lwgeom_dump.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 2001-2009 Refractions Research Inc.
 *
 **********************************************************************/


#include <math.h>
#include <float.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <assert.h>

#include "postgres.h"
#include "fmgr.h"
#include "utils/elog.h"
#include "utils/array.h"
#include "utils/geo_decls.h"
#include "funcapi.h"

#include "../postgis_config.h"
#include "liblwgeom.h"
#include "lwgeom_pg.h"


Datum LWGEOM_dump(PG_FUNCTION_ARGS);
Datum LWGEOM_dump_rings(PG_FUNCTION_ARGS);
Datum ST_Subdivide(PG_FUNCTION_ARGS);

typedef struct GEOMDUMPNODE_T
{
        int idx;
        LWGEOM *geom;
}
GEOMDUMPNODE;

#define MAXDEPTH 32
typedef struct GEOMDUMPSTATE
{
        int stacklen;
        GEOMDUMPNODE *stack[MAXDEPTH];
        LWGEOM *root;
}
GEOMDUMPSTATE;

#define PUSH(x,y) ((x)->stack[(x)->stacklen++]=(y))
#define LAST(x) ((x)->stack[(x)->stacklen-1])
#define POP(x) (--((x)->stacklen))


PG_FUNCTION_INFO_V1(LWGEOM_dump);
Datum LWGEOM_dump(PG_FUNCTION_ARGS)
{
        GSERIALIZED *pglwgeom;
        LWCOLLECTION *lwcoll;
        LWGEOM *lwgeom;
        FuncCallContext *funcctx;
        GEOMDUMPSTATE *state;
        GEOMDUMPNODE *node;
        TupleDesc tupdesc;
        HeapTuple tuple;
        AttInMetadata *attinmeta;
        MemoryContext oldcontext, newcontext;
        Datum result;
        char address[256];
        char *ptr;
        uint32 i;
        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);
                lwgeom = lwgeom_from_gserialized(pglwgeom);

                /* Create function state */
                state = lwalloc(sizeof(GEOMDUMPSTATE));
                state->root = lwgeom;
                state->stacklen=0;

                if ( lwgeom_is_collection(lwgeom) )
                {
                        /*
                         * Push a GEOMDUMPNODE on the state stack
                         */
                        node = lwalloc(sizeof(GEOMDUMPNODE));
                        node->idx=0;
                        node->geom = lwgeom;
                        PUSH(state, node);
                }

                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;

        /* Handled simple geometries */
        if ( ! state->root ) SRF_RETURN_DONE(funcctx);
        /* Return nothing for empties */
        if ( lwgeom_is_empty(state->root) ) SRF_RETURN_DONE(funcctx);
        if ( ! lwgeom_is_collection(state->root) )
        {
                values[0] = "{}";
                values[1] = lwgeom_to_hexwkb(state->root, WKB_EXTENDED, 0);
                tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
                result = HeapTupleGetDatum(tuple);

                state->root = NULL;
                SRF_RETURN_NEXT(funcctx, result);
        }

        while (1)
        {
                node = LAST(state);
                lwcoll = (LWCOLLECTION*)node->geom;

                if ( node->idx < lwcoll->ngeoms )
                {
                        lwgeom = lwcoll->geoms[node->idx];
                        if ( ! lwgeom_is_collection(lwgeom) )
                        {
                                /* write address of current geom */
                                ptr=address;
                                *ptr++='{';
                                for (i=0; i<state->stacklen; i++)
                                {
                                        if ( i ) ptr += sprintf(ptr, ",");
                                        ptr += sprintf(ptr, "%d", state->stack[i]->idx+1);
                                }
                                *ptr++='}';
                                *ptr='\0';

                                break;
                        }

                        /*
                         * It's a collection, increment index
                         * of current node, push a new one on the
                         * stack
                         */

                        oldcontext = MemoryContextSwitchTo(newcontext);

                        node = lwalloc(sizeof(GEOMDUMPNODE));
                        node->idx=0;
                        node->geom = lwgeom;
                        PUSH(state, node);

