root/spike/nicklas/distcalc/liblwgeom/measures.c

/**********************************************************************
 * $Id$
 *
 * PostGIS - Spatial Types for PostgreSQL
 * http://postgis.refractions.net
 * Copyright 2001-2006 Refractions Research Inc.
 *
 * This is free software; you can redistribute and/or modify it under
 * the terms of the GNU General Public Licence. See the COPYING file.
 *
 **********************************************************************/

#include <math.h>
#include <string.h>
#include <stdlib.h>

#include "measures.h"


/*------------------------------------------------------------------------------------------------------------
Initializing functions
The functions starting the distance-calculation processses
--------------------------------------------------------------------------------------------------------------*/

/**
Function initializing shortestline and longestline calculations.
*/
LWGEOM *
lw_dist2d_distanceline(uchar *lw1, uchar *lw2,int srid,int mode)
{
        LWDEBUG(2, "lw_dist2d_distanceline is called");
        double x1,x2,y1,y2;
        LWPOINT *point1, *point2;
        double initdistance = ( mode == DIST2D_MIN ? MAXFLOAT : -1.0);
        DISTPTS thedl;
        thedl.mode = mode;
        thedl.distance = initdistance;
        thedl.tolerance = 0.0;

        LWPOINT *lwpoints[2];
        LWGEOM *result;

        if (!lw_dist2d_comp( lw1,lw2,&thedl))
        {
        /*should never get here. all cases ought to be error handled earlier*/
                lwerror("Some unspecified error.");
                result =(LWGEOM *)lwcollection_construct_empty(srid, 0, 0);
        }

        /*if thedl.distance is unchanged there where only empty geometries input*/
        if (thedl.distance == initdistance)
        {
                LWDEBUG(3, "didn't find geometries to measure between, returning null");
                result =(LWGEOM *)lwcollection_construct_empty(srid, 0, 0);
        }
        else
        {
                x1=thedl.p1.x;
                y1=thedl.p1.y;
                x2=thedl.p2.x;
                y2=thedl.p2.y;

                point1 = make_lwpoint2d(srid, x1, y1);
                point2 = make_lwpoint2d(srid, x2, y2);

                lwpoints[0] = make_lwpoint2d(srid, x1, y1);
                lwpoints[1] = make_lwpoint2d(srid, x2, y2);

                result = (LWGEOM *)lwline_from_lwpointarray(srid, 2, lwpoints);
        }
        return result;
}

/**
Function initializing closestpoint calculations.
*/
LWGEOM *
lw_dist2d_distancepoint(uchar *lw1, uchar *lw2,int srid,int mode)
{
        LWDEBUG(2, "lw_dist2d_distancepoint is called");
        double x,y;
        DISTPTS thedl;
        double initdistance = MAXFLOAT;

        thedl.mode = mode;
        thedl.distance= initdistance;
        thedl.tolerance = 0;

        LWGEOM *result;

        if (!lw_dist2d_comp( lw1,lw2,&thedl))
        {
        /*should never get here. all cases ought to be error handled earlier*/
        lwerror("Some unspecified error.");
        result =(LWGEOM *)lwcollection_construct_empty(srid, 0, 0);
        }
        if (thedl.distance == initdistance)
        {
                LWDEBUG(3, "didn't find geometries to measure between, returning null");
                result =(LWGEOM *)lwcollection_construct_empty(srid, 0, 0);
        }
        else
        {
                x=thedl.p1.x;
                y=thedl.p1.y;
                result = (LWGEOM *)make_lwpoint2d(srid, x, y);
        }
        return result;
}


/**
Function initialazing max distance calculation
*/
double
lwgeom_maxdistance2d(uchar *lw1, uchar *lw2)
{
        LWDEBUG(2, "lwgeom_maxdistance2d is called");

        return lwgeom_maxdistance2d_tolerance( lw1, lw2, 0.0 );
}

/**
Function handling max distance calculations and dfyllywithin calculations.
The difference is just the tolerance.
*/
double
lwgeom_maxdistance2d_tolerance(uchar *lw1, uchar *lw2, double tolerance)
{
        LWDEBUG(2, "lwgeom_maxdistance2d_tolerance is called");
        /*double thedist;*/
        DISTPTS thedl;
        thedl.mode = DIST2D_MAX;
        thedl.distance= -1;
        thedl.tolerance = tolerance;
        if (lw_dist2d_comp( lw1,lw2,&thedl))
        {
                return thedl.distance;
        }
        /*should never get here. all cases ought to be error handled earlier*/
        lwerror("Some unspecified error.");
        return -1;
}

/**
        Function initialazing min distance calculation
*/
double
lwgeom_mindistance2d(uchar *lw1, uchar *lw2)
{
        LWDEBUG(2, "lwgeom_mindistance2d is called");
        return lwgeom_mindistance2d_tolerance( lw1, lw2, 0.0 );
}

/**
        Function handling min distance calculations and dwithin calculations.
        The difference is just the tolerance.
*/
double
lwgeom_mindistance2d_tolerance(uchar *lw1, uchar *lw2, double tolerance)
{
        LWDEBUG(2, "lwgeom_mindistance2d_tolerance is called");
        DISTPTS thedl;
        thedl.mode = DIST2D_MIN;
        thedl.distance= MAXFLOAT;
        thedl.tolerance = tolerance;
        if (lw_dist2d_comp( lw1,lw2,&thedl))
        {
                return thedl.distance;
        }
        /*should never get here. all cases ought to be error handled earlier*/
        lwerror("Some unspecified error.");
        return MAXFLOAT;
}


/*------------------------------------------------------------------------------------------------------------
End of Initializing functions
--------------------------------------------------------------------------------------------------------------*/

/*------------------------------------------------------------------------------------------------------------
Preprocessing functions
Functions preparing geometries for distance-calculations
--------------------------------------------------------------------------------------------------------------*/

/**
        This function just deserializes geometries
        Bboxes is not checked here since it is the subgeometries
        bboxes we will use anyway.
*/
int
lw_dist2d_comp(uchar *lw1, uchar *lw2, DISTPTS *dl)
{
        LWDEBUG(2, "lw_dist2d_comp is called");

        LWGEOM *lwg1 = lwgeom_deserialize(lw1);
        LWGEOM *lwg2 = lwgeom_deserialize(lw2);

        return lw_dist2d_recursive      ((LWCOLLECTION*) lwg1,(LWCOLLECTION*) lwg2, dl);
}

