postgis/lwgeom_transform.c

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/**********************************************************************
 *
 * PostGIS - Spatial Types for PostgreSQL
 * http://postgis.net
 *
 * PostGIS is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * PostGIS is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with PostGIS.  If not, see <http://www.gnu.org/licenses/>.
 *
 **********************************************************************
 *
 * Copyright (C) 2001-2003 Refractions Research Inc.
 *
 **********************************************************************/
 
 
#include "postgres.h"
#include "fmgr.h"
#include "funcapi.h"
#include "utils/builtins.h"
 
#include "../postgis_config.h"
#include "liblwgeom.h"
#include "lwgeodetic.h"
#include "stringbuffer.h"
#include "lwgeom_transform.h"
 
 
Datum transform(PG_FUNCTION_ARGS);
Datum transform_geom(PG_FUNCTION_ARGS);
Datum transform_pipeline_geom(PG_FUNCTION_ARGS);
Datum postgis_proj_version(PG_FUNCTION_ARGS);
Datum postgis_proj_compiled_version(PG_FUNCTION_ARGS);
Datum LWGEOM_asKML(PG_FUNCTION_ARGS);
 
PG_FUNCTION_INFO_V1(transform);
Datum transform(PG_FUNCTION_ARGS)
{
        GSERIALIZED* geom;
        GSERIALIZED* result=NULL;
        LWGEOM* lwgeom;
        LWPROJ *pj;
        int32 srid_to, srid_from;
 
        srid_to = PG_GETARG_INT32(1);
        if (srid_to == SRID_UNKNOWN)
        {
                elog(ERROR, "ST_Transform: %d is an invalid target SRID", SRID_UNKNOWN);
                PG_RETURN_NULL();
        }
 
        geom = PG_GETARG_GSERIALIZED_P_COPY(0);
        srid_from = gserialized_get_srid(geom);
 
        if ( srid_from == SRID_UNKNOWN )
        {
                PG_FREE_IF_COPY(geom, 0);
                elog(ERROR, "ST_Transform: Input geometry has unknown (%d) SRID", SRID_UNKNOWN);
                PG_RETURN_NULL();
        }
 
        /* Input SRID and output SRID are equal, noop */
        if ( srid_from == srid_to )
                PG_RETURN_POINTER(geom);
 
        postgis_initialize_cache();
        if ( lwproj_lookup(srid_from, srid_to, &pj) == LW_FAILURE )
        {
                PG_FREE_IF_COPY(geom, 0);
                elog(ERROR, "ST_Transform: Failure reading projections from spatial_ref_sys.");
                PG_RETURN_NULL();
        }
 
        /* now we have a geometry, and input/output PJ structs. */
        lwgeom = lwgeom_from_gserialized(geom);
        lwgeom_transform(lwgeom, pj);
        lwgeom->srid = srid_to;
 
        /* Re-compute bbox if input had one (COMPUTE_BBOX TAINTING) */
        if ( lwgeom->bbox )
        {
                lwgeom_refresh_bbox(lwgeom);
        }
 
        result = geometry_serialize(lwgeom);
        lwgeom_free(lwgeom);
        PG_FREE_IF_COPY(geom, 0);
 
        PG_RETURN_POINTER(result); /* new geometry */
}
 
PG_FUNCTION_INFO_V1(transform_geom);
Datum transform_geom(PG_FUNCTION_ARGS)
{
        GSERIALIZED *gser, *gser_result=NULL;
        LWGEOM *geom;
        char *input_srs, *output_srs;
        int32 result_srid;
        int rv;
 
        /* Take a copy, since we will be altering the coordinates */
        gser = PG_GETARG_GSERIALIZED_P_COPY(0);
 
        /* Convert from text to cstring for libproj */
        input_srs = text_to_cstring(PG_GETARG_TEXT_P(1));
        output_srs = text_to_cstring(PG_GETARG_TEXT_P(2));
        result_srid = PG_GETARG_INT32(3);
 
        /* now we have a geometry, and input/output PJ structs. */
        geom = lwgeom_from_gserialized(gser);
        rv = lwgeom_transform_from_str(geom, input_srs, output_srs);
        pfree(input_srs);
        pfree(output_srs);
 
        if (rv == LW_FAILURE)
        {
                elog(ERROR, "coordinate transformation failed");
                PG_RETURN_NULL();
        }
 
