liblwgeom/lwgeom_geos.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 2011-2014 Sandro Santilli <strk@kbt.io>
 * Copyright 2015-2018 Daniel Baston <dbaston@gmail.com>
 * Copyright 2017-2018 Darafei Praliaskouski <me@komzpa.net>
 *
 **********************************************************************/
 
#include "lwgeom_geos.h"
#include "liblwgeom.h"
#include "liblwgeom_internal.h"
#include "lwgeom_log.h"
#include "lwrandom.h"
 
#include <stdarg.h>
#include <stdlib.h>
 
LWTIN* lwtin_from_geos(const GEOSGeometry* geom, uint8_t want3d);
 
#define AUTOFIX LW_TRUE
#define LWGEOM_GEOS_ERRMSG_MAXSIZE 256
char lwgeom_geos_errmsg[LWGEOM_GEOS_ERRMSG_MAXSIZE];
 
extern void
lwgeom_geos_error(const char* fmt, ...)
{
        va_list ap;
        va_start(ap, fmt);
 
        /* Call the supplied function */
        if (LWGEOM_GEOS_ERRMSG_MAXSIZE - 1 < vsnprintf(lwgeom_geos_errmsg, LWGEOM_GEOS_ERRMSG_MAXSIZE - 1, fmt, ap))
                lwgeom_geos_errmsg[LWGEOM_GEOS_ERRMSG_MAXSIZE - 1] = '\0';
 
        va_end(ap);
}
 
/* Destroy any non-null GEOSGeometry* pointers passed as arguments */
#define GEOS_FREE(...) \
do { \
        geos_destroy((sizeof((void*[]){__VA_ARGS__})/sizeof(void*)), __VA_ARGS__); \
} while (0)
 
/* Pass the latest GEOS error to lwerror, then return NULL */
#define GEOS_FAIL() \
do { \
        lwerror("%s: GEOS Error: %s", __func__, lwgeom_geos_errmsg); \
        return NULL; \
} while (0)
 
/* Pass the latest GEOS error to lwdebug, then return NULL */
#define GEOS_FAIL_DEBUG() \
        do \
        { \
                lwdebug(1, "%s: GEOS Error: %s", __func__, lwgeom_geos_errmsg); \
                return NULL; \
        } while (0)
 
#define GEOS_FREE_AND_FAIL(...) \
do { \
        GEOS_FREE(__VA_ARGS__); \
        GEOS_FAIL(); \
} while (0)
 
#define GEOS_FREE_AND_FAIL_DEBUG(...) \
        do \
        { \
                GEOS_FREE(__VA_ARGS__); \
                GEOS_FAIL_DEBUG(); \
        } while (0)
 
/* Return the consistent SRID of all inputs, or call lwerror
 * in case of SRID mismatch. */
#define RESULT_SRID(...) \
        (get_result_srid((sizeof((const void*[]){__VA_ARGS__})/sizeof(void*)), __func__,  __VA_ARGS__))
 
/* Free any non-null GEOSGeometry* pointers passed as arguments *
 * Called by GEOS_FREE, which populates 'count' */
static void geos_destroy(size_t count, ...) {
        va_list ap;
        va_start(ap, count);
        while (count--)
        {
                GEOSGeometry* g = va_arg(ap, GEOSGeometry*);
                if (g)
                {
                        GEOSGeom_destroy(g);
                }
        }
}
 
/*
**  GEOS <==> PostGIS conversion functions
**
** Default conversion creates a GEOS point array, then iterates through the
** PostGIS points, setting each value in the GEOS array one at a time.
**
*/
 
/* Return a POINTARRAY from a GEOSCoordSeq */
POINTARRAY*
ptarray_from_GEOSCoordSeq(const GEOSCoordSequence* cs, uint8_t want3d)
{
        uint32_t dims = 2;
        uint32_t size = 0, i;
        POINTARRAY* pa;
        POINT4D point = { 0.0, 0.0, 0.0, 0.0 };
 
        LWDEBUG(2, "ptarray_fromGEOSCoordSeq called");
 
        if (!GEOSCoordSeq_getSize(cs, &size)) lwerror("Exception thrown");
 
        LWDEBUGF(4, " GEOSCoordSeq size: %d", size);
 
        if (want3d)
        {
                if (!GEOSCoordSeq_getDimensions(cs, &dims)) lwerror("Exception thrown");
 
                LWDEBUGF(4, " GEOSCoordSeq dimensions: %d", dims);
 
                /* forget higher dimensions (if any) */
                if (dims > 3) dims = 3;
        }
 
        LWDEBUGF(4, " output dimensions: %d", dims);
 
        pa = ptarray_construct((dims == 3), 0, size);
 
        for (i = 0; i < size; i++)
        {
#if POSTGIS_GEOS_VERSION < 38
                GEOSCoordSeq_getX(cs, i, &(point.x));
                GEOSCoordSeq_getY(cs, i, &(point.y));
                if (dims >= 3) GEOSCoordSeq_getZ(cs, i, &(point.z));
#else
                if (dims >= 3)
                        GEOSCoordSeq_getXYZ(cs, i, &(point.x), &(point.y), &(point.z));
                else
                        GEOSCoordSeq_getXY(cs, i, &(point.x), &(point.y));
#endif
                ptarray_set_point4d(pa, i, &point);
        }
 
        return pa;
}
 
/* Return an LWGEOM from a Geometry */
LWGEOM*
GEOS2LWGEOM(const GEOSGeometry* geom, uint8_t want3d)
{
        int type = GEOSGeomTypeId(geom);
        int SRID = GEOSGetSRID(geom);
 
        /* GEOS's 0 is equivalent to our unknown as for SRID values */
        if (SRID == 0) SRID = SRID_UNKNOWN;
 
        if (want3d && !GEOSHasZ(geom))
        {
                LWDEBUG(3, "Geometry has no Z, won't provide one");
                want3d = 0;
        }
 
        switch (type)
        {
                const GEOSCoordSequence* cs;
                POINTARRAY *pa, **ppaa;
                const GEOSGeometry* g;
                LWGEOM** geoms;
                uint32_t i, ngeoms;
 
        case GEOS_POINT:
                LWDEBUG(4, "lwgeom_from_geometry: it's a Point");
                cs = GEOSGeom_getCoordSeq(geom);
                if (GEOSisEmpty(geom)) return (LWGEOM*)lwpoint_construct_empty(SRID, want3d, 0);
                pa = ptarray_from_GEOSCoordSeq(cs, want3d);
                return (LWGEOM*)lwpoint_construct(SRID, NULL, pa);
 
        case GEOS_LINESTRING:
        case GEOS_LINEARRING:
                LWDEBUG(4, "lwgeom_from_geometry: it's a LineString or LinearRing");
                if (GEOSisEmpty(geom)) return (LWGEOM*)lwline_construct_empty(SRID, want3d, 0);
 
                cs = GEOSGeom_getCoordSeq(geom);
                pa = ptarray_from_GEOSCoordSeq(cs, want3d);
                return (LWGEOM*)lwline_construct(SRID, NULL, pa);
 
        case GEOS_POLYGON:
                LWDEBUG(4, "lwgeom_from_geometry: it's a Polygon");
                if (GEOSisEmpty(geom)) return (LWGEOM*)lwpoly_construct_empty(SRID, want3d, 0);
                ngeoms = GEOSGetNumInteriorRings(geom);
                ppaa = lwalloc(sizeof(POINTARRAY*) * (ngeoms + 1));
                g = GEOSGetExteriorRing(geom);
                cs = GEOSGeom_getCoordSeq(g);
                ppaa[0] = ptarray_from_GEOSCoordSeq(cs, want3d);
                for (i = 0; i < ngeoms; i++)
                {
                        g = GEOSGetInteriorRingN(geom, i);
                        cs = GEOSGeom_getCoordSeq(g);
                        ppaa[i + 1] = ptarray_from_GEOSCoordSeq(cs, want3d);
                }
                return (LWGEOM*)lwpoly_construct(SRID, NULL, ngeoms + 1, ppaa);
 
        case GEOS_MULTIPOINT:
        case GEOS_MULTILINESTRING:
        case GEOS_MULTIPOLYGON:
        case GEOS_GEOMETRYCOLLECTION:
                LWDEBUG(4, "lwgeom_from_geometry: it's a Collection or Multi");
 
                ngeoms = GEOSGetNumGeometries(geom);
                geoms = NULL;
                if (ngeoms)
                {
                        geoms = lwalloc(sizeof(LWGEOM*) * ngeoms);
                        for (i = 0; i < ngeoms; i++)
                        {
                                g = GEOSGetGeometryN(geom, i);
                                geoms[i] = GEOS2LWGEOM(g, want3d);
                        }
                }
                return (LWGEOM*)lwcollection_construct(type, SRID, NULL, ngeoms, geoms);
 
        default:
                lwerror("GEOS2LWGEOM: unknown geometry type: %d", type);
                return NULL;
        }
}
 
