SharedQueue.st
author fm
Fri, 08 Aug 2008 15:32:03 +0200
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"
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 COPYRIGHT (c) 1993 by Claus Gittinger
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	      All Rights Reserved
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 This software is furnished under a license and may be used
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 only in accordance with the terms of that license and with the
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 inclusion of the above copyright notice.   This software may not
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 be provided or otherwise made available to, or used by, any
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 other person.  No title to or ownership of the software is
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 hereby transferred.
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"
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"{ Package: 'stx:libbasic2' }"
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Queue subclass:#SharedQueue
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	instanceVariableNames:'dataAvailable spaceAvailable accessLock'
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	classVariableNames:''
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	poolDictionaries:''
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	category:'Kernel-Processes'
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!
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!SharedQueue class methodsFor:'documentation'!
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copyright
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"
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 COPYRIGHT (c) 1993 by Claus Gittinger
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	      All Rights Reserved
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 This software is furnished under a license and may be used
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 only in accordance with the terms of that license and with the
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 inclusion of the above copyright notice.   This software may not
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 be provided or otherwise made available to, or used by, any
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 other person.  No title to or ownership of the software is
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 hereby transferred.
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!
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documentation
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"
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    SharedQueues provide a safe mechanism for processes to communicate.
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    They are basically Queues, with added secure access to the internals,
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    allowing use from multiple processes (i.e. the access methods use
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    critical regions to protect against confusion due to a process
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    switch within a modification).
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    Also, sharedQueues can be used for synchronization, since a reading
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    process will be blocked when attempting to read an empty queue, while
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    a writer will be blocked when attempting to write into a full queue.
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    For nonBlocking read, use #isEmpty; for nonBlocking write, use #isFull.
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    See samples in doc/coding.
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    [author:]
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        Claus Gittinger
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    [see also:]
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        Semaphore
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        Process
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        CodingExamples::SharedQueueExamples
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!
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examples
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    |queues readers writers seqNumber accessLock accessLock2
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     numbersStillToReceive|
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    seqNumber := 1.
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    accessLock := Semaphore forMutualExclusion.
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    accessLock2 := Semaphore forMutualExclusion.
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    numbersStillToReceive := BooleanArray new:100000 withAll:true.
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    queues := (1 to:10) collect:[:i | SharedQueue new].
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    readers := (1 to:10) collect:[:i |
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                                    [   |num|
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                                        10000 timesRepeat:[
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                                            num := (queues at:i) next.
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                                            accessLock2 critical:[
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                                                (numbersStillToReceive at:num) ifFalse:[
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                                                    self halt:(num printString , ' received twice')
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                                                ] ifTrue:[
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                                                    numbersStillToReceive at:num put:false.
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                                                ].
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                                            ].
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                                            'num printCR.'.
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                                        ].
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                                    ] fork
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                                 ].
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    writers := (1 to:10) collect:[:i |
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                                    [   |num|
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                                        10000 timesRepeat:[
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                                            accessLock critical:[
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                                                num := seqNumber.
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                                                seqNumber := seqNumber + 1.
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                                            ].
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                                            (queues at:i) nextPut:num.
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                                        ]
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                                    ] fork
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                                 ].
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    readers do:[:aReader | aReader waitUntilTerminated].
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    ' any left ? '.
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    (numbersStillToReceive includes:true) ifTrue:[
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        self halt:'oops - not all numbers received'
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    ]
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"
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! !
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!SharedQueue methodsFor:'accessing'!
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do:anObject
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    "evaluate the argument, aBlock for each element in the queue"
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    |retVal|
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    accessLock critical:[
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        retVal := super do:anObject.
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    ].
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    ^ retVal.
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!
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next
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    "return the next value in the queue; if it its empty, wait 'til
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     something is put into the receiver.
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     When the datum has been removed, signal space-availability to
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     writers"
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    |retVal|
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    dataAvailable wait.
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    accessLock critical:[
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        retVal := super next.
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    ].
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    spaceAvailable signal.
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    ^ retVal.
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!
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nextIfEmpty:exceptionValue
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    "return the next value in the queue; if it its empty do not wait, but return
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     the value of exceptionValue.
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     When a datum has been removed, signal space-availability to writers"
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    |retVal anyRemoved|
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    accessLock critical:[
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        self isEmpty ifTrue:[
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            retVal := exceptionValue value
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        ] ifFalse:[
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            retVal := super next.