/**
This is a recursive function delivering every possible combinatin of subgeometries
*/
int lw_dist2d_recursive(const LWCOLLECTION * lwg1,const LWCOLLECTION * lwg2,DISTPTS *dl)
{
        LWDEBUGF(2, "lw_dist2d_comp is called with type1=%d, type2=%d", TYPE_GETTYPE(lwg1->type), TYPE_GETTYPE(lwg2->type));
        /*If empty gemetry, return. True here only means continue searching. False would have stoped the process
        if (lwgeom_is_empty(lwg1)||lwgeom_is_empty(lwg2)) return LW_TRUE;               moved down*/

        int i, j;
        int n1=1;
        int n2=1;;
        LWGEOM *g1, *g2;

        if (lwgeom_is_collection(TYPE_GETTYPE(lwg1->type)))
        {
                LWDEBUG(3, "First geometry is collection");
                n1=lwg1->ngeoms;
        }
        if (lwgeom_is_collection(TYPE_GETTYPE(lwg2->type)))
        {
                LWDEBUG(3, "Second geometry is collection");
                n2=lwg2->ngeoms;
        }

        for ( i = 0; i < n1; i++ )
        {

                if (lwgeom_is_collection(TYPE_GETTYPE(lwg1->type)))
                {
                        g1=lwg1->geoms[i];
                }
                else
                {
                        g1=(LWGEOM*)lwg1;
                }

                if (lwgeom_is_empty(g1)) return LW_TRUE;

                if (lwgeom_is_collection(TYPE_GETTYPE(g1->type)))
                {
                        LWDEBUG(3, "Found collection inside first geometry collection, recursing");
                        if (!lw_dist2d_recursive((LWCOLLECTION*)g1, (LWCOLLECTION*)lwg2, dl)) return LW_FALSE;
                        continue;
                }
                for ( j = 0; j < n2; j++ )
                {
                        if (lwgeom_is_collection(TYPE_GETTYPE(lwg2->type)))
                        {
                                g2=lwg2->geoms[j];
                        }
                        else
                        {
                                g2=(LWGEOM*)lwg2;
                        }
                        if (lwgeom_is_collection(TYPE_GETTYPE(g2->type)))
                        {
                                LWDEBUG(3, "Found collection inside second geometry collection, recursing");
                                if (!lw_dist2d_recursive((LWCOLLECTION*) g1, (LWCOLLECTION*)g2, dl)) return LW_FALSE;
                                continue;
                        }

                        if ( ! g1->bbox )
                        {
                                g1->bbox = lwgeom_compute_box2d(g1);
                        }
                        if ( ! g2->bbox )
                        {
                                g2->bbox = lwgeom_compute_box2d(g2);
                        }
                        /*If one of geometries is empty, return. True here only means continue searching. False would have stoped the process*/
                        if (lwgeom_is_empty(g1)||lwgeom_is_empty(g2)) return LW_TRUE;

                        if ((dl->mode==DIST2D_MAX)||(TYPE_GETTYPE(g1->type)==POINTTYPE) ||(TYPE_GETTYPE(g2->type)==POINTTYPE)||lw_dist2d_check_overlap(g1, g2))
                        {
                                if (!lw_dist2d_distribute_bruteforce(g1, g2, dl)) return LW_FALSE;
                                if (dl->distance<=dl->tolerance && dl->mode == DIST2D_MIN) return LW_TRUE; /*just a check if  the answer is already given*/
                        }
                        else
                        {
                                if (!lw_dist2d_distribute_fast(g1, g2, dl)) return LW_FALSE;
                        }
                }
        }
        return LW_TRUE;
}



/**

This function distributes the "old-type" brut-force tasks depending on type
*/
int
lw_dist2d_distribute_bruteforce(LWGEOM *lwg1, LWGEOM *lwg2, DISTPTS *dl)
{
        LWDEBUGF(2, "lw_dist2d_distribute_bruteforce is called with typ1=%d, type2=%d", TYPE_GETTYPE(lwg1->type), TYPE_GETTYPE(lwg2->type));

        int     t1 = TYPE_GETTYPE(lwg1->type);
        int     t2 = TYPE_GETTYPE(lwg2->type);


        if  ( t1 == POINTTYPE )
        {
                if  ( t2 == POINTTYPE )
                {
                        dl->twisted=1;
                        return lw_dist2d_point_point((LWPOINT *)lwg1, (LWPOINT *)lwg2, dl);
                }
                else if  ( t2 == LINETYPE )
                {
                        dl->twisted=1;
                        return lw_dist2d_point_line((LWPOINT *)lwg1, (LWLINE *)lwg2, dl);
                }
                else if  ( t2 == POLYGONTYPE )
                {
                        dl->twisted=1;
                        return lw_dist2d_point_poly((LWPOINT *)lwg1, (LWPOLY *)lwg2,dl);
                }
                else
                {
                        lwerror("Unsupported geometry type: %s", lwgeom_typename(t2));
                        return LW_FALSE;
                }
        }
        else if ( t1 == LINETYPE )
        {
                if ( t2 == POINTTYPE )
                {
                        dl->twisted=(-1);
                        return lw_dist2d_point_line((LWPOINT *)lwg2,(LWLINE *)lwg1,dl);
                }
                else if ( t2 == LINETYPE )
                {
                        dl->twisted=1;
                        /*lwnotice("start line");*/
                        return lw_dist2d_line_line((LWLINE *)lwg1,(LWLINE *)lwg2,dl);
                }
                else if ( t2 == POLYGONTYPE )
                {
                        dl->twisted=1;
                        return lw_dist2d_line_poly((LWLINE *)lwg1,(LWPOLY *)lwg2,dl);
                }
                else
                {
                        lwerror("Unsupported geometry type: %s", lwgeom_typename(t2));
                        return LW_FALSE;
                }
        }
        else if ( t1 == POLYGONTYPE )
        {
                if ( t2 == POLYGONTYPE )
                {
                        dl->twisted=(1);
                        return lw_dist2d_poly_poly((LWPOLY *)lwg1,(LWPOLY *)lwg2,dl);
                }
                else if ( t2 == POINTTYPE )
                {
                        dl->twisted=(-1);
                        return lw_dist2d_point_poly((LWPOINT *)lwg2,  (LWPOLY *)lwg1, dl);
                }
                else if ( t2 == LINETYPE )
                {
                        dl->twisted=(-1);
                        return lw_dist2d_line_poly((LWLINE *)lwg2,(LWPOLY *)lwg1,dl);
                }
                else
                {
                        lwerror("Unsupported geometry type: %s", lwgeom_typename(t2));
                        return LW_FALSE;
                }
        }
        else
        {
                lwerror("Unsupported geometry type: %s", lwgeom_typename(t1));
                return LW_FALSE;
        }
        /*You shouldn't being able to get here*/
        lwerror("unspecified error in function lw_dist2d_distribute_bruteforce");
        return LW_FALSE;
}

/**

We have to check for overlapping bboxes
*/
int
lw_dist2d_check_overlap(LWGEOM *lwg1,LWGEOM *lwg2)
{
        LWDEBUG(2, "lw_dist2d_check_overlap is called");
        if ( ! lwg1->bbox )
                lwg1->bbox = lwgeom_compute_box2d(lwg1);
        if ( ! lwg2->bbox )
                lwg2->bbox = lwgeom_compute_box2d(lwg2);

        /*Check if the geometries intersect.
        */
        if ((lwg1->bbox->xmax<lwg2->bbox->xmin||lwg1->bbox->xmin>lwg2->bbox->xmax||lwg1->bbox->ymax<lwg2->bbox->ymin||lwg1->bbox->ymin>lwg2->bbox->ymax))
        {
                LWDEBUG(3, "geometries bboxes did not overlap");
                return LW_FALSE;
        }
        LWDEBUG(3, "geometries bboxes overlap");
        return LW_TRUE;
}

/**

Here the geometries are distributed for the new faster distance-calculations
*/
int
lw_dist2d_distribute_fast(LWGEOM *lwg1, LWGEOM *lwg2, DISTPTS *dl)
{
        LWDEBUGF(2, "lw_dist2d_distribute_fast is called with typ1=%d, type2=%d", TYPE_GETTYPE(lwg1->type), TYPE_GETTYPE(lwg2->type));

