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Class: WeakValueIdentityDictionary


Inheritance:

   Object
   |
   +--Collection
      |
      +--Set
         |
         +--Dictionary
            |
            +--IdentityDictionary
               |
               +--WeakValueIdentityDictionary

Package:
stx:libbasic
Category:
Collections-Weak
Version:
rev: 1.7 date: 2016/04/05 18:47:58
user: stefan
file: WeakValueIdentityDictionary.st directory: libbasic
module: stx stc-classLibrary: libbasic
Author:
Claus (stolen from Stefans WeakValueDictionary)

Description:


WeakValueIdentityDictionaries behave like IdentityDictionaries, 
as long as the values are still referenced by some 
other (non-weak) object.
However, once the last non-weak reference ceases to exist,
the Dictionary will return nil for the value at position key.
(with some delay: it will be removed after the next garbage collect).


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.

Related information:

    WeakArray
    WeakIdentityDictionary
    WeakIdentitySet
    WeakValueDictionary

Instance protocol:

adding & removing
o  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.

o  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).

o  removeValue: aKey ifAbsent: aBlock
remove the association under aValue from the collection,
return the key 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).

element disposal
o  update: something with: aParameter from: changedObject
an element (either key or value) died - clear out slots for
disposed keys.

private
o  valueContainerOfSize: n
return a container for values of size n.
use WeakArrays here.

testing
o  includes: anObject
redefined to block interrupts
(avoid change of the dictionary while accessing)

o  includesKey: key
redefined to block interrupts
(avoid change of the dictionary while accessing)

o  isWeakCollection
return true, if the receiver has weak references to its elements.



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