ST_Subdivide()

Datum ST_Subdivide

(

PG_FUNCTION_ARGS

)

Definition at line 330 of file lwgeom_dump.c.

References GEOMDUMPNODE_T::geom, geometry_serialize(), lwgeom_from_gserialized(), lwgeom_subdivide(), LWCOLLECTION::ngeoms, and POSTGIS_GEOS_VERSION.

{
#if POSTGIS_GEOS_VERSION < 35

        elog(ERROR, "The GEOS version this PostGIS binary "
                "was compiled against (%d) doesn't support "
                "'%s' function (3.5.0+ required)",
                POSTGIS_GEOS_VERSION, __func__);
        PG_RETURN_NULL();

#else /* POSTGIS_GEOS_VERSION >= 35 */

        typedef struct
        {
                int nextgeom;
                int numgeoms;
                LWCOLLECTION *col;
        } collection_fctx;

        FuncCallContext *funcctx;
        collection_fctx *fctx;
        MemoryContext oldcontext;

        /* stuff done only on the first call of the function */
        if (SRF_IS_FIRSTCALL())
        {
                GSERIALIZED *gser;
                LWGEOM *geom;
                LWCOLLECTION *col;
                int maxvertices = 256;

                /* create a function context for cross-call persistence */
                funcctx = SRF_FIRSTCALL_INIT();

                /*
                * switch to memory context appropriate for multiple function calls
                */
                oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

                /*
                * Get the geometry value
                */
                gser = PG_GETARG_GSERIALIZED_P(0);
                geom = lwgeom_from_gserialized(gser);

                /*
                * Get the max vertices value
                */
                if ( PG_NARGS() > 1 && ! PG_ARGISNULL(1) )
                        maxvertices = PG_GETARG_INT32(1);

                /*
                * Compute the subdivision of the geometry
                */
                col = lwgeom_subdivide(geom, maxvertices);

                if ( ! col )
                        SRF_RETURN_DONE(funcctx);

                /* allocate memory for user context */
                fctx = (collection_fctx *) palloc(sizeof(collection_fctx));

                /* initialize state */
                fctx->nextgeom = 0;
                fctx->numgeoms = col->ngeoms;
                fctx->col = col;

                /* save user context, switch back to function context */
                funcctx->user_fctx = fctx;
                MemoryContextSwitchTo(oldcontext);
        }

        /* stuff done on every call of the function */
        funcctx = SRF_PERCALL_SETUP();
        fctx = funcctx->user_fctx;

        if (fctx->nextgeom < fctx->numgeoms)
        {
                GSERIALIZED *gpart = geometry_serialize(fctx->col->geoms[fctx->nextgeom]);
                fctx->nextgeom++;
                SRF_RETURN_NEXT(funcctx, PointerGetDatum(gpart));
        }
        else
        {
                /* do when there is no more left */
                SRF_RETURN_DONE(funcctx);
        }

#endif /* POSTGIS_GEOS_VERSION >= 35 */
}

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