"{ Package: 'stx:libbasic2' }"

Promise subclass:#TimedPromise

	instanceVariableNames:'delay ms'

	classVariableNames:''

	poolDictionaries:''

	category:'Kernel-Processes'

!

!TimedPromise class methodsFor:'documentation'!

documentation

"

    A TimedPromise is a Promise with a timeout.

    An attempt to read the value of a TimedPromise will wait until the process has finished computing it 

    or the specified timeout expires.  

    If the process terminates with an exception, an attempt to read the value of the TimedPromise will raise the same exception. 

    In case of a timeout the OsNeedRetryError will be raised.

"

!

examples

"

                                                                    [exBegin]

     |p|

     p := TimedPromise forMilliseconds:1000.

     p value:[10000 factorial] priority:Processor activePriority.

     Transcript showCR:'doing something else'.

     p value   

                                                                    [exEnd]

                                                                    [exBegin]

     |p|

     p := TimedPromise forMilliseconds:1000.

     p value:[1000 factorial] priority:Processor activePriority.

     Transcript showCR:'doing something else'.

     p value   

                                                                    [exEnd]

                                                                    [exBegin]

     |p|

     p := TimedPromise forMilliseconds:1000.

     p value:[1000 factorial. ZeroDivide raise] priority:Processor activePriority.

     Transcript showCR:'doing something else'.

     p value   

                                                                    [exEnd]

"

! !

!TimedPromise class methodsFor:'instance creation'!

forMilliseconds: ms

        ^super new ms: ms.

! !

!TimedPromise methodsFor:'accessing'!

ms: msec

	ms := msec

! !

!TimedPromise methodsFor:'accessing-parent'!

value

        | whichSemaSignalled delaySemaphore |

        " Note -- only good for one waiter "

        delay notNil ifTrue:[

            self error:'Only one waiter allowed'.

        ].

        self startup.

        delay isNil ifTrue: [ ^ super value ].

        delaySemaphore := delay delaySemaphore.

        whichSemaSignalled := (SemaphoreSet with:valueAvailable with:delaySemaphore) wait.

        delay disable.

        delay := nil.

        exception == nil

                ifTrue: [

                        whichSemaSignalled == delaySemaphore

                                ifTrue: [OSErrorHolder needRetrySignal raise]

                                ifFalse: [^value]]

                ifFalse: [exception raise "(exception copyForReraise) searchFrom: thisContext; raise"]

! !

!TimedPromise methodsFor:'private'!

startup

        ms notNil

                ifTrue:

                        [delay := Delay forMilliseconds: ms.

                        delay startup.  "Wait for data arrival or alarm expiry."]

! !

!TimedPromise class methodsFor:'documentation'!

version

    ^ '$Header: /cvs/stx/stx/libbasic2/TimedPromise.st,v 1.1 2004-11-10 10:43:11 penk Exp $'

! !