        /* Re-compute bbox if input had one (COMPUTE_BBOX TAINTING) */
        geom->srid = result_srid;
        if (geom->bbox)
                lwgeom_refresh_bbox(geom);
 
        gser_result = geometry_serialize(geom);
        lwgeom_free(geom);
        PG_FREE_IF_COPY(gser, 0);
 
        PG_RETURN_POINTER(gser_result); /* new geometry */
}
 
 
PG_FUNCTION_INFO_V1(transform_pipeline_geom);
Datum transform_pipeline_geom(PG_FUNCTION_ARGS)
{
        GSERIALIZED *gser, *gser_result=NULL;
        LWGEOM *geom;
        char *input_pipeline;
        bool is_forward;
        int32 result_srid;
        int rv;
 
        /* Take a copy, since we will be altering the coordinates */
        gser = PG_GETARG_GSERIALIZED_P_COPY(0);
 
        /* Convert from text to cstring for libproj */
        input_pipeline = text_to_cstring(PG_GETARG_TEXT_P(1));
        is_forward = PG_GETARG_BOOL(2);
        result_srid = PG_GETARG_INT32(3);
 
        geom = lwgeom_from_gserialized(gser);
        rv = lwgeom_transform_pipeline(geom, input_pipeline, is_forward);
        pfree(input_pipeline);
 
        if (rv == LW_FAILURE)
        {
                elog(ERROR, "coordinate transformation failed");
                PG_RETURN_NULL();
        }
 
        /* Re-compute bbox if input had one (COMPUTE_BBOX TAINTING) */
        geom->srid = result_srid;
        if (geom->bbox)
                lwgeom_refresh_bbox(geom);
 
        gser_result = geometry_serialize(geom);
        lwgeom_free(geom);
        PG_FREE_IF_COPY(gser, 0);
 
        PG_RETURN_POINTER(gser_result); /* new geometry */
}
 
 
PG_FUNCTION_INFO_V1(postgis_proj_version);
Datum postgis_proj_version(PG_FUNCTION_ARGS)
{
        stringbuffer_t sb;
 
        PJ_INFO pji = proj_info();
        stringbuffer_init(&sb);
        stringbuffer_append(&sb, pji.version);
 
#if POSTGIS_PROJ_VERSION >= 70100
 
        stringbuffer_aprintf(&sb,
                " NETWORK_ENABLED=%s",
                proj_context_is_network_enabled(NULL) ? "ON" : "OFF");
 
        if (proj_context_get_url_endpoint(NULL))
                stringbuffer_aprintf(&sb, " URL_ENDPOINT=%s", proj_context_get_url_endpoint(NULL));
 
        if (proj_context_get_user_writable_directory(NULL, 0))
                stringbuffer_aprintf(&sb, " USER_WRITABLE_DIRECTORY=%s", proj_context_get_user_writable_directory(NULL, 0));
 
        if (proj_context_get_database_path(NULL))
                stringbuffer_aprintf(&sb, " DATABASE_PATH=%s", proj_context_get_database_path(NULL));
 
#endif
 
        PG_RETURN_POINTER(cstring_to_text(stringbuffer_getstring(&sb)));
}
 
PG_FUNCTION_INFO_V1(postgis_proj_compiled_version);
Datum postgis_proj_compiled_version(PG_FUNCTION_ARGS)
{
  static char ver[64];
  text *result;
  sprintf(
    ver,
    "%d.%d.%d",
    (POSTGIS_PROJ_VERSION/10000),
    ((POSTGIS_PROJ_VERSION%10000)/100),
    ((POSTGIS_PROJ_VERSION)%100)
  );
 
  result = cstring_to_text(ver);
  PG_RETURN_POINTER(result);
}
 
PG_FUNCTION_INFO_V1(LWGEOM_asKML);
Datum LWGEOM_asKML(PG_FUNCTION_ARGS)
{
        LWGEOM *lwgeom;
        lwvarlena_t *kml;
        const char *default_prefix = ""; /* default prefix */
        char *prefixbuf;
        const char *prefix = default_prefix;
        int32_t srid_from;
        const int32_t srid_to = 4326;
 