GEOSCoordSeq ptarray_to_GEOSCoordSeq(const POINTARRAY*, uint8_t fix_ring);
 
GEOSCoordSeq
ptarray_to_GEOSCoordSeq(const POINTARRAY* pa, uint8_t fix_ring)
{
        uint32_t dims = 2;
        uint32_t i;
        int append_points = 0;
        const POINT3D *p3d = NULL;
        const POINT2D* p2d = NULL;
        GEOSCoordSeq sq;
 
        if (FLAGS_GET_Z(pa->flags)) dims = 3;
 
        if (fix_ring)
        {
                if (pa->npoints < 1)
                {
                        lwerror("ptarray_to_GEOSCoordSeq called with fix_ring and 0 vertices in ring, cannot fix");
                        return NULL;
                }
                else
                {
                        if (pa->npoints < 4) append_points = 4 - pa->npoints;
                        if (!ptarray_is_closed_2d(pa) && append_points == 0) append_points = 1;
                }
        }
 
        if (!(sq = GEOSCoordSeq_create(pa->npoints + append_points, dims)))
        {
                lwerror("Error creating GEOS Coordinate Sequence");
                return NULL;
        }
 
        for (i = 0; i < pa->npoints; i++)
        {
                if (dims == 3)
                {
                        p3d = getPoint3d_cp(pa, i);
                        p2d = (const POINT2D*)p3d;
                        LWDEBUGF(4, "Point: %g,%g,%g", p3d->x, p3d->y, p3d->z);
                }
                else
                {
                        p2d = getPoint2d_cp(pa, i);
                        LWDEBUGF(4, "Point: %g,%g", p2d->x, p2d->y);
                }
 
#if POSTGIS_GEOS_VERSION < 38
                GEOSCoordSeq_setX(sq, i, p2d->x);
                GEOSCoordSeq_setY(sq, i, p2d->y);
                if (dims == 3) GEOSCoordSeq_setZ(sq, i, p3d->z);
#else
                if (dims == 3)
                        GEOSCoordSeq_setXYZ(sq, i, p2d->x, p2d->y, p3d->z);
                else
                        GEOSCoordSeq_setXY(sq, i, p2d->x, p2d->y);
#endif
 
        }
 
        if (append_points)
        {
                if (dims == 3)
                {
                        p3d = getPoint3d_cp(pa, 0);
                        p2d = (const POINT2D*)p3d;
                }
                else
                        p2d = getPoint2d_cp(pa, 0);
                for (i = pa->npoints; i < pa->npoints + append_points; i++)
                {
#if POSTGIS_GEOS_VERSION < 38
                        GEOSCoordSeq_setX(sq, i, p2d->x);
                        GEOSCoordSeq_setY(sq, i, p2d->y);
#else
                        GEOSCoordSeq_setXY(sq, i, p2d->x, p2d->y);
#endif
 
                        if (dims == 3) GEOSCoordSeq_setZ(sq, i, p3d->z);
                }
        }
 
        return sq;
}
 
static inline GEOSGeometry*
ptarray_to_GEOSLinearRing(const POINTARRAY* pa, uint8_t autofix)
{
        GEOSCoordSeq sq;
        GEOSGeom g;
        sq = ptarray_to_GEOSCoordSeq(pa, autofix);
        g = GEOSGeom_createLinearRing(sq);
        return g;
}
 
GEOSGeometry*
GBOX2GEOS(const GBOX* box)
{
        GEOSGeometry* envelope;
        GEOSGeometry* ring;
        GEOSCoordSequence* seq = GEOSCoordSeq_create(5, 2);
        if (!seq) return NULL;
 
#if POSTGIS_GEOS_VERSION < 38
        GEOSCoordSeq_setX(seq, 0, box->xmin);
        GEOSCoordSeq_setY(seq, 0, box->ymin);
 
        GEOSCoordSeq_setX(seq, 1, box->xmax);
        GEOSCoordSeq_setY(seq, 1, box->ymin);
 
        GEOSCoordSeq_setX(seq, 2, box->xmax);
        GEOSCoordSeq_setY(seq, 2, box->ymax);
 
        GEOSCoordSeq_setX(seq, 3, box->xmin);
        GEOSCoordSeq_setY(seq, 3, box->ymax);
 
        GEOSCoordSeq_setX(seq, 4, box->xmin);
        GEOSCoordSeq_setY(seq, 4, box->ymin);
#else
        GEOSCoordSeq_setXY(seq, 0, box->xmin, box->ymin);
        GEOSCoordSeq_setXY(seq, 1, box->xmax, box->ymin);
        GEOSCoordSeq_setXY(seq, 2, box->xmax, box->ymax);
        GEOSCoordSeq_setXY(seq, 3, box->xmin, box->ymax);
        GEOSCoordSeq_setXY(seq, 4, box->xmin, box->ymin);
#endif
 
        ring = GEOSGeom_createLinearRing(seq);
        if (!ring)
        {
                GEOSCoordSeq_destroy(seq);
                return NULL;
        }
 
        envelope = GEOSGeom_createPolygon(ring, NULL, 0);
        if (!envelope)
        {
                GEOSGeom_destroy(ring);
                return NULL;
        }
 
        return envelope;
}
 
GEOSGeometry*
LWGEOM2GEOS(const LWGEOM* lwgeom, uint8_t autofix)
{
        GEOSCoordSeq sq;
        GEOSGeom g, shell;
        GEOSGeom* geoms = NULL;
        uint32_t ngeoms, i, j;
        int geostype;
#if LWDEBUG_LEVEL >= 4
        char* wkt;
#endif
 
        if (autofix)
        {
                /* cross fingers and try without autofix, maybe it'll work? */
                g = LWGEOM2GEOS(lwgeom, LW_FALSE);
                if (g) return g;
        }
 
        LWDEBUGF(4, "LWGEOM2GEOS got a %s", lwtype_name(lwgeom->type));
 
        if (lwgeom_has_arc(lwgeom))
        {
                LWGEOM* lwgeom_stroked = lwgeom_stroke(lwgeom, 32);
                GEOSGeometry* g = LWGEOM2GEOS(lwgeom_stroked, autofix);
                lwgeom_free(lwgeom_stroked);
                return g;
        }
 
        LWPOINT* lwp = NULL;
        LWPOLY* lwpoly = NULL;
        LWLINE* lwl = NULL;
        LWCOLLECTION* lwc = NULL;
 
        switch (lwgeom->type)
        {
        case POINTTYPE:
                lwp = (LWPOINT*)lwgeom;
 
                if (lwgeom_is_empty(lwgeom))
                        g = GEOSGeom_createEmptyPolygon();
                else
                {
#if POSTGIS_GEOS_VERSION < 38
                        sq = ptarray_to_GEOSCoordSeq(lwp->point, 0);
                        g = GEOSGeom_createPoint(sq);
#else
                        if (lwgeom_has_z(lwgeom))
                        {
                                sq = ptarray_to_GEOSCoordSeq(lwp->point, 0);
                                g = GEOSGeom_createPoint(sq);
                        }
                        else
                        {
                                const POINT2D* p = getPoint2d_cp(lwp->point, 0);
                                g = GEOSGeom_createPointFromXY(p->x, p->y);
                        }
#endif
                }
                if (!g) return NULL;
                break;
 
        case LINETYPE:
                lwl = (LWLINE*)lwgeom;
                /* TODO: if (autofix) */
                if (lwl->points->npoints == 1)
                {
                        /* Duplicate point, to make geos-friendly */
                        lwl->points = ptarray_addPoint(lwl->points,
                                                       getPoint_internal(lwl->points, 0),
                                                       FLAGS_NDIMS(lwl->points->flags),
                                                       lwl->points->npoints);
                }
                sq = ptarray_to_GEOSCoordSeq(lwl->points, 0);
                g = GEOSGeom_createLineString(sq);
                if (!g) return NULL;
                break;
 
        case POLYGONTYPE:
                lwpoly = (LWPOLY*)lwgeom;
                if (lwgeom_is_empty(lwgeom))
                        g = GEOSGeom_createEmptyPolygon();
                else
                {
                        shell = ptarray_to_GEOSLinearRing(lwpoly->rings[0], autofix);
                        if (!shell) return NULL;
                        ngeoms = lwpoly->nrings - 1;
                        if (ngeoms > 0) geoms = lwalloc(sizeof(GEOSGeom) * ngeoms);
 
