| | 49 | == An Example == |
| | 50 | |
| | 51 | {{{ |
| | 52 | #!c |
| | 53 | PG_FUNCTION_INFO_V1(LWGEOM_shortestline2d); |
| | 54 | Datum LWGEOM_shortestline2d(PG_FUNCTION_ARGS) |
| | 55 | { |
| | 56 | PG_LWGEOM *result; |
| | 57 | /* Detoast the actual PgSQL varlena structures, in our case PG_LWGEOM (soon to be GSERIALIZED) */ |
| | 58 | PG_LWGEOM *geom1 = (PG_LWGEOM*)PG_DETOAST_DATUM(PG_GETARG_DATUM(0)); |
| | 59 | PG_LWGEOM *geom2 = (PG_LWGEOM*)PG_DETOAST_DATUM(PG_GETARG_DATUM(1)); |
| | 60 | /* Build LWGEOM from the varlena (soon to be with lwgeom_from_gserialized) */ |
| | 61 | LWGEOM *lwgeom1 = pglwgeom_deserialize(geom1); |
| | 62 | LWGEOM *lwgeom2 = pglwgeom_deserialize(geom2); |
| | 63 | LWGEOM *theline; |
| | 64 | |
| | 65 | |
| | 66 | if (lwgeom1->srid != lwgeom2->srid) |
| | 67 | { |
| | 68 | elog(ERROR,"Operation on two GEOMETRIES with different SRIDs\n"); |
| | 69 | PG_RETURN_NULL(); |
| | 70 | } |
| | 71 | |
| | 72 | theline = lw_dist2d_distanceline(lwgeom1, lwgeom2, lwgeom1->srid, DIST_MIN); |
| | 73 | if (lwgeom_is_empty(theline)) |
| | 74 | PG_RETURN_NULL(); |
| | 75 | |
| | 76 | /* Serialize the result back down from LWGEOM, but don't return right away */ |
| | 77 | result = pglwgeom_serialize(theline); |
| | 78 | /* First free the LWGEOMs you used */ |
| | 79 | lwgeom_free(lwgeom1); |
| | 80 | lwgeom_free(lwgeom2); |
| | 81 | |
| | 82 | /* Then call free_if_copy on the *varlena* structures you originally get as arguments */ |
| | 83 | PG_FREE_IF_COPY(geom1, 0); |
| | 84 | PG_FREE_IF_COPY(geom2, 1); |
| | 85 | |
| | 86 | /* And now return */ |
| | 87 | PG_RETURN_POINTER(result); |
| | 88 | } |
| | 89 | }}} |
