Class: WeakIdentityDictionary

• Inheritance
• Description
• Instance protocol
  • accessing
  • adding & removing
  • element disposal
  • enumerating
  • private
  • queries
  • testing

Inheritance:

   Object
   |
   +--Collection
      |
      +--Set
         |
         +--Dictionary
            |
            +--IdentityDictionary
               |
               +--WeakIdentityDictionary
                  |
                  +--Registry
                  |
                  +--WeakDependencyDictionary

Package:

stx:libbasic

Category:

Collections-Weak

Version:

rev: 1.68 date: 2022/09/26 09:56:49

user: matilk

file: WeakIdentityDictionary.st directory: libbasic

module: stx stc-classLibrary: libbasic

Description:

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 to a key 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 - a value 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.

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.

Instance protocol:

 keys

return a collection containing all valid keys of the receiver

 at: key ifAbsent: exceptionBlock

redefined to block interrupts
(avoid change of the dictionary while accessing)

 at: key ifAbsentPut: replacementBlock

redefined to block interrupts
(avoid change of the dictionary while accessing)

 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.

 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).

 safeRemoveKey: key

redefined to block interrupts
(avoid change of the dictionary while accessing)

 clearDeadSlots

an element (one of my keys) died - clear slots for
disposed keys and set corresponding values to nil.

 update: anAspect with: aParameter from: changedObject

one of our keys died - clear out slots for disposed keys.

 keysAndValuesDo: aTwoArgBlock

evaluate aTwoArgBlock for each registered object with key and value

 keysDo: aBlock

evaluate aBlock for each registered object

 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.

 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.

 grow: newSize

grow the receiver.
Redefined to block interrupts, to avoid trouble when dependencies
are added within interrupting high prio processes.

Usage example(s):

'grow:' printCR.

 initializeForCapacity: minSize

reset the receiver's contents.
Redefined to block interrupts, to avoid trouble when dependencies
are added within interrupting high prio processes.

 keyContainerOfSize: n

return a container for keys of size n.
use WeakArrays here.

 rehash

grow the receiver.
Redefined to block interrupts, to avoid trouble when dependencies
are added within interrupting high prio processes.

Usage example(s):

'rehash' printCR.

 includes: anObject

redefined to block interrupts
(avoid change of the dictionary while accessing)

 includesKey: key

redefined to block interrupts
(avoid change of the dictionary while accessing)

 isWeak

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

 isWeakCollection

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