                        for (i = 1; i < lwpoly->nrings; i++)
                        {
                                geoms[i - 1] = ptarray_to_GEOSLinearRing(lwpoly->rings[i], autofix);
                                if (!geoms[i - 1])
                                {
                                        uint32_t k;
                                        for (k = 0; k < i - 1; k++)
                                                GEOSGeom_destroy(geoms[k]);
                                        lwfree(geoms);
                                        GEOSGeom_destroy(shell);
                                        return NULL;
                                }
                        }
                        g = GEOSGeom_createPolygon(shell, geoms, ngeoms);
                        if (geoms) lwfree(geoms);
                }
                if (!g) return NULL;
                break;
 
        case TRIANGLETYPE:
                if (lwgeom_is_empty(lwgeom))
                        g = GEOSGeom_createEmptyPolygon();
                else
                {
                        LWTRIANGLE *lwt = (LWTRIANGLE *)lwgeom;
                        shell = ptarray_to_GEOSLinearRing(lwt->points, autofix);
                        if (!shell)
                                return NULL;
                        g = GEOSGeom_createPolygon(shell, NULL, 0);
                }
                if (!g)
                        return NULL;
                break;
        case MULTIPOINTTYPE:
        case MULTILINETYPE:
        case MULTIPOLYGONTYPE:
        case TINTYPE:
        case COLLECTIONTYPE:
                if (lwgeom->type == MULTIPOINTTYPE)
                        geostype = GEOS_MULTIPOINT;
                else if (lwgeom->type == MULTILINETYPE)
                        geostype = GEOS_MULTILINESTRING;
                else if (lwgeom->type == MULTIPOLYGONTYPE)
                        geostype = GEOS_MULTIPOLYGON;
                else
                        geostype = GEOS_GEOMETRYCOLLECTION;
 
                lwc = (LWCOLLECTION*)lwgeom;
 
                ngeoms = lwc->ngeoms;
                if (ngeoms > 0) geoms = lwalloc(sizeof(GEOSGeom) * ngeoms);
 
                j = 0;
                for (i = 0; i < ngeoms; ++i)
                {
                        GEOSGeometry* g;
 
                        if (lwgeom_is_empty(lwc->geoms[i])) continue;
 
                        g = LWGEOM2GEOS(lwc->geoms[i], 0);
                        if (!g)
                        {
                                uint32_t k;
                                for (k = 0; k < j; k++)
                                        GEOSGeom_destroy(geoms[k]);
                                lwfree(geoms);
                                return NULL;
                        }
                        geoms[j++] = g;
                }
                g = GEOSGeom_createCollection(geostype, geoms, j);
                if (ngeoms > 0) lwfree(geoms);
                if (!g) return NULL;
                break;
 
        default:
                lwerror("Unknown geometry type: %d - %s", lwgeom->type, lwtype_name(lwgeom->type));
                return NULL;
        }
 
        GEOSSetSRID(g, lwgeom->srid);
 
#if LWDEBUG_LEVEL >= 4
        wkt = GEOSGeomToWKT(g);
        LWDEBUGF(4, "LWGEOM2GEOS: GEOSGeom: %s", wkt);
        free(wkt);
#endif
 
        return g;
}
 
GEOSGeometry*
make_geos_point(double x, double y)
{
        GEOSCoordSequence* seq = GEOSCoordSeq_create(1, 2);
        GEOSGeometry* geom = NULL;
 
        if (!seq) return NULL;
 
#if POSTGIS_GEOS_VERSION < 38
        GEOSCoordSeq_setX(seq, 0, x);
        GEOSCoordSeq_setY(seq, 0, y);
#else
        GEOSCoordSeq_setXY(seq, 0, x, y);
#endif
 
        geom = GEOSGeom_createPoint(seq);
        if (!geom) GEOSCoordSeq_destroy(seq);
        return geom;
}
 
GEOSGeometry*
make_geos_segment(double x1, double y1, double x2, double y2)
{
        GEOSCoordSequence* seq = GEOSCoordSeq_create(2, 2);
        GEOSGeometry* geom = NULL;
 
        if (!seq) return NULL;
 
#if POSTGIS_GEOS_VERSION < 38
        GEOSCoordSeq_setX(seq, 0, x1);
        GEOSCoordSeq_setY(seq, 0, y1);
        GEOSCoordSeq_setX(seq, 1, x2);
        GEOSCoordSeq_setY(seq, 1, y2);
#else
        GEOSCoordSeq_setXY(seq, 0, x1, y1);
        GEOSCoordSeq_setXY(seq, 1, x2, y2);
#endif
 
        geom = GEOSGeom_createLineString(seq);
        if (!geom) GEOSCoordSeq_destroy(seq);
        return geom;
}
 
const char*
lwgeom_geos_version()
{
        const char* ver = GEOSversion();
        return ver;
}
 
/* Return the consistent SRID of all input.
 * Intended to be called from RESULT_SRID macro */
static int32_t
get_result_srid(size_t count, const char* funcname, ...)
{
        va_list ap;
        va_start(ap, funcname);
        int32_t srid = SRID_INVALID;
        size_t i;
        for(i = 0; i < count; i++)
        {
                LWGEOM* g = va_arg(ap, LWGEOM*);
                if (!g)
                {
                        lwerror("%s: Geometry is null", funcname);
                        return SRID_INVALID;
                }
                if (i == 0)
                {
                        srid = g->srid;
                }
                else
                {
                        if (g->srid != srid)
                        {
                                lwerror("%s: Operation on mixed SRID geometries (%d != %d)", funcname, srid, g->srid);
                                return SRID_INVALID;
                        }
                }
        }
        return srid;
}
 
LWGEOM*
lwgeom_normalize(const LWGEOM* geom)
{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom);
        uint8_t is3d = FLAGS_GET_Z(geom->flags);
        GEOSGeometry* g;
 
        if (srid == SRID_INVALID) return NULL;
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g = LWGEOM2GEOS(geom, AUTOFIX))) GEOS_FAIL();
 
        if (GEOSNormalize(g) == -1) GEOS_FREE_AND_FAIL(g);
        GEOSSetSRID(g, srid);
 
        if (!(result = GEOS2LWGEOM(g, is3d))) GEOS_FREE_AND_FAIL(g);
 
        GEOSGeom_destroy(g);
        return result;
}
 
LWGEOM*
lwgeom_intersection(const LWGEOM* geom1, const LWGEOM* geom2)
{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom1, geom2);
        uint8_t is3d = (FLAGS_GET_Z(geom1->flags) || FLAGS_GET_Z(geom2->flags));
        GEOSGeometry* g1;
        GEOSGeometry* g2;
        GEOSGeometry* g3;
 
        if (srid == SRID_INVALID) return NULL;
 
        /* A.Intersection(Empty) == Empty */
        if (lwgeom_is_empty(geom2)) return lwgeom_clone_deep(geom2); /* match empty type? */
 
