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"
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COPYRIGHT (c) 1992 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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Dictionary subclass:#IdentityDictionary
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instanceVariableNames:''
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classVariableNames:''
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poolDictionaries:''
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category:'Collections-Unordered'
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!
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IdentityDictionary comment:'
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COPYRIGHT (c) 1992 by Claus Gittinger
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All Rights Reserved
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same as a Dictionary but key must be identical - not just equal.
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Since compare is on identity keys, hashing is also done via
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identityHash instead of hash.
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$Header: /cvs/stx/stx/libbasic/IdentityDictionary.st,v 1.4 1993-11-08 02:30:40 claus Exp $
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written jul 92 by claus
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'!
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!IdentityDictionary methodsFor:'accessing'!
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keyAtValue:aValue ifAbsent:exceptionBlock
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"return the key whose value equals the argument, the value of the
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exceptionBlock if none is found..
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This is a slow access, since there is no fast reverse mapping"
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keyArray keysAndValuesDo:[:index :aKey |
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aKey notNil ifTrue:[
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(valueArray at:index) == aValue ifTrue:[^ aKey].
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]
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].
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^ exceptionBlock value
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! !
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1
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!IdentityDictionary methodsFor:'private'!
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findKeyOrNil:key
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"Look for the key in the receiver. If it is found, return
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the index of the association containing the key, otherwise
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return the index of the first unused slot. Grow the receiver,
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if key was not found, and no unused slots where present"
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|index "{ Class:SmallInteger }"
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3
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length startIndex probe |
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1
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length := keyArray basicSize.
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startIndex := key identityHash \\ length + 1.
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index := startIndex.
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[true] whileTrue:[
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probe := keyArray basicAt:index.
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(probe isNil or: [probe == key]) ifTrue:[^ index].
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index == length ifTrue:[
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index := 1
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] ifFalse:[
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index := index + 1
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].
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index == startIndex ifTrue:[^ self grow findKeyOrNil:key].
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]
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!
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findKey:key ifAbsent:aBlock
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"Look for the key in the receiver. If it is found, return
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the index of the association containing the key, otherwise
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return the value of evaluating aBlock."
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|index "{ Class:SmallInteger }"
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length "{ Class:SmallInteger }"
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startIndex
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probe|
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length := keyArray basicSize.
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length < 10 ifTrue:[
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"assuming, that for small dictionaries the overhead of hashing
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is large ... maybe that proves wrong (if overhead of comparing
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is high)"
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10
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^ keyArray identityIndexOf:key ifAbsent:aBlock.
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1
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].
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startIndex := key identityHash \\ length + 1.
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index := startIndex.
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[true] whileTrue:[
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probe := keyArray basicAt:index.
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probe == key ifTrue:[^ index].
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index == length ifTrue:[
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index := 1
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] ifFalse:[
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index := index + 1
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].
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(probe isNil or:[index == startIndex]) ifTrue:[^ aBlock value]
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]
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! !
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