"

 COPYRIGHT (c) 1992 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

"{ Package: 'stx:libbasic' }"

"{ NameSpace: Smalltalk }"

IdentityDictionary subclass:#WeakIdentityDictionary

	instanceVariableNames:''

	classVariableNames:''

	poolDictionaries:''

	category:'Collections-Weak'

!

!WeakIdentityDictionary class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1992 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

!

documentation

"

    WeakIdentityDictionaries behave like IdentityDictionaries,

    as long as the keys are still referenced by some

    other (non-weak) object.

    However, once the last non-weak reference ceases to exist,

    the object will be automatically removed from the Weakcollection

    (with some delay: it will be removed after the next garbage collect).

    This class was added to support keeping track of dependents without

    keeping the values alive - values simply become nil when no one else

    references it. The original dependency mechanism used a regular Dictionary,

    which usually leads to a lot of garbage being kept due to a forgotten

    release. Using a WeakDictionary may be incompatible to ST-80 but is much

    more comfortable, since no manual release of dependents is needed.

    [Warning:]

      If you use this, be very careful since the collections size changes

      'magically' - for example, testing for being nonEmpty and then

      removing the first element may fail, since the element may vanish inbetween.

      In general, never trust the value as returned by the size/isEmpty messages.

    [author:]

	Claus Gittinger

    [See also:]

	WeakArray WeakValueDictionary WeakIdentitySet

"

! !

!WeakIdentityDictionary methodsFor:'adding & removing'!

at:key ifAbsent:exceptionBlock

    "redefined to block interrupts

     (avoid change of the dictionary while accessing)"

    |val|

    key class == SmallInteger ifTrue:[  

        "SmallIntegers cannot be stored into a WeakArray"

        ^ exceptionBlock value.

    ].

    (OperatingSystem blockInterrupts) ifTrue:[

        "/ already blocked

        ^ super at:key ifAbsent:exceptionBlock.

    ].

    [

        val := super at:key ifAbsent:exceptionBlock.

    ] ensure:[

        OperatingSystem unblockInterrupts.

    ].

    ^ val

    "Modified: 6.5.1996 / 12:22:26 / stefan"

    "Modified: 1.7.1997 / 10:45:47 / cg"

!

at:key ifAbsentPut:replacementBlock

    "redefined to block interrupts

     (avoid change of the dictionary while accessing)"

    |val|

    key class == SmallInteger ifTrue:[  

        "SmallIntegers cannot be stored into a WeakArray"

        self error:'WeakidentityDictionary: cannot store a SmallInteger'.

    ].

    (OperatingSystem blockInterrupts) ifTrue:[

        "/ already blocked

        ^ super at:key ifAbsentPut:replacementBlock.

    ].

    [

        val := super at:key ifAbsentPut:replacementBlock.

    ] ensure:[

        OperatingSystem unblockInterrupts.

    ].

    ^ val

!

at:key put:anObject

    "add the argument anObject under key, aKey to the receiver.

     Return anObject (sigh).

     Redefined to block interrupts, to avoid trouble when dependencies

     are added within interrupting high prio processes."

    |val|

    key class == SmallInteger ifTrue:[  

        "SmallIntegers cannot be stored into a WeakArray"

        self error:'WeakidentityDictionary: cannot store a SmallInteger'.

    ].

    (OperatingSystem blockInterrupts) ifTrue:[

        "/ already blocked

        ^ super at:key put:anObject.

    ].

    [

        val := super at:key put:anObject.

    ] ensure:[

        OperatingSystem unblockInterrupts.

    ].

    ^ val

    "Modified: 6.5.1996 / 12:22:26 / stefan"

    "Modified: 29.1.1997 / 15:08:45 / cg"

!

removeKey:aKey ifAbsent:aBlock

    "remove the association under aKey from the collection,

     return the value previously stored there.

     If it was not in the collection return the result

     from evaluating aBlock.

    Redefined to avoid synchronization problems, in case

    of interrupts (otherwise, there could be some other operation

    on the receiver done by another process, which garbles my contents)."

    |ret|

    aKey class == SmallInteger ifTrue:[  

        "SmallIntegers cannot be stored into a WeakArray"

        ^ aBlock value.