        /* Empty.Intersection(A) == Empty */
        if (lwgeom_is_empty(geom1)) return lwgeom_clone_deep(geom1); /* match empty type? */
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom1, AUTOFIX))) GEOS_FAIL();
        if (!(g2 = LWGEOM2GEOS(geom2, AUTOFIX))) GEOS_FREE_AND_FAIL(g1);
 
        g3 = GEOSIntersection(g1, g2);
 
        if (!g3) GEOS_FREE_AND_FAIL(g1);
        GEOSSetSRID(g3, srid);
 
        if (!(result = GEOS2LWGEOM(g3, is3d))) GEOS_FREE_AND_FAIL(g1, g2, g3);
 
        GEOS_FREE(g1, g2, g3);
        return result;
}
 
LWGEOM*
lwgeom_linemerge(const LWGEOM* geom)
{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom);
        uint8_t is3d = FLAGS_GET_Z(geom->flags);
        GEOSGeometry* g1;
        GEOSGeometry* g3;
 
        if (srid == SRID_INVALID) return NULL;
 
        /* Empty.Linemerge() == Empty */
        if (lwgeom_is_empty(geom)) return lwgeom_clone_deep(geom); /* match empty type to linestring? */
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom, AUTOFIX))) GEOS_FAIL();
 
        g3 = GEOSLineMerge(g1);
 
        if (!g3) GEOS_FREE_AND_FAIL(g1);
        GEOSSetSRID(g3, srid);
 
        if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1, g3);
 
        GEOS_FREE(g1, g3);
 
        return result;
}
 
LWGEOM*
lwgeom_unaryunion(const LWGEOM* geom)
{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom);
        uint8_t is3d = FLAGS_GET_Z(geom->flags);
        GEOSGeometry* g1;
        GEOSGeometry* g3;
 
        if (srid == SRID_INVALID) return NULL;
 
        /* Empty.UnaryUnion() == Empty */
        if (lwgeom_is_empty(geom)) return lwgeom_clone_deep(geom);
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom, AUTOFIX))) GEOS_FAIL();
 
        g3 = GEOSUnaryUnion(g1);
 
        if (!g3) GEOS_FREE_AND_FAIL(g1);
        GEOSSetSRID(g3, srid);
 
        if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1, g3);
 
        GEOS_FREE(g1, g3);
 
        return result;
}
 
LWGEOM*
lwgeom_difference(const LWGEOM* geom1, const LWGEOM* geom2)
{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom1, geom2);
        uint8_t is3d = (FLAGS_GET_Z(geom1->flags) || FLAGS_GET_Z(geom2->flags));
        GEOSGeometry *g1, *g2, *g3;
 
        if (srid == SRID_INVALID) return NULL;
 
        /* A.Intersection(Empty) == Empty */
        if (lwgeom_is_empty(geom2)) return lwgeom_clone_deep(geom1); /* match empty type? */
 
        /* Empty.Intersection(A) == Empty */
        if (lwgeom_is_empty(geom1)) return lwgeom_clone_deep(geom1); /* match empty type? */
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom1, AUTOFIX))) GEOS_FAIL();
        if (!(g2 = LWGEOM2GEOS(geom2, AUTOFIX))) GEOS_FREE_AND_FAIL(g1);
 
        g3 = GEOSDifference(g1, g2);
 
        if (!g3) GEOS_FREE_AND_FAIL(g1, g2);
        GEOSSetSRID(g3, srid);
 
        if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1, g2, g3);
 
        GEOS_FREE(g1, g2, g3);
        return result;
}
 
LWGEOM*
lwgeom_symdifference(const LWGEOM* geom1, const LWGEOM* geom2)
{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom1, geom2);
        uint8_t is3d = (FLAGS_GET_Z(geom1->flags) || FLAGS_GET_Z(geom2->flags));
        GEOSGeometry *g1, *g2, *g3;
 
        if (srid == SRID_INVALID) return NULL;
 
        /* A.SymDifference(Empty) == A */
        if (lwgeom_is_empty(geom2)) return lwgeom_clone_deep(geom1);
 
        /* Empty.DymDifference(B) == B */
        if (lwgeom_is_empty(geom1)) return lwgeom_clone_deep(geom2);
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom1, AUTOFIX))) GEOS_FAIL();
        if (!(g2 = LWGEOM2GEOS(geom2, AUTOFIX))) GEOS_FREE_AND_FAIL(g1);
 
        g3 = GEOSSymDifference(g1, g2);
 
        if (!g3) GEOS_FREE_AND_FAIL(g1, g2);
        GEOSSetSRID(g3, srid);
 
        if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1, g2, g3);
 
        GEOS_FREE(g1, g2, g3);
        return result;
}
 
LWGEOM*
lwgeom_centroid(const LWGEOM* geom)
{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom);
        uint8_t is3d = FLAGS_GET_Z(geom->flags);
        GEOSGeometry *g1, *g3;
 
        if (srid == SRID_INVALID) return NULL;
 
        if (lwgeom_is_empty(geom))
        {
                LWPOINT* lwp = lwpoint_construct_empty(srid, is3d, lwgeom_has_m(geom));
                return lwpoint_as_lwgeom(lwp);
        }
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom, AUTOFIX))) GEOS_FAIL();
 
        g3 = GEOSGetCentroid(g1);
 
        if (!g3) GEOS_FREE_AND_FAIL(g1);
        GEOSSetSRID(g3, srid);
 
        if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1);
 
        GEOS_FREE(g1, g3);
 
        return result;
}
 
LWGEOM *
lwgeom_pointonsurface(const LWGEOM *geom)
{
        LWGEOM *result;
        int32_t srid = RESULT_SRID(geom);
        uint8_t is3d = FLAGS_GET_Z(geom->flags);
        GEOSGeometry *g1, *g3;
 
        if (srid == SRID_INVALID) return NULL;
 
        if (lwgeom_is_empty(geom))
        {
                LWPOINT *lwp = lwpoint_construct_empty(srid, is3d, lwgeom_has_m(geom));
                return lwpoint_as_lwgeom(lwp);
        }
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom, AUTOFIX))) GEOS_FAIL();
 
        g3 = GEOSPointOnSurface(g1);
 
        if (!g3) GEOS_FREE_AND_FAIL(g1);
        GEOSSetSRID(g3, srid);
 
        if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1, g3);
 
        GEOS_FREE(g1, g3);
 
        return result;
}
 
LWGEOM*
lwgeom_union(const LWGEOM* geom1, const LWGEOM* geom2)
{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom1, geom2);
        uint8_t is3d = (FLAGS_GET_Z(geom1->flags) || FLAGS_GET_Z(geom2->flags));
        GEOSGeometry *g1, *g2, *g3;
 
        if (srid == SRID_INVALID) return NULL;
 
        /* A.Union(empty) == A */
        if (lwgeom_is_empty(geom1)) return lwgeom_clone_deep(geom2);
 
        /* B.Union(empty) == B */
        if (lwgeom_is_empty(geom2)) return lwgeom_clone_deep(geom1);
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom1, AUTOFIX))) GEOS_FAIL();
        if (!(g2 = LWGEOM2GEOS(geom2, AUTOFIX))) GEOS_FREE_AND_FAIL(g1);
 
        g3 = GEOSUnion(g1, g2);
 
        if (!g3) GEOS_FREE_AND_FAIL(g1, g2);
        GEOSSetSRID(g3, srid);
 
        if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1, g2, g3);
 
        GEOS_FREE(g1, g2, g3);
        return result;
}
 
LWGEOM *
lwgeom_clip_by_rect(const LWGEOM *geom1, double x1, double y1, double x2, double y2)
{
        LWGEOM *result;
        GEOSGeometry *g1, *g3;
        int is3d;
 
        /* A.Intersection(Empty) == Empty */
        if ( lwgeom_is_empty(geom1) )
                return lwgeom_clone_deep(geom1);
 
        is3d = FLAGS_GET_Z(geom1->flags);
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom1, AUTOFIX)))
                GEOS_FAIL_DEBUG();
 
        if (!(g3 = GEOSClipByRect(g1, x1, y1, x2, y2)))
                GEOS_FREE_AND_FAIL_DEBUG(g1);
 
