javax.realtime
Class PeriodicParameters

java.lang.Object
  javax.realtime.ReleaseParameters
      javax.realtime.PeriodicParameters

All Implemented Interfaces:

Cloneable

public class PeriodicParameters

extends ReleaseParameters

This release parameter indicates that the public boolean RealtimeThread.waitForNextPeriod() throws IllegalThreadStateException method on the associated Schedulable object will be unblocked at the start of each period. When a reference to a PeriodicParameters object is given as a parameter to a constructor the PeriodicParameters object becomes bound to the object being created. Changes to the values in the PeriodicParameters object affect the constructed object. If given to more than one constructor then changes to the values in the PeriodicParameters object affect all of the associated objects. Note that this is a one-to-many relationship and not a many-to-many.

Caution: This class is explicitly unsafe in multithreaded situations when it is being changed. No synchronization is done. It is assumed that users of this class who are mutating instances will be doing their own synchronization at a higher level.

Author:

Angelo Corsaro, Morgan Deters

Field Summary

protected RelativeTime	period
protected HighResolutionTime	start

Fields inherited from class javax.realtime.ReleaseParameters

cost, deadline, missHandler, overrunHandler

Constructor Summary

PeriodicParameters(HighResolutionTime start, RelativeTime period)
Creates a new PeriodicParameters instance.

PeriodicParameters(HighResolutionTime start, RelativeTime period, RelativeTime cost, RelativeTime deadline, AsyncEventHandler overrunHandler, AsyncEventHandler missHandler)
Creates a new PeriodicParameters instance.

PeriodicParameters(RelativeTime period)
Creates a new PeriodicParameters instance.

Method Summary

RelativeTime	getPeriod() Get the period value.
HighResolutionTime	getStart() Get the start time.
boolean	setIfFeasible(RelativeTime period, RelativeTime cost, RelativeTime deadline) Perform a feasibility analysis with the given replacement values.
void	setPeriod(RelativeTime period) Set the period value.
void	setStart(HighResolutionTime start) Set the start time.

Methods inherited from class javax.realtime.ReleaseParameters

clone, getCost, getCostOverrunHandler, getDeadline, getDeadlineMissHandler, setCost, setCostOverrunHandler, setDeadline, setDeadlineMissHandler, setIfFeasible

Methods inherited from class java.lang.Object

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

Field Detail

start

protected HighResolutionTime start

period

protected RelativeTime period

Constructor Detail

PeriodicParameters

public PeriodicParameters(HighResolutionTime start,
                          RelativeTime period)

Creates a new PeriodicParameters instance. This constructor has the same effect as invoking PeriodicParameters(start, period, null, null, null, null).

Parameters:

start - Time at which the first period begins. If a RelativeTime , this time is relative to the first time the schedulable object becomes schedulable (schedulable time) (e.g., when start() is called on a thread). If an AbsoluteTime and it is before the schedulable time, start is equivalent to the schedulable time.

period - The period is the interval between successive unblocks of RealtimeThread.waitForNextPeriod(). Must be greater than zero when entering feasibility analysis.

PeriodicParameters

public PeriodicParameters(HighResolutionTime start,
                          RelativeTime period,
                          RelativeTime cost,
                          RelativeTime deadline,
                          AsyncEventHandler overrunHandler,
                          AsyncEventHandler missHandler)

Creates a new PeriodicParameters instance.

Parameters:

start - Time at which the first period begins. If a RelativeTime , this time is relative to the first time the schedulable object becomes schedulable (schedulable time) (e.g., when start() is called on a thread). If an AbsoluteTime and it is before the schedulable time, start is equivalent to the schedulable time.

period - The period is the interval between successive unblocks of RealtimeThread.waitForNextPeriod(). Must be greater than zero when entering feasibility analysis.

cost - Processing time per period. On implementations which can measure the amount of time a schedulable object is executed, this value is the maximum amount of time a schedulable object receives per period. On implementations which cannot measure execution time, this value is used as a hint to the feasibility algorithm. On such systems it is not possible to determine when any particular object exceeds or will exceed cost time units in a period. Equivalent to RelativeTime(0,0) if null.

deadline - The latest permissible completion time measured from the release time of the associated invocation of the schedulable object. For a minimum implementation for purposes of feasibility analysis, the deadline is equal to the period. Other implementations may use this parameter to compute execution eligibility. If null, deadline will equal the period.

overrunHandler - This handler is invoked if an invocation of the schedulable object exceeds cost in the given period. Not required for minimum implementation. If null, nothing happens on the overrun condition.

missHandler - This handler is invoked if the Runnable.run() method of the schedulable object is still executing after the deadline has passed. Although minimum implementations do not consider deadlines in feasibility calculations, they must recognize variable deadlines and invoke the miss handler as appropriate. If null, nothing happens on the miss deadline condition.

PeriodicParameters

public PeriodicParameters(RelativeTime period)

Creates a new PeriodicParameters instance. This constructror has the same effect as invoking PeriodicParameters(null, period, null, null, null, null).

Parameters:

period - the period parameter

Method Detail

getPeriod

public RelativeTime getPeriod()

Get the period value.

Returns:

a RelativeTime representing the period value.

setPeriod

public void setPeriod(RelativeTime period)

Set the period value.

Parameters:

period - The period is the interval between successive unblocks of RealtimeThread.waitForNextPeriod(). Must be greater than zero when entering feasibility analysis.

getStart

public HighResolutionTime getStart()

Get the start time.

Returns:

a HighResolutionTime value

setStart

public void setStart(HighResolutionTime start)

Set the start time.

Parameters:

start - time at which the first period begins.

setIfFeasible

public boolean setIfFeasible(RelativeTime period,
                             RelativeTime cost,
                             RelativeTime deadline)

Perform a feasibility analysis with the given replacement values. If the resulting system is feasible, set these values and return true. Otherwise, change nothing and return false.

Parameters:

period - the suggested period

cost - the suggested cost

deadline - the suggested deadline

Returns:

true if the resulting system was feasible and changes were made; false otherwise.

Throws:

IllegalArgumentException - if period is null or nonpositive, if cost is negative, if deadline is nonpositive, or if values are incompatible with the current scheduler(s)

IllegalAssignmentError - if one or more of the arguments cannot be referred to by this; in this case, no changes are made, even for those parameters that can be stored in this