C API cluster functions: Return ids instead of GEOSGeometry*

capi/geos_c.cpp

@@ -343,29 +343,34 @@ extern "C" {
         return GEOSNearestPoints_r(handle, g1, g2);
     }
 
-    GEOSGeometry*
-    GEOSClusterDBSCAN(Geometry* g, double eps, unsigned minPoints) {
-        return GEOSClusterDBSCAN_r(handle, g, eps, minPoints);
+    unsigned*
+    GEOSClusterDBSCAN(const GEOSGeometry* g, double eps, unsigned minPoints, unsigned* numClusters)
+    {
+        return GEOSClusterDBSCAN_r(handle, g, eps, minPoints, numClusters);
     }
 
-    GEOSGeometry*
-    GEOSClusterGeometryDistance(GEOSGeometry* g, double d) {
-        return GEOSClusterGeometryDistance_r(handle, g, d);
+    unsigned*
+    GEOSClusterGeometryDistance(const GEOSGeometry* g, double d, unsigned* numClusters)
+    {
+        return GEOSClusterGeometryDistance_r(handle, g, d, numClusters);
     }
 
-    GEOSGeometry*
-    GEOSClusterGeometryIntersects(GEOSGeometry* g) {
-        return GEOSClusterGeometryIntersects_r(handle, g);
+    unsigned*
+    GEOSClusterGeometryIntersects(const GEOSGeometry* g, unsigned* numClusters)
+    {
+        return GEOSClusterGeometryIntersects_r(handle, g, numClusters);
     }
 
-    GEOSGeometry*
-    GEOSClusterEnvelopeDistance(GEOSGeometry* g, double d) {
-        return GEOSClusterEnvelopeDistance_r(handle, g, d);
+    unsigned*
+    GEOSClusterEnvelopeDistance(const GEOSGeometry* g, double d, unsigned* numClusters)
+    {
+        return GEOSClusterEnvelopeDistance_r(handle, g, d, numClusters);
     }
 
-    GEOSGeometry*
-    GEOSClusterEnvelopeIntersects(GEOSGeometry* g) {
-        return GEOSClusterEnvelopeIntersects_r(handle, g);
+    unsigned*
+    GEOSClusterEnvelopeIntersects(const GEOSGeometry* g, unsigned* numClusters)
+    {
+        return GEOSClusterEnvelopeIntersects_r(handle, g, numClusters);
     }
 
     Geometry*

capi/geos_c.h.in

@@ -1849,34 +1849,38 @@ extern GEOSGeometry GEOS_DLL *GEOSGeom_transformXYZ_r(
     void* userdata);
 
 /** \see GEOSClusterDBSCAN */
-extern GEOSGeometry GEOS_DLL *GEOSClusterDBSCAN_r(
-        GEOSContextHandle_t handle,
-        GEOSGeometry* g,
-        double eps,
-        unsigned minPoints);
-
+extern unsigned GEOS_DLL* GEOSClusterDBSCAN_r(
+    GEOSContextHandle_t handle,
+    const GEOSGeometry* g,
+    double eps,
+    unsigned minPoints,
+    unsigned* numClusters);
 
 /** \see GEOSClusterGeometryDistance */
-extern GEOSGeometry GEOS_DLL *GEOSClusterGeometryDistance_r(
-        GEOSContextHandle_t handle,
-        GEOSGeometry* g,
-        double d);
+extern unsigned GEOS_DLL* GEOSClusterGeometryDistance_r(
+    GEOSContextHandle_t handle,
+    const GEOSGeometry* g,
+    double d,
+    unsigned* numClusters);
 
 /** \see GEOSClusterGeometryIntersects */
-extern GEOSGeometry GEOS_DLL *GEOSClusterGeometryIntersects_r(
-        GEOSContextHandle_t handle,
-        GEOSGeometry* g);
+extern unsigned GEOS_DLL* GEOSClusterGeometryIntersects_r(
+    GEOSContextHandle_t handle,
+    const GEOSGeometry* g,
+    unsigned* numClusters);
 
 /** \see GEOSClusterEnvelopeDistance */
-extern GEOSGeometry GEOS_DLL *GEOSClusterEnvelopeDistance_r(
-        GEOSContextHandle_t handle,
-        GEOSGeometry* g,
-        double d);
+extern unsigned GEOS_DLL* GEOSClusterEnvelopeDistance_r(
+    GEOSContextHandle_t handle,
+    const GEOSGeometry* g,
+    double d,
+    unsigned* numClusters);
 
