lwhomogenize.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 2010 Olivier Courtin <olivier.courtin@oslandia.com>
 *
 **********************************************************************/


#include <stdlib.h>
#include "liblwgeom_internal.h"
#include "lwgeom_log.h"


typedef struct {
        int cnt[NUMTYPES];
        LWCOLLECTION* buf[NUMTYPES];
} HomogenizeBuffer;

static void
init_homogenizebuffer(HomogenizeBuffer *buffer)
{
        int i;
        for ( i = 0; i < NUMTYPES; i++ )
        {
                buffer->cnt[i] = 0;
                buffer->buf[i] = NULL;
        }
}

/*
static void
free_homogenizebuffer(HomogenizeBuffer *buffer)
{
        int i;
        for ( i = 0; i < NUMTYPES; i++ )
        {
                if ( buffer->buf[i] )
                {
                        lwcollection_free(buffer->buf[i]);
                }
        }
}
*/

/*
** Given a generic collection, return the "simplest" form.
**
** eg: GEOMETRYCOLLECTION(MULTILINESTRING()) => MULTILINESTRING()
**
**     GEOMETRYCOLLECTION(MULTILINESTRING(), MULTILINESTRING(), POINT())
**      => GEOMETRYCOLLECTION(MULTILINESTRING(), POINT())
**
** In general, if the subcomponents are homogeneous, return a properly
** typed collection.
** Otherwise, return a generic collection, with the subtypes in minimal
** typed collections.
*/
static void
lwcollection_build_buffer(const LWCOLLECTION *col, HomogenizeBuffer *buffer)
{
        int i;

        if ( ! col ) return;
        if ( lwgeom_is_empty(lwcollection_as_lwgeom(col)) ) return;
        for ( i = 0; i < col->ngeoms; i++ )
        {
                LWGEOM *geom = col->geoms[i];
                switch(geom->type)
                {
                        case POINTTYPE:
                        case LINETYPE:
                        case CIRCSTRINGTYPE:
                        case COMPOUNDTYPE:
                        case TRIANGLETYPE:
                        case CURVEPOLYTYPE:
                        case POLYGONTYPE:
                        {
                                /* Init if necessary */
                                if ( ! buffer->buf[geom->type] )
                                {
                                        LWCOLLECTION *bufcol = lwcollection_construct_empty(COLLECTIONTYPE, col->srid, FLAGS_GET_Z(col->flags), FLAGS_GET_M(col->flags));
                                        bufcol->type = lwtype_get_collectiontype(geom->type);
                                        buffer->buf[geom->type] = bufcol;
                                }
                                /* Add sub-geom to buffer */
                                lwcollection_add_lwgeom(buffer->buf[geom->type], lwgeom_clone(geom));
                                /* Increment count for this singleton type */
                                buffer->cnt[geom->type] = buffer->cnt[geom->type] + 1;
                        }
                        default:
                        {
                                lwcollection_build_buffer(lwgeom_as_lwcollection(geom), buffer);
                        }
                }
        }
        return;
}

static LWGEOM*
lwcollection_homogenize(const LWCOLLECTION *col)
{
        int i;
        int ntypes = 0;
        int type = 0;
        LWGEOM *outgeom = NULL;

        HomogenizeBuffer buffer;

        /* Sort all the parts into a buffer */
        init_homogenizebuffer(&buffer);
        lwcollection_build_buffer(col, &buffer);

        /* Check for homogeneity */
        for ( i = 0; i < NUMTYPES; i++ )
        {
                if ( buffer.cnt[i] > 0 )
                {
                        ntypes++;
                        type = i;
                }
        }

