From 4ae6967f5fcee119d2dba964cf5217b521be37e8 Mon Sep 17 00:00:00 2001 From: Bruce Momjian Date: Mon, 5 Mar 2007 23:29:14 +0000 Subject: [PATCH] Remove copied comments from geo_ops.c source file and replace with new comments, and cleanup functions. Remove copyright that is no longer relevant. --- src/backend/utils/adt/geo_ops.c | 148 ++++++++++++++++---------------- 1 file changed, 73 insertions(+), 75 deletions(-) diff --git a/src/backend/utils/adt/geo_ops.c b/src/backend/utils/adt/geo_ops.c index 3360c07afc..33a781bb30 100644 --- a/src/backend/utils/adt/geo_ops.c +++ b/src/backend/utils/adt/geo_ops.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/utils/adt/geo_ops.c,v 1.95 2007/02/27 23:48:08 tgl Exp $ + * $PostgreSQL: pgsql/src/backend/utils/adt/geo_ops.c,v 1.96 2007/03/05 23:29:14 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -5063,128 +5063,126 @@ poly_circle(PG_FUNCTION_ARGS) ***********************************************************************/ /* - * Test to see if the point is inside the polygon. - * Code adapted from integer-based routines in WN: A Server for the HTTP + * Test to see if the point is inside the polygon, returns 1/0, or 2 if + * the point is on the polygon. + * Code adapted but not copied from integer-based routines in WN: A + * Server for the HTTP * version 1.15.1, file wn/image.c - * GPL Copyright (C) 1995 by John Franks * http://hopf.math.northwestern.edu/index.html * Description of algorithm: http://www.linuxjournal.com/article/2197 + * http://www.linuxjournal.com/article/2029 */ -#define HIT_IT INT_MAX +#define POINT_ON_POLYGON INT_MAX static int point_inside(Point *p, int npts, Point *plist) { double x0, y0; - double px, - py; - int i; + double prev_x, + prev_y; + int i = 0; double x, y; - int cross, - crossnum; - -/* - * We calculate crossnum, which is twice the crossing number of a - * ray from the origin parallel to the positive X axis. - * A coordinate change is made to move the test point to the origin. - * Then the function lseg_crossing() is called to calculate the crossnum of - * one segment of the translated polygon with the ray which is the - * positive X-axis. - */ + int cross, total_cross = 0; - crossnum = 0; - i = 0; if (npts <= 0) return 0; + /* compute first polygon point relative to single point */ x0 = plist[0].x - p->x; y0 = plist[0].y - p->y; - px = x0; - py = y0; + prev_x = x0; + prev_y = y0; + /* loop over polygon points and aggregate total_cross */ for (i = 1; i < npts; i++) { + /* compute next polygon point relative to single point */ x = plist[i].x - p->x; y = plist[i].y - p->y; - if ((cross = lseg_crossing(x, y, px, py)) == HIT_IT) + /* compute previous to current point crossing */ + if ((cross = lseg_crossing(x, y, prev_x, prev_y)) == POINT_ON_POLYGON) return 2; - crossnum += cross; - - px = x; - py = y; + total_cross += cross; + + prev_x = x; + prev_y = y; } - if ((cross = lseg_crossing(x0, y0, px, py)) == HIT_IT) + + /* now do the first point */ + if ((cross = lseg_crossing(x0, y0, prev_x, prev_y)) == POINT_ON_POLYGON) return 2; - crossnum += cross; - if (crossnum != 0) + total_cross += cross; + + if (total_cross != 0) return 1; return 0; } /* lseg_crossing() - * The function lseg_crossing() returns +2, or -2 if the segment from (x,y) - * to previous (x,y) crosses the positive X-axis positively or negatively. - * It returns +1 or -1 if one endpoint is on this ray, or 0 if both are. - * It returns 0 if the ray and the segment don't intersect. - * It returns HIT_IT if the segment contains (0,0) + * Returns +/-2 if line segment crosses the positive X-axis in a +/- direction. + * Returns +/-1 if one point is on the positive X-axis. + * Returns 0 if both points are on the positive X-axis, or there is no crossing. + * Returns POINT_ON_POLYGON if the segment contains (0,0). + * Wow, that is one confusing API, but it is used above, and when summed, + * can tell is if a point is in a polygon. */ static int -lseg_crossing(double x, double y, double px, double py) +lseg_crossing(double x, double y, double prev_x, double prev_y) { double z; - int sgn; - - /* If (px,py) = (0,0) and not first call we have already sent HIT_IT */ + int y_sign; if (FPzero(y)) - { - if (FPzero(x)) - { - return HIT_IT; - - } + { /* y == 0, on X axis */ + if (FPzero(x)) /* (x,y) is (0,0)? */ + return POINT_ON_POLYGON; else if (FPgt(x, 0)) - { - if (FPzero(py)) - return FPgt(px, 0) ? 0 : HIT_IT; - return FPlt(py, 0) ? 1 : -1; - + { /* x > 0 */ + if (FPzero(prev_y)) /* y and prev_y are zero */ + /* prev_x > 0? */ + return FPgt(prev_x, 0) ? 0 : POINT_ON_POLYGON; + return FPlt(prev_y, 0) ? 1 : -1; } else - { /* x < 0 */ - if (FPzero(py)) - return FPlt(px, 0) ? 0 : HIT_IT; + { /* x < 0, x not on positive X axis */ + if (FPzero(prev_y)) + /* prev_x < 0? */ + return FPlt(prev_x, 0) ? 0 : POINT_ON_POLYGON; return 0; } } - - /* Now we know y != 0; set sgn to sign of y */ - sgn = (FPgt(y, 0) ? 1 : -1); - if (FPzero(py)) - return FPlt(px, 0) ? 0 : sgn; - - if (FPgt((sgn * py), 0)) - { /* y and py have same sign */ - return 0; - - } else - { /* y and py have opposite signs */ - if (FPge(x, 0) && FPgt(px, 0)) - return 2 * sgn; - if (FPlt(x, 0) && FPle(px, 0)) - return 0; - - z = (x - px) * y - (y - py) * x; - if (FPzero(z)) - return HIT_IT; - return FPgt((sgn * z), 0) ? 0 : 2 * sgn; + { /* y != 0 */ + /* compute y crossing direction from previous point */ + y_sign = FPgt(y, 0) ? 1 : -1; + + if (FPzero(prev_y)) + /* previous point was on X axis, so new point is either off or on */ + return FPlt(prev_x, 0) ? 0 : y_sign; + else if (FPgt(y_sign * prev_y, 0)) + /* both above or below X axis */ + return 0; /* same sign */ + else + { /* y and prev_y cross X-axis */ + if (FPge(x, 0) && FPgt(prev_x, 0)) + /* both non-negative so cross positive X-axis */ + return 2 * y_sign; + if (FPlt(x, 0) && FPle(prev_x, 0)) + /* both non-positive so do not cross positive X-axis */ + return 0; + + /* x and y cross axises, see URL above point_inside() */ + z = (x - prev_x) * y - (y - prev_y) * x; + if (FPzero(z)) + return POINT_ON_POLYGON; + return FPgt((y_sign * z), 0) ? 0 : 2 * y_sign; + } } } -- 2.40.0