        /* Get the geometry */
        GSERIALIZED *geom = PG_GETARG_GSERIALIZED_P_COPY(0);
        int precision = PG_GETARG_INT32(1);
        text *prefix_text = PG_GETARG_TEXT_P(2);
        srid_from = gserialized_get_srid(geom);
 
        if ( srid_from == SRID_UNKNOWN )
        {
                PG_FREE_IF_COPY(geom, 0);
                elog(ERROR, "ST_AsKML: Input geometry has unknown (%d) SRID", SRID_UNKNOWN);
                PG_RETURN_NULL();
        }
 
        /* Condition precision */
        if (precision < 0)
                precision = 0;
 
        if (VARSIZE_ANY_EXHDR(prefix_text) > 0)
        {
                /* +2 is one for the ':' and one for term null */
                prefixbuf = palloc(VARSIZE_ANY_EXHDR(prefix_text)+2);
                memcpy(prefixbuf, VARDATA(prefix_text),
                       VARSIZE_ANY_EXHDR(prefix_text));
                /* add colon and null terminate */
                prefixbuf[VARSIZE_ANY_EXHDR(prefix_text)] = ':';
                prefixbuf[VARSIZE_ANY_EXHDR(prefix_text)+1] = '\0';
                prefix = prefixbuf;
        }
 
        lwgeom = lwgeom_from_gserialized(geom);
 
        if (srid_from != srid_to)
        {
                LWPROJ *pj;
                if (lwproj_lookup(srid_from, srid_to, &pj) == LW_FAILURE)
                {
                        PG_FREE_IF_COPY(geom, 0);
                        elog(ERROR, "ST_AsKML: Failure reading projections from spatial_ref_sys.");
                        PG_RETURN_NULL();
                }
                lwgeom_transform(lwgeom, pj);
        }
 
        kml = lwgeom_to_kml2(lwgeom, precision, prefix);
        if (kml)
                PG_RETURN_TEXT_P(kml);
        PG_RETURN_NULL();
}
 
/********************************************************************************
 * PROJ database reading functions
 */
 
struct srs_entry {
        text* auth_name;
        text* auth_code;
        double sort;
};
 
struct srs_data {
        struct srs_entry* entries;
        uint32_t num_entries;
        uint32_t capacity;
        uint32_t current_entry;
};
 
static int
srs_entry_cmp (const void *a, const void *b)
{
        const struct srs_entry *entry_a = (const struct srs_entry*)(a);
        const struct srs_entry *entry_b = (const struct srs_entry*)(b);
        if      (entry_a->sort < entry_b->sort) return -1;
        else if (entry_a->sort > entry_b->sort) return 1;
        else return 0;
}
 
static Datum
srs_tuple_from_entry(const struct srs_entry* entry, TupleDesc tuple_desc)
{
        HeapTuple tuple;
        Datum tuple_data[7] = {0, 0, 0, 0, 0, 0, 0};
        bool  tuple_null[7] = {true, true, true, true, true, true, true};
        PJ_CONTEXT * ctx = NULL;
        const char * const empty_options[2] = {NULL};
        const char * const wkt_options[2] = {"MULTILINE=NO", NULL};
        const char * srtext;
        const char * proj4text;
        const char * srname;
        double w_lon, s_lat, e_lon, n_lat;
        int ok;
 
        PJ *obj = proj_create_from_database(ctx,
                    text_to_cstring(entry->auth_name),
                    text_to_cstring(entry->auth_code),
                    PJ_CATEGORY_CRS, 0, empty_options);
 
        if (!obj)
                return (Datum) 0;
 
        srtext = proj_as_wkt(ctx, obj, PJ_WKT1_GDAL, wkt_options);
        proj4text = proj_as_proj_string(ctx, obj, PJ_PROJ_4, empty_options);
        srname = proj_get_name(obj);
        ok = proj_get_area_of_use(ctx, obj, &w_lon, &s_lat, &e_lon, &n_lat, NULL);
 
        if (entry->auth_name) {
                tuple_data[0] = PointerGetDatum(entry->auth_name);
                tuple_null[0] = false;
        }
 
        if (entry->auth_code) {
                tuple_data[1] = PointerGetDatum(entry->auth_code);
                tuple_null[1] = false;
        }
 
