RiderControls.java

// PART OF THE MACHINE SIMULATION. DO NOT CHANGE.

package nachos.machine;

/**
 * A set of controls that can be used by a rider controller. Each rider uses a
 * distinct <tt>RiderControls</tt> object.
 */
public interface RiderControls {
    /**
     * Return the number of floors in the elevator bank. If <i>n</i> is the
     * number of floors in the bank, then the floors are numbered <i>0</i>
     * (the ground floor) through <i>n - 1</i> (the top floor).
     *
     * @return	the number of floors in the bank.
     */
    public int getNumFloors();

    /**
     * Return the number of elevators in the elevator bank. If <i>n</i> is the
     * number of elevators in the bank, then the elevators are numbered
     * <i>0</i> through <i>n - 1</i>.
     *
     * @return	the numbe rof elevators in the bank.
     */
    public int getNumElevators();

    /**
     * Set the rider's interrupt handler. This handler will be called when the
     * rider observes an event.
     *
     * @param	handler	the rider's interrupt handler.
     */
    public void setInterruptHandler(Runnable handler);

    /**
     * Return the current location of the rider. If the rider is in motion,
     * the returned value will be within one of the exact location.
     *
     * @return	the floor the rider is on.
     */
    public int getFloor();

    /**
     * Return an array specifying the sequence of floors at which this rider
     * has successfully exited an elevator. This array naturally does not
     * count the floor the rider started on, nor does it count floors where
     * the rider is in the elevator and does not exit.
     *
     * @return	an array specifying the floors this rider has visited.
     */
    public int[] getFloors();

    /**
     * Return the indicated direction of the specified elevator, set by
     * <tt>ElevatorControls.setDirectionDisplay()</tt>.
     *
     * @param	elevator	the elevator to check the direction of.
     * @return	the displayed direction for the elevator.
     *
     * @see	nachos.machine.ElevatorControls#setDirectionDisplay
     */
    public int getDirectionDisplay(int elevator);

    /**
     * Press a direction button. If <tt>up</tt> is <tt>true</tt>, invoke
     * <tt>pressUpButton()</tt>; otherwise, invoke <tt>pressDownButton()</tt>.
     *
     * @param	up	<tt>true</tt> to press the up button, <tt>false</tt> to
     *			press the down button.
     * @return	the return value of <tt>pressUpButton()</tt> or of
     *		<tt>pressDownButton()</tt>.
     */
    public boolean pressDirectionButton(boolean up);

    /**
     * Press the up button. The rider must not be on the top floor and must not
     * be inside an elevator. If an elevator is on the same floor as this
     * rider, has the doors open, and says it is going up, does nothing and
     * returns <tt>false</tt>.
     *
     * @return	<tt>true</tt> if the button event was sent to the elevator
     *		controller.
     */
    public boolean pressUpButton();

    /**
     * Press the down button. The rider must not be on the bottom floor and
     * must not be inside an elevator. If an elevator is on the same floor as
     * as this rider, has the doors open, and says it is going down, does
     * nothing and returns <tt>false</tt>.
     *
     * @return	<tt>true</tt> if the button event was sent to the elevator
     *		controller.
     */
    public boolean pressDownButton();

    /**
     * Enter an elevator. A rider cannot enter an elevator if its doors are not
     * open at the same floor, or if the elevator is full. The rider must not
     * already be in an elevator.
     *
     * @param	elevator	the elevator to enter.
     * @return	<tt>true</tt> if the rider successfully entered the elevator.
     */
    public boolean enterElevator(int elevator);

    /**
     * Press a floor button. The rider must be inside an elevator. If the
     * elevator already has its doors open on <tt>floor</tt>, does nothing and
     * returns <tt>false</tt>.
     *
     * @param	floor	the button to press.
     * @return	<tt>true</tt> if the button event was sent to the elevator
     *		controller.
     */
    public boolean pressFloorButton(int floor);

    /**
     * Exit the elevator. A rider cannot exit the elevator if its doors are not
     * open on the requested floor. The rider must already be in an elevator.
     *
     * @param	floor	the floor to exit on.
     * @return	<tt>true</tt> if the rider successfully got off the elevator.
     */
    public boolean exitElevator(int floor);

    /**
     * Call when the rider is finished.
     */
    public void finish();

    /**
     * Return the next event in the event queue. Note that there may be
     * multiple events pending when a rider interrupt occurs, so this
     * method should be called repeatedly until it returns <tt>null</tt>.
     *
     * @return	the next event, or <tt>null</tt> if no further events are
     * currently pending.
     */
    public RiderEvent getNextEvent();
}