javax.realtime
Class AperiodicParameters

java.lang.Object
  javax.realtime.ReleaseParameters
      javax.realtime.AperiodicParameters

Direct Known Subclasses:

SporadicParameters

public class AperiodicParameters

extends ReleaseParameters

This release parameter object characterizes a schedulable object that may become active at any time. When a reference to a AperiodicParameters object is given as a parameter to a constructor the AperiodicParameters object becomes bound to the object being created. Changes to the values in the AperiodicParameters object affect the constructed object. If given to more than one constructor then changes to the values in the AperiodicParameters object affect all of the associated objects. Note that this is a one-to-many relationship and not a many-to-many.

Author:

Angelo Corsaro

Field Summary

Fields inherited from class javax.realtime.ReleaseParameters

cost, deadline, missHandler, overrunHandler

Constructor Summary

AperiodicParameters(RelativeTime cost, RelativeTime deadline, AsyncEventHandler overrunHandler, AsyncEventHandler missHandler)
Creates a new AperiodicParameters instance.

Method Summary

boolean

setIfFeasible(RelativeTime cost, RelativeTime deadline) Attempt to change the cost and deadline.

Methods inherited from class javax.realtime.ReleaseParameters

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

Methods inherited from class java.lang.Object

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

Constructor Detail

AperiodicParameters

public AperiodicParameters(RelativeTime cost,
                           RelativeTime deadline,
                           AsyncEventHandler overrunHandler,
                           AsyncEventHandler missHandler)

Creates a new AperiodicParameters instance.

Parameters:

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 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.

Method Detail

setIfFeasible

public boolean setIfFeasible(RelativeTime cost,
                             RelativeTime deadline)

Attempt to change the cost and deadline. The values will be changed if the resulting system is feasible. If the resulting system would not be feasible no changes are made.

Overrides:

setIfFeasible in class ReleaseParameters

Parameters:

cost - The proposed cost. If zero, no change is made.

deadline - The proposed deadline. If zero, no change is made.

Returns:

true if the resulting system is feasible and the changes are made. false if the resulting system is not feasible and no changes are made.