        GEOS_FREE(g1);
        result = GEOS2LWGEOM(g3, is3d);
        GEOS_FREE(g3);
 
        if (!result)
                GEOS_FAIL_DEBUG();
 
        result->srid = geom1->srid;
 
        return result;
}
 
/* ------------ BuildArea stuff ---------------------------------------------------------------------{ */
#if POSTGIS_GEOS_VERSION < 38
typedef struct Face_t
{
        const GEOSGeometry* geom;
        GEOSGeometry* env;
        double envarea;
        struct Face_t* parent; /* if this face is an hole of another one, or NULL */
} Face;
 
static Face* newFace(const GEOSGeometry* g);
static void delFace(Face* f);
static unsigned int countParens(const Face* f);
static void findFaceHoles(Face** faces, int nfaces);
 
static Face*
newFace(const GEOSGeometry* g)
{
        Face* f = lwalloc(sizeof(Face));
        f->geom = g;
        f->env = GEOSEnvelope(f->geom);
        GEOSArea(f->env, &f->envarea);
        f->parent = NULL;
        return f;
}
 
static unsigned int
countParens(const Face* f)
{
        unsigned int pcount = 0;
        while (f->parent)
        {
                ++pcount;
                f = f->parent;
        }
        return pcount;
}
 
/* Destroy the face and release memory associated with it */
static void
delFace(Face* f)
{
        GEOSGeom_destroy(f->env);
        lwfree(f);
}
 
static int
compare_by_envarea(const void* g1, const void* g2)
{
        Face* f1 = *(Face**)g1;
        Face* f2 = *(Face**)g2;
        double n1 = f1->envarea;
        double n2 = f2->envarea;
 
        if (n1 < n2) return 1;
        if (n1 > n2) return -1;
        return 0;
}
 
/* Find holes of each face */
static void
findFaceHoles(Face** faces, int nfaces)
{
        int i, j, h;
 
        /* We sort by envelope area so that we know holes are only after their shells */
        qsort(faces, nfaces, sizeof(Face*), compare_by_envarea);
        for (i = 0; i < nfaces; ++i)
        {
                Face* f = faces[i];
                int nholes = GEOSGetNumInteriorRings(f->geom);
                LWDEBUGF(2, "Scanning face %d with env area %g and %d holes", i, f->envarea, nholes);
                for (h = 0; h < nholes; ++h)
                {
                        const GEOSGeometry* hole = GEOSGetInteriorRingN(f->geom, h);
                        LWDEBUGF(2,
                                 "Looking for hole %d/%d of face %d among %d other faces",
                                 h + 1,
                                 nholes,
                                 i,
                                 nfaces - i - 1);
                        for (j = i + 1; j < nfaces; ++j)
                        {
                                const GEOSGeometry* f2er;
                                Face* f2 = faces[j];
                                if (f2->parent) continue; /* hole already assigned */
                                f2er = GEOSGetExteriorRing(f2->geom);
                                /* TODO: can be optimized as the ring would have the same vertices, possibly in
                                 * different order. Maybe comparing number of points could already be useful. */
                                if (GEOSEquals(f2er, hole))
                                {
                                        LWDEBUGF(2, "Hole %d/%d of face %d is face %d", h + 1, nholes, i, j);
                                        f2->parent = f;
                                        break;
                                }
                        }
                }
        }
}
 
static GEOSGeometry*
collectFacesWithEvenAncestors(Face** faces, int nfaces)
{
        GEOSGeometry** geoms = lwalloc(sizeof(GEOSGeometry*) * nfaces);
        GEOSGeometry* ret;
        unsigned int ngeoms = 0;
        int i;
 
        for (i = 0; i < nfaces; ++i)
        {
                Face* f = faces[i];
                if (countParens(f) % 2) continue; /* we skip odd parents geoms */
                geoms[ngeoms++] = GEOSGeom_clone(f->geom);
        }
 
        ret = GEOSGeom_createCollection(GEOS_MULTIPOLYGON, geoms, ngeoms);
        lwfree(geoms);
        return ret;
}
 
GEOSGeometry*
LWGEOM_GEOS_buildArea(const GEOSGeometry* geom_in)
{
        GEOSGeometry* tmp;
        GEOSGeometry *geos_result, *shp;
        GEOSGeometry const* vgeoms[1];
        uint32_t i, ngeoms;
        int srid = GEOSGetSRID(geom_in);
        Face** geoms;
#if POSTGIS_DEBUG_LEVEL >= 3
        LWGEOM *geos_geom;
        char *geom_ewkt;
#endif
 
        vgeoms[0] = geom_in;
        geos_result = GEOSPolygonize(vgeoms, 1);
 
        LWDEBUGF(3, "GEOSpolygonize returned @ %p", geos_result);
 
        /* Null return from GEOSpolygonize (an exception) */
        if (!geos_result) return 0;
 
                /* We should now have a collection */
#if PARANOIA_LEVEL > 0
        if (GEOSGeomTypeId(geos_result) != COLLECTIONTYPE)
        {
                GEOSGeom_destroy(geos_result);
                lwerror("%s [%d] Unexpected return from GEOSpolygonize", __FILE__, __LINE__);
                return 0;
        }
#endif
 
        ngeoms = GEOSGetNumGeometries(geos_result);
 
#if POSTGIS_DEBUG_LEVEL >= 3
        LWDEBUGF(3, "GEOSpolygonize: ngeoms in polygonize output: %d", ngeoms);
        geos_geom = GEOS2LWGEOM(geos_result, 0);
        geom_ewkt = lwgeom_to_ewkt(geos_geom);
        LWDEBUGF(3, "GEOSpolygonize: polygonized:%s", geom_ewkt);
        lwgeom_free(geos_geom);
        lwfree(geom_ewkt);
#endif
 
        /* No geometries in collection, early out */
        if (ngeoms == 0)
        {
                GEOSSetSRID(geos_result, srid);
                return geos_result;
        }
 
        /* Return first geometry if we only have one in collection, to avoid the unnecessary Geometry clone below. */
        if (ngeoms == 1)
        {
                tmp = (GEOSGeometry*)GEOSGetGeometryN(geos_result, 0);
                if (!tmp)
                {
                        GEOSGeom_destroy(geos_result);
                        return 0; /* exception */
                }
                shp = GEOSGeom_clone(tmp);
                GEOSGeom_destroy(geos_result); /* only safe after the clone above */
                GEOSSetSRID(shp, srid);
                return shp;
        }
 
        LWDEBUGF(2, "Polygonize returned %d geoms", ngeoms);
 
        /*
         * Polygonizer returns a polygon for each face in the built topology.
         *
         * This means that for any face with holes we'll have other faces representing each hole. We can imagine a
         * parent-child relationship between these faces.
         *
         * In order to maximize the number of visible rings in output we only use those faces which have an even number
         * of parents.
         *
         * Example:
         *
         *   +---------------+
         *   |     L0        |  L0 has no parents
         *   |  +---------+  |
         *   |  |   L1    |  |  L1 is an hole of L0
         *   |  |  +---+  |  |
         *   |  |  |L2 |  |  |  L2 is an hole of L1 (which is an hole of L0)
         *   |  |  |   |  |  |
         *   |  |  +---+  |  |
         *   |  +---------+  |
         *   |               |
         *   +---------------+
         *
         * See http://trac.osgeo.org/postgis/ticket/1806
         *
         */
 
        /* Prepare face structures for later analysis */
        geoms = lwalloc(sizeof(Face**) * ngeoms);
        for (i = 0; i < ngeoms; ++i)
                geoms[i] = newFace(GEOSGetGeometryN(geos_result, i));
 
        /* Find faces representing other faces holes */
        findFaceHoles(geoms, ngeoms);
 
        /* Build a MultiPolygon composed only by faces with an even number of ancestors */
        tmp = collectFacesWithEvenAncestors(geoms, ngeoms);
 
        /* Cleanup face structures */
        for (i = 0; i < ngeoms; ++i)
                delFace(geoms[i]);
        lwfree(geoms);
 
        /* Faces referenced memory owned by geos_result. It is safe to destroy geos_result after deleting them. */
        GEOSGeom_destroy(geos_result);
 
        /* Run a single overlay operation to dissolve shared edges */
        shp = GEOSUnionCascaded(tmp);
        if (!shp)
        {
                GEOSGeom_destroy(tmp);
                return 0; /* exception */
        }
 