        if (srname) {
                tuple_data[2] = PointerGetDatum(cstring_to_text(srname));
                tuple_null[2] = false;
        }
 
        if (srtext) {
                tuple_data[3] = PointerGetDatum(cstring_to_text(srtext));
                tuple_null[3] = false;
        }
 
        if (proj4text) {
                tuple_data[4] = PointerGetDatum(cstring_to_text(proj4text));
                tuple_null[4] = false;
        }
 
        if (ok) {
                LWPOINT *p_sw = lwpoint_make2d(4326, w_lon, s_lat);
                LWPOINT *p_ne = lwpoint_make2d(4326, e_lon, n_lat);
                GSERIALIZED *g_sw = geometry_serialize((LWGEOM*)p_sw);
                GSERIALIZED *g_ne = geometry_serialize((LWGEOM*)p_ne);
                tuple_data[5] = PointerGetDatum(g_sw);
                tuple_null[5] = false;
                tuple_data[6] = PointerGetDatum(g_ne);
                tuple_null[6] = false;
        }
 
        tuple = heap_form_tuple(tuple_desc, tuple_data, tuple_null);
        proj_destroy(obj);
 
        return HeapTupleGetDatum(tuple);
}
 
static struct srs_data *
srs_state_init()
{
        struct srs_data *state = palloc0(sizeof(*state));
        state->capacity = 8192;
        state->num_entries = 0;
        state->entries = palloc0(state->capacity * sizeof(*(state->entries)));
        return state;
}
 
static void
srs_state_memcheck(struct srs_data *state)
{
        if (state->num_entries == state->capacity)
        {
                state->capacity *= 2;
                state->entries = repalloc(state->entries, state->capacity * sizeof(*(state->entries)));
        }
        return;
}
 
static void
srs_state_codes(const char* auth_name, struct srs_data *state)
{
        /*
        * Only a subset of supported proj types actually
        * show up in spatial_ref_sys
        */
        #define ntypes 3
        PJ_TYPE types[ntypes] = {PJ_TYPE_PROJECTED_CRS, PJ_TYPE_GEOGRAPHIC_CRS, PJ_TYPE_COMPOUND_CRS};
        uint32_t j;
 
        for (j = 0; j < ntypes; j++)
        {
                PJ_CONTEXT *ctx = NULL;
                int allow_deprecated = 0;
                PJ_TYPE type = types[j];
                PROJ_STRING_LIST codes_ptr = proj_get_codes_from_database(ctx, auth_name, type, allow_deprecated);
                PROJ_STRING_LIST codes = codes_ptr;
                const char *code;
                while(codes && *codes)
                {
                        /* Read current code and move forward one entry */
                        code = *codes++;
                        /* Ensure there is space in the entry list */
                        srs_state_memcheck(state);
 
                        /* Write the entry into the entry list and increment */
                        state->entries[state->num_entries].auth_name = cstring_to_text(auth_name);
                        state->entries[state->num_entries].auth_code = cstring_to_text(code);
                        state->num_entries++;
                }
                /* Clean up system allocated memory */
                proj_string_list_destroy(codes_ptr);
        }
}
 
static void
srs_find_planar(const char *auth_name, const LWGEOM *bounds, struct srs_data *state)
{
        int32_t srid_from = lwgeom_get_srid(bounds);
        const int32_t srid_to = 4326;
        GBOX gbox = *(lwgeom_get_bbox(bounds));
        PJ_TYPE types[1] = {PJ_TYPE_PROJECTED_CRS};
        PROJ_CRS_INFO **crs_list_ptr, **crs_list;
        int crs_count;
        PJ_CONTEXT *ctx = NULL;
 
        PROJ_CRS_LIST_PARAMETERS *params = proj_get_crs_list_parameters_create();
        params->types = types;
        params->typesCount = 1;
        params->crs_area_of_use_contains_bbox = true;
        params->bbox_valid = true;
        params->allow_deprecated = false;
 
