[geos-commits] r2327 - in trunk/source: geom headers/geos/geom

[svn_geos at osgeo.org]

Author: strk
Date: 2009-04-08 10:41:58 -0400 (Wed, 08 Apr 2009)
New Revision: 2327

Modified:
   trunk/source/geom/CoordinateSequence.cpp
   trunk/source/headers/geos/geom/CoordinateSequence.h
Log:
Add increasingDirection static method, from JTS's CoordinateArray (GEOS puts all of them in CoordinateSequence for historical reasons)


Modified: trunk/source/geom/CoordinateSequence.cpp
===================================================================
--- trunk/source/geom/CoordinateSequence.cpp	2009-04-08 13:16:37 UTC (rev 2326)
+++ trunk/source/geom/CoordinateSequence.cpp	2009-04-08 14:41:58 UTC (rev 2327)
@@ -141,6 +141,21 @@
 	cl->setPoints(v);
 }
 
+int
+CoordinateSequence::increasingDirection(const CoordinateSequence& pts)
+{
+	size_t ptsize = pts.size();
+	for (size_t i=0, n=ptsize/2; i<n; ++i)
+	{
+		size_t j = ptsize - 1 - i;
+		// skip equal points on both ends
+		int comp = pts[i].compareTo(pts[j]);
+		if (comp != 0) return comp;
+	}
+	// array must be a palindrome - defined to be in positive direction
+	return 1;
+}
+
 void
 CoordinateSequence::reverse(CoordinateSequence *cl)
 {

Modified: trunk/source/headers/geos/geom/CoordinateSequence.h
===================================================================
--- trunk/source/headers/geos/geom/CoordinateSequence.h	2009-04-08 13:16:37 UTC (rev 2326)
+++ trunk/source/headers/geos/geom/CoordinateSequence.h	2009-04-08 14:41:58 UTC (rev 2327)
@@ -265,6 +265,25 @@
 	/// Scroll given CoordinateSequence so to start with given Coordinate.
 	static void scroll(CoordinateSequence *cl, const Coordinate *firstCoordinate);
 
+	/** \brief
+	 * Determines which orientation of the {@link Coordinate} array
+	 * is (overall) increasing.
+	 *
+	 * In other words, determines which end of the array is "smaller"
+	 * (using the standard ordering on {@link Coordinate}).
+	 * Returns an integer indicating the increasing direction.
+	 * If the sequence is a palindrome, it is defined to be
+	 * oriented in a positive direction.
+	 *
+	 * @param pts the array of Coordinates to test
+	 * @return <code>1</code> if the array is smaller at the start
+	 * or is a palindrome,
+	 * <code>-1</code> if smaller at the end
+	 *
+	 * NOTE: this method is found in CoordinateArrays class for JTS
+	 */
+	static int increasingDirection(const CoordinateSequence& pts);
+
 	/// Reverse Coordinate order in given CoordinateSequence
 	static void reverse(CoordinateSequence *cl);