        /* No types? Huh. Return empty. */
        if ( ntypes == 0 )
        {
                LWCOLLECTION *outcol;
                outcol = lwcollection_construct_empty(COLLECTIONTYPE, col->srid, FLAGS_GET_Z(col->flags), FLAGS_GET_M(col->flags));
                outgeom = lwcollection_as_lwgeom(outcol);
        }
        /* One type, return homogeneous collection */
        else if ( ntypes == 1 )
        {
                LWCOLLECTION *outcol;
                outcol = buffer.buf[type];
                if ( outcol->ngeoms == 1 )
                {
                        outgeom = outcol->geoms[0];
                        outcol->ngeoms=0; lwcollection_free(outcol);
                }
                else
                {
                        outgeom = lwcollection_as_lwgeom(outcol);
                }
                outgeom->srid = col->srid;
        }
        /* Bah, more than out type, return anonymous collection */
        else if ( ntypes > 1 )
        {
                int j;
                LWCOLLECTION *outcol;
                outcol = lwcollection_construct_empty(COLLECTIONTYPE, col->srid, FLAGS_GET_Z(col->flags), FLAGS_GET_M(col->flags));
                for ( j = 0; j < NUMTYPES; j++ )
                {
                        if ( buffer.buf[j] )
                        {
                                LWCOLLECTION *bcol = buffer.buf[j];
                                if ( bcol->ngeoms == 1 )
                                {
                                        lwcollection_add_lwgeom(outcol, bcol->geoms[0]);
                                        bcol->ngeoms=0; lwcollection_free(bcol);
                                }
                                else
                                {
                                        lwcollection_add_lwgeom(outcol, lwcollection_as_lwgeom(bcol));
                                }
                        }
                }
                outgeom = lwcollection_as_lwgeom(outcol);
        }

        return outgeom;
}





/*
** Given a generic geometry, return the "simplest" form.
**
** eg:
**     LINESTRING() => LINESTRING()
**
**     MULTILINESTRING(with a single line) => LINESTRING()
**
**     GEOMETRYCOLLECTION(MULTILINESTRING()) => MULTILINESTRING()
**
**     GEOMETRYCOLLECTION(MULTILINESTRING(), MULTILINESTRING(), POINT())
**      => GEOMETRYCOLLECTION(MULTILINESTRING(), POINT())
*/
LWGEOM *
lwgeom_homogenize(const LWGEOM *geom)
{
        LWGEOM *hgeom;

        /* EMPTY Geometry */
        if (lwgeom_is_empty(geom))
        {
                if( lwgeom_is_collection(geom) )
                {
                        return lwcollection_as_lwgeom(lwcollection_construct_empty(geom->type, geom->srid, lwgeom_has_z(geom), lwgeom_has_m(geom)));
                }

                return lwgeom_clone(geom);
        }

        switch (geom->type)
        {

                /* Return simple geometries untouched */
                case POINTTYPE:
                case LINETYPE:
                case CIRCSTRINGTYPE:
                case COMPOUNDTYPE:
                case TRIANGLETYPE:
                case CURVEPOLYTYPE:
                case POLYGONTYPE:
                        return lwgeom_clone(geom);

                /* Process homogeneous geometries lightly */
                case MULTIPOINTTYPE:
                case MULTILINETYPE:
                case MULTIPOLYGONTYPE:
                case MULTICURVETYPE:
                case MULTISURFACETYPE:
                case POLYHEDRALSURFACETYPE:
                case TINTYPE:
                {
                        LWCOLLECTION *col = (LWCOLLECTION*)geom;

                        /* Strip single-entry multi-geometries down to singletons */
                        if ( col->ngeoms == 1 )
                        {
                                hgeom = lwgeom_clone((LWGEOM*)(col->geoms[0]));
                                hgeom->srid = geom->srid;
                                if (geom->bbox)
                                        hgeom->bbox = gbox_copy(geom->bbox);
                                return hgeom;
                        }

                        /* Return proper multigeometry untouched */
                        return lwgeom_clone(geom);
                }

                /* Work on anonymous collections separately */
                case COLLECTIONTYPE:
                        return lwcollection_homogenize((LWCOLLECTION *) geom);
        }

        /* Unknown type */
        lwerror("lwgeom_homogenize: Geometry Type not supported (%i)",
                lwtype_name(geom->type));

        return NULL; /* Never get here! */
}