Something

void s_drawLine(int x0, int y0, int x1, int y1, uint16 color)
{
	int dy = y1 - y0;
	int dx = x1 - x0;
	int stepx, stepy;

	if (dy < 0) { dy = -dy;  stepy = -1; } else { stepy = 1; }
	if (dx < 0) { dx = -dx;  stepx = -1; } else { stepx = 1; }
	dy <<= 1;                                                  // dy is now 2*dy
	dx <<= 1;                                                  // dx is now 2*dx

	s_setPixel(x0, y0, color);
	
	if (dx > dy) 
	{
		int fraction = dy - (dx >> 1);                         // same as 2*dy - dx
		while (x0 != x1) 
		{
			if (fraction >= 0) 
			{
				y0 += stepy;
				fraction -= dx;                                // same as fraction -= 2*dx
			}
			x0 += stepx;
			fraction += dy;                                    // same as fraction -= 2*dy
			s_setPixel(x0, y0, color);
		}
	} 
	else 
	{
		int fraction = dx - (dy >> 1);
		while (y0 != y1) 
		{
			if (fraction >= 0) 
			{
				x0 += stepx;
				fraction -= dy;
			}
			y0 += stepy;
			fraction += dx;
			s_setPixel(x0, y0, color);
		}
	}
}