Class Device

java.lang.Object
  |
  +--Device

Direct Known Subclasses:

CPU, JobArrival

class Device

extends java.lang.Object

A Device can be running or stopped. Once started, it will "interrupt" at some time in the future. Since this is a simulation, interrupts are a bit funny: Each device indicates the simulation time when the interrupt will occur and Sim.mainLoop() polls the devices, see which one is next to interrupt. It then advances its current time to the time of the interrupt, stops the device, and does what the "interrupt handler" for the device would do. In the current version of the simulation, the disk, clock, and cpu devices are all instances of Device. Job arrivals are represented by a pseudo-device JobArrival, which extends Device.

See Also:

JobArrival, Sim#mainLoop()

Field Summary

private Job	currentJob The current job, if running.
private java.lang.String	name The name of the device (for diagnostic output)
private int	nextInterruptTime When will it next interrupt? (MAX_VALUE if not running)
private boolean	running Is the device currently running?
private int	startedAt When did it last start running? (meaningless if not running)
private int	totalTime What is the total amount of time it has been running?
private java.util.Vector	trace Trace of significant events in this device's lifetime (only if Sim.traceFlag)

Constructor Summary

(package private)

Device(java.lang.String name) Initialize the Device.

Method Summary

Job	current() Get the current job.
boolean	isBusy() Is the device currently runing?
int	nextInterrupt() Retrieve the time when the next interrupt will occur.
void	printStats() Print information about this device
void	start(Job j, int amt) Start a device running, servicing a job.
Job	stop() Stop the device.
java.lang.String	toString() For debugging, information about this device.

Methods inherited from class java.lang.Object

, clone, equals, finalize, getClass, hashCode, notify, notifyAll, registerNatives, wait, wait, wait

Field Detail

name

private java.lang.String name

The name of the device (for diagnostic output)

trace

private java.util.Vector trace

Trace of significant events in this device's lifetime (only if Sim.traceFlag)

running

private boolean running

Is the device currently running?

currentJob

private Job currentJob

The current job, if running.

nextInterruptTime

private int nextInterruptTime

When will it next interrupt? (MAX_VALUE if not running)

startedAt

private int startedAt

When did it last start running? (meaningless if not running)

totalTime

private int totalTime

What is the total amount of time it has been running?

Constructor Detail

Device

Device(java.lang.String name)

Initialize the Device.

Parameters:

name - the name of the device.

Method Detail

current

public Job current()

Get the current job.

Returns:

the current job (null if device is idle)

toString

public java.lang.String toString()

For debugging, information about this device.

Overrides:

toString in class java.lang.Object

Returns:

the name of this device.

start

public void start(Job j,
                  int amt)

Start a device running, servicing a job.

Parameters:

j - the job to run

amt - for generic devices, the amount of time to run the job, in milliseconds. Specific devices may interpret the argument differently.

stop

public Job stop()

Stop the device.

Returns:

the job that was being serviced by the device.

nextInterrupt

public final int nextInterrupt()

Retrieve the time when the next interrupt will occur.

Returns:

the time of the completion interrupt (-1 if not running).

isBusy

public boolean isBusy()

Is the device currently runing?

Returns:

true if the device is running .

printStats

public void printStats()

Print information about this device