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            anyRemoved := true.
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        ]
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    ].
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    anyRemoved == true ifTrue:[spaceAvailable signal].
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    ^ retVal.
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!
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nextOrNil
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    ^ self nextIfEmpty:nil
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    "Created: / 31-05-2007 / 15:09:33 / cg"
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!
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nextPut:anObject
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    "enter anObject into the queue; wait for available space, if
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     the queue is full. After the put, signal availablity of a datum
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     to readers."
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    |retVal|
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    spaceAvailable wait.
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    accessLock critical:[
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        retVal := super nextPut:anObject.
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    ].
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    dataAvailable signal.
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    ^ retVal.
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!
156
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1124
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nextPutFirst:anObject
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    |retVal|
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    spaceAvailable wait.
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    accessLock critical:[
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        retVal := super nextPutFirst:anObject.
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   188
    ].
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    dataAvailable signal.
1502
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    ^ retVal.
1124
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   191
!
f653d6a20abd +nextPutFirst:
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   192
1933
448db7605469 +nextWithTimeout:
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nextWithTimeout:seconds
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    "return the next value in the queue; if it its empty, wait 'til
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   195
     something is put into the receiver.
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     When the datum has been removed, signal space-availability to
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   197
     writers"
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448db7605469 +nextWithTimeout:
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    |retVal|
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448db7605469 +nextWithTimeout:
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    (dataAvailable waitWithTimeout:seconds) isNil ifTrue:[
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        ^ nil
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   203
    ].
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    accessLock critical:[
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        retVal := super next.
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   206
    ].
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    spaceAvailable signal.
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   208
448db7605469 +nextWithTimeout:
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   209
    ^ retVal.
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   210
!
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   211
1620
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peek
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    self isEmpty ifTrue:[
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        dataAvailable waitUncounted.
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   215
    ].
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    ^ super peek
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!
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   218
647
f937d30a8afc remove all elements in the queue:
ca
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diff changeset
   219
removeAll
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   220
    "remove all elements in the queue; do not wait, but
f937d30a8afc remove all elements in the queue:
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   221
     synchronize access to the queue.
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   222
     If the queue was full before, signal space-availability to writers.
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ca
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diff changeset
   223
     This can be used to flush queues in multi-process applications,
f937d30a8afc remove all elements in the queue:
ca
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diff changeset
   224
     when cleanup is required."
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diff changeset
   225
916
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   226
    |count|
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diff changeset
   227
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    count := 0.
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   229
    [(dataAvailable waitWithTimeout:0) notNil] whileTrue:[
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   230
        count := count + 1.
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   231
    ].    
917
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    accessLock critical:[
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   233
        super removeAll.
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   234
    ].
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   235
    count timesRepeat:[spaceAvailable signal].
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   236
!
647
f937d30a8afc remove all elements in the queue:
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parents: 487
diff changeset
   237
1494
8f617564556b +removeIdentical
penk
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   238
removeIdentical:anElement ifAbsent:exceptionalValue
1502
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   239
    |retVal noSuchElement|
1494
8f617564556b +removeIdentical
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diff changeset
   240
8f617564556b +removeIdentical
penk
parents: 1489
diff changeset
   241
    noSuchElement := false.
8f617564556b +removeIdentical
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diff changeset
   242
    accessLock critical:[
1502
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diff changeset
   243
        retVal := super removeIdentical:anElement ifAbsent:[noSuchElement := true]
1494
8f617564556b +removeIdentical
penk
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diff changeset
   244
    ].
8f617564556b +removeIdentical
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diff changeset
   245
    noSuchElement ifTrue:[
8f617564556b +removeIdentical
penk
parents: 1489
diff changeset
   246
        ^ exceptionalValue value.
8f617564556b +removeIdentical
penk
parents: 1489
diff changeset
   247
    ].
1498
681b0afc046c removeIdentical: ifAbsent:
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diff changeset
   248
    spaceAvailable signal.
1502
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diff changeset
   249
    ^ retVal.
1494
8f617564556b +removeIdentical
penk
parents: 1489
diff changeset
   250
!
8f617564556b +removeIdentical
penk
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diff changeset
   251
396
88bd6136ee67 added #removeLast
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diff changeset
   252
removeLast
88bd6136ee67 added #removeLast
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diff changeset
   253
    "return the last value in the queue; if it its empty, wait 'til
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diff changeset
   254
     something is put into the receiver.
