Add GEOSGeom_releaseCollection to CAPI (libgeos#882)

Add GEOSGeom_releaseCollection to CAPI, references libgeosGH-848

NEWS.md

@@ -21,6 +21,7 @@ xxxx-xx-xx
   - Voronoi: Add option to create diagram in order consistent with inputs (GH-781, Dan Baston)
   - Polygonal coverages: CoverageSimplifier (JTS-911, Martin Davis)
   - CAPI: GEOSCoverageIsValid, GEOSCoverageSimplifyVW (GH-867, Paul Ramsey)
+  - CAPI: GEOSGeom_releaseCollection (GH-848)
 
 - Fixes/Improvements:
   - WKTReader: Fix parsing of Z and M flags in WKTReader (#676 and GH-669, Dan Baston)

capi/geos_c.cpp

@@ -849,6 +849,12 @@ extern "C" {
         return GEOSGeom_createCollection_r(handle, type, geoms, ngeoms);
     }
 
+    Geometry**
+    GEOSGeom_releaseCollection(Geometry* collection, unsigned int * ngeoms)
+    {
+        return GEOSGeom_releaseCollection_r(handle, collection, ngeoms);
+    }
+
     Geometry*
     GEOSPolygonize(const Geometry* const* g, unsigned int ngeoms)
     {

capi/geos_c.h.in

@@ -736,6 +736,12 @@ extern GEOSGeometry GEOS_DLL *GEOSGeom_createCollection_r(
     GEOSGeometry* *geoms,
     unsigned int ngeoms);
 
+/** \see GEOSGeom_releaseCollection */
+extern GEOSGeometry GEOS_DLL ** GEOSGeom_releaseCollection_r(
+    GEOSContextHandle_t handle,
+    GEOSGeometry * collection,
+    unsigned int * ngeoms);
+
 /** \see GEOSGeom_createEmptyCollection */
 extern GEOSGeometry GEOS_DLL *GEOSGeom_createEmptyCollection_r(
     GEOSContextHandle_t handle, int type);
@@ -2441,6 +2447,26 @@ extern GEOSGeometry GEOS_DLL *GEOSGeom_createCollection(
     GEOSGeometry** geoms,
     unsigned int ngeoms);
 
+/**
+* Release the sub-geometries of a collection for management.
+* by the caller. The input collection remains as an empty collection,
+* that the caller is responsible for destroying. The output geometries
+* are also the responsibility of the caller, as is the containing array,
+* which must be freed with GEOSFree().
+* \param collection The collection that will have its components released.
+* \param ngeoms A pointer to a variable that will be filled with the
+*        size of the output array.
+* \return A newly allocated array of GEOSGeometry pointers.
+* \note The caller is responsible for freeing the returned array
+*       with GEOSFree() and all the elements with GEOSGeom_destroy().
+*       If called with an empty collection, null will be returned
+*       and ngeoms set to zero.
+* \since 3.4
+*/
+extern GEOSGeometry GEOS_DLL ** GEOSGeom_releaseCollection(
+    GEOSGeometry * collection,
+    unsigned int * ngeoms);
+
 /**
 * Create an empty geometry collection.
 * \param type The geometry type, enumerated by \ref GEOSGeomTypes

capi/geos_ts_c.cpp

@@ -2024,6 +2024,38 @@ extern "C" {
         });
     }
 
+    Geometry**
+    GEOSGeom_releaseCollection_r(GEOSContextHandle_t extHandle, Geometry* collection, unsigned int * ngeoms)
+    {
+        return execute(extHandle, [&]() {
+            GEOSContextHandleInternal_t* handle = reinterpret_cast<GEOSContextHandleInternal_t*>(extHandle);
+
+            if (ngeoms == nullptr) {
+                handle->ERROR_MESSAGE("Parameter ngeoms of GEOSGeom_releaseCollection_r must not be null");
+            }
+
+            GeometryCollection *col = dynamic_cast<GeometryCollection*>(collection);
+            if (!col) {
+                handle->ERROR_MESSAGE("Parameter collection of GEOSGeom_releaseCollection_r must not be a collection");
+            }
+
+            // Early exit on empty/null input
+            *ngeoms = static_cast<unsigned int>(col->getNumGeometries());
+            if (!col || *ngeoms == 0) {
+                return static_cast<Geometry**>(nullptr);
+            }
+
+            std::vector<std::unique_ptr<Geometry>> subgeoms = col->releaseGeometries();
+
+            Geometry** subgeomArray = static_cast<Geometry**>(malloc(sizeof(Geometry*) * subgeoms.size()));
+            for (std::size_t i = 0; i < subgeoms.size(); i++) {
+                subgeomArray[i] = subgeoms[i].release();
+            }
+
+            return subgeomArray;
+        });
+    }
+
     Geometry*
     GEOSPolygonize_r(GEOSContextHandle_t extHandle, const Geometry* const* g, unsigned int ngeoms)
     {

