*/

#include <SDL/SDL.h>

#define max(a,b) (((a) > (b)) ? (a) : (b))

#define min(a,b) (((a) < (b)) ? (a) : (b))

#define abs(a) (((a)<0) ? -(a) : (a))

#define sign(a) (((a)<0) ? -1 : (a)>0 ? 1 : 0)

void drawLine (SDL_Surface * s, int x1, int y1, int x2, int y2, Uint32 color)

{

    int d;

    int x;

    int y;

    int ax;

    int ay;

    int sx;

    int sy;

    int dx;

    int dy;

    Uint8 *lineAddr;

    Sint32 yOffset;

    dx = x2 - x1;

    ax = abs (dx) << 1;

    sx = sign (dx);

    dy = y2 - y1;

    ay = abs (dy) << 1;

    sy = sign (dy);

    yOffset = sy * s->pitch;

    x = x1;

    y = y1;

    lineAddr = ((Uint8 *) s->pixels) + (y * s->pitch);

    if (ax > ay) {              /* x dominant */

        d = ay - (ax >> 1);

        for (;;) {

            *((Uint16 *) (lineAddr + (x << 1))) = (Uint16) color;

            if (x == x2) {

                return;

            }

            if (d >= 0) {

                y += sy;

                lineAddr += yOffset;

                d -= ax;

            }

            x += sx;

            d += ay;

        }

    } else {                    /* y dominant */

        d = ax - (ay >> 1);

        for (;;) {

            *((Uint16 *) (lineAddr + (x << 1))) = (Uint16) color;

            if (y == y2) {

                return;

            }

            if (d >= 0) {

                x += sx;

                d -= ay;

            }

            y += sy;

            lineAddr += yOffset;

            d += ax;

        }

    }

}