        POINTARRAY *pa1, *pa2;
        int     type1 = TYPE_GETTYPE(lwg1->type);
        int     type2 = TYPE_GETTYPE(lwg2->type);

        switch (type1)
        {
        case LINETYPE:
                pa1 = ((LWLINE *)lwg1)->points;
                break;
        case POLYGONTYPE:
                pa1 = ((LWPOLY *)lwg1)->rings[0];
                break;
        default:
                lwerror("Unsupported geometry1 type: %s", lwgeom_typename(type1));
                return LW_FALSE;
        }
        switch (type2)
        {
        case LINETYPE:
                pa2 = ((LWLINE *)lwg2)->points;
                break;
        case POLYGONTYPE:
                pa2 = ((LWPOLY *)lwg2)->rings[0];
                break;
        default:
                lwerror("Unsupported geometry2 type: %s", lwgeom_typename(type1));
                return LW_FALSE;
        }
        dl->twisted=1;
        return lw_dist2d_fast_ptarray_ptarray(pa1, pa2, dl, lwg1->bbox, lwg2->bbox);
}

/*------------------------------------------------------------------------------------------------------------
End of Preprocessing functions
--------------------------------------------------------------------------------------------------------------*/


/*------------------------------------------------------------------------------------------------------------
Brute force functions
The old way of calculating distances, now used for:
1)      distances to points (because there shouldn't be anything to gain by the new way of doing it)
2)      distances when subgeometries geometries bboxes overlaps
--------------------------------------------------------------------------------------------------------------*/

/**

point to point calculation
*/
int
lw_dist2d_point_point(LWPOINT *point1, LWPOINT *point2, DISTPTS *dl)
{
        POINT2D p1;
        POINT2D p2;

        getPoint2d_p(point1->point, 0, &p1);
        getPoint2d_p(point2->point, 0, &p2);

        return lw_dist2d_pt_pt(&p1, &p2,dl);
}
/**

point to line calculation
*/
int
lw_dist2d_point_line(LWPOINT *point, LWLINE *line, DISTPTS *dl)
{
        LWDEBUG(2, "lw_dist2d_point_line is called");
        POINT2D p;
        POINTARRAY *pa = line->points;
        getPoint2d_p(point->point, 0, &p);
        return lw_dist2d_pt_ptarray(&p, pa, dl);
}
/**
 * 1. see if pt in outer boundary. if no, then treat the outer ring like a line
 * 2. if in the boundary, test to see if its in a hole.
 *    if so, then return dist to hole, else return 0 (point in polygon)
 */
int
lw_dist2d_point_poly(LWPOINT *point, LWPOLY *poly, DISTPTS *dl)
{
        LWDEBUG(2, "lw_dist2d_point_poly called");

        POINT2D p;
        int i;

        getPoint2d_p(point->point, 0, &p);




        if (dl->mode == DIST2D_MAX)
        {
                LWDEBUG(3, "looking for maxdistance");
                return lw_dist2d_pt_ptarray(&p, poly->rings[0], dl);
        }
        /* Return distance to outer ring if not inside it */
        if ( ! pt_in_ring_2d(&p, poly->rings[0]) )
        {
                LWDEBUG(3, "first point not inside outer-ring");
                return lw_dist2d_pt_ptarray(&p, poly->rings[0], dl);
        }

        /*
         * Inside the outer ring.
         * Scan though each of the inner rings looking to
         * see if its inside.  If not, distance==0.
         * Otherwise, distance = pt to ring distance
         */
        for (i=1; i<poly->nrings; i++)
        {
                /* Inside a hole. Distance = pt -> ring */
                if ( pt_in_ring_2d(&p, poly->rings[i]) )
                {
                        LWDEBUG(3, " inside an hole");
                        return lw_dist2d_pt_ptarray(&p, poly->rings[i], dl);
                }
        }

        LWDEBUG(3, " inside the polygon");
        if (dl->mode == DIST2D_MIN)
        {
                dl->distance=0.0;
                dl->p1.x=p.x;
                dl->p1.y=p.y;
                dl->p2.x=p.x;
                dl->p2.y=p.y;
        }
        return LW_TRUE; /* Is inside the polygon */
}
/**

line to line calculation
*/
int
lw_dist2d_line_line(LWLINE *line1, LWLINE *line2, DISTPTS *dl)
{
        LWDEBUG(2, "lw_dist2d_line_line is called");
        POINTARRAY *pa1 = line1->points;
        POINTARRAY *pa2 = line2->points;
        return lw_dist2d_ptarray_ptarray(pa1, pa2, dl);
}
/**

line to polygon calculation
*/
int
lw_dist2d_line_poly(LWLINE *line, LWPOLY *poly, DISTPTS *dl)
{
        LWDEBUG(2, "lw_dist2d_line_poly is called");
        return lw_dist2d_ptarray_poly(line->points, poly, dl);
}

/**

Function handling polygon to polygon calculation
1       if we are looking for maxdistance, just check the outer rings.
2       check if poly1 has first point outside poly2 and vice versa, if so, just check outer rings
3       check if first point of poly2 is in a hole of poly1. If so check outer ring of poly2 against that hole of poly1
4       check if first point of poly1 is in a hole of poly2. If so check outer ring of poly1 against that hole of poly2
5       If we have come all the way here we know that the first point of one of them is inside the other ones outer ring and not in holes so we check wich one is inside.
 */
int
lw_dist2d_poly_poly(LWPOLY *poly1, LWPOLY *poly2, DISTPTS *dl)
{

        LWDEBUG(2, "lw_dist2d_poly_poly called");

        POINT2D pt;
        int i;


        /*1     if we are looking for maxdistance, just check the outer rings.*/
        if (dl->mode == DIST2D_MAX)
        {
                return lw_dist2d_ptarray_ptarray(poly1->rings[0],       poly2->rings[0],dl);
        }


        /* 2    check if poly1 has first point outside poly2 and vice versa, if so, just check outer rings
        here it would be possible to handle the information about wich one is inside wich one and only search for the smaller ones in the bigger ones holes.*/
        getPoint2d_p(poly1->rings[0], 0, &pt);
        if ( !pt_in_ring_2d(&pt, poly2->rings[0]))
        {
                getPoint2d_p(poly2->rings[0], 0, &pt);
                if (!pt_in_ring_2d(&pt, poly1->rings[0]))
                {
                        return lw_dist2d_ptarray_ptarray(poly1->rings[0],       poly2->rings[0],dl);
                }
        }

        /*3     check if first point of poly2 is in a hole of poly1. If so check outer ring of poly2 against that hole of poly1*/
        getPoint2d_p(poly2->rings[0], 0, &pt);
        for (i=1; i<poly1->nrings; i++)
        {
                /* Inside a hole */
                if ( pt_in_ring_2d(&pt, poly1->rings[i]) )
                {
                        return lw_dist2d_ptarray_ptarray(poly1->rings[i],       poly2->rings[0],dl);
                }
        }

        /*4     check if first point of poly1 is in a hole of poly2. If so check outer ring of poly1 against that hole of poly2*/
        getPoint2d_p(poly1->rings[0], 0, &pt);
        for (i=1; i<poly2->nrings; i++)
        {
                /* Inside a hole */
                if ( pt_in_ring_2d(&pt, poly2->rings[i]) )
                {
                        return lw_dist2d_ptarray_ptarray(poly1->rings[0],       poly2->rings[i],dl);
                }
        }


