lwgeom_dumppoints.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^
 *
 **********************************************************************/
 
#include "postgres.h"
#include "fmgr.h"
#include "utils/elog.h"
#include "utils/array.h"
#include "utils/geo_decls.h"
#include "utils/lsyscache.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
 
#include "../postgis_config.h"
#include "lwgeom_pg.h"
 
#include "access/htup_details.h"
 
 
#include "liblwgeom.h"
 
/* ST_DumpPoints for postgis.
 * By Nathan Wagner, copyright disclaimed,
 * this entire file is in the public domain
 */
 
Datum LWGEOM_dumppoints(PG_FUNCTION_ARGS);
 
struct dumpnode {
        LWGEOM *geom;
        uint32_t idx; /* which member geom we're working on */
} ;
 
/* 32 is the max depth for st_dump, so it seems reasonable
 * to use the same here
 */
#define MAXDEPTH 32
struct dumpstate {
        LWGEOM  *root;
        int     stacklen; /* collections/geoms on stack */
        int     pathlen; /* polygon rings and such need extra path info */
        struct  dumpnode stack[MAXDEPTH];
        Datum   path[34]; /* two more than max depth, for ring and point */
 
        /* used to cache the type attributes for integer arrays */
        int16   typlen;
        bool    byval;
        char    align;
 
        uint32_t ring; /* ring of top polygon */
        uint32_t pt; /* point of top geom or current ring */
};
 
PG_FUNCTION_INFO_V1(LWGEOM_dumppoints);
Datum LWGEOM_dumppoints(PG_FUNCTION_ARGS) {
        FuncCallContext *funcctx;
        MemoryContext oldcontext, newcontext;
 
        GSERIALIZED *pglwgeom;
        LWCOLLECTION *lwcoll;
        LWGEOM *lwgeom;
        struct dumpstate *state;
        struct dumpnode *node;
 
        HeapTuple tuple;
        Datum pathpt[2]; /* used to construct the composite return value */
        bool isnull[2] = {0,0}; /* needed to say neither value is null */
        Datum result; /* the actual composite return value */
 
        if (SRF_IS_FIRSTCALL()) {
                funcctx = SRF_FIRSTCALL_INIT();
 
                newcontext = funcctx->multi_call_memory_ctx;
                oldcontext = MemoryContextSwitchTo(newcontext);
 
                /* get a local copy of what we're doing a dump points on */
                pglwgeom = PG_GETARG_GSERIALIZED_P_COPY(0);
                lwgeom = lwgeom_from_gserialized(pglwgeom);
 
                /* return early if nothing to do */
                if (!lwgeom || lwgeom_is_empty(lwgeom)) {
                        MemoryContextSwitchTo(oldcontext);
                        funcctx = SRF_PERCALL_SETUP();
                        SRF_RETURN_DONE(funcctx);
                }
 
                /* Create function state */
                state = lwalloc(sizeof *state);
                state->root = lwgeom;
                state->stacklen = 0;
                state->pathlen = 0;
                state->pt = 0;
                state->ring = 0;
 
                funcctx->user_fctx = state;
 
                /*
                 * Push a struct dumpnode on the state stack
                 */
 
                state->stack[0].idx = 0;
                state->stack[0].geom = lwgeom;
                state->stacklen++;
 
                /*
                 * get tuple description for return type
                 */
                if (get_call_result_type(fcinfo, 0, &funcctx->tuple_desc) != TYPEFUNC_COMPOSITE) {
                        ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                errmsg("set-valued function called in context that cannot accept a set")));
                }
 
                BlessTupleDesc(funcctx->tuple_desc);
 
                /* get and cache data for constructing int4 arrays */
                get_typlenbyvalalign(INT4OID, &state->typlen, &state->byval, &state->align);
 
                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;
 
        while (1) {
                node = &state->stack[state->stacklen-1];
                lwgeom = node->geom;
 
                /* need to return a point from this geometry */
                if (!lwgeom_is_collection(lwgeom)) {
                        /* either return a point, or pop the stack */
                        /* TODO use a union?  would save a tiny amount of stack space.
                         * probably not worth the bother
                         */
                        LWLINE  *line;
                        LWCIRCSTRING *circ;
                        LWPOLY  *poly;
                        LWTRIANGLE      *tri;
                        LWPOINT *lwpoint = NULL;
                        POINT4D pt;
 
