StandardConsole.java

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

package nachos.machine;

import nachos.security.*;

import java.io.IOException;

/**
 * A text-based console that uses System.in and System.out.
 */
public class StandardConsole implements SerialConsole {
    /**
     * Allocate a new standard console.
     *
     * @param	privilege      	encapsulates privileged access to the Nachos
     *				machine.
     */
    public StandardConsole(Privilege privilege) {
	System.out.print(" console");

	this.privilege = privilege;

	receiveInterrupt = new Runnable() {
		public void run() { receiveInterrupt(); }
	    };

	sendInterrupt = new Runnable() {
		public void run() { sendInterrupt(); }
	    };		
	
	scheduleReceiveInterrupt();
    }
    
    public final void setInterruptHandlers(Runnable receiveInterruptHandler,
					   Runnable sendInterruptHandler) {
	this.receiveInterruptHandler = receiveInterruptHandler;
	this.sendInterruptHandler = sendInterruptHandler;
    }

    private void scheduleReceiveInterrupt() {
	privilege.interrupt.schedule(Stats.ConsoleTime, "console read",
				     receiveInterrupt);
    }

    /**
     * Attempt to read a byte from the object backing this console.
     *
     * @return	the byte read, or -1 of no data is available.
     */
    protected int in() {
	try {
	    if (System.in.available() <= 0)
		return -1;

	    return System.in.read();
	}
	catch (IOException e) {
	    return -1;
	}
    }

    private int translateCharacter(int c) {
	// translate win32 0x0D 0x0A sequence to single newline
	if (c == 0x0A && prevCarriageReturn) {
	    prevCarriageReturn = false;
	    return -1;
	}
	prevCarriageReturn = (c == 0x0D);
	
	// invalid if non-ASCII
	if (c >= 0x80)
	    return -1;
	// backspace characters
	else if (c == 0x04 || c == 0x08 || c == 0x19 || c == 0x1B || c == 0x7F)
	    return '\b';
	// if normal ASCII range, nothing to do
	else if (c >= 0x20)
	    return c;
	// newline characters
	else if (c == 0x0A || c == 0x0D)
	    return '\n';
	// everything else is invalid
	else
	    return -1;
    }


    private void receiveInterrupt() {
	Lib.assertTrue(incomingKey == -1);

	incomingKey = translateCharacter(in());
	if (incomingKey == -1) {
	    scheduleReceiveInterrupt();
	}
	else {
	    privilege.stats.numConsoleReads++;

	    if (receiveInterruptHandler != null)
		receiveInterruptHandler.run();
	}
    }

    public final int readByte() {
	int key = incomingKey;

	if (incomingKey != -1) {
	    incomingKey = -1;
	    scheduleReceiveInterrupt();
	}

	return key;
    }

    private void scheduleSendInterrupt() {
	privilege.interrupt.schedule(Stats.ConsoleTime, "console write",
				     sendInterrupt);
    }

    /**
     * Write a byte to the object backing this console.
     *
     * @param	value	the byte to write.
     */
    protected void out(int value) {
	System.out.write(value);
	System.out.flush();
    }	

    private void sendInterrupt() {
	Lib.assertTrue(outgoingKey != -1);

	out(outgoingKey);
	outgoingKey = -1;

	privilege.stats.numConsoleWrites++;

	if (sendInterruptHandler != null)
	    sendInterruptHandler.run();
    }

    public final void writeByte(int value) {
	if (outgoingKey == -1)
	    scheduleSendInterrupt();
	
	outgoingKey = value&0xFF;
    }

    private Privilege privilege = null;

    private Runnable receiveInterrupt;
    private Runnable sendInterrupt;

    private Runnable receiveInterruptHandler = null;
    private Runnable sendInterruptHandler = null;

    private int incomingKey = -1;
    private int outgoingKey = -1;

    private boolean prevCarriageReturn = false;
}