[geos-devel] Exposing PrecisionModel, GeometryPrecisionReducer in the C API

[Sandro Mani]

Hi,

Following the initial discussion in ticket #713 [1], I'd like to discuss 
the exposing of PrecisionModel and GeometryPrecisionReducer methods in 
the C API.

Personally I'm interested in having access to the 
GeometryPrecisionReducer::reduce method, as noted in the ticket there is 
also the desire [2] to expose the GeometryFactory in the C API and allow 
creating geometries with a specified GeometryFactory. Below is an 
initial proposal.

-------------------------------------------------------------------------------

/** Precision Model **/
typedef struct GEOSPrecisionModel_t GEOSPrecisionModel;

enum GEOSPrecisionModelType {
     GEOS_PRECISION_FIXED,
     GEOS_PRECISION_FLOATING,
     GEOS_PRECISION_FLOATING_SINGLE
};

extern GEOSPrecisionModel* GEOSPrecisionModel_create(int type);
extern GEOSPrecisionModel* GEOSPrecisionModel_createFixed(double scale);
extern void GEOSPrecisionModel_destroy(GEOSPrecisionModel* model);


/** Geometry Factory **/
typedef struct GEOSGeometryFactory_t GEOSGeometryFactory;

/* pm copied, NULL for default. */
extern GEOSGeometryFactory* 
GEOSGeometryFactory_create(GEOSPrecisionModel* pm, int SRID);
extern void GEOSGeometryFactory_destroy(GEOSGeometryFactory* factory);


/** New geometry constructors **/
/* Factory needs to stay valid */
extern GEOSGeometry GEOS_DLL 
*GEOSGeometryFactory_createPoint(GEOSGeometryFactory* factory, 
GEOSCoordSequence* s);
extern GEOSGeometry GEOS_DLL 
*GEOSGeometryFactory_createEmptyPoint(GEOSGeometryFactory* factory);
extern GEOSGeometry GEOS_DLL 
*GEOSGeometryFactory_createLinearRing(GEOSGeometryFactory* factory, 
GEOSCoordSequence* s);
extern GEOSGeometry GEOS_DLL 
*GEOSGeometryFactory_createLineString(GEOSGeometryFactory* factory, 
GEOSCoordSequence* s);
extern GEOSGeometry GEOS_DLL 
*GEOSGeometryFactory_createEmptyLineString(GEOSGeometryFactory* factory);

extern GEOSGeometry GEOS_DLL 
*GEOSGeometryFactory_createEmptyPolygon(GEOSGeometryFactory* factory);
extern GEOSGeometry GEOS_DLL 
*GEOSGeometryFactory_createPolygon(GEOSGeometryFactory* factory, 
GEOSGeometry* shell, GEOSGeometry** holes, unsigned int nholes);
extern GEOSGeometry GEOS_DLL 
*GEOSGeometryFactory_createCollection(GEOSGeometryFactory* factory, int 
type, GEOSGeometry* *geoms, unsigned int ngeoms);
extern GEOSGeometry GEOS_DLL 
*GEOSGeometryFactory_createEmptyCollection(GEOSGeometryFactory* factory, 
int type);


/** Retreive factory from geometry **/
extern GEOSGeometryFactory GEOSGeom_getGeometryFactory(GEOSGeometry* geom);


/** Precision Reducer **/
typedef struct GEOSGeometryPrecisionReducer_t GEOSGeometryPrecisionReducer;

/* Factory needs to stay valid */
extern GEOSGeometryPrecisionReducer* 
GEOSGeometryPrecisionReducer_create_factory(GEOSGeometryFactory* factory);
extern GEOSGeometry* 
GEOSGeometryPrecisionReducer_reduce(GEOSGeometryPrecisionReducer* 
reducer, GEOSGeometry* geometry);
extern void 
GEOSGeometryPrecisionReducer_destroy(GEOSGeometryPrecisionReducer* reducer);

-------------------------------------------------------------------------------

Remarks:
- GEOSGeometryFactory_createXXX is closer to the C++ API, an alternative 
would be something like GEOSGeom_createXXX_factory which is closer to 
what is described in [2].
- Possibly the CoordinateSequenceFactory needs to be exposed also?

Comments appreciated. Thanks,
Sandro


[1] http://trac.osgeo.org/geos/ticket/713
[2] http://trac.osgeo.org/geos/wiki/GSoC/CAPI_PrecisionModel