cae-tools/poly2d/poly2d.h

/*
 * poly2d.h - The public face of the 2D Polygon library
 *
 * Written 2012 by Werner Almesberger
 * Copyright 2012 Werner Almesberger
 *
 * This program 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.
 */


#ifndef POLY2D_H
#define POLY2D_H

#include <stdio.h>


struct v2d {
	double x, y;
	struct v2d *next; /* may end in NULL or may be cyclic */
};


struct p2d {
	struct v2d *v;	/* vertices */
	struct v2d *last;	/* last vertex or vertex preceding first */
	struct p2d *next;
};


/*
 * forall_v2d* need -std=gnu99
 */

#define	forall_v2d_once(var, first)					\
	for (const struct v2d *__fv2do_0 = (var = (first));		\
	    var;							\
	    var = var->next == __fv2do_0 ? NULL : var->next)

#define	forall_v2d(var, first)						\
	for (const struct v2d *__fv2d_0 = (var = (first));		\
	    var;							\
	    ({								\
		var = __fv2d_0 ? var->next : NULL;			\
		if (var == __fv2d_0)					\
			__fv2d_0 = NULL;				\
	    }))

#define	forall_edges(a, b, first)					\
	for (const struct v2d *__fe_0 =					\
	   (a = (first), b = a ? a->next : a, a);			\
	    a && b;							\
	    ({								\
		a = b;							\
		b = b == __fe_0 ? NULL : b->next;			\
	    }))


/*
 * Polygon creation
 */

struct p2d *p2d_new(void);
struct v2d *v2d_new(double x, double y);
void p2d_append(struct p2d *p, struct v2d *v);
void p2d_prepend(struct p2d *p, struct v2d *v);
void p2d_close(struct p2d *p);

/*
 * Intersect line from A0 to A1 with line from B0 to B1.
 *
 * Returns:
 *   0  if the lines are parallel,
 *   1  if the lines intersect between A0-A1 and B0-B1,
 *  -1  if the lines intersect outside A0-A1 or B0-B1.
 *
 * If v2d_intersect returns non-zero, the intersection P is at
 *
 * P = A0+(A1-A0)*na = B0+(B1-B0)*nb
 */

int v2d_intersect(const struct v2d *a0, const struct v2d *a1,
    const struct v2d *b0, const struct v2d *b1,
    double *na, double *nb);

/*
 * Calculate the distance between point P and the line from A to B.
 * The result is negative if P is on the "right" side of A->B.
 */

double v2d_line_distance(const struct v2d *a, const struct v2d *b,
    const struct v2d *p);

/*
 * Duplicate a polygon
 */

struct p2d *p2d_copy(const struct p2d *p);
struct p2d *p2d_copy_all(const struct p2d *p);

/*
 * Change a polygon from clockwise to counter-clockwise and vice versa.
 */

struct p2d *p2d_reverse(const struct p2d *p);

/*
 * p2d_is_cw determine whether a polygon is clockwise.
 * p2d_is_closed determines whether a polygon is closed.
 * p2d_no_intersect determines whether a polygon does't self-intersect.
 * p2d_vertices counts the number of vertices in a polygon.
 */

int p2d_is_cw(const struct p2d *p);
int p2d_is_closed(const struct p2d *p);
int p2d_no_intersect(const struct p2d *p);
int p2d_vertices(const struct p2d *p);

/*
 * Convert a possibly self-intersecting polygon into one or more simple
 * polygons. [1]
 *
 * http://en.wikipedia.org/wiki/Simple_polygon
 */

struct p2d *p2d_simplify(const struct p2d *p);

/*
 * p2d_free deallocates a single polygon and its vertices.
 * p2d_free_all deallocates all polygons in a list.
 */

void p2d_free(struct p2d *p);
void p2d_free_all(struct p2d *p);

/*
 * Returns non-zero if the point is inside or on the simple polygon.
 */

int p2d_contains_point(const struct p2d *p, const struct v2d *v);

/*
 * Returns:
 *   0 if polygon "b" is outside of polygon "a"
 *   1 if polygon "b" is inside of polygon "a"
 *  -1 if the two polygons intersect
 */

int p2d_contains_poly(const struct p2d *a, const struct p2d *b);

struct p2d *p2d_offset_holes(const struct p2d *p, const struct p2d *holes,
    double off);
struct p2d *p2d_offset(const struct p2d *p, double off);

void p2d_area_holes_append(const struct p2d *p,
    const struct p2d *holes, double first, double next,
    struct p2d ***last);
struct p2d *p2d_area_holes(const struct p2d *p, const struct p2d *holes,
    double first, double next);
struct p2d *p2d_area(const struct p2d *p, double first, double next);

struct p2d *p2d_read_gnuplot(FILE *file);
int p2d_write_gnuplot(FILE *file, const struct p2d *p);
int p2d_write_gnuplot_all(FILE *file, const struct p2d *p);

#endif /* !POLY2D_H */