Package com.cosylab.epics.caj.util

Class SearchTimer

java.lang.Object

java.lang.Thread

com.cosylab.epics.caj.util.SearchTimer

All Implemented Interfaces:

Runnable

public class SearchTimer
extends Thread

Timer. Based on EDU.oswego.cs.dl.util.concurrent. Timer tasks should complete quickly. If a timer task takes excessive time to complete, it "hogs" the timer's task execution thread. This can, in turn, delay the execution of subsequent tasks, which may "bunch up" and execute in rapid succession when (and if) the offending task finally completes.

Version:

$id$

Author:

Matej Sekoranja

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
protected class	SearchTimer.RunLoop	The run loop is isolated in its own Runnable class just so that the main class need not implement Runnable, which would allow others to directly invoke run, which is not supported.
static class	SearchTimer.TimerTask

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

Thread.State, Thread.UncaughtExceptionHandler

Field Summary

Fields

Modifier and Type	Field	Description
protected PriorityBlockingQueue<SearchTimer.TimerTask>	heap	Tasks are maintained in a standard priority queue.
protected SearchTimer.RunLoop	runLoop
protected Thread	thread	The thread used to process commands

Fields inherited from class java.lang.Thread

MAX_PRIORITY, MIN_PRIORITY, NORM_PRIORITY

Constructor Summary

Constructors

Constructor	Description
SearchTimer()	Protected constructor (singleton pattern).

Method Summary

Modifier and Type	Method	Description
static void	cancel(Object taskID)	Cancel a scheduled task that has not yet been run.
protected void	clearThread()	set thread to null to indicate termination
void	executeAfterDelay(long millisecondsToDelay, SearchTimer.TimerTask task)	Execute the given command after waiting for the given delay.
Thread	getThread()
boolean	hasNext(long dT)	Check whether there is a task scheduled in next "dT" ms.
protected SearchTimer.TimerTask	nextTask(boolean blockAndExtract, long dt)	Return the next task to execute, or null if thread is interrupted.
void	rescheduleAllAfterDelay(long millisecondsToDelay)
void	restart()	Start (or restart) a thread to process commands, or wake up an existing thread if one is already running.
void	shutDown()	Cancel all tasks and interrupt the background thread executing the current task, if any.

Methods inherited from class java.lang.Thread

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

Methods inherited from class java.lang.Object

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

Field Detail

heap

protected final PriorityBlockingQueue<SearchTimer.TimerTask> heap

Tasks are maintained in a standard priority queue.

runLoop

protected final SearchTimer.RunLoop runLoop

thread

protected Thread thread

The thread used to process commands

Constructor Detail

SearchTimer

public SearchTimer()

Protected constructor (singleton pattern).

Method Detail

executeAfterDelay

public void executeAfterDelay(long millisecondsToDelay,
                              SearchTimer.TimerTask task)

Execute the given command after waiting for the given delay.

Parameters:

millisecondsToDelay - -- the number of milliseconds from now to run the command.

task - -- the command to run after the delay.

rescheduleAllAfterDelay

public void rescheduleAllAfterDelay(long millisecondsToDelay)

cancel

public static void cancel(Object taskID)

Cancel a scheduled task that has not yet been run. The task will be cancelled upon the next opportunity to run it. This has no effect if this is a one-shot task that has already executed. Also, if an execution is in progress, it will complete normally. (It may however be interrupted via getThread().interrupt()). But if it is a periodic task, future iterations are cancelled.

Parameters:

taskID - -- a task reference returned by one of the execute commands

Throws:

ClassCastException - if the taskID argument is not of the type returned by an execute command.

getThread

public Thread getThread()

clearThread

protected void clearThread()

set thread to null to indicate termination

restart

public void restart()

Start (or restart) a thread to process commands, or wake up an existing thread if one is already running. This method can be invoked if the background thread crashed due to an unrecoverable exception in an executed command.

shutDown

public void shutDown()

Cancel all tasks and interrupt the background thread executing the current task, if any. A new background thread will be started if new execution requests are encountered. If the currently executing task does not respond to interrupts, the current thread may persist, even if a new thread is started via restart().

nextTask

protected SearchTimer.TimerTask nextTask(boolean blockAndExtract,
                                         long dt)

Return the next task to execute, or null if thread is interrupted.

hasNext

public boolean hasNext(long dT)

Check whether there is a task scheduled in next "dT" ms.

Parameters:

dT - period in ms to check

Returns:

true if a task is scheduled within dT ms