postgis_srs_search()

Datum postgis_srs_search

(

PG_FUNCTION_ARGS

)

Search for projections given extent and (optional) auth_name returns TABLE(auth_name, auth_srid, srtext, proj4text, point_sw, point_ne)

Definition at line 699 of file postgis/lwgeom_transform.c.

{
        FuncCallContext *funcctx;
        MemoryContext oldcontext;
        struct srs_data *state;
        Datum result;
 
        /*
        * On the first call, fill in the state with all
        * of the auth_name/auth_srid pairings in the
        * proj database. Then the per-call routine is just
        * one isolated call per pair.
        */
        if (SRF_IS_FIRSTCALL())
        {
                GSERIALIZED *gbounds = PG_GETARG_GSERIALIZED_P(0);
                LWGEOM *bounds = lwgeom_from_gserialized(gbounds);
                text *auth_name = PG_GETARG_TEXT_P(1);
 
                funcctx = SRF_FIRSTCALL_INIT();
                oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
 
                /*
                * Could read all authorities from database, but includes
                * authorities (IGN, OGC) that use non-integral values in
                * auth_srid. So hand-coded list for now.
                */
                state = srs_state_init();
 
                /* Run the Proj query */
                srs_find_planar(text_to_cstring(auth_name), bounds, state);
 
                /*
                * Read the TupleDesc from the FunctionCallInfo. The SQL definition
                * of the function must have the right number of fields and types
                * to match up to this C code.
                */
                if (get_call_result_type(fcinfo, 0, &funcctx->tuple_desc) != TYPEFUNC_COMPOSITE)
                {
                        ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                            errmsg("%s called with incompatible return type", __func__)));
                }
 
                BlessTupleDesc(funcctx->tuple_desc);
                funcctx->user_fctx = state;
                MemoryContextSwitchTo(oldcontext);
        }
 
        /* Stuff done on every call of the function */
        funcctx = SRF_PERCALL_SETUP();
        state = funcctx->user_fctx;
 
        /* Exit when we've read all entries */
        if (!state->num_entries ||
            state->current_entry == state->num_entries)
        {
                SRF_RETURN_DONE(funcctx);
        }
 
        /* Lookup the srtext/proj4text for this entry */
        result = srs_tuple_from_entry(
                   state->entries + state->current_entry++,
                   funcctx->tuple_desc);
 
        if (result)
                SRF_RETURN_NEXT(funcctx, result);
 
        /* Stop if lookup fails drastically */
        SRF_RETURN_DONE(funcctx);
}

References srs_data::current_entry, srs_data::entries, lwgeom_from_gserialized(), srs_data::num_entries, result, srs_find_planar(), srs_state_init(), and srs_tuple_from_entry().

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