openfilewithposition.java

Nachos 5 java version

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

package nachos.machine;

/**
 * An <tt>OpenFile</tt> that maintains a current file position.
 */
public abstract class OpenFileWithPosition extends OpenFile {
    /**
     * Allocate a new <tt>OpenFileWithPosition</tt>.
     */
    public OpenFileWithPosition() {
    }

    public void seek(int position) {
	this.position = position;
    }

    public int tell() {
	return position;
    }

    public int read(byte[] buf, int offset, int length) {
	int amount = read(position, buf, offset, length);
	if (amount == -1)
	    return -1;
	
	position += amount;
	return amount;
    }

    public int write(byte[] buf, int offset, int length) {
	int amount = write(position, buf, offset, length);
	if (amount == -1)
	    return -1;
	
	position += amount;
	return amount;
    }

    /**
     * The current value of the file pointer.
     */
    protected int position = 0;
}