        /*5     If we have come all the way here we know that the first point of one of them is inside the other ones outer ring and not in holes so we check wich one is inside.*/
        getPoint2d_p(poly1->rings[0], 0, &pt);
        if ( pt_in_ring_2d(&pt, poly2->rings[0]))
        {
                dl->distance=0.0;
                dl->p1.x=pt.x;
                dl->p1.y=pt.y;
                dl->p2.x=pt.x;
                dl->p2.y=pt.y;
                return LW_TRUE;
        }

        getPoint2d_p(poly2->rings[0], 0, &pt);
        if (pt_in_ring_2d(&pt, poly1->rings[0]))
        {
                dl->distance=0.0;
                dl->p1.x=pt.x;
                dl->p1.y=pt.y;
                dl->p2.x=pt.x;
                dl->p2.y=pt.y;
                return LW_TRUE;
        }


        lwerror("Unspecified error in function lw_dist2d_poly_poly");
        return LW_FALSE;
}

/**

 * search all the segments of pointarray to see which one is closest to p1
 * Returns minimum distance between point and pointarray
 */
int
lw_dist2d_pt_ptarray(POINT2D *p, POINTARRAY *pa,DISTPTS *dl)
{
        LWDEBUG(2, "lw_dist2d_pt_ptarray is called");

        int t;
        POINT2D start, end;
        int twist = dl->twisted;
        getPoint2d_p(pa, 0, &start);

        for (t=1; t<pa->npoints; t++)
        {
                dl->twisted=twist;
                getPoint2d_p(pa, t, &end);
                if (!lw_dist2d_pt_seg(p, &start, &end,dl)) return LW_FALSE;

                if (dl->distance<=dl->tolerance && dl->mode == DIST2D_MIN) return LW_TRUE; /*just a check if  the answer is already given*/
                start = end;
        }

        return LW_TRUE;
}

/**
 * Brute force.
 * Test line-ring distance against each ring.
 * If there's an intersection (distance==0) then return 0 (crosses boundary).
 * Otherwise, test to see if any point is inside outer rings of polygon,
 * but not in inner rings.
 * If so, return 0  (line inside polygon),
 * otherwise return min distance to a ring (could be outside
 * polygon or inside a hole)
 */

int
lw_dist2d_ptarray_poly(POINTARRAY *pa, LWPOLY *poly, DISTPTS *dl)
{
        LWDEBUGF(2, "lw_dist2d_ptarray_poly called (%d rings)", poly->nrings);

        POINT2D pt;
        int i;



        getPoint2d_p(pa, 0, &pt);
        if ( !pt_in_ring_2d(&pt, poly->rings[0]))
        {
                return lw_dist2d_ptarray_ptarray(pa,poly->rings[0],dl);
        }

        for (i=1; i<poly->nrings; i++)
        {
                if (!lw_dist2d_ptarray_ptarray(pa, poly->rings[i], dl)) return LW_FALSE;

                LWDEBUGF(3, " distance from ring %d: %f, mindist: %f",
                         i, dist, mindist);
                if (dl->distance<=dl->tolerance && dl->mode == DIST2D_MIN) return LW_TRUE; /*just a check if  the answer is already given*/
        }

        /*
         * No intersection, have to check if a point is
         * inside polygon
         */
        getPoint2d_p(pa, 0, &pt);

        /*
         * Outside outer ring, so min distance to a ring
         * is the actual min distance

        if ( ! pt_in_ring_2d(&pt, poly->rings[0]) )
        {
                return ;
        } */

        /*
         * Its in the outer ring.
         * Have to check if its inside a hole
         */
        for (i=1; i<poly->nrings; i++)
        {
                if ( pt_in_ring_2d(&pt, poly->rings[i]) )
                {
                        /*
                         * Its inside a hole, then the actual
                         * distance is the min ring distance
                         */
                        return LW_TRUE;
                }
        }
        if (dl->mode == DIST2D_MIN)
        {
                dl->distance=0.0;
                dl->p1.x=pt.x;
                dl->p1.y=pt.y;
                dl->p2.x=pt.x;
                dl->p2.y=pt.y;
        }
        return LW_TRUE; /* Not in hole, so inside polygon */
}



/**

test each segment of l1 against each segment of l2.
*/
int
lw_dist2d_ptarray_ptarray(POINTARRAY *l1, POINTARRAY *l2,DISTPTS *dl)
{
        LWDEBUG(2, "lw_dist2d_ptarray_ptarray is called");

        int t,u;
        POINT2D start, end;
        POINT2D start2, end2;
        int twist = dl->twisted;
        LWDEBUGF(2, "lw_dist2d_ptarray_ptarray called (points: %d-%d)",l1->npoints, l2->npoints);
        if (dl->mode == DIST2D_MAX)/*If we are searching for maxdistance we go straight to point-point calculation since the maxdistance have to be between two vertexes*/
        {
                for (t=0; t<l1->npoints; t++) /*for each segment in L1 */
                {
                        getPoint2d_p(l1, t, &start);
                        for (u=0; u<l2->npoints; u++) /*for each segment in L2 */
                        {
                                getPoint2d_p(l2, u, &start2);
                                lw_dist2d_pt_pt(&start,&start2,dl);
                                LWDEBUGF(4, "maxdist_ptarray_ptarray; seg %i * seg %i, dist = %g\n",t,u,dist);
                                LWDEBUGF(3, " seg%d-seg%d dist: %f, mindist: %f",
                                         t, u, dl->distance, result);
                        }
                }
        }
        else
        {
                getPoint2d_p(l1, 0, &start);
                for (t=1; t<l1->npoints; t++) /*for each segment in L1 */
                {
                        getPoint2d_p(l1, t, &end);
                        getPoint2d_p(l2, 0, &start2);
                        for (u=1; u<l2->npoints; u++) /*for each segment in L2 */
                        {
                                getPoint2d_p(l2, u, &end2);
                                dl->twisted=twist;
                                lw_dist2d_seg_seg(&start, &end, &start2, &end2,dl);
                                LWDEBUGF(4, "mindist_ptarray_ptarray; seg %i * seg %i, dist = %g\n",t,u,dist);
                                LWDEBUGF(3, " seg%d-seg%d dist: %f, mindist: %f",
                                         t, u, dl->distance, result);
                                if (dl->distance<=dl->tolerance && dl->mode == DIST2D_MIN) return LW_TRUE; /*just a check if  the answer is already given*/
                                start2 = end2;
                        }
                        start = end;
                }
        }
        return LW_TRUE;
}

/**

Finds the shortest distance between two segments.
This function is changed so it is not doing any comparasion of distance
but just sending every possible combination further to lw_dist2d_pt_seg
*/
int
lw_dist2d_seg_seg(POINT2D *A, POINT2D *B, POINT2D *C, POINT2D *D, DISTPTS *dl)
{
        LWDEBUGF(2, "lw_dist2d_seg_seg [%g,%g]->[%g,%g] by [%g,%g]->[%g,%g]",
                 A->x,A->y,B->x,B->y, C->x,C->y, D->x, D->y);

        double  s_top, s_bot,s;
        double  r_top, r_bot,r;




