[geos-devel] C-API extension

[Jürgen E. Fischer]

Hi there,

while porting Quantum GIS from the C++ API to the C API I found that
there currently seems to be no way to get the cut edges from
the Polygonizer.

Please consider the attached patch, which adds that.

tia
Jürgen

-- 
Jürgen E. Fischer         norBIT GmbH               Tel. +49-4931-918175-0
Dipl.-Inf. (FH)           Rheinstraße 13            Fax. +49-4931-918175-50
Software Engineer         D-26506 Norden               http://www.norbit.de

-- 
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Rheinstrasse 13, 26506 Norden
GF: Jelto Buurman, HR: Amtsgericht Emden, HRB 5502

-------------- next part --------------
Index: capi/geos_c.cpp
===================================================================
--- capi/geos_c.cpp	(revision 2135)
+++ capi/geos_c.cpp	(working copy)
@@ -1349,6 +1349,54 @@
 }
 
 Geometry *
+GEOSPolygonizeGetCutEdges(const Geometry * const * g, unsigned int ngeoms)
+{
+	using geos::operation::polygonize::Polygonizer;
+	unsigned int i;
+	Geometry *out = NULL;
+
+	try{
+		// Polygonize
+		Polygonizer plgnzr;
+		for (i=0; i<ngeoms; i++) plgnzr.add(g[i]);
+#if GEOS_DEBUG
+	NOTICE_MESSAGE("geometry vector added to polygonizer");
+#endif
+
+		std::vector<const LineString *>*lines = plgnzr.getCutEdges();
+
+#if GEOS_DEBUG
+	NOTICE_MESSAGE("output polygons got");
+#endif
+
+		// We need a vector of Geometry pointers, not
+		// Polygon pointers.
+		// STL vector doesn't allow transparent upcast of this
+		// nature, so we explicitly convert.
+		// (it's just a waste of processor and memory, btw)
+    std::vector<Geometry*> *linevec =
+				new std::vector<Geometry *>(lines->size());
+		for (i=0; i<lines->size(); i++) (*linevec)[i] = (*lines)[i]->clone();
+
+		out = geomFactory->createGeometryCollection(linevec);
+		// the above method takes ownership of the passed
+		// vector, so we must *not* delete it
+	}
+	catch (const std::exception &e)
+	{
+		ERROR_MESSAGE("%s", e.what());
+		return NULL;
+	}
+	catch (...)
+	{
+		ERROR_MESSAGE("Unknown exception thrown");
+		return NULL;
+	}
+
+	return out;
+}
+
+Geometry *
 GEOSLineMerge(const Geometry *g)
 {
 		using geos::operation::linemerge::LineMerger;
Index: capi/geos_c.h.in
===================================================================
--- capi/geos_c.h.in	(revision 2135)
+++ capi/geos_c.h.in	(working copy)
@@ -283,8 +283,8 @@
  * all arguments remain ownership of the caller
  * (both Geometries and pointers)
  */
-extern GEOSGeometry GEOS_DLL *GEOSPolygonize(const GEOSGeometry * const geoms[],
-	unsigned int ngeoms);
+extern GEOSGeometry GEOS_DLL *GEOSPolygonize(const GEOSGeometry * const geoms[], unsigned int ngeoms);
+extern GEOSGeometry GEOS_DLL *GEOSPolygonizeGetCutEdges(const GEOSGeometry * const geoms[], unsigned int ngeoms);
 
 extern GEOSGeometry GEOS_DLL *GEOSLineMerge(const GEOSGeometry* g);
 extern GEOSGeometry GEOS_DLL *GEOSSimplify(const GEOSGeometry* g1, double tolerance);