    ].

    (OperatingSystem blockInterrupts) ifTrue:[

        "/ already blocked

        ^ super removeKey:aKey ifAbsent:aBlock.

    ].

    [

        ret := super removeKey:aKey ifAbsent:aBlock

    ] ensure:[

        OperatingSystem unblockInterrupts

    ].

    ^ ret

    "Modified: 6.5.1996 / 12:44:51 / stefan"

    "Modified: 29.1.1997 / 15:09:11 / cg"

!

safeRemoveKey:key

    "redefined to block interrupts

     (avoid change of the dictionary while accessing)"

    |val|

    key class == SmallInteger ifTrue:[  

        "SmallIntegers cannot be stored into a WeakArray"

        ^ nil.

    ].

    (OperatingSystem blockInterrupts) ifTrue:[

        "/ already blocked

        ^ super safeRemoveKey:key.

    ].

    [

        val := super safeRemoveKey:key.

    ] ensure:[

        OperatingSystem unblockInterrupts.

    ].

    ^ val

    "Modified: 6.5.1996 / 12:22:26 / stefan"

    "Modified: 1.7.1997 / 10:45:52 / cg"

    "Created: 1.7.1997 / 10:46:34 / cg"

! !

!WeakIdentityDictionary methodsFor:'element disposal'!

clearDeadSlots

    |wasBlocked anyChange|

    "

     have to block here - dispose may be done at a low priority

     from the background finalizer. If new items are added by a

     higher prio process, the dictionary might get corrupted otherwise

    "

    wasBlocked := OperatingSystem blockInterrupts.

    anyChange := false.

    [

        keyArray

            forAllDeadIndicesDo:[:idx |

                                    valueArray basicAt:idx put:nil.

                                    tally := tally - 1.

                                    anyChange := true.

                                ]

            replacingCorpsesWith:DeletedEntry.

    ] ensure:[

        wasBlocked ifFalse:[OperatingSystem unblockInterrupts].

    ].

    anyChange ifTrue:[

        self changed:#ElementExpired

    ].    

    "Modified: / 13.12.2001 / 14:18:17 / martin"

!

update:something with:aParameter from:changedObject

    "an element (either key or value) died - clear out slots for

     disposed keys."

    something == #ElementExpired ifTrue:[

	self clearDeadSlots.

    ]

    "Created: / 7.1.1997 / 16:59:30 / stefan"

    "Modified: / 13.12.2001 / 14:17:58 / martin"

! !

!WeakIdentityDictionary methodsFor:'private'!

findKeyOrNil:key

    "Look for the key in the receiver.

     If it is found, return the index,

     otherwise the index of the first unused slot.

     Grow the receiver, if key was not found, and no unused slots were present.

     Warning: an empty slot MUST be filled by the sender - it is only to be sent

              by at:put: / add: - like methods."

    |index  "{ Class:SmallInteger }"

     length "{ Class:SmallInteger }"

     startIndex probe

     delIndex "{ Class:SmallInteger }"|

    (OperatingSystem blockInterrupts) ifFalse:[

        "/

        "/ may never be entered with interrupts enabled

        "/

        OperatingSystem unblockInterrupts.

        self error:'unblocked call of findKeyOrNil'.

    ].

    delIndex := 0.

    length := keyArray basicSize.

    startIndex := index := self initialIndexForKey:key.

    [

        probe := keyArray basicAt:index.

        key == probe ifTrue:[^ index].

        probe isNil ifTrue:[

            delIndex == 0 ifTrue:[^ index].

            keyArray basicAt:delIndex put:nil.

            ^ delIndex

        ].

        probe class == SmallInteger ifTrue:[

            probe := DeletedEntry.

            keyArray basicAt:index put:probe.

            valueArray basicAt:index put:nil.

            tally := tally - 1.

        ].

        (delIndex == 0 and:[probe == DeletedEntry]) ifTrue:[

            delIndex := index

        ].

        index == length ifTrue:[

            index := 1

        ] ifFalse:[

            index := index + 1

        ].

        index == startIndex ifTrue:[

            delIndex ~~ 0 ifTrue:[

                keyArray basicAt:delIndex put:nil.

