/* line2.c - two different implementations of a line drawing function */
#include <stdio.h>
#include <stdlib.h>

/* this version profiles slightly better than line1() */
#define SWAP(a,b) { (a)^=(b); (b)^=(a); (a)^=(b); } 
static void line2(int w, char d[][w], char c, int x, int y, int x2, int y2) {
	int dx, dy, p;
	dx=2*abs(x2-x);
	dy=2*abs(y2-y);
	if(dx>dy) {
		if(x>x2) {
			SWAP(x,x2);
			SWAP(y,y2);
		}
		p=dy-dx;
		if(y<y2) {
			/* long X slope going down */
			while(x!=x2) {
				d[y][x]=c;
				if(p>=0) {
					y++;
					p-=dx;
				}
				x++;
				p+=dy;
			}
		} else {
			/* long X slope going up */
			while(x!=x2) {
				d[y][x]=c;
				if(p>=0) {
					y--;
					p-=dx;
				}
				x++;
				p+=dy;
			}
		}
	} else {
		if(y>y2) {
			SWAP(x,x2);
			SWAP(y,y2);
		}
		p=dx-dy;
		if(x<x2) {
			/* long Y slope going right */
			while(y!=y2) {
				d[y][x]=c;
				if(p>=0) {
					x++;
					p-=dy;
				}
				y++;
				p+=dx;
			}
		} else {
			/* long Y slope going left */
			while(y!=y2) {
				d[y][x]=c;
				if(p>=0) {
					x--;
					p-=dy;
				}
				y++;
				p+=dx;
			}
		}
	}
}

static void line1(int w, char d[][w], char c, int x, int y, int x2, int y2) {
    int ddx, ddy;
    int sx, sy;
    ddx=2*abs(x2-x);
    ddy=2*abs(y2-y);
    sx = (x2<x) ? -1 : (x2>x) ? 1 : 0;
    sy = (y2<y) ? -1 : (y2>y) ? 1 : 0;
    if(ddx>=ddy) {
        int ydp;
        ydp=ddy-ddx;
        while(d[y][x]=c, x!=x2) {
            if(ydp>=0) {
                y+=sy;
                ydp-=ddx;
            }
            x+=sx;
            ydp+=ddy;
        }
    } else {
        int xdp;
        xdp=ddx-ddy;
        while(d[y][x]=c, y!=y2) {
            if(xdp>=0) {
                x+=sx;
                xdp-=ddy;
            } 
            y+=sy;
            xdp+=ddx;
        }
    }
}

static void test1(int w, int h, int n) {
	char d[h][w];
	int x1, y1, x2, y2;
	do {
		for(x1=0;x1<w;x1++) {
			for(y1=0;y1<h;y1++) {
				for(x2=0;x2<w;x2++) {
					for(y2=0;y2<h;y2++) {
						line1(w, d, '@', x1, y1, x2, y2);
					}
				}
			}
		}
	} while(--n);
}

static void test2(int w, int h, int n) {
	char d[h][w];
	int x1, y1, x2, y2;
	do {
		for(x1=0;x1<w;x1++) {
			for(y1=0;y1<h;y1++) {
				for(x2=0;x2<w;x2++) {
					for(y2=0;y2<h;y2++) {
						line2(w, d, '@', x1, y1, x2, y2);
					}
				}
			}
		}
	} while(--n);
}

int main() {
	printf("Testing line2()\n");
	test2(20, 20, 1000);
	printf("Testing line1()\n");
	test1(20, 20, 1000);
	return 0;
}