                        if ( !lwgeom_is_empty(lwgeom) ) {
                        /*
                         * net result of switch should be to set lwpoint to the
                         * next point to return, or leave at NULL if there
                         * are no more points in the geometry
                         */
                        switch(lwgeom->type) {
                                case TRIANGLETYPE:
                                        tri = lwgeom_as_lwtriangle(lwgeom);
                                        if (state->pt == 0) {
                                                state->path[state->pathlen++] = Int32GetDatum(state->ring+1);
                                        }
                                        if (state->pt <= 3) {
                                                getPoint4d_p(tri->points, state->pt, &pt);
                                                lwpoint = lwpoint_make(tri->srid,
                                                                lwgeom_has_z(lwgeom),
                                                                lwgeom_has_m(lwgeom),
                                                                &pt);
                                        }
                                        if (state->pt > 3) {
                                                state->pathlen--;
                                        }
                                        break;
                                case POLYGONTYPE:
                                        poly = lwgeom_as_lwpoly(lwgeom);
                                        if (state->pt == poly->rings[state->ring]->npoints) {
                                                state->pt = 0;
                                                state->ring++;
                                                state->pathlen--;
                                        }
                                        if (state->pt == 0 && state->ring < poly->nrings) {
                                                /* handle new ring */
                                                state->path[state->pathlen] = Int32GetDatum(state->ring+1);
                                                state->pathlen++;
                                        }
                                        if (state->ring == poly->nrings) {
                                        } else {
                                        /* TODO should be able to directly get the point
                                         * into the point array of a fixed lwpoint
                                         */
                                        /* can't get the point directly from the ptarray because
                                         * it might be aligned wrong, so at least one memcpy
                                         * seems unavoidable
                                         * It might be possible to pass it directly to gserialized
                                         * depending how that works, it might effectively be gserialized
                                         * though a brief look at the code indicates not
                                         */
                                                getPoint4d_p(poly->rings[state->ring], state->pt, &pt);
                                                lwpoint = lwpoint_make(poly->srid,
                                                                lwgeom_has_z(lwgeom),
                                                                lwgeom_has_m(lwgeom),
                                                                &pt);
                                        }
                                        break;
                                case POINTTYPE:
                                        if (state->pt == 0) lwpoint = lwgeom_as_lwpoint(lwgeom);
                                        break;
                                case LINETYPE:
                                        line = lwgeom_as_lwline(lwgeom);
                                        if (line->points && state->pt <= line->points->npoints) {
                                                lwpoint = lwline_get_lwpoint((LWLINE*)lwgeom, state->pt);
                                        }
                                        break;
                                case CIRCSTRINGTYPE:
                                        circ = lwgeom_as_lwcircstring(lwgeom);
                                        if (circ->points && state->pt <= circ->points->npoints) {
                                                lwpoint = lwcircstring_get_lwpoint((LWCIRCSTRING*)lwgeom, state->pt);
                                        }
                                        break;
                                default:
                                        ereport(ERROR, (errcode(ERRCODE_DATA_EXCEPTION),
                                                errmsg("Invalid Geometry type %d passed to ST_DumpPoints()", lwgeom->type)));
                                }
                        }
 
                        /*
                         * At this point, lwpoint is either NULL, in which case
                         * we need to pop the geometry stack and get the next
                         * geometry, if any, or lwpoint is set and we construct
                         * a record type with the integer array of geometry
                         * indexes and the point number, and the actual point
                         * geometry itself
                         */
 
                        if (!lwpoint) {
                                /* no point, so pop the geom and look for more */
                                if (--state->stacklen == 0) SRF_RETURN_DONE(funcctx);
                                state->pathlen--;
                                continue;
                        } else {
                                /* write address of current geom/pt */
                                state->pt++;
 
                                state->path[state->pathlen] = Int32GetDatum(state->pt);
                                pathpt[0] = PointerGetDatum(construct_array(state->path, state->pathlen+1,
                                                INT4OID, state->typlen, state->byval, state->align));
 
                                pathpt[1] = PointerGetDatum(geometry_serialize((LWGEOM*)lwpoint));
 
                                tuple = heap_form_tuple(funcctx->tuple_desc, pathpt, isnull);
                                result = HeapTupleGetDatum(tuple);
                                SRF_RETURN_NEXT(funcctx, result);
                        }
                }
 
                lwcoll = (LWCOLLECTION*)node->geom;
 
                /* if a collection and we have more geoms */
                if (node->idx < lwcoll->ngeoms) {
                        /* push the next geom on the path and the stack */
                        lwgeom = lwcoll->geoms[node->idx++];
                        state->path[state->pathlen++] = Int32GetDatum(node->idx);
 
                        node = &state->stack[state->stacklen++];
                        node->idx = 0;
                        node->geom = lwgeom;
 
                        state->pt = 0;
                        state->ring = 0;
 
                        /* loop back to beginning, which will then check whatever node we just pushed */
                        continue;
                }
 
                /* no more geometries in the current collection */
                if (--state->stacklen == 0) SRF_RETURN_DONE(funcctx);
                state->pathlen--;
                state->stack[state->stacklen-1].idx++;
        }
}