frysk.event
Class EventLoop

java.lang.Object
  java.lang.Thread
      frysk.event.EventLoop

All Implemented Interfaces:

Runnable

Direct Known Subclasses:

PollEventLoop, WaitEventLoop

public abstract class EventLoop
extends Thread

Implements an event loop.

Nested Class Summary

private class	EventLoop.ExecuteRequest
private class	EventLoop.Running Run the event-loop.

Nested classes/interfaces inherited from class java.lang.Thread

Thread.State, Thread.UncaughtExceptionHandler

Field Summary

private static Log	fine
private Exception	firstSet
private boolean	isGoingToBlock The event loop will enter a blocking poll.
private List	pendingEvents Maintain a FIFO of events that are ready to be processed.
private EventLoop.ExecuteRequest	request
private EventLoop.Running	running
private Map	signalHandlers Collection of signals; assume that very few signals are being watched and hence that a small map is sufficient.
private boolean	stop
private ProcessIdentifier	tid The EventLoop's thread ID.
private SortedMap	timerEvents List of timer events.

Fields inherited from class java.lang.Thread

MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY

Constructor Summary

protected

EventLoop() The EventLoop uses Signal.IO to wake up, or unblock, the event-loop thread when a request comes in.

Method Summary

void	add(Event e) Add the event to the end of the queue of events that need to be processed.
void	add(SignalEvent signalEvent) Add the signal handler, signals are processed and then delivered using the event-loop.
void	add(TimerEvent t) Add a timer event that will expire at some stage in the future.
abstract void	add(WaitBuilder waitBuilder) Add support for the notification of waitpid events.
protected abstract void	block(long millisecondTimeout) Block for up-to TIMEOUT, or until an event arrives, or possibly no-reason.
private void	checkForTimerEvents() Move any expired timer events onto the event queue.
void	execute(Event e) Execute the event on the event-loop thread; return when completed.
static EventLoop	factory() Return the current prefered flavour of the event-loop.
private long	getTimerEventMillisecondTimeout() Return the number of milliseconds until the next timer, or -1 if there is no pending timer (-1 implies an infinite timeout).
(package private) boolean	isCurrentThread()
protected void	processSignal(Signal sig) Process the signal.
private Event	remove() Remove and return the first pending event, or null if there are no pending event.
void	remove(Event e) Remove the pending event.
void	remove(SignalEvent signalEvent) Remove the signal event handler, further occurances of the signal are discarded.
void	remove(TimerEvent t) Remove the timer event from the event queue.
void	requestStop() Request that the event-loop stop.
void	run()
private void	runEventLoop(boolean pendingOnly) Run the event-loop.
void	runPending() Run the event loop until there are no pending events.
boolean	runPolling(long timeout) Run the full event loop (checking for both synchronous and asynchronous events) for at most TIMEOUT milliseconds.
protected abstract void	signalAdd(Signal sig) Add Signal to the signals that can be received.
protected abstract void	signalEmpty() Clear the signal set being used by the event-loop.
void	start() Start the EventLoop thread; note that this forces a brief synchronization with that thread to ensure that it is ready.
private void	updateTid()
private void	wakeupBlockedEventLoop()
private void	wakeupIfBlocked() If the event loop is blocking, wake it up.

Methods inherited from class java.lang.Thread

activeCount, checkAccess, countStackFrames, currentThread, destroy, dumpStack, enumerate, getAllStackTraces, getContextClassLoader, getDefaultUncaughtExceptionHandler, getId, getName, getPriority, getStackTrace, getState, getThreadGroup, getUncaughtExceptionHandler, holdsLock, interrupt, interrupted, isAlive, isDaemon, isInterrupted, join, join, join, resume, setContextClassLoader, setDaemon, setDefaultUncaughtExceptionHandler, setName, setPriority, setUncaughtExceptionHandler, sleep, sleep, stop, stop, suspend, toString, yield

Methods inherited from class java.lang.Object

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

Field Detail

fine

private static final Log fine

tid

private ProcessIdentifier tid

The EventLoop's thread ID. If a thread, other than the EventLoop thread modifies any of the event queues, the event thread will need to be woken up using a Signal.IO.

firstSet

private Exception firstSet

isGoingToBlock

private volatile boolean isGoingToBlock

The event loop will enter a blocking poll. This state is entered after the pending event queue, along with any other tasks (signals, timers), have been processed leaving the event thread with nothing to do. Should some new asynchronus task come along (such as a new event, timer, or signal handler), the event thread will need to be woken up.