                ^ delIndex

            ].

            self grow.

            length := keyArray basicSize.

            startIndex := index := self initialIndexForKey:key.

        ].

    ] loop.

    "Modified: 30.1.1997 / 15:04:34 / cg"

    "Modified: 1.10.1997 / 11:25:32 / stefan"

!

findKeyOrNilOrDeletedEntry:key

    "Look for the key in the receiver.

     If it is found, return the index,

     otherwise the index of the first unused slot.

     Grow the receiver, if key was not found, and no unused slots were present."

    |index  "{ Class:SmallInteger }"

     length "{ Class:SmallInteger }"

     startIndex probe

     delIndex "{ Class:SmallInteger }"|

    (OperatingSystem blockInterrupts) ifFalse:[

        "/

        "/ may never be entered with interrupts enabled

        "/

        OperatingSystem unblockInterrupts.

        self error:'unblocked call of findKeyOrNil'.

    ].

    delIndex := 0.

    length := keyArray basicSize.

    startIndex := index := self initialIndexForKey:key.

    [

        probe := keyArray basicAt:index.

        key == probe ifTrue:[^ index].

        probe isNil ifTrue:[

            delIndex == 0 ifTrue:[^ index].

            ^ delIndex

        ].

        probe class == SmallInteger ifTrue:[

            probe := DeletedEntry.

            keyArray basicAt:index put:probe.

            valueArray basicAt:index put:nil.

            tally := tally - 1.

        ].

        (delIndex == 0 and:[probe == DeletedEntry]) ifTrue:[

            delIndex := index

        ].

        index == length ifTrue:[

            index := 1

        ] ifFalse:[

            index := index + 1

        ].

        index == startIndex ifTrue:[

            delIndex ~~ 0 ifTrue:[

                ^ delIndex

            ].

            self grow.

            length := keyArray basicSize.

            startIndex := index := self initialIndexForKey:key.

        ].

    ] loop.

    "Modified: 30.1.1997 / 15:04:34 / cg"

    "Modified: 1.10.1997 / 11:25:32 / stefan"

!

grow:newSize

    "grow the receiver.

     Redefined to block interrupts, to avoid trouble when dependencies

     are added within interrupting high prio processes."

"/ 'grow:' printCR.

    (OperatingSystem blockInterrupts) ifTrue:[

	"/ already blocked

	^ super grow:newSize.

    ].

    [

	super grow:newSize

    ] ensure:[

	OperatingSystem unblockInterrupts

    ].

    "Created: 28.1.1997 / 23:41:39 / cg"

    "Modified: 29.1.1997 / 15:10:12 / cg"

!

initializeForCapacity:minSize

    "reset the receiver's contents.

     Redefined to block interrupts, to avoid trouble when dependencies

     are added within interrupting high prio processes."

"/ 'setTally:' printCR.

    (OperatingSystem blockInterrupts) ifTrue:[

	"/ already blocked

	super initializeForCapacity:minSize.

	^ self.

    ].

    [

	super initializeForCapacity:minSize

    ] ensure:[

	OperatingSystem unblockInterrupts

    ].

    "Created: 29.1.1997 / 11:40:12 / cg"

    "Modified: 29.1.1997 / 15:11:11 / cg"

!

keyContainerOfSize:n

    "return a container for keys of size n.

     use WeakArrays here."

    |w|

    w := WeakArray new:n.

    w addDependent:self.

    ^ w

    "Modified: 7.1.1997 / 17:01:15 / stefan"

    "Modified: 29.1.1997 / 14:18:49 / cg"

!

rehash

    "grow the receiver.

     Redefined to block interrupts, to avoid trouble when dependencies

     are added within interrupting high prio processes."

"/ 'rehash' printCR.

    (OperatingSystem blockInterrupts) ifTrue:[

	"/ already blocked

	super rehash.

	^ self.

    ].

    [

	super rehash

    ] ensure:[

	OperatingSystem unblockInterrupts

    ].