#if POSTGIS_PROJ_VERSION >= 80100
        params->celestial_body_name = "Earth";
#endif
 
        if (srid_from != srid_to)
        {
                LWPROJ *pj;
                if (lwproj_lookup(srid_from, srid_to, &pj) == LW_FAILURE)
                        elog(ERROR, "%s: Lookup of SRID %u => %u transform failed",
                            __func__, srid_from, srid_to);
 
                box3d_transform(&gbox, pj);
        }
 
        params->west_lon_degree = gbox.xmin;
        params->south_lat_degree = gbox.ymin;
        params->east_lon_degree = gbox.xmax;
        params->north_lat_degree = gbox.ymax;
 
        crs_list = crs_list_ptr = proj_get_crs_info_list_from_database(
                                    ctx, auth_name, params, &crs_count);
 
        /* TODO, throw out really huge / dumb areas? */
 
        while (crs_list && *crs_list)
        {
                /* Read current crs and move forward one entry */
                PROJ_CRS_INFO *crs = *crs_list++;
 
                /* Read the corners of the CRS area of use */
                double area;
                double height = crs->north_lat_degree - crs->south_lat_degree;
                double width = crs->east_lon_degree - crs->west_lon_degree;
                if (width < 0.0)
                        width = 360 - (crs->west_lon_degree - crs->east_lon_degree);
                area = width * height;
 
                /* Ensure there is space in the entry list */
                srs_state_memcheck(state);
 
                /* Write the entry into the entry list and increment */
                state->entries[state->num_entries].auth_name = cstring_to_text(crs->auth_name);
                state->entries[state->num_entries].auth_code = cstring_to_text(crs->code);
                state->entries[state->num_entries].sort = area;
                state->num_entries++;
        }
 
        /* Put the list of entries into order of area size, smallest to largest */
        qsort(state->entries, state->num_entries, sizeof(struct srs_data), srs_entry_cmp);
 
        proj_crs_info_list_destroy(crs_list_ptr);
        proj_get_crs_list_parameters_destroy(params);
}
 
Datum postgis_srs_entry(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(postgis_srs_entry);
Datum postgis_srs_entry(PG_FUNCTION_ARGS)
{
        Datum result;
        struct srs_entry entry;
        text* auth_name = PG_GETARG_TEXT_P(0);
        text* auth_code = PG_GETARG_TEXT_P(1);
        TupleDesc tuple_desc;
 
        if (get_call_result_type(fcinfo, 0, &tuple_desc) != TYPEFUNC_COMPOSITE)
        {
                ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                        errmsg("%s called with incompatible return type", __func__)));
        }
        BlessTupleDesc(tuple_desc);
 
        entry.auth_name = auth_name;
        entry.auth_code = auth_code;
        result = srs_tuple_from_entry(&entry, tuple_desc);
 
        if (result)
                PG_RETURN_DATUM(srs_tuple_from_entry(&entry, tuple_desc));
        else
                PG_RETURN_NULL();
}
 
 
Datum postgis_srs_entry_all(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(postgis_srs_entry_all);
Datum postgis_srs_entry_all(PG_FUNCTION_ARGS)
{
        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())
        {
                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();
                srs_state_codes("EPSG", state);
                srs_state_codes("ESRI", state);
                srs_state_codes("IAU_2015", 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);
}
 
 
Datum postgis_srs_codes(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(postgis_srs_codes);
Datum postgis_srs_codes(PG_FUNCTION_ARGS)
{
        FuncCallContext *funcctx;
        MemoryContext oldcontext;
        struct srs_data *state;
        Datum result;
        text* auth_name = PG_GETARG_TEXT_P(0);
        text* auth_code;
 
        /*
        * 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())
        {
                /*
                * Only a subset of supported proj types actually
                * show up in spatial_ref_sys
                */
                funcctx = SRF_FIRSTCALL_INIT();
                oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
                state = srs_state_init();
                srs_state_codes(text_to_cstring(auth_name), state);
                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);
        }
 
        /* Read the code for this entry */
        auth_code = state->entries[state->current_entry++].auth_code;
        result = PointerGetDatum(auth_code);
 
        /* We are returning setof(text) */
        if (result)
                SRF_RETURN_NEXT(funcctx, result);
 
        /* Stop if lookup fails drastically */
        SRF_RETURN_DONE(funcctx);
        SRF_RETURN_DONE(funcctx);
}
 
 
Datum postgis_srs_search(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(postgis_srs_search);
Datum postgis_srs_search(PG_FUNCTION_ARGS)
{
        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);
}