        /*A and B are the same point */
        if (  ( A->x == B->x) && (A->y == B->y) )
        {
                return lw_dist2d_pt_seg(A,C,D,dl);
        }
        /*U and V are the same point */

        if (  ( C->x == D->x) && (C->y == D->y) )
        {
                dl->twisted= ((dl->twisted) * (-1));
                return lw_dist2d_pt_seg(D,A,B,dl);
        }
        /* AB and CD are line segments */
        /* from comp.graphics.algo

        Solving the above for r and s yields
                                (Ay-Cy)(Dx-Cx)-(Ax-Cx)(Dy-Cy)
                   r = ----------------------------- (eqn 1)
                                (Bx-Ax)(Dy-Cy)-(By-Ay)(Dx-Cx)

                        (Ay-Cy)(Bx-Ax)-(Ax-Cx)(By-Ay)
                s = ----------------------------- (eqn 2)
                        (Bx-Ax)(Dy-Cy)-(By-Ay)(Dx-Cx)
        Let P be the position vector of the intersection point, then
                P=A+r(B-A) or
                Px=Ax+r(Bx-Ax)
                Py=Ay+r(By-Ay)
        By examining the values of r & s, you can also determine some other limiting conditions:
                If 0<=r<=1 & 0<=s<=1, intersection exists
                r<0 or r>1 or s<0 or s>1 line segments do not intersect
                If the denominator in eqn 1 is zero, AB & CD are parallel
                If the numerator in eqn 1 is also zero, AB & CD are collinear.

        */
        r_top = (A->y-C->y)*(D->x-C->x) - (A->x-C->x)*(D->y-C->y) ;
        r_bot = (B->x-A->x)*(D->y-C->y) - (B->y-A->y)*(D->x-C->x) ;

        s_top = (A->y-C->y)*(B->x-A->x) - (A->x-C->x)*(B->y-A->y);
        s_bot = (B->x-A->x)*(D->y-C->y) - (B->y-A->y)*(D->x-C->x);

        if  ( (r_bot==0) || (s_bot == 0) )
        {
                if ((lw_dist2d_pt_seg(A,C,D,dl)) && (lw_dist2d_pt_seg(B,C,D,dl)))
                {
                        dl->twisted= ((dl->twisted) * (-1));  /*here we change the order of inputted geometrys and that we  notice by changing sign on dl->twisted*/
                        return ((lw_dist2d_pt_seg(C,A,B,dl)) && (lw_dist2d_pt_seg(D,A,B,dl))); /*if all is successful we return true*/
                }
                else
                {
                        return LW_FALSE; /* if any of the calls to lw_dist2d_pt_seg goes wrong we return false*/
                }
        }

        s = s_top/s_bot;
        r=  r_top/r_bot;

        if (((r<0) || (r>1) || (s<0) || (s>1)) || (dl->mode == DIST2D_MAX))
        {
                if ((lw_dist2d_pt_seg(A,C,D,dl)) && (lw_dist2d_pt_seg(B,C,D,dl)))
                {
                        dl->twisted= ((dl->twisted) * (-1));  /*here we change the order of inputted geometrys and that we  notice by changing sign on dl->twisted*/
                        return ((lw_dist2d_pt_seg(C,A,B,dl)) && (lw_dist2d_pt_seg(D,A,B,dl))); /*if all is successful we return true*/
                }
                else
                {
                        return LW_FALSE; /* if any of the calls to lw_dist2d_pt_seg goes wrong we return false*/
                }
        }
        else
        {
                if (dl->mode == DIST2D_MIN)     /*If there is intersection we identify the intersection point and return it but only if we are looking for mindistance*/
                {
                        POINT2D theP;

                        if (((A->x==C->x)&&(A->y==C->y))||((A->x==D->x)&&(A->y==D->y)))
                        {
                                theP.x = A->x;
                                theP.y = A->y;
                        }
                        else if (((B->x==C->x)&&(B->y==C->y))||((B->x==D->x)&&(B->y==D->y)))
                        {
                                theP.x = B->x;
                                theP.y = B->y;
                        }
                        else
                        {
                                theP.x = A->x+r*(B->x-A->x);
                                theP.y = A->y+r*(B->y-A->y);
                        }
                        dl->distance=0.0;
                        dl->p1=theP;
                        dl->p2=theP;
                }
                return LW_TRUE;

        }
        lwerror("unspecified error in function lw_dist2d_seg_seg");
        return LW_FALSE; /*If we have come here something is wrong*/
}


/*------------------------------------------------------------------------------------------------------------
End of Brute force functions
--------------------------------------------------------------------------------------------------------------*/


/*------------------------------------------------------------------------------------------------------------
New faster distance calculations
--------------------------------------------------------------------------------------------------------------*/

/**

The new faster calculation comparing pointarray to another pointarray
the arrays can come from both polygons and linestrings.
The naming is not good but comes from that it compares a
chosen selection of the points not all of them
*/
int
lw_dist2d_fast_ptarray_ptarray(POINTARRAY *l1, POINTARRAY *l2,DISTPTS *dl, BOX2DFLOAT4 *box1, BOX2DFLOAT4 *box2)
{
        LWDEBUG(2, "lw_dist2d_fast_ptarray_ptarray is called");
        /*here we define two lists to hold our calculated "z"-values and the order number in the geometry*/

        double k, thevalue;
        float   deltaX, deltaY, c1m, c2m;
        POINT2D theP,c1, c2;
        float min1X, max1X, max1Y, min1Y,min2X, max2X, max2Y, min2Y;
        int t,  n1, n2;
        n1 = l1->npoints;
        n2 = l2->npoints;

        LISTSTRUCT list1[n1];
        LISTSTRUCT list2[n2];

        max1X = box1->xmax;
        min1X = box1->xmin;
        max1Y = box1->ymax;
        min1Y = box1->ymin;
        max2X = box2->xmax;
        min2X = box2->xmin;
        max2Y = box2->ymax;
        min2Y = box2->ymin;
        /*we want the center of the bboxes, and calculate the slope between the centerpoints*/
        c1.x = min1X + (max1X-min1X)/2;
        c1.y = min1Y + (max1Y-min1Y)/2;
        c2.x = min2X + (max2X-min2X)/2;
        c2.y = min2Y + (max2Y-min2Y)/2;

        deltaX=(c2.x-c1.x);
        deltaY=(c2.y-c1.y);


        /*Here we calculate where the line perpendicular to the center-center line crosses the axes for each vertex
        if the center-center line is vertical the perpendicular line will be horizontal and we find it's crossing the Y-axes with z = y-kx */
        if ((deltaX*deltaX)<(deltaY*deltaY))        /*North or South*/
        {
                k = -deltaX/deltaY;
                for (t=0; t<n1; t++) /*for each segment in L1 */
                {
                        getPoint2d_p(l1, t, &theP);
                        thevalue = theP.y-(k*theP.x);
                        list1[t].themeasure=thevalue;
                        list1[t].pnr=t;

                }
                for (t=0; t<n2; t++) /*for each segment in L2*/
                {
                        getPoint2d_p(l2, t, &theP);
                        thevalue = theP.y-(k*theP.x);
                        list2[t].themeasure=thevalue;
                        list2[t].pnr=t;

                }
                c1m = c1.y-(k*c1.x);
                c2m = c2.y-(k*c2.x);
        }