        GEOSGeom_destroy(tmp);
 
        GEOSSetSRID(shp, srid);
 
        return shp;
}
#endif
 
LWGEOM*
lwgeom_buildarea(const LWGEOM* geom)
{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom);
        uint8_t is3d = FLAGS_GET_Z(geom->flags);
        GEOSGeometry *g1, *g3;
 
        if (srid == SRID_INVALID) return NULL;
 
        /* Can't build an area from an empty! */
        if (lwgeom_is_empty(geom)) return (LWGEOM*)lwpoly_construct_empty(srid, is3d, 0);
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom, AUTOFIX))) GEOS_FAIL();
 
#if POSTGIS_GEOS_VERSION < 38
        g3 = LWGEOM_GEOS_buildArea(g1);
#else
        g3 = GEOSBuildArea(g1);
#endif
 
        if (!g3) GEOS_FREE_AND_FAIL(g1);
        GEOSSetSRID(g3, srid);
 
        /* If no geometries are in result collection, return NULL */
        if (GEOSGetNumGeometries(g3) == 0)
        {
                GEOS_FREE(g1);
                return NULL;
        }
 
        if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1, g3);
 
        GEOS_FREE(g1, g3);
 
        return result;
}
 
/* ------------ end of BuildArea stuff ---------------------------------------------------------------------} */
 
int
lwgeom_is_simple(const LWGEOM* geom)
{
        GEOSGeometry* g;
        int simple;
 
        /* Empty is always simple */
        if (lwgeom_is_empty(geom)) return LW_TRUE;
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g = LWGEOM2GEOS(geom, AUTOFIX))) return -1;
 
        simple = GEOSisSimple(g);
        GEOSGeom_destroy(g);
 
        if (simple == 2) /* exception thrown */
        {
                lwerror("lwgeom_is_simple: %s", lwgeom_geos_errmsg);
                return -1;
        }
 
        return simple ? LW_TRUE : LW_FALSE;
}
 
LWGEOM*
lwgeom_geos_noop(const LWGEOM* geom)
{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom);
        uint8_t is3d = FLAGS_GET_Z(geom->flags);
        GEOSGeometry* g;
 
        if (srid == SRID_INVALID) return NULL;
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g = LWGEOM2GEOS(geom, AUTOFIX))) GEOS_FAIL();
 
        if (!g) GEOS_FREE_AND_FAIL(g);
        GEOSSetSRID(g, srid);
 
        if (!(result = GEOS2LWGEOM(g, is3d)))
                GEOS_FREE_AND_FAIL(g);
 
        GEOS_FREE(g);
 
        return result;
}
 
LWGEOM*
lwgeom_snap(const LWGEOM* geom1, const LWGEOM* geom2, double tolerance)
{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom1, geom2);
        uint8_t is3d = (FLAGS_GET_Z(geom1->flags) || FLAGS_GET_Z(geom2->flags));
        GEOSGeometry *g1, *g2, *g3;
 
        if (srid == SRID_INVALID) return NULL;
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom1, AUTOFIX))) GEOS_FAIL();
        if (!(g2 = LWGEOM2GEOS(geom2, AUTOFIX))) GEOS_FREE_AND_FAIL(g1);
 
        g3 = GEOSSnap(g1, g2, tolerance);
 
        if (!g3) GEOS_FREE_AND_FAIL(g1, g2);
        GEOSSetSRID(g3, srid);
 
        if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1, g2, g3);
 
        GEOS_FREE(g1, g2, g3);
        return result;
}
 
LWGEOM*
lwgeom_sharedpaths(const LWGEOM* geom1, const LWGEOM* geom2)
{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom1, geom2);
        uint8_t is3d = (FLAGS_GET_Z(geom1->flags) || FLAGS_GET_Z(geom2->flags));
        GEOSGeometry *g1, *g2, *g3;
 
        if (srid == SRID_INVALID) return NULL;
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom1, AUTOFIX))) GEOS_FAIL();
        if (!(g2 = LWGEOM2GEOS(geom2, AUTOFIX))) GEOS_FREE_AND_FAIL(g1);
 
        g3 = GEOSSharedPaths(g1, g2);
 
        if (!g3) GEOS_FREE_AND_FAIL(g1, g2);
        GEOSSetSRID(g3, srid);
 
        if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1, g2, g3);
 
        GEOS_FREE(g1, g2, g3);
        return result;
}
 
static LWGEOM *
lwline_offsetcurve(const LWLINE *lwline, double size, int quadsegs, int joinStyle, double mitreLimit)
{
        LWGEOM* result;
        LWGEOM* geom = lwline_as_lwgeom(lwline);
        int32_t srid = RESULT_SRID(geom);
        uint8_t is3d = FLAGS_GET_Z(geom->flags);
        GEOSGeometry *g1, *g3;
 
        if (srid == SRID_INVALID) return NULL;
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom, AUTOFIX))) GEOS_FAIL();
 
        g3 = GEOSOffsetCurve(g1, size, quadsegs, joinStyle, mitreLimit);
 
        if (!g3)
        {
                GEOS_FREE(g1);
                return NULL;
        }
 
        GEOSSetSRID(g3, srid);
 
        if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1, g3);
 
        GEOS_FREE(g1, g3);
        return result;
}
 
static LWGEOM *
lwcollection_offsetcurve(const LWCOLLECTION *col, double size, int quadsegs, int joinStyle, double mitreLimit)
{
        const LWGEOM *geom = lwcollection_as_lwgeom(col);
        int32_t srid = RESULT_SRID(geom);
        uint8_t is3d = FLAGS_GET_Z(col->flags);
        LWCOLLECTION *result;
        LWGEOM *tmp;
        uint32_t i;
        if (srid == SRID_INVALID) return NULL;
 
        result = lwcollection_construct_empty(MULTILINETYPE, srid, is3d, LW_FALSE);
 
        for (i = 0; i < col->ngeoms; i++)
        {
                tmp = lwgeom_offsetcurve(col->geoms[i], size, quadsegs, joinStyle, mitreLimit);
 
                if (!tmp)
                {
                        lwcollection_free(result);
                        return NULL;
                }
 
                if (!lwgeom_is_empty(tmp))
                {
                        if (lwgeom_is_collection(tmp))
                                result = lwcollection_concat_in_place(result, lwgeom_as_lwcollection(tmp));
                        else
                                result = lwcollection_add_lwgeom(result, tmp);
 
                        if (!result)
                        {
                                lwgeom_free(tmp);
                                return NULL;
                        }
                }
        }
 
        if (result->ngeoms == 1)
        {
                tmp = result->geoms[0];
                lwcollection_release(result);
                return tmp;
        }
        else
                return lwcollection_as_lwgeom(result);
}
 
LWGEOM*
lwgeom_offsetcurve(const LWGEOM* geom, double size, int quadsegs, int joinStyle, double mitreLimit)
{
        int32_t srid = RESULT_SRID(geom);
        LWGEOM *result = NULL;
        LWGEOM *noded = NULL;
        if (srid == SRID_INVALID) return NULL;
 
        if (lwgeom_dimension(geom) != 1)
        {
                lwerror("%s: input is not linear", __func__, lwtype_name(geom->type));
                return NULL;
        }
 
        while (!result)
        {
                switch (geom->type)
                {
                case LINETYPE:
                        result = lwline_offsetcurve(lwgeom_as_lwline(geom), size, quadsegs, joinStyle, mitreLimit);
                        break;
                case COLLECTIONTYPE:
                case MULTILINETYPE:
                        result = lwcollection_offsetcurve(lwgeom_as_lwcollection(geom), size, quadsegs, joinStyle, mitreLimit);
                        break;
                default:
                        lwerror("%s: unsupported geometry type: %s", __func__, lwtype_name(geom->type));
                        return NULL;
                }
 
                if (result)
                {
                        if (noded) lwgeom_free(noded);
                        return result;
                }
                else if (!noded)
                {
                        noded = lwgeom_node(geom);
                        if (!noded)
                        {
                                lwerror("lwgeom_offsetcurve: cannot node input");
                                return NULL;
                        }
                        geom = noded;
                }
                else
                {
                        lwgeom_free(noded);
                        lwerror("lwgeom_offsetcurve: noded geometry cannot be offset");
                        return NULL;
                }
        }
 
