LWGEOM_dump_rings()

Datum LWGEOM_dump_rings

(

PG_FUNCTION_ARGS

)

Definition at line 221 of file lwgeom_dump.c.

{
        GSERIALIZED *pglwgeom;
        LWGEOM *lwgeom;
        FuncCallContext *funcctx;
        struct POLYDUMPSTATE *state;
        TupleDesc tupdesc;
        HeapTuple tuple;
        AttInMetadata *attinmeta;
        MemoryContext oldcontext, newcontext;
        Datum result;
        char address[256];
        char *values[2];
 
        if (SRF_IS_FIRSTCALL())
        {
                funcctx = SRF_FIRSTCALL_INIT();
                newcontext = funcctx->multi_call_memory_ctx;
 
                oldcontext = MemoryContextSwitchTo(newcontext);
 
                pglwgeom = PG_GETARG_GSERIALIZED_P_COPY(0);
                if ( gserialized_get_type(pglwgeom) != POLYGONTYPE )
                {
                        elog(ERROR, "Input is not a polygon");
                }
 
                lwgeom = lwgeom_from_gserialized(pglwgeom);
 
                /* Create function state */
                state = lwalloc(sizeof(struct POLYDUMPSTATE));
                state->poly = lwgeom_as_lwpoly(lwgeom);
                assert (state->poly);
                state->ringnum=0;
 
                funcctx->user_fctx = state;
 
                /*
                 * Build a tuple description for an
                 * geometry_dump tuple
                 */
                get_call_result_type(fcinfo, 0, &tupdesc);
                BlessTupleDesc(tupdesc);
 
                /*
                 * generate attribute metadata needed later to produce
                 * tuples from raw C strings
                 */
                attinmeta = TupleDescGetAttInMetadata(tupdesc);
                funcctx->attinmeta = attinmeta;
 
                MemoryContextSwitchTo(oldcontext);
        }
 
        /* stuff done on every call of the function */
        funcctx = SRF_PERCALL_SETUP();
        newcontext = funcctx->multi_call_memory_ctx;
 
        /* get state */
        state = funcctx->user_fctx;
 
        /* Loop trough polygon rings */
        while (state->ringnum < state->poly->nrings )
        {
                LWPOLY* poly = state->poly;
                POINTARRAY *ring;
                LWGEOM* ringgeom;
 
                /* Switch to an appropriate memory context for POINTARRAY
                 * cloning and hexwkb allocation */
                oldcontext = MemoryContextSwitchTo(newcontext);
 
                /* We need a copy of input ring here */
                ring = ptarray_clone_deep(poly->rings[state->ringnum]);
 
                /* Construct another polygon with shell only */
                ringgeom = (LWGEOM*)lwpoly_construct(
                               poly->srid,
                               NULL, /* TODO: could use input bounding box here */
                               1, /* one ring */
                               &ring);
 
                /* Write path as ``{ <ringnum> }'' */
                sprintf(address, "{%d}", state->ringnum);
 
                values[0] = address;
                values[1] = lwgeom_to_hexwkb_buffer(ringgeom, WKB_EXTENDED);
 
                MemoryContextSwitchTo(oldcontext);
 
                tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
                result = HeapTupleGetDatum(tuple);
                ++state->ringnum;
                SRF_RETURN_NEXT(funcctx, result);
        }
 
        SRF_RETURN_DONE(funcctx);
 
}

References gserialized_get_type(), lwalloc(), lwgeom_as_lwpoly(), lwgeom_from_gserialized(), lwgeom_to_hexwkb_buffer(), lwpoly_construct(), LWPOLY::nrings, POLYDUMPSTATE::poly, POLYGONTYPE, ptarray_clone_deep(), result, POLYDUMPSTATE::ringnum, LWPOLY::rings, LWPOLY::srid, and WKB_EXTENDED.

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