 /** \see GEOSClusterEnvelopeIntersects */
-extern GEOSGeometry GEOS_DLL *GEOSClusterEnvelopeIntersects_r(
-        GEOSContextHandle_t handle,
-        GEOSGeometry* g);
+extern unsigned GEOS_DLL* GEOSClusterEnvelopeIntersects_r(
+    GEOSContextHandle_t handle,
+    const GEOSGeometry* g,
+    unsigned* numClusters);
 
 /* ========= Algorithms ========= */
 
@@ -3791,10 +3795,13 @@ extern GEOSGeometry GEOS_DLL *GEOSSharedPaths(
     const GEOSGeometry* g2);
 ///@}
 
-/* ========== Buffer related functions ========== */
+/* ========== Clustering functions ========== */
 /** @name Clustering
 * Functions for clustering geometries
 */
+
+static const unsigned GEOS_CLUSTER_NONE = 4294967295;
+
 ///@{
 /**
  * @brief GEOSClusterDBSCAN
@@ -3804,51 +3811,57 @@ extern GEOSGeometry GEOS_DLL *GEOSSharedPaths(
  * @param g a collection of geometries to be clustered
  * @param eps distance parameter for clustering
  * @param minPoints density parameter for clustering
- * @return GeometryCollection whose components represent individual clusters
+ * @param numClusters the number of clusters formed
+ * @return an array of cluster identifiers
  */
-extern GEOSGeometry GEOS_DLL *GEOSClusterDBSCAN(GEOSGeometry* g, double eps, unsigned minPoints);
+extern unsigned GEOS_DLL* GEOSClusterDBSCAN(const GEOSGeometry* g, double eps, unsigned minPoints,
+        unsigned* numClusters);
 
 /**
  * @brief GEOSClusterGeometryDistance
  *
  * Cluster geometries according to a distance threshold
  *
  * @param g a collection of geometries to be clustered
- * @param d minimim distance between geometries in the same cluster
- * @return GeometryCollection whose components represent individual clusters
+ * @param d minimum distance between geometries in the same cluster
+ * @param numClusters the number of clusters formed
+ * @return an array of cluster identifiers
  */
-extern GEOSGeometry GEOS_DLL *GEOSClusterGeometryDistance(GEOSGeometry* g, double d);
+extern unsigned GEOS_DLL* GEOSClusterGeometryDistance(const GEOSGeometry* g, double d, unsigned* numClusters);
 
 /**
  * @brief GEOSClusterGeometryIntersects
  *
  * Cluster geometries that intersect
  *
  * @param g a collection of geometries to be clustered
- * @return GeometryCollection whose components represent individual clusters
+ * @param numClusters the number of clusters formed
+ * @return an array of cluster identifiers
  */
-extern GEOSGeometry GEOS_DLL *GEOSClusterGeometryIntersects(GEOSGeometry* g);
+extern unsigned GEOS_DLL* GEOSClusterGeometryIntersects(const GEOSGeometry* g, unsigned* numClusters);
 
 /**
  * @brief GEOSClusterEnvelopeDistance
  *
  * Cluster geometries according to an envelope distance threshold
  *
  * @param g a collection of geometries to be clustered
- * @param d minimim envelope distance between geometries in the same cluster
- * @return GeometryCollection whose components represent individual clusters
+ * @param d minimum envelope distance between geometries in the same cluster
+ * @param numClusters the number of clusters formed
+ * @return an array of cluster identifiers
  */
-extern GEOSGeometry GEOS_DLL *GEOSClusterEnvelopeDistance(GEOSGeometry* g, double d);
+extern unsigned GEOS_DLL* GEOSClusterEnvelopeDistance(const GEOSGeometry* g, double d, unsigned* numClusters);
 
 /**
  * @brief GEOSClusterEnvelopeIntersects
  *
  * Cluster geometries whose envelopes intersect
  *
  * @param g
- * @return GeometryCollection whose components represent individual clusters
+ * @param numClusters the number of clusters formed
+ * @return an array of cluster identifiers
  */
-extern GEOSGeometry GEOS_DLL *GEOSClusterEnvelopeIntersects(GEOSGeometry* g);
+extern unsigned GEOS_DLL* GEOSClusterEnvelopeIntersects(const GEOSGeometry* g, unsigned* numClusters);
 ///@}
 
 /* ========== Buffer related functions ========== */
@@ -5064,9 +5077,9 @@ extern char GEOS_DLL GEOSEqualsIdentical(
 