        /*if the center-center line is horizontal the perpendicular line will be vertical. To eliminate problems with deviding by zero we are here mirroring the coordinate-system
         and we find it's crossing the X-axes with z = x-(1/k)y */
        else        /*West or East*/
        {
                k = -deltaY/deltaX;
                for (t=0; t<n1; t++) /*for each segment in L1 */
                {
                        getPoint2d_p(l1, t, &theP);
                        thevalue = theP.x-(k*theP.y);
                        list1[t].themeasure=thevalue;
                        list1[t].pnr=t;
                        /*lwnotice("1pnr=%d, pnr=%d, themeasure=%f, themeasure=%f",t,list1[t].pnr,thevalue,list1[t].themeasure  );*/
                }
                for (t=0; t<n2; t++) /*for each segment in L2*/
                {
                        getPoint2d_p(l2, t, &theP);

                        thevalue = theP.x-(k*theP.y);
                        list2[t].themeasure=thevalue;
                        list2[t].pnr=t;
                }
                c1m = c1.x-(k*c1.y);
                c2m = c2.x-(k*c2.y);
        }

        /*we sort our lists by the calculated values*/
        qsort(list1, n1, sizeof(LISTSTRUCT), struct_cmp_by_measure);
        qsort(list2, n2, sizeof(LISTSTRUCT), struct_cmp_by_measure);

        if (c1m < c2m)
        {
                if (!lw_dist2d_pre_seg_seg(l1,l2,list1,list2,k,dl)) return LW_FALSE;
        }
        else
        {
                dl->twisted= ((dl->twisted) * (-1));
                if (!lw_dist2d_pre_seg_seg(l2,l1,list2,list1,k,dl)) return LW_FALSE;
        }
        return LW_TRUE;
}

int
struct_cmp_by_measure(const void *a, const void *b)
{
        LISTSTRUCT *ia = (LISTSTRUCT*)a;
        LISTSTRUCT *ib = (LISTSTRUCT*)b;
        return ( ia->themeasure>ib->themeasure ) ? 1 : -1;
}

/**
        preparation before lw_dist2d_seg_seg.
*/
int
lw_dist2d_pre_seg_seg(POINTARRAY *l1, POINTARRAY *l2,LISTSTRUCT *list1, LISTSTRUCT *list2,double k, DISTPTS *dl)
{
        LWDEBUG(2, "lw_dist2d_pre_seg_seg is called");


        POINT2D p1, p2, p3, p4, p01, p02;
        int pnr1,pnr2,pnr3,pnr4, n1, n2, i, u, r, twist;

        double maxmeasure;
        n1=     l1->npoints;
        n2 = l2->npoints;


        getPoint2d_p(l1, list1[0].pnr, &p1);
        getPoint2d_p(l2, list2[0].pnr, &p3);
        lw_dist2d_pt_pt(&p1, &p3,dl);
        maxmeasure = sqrt(dl->distance*dl->distance + (dl->distance*dl->distance*k*k));
        twist = dl->twisted; /*to keep the incomming order between iterations*/
        for (i =(n1-1); i>=0; --i)
        {
                /*we break this iteration when we have checked every
                point closer to our perpendicular "checkline" than
                our shortest found distance*/
                if (((list2[0].themeasure-list1[i].themeasure)) > maxmeasure) break;
                for (r=-1; r<=1; r +=2) /*because we are not iterating in the original pointorder we have to check the segment before and after every point*/
                {
                        pnr1 = list1[i].pnr;
                        getPoint2d_p(l1, pnr1, &p1);
                        if (pnr1+r<0)
                        {
                                getPoint2d_p(l1, (n1-1), &p01);
                                if (( p1.x == p01.x) && (p1.y == p01.y)) pnr2 = (n1-1);
                                else pnr2 = pnr1; /* if it is a line and the last and first point is not the same we avoid the edge between start and end this way*/
                        }

                        else if (pnr1+r>(n1-1))
                        {
                                getPoint2d_p(l1, 0, &p01);
                                if (( p1.x == p01.x) && (p1.y == p01.y)) pnr2 = 0;
                                else pnr2 = pnr1; /* if it is a line and the last and first point is not the same we avoid the edge between start and end this way*/
                        }
                        else pnr2 = pnr1+r;


                        getPoint2d_p(l1, pnr2, &p2);
                        for (u=0; u<n2; ++u)
                        {
                                if (((list2[u].themeasure-list1[i].themeasure)) >= maxmeasure) break;
                                pnr3 = list2[u].pnr;
                                getPoint2d_p(l2, pnr3, &p3);
                                if (pnr3==0)
                                {
                                        getPoint2d_p(l2, (n2-1), &p02);
                                        if (( p3.x == p02.x) && (p3.y == p02.y)) pnr4 = (n2-1);
                                        else pnr4 = pnr3; /* if it is a line and the last and first point is not the same we avoid the edge between start and end this way*/
                                }
                                else pnr4 = pnr3-1;

                                getPoint2d_p(l2, pnr4, &p4);
                                dl->twisted=twist;
                                if (!lw_dist2d_selected_seg_seg(&p1, &p2, &p3, &p4, dl)) return LW_FALSE;

                                if (pnr3>=(n2-1))
                                {
                                        getPoint2d_p(l2, 0, &p02);
                                        if (( p3.x == p02.x) && (p3.y == p02.y)) pnr4 = 0;
                                        else pnr4 = pnr3; /* if it is a line and the last and first point is not the same we avoid the edge between start and end this way*/
                                }

                                else pnr4 = pnr3+1;

                                getPoint2d_p(l2, pnr4, &p4);
                                dl->twisted=twist; /*we reset the "twist" for each iteration*/
                                if (!lw_dist2d_selected_seg_seg(&p1, &p2, &p3, &p4, dl)) return LW_FALSE;

                                maxmeasure = sqrt(dl->distance*dl->distance + (dl->distance*dl->distance*k*k));/*here we "translate" the found mindistance so it can be compared to our "z"-values*/
                        }
                }
        }

        return LW_TRUE;
}


/**
        This is the same function as lw_dist2d_seg_seg but
        without any calculations to determine intersection since we
        already know they do not intersect
*/
int
lw_dist2d_selected_seg_seg(POINT2D *A, POINT2D *B, POINT2D *C, POINT2D *D, DISTPTS *dl)
{
        LWDEBUGF(2, "lw_dist2d_selected_seg_seg [%g,%g]->[%g,%g] by [%g,%g]->[%g,%g]",
                 A->x,A->y,B->x,B->y, C->x,C->y, D->x, D->y);

        /*A and B are the same point */
        if (  ( A->x == B->x) && (A->y == B->y) )
        {
                return lw_dist2d_pt_seg(A,C,D,dl);
        }
        /*U and V are the same point */

        if (  ( C->x == D->x) && (C->y == D->y) )
        {
                dl->twisted= ((dl->twisted) * (-1));
                return lw_dist2d_pt_seg(D,A,B,dl);
        }

        if ((lw_dist2d_pt_seg(A,C,D,dl)) && (lw_dist2d_pt_seg(B,C,D,dl)))
        {
                dl->twisted= ((dl->twisted) * (-1));  /*here we change the order of inputted geometrys and that we  notice by changing sign on dl->twisted*/
                return ((lw_dist2d_pt_seg(C,A,B,dl)) && (lw_dist2d_pt_seg(D,A,B,dl))); /*if all is successful we return true*/
        }
        else
        {
                return LW_FALSE; /* if any of the calls to lw_dist2d_pt_seg goes wrong we return false*/
        }
}