88bd6136ee67 added #removeLast
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diff changeset
   255
     When the datum has been removed, signal space-availability to
88bd6136ee67 added #removeLast
Claus Gittinger <cg@exept.de>
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diff changeset
   256
     writers"
88bd6136ee67 added #removeLast
Claus Gittinger <cg@exept.de>
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diff changeset
   257
1502
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diff changeset
   258
    |retVal|
396
88bd6136ee67 added #removeLast
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diff changeset
   259
916
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diff changeset
   260
    dataAvailable wait.
917
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parents: 916
diff changeset
   261
    accessLock critical:[
1502
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diff changeset
   262
        retVal := super removeLast.
917
df608391baa5 Need access lock when calling super methods.
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diff changeset
   263
    ].
916
63fddba933d6 Fix bug with two reader and two writer processes.
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diff changeset
   264
    spaceAvailable signal.
396
88bd6136ee67 added #removeLast
Claus Gittinger <cg@exept.de>
parents: 257
diff changeset
   265
1502
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diff changeset
   266
    ^ retVal.
931
60a44b4aa743 *** empty log message ***
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parents: 917
diff changeset
   267
! !
60a44b4aa743 *** empty log message ***
Claus Gittinger <cg@exept.de>
parents: 917
diff changeset
   268
60a44b4aa743 *** empty log message ***
Claus Gittinger <cg@exept.de>
parents: 917
diff changeset
   269
!SharedQueue methodsFor:'accessing-internals'!
60a44b4aa743 *** empty log message ***
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diff changeset
   270
1489
88159ab72ba0 access to accessLock
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diff changeset
   271
accessLock
88159ab72ba0 access to accessLock
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diff changeset
   272
    "return the critical access-semaphore which is used internally to syncronize access"
88159ab72ba0 access to accessLock
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diff changeset
   273
88159ab72ba0 access to accessLock
Claus Gittinger <cg@exept.de>
parents: 1124
diff changeset
   274
    ^ accessLock
88159ab72ba0 access to accessLock
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diff changeset
   275
!
88159ab72ba0 access to accessLock
Claus Gittinger <cg@exept.de>
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diff changeset
   276
931
60a44b4aa743 *** empty log message ***
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parents: 917
diff changeset
   277
readSemaphore
60a44b4aa743 *** empty log message ***
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parents: 917
diff changeset
   278
    "return the semaphore which is signalled when data is available
60a44b4aa743 *** empty log message ***
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parents: 917
diff changeset
   279
     for reading."
60a44b4aa743 *** empty log message ***
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diff changeset
   280
60a44b4aa743 *** empty log message ***
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parents: 917
diff changeset
   281
    ^ dataAvailable
60a44b4aa743 *** empty log message ***
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diff changeset
   282
60a44b4aa743 *** empty log message ***
Claus Gittinger <cg@exept.de>
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   283
    "Modified: 16.12.1995 / 13:47:11 / cg"
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diff changeset
   284
!
60a44b4aa743 *** empty log message ***
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parents: 917
diff changeset
   285
2022
0f7f5bae8bdd readWait
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parents: 1933
diff changeset
   286
readWaitWithTimeoutMs:ms
2032
05ebef21930b comment
fm
parents: 2022
diff changeset
   287
    "Return true if a timeout occured (i.e. false, if data is available)."
05ebef21930b comment
fm
parents: 2022
diff changeset
   288
2022
0f7f5bae8bdd readWait
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parents: 1933
diff changeset
   289
    |avail|
0f7f5bae8bdd readWait
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diff changeset
   290
0f7f5bae8bdd readWait
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parents: 1933
diff changeset
   291
    dataAvailable wouldBlock ifFalse:[^ false].
0f7f5bae8bdd readWait
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diff changeset
   292
    avail := (dataAvailable waitWithTimeoutMs:ms) notNil.
0f7f5bae8bdd readWait
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parents: 1933
diff changeset
   293
    avail ifTrue:[
0f7f5bae8bdd readWait
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diff changeset
   294
        "/ sigh - the above wait has already consumed the sema
0f7f5bae8bdd readWait
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diff changeset
   295
        dataAvailable signal
0f7f5bae8bdd readWait
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parents: 1933
diff changeset
   296
    ].
0f7f5bae8bdd readWait
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diff changeset
   297
    ^ avail not
0f7f5bae8bdd readWait
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parents: 1933
diff changeset
   298
!