 /**
 * Calculate the [DE9IM](https://en.wikipedia.org/wiki/DE-9IM) string for a geometry pair
-* and compare against a DE9IM pattern. 
+* and compare against a DE9IM pattern.
 * Returns true if the computed matrix matches the pattern.
-* The pattern is a 9-character string 
+* The pattern is a 9-character string
 * containing symbols in the set "012TF*".
 * "012F" match the corresponding dimension symbol;
 * "T" matches any non-empty dimension; "*" matches any dimension.

capi/geos_ts_c.cpp

@@ -953,53 +953,74 @@ extern "C" {
         });
     }
 
-    Geometry*
-    GEOSClusterDBSCAN_r(GEOSContextHandle_t extHandle, Geometry* g, double eps, unsigned minPoints)
+    static unsigned* capi_clusters(const Geometry* g,
+                                   geos::operation::cluster::AbstractClusterFinder& finder,
+                                   unsigned* numClusters)
+    {
+        std::vector<const Geometry*> input{g->getNumGeometries()};
+        for (std::size_t i = 0; i < input.size(); i++) {
+            input[i] = g->getGeometryN(i);
+        }
+
+        auto result = finder.cluster(input);
+
+        if (numClusters) {
+            *numClusters = static_cast<unsigned>(result.getNumClusters());
+        }
+
+        auto cluster_ids = result.getClusterIds(GEOS_CLUSTER_NONE);
+        unsigned* ids = (unsigned*) malloc(cluster_ids.size() * sizeof(unsigned));
+        for (std::size_t i = 0; i < cluster_ids.size(); i++) {
+            ids[i] = static_cast<unsigned>(cluster_ids[i]);
+        }
+
+        return ids;
+    }
+
+    unsigned*
+    GEOSClusterDBSCAN_r(GEOSContextHandle_t extHandle, const Geometry* g, double eps, unsigned minPoints,
+                        unsigned* numClusters)
     {
         return execute(extHandle, [&]() {
-            std::unique_ptr<Geometry> in(g);
             geos::operation::cluster::DBSCANClusterFinder finder(eps, minPoints);
-            return finder.clusterToCollection(std::move(in)).release();
+
+            return capi_clusters(g, finder, numClusters);
         });
     }
 
-    Geometry*
-    GEOSClusterGeometryIntersects_r(GEOSContextHandle_t extHandle, Geometry* g)
+    unsigned*
+    GEOSClusterGeometryIntersects_r(GEOSContextHandle_t extHandle, const Geometry* g, unsigned* numClusters)
     {
         return execute(extHandle, [&]() {
-            std::unique_ptr<Geometry> in(g);
             geos::operation::cluster::GeometryIntersectsClusterFinder finder;
-            return finder.clusterToCollection(std::move(in)).release();
+            return capi_clusters(g, finder, numClusters);
         });
     }
 
-    Geometry*
-    GEOSClusterEnvelopeIntersects_r(GEOSContextHandle_t extHandle, Geometry* g)
+    unsigned*
+    GEOSClusterEnvelopeIntersects_r(GEOSContextHandle_t extHandle, const Geometry* g, unsigned* numClusters)
     {
         return execute(extHandle, [&]() {
-            std::unique_ptr<Geometry> in(g);
             geos::operation::cluster::EnvelopeIntersectsClusterFinder finder;
-            return finder.clusterToCollection(std::move(in)).release();
+            return capi_clusters(g, finder, numClusters);
         });
     }
 
-    Geometry*
-    GEOSClusterEnvelopeDistance_r(GEOSContextHandle_t extHandle, Geometry* g, double d)
+    unsigned*
+    GEOSClusterEnvelopeDistance_r(GEOSContextHandle_t extHandle, const Geometry* g, double d, unsigned* numClusters)
     {
         return execute(extHandle, [&]() {
-            std::unique_ptr<Geometry> in(g);
             geos::operation::cluster::EnvelopeDistanceClusterFinder finder(d);
-            return finder.clusterToCollection(std::move(in)).release();
+            return capi_clusters(g, finder, numClusters);
         });
     }
 
-    Geometry*
-    GEOSClusterGeometryDistance_r(GEOSContextHandle_t extHandle, Geometry* g, double d)
+    unsigned*
+    GEOSClusterGeometryDistance_r(GEOSContextHandle_t extHandle, const Geometry* g, double d, unsigned* numClusters)
     {
         return execute(extHandle, [&]() {
-            std::unique_ptr<Geometry> in(g);
             geos::operation::cluster::GeometryDistanceClusterFinder finder(d);
-            return finder.clusterToCollection(std::move(in)).release();
+            return capi_clusters(g, finder, numClusters);
         });
     }