org.erights.e.elib.vat
Class HeadlessRunner

java.lang.Object
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  +--org.erights.e.elib.vat.Runner
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        +--org.erights.e.elib.vat.HeadlessRunner

All Implemented Interfaces:

Runnable

final class HeadlessRunner

extends Runner

implements Runnable

A redirectable Runner, mostly for internal use.

Author:

Mark S. Miller, Many improvements due to suggestions by E-Dean Tribble

Field Summary

private static int	DEQUEUE_GRANULARITY The number of Runnables to dequeue and run in one go.
private FlexSet	myDeadManSwitches The DeadManSwitches I need to inform if I shutdown.
private SynchQueue	myOptQ Where PendingEvents are to be enqueued, or null if I've been redirected.
private Runner	myOptTarget The Runner that this Runner has been redirected to, or null if this Runner is fresh.
private RunnerThread	myOptThread The RunnerThread servicing this Runner's queue.
private Object	myQLock myOptQ's internal lock.

Fields inherited from class org.erights.e.elib.vat.Runner

myOptServingVat, myServingTicket

Constructor Summary

(package private)

HeadlessRunner(String optName) Makes a Vat, and starts the thread that services its queue.

Method Summary

(package private) void	addDeadManSwitch(Object deadManSwitch) Remember the deadManSwitch, so that if I'm shut down, I can notify him.
(package private) void	disturbEvent(Throwable t) Performs a Thread.stop(t) on the thread executing the current event.
protected Throwable	enqueue(PendingEvent todo) Add todo to the queue my thread is servicing
(package private) String	getRunnerKind() What kind of Runner is this?
(package private) boolean	isCurrent() Is the current thread this Runner's thread (the thread servicing this Vat)?
(package private) Runner	redirect(Runner newRunner) If the enabling conditions are met, then requeue all my events onto newRunner's queue, and remember to redirect all further requests to newRunner.
void	run() Called only by Thread.start().
(package private) void	setPriority(int newPriority) Requests a change of priority of the thread servicing this Runner.
(package private) Runner	shorten() If x.shorten() != x, then this Runner is no more, and should not be used.
String	toString() Suppressed: Returns a string representation of the object.

Methods inherited from class org.erights.e.elib.vat.Runner

getCurrentRunner, getOptCurrentRunner, getOptEStack, getOptServingVat, obtainRunner, obtainRunner, popEStackItem, pushEStackItem, requireCurrent, servingTicket

Methods inherited from class java.lang.Object

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

Field Detail

DEQUEUE_GRANULARITY

private static final int DEQUEUE_GRANULARITY

The number of Runnables to dequeue and run in one go. Must be >= 1.

myOptThread

private transient RunnerThread myOptThread

The RunnerThread servicing this Runner's queue.

If we ever go orthogonal again, myOptThread must not be checkpointed. Ie, it must be a DISALLOWED_FIELD or 'transient' or something.

myOptTarget

private Runner myOptTarget

The Runner that this Runner has been redirected to, or null if this Runner is fresh.

myOptQ

private SynchQueue myOptQ

Where PendingEvents are to be enqueued, or null if I've been redirected.

Note that SynchQueue is a thread-safe data structure with its own lock which we hold in myQLock.

myQLock

private final Object myQLock

myOptQ's internal lock.

myDeadManSwitches

private FlexSet myDeadManSwitches

The DeadManSwitches I need to inform if I shutdown.

Constructor Detail

HeadlessRunner

HeadlessRunner(String optName)

Makes a Vat, and starts the thread that services its queue.

Parameters:

optName - is the name to give to the created thread.

Method Detail

toString

public String toString()

Description copied from class: Object

Suppressed: Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

 getClass().getName() + '@' + Integer.toHexString(hashCode())
 

Overrides:

toString in class Object

Returns:

a string representation of the object.

shorten

Runner shorten()

Description copied from class: Runner

If x.shorten() != x, then this Runner is no more, and should not be used. This can happen only to HeadlessRunners.

Overrides:

shorten in class Runner

Returns:

The best Runner to use in lieu of me

getRunnerKind

String getRunnerKind()

Description copied from class: Runner

What kind of Runner is this?

A kind of Runner determines which kind of "devices" (eg, AWT or SWT widgets) may be synchronously accessed from within this Runner

Specified by:

getRunnerKind in class Runner

Returns:

"headless"

enqueue

protected Throwable enqueue(PendingEvent todo)

Description copied from class: Runner

Add todo to the queue my thread is servicing

Specified by:

enqueue in class Runner

setPriority

void setPriority(int newPriority)

Description copied from class: Runner

Requests a change of priority of the thread servicing this Runner.

Specified by:

setPriority in class Runner

disturbEvent

void disturbEvent(Throwable t)

Description copied from class: Runner

Performs a Thread.stop(t) on the thread executing the current event.

Note that Thread.stop() does not stop the thread (obvious huh?), but rather causes that thread to experience a "spontaneously" thrown exception.

Specified by:

disturbEvent in class Runner

isCurrent

boolean isCurrent()

Description copied from class: Runner

Is the current thread this Runner's thread (the thread servicing this Vat)?

If it is, we say we are executing inside this Runner.

r.isCurrent() implies Runner.getCurrentRunner() == r.

Specified by:

isCurrent in class Runner

run

public void run()

Called only by Thread.start().

(XXX It's a modularity bug for this to be public.) Pulls PendingEvents from the queue until there aren't any more, then waits until there's more to do.

Specified by:

run in interface Runnable

See Also:

java.lang.Thread#run()

redirect

Runner redirect(Runner newRunner)

If the enabling conditions are met, then requeue all my events onto newRunner's queue, and remember to redirect all further requests to newRunner.

The enabling conditions are

• This Runner isn't already redirected.
• newRunner isn't already redirected to this Runner. (If it is, we throw a ViciousCycleException.)

XXX Should we instead have an operation that only requeues the events queued by a given Vat, allowing Vats to migrate rather than merge?

addDeadManSwitch

void addDeadManSwitch(Object deadManSwitch)

Description copied from class: Runner

Remember the deadManSwitch, so that if I'm shut down, I can notify him.

The deadManSwitch is only notified if it's be a boot-ref (a Ref handled by a BootRefHandler whose target's vat is a vat handled by a different Runner. Otherwise, the notification would need to occur in this Runner, which is presumably already shut down.

Specified by:

addDeadManSwitch in class Runner