/*------------------------------------------------------------------------------------------------------------
End of New faster distance calculations
--------------------------------------------------------------------------------------------------------------*/


/*------------------------------------------------------------------------------------------------------------
Functions in common for Brute force and new calculation
--------------------------------------------------------------------------------------------------------------*/

/**
 * pt_in_ring_2d(): crossing number test for a point in a polygon
 *      input:   p = a point,
 *               pa = vertex points of a ring V[n+1] with V[n]=V[0]
 *      returns: 0 = outside, 1 = inside
 *
 *      Our polygons have first and last point the same,
 *
 */
int
pt_in_ring_2d(POINT2D *p, POINTARRAY *ring)
{
        int cn = 0;    /* the crossing number counter */
        int i;
        POINT2D v1, v2;

#if INTEGRITY_CHECKS
        POINT2D first, last;

        getPoint2d_p(ring, 0, &first);
        getPoint2d_p(ring, ring->npoints-1, &last);
        if ( memcmp(&first, &last, sizeof(POINT2D)) )
        {
                lwerror("pt_in_ring_2d: V[n] != V[0] (%g %g != %g %g)",
                        first.x, first.y, last.x, last.y);
                return LW_FALSE;

        }
#endif

        LWDEBUGF(2, "pt_in_ring_2d called with point: %g %g", p->x, p->y);
        /* printPA(ring); */

        /* loop through all edges of the polygon */
        getPoint2d_p(ring, 0, &v1);
        for (i=0; i<ring->npoints-1; i++)
        {
                double vt;
                getPoint2d_p(ring, i+1, &v2);

                /* edge from vertex i to vertex i+1 */
                if
                (
                    /* an upward crossing */
                    ((v1.y <= p->y) && (v2.y > p->y))
                    /* a downward crossing */
                    || ((v1.y > p->y) && (v2.y <= p->y))
                )
                {

                        vt = (double)(p->y - v1.y) / (v2.y - v1.y);

                        /* P.x <intersect */
                        if (p->x < v1.x + vt * (v2.x - v1.x))
                        {
                                /* a valid crossing of y=p.y right of p.x */
                                ++cn;
                        }
                }
                v1 = v2;
        }

        LWDEBUGF(3, "pt_in_ring_2d returning %d", cn&1);

        return (cn&1);    /* 0 if even (out), and 1 if odd (in) */
}


/**

lw_dist2d_comp from p to line A->B
This one is now sending every occation to lw_dist2d_pt_pt
Before it was handling occations where r was between 0 and 1 internally
and just returning the distance without identifying the points.
To get this points it was nessecary to change and it also showed to be about 10%faster.
*/
int
lw_dist2d_pt_seg(POINT2D *p, POINT2D *A, POINT2D *B, DISTPTS *dl)
{
        double  r;
        /*if start==end, then use pt distance */
        if (  ( A->x == B->x) && (A->y == B->y) )
        {
                return lw_dist2d_pt_pt(p,A,dl);
        }
        /*
         * otherwise, we use comp.graphics.algorithms
         * Frequently Asked Questions method
         *
         *  (1)               AC dot AB
             *         r = ---------
             *               ||AB||^2
         *      r has the following meaning:
         *      r=0 P = A
         *      r=1 P = B
         *      r<0 P is on the backward extension of AB
         *      r>1 P is on the forward extension of AB
         *      0<r<1 P is interior to AB
         */

        r = ( (p->x-A->x) * (B->x-A->x) + (p->y-A->y) * (B->y-A->y) )/( (B->x-A->x)*(B->x-A->x) +(B->y-A->y)*(B->y-A->y) );

        /*This is for finding the maxdistance.
        the maxdistance have to be between two vertexes,
        compared to mindistance which can be between
        tvo vertexes vertex.*/
        if (dl->mode == DIST2D_MAX)
        {
                if (r>=0.5)
                {
                        return lw_dist2d_pt_pt(p,A,dl);
                }
                if (r<0.5)
                {
                        return lw_dist2d_pt_pt(p,B,dl);
                }
        }

        if (r<0)        /*If the first vertex A is closest to the point p*/
        {
                return lw_dist2d_pt_pt(p,A,dl);
        }
        if (r>1)        /*If the second vertex B is closest to the point p*/
        {
                return lw_dist2d_pt_pt(p,B,dl);
        }


        /*else if the point p is closer to some point between a and b
        then we find that point and send it to lw_dist2d_pt_pt*/
        POINT2D c;
        c.x=A->x + r * (B->x-A->x);
        c.y=A->y + r * (B->y-A->y);

        return lw_dist2d_pt_pt(p,&c,dl);
}


/**

Compares incomming points and
stores the points closest to each other
or most far away from each other
depending on dl->mode (max or min)
*/
int
lw_dist2d_pt_pt(POINT2D *thep1, POINT2D *thep2,DISTPTS *dl)
{
        double hside = thep2->x - thep1->x;
        double vside = thep2->y - thep1->y;
        double dist = sqrt ( hside*hside + vside*vside );

        if (((dl->distance - dist)*(dl->mode))>0) /*multiplication with mode to handle mindistance (mode=1)  and maxdistance (mode = (-1)*/
        {
                dl->distance = dist;

                if (dl->twisted>0)      /*To get the points in right order. twisted is updated between 1 and (-1) every time the order is changed earlier in the chain*/
                {
                        dl->p1 = *thep1;
                        dl->p2 = *thep2;
                }
                else
                {
                        dl->p1 = *thep2;
                        dl->p2 = *thep1;
                }
        }
        return LW_TRUE;
}




/*------------------------------------------------------------------------------------------------------------
End of Functions in common for Brute force and new calculation
--------------------------------------------------------------------------------------------------------------*/


/*Mixed functions*/


/**

 true if point is in poly (and not in its holes)
 It's not used by postgis but since I don't know what else
 can be affectes in the world I don't dare removing it.
 */
int
pt_in_poly_2d(POINT2D *p, LWPOLY *poly)
{
        int i;

        /* Not in outer ring */
        if ( ! pt_in_ring_2d(p, poly->rings[0]) ) return 0;

        /* Check holes */
        for (i=1; i<poly->nrings; i++)
        {
                /* Inside a hole */
                if ( pt_in_ring_2d(p, poly->rings[i]) ) return 0;
        }

        return 1; /* In outer ring, not in holes */
}


/**
The old function nessecary for ptarray_segmentize2d in ptarray.c
*/
double
distance2d_pt_pt(POINT2D *p1, POINT2D *p2)
{
        double hside = p2->x - p1->x;
        double vside = p2->y - p1->y;

        return sqrt ( hside*hside + vside*vside );

        /* the above is more readable
           return sqrt(
                (p2->x-p1->x) * (p2->x-p1->x) + (p2->y-p1->y) * (p2->y-p1->y)
                );  */
}



/**

The old function nessecary for ptarray_segmentize2d in ptarray.c
*/
double
distance2d_pt_seg(POINT2D *p, POINT2D *A, POINT2D *B)
{
        double  r,s;