tests/unit/capi/GEOSGeom_createCollectionTest.cpp

@@ -21,7 +21,11 @@ namespace tut {
 // Common data used in test cases.
 struct test_capigeosgeom_createcollection_data {
     GEOSContextHandle_t handle_;
-    GEOSGeom geom_; // collection result
+    GEOSWKTReader * reader_;
+    GEOSGeometry * geom_;
+    GEOSGeometry ** geoms_;
+    unsigned int ngeoms_;
+
     enum { geom_size = 3 };
 
     static void
@@ -37,16 +41,31 @@ struct test_capigeosgeom_createcollection_data {
         std::fprintf(stdout, "\n");
     }
 
+    GEOSGeometry*
+    read(const char* wkt)
+    {
+        return GEOSWKTReader_read_r(handle_, reader_, wkt);
+    }
+
     test_capigeosgeom_createcollection_data()
-        : handle_(initGEOS_r(notice, notice)), geom_(nullptr)
+        : handle_(initGEOS_r(notice, notice))
+        , reader_(GEOSWKTReader_create_r(handle_))
+        , geom_(nullptr)
+        , geoms_(nullptr)
+        , ngeoms_(0)
     {
     }
 
     ~test_capigeosgeom_createcollection_data()
     {
-        GEOSGeom_destroy(geom_);
-        geom_ = nullptr;
+        if (reader_) GEOSWKTReader_destroy_r(handle_, reader_);
+        if (geom_)   GEOSGeom_destroy_r(handle_, geom_);
+        if (geoms_)  GEOSFree_r(handle_, geoms_);
         finishGEOS_r(handle_);
+        handle_ = nullptr;
+        reader_ = nullptr;
+        geom_ = nullptr;
+        geoms_ = nullptr;
     }
 };
 
@@ -126,5 +145,63 @@ void object::test<4>
     ensure(geom_ == nullptr);
 }
 
+// Release empty collection
+template<>
+template<>
+void object::test<5>
+()
+{
+    const char *wkt = "MULTIPOLYGON EMPTY";
+    geom_ = read(wkt);
+    ensure(geom_ != nullptr);
+
+    geoms_ = GEOSGeom_releaseCollection_r(handle_, geom_, &ngeoms_);
+    ensure(geoms_ == nullptr);
+    ensure(ngeoms_ == 0);
+}
+
+
+// Release generic collection
+template<>
+template<>
+void object::test<6>
+()
+{
+    const char *wkt = "GEOMETRYCOLLECTION(POINT(0 0), POINT(1 1))";
+    geom_ = read(wkt);
+    ensure(geom_ != nullptr);
+
+    geoms_ = GEOSGeom_releaseCollection_r(handle_, geom_, &ngeoms_);
+    ensure(geoms_ != nullptr);
+    ensure(ngeoms_ == 2);
+
+    for (size_t i = 0 ; i < ngeoms_; i++) {
+        ensure(GEOSGeomTypeId_r(handle_, geoms_[i]) == GEOS_POINT);
+        GEOSGeom_destroy_r(handle_, geoms_[i]);
+    }
+
+}
+
+// Release typed collection
+template<>
+template<>
+void object::test<7>
+()
+{
+    const char *wkt = "MULTIPOINT(0 0, 1 1)";
+    geom_ = read(wkt);
+    ensure(geom_ != nullptr);
+
+    geoms_ = GEOSGeom_releaseCollection_r(handle_, geom_, &ngeoms_);
+    ensure(geoms_ != nullptr);
+    ensure(ngeoms_ == 2);
+
+    for (size_t i = 0 ; i < ngeoms_; i++) {
+        ensure(GEOSGeomTypeId_r(handle_, geoms_[i]) == GEOS_POINT);
+        GEOSGeom_destroy_r(handle_, geoms_[i]);
+    }
+
+}
+
 } // namespace tut