Changeset 4847 for trunk/postgis/lwgeom_functions_basic.c

Timestamp:

11/17/09 12:03:50 (3 years ago)

Author:

pramsey

Message:

Implement ST_CollectionExtract() to pull specific homogeneous collections out of heterogeneous collections. Regressions and documentation included. (#218)

Files:

• trunk/postgis/lwgeom_functions_basic.c (modified) (2 diffs)

trunk/postgis/lwgeom_functions_basic.c

@@ -79 +79 @@
 Datum ST_GeoHash(PG_FUNCTION_ARGS);
 Datum ST_MakeEnvelope(PG_FUNCTION_ARGS);
+Datum ST_CollectionExtract(PG_FUNCTION_ARGS);
 
 void lwgeom_affine_ptarray(POINTARRAY *pa, double afac, double bfac, double cfac,
@@ -3436 +3437 @@
 
 }
+
+PG_FUNCTION_INFO_V1(ST_CollectionExtract);
+Datum ST_CollectionExtract(PG_FUNCTION_ARGS)
+{
+        PG_LWGEOM *input = (PG_LWGEOM *)PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
+        PG_LWGEOM *output;
+        LWGEOM *lwgeom = pglwgeom_deserialize(input);
+        LWCOLLECTION *lwcol = NULL;
+        int type = PG_GETARG_INT32(1);
+        int lwgeom_type = TYPE_GETTYPE(lwgeom->type);
+        
+        /* Ensure the right type was input */
+        if ( ! ( type == POINTTYPE || type == LINETYPE || type == POLYGONTYPE ) )
+        {
+                lwgeom_free(lwgeom);
+                elog(ERROR, "ST_CollectionExtract: only point, linestring and polygon may be extracted");
+                PG_RETURN_NULL();
+        }
+        
+        /* Mirror non-collections right back */
+        if ( ! lwgeom_is_collection(lwgeom_type) )
+        {
+                output = palloc(VARSIZE(input));
+                memcpy(VARDATA(output), VARDATA(input), VARSIZE(input) - VARHDRSZ);
+                SET_VARSIZE(output, VARSIZE(input));
+                lwgeom_free(lwgeom);
+                PG_RETURN_POINTER(output);
+        }
+
+        lwcol = lwcollection_extract((LWCOLLECTION*)lwgeom, type);
+        output = pglwgeom_serialize((LWGEOM*)lwcol);
+        lwgeom_free(lwgeom); 
+
+        PG_RETURN_POINTER(output);
+}