        return result;
}
 
LWMPOINT*
lwpoly_to_points(const LWPOLY* lwpoly, uint32_t npoints, int32_t seed)
{
        double area, bbox_area, bbox_width, bbox_height;
        GBOX bbox;
        const LWGEOM* lwgeom = (LWGEOM*)lwpoly;
        uint32_t sample_npoints, sample_sqrt, sample_width, sample_height;
        double sample_cell_size;
        uint32_t i, j, n;
        uint32_t iterations = 0;
        uint32_t npoints_generated = 0;
        uint32_t npoints_tested = 0;
        GEOSGeometry* g;
        const GEOSPreparedGeometry* gprep;
        GEOSGeometry* gpt;
        GEOSCoordSequence* gseq;
        LWMPOINT* mpt;
        int32_t srid = lwgeom_get_srid(lwgeom);
        int done = 0;
        int* cells;
        const size_t size = 2 * sizeof(int);
        char tmp[2 * sizeof(int)];
        const size_t stride = 2 * sizeof(int);
 
        if (lwgeom_get_type(lwgeom) != POLYGONTYPE)
        {
                lwerror("%s: only polygons supported", __func__);
                return NULL;
        }
 
        if (npoints == 0 || lwgeom_is_empty(lwgeom)) return NULL;
 
        if (!lwpoly->bbox)
                lwgeom_calculate_gbox(lwgeom, &bbox);
        else
                bbox = *(lwpoly->bbox);
 
        area = lwpoly_area(lwpoly);
        bbox_width = bbox.xmax - bbox.xmin;
        bbox_height = bbox.ymax - bbox.ymin;
        bbox_area = bbox_width * bbox_height;
 
        if (area == 0.0 || bbox_area == 0.0)
        {
                lwerror("%s: zero area input polygon, TBD", __func__);
                return NULL;
        }
 
        /* Gross up our test set a bit to increase odds of getting coverage in one pass */
        sample_npoints = npoints * bbox_area / area;
 
        /* We're going to generate points using a sample grid as described
         * http://lin-ear-th-inking.blogspot.ca/2010/05/more-random-points-in-jts.html to try and get a more uniform
         * "random" set of points. So we have to figure out how to stick a grid into our box */
        sample_sqrt = lround(sqrt(sample_npoints));
        if (sample_sqrt == 0)
                sample_sqrt = 1;
 
        /* Calculate the grids we're going to randomize within */
        if (bbox_width > bbox_height)
        {
                sample_width = sample_sqrt;
                sample_height = ceil((double)sample_npoints / (double)sample_width);
                sample_cell_size = bbox_width / sample_width;
        }
        else
        {
                sample_height = sample_sqrt;
                sample_width = ceil((double)sample_npoints / (double)sample_height);
                sample_cell_size = bbox_height / sample_height;
        }
 
        /* Prepare the polygon for fast true/false testing */
        initGEOS(lwnotice, lwgeom_geos_error);
        g = (GEOSGeometry*)LWGEOM2GEOS(lwgeom, 0);
        if (!g)
        {
                lwerror("%s: Geometry could not be converted to GEOS: %s", __func__, lwgeom_geos_errmsg);
                return NULL;
        }
        gprep = GEOSPrepare(g);
 
        /* Get an empty multi-point ready to return */
        mpt = lwmpoint_construct_empty(srid, 0, 0);
 
        /* Initiate random number generator.
         * Repeatable numbers are generated with seed values >= 1.
         * When seed is zero and has not previously been set, it is based on
         * Unix time (seconds) and process ID. */
        lwrandom_set_seed(seed);
 
        /* Now we fill in an array of cells, and then shuffle that array, */
        /* so we can visit the cells in random order to avoid visual ugliness */
        /* caused by visiting them sequentially */
        cells = lwalloc(2 * sizeof(int) * sample_height * sample_width);
        for (i = 0; i < sample_width; i++)
        {
                for (j = 0; j < sample_height; j++)
                {
                        cells[2 * (i * sample_height + j)] = i;
                        cells[2 * (i * sample_height + j) + 1] = j;
                }
        }
 
        /* Fisher-Yates shuffle */
        n = sample_height * sample_width;
        if (n > 1)
        {
                for (i = n - 1; i > 0; i--)
                {
                        size_t j = (size_t)(lwrandom_uniform() * (i + 1));
 
                        memcpy(tmp, (char *)cells + j * stride, size);
                        memcpy((char *)cells + j * stride, (char *)cells + i * stride, size);
                        memcpy((char *)cells + i * stride, tmp, size);
                }
        }
 
        /* Start testing points */
        while (npoints_generated < npoints)
        {
                iterations++;
                for (i = 0; i < sample_width * sample_height; i++)
                {
                        int contains = 0;
                        double y = bbox.ymin + cells[2 * i] * sample_cell_size;
                        double x = bbox.xmin + cells[2 * i + 1] * sample_cell_size;
                        x += lwrandom_uniform() * sample_cell_size;
                        y += lwrandom_uniform() * sample_cell_size;
                        if (x >= bbox.xmax || y >= bbox.ymax) continue;
 
                        gseq = GEOSCoordSeq_create(1, 2);
#if POSTGIS_GEOS_VERSION < 38
                        GEOSCoordSeq_setX(gseq, 0, x);
                        GEOSCoordSeq_setY(gseq, 0, y);
#else
                        GEOSCoordSeq_setXY(gseq, 0, x, y);
#endif
                        gpt = GEOSGeom_createPoint(gseq);
 
                        contains = GEOSPreparedIntersects(gprep, gpt);
 
                        GEOSGeom_destroy(gpt);
 
                        if (contains == 2)
                        {
                                GEOSPreparedGeom_destroy(gprep);
                                GEOSGeom_destroy(g);
                                lwerror("%s: GEOS exception on PreparedContains: %s", __func__, lwgeom_geos_errmsg);
                                return NULL;
                        }
                        if (contains)
                        {
                                npoints_generated++;
                                mpt = lwmpoint_add_lwpoint(mpt, lwpoint_make2d(srid, x, y));
                                if (npoints_generated == npoints)
                                {
                                        done = 1;
                                        break;
                                }
                        }
 
                        /* Short-circuit check for ctrl-c occasionally */
                        npoints_tested++;
                        if (npoints_tested % 10000 == 0)
                                LW_ON_INTERRUPT(GEOSPreparedGeom_destroy(gprep); GEOSGeom_destroy(g); return NULL);
 
                        if (done) break;
                }
                if (done || iterations > 100) break;
        }
 
        GEOSPreparedGeom_destroy(gprep);
        GEOSGeom_destroy(g);
        lwfree(cells);
 
        return mpt;
}
 
/* Allocate points to sub-geometries by area, then call lwgeom_poly_to_points and bundle up final result in a single
 * multipoint. */
LWMPOINT*
lwmpoly_to_points(const LWMPOLY* lwmpoly, uint32_t npoints, int32_t seed)
{
        const LWGEOM* lwgeom = (LWGEOM*)lwmpoly;
        double area;
        uint32_t i;
        LWMPOINT* mpt = NULL;
 
        if (lwgeom_get_type(lwgeom) != MULTIPOLYGONTYPE)
        {
                lwerror("%s: only multipolygons supported", __func__);
                return NULL;
        }
        if (npoints == 0 || lwgeom_is_empty(lwgeom)) return NULL;
 
        area = lwgeom_area(lwgeom);
 
        for (i = 0; i < lwmpoly->ngeoms; i++)
        {
                double sub_area = lwpoly_area(lwmpoly->geoms[i]);
                int sub_npoints = lround(npoints * sub_area / area);
                if (sub_npoints > 0)
                {
                        LWMPOINT* sub_mpt = lwpoly_to_points(lwmpoly->geoms[i], sub_npoints, seed);
                        if (!mpt)
                                mpt = sub_mpt;
                        else
                        {
                                uint32_t j;
                                for (j = 0; j < sub_mpt->ngeoms; j++)
                                        mpt = lwmpoint_add_lwpoint(mpt, sub_mpt->geoms[j]);
                                /* Just free the shell, leave the underlying lwpoints alone, as they are now owned by
                                 * the returning multipoint */
                                lwfree(sub_mpt->geoms);
                                lwgeom_release((LWGEOM*)sub_mpt);
                        }
                }
        }
        return mpt;
}
 
