	return builder.toPositionSequence().reverse();
+        switch (orientation) {
+            case Counterclockwise:
+                builder.add(p0);
+                AddPointsBetweenPolarCoordinates(theta0, theta1, p0, p1, angleIncr, builder);
+                builder.add(p1);
+                AddPointsBetweenPolarCoordinates(theta1, theta2, p1, p2, angleIncr, builder);
+                builder.add(p2);
+                return builder.toPositionSequence();
+            case Clockwise:
+                // If clockwise, we have to do it reverse
+                builder.add(p2);
+                AddPointsBetweenPolarCoordinates(theta2, theta1, p2, p1, angleIncr, builder);
+                builder.add(p1);
+                AddPointsBetweenPolarCoordinates(theta1, theta0, p1, p0, angleIncr, builder);
+                builder.add(p0);
+                return builder.toPositionSequence().reverse();
+            default:
+                builder.add(p0);
+                builder.add(p1);
+                builder.add(p2);
+                return builder.toPositionSequence();
         }
-
     }
 
     // Adds points strictly between theta and theta1, using the specified angle-increment

geom/src/main/java/org/geolatte/geom/cga/NumericalMethods.java

@@ -11,6 +11,14 @@
  */
 public class NumericalMethods {
 
+    public static enum Orientation {
+        Clockwise, Counterclockwise, Colinear
+    }
+
+    public final static int ClockWise = 1;
+    public final static int CounterClockWise = 2;
+
+
     /**
      * Calculates the determinant of a 2x2 matrix
      *
@@ -69,12 +77,12 @@ public static double determinant(double a11, double a12, double a13, double a21,
      * @param p2
      * @return true if counterclockwise
      */
-    public static boolean isCounterClockwise(Position p0, Position p1, Position p2) {
+    public static Orientation orientation(Position p0, Position p1, Position p2) {
         double det = deltaDeterminant(p0, p1, p2);
         if (det == 0) {
-            throw new IllegalArgumentException("Positions are collinear in 2D");
+            return Orientation.Colinear;
         }
-        return det > 0;
+        return det > 0? Orientation.Counterclockwise : Orientation.Clockwise;
     }
 
     /**

geom/src/test/java/org/geolatte/geom/cga/CircularArcLinearizerTest.java

@@ -4,6 +4,8 @@
 import static java.lang.Math.sin;
 import static junit.framework.Assert.assertFalse;
 import static junit.framework.Assert.assertTrue;
+import static org.geolatte.geom.cga.NumericalMethods.Orientation.Clockwise;
+import static org.geolatte.geom.cga.NumericalMethods.Orientation.Counterclockwise;
 import static org.junit.Assert.assertEquals;
 
 import org.geolatte.geom.C2D;
@@ -281,8 +283,8 @@ public ThreePointSample sample() {
         }
 
         // verify that we actually do return as expected.
-        assert ((isCCW && NumericalMethods.isCounterClockwise(positions[0], positions[1], positions[2])) ||
-                (!isCCW && !NumericalMethods.isCounterClockwise(positions[0], positions[1], positions[2])) );
+        assert ((isCCW && Counterclockwise ==NumericalMethods.orientation(positions[0], positions[1], positions[2])) ||
+                (!isCCW && Clockwise == NumericalMethods.orientation(positions[0], positions[1], positions[2])) );
 
         return new ThreePointSample(isCCW, theta, positions);
 

geom/src/test/java/org/geolatte/geom/codec/db/oracle/SmallArcBugTest.java

@@ -0,0 +1,22 @@
+package org.geolatte.geom.codec.db.oracle;
+
+import org.geolatte.geom.Geometry;
+import org.junit.Test;
+
+import static org.junit.Assert.assertNotNull;
+
+// for testing issue #151
+public class SmallArcBugTest {
+
+    @Test
+    public void testCase1(){
+        int[] elems =  {1,1005,3,1,2,1,15,2,2,19,2,1};
+        Double[] coords = {209499.475,578259.358,209503.708,578359.503,209505.325,578409.615,209505.144,578416.324,209504.933,578419.552,209505.118,578420.213,209505.693,578421.019,209500.401,578421.362,209500.401,578421.361,209500.402,578421.361,209500.832,578421.033,209501.057,578420.591,209501.063,578420.225,209499.607,578371.806,209497.623,578305.131,209495.574,578238.184,209495.409,578222.433,209495.062,578211.578,209498.02,578211.469,209499.475,578259.358};
+        SDOGeometry sdo = SDOGeometryHelper.sdoGeometry(
+                2003, 28992, null, elems, coords
+        );
+        Geometry<?> geom = Decoders.decode(sdo);
+        assertNotNull(geom); //check that this doesn't throw an exception
+    }
+
+}