timerEvents

private SortedMap timerEvents

List of timer events. Ordered by the timer's expiry time (that way the first timer event always determines the next timeout).

signalHandlers

private Map signalHandlers

Collection of signals; assume that very few signals are being watched and hence that a small map is sufficient.

pendingEvents

private List pendingEvents

Maintain a FIFO of events that are ready to be processed.

request

private final EventLoop.ExecuteRequest request

stop

private volatile boolean stop

running

private EventLoop.Running running

Constructor Detail

EventLoop

protected EventLoop()

The EventLoop uses Signal.IO to wake up, or unblock, the event-loop thread when a request comes in.

Method Detail

signalEmpty

protected abstract void signalEmpty()

Clear the signal set being used by the event-loop.

signalAdd

protected abstract void signalAdd(Signal sig)

Add Signal to the signals that can be received.

add

public abstract void add(WaitBuilder waitBuilder)

Add support for the notification of waitpid events.

block

protected abstract void block(long millisecondTimeout)

Block for up-to TIMEOUT, or until an event arrives, or possibly no-reason.

isCurrentThread

final boolean isCurrentThread()

wakeupBlockedEventLoop

private void wakeupBlockedEventLoop()

updateTid

private void updateTid()

wakeupIfBlocked

private void wakeupIfBlocked()

If the event loop is blocking, wake it up. The event loop blocks when it has nothing better to do (app pending events have been processed, all timers and signals have been handled). See remove() for where this flag is set.

add

public void add(TimerEvent t)

Add a timer event that will expire at some stage in the future. The actual time is determined by TimerEvent.getTimeMillis.

remove

public void remove(TimerEvent t)

Remove the timer event from the event queue.

getTimerEventMillisecondTimeout

private long getTimerEventMillisecondTimeout()

Return the number of milliseconds until the next timer, or -1 if there is no pending timer (-1 implies an infinite timeout).

checkForTimerEvents

private void checkForTimerEvents()

Move any expired timer events onto the event queue. Since the timer queue is ordered by time, the loop need only check the front of the queue.

add

public void add(SignalEvent signalEvent)

Add the signal handler, signals are processed and then delivered using the event-loop.

remove

public void remove(SignalEvent signalEvent)

Remove the signal event handler, further occurances of the signal are discarded.

processSignal

protected void processSignal(Signal sig)

Process the signal. Find the applicable handler and, if present, append the corresponding delivery event. Since a signal delivery un-blocks the poll, the event thread is no longer going to block.

add

public void add(Event e)

Add the event to the end of the queue of events that need to be processed. If necessary, interrupt the event thread.

remove

public void remove(Event e)

Remove the pending event.

execute

public void execute(Event e)

Execute the event on the event-loop thread; return when completed. If these requests are ongoing then consider creating a dedicated Request object.

remove

private Event remove()

Remove and return the first pending event, or null if there are no pending event. Also set the isGoingToBlock flag (after all with the event queue empty there is nothing better to do).

runEventLoop

private void runEventLoop(boolean pendingOnly)

Run the event-loop. If pendingOnly, stop after processing all pending events. The event loop is stopped by calling requestStop (that stops the event loop once all pending events have been processed). Any existing pending events are always processed before performing the first poll.

requestStop

public void requestStop()

Request that the event-loop stop. The event loop stops once all pending events have been processed. Can be called asynchronously.

runPending

public final void runPending()

Run the event loop until there are no pending events. Of course, if more events are appended to the pending queue, then they too are processed. For testing only. This method does not check for asynchronous events (Signals, Poll, Timers) is made. For that see runPolling.

runPolling

public final boolean runPolling(long timeout)

Run the full event loop (checking for both synchronous and asynchronous events) for at most TIMEOUT milliseconds. Return true if the event loop was stopped before the timer expired. For testing only. Should only be used thus: eventLoop.add<>Event (new <>Event () { public void execute () { eventLoop.stop (); }}); assertTrue ("Waiting for <>", eventLoop.runPolling (<>));

run

public final void run()

Specified by:

run in interface Runnable

Overrides:

run in class Thread

start

public void start()

Start the EventLoop thread; note that this forces a brief synchronization with that thread to ensure that it is ready.

Overrides:

start in class Thread

factory

public static EventLoop factory()

Return the current prefered flavour of the event-loop.