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/* ----------------------------------------------------------------<Prolog>-
Name: sflmath.c
Title: Mathematic functions
Package: Standard Function Library (SFL)
Written: 1996/05/13 iMatix SFL project team <sfl@imatix.com>
Revised: 1997/09/08
Copyright: Copyright (c) 1996-2000 iMatix Corporation
This code was adapted from the NCSA HTTPd Server.
License: This is free software; you can redistribute it and/or modify
it under the terms of the SFL License Agreement as provided
in the file LICENSE.TXT. This software is distributed in
the hope that it will be useful, but without any warranty.
------------------------------------------------------------------</Prolog>-*/
#include "prelude.h" /* Universal header file */
#include "sflmath.h" /* Function prototypes */
/* ---------------------------------------------------------------------[<]-
Function: point_in_rect
Synopsis: Checks if the requested FPOINT is within the specified
rectangle. Returns TRUE or FALSE appropriately.
---------------------------------------------------------------------[>]-*/
int
point_in_rect (const FPOINT *point, const FPOINT *coords)
{
return ((point-> x >= coords [0].x && point-> x <= coords [1].x)
&& (point-> y >= coords [0].y && point-> y <= coords [1].y));
}
/* ---------------------------------------------------------------------[<]-
Function: point_in_circle
Synopsis: Checks if the requested FPOINT is within the specified
circle. Returns TRUE or FALSE appropriately.
---------------------------------------------------------------------[>]-*/
int
point_in_circle (const FPOINT *point, const FPOINT *coords)
{
double
circle_radius,
distance_from_centre;
circle_radius = ((coords [0].y - coords [1].y) *
(coords [0].y - coords [1].y)) +
((coords [0].x - coords [1].x) *
(coords [0].x - coords [1].x));
distance_from_centre = ((coords [0].y - point-> y) *
(coords [0].y - point-> y)) +
((coords [0].x - point-> x) *
(coords [0].x - point-> x));
return (distance_from_centre <= circle_radius);
}
/* ---------------------------------------------------------------------[<]-
Function: point_in_poly
Synopsis: Checks if the requested FPOINT is within the specified
polygon. Returns TRUE or FALSE.
---------------------------------------------------------------------[>]-*/
int
point_in_poly (const FPOINT *point, const FPOINT *pgon, int nbpoints)
{
int
inside_flag,
xflag0,
crossings;
const double
*stop;
double
*p,
tx,
ty,
y;
crossings = 0;
tx = point-> x;
ty = point-> y;
y = pgon [nbpoints - 1].y;
p = (double *) pgon + 1;
if ((y >= ty) != (*p >= ty))
{
if ((xflag0 = (pgon [nbpoints - 1].x >= tx)) ==
(*(double *) pgon >= tx))
{
if (xflag0)
crossings++;
}
else
crossings += (pgon [nbpoints - 1].x - (y - ty) *
(*(double *) pgon - pgon [nbpoints - 1].x) /
(*p - y)) >= tx;
}
stop = &pgon [nbpoints].y;
for (y = *p, p += 2; p <= stop; y = *p, p += 2)
{
if (y >= ty)
{
while ((p < stop) && (*p >= ty))
p += 2;
if (p >= stop)
break;
if ((xflag0 = (*(p - 3) >= tx)) == (*(p - 1) >= tx))
{
if (xflag0)
crossings++;
}
else
crossings += (*(p - 3) - (*(p - 2) - ty) *
(*(p - 1) - *(p - 3)) /
(*p - *(p - 2))) >= tx;
}
else
{
while ((p < stop) && (*p < ty))
p += 2;
if (p >= stop)
break;
if ((xflag0 = (*(p - 3) >= tx)) == (*(p - 1) >= tx))
{
if (xflag0)
crossings++;
}
else
crossings += (*(p - 3) - (*(p - 2) - ty) *
(*(p - 1) - *(p - 3)) /
(*p - *(p - 2))) >= tx;
}
}
inside_flag = crossings & 0x01;
return (inside_flag);
}

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