        /*if start==end, then use pt distance */
        if (  ( A->x == B->x) && (A->y == B->y) )
                return distance2d_pt_pt(p,A);

        /*
         * otherwise, we use comp.graphics.algorithms
         * Frequently Asked Questions method
         *
         *  (1)               AC dot AB
                *         r = ---------
                *               ||AB||^2
         *      r has the following meaning:
         *      r=0 P = A
         *      r=1 P = B
         *      r<0 P is on the backward extension of AB
         *      r>1 P is on the forward extension of AB
         *      0<r<1 P is interior to AB
         */

        r = ( (p->x-A->x) * (B->x-A->x) + (p->y-A->y) * (B->y-A->y) )/( (B->x-A->x)*(B->x-A->x) +(B->y-A->y)*(B->y-A->y) );

        if (r<0) return distance2d_pt_pt(p,A);
        if (r>1) return distance2d_pt_pt(p,B);


        /*
         * (2)
         *           (Ay-Cy)(Bx-Ax)-(Ax-Cx)(By-Ay)
         *      s = -----------------------------
         *                      L^2
         *
         *      Then the distance from C to P = |s|*L.
         *
         */

        s = ( (A->y-p->y)*(B->x-A->x)- (A->x-p->x)*(B->y-A->y) ) /
            ( (B->x-A->x)*(B->x-A->x) +(B->y-A->y)*(B->y-A->y) );

        return LW_ABS(s) * sqrt(
                   (B->x-A->x)*(B->x-A->x) + (B->y-A->y)*(B->y-A->y)
               );
}







/**
find the 2d length of the given POINTARRAY (even if it's 3d)
*/
double
lwgeom_pointarray_length2d(POINTARRAY *pts)
{
        double dist = 0.0;
        int i;
        POINT2D frm;
        POINT2D to;

        if ( pts->npoints < 2 ) return 0.0;
        for (i=0; i<pts->npoints-1; i++)
        {
                getPoint2d_p(pts, i, &frm);
                getPoint2d_p(pts, i+1, &to);
                dist += sqrt( ( (frm.x - to.x)*(frm.x - to.x) )  +
                              ((frm.y - to.y)*(frm.y - to.y) ) );
        }
        return dist;
}

/**
 * Find the 3d/2d length of the given POINTARRAY
 * (depending on its dimensions)
 */
double
lwgeom_pointarray_length(POINTARRAY *pts)
{
        double dist = 0.0;
        int i;
        POINT3DZ frm;
        POINT3DZ to;

        if ( pts->npoints < 2 ) return 0.0;

        /* compute 2d length if 3d is not available */
        if ( ! TYPE_HASZ(pts->dims) ) return lwgeom_pointarray_length2d(pts);

        for (i=0; i<pts->npoints-1; i++)
        {
                getPoint3dz_p(pts, i, &frm);
                getPoint3dz_p(pts, i+1, &to);
                dist += sqrt( ( (frm.x - to.x)*(frm.x - to.x) )  +
                              ((frm.y - to.y)*(frm.y - to.y) ) +
                              ((frm.z - to.z)*(frm.z - to.z) ) );
        }
        return dist;
}

/**
 * This should be rewritten to make use of the curve itself.
 */
double
lwgeom_curvepolygon_area(LWCURVEPOLY *curvepoly)
{
        LWPOLY *poly = (LWPOLY *)lwgeom_segmentize((LWGEOM *)curvepoly, 32);
        return lwgeom_polygon_area(poly);
}

/**
 * Find the area of the outer ring - sum (area of inner rings).
 * Could use a more numerically stable calculator...
 */
double
lwgeom_polygon_area(LWPOLY *poly)
{
        double poly_area=0.0;
        int i;
        POINT2D p1;
        POINT2D p2;

        LWDEBUGF(2, "in lwgeom_polygon_area (%d rings)", poly->nrings);

        for (i=0; i<poly->nrings; i++)
        {
                int j;
                POINTARRAY *ring = poly->rings[i];
                double ringarea = 0.0;

                LWDEBUGF(4, " rings %d has %d points", i, ring->npoints);

                if ( ! ring->npoints ) continue; /* empty ring */
                for (j=0; j<ring->npoints-1; j++)
                {
                        getPoint2d_p(ring, j, &p1);
                        getPoint2d_p(ring, j+1, &p2);
                        ringarea += ( p1.x * p2.y ) - ( p1.y * p2.x );
                }

                ringarea  /= 2.0;

                LWDEBUGF(4, " ring 1 has area %lf",ringarea);

                ringarea  = fabs(ringarea);
                if (i != 0)     /*outer */
                        ringarea  = -1.0*ringarea ; /* its a hole */

                poly_area += ringarea;
        }

        return poly_area;
}

/**
 * Compute the sum of polygon rings length.
 * Could use a more numerically stable calculator...
 */
double
lwgeom_polygon_perimeter(LWPOLY *poly)
{
        double result=0.0;
        int i;

        LWDEBUGF(2, "in lwgeom_polygon_perimeter (%d rings)", poly->nrings);

        for (i=0; i<poly->nrings; i++)
                result += lwgeom_pointarray_length(poly->rings[i]);

        return result;
}

/**
 * Compute the sum of polygon rings length (forcing 2d computation).
 * Could use a more numerically stable calculator...
 */
double
lwgeom_polygon_perimeter2d(LWPOLY *poly)
{
        double result=0.0;
        int i;

        LWDEBUGF(2, "in lwgeom_polygon_perimeter (%d rings)", poly->nrings);

        for (i=0; i<poly->nrings; i++)
                result += lwgeom_pointarray_length2d(poly->rings[i]);

        return result;
}


int
lwgeom_pt_inside_circle(POINT2D *p, double cx, double cy, double rad)
{
        POINT2D center;

        center.x = cx;
        center.y = cy;

        if ( distance2d_pt_pt(p, &center) < rad ) return 1;
        else return 0;

}

/**
 * Compute the azimuth of segment AB in radians.
 * Return 0 on exception (same point), 1 otherwise.
 */
int
azimuth_pt_pt(POINT2D *A, POINT2D *B, double *d)
{
        if ( A->x == B->x )
        {
                if ( A->y < B->y ) *d=0.0;
                else if ( A->y > B->y ) *d=M_PI;
                else return 0;
                return 1;
        }

        if ( A->y == B->y )
        {
                if ( A->x < B->x ) *d=M_PI/2;
                else if ( A->x > B->x ) *d=M_PI+(M_PI/2);
                else return 0;
                return 1;
        }

        if ( A->x < B->x )
        {
                if ( A->y < B->y )
                {
                        *d=atan(fabs(A->x - B->x) / fabs(A->y - B->y) );
                }
                else /* ( A->y > B->y )  - equality case handled above */
                {
                        *d=atan(fabs(A->y - B->y) / fabs(A->x - B->x) )
                           + (M_PI/2);
                }
        }

        else /* ( A->x > B->x ) - equality case handled above */
        {
                if ( A->y > B->y )
                {
                        *d=atan(fabs(A->x - B->x) / fabs(A->y - B->y) )
                           + M_PI;
                }
                else /* ( A->y < B->y )  - equality case handled above */
                {
                        *d=atan(fabs(A->y - B->y) / fabs(A->x - B->x) )
                           + (M_PI+(M_PI/2));
                }
        }

        return 1;
}