LWMPOINT*
lwgeom_to_points(const LWGEOM* lwgeom, uint32_t npoints, int32_t seed)
{
        switch (lwgeom_get_type(lwgeom))
        {
        case MULTIPOLYGONTYPE:
                return lwmpoly_to_points((LWMPOLY*)lwgeom, npoints, seed);
        case POLYGONTYPE:
                return lwpoly_to_points((LWPOLY*)lwgeom, npoints, seed);
        default:
                lwerror("%s: unsupported geometry type '%s'", __func__, lwtype_name(lwgeom_get_type(lwgeom)));
                return NULL;
        }
}
 
LWTIN*
lwtin_from_geos(const GEOSGeometry* geom, uint8_t want3d)
{
        int type = GEOSGeomTypeId(geom);
        int SRID = GEOSGetSRID(geom);
 
        /* GEOS's 0 is equivalent to our unknown as for SRID values */
        if (SRID == 0) SRID = SRID_UNKNOWN;
 
        if (want3d && !GEOSHasZ(geom))
        {
                LWDEBUG(3, "Geometry has no Z, won't provide one");
                want3d = 0;
        }
 
        switch (type)
        {
                LWTRIANGLE** geoms;
                uint32_t i, ngeoms;
        case GEOS_GEOMETRYCOLLECTION:
                LWDEBUG(4, "lwgeom_from_geometry: it's a Collection or Multi");
 
                ngeoms = GEOSGetNumGeometries(geom);
                geoms = NULL;
                if (ngeoms)
                {
                        geoms = lwalloc(ngeoms * sizeof *geoms);
                        if (!geoms)
                        {
                                lwerror("lwtin_from_geos: can't allocate geoms");
                                return NULL;
                        }
                        for (i = 0; i < ngeoms; i++)
                        {
                                const GEOSGeometry *poly, *ring;
                                const GEOSCoordSequence* cs;
                                POINTARRAY* pa;
 
                                poly = GEOSGetGeometryN(geom, i);
                                ring = GEOSGetExteriorRing(poly);
                                cs = GEOSGeom_getCoordSeq(ring);
                                pa = ptarray_from_GEOSCoordSeq(cs, want3d);
 
                                geoms[i] = lwtriangle_construct(SRID, NULL, pa);
                        }
                }
                return (LWTIN*)lwcollection_construct(TINTYPE, SRID, NULL, ngeoms, (LWGEOM**)geoms);
        case GEOS_POLYGON:
        case GEOS_MULTIPOINT:
        case GEOS_MULTILINESTRING:
        case GEOS_MULTIPOLYGON:
        case GEOS_LINESTRING:
        case GEOS_LINEARRING:
        case GEOS_POINT:
                lwerror("lwtin_from_geos: invalid geometry type for tin: %d", type);
                break;
 
        default:
                lwerror("GEOS2LWGEOM: unknown geometry type: %d", type);
                return NULL;
        }
 
        /* shouldn't get here */
        return NULL;
}
/*
 * output = 1 for edges, 2 for TIN, 0 for polygons
 */
LWGEOM*
lwgeom_delaunay_triangulation(const LWGEOM* geom, double tolerance, int32_t output)
{
        LWGEOM* result;
        int32_t srid = RESULT_SRID(geom);
        uint8_t is3d = FLAGS_GET_Z(geom->flags);
        GEOSGeometry *g1, *g3;
 
        if (output < 0 || output > 2)
        {
                lwerror("%s: invalid output type specified %d", __func__, output);
                return NULL;
        }
 
        if (srid == SRID_INVALID) return NULL;
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        if (!(g1 = LWGEOM2GEOS(geom, AUTOFIX))) GEOS_FAIL();
 
        /* if output != 1 we want polys */
        g3 = GEOSDelaunayTriangulation(g1, tolerance, output == 1);
 
        if (!g3) GEOS_FREE_AND_FAIL(g1);
        GEOSSetSRID(g3, srid);
 
        if (output == 2)
        {
                result = (LWGEOM*)lwtin_from_geos(g3, is3d);
                if (!result)
                {
                        GEOS_FREE(g1, g3);
                        lwerror("%s: cannot convert output geometry", __func__);
                        return NULL;
                }
                lwgeom_set_srid(result, srid);
        }
        else if (!(result = GEOS2LWGEOM(g3, is3d)))
                GEOS_FREE_AND_FAIL(g1, g3);
 
        GEOS_FREE(g1, g3);
        return result;
}
 
static GEOSCoordSequence*
lwgeom_get_geos_coordseq_2d(const LWGEOM* g, uint32_t num_points)
{
        uint32_t i = 0;
        uint8_t num_dims = 2;
        LWPOINTITERATOR* it;
        GEOSCoordSequence* coords;
        POINT4D tmp;
 
        coords = GEOSCoordSeq_create(num_points, num_dims);
        if (!coords) return NULL;
 
        it = lwpointiterator_create(g);
        while (lwpointiterator_next(it, &tmp))
        {
                if (i >= num_points)
                {
                        lwerror("Incorrect num_points provided to lwgeom_get_geos_coordseq_2d");
                        GEOSCoordSeq_destroy(coords);
                        lwpointiterator_destroy(it);
                        return NULL;
                }
 
#if POSTGIS_GEOS_VERSION < 38
                if (!GEOSCoordSeq_setX(coords, i, tmp.x) || !GEOSCoordSeq_setY(coords, i, tmp.y))
#else
                if (!GEOSCoordSeq_setXY(coords, i, tmp.x, tmp.y))
#endif
                {
                        GEOSCoordSeq_destroy(coords);
                        lwpointiterator_destroy(it);
                        return NULL;
                }
                i++;
        }
        lwpointiterator_destroy(it);
 
        return coords;
}
 
LWGEOM*
lwgeom_voronoi_diagram(const LWGEOM* g, const GBOX* env, double tolerance, int output_edges)
{
        uint32_t num_points = lwgeom_count_vertices(g);
        LWGEOM* lwgeom_result;
        char is_3d = LW_FALSE;
        int32_t srid = lwgeom_get_srid(g);
        GEOSCoordSequence* coords;
        GEOSGeometry* geos_geom;
        GEOSGeometry* geos_env = NULL;
        GEOSGeometry* geos_result;
 
        if (num_points < 2)
        {
                LWCOLLECTION* empty = lwcollection_construct_empty(COLLECTIONTYPE, lwgeom_get_srid(g), 0, 0);
                return lwcollection_as_lwgeom(empty);
        }
 
        initGEOS(lwnotice, lwgeom_geos_error);
 
        /* Instead of using the standard LWGEOM2GEOS transformer, we read the vertices of the LWGEOM directly and put
         * them into a single GEOS CoordinateSeq that can be used to define a LineString.  This allows us to process
         * geometry types that may not be supported by GEOS, and reduces the memory requirements in cases of many
         * geometries with few points (such as LWMPOINT).*/
        coords = lwgeom_get_geos_coordseq_2d(g, num_points);
        if (!coords) return NULL;
 
        geos_geom = GEOSGeom_createLineString(coords);
        if (!geos_geom)
        {
                GEOSCoordSeq_destroy(coords);
                return NULL;
        }
 
        if (env) geos_env = GBOX2GEOS(env);
 
        geos_result = GEOSVoronoiDiagram(geos_geom, geos_env, tolerance, output_edges);
 
        GEOSGeom_destroy(geos_geom);
        if (env) GEOSGeom_destroy(geos_env);
 
        if (!geos_result)
        {
                lwerror("GEOSVoronoiDiagram: %s", lwgeom_geos_errmsg);
                return NULL;
        }
 
        lwgeom_result = GEOS2LWGEOM(geos_result, is_3d);
        GEOSGeom_destroy(geos_result);
 
        lwgeom_set_srid(lwgeom_result, srid);
 
        return lwgeom_result;
}