                        MemoryContextSwitchTo(oldcontext);

                        continue;
                }

                if ( ! POP(state) ) SRF_RETURN_DONE(funcctx);
                LAST(state)->idx++;
        }

        lwgeom->srid = state->root->srid;

        values[0] = address;
        values[1] = lwgeom_to_hexwkb(lwgeom, WKB_EXTENDED, 0);
        tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
        result = TupleGetDatum(funcctx->slot, tuple);
        node->idx++;
        SRF_RETURN_NEXT(funcctx, result);
}

struct POLYDUMPSTATE
{
        int ringnum;
        LWPOLY *poly;
};

PG_FUNCTION_INFO_V1(LWGEOM_dump_rings);
Datum LWGEOM_dump_rings(PG_FUNCTION_ARGS)
{
        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(ringgeom, WKB_EXTENDED, 0);

                MemoryContextSwitchTo(oldcontext);

                tuple = BuildTupleFromCStrings(funcctx->attinmeta, values);
                result = HeapTupleGetDatum(tuple);
                ++state->ringnum;
                SRF_RETURN_NEXT(funcctx, result);
        }

        SRF_RETURN_DONE(funcctx);

}


struct FLATCOLLECTIONDUMPSTATE
{
        int geomnum;
        LWCOLLECTION *col;
};

/*
* Break an object up into smaller objects of no more than N vertices
*/
PG_FUNCTION_INFO_V1(ST_Subdivide);
Datum ST_Subdivide(PG_FUNCTION_ARGS)
{
#if POSTGIS_GEOS_VERSION < 35

        elog(ERROR, "The GEOS version this PostGIS binary "
                "was compiled against (%d) doesn't support "
                "'%s' function (3.5.0+ required)",
                POSTGIS_GEOS_VERSION, __func__);
        PG_RETURN_NULL();

#else /* POSTGIS_GEOS_VERSION >= 35 */

        typedef struct
        {
                int nextgeom;
                int numgeoms;
                LWCOLLECTION *col;
        } collection_fctx;

        FuncCallContext *funcctx;
        collection_fctx *fctx;
        MemoryContext oldcontext;

        /* stuff done only on the first call of the function */
        if (SRF_IS_FIRSTCALL())
        {
                GSERIALIZED *gser;
                LWGEOM *geom;
                LWCOLLECTION *col;
                int maxvertices = 256;

                /* create a function context for cross-call persistence */
                funcctx = SRF_FIRSTCALL_INIT();

                /*
                * switch to memory context appropriate for multiple function calls
                */
                oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

                /*
                * Get the geometry value
                */
                gser = PG_GETARG_GSERIALIZED_P(0);
                geom = lwgeom_from_gserialized(gser);

                /*
                * Get the max vertices value
                */
                if ( PG_NARGS() > 1 && ! PG_ARGISNULL(1) )
                        maxvertices = PG_GETARG_INT32(1);

                /*
                * Compute the subdivision of the geometry
                */
                col = lwgeom_subdivide(geom, maxvertices);

                if ( ! col )
                        SRF_RETURN_DONE(funcctx);

                /* allocate memory for user context */
                fctx = (collection_fctx *) palloc(sizeof(collection_fctx));

                /* initialize state */
                fctx->nextgeom = 0;
                fctx->numgeoms = col->ngeoms;
                fctx->col = col;

                /* save user context, switch back to function context */
                funcctx->user_fctx = fctx;
                MemoryContextSwitchTo(oldcontext);
        }

        /* stuff done on every call of the function */
        funcctx = SRF_PERCALL_SETUP();
        fctx = funcctx->user_fctx;

        if (fctx->nextgeom < fctx->numgeoms)
        {
                GSERIALIZED *gpart = geometry_serialize(fctx->col->geoms[fctx->nextgeom]);
                fctx->nextgeom++;
                SRF_RETURN_NEXT(funcctx, PointerGetDatum(gpart));
        }
        else
        {
                /* do when there is no more left */
                SRF_RETURN_DONE(funcctx);
        }

#endif /* POSTGIS_GEOS_VERSION >= 35 */
}