0f7f5bae8bdd readWait
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parents: 1933
diff changeset
   299
931
60a44b4aa743 *** empty log message ***
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diff changeset
   300
withAccessLockedDo:aBlock
60a44b4aa743 *** empty log message ***
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parents: 917
diff changeset
   301
    "evaluate aBlock while access via next/nextPut are blocked."
60a44b4aa743 *** empty log message ***
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parents: 917
diff changeset
   302
60a44b4aa743 *** empty log message ***
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parents: 917
diff changeset
   303
    accessLock critical:aBlock
917
df608391baa5 Need access lock when calling super methods.
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parents: 916
diff changeset
   304
!
396
88bd6136ee67 added #removeLast
Claus Gittinger <cg@exept.de>
parents: 257
diff changeset
   305
156
109b1c9342b2 access methods for the internal semaphores added (maybe useful when waiting for multiple queues)
Claus Gittinger <cg@exept.de>
parents: 141
diff changeset
   306
writeSemaphore
109b1c9342b2 access methods for the internal semaphores added (maybe useful when waiting for multiple queues)
Claus Gittinger <cg@exept.de>
parents: 141
diff changeset
   307
    "return the semaphore which is signalled when the queue has space
109b1c9342b2 access methods for the internal semaphores added (maybe useful when waiting for multiple queues)
Claus Gittinger <cg@exept.de>
parents: 141
diff changeset
   308
     for writing."
109b1c9342b2 access methods for the internal semaphores added (maybe useful when waiting for multiple queues)
Claus Gittinger <cg@exept.de>
parents: 141
diff changeset
   309
109b1c9342b2 access methods for the internal semaphores added (maybe useful when waiting for multiple queues)
Claus Gittinger <cg@exept.de>
parents: 141
diff changeset
   310
    ^ spaceAvailable
109b1c9342b2 access methods for the internal semaphores added (maybe useful when waiting for multiple queues)
Claus Gittinger <cg@exept.de>
parents: 141
diff changeset
   311
109b1c9342b2 access methods for the internal semaphores added (maybe useful when waiting for multiple queues)
Claus Gittinger <cg@exept.de>
parents: 141
diff changeset
   312
    "Modified: 16.12.1995 / 13:47:07 / cg"
0
1cf8d1747859 Initial revision
claus
parents:
diff changeset
   313
! !
141
2804943fc6f0 checkin from browser
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parents: 112
diff changeset
   314
2804943fc6f0 checkin from browser
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parents: 112
diff changeset
   315
!SharedQueue methodsFor:'initialization'!
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parents: 112
diff changeset
   316
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diff changeset
   317
init:size
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parents: 112
diff changeset
   318
    "initialize the receiver for size entries"
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parents: 112
diff changeset
   319
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parents: 112
diff changeset
   320
    super init:size.
487
0230ee378075 checkin from browser
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parents: 485
diff changeset
   321
    dataAvailable := Semaphore new name:'shared q-read'.
917
df608391baa5 Need access lock when calling super methods.
Stefan Vogel <sv@exept.de>
parents: 916
diff changeset
   322
    spaceAvailable := (Semaphore new:size) name:'shared q-write'.
931
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parents: 917
diff changeset
   323
    accessLock := RecursionLock new.
487
0230ee378075 checkin from browser
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parents: 485
diff changeset
   324
917
df608391baa5 Need access lock when calling super methods.
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parents: 916
diff changeset
   325
    "Modified: 25.1.1997 / 00:19:45 / cg"
df608391baa5 Need access lock when calling super methods.
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parents: 916
diff changeset
   326
! !
141
2804943fc6f0 checkin from browser
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parents: 112
diff changeset
   327
469
9b4318b56d9d commentary
Claus Gittinger <cg@exept.de>
parents: 396
diff changeset
   328
!SharedQueue class methodsFor:'documentation'!
141
2804943fc6f0 checkin from browser
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parents: 112
diff changeset
   329
2804943fc6f0 checkin from browser
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diff changeset
   330
version
2032
05ebef21930b comment
fm
parents: 2022
diff changeset
   331
    ^ '$Header: /cvs/stx/stx/libbasic2/SharedQueue.st,v 1.36 2008-08-08 13:32:03 fm Exp $'
141
2804943fc6f0 checkin from browser
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parents: 112
diff changeset
   332
! !