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"
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COPYRIGHT (c) 1996 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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Stream subclass:#FilteringStream
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instanceVariableNames:'inputStream outputStream filter unbound'
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classVariableNames:''
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poolDictionaries:''
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category:'Streams'
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!
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!FilteringStream class methodsFor:'documentation'!
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copyright
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"
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COPYRIGHT (c) 1996 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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!
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documentation
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"
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A FilteringStream can be connected to some input
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(from which elements are read via the ReadStream protocol),
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and/or to some output (to which elements are written via
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the WriteStream protocol.
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The FilteringStream itself performs some filtering/processing
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on the elements as they arrive.
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[instance variables:]
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inputStream <Stream> the stream from which elements are read
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outputStream <Stream> the stream to which elements are written
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filter <Block> the filter block;
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unbound <Boolean> if true, the stream is unbound.
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[author:]
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Claus Gittinger
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[See also:]
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ReadStream WriteStream
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"
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!
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examples
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filter random numbers:
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[exBegin]
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|in filter|
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in := Random new.
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filter := FilteringLineStream basicNew.
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filter inputStream:in.
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filter filter:[:num | ((num >= 0.5) and:[num <= 0.6]) ifTrue:[num] ifFalse:[nil]].
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20 timesRepeat:[
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Transcript showCR:(filter next printString).
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]
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[exEnd]
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filtering prime numbers:
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[exBegin]
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|num generator primeFilter addFilter|
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num := 1.
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generator := Plug new.
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generator respondTo:#next
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with:[num := num + 1. num].
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generator respondTo:#atEnd
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with:[false].
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addFilter := [:prime | |newFilter|
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newFilter := FilteringLineStream basicNew.
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newFilter filter:[:num | (num \\ prime) == 0 ifTrue:[
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nil
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] ifFalse:[
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num
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]
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].
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newFilter inputStream:primeFilter.
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primeFilter := newFilter
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].
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addFilter value:2.
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primeFilter inputStream:generator.
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10000 timesRepeat:[
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|nextPrime|
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nextPrime := primeFilter next.
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addFilter value:nextPrime.
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Transcript showCR:nextPrime.
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]
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[exEnd]
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"
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! !
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!FilteringStream methodsFor:'access - pull-reading'!
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filterUpToEnd
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"pull input from inputStream up to the end,
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push it filtered into the outputStream"
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[inputStream atEnd] whileFalse:[
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self nextPut:(inputStream next)
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].
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"Modified: 2.7.1996 / 21:02:49 / cg"
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"Created: 2.7.1996 / 21:06:42 / cg"
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!
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next
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"pull input from inputStream and
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push it filtered into the outputStream"
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|input output|
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[inputStream atEnd] whileFalse:[
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"/ get an element
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input := inputStream next.
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"/ filter it - this may return nil, to eat it
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output := filter value:input.
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output notNil ifTrue:[
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"/ good - output it
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^ output.
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].
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].
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^ nil
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"Created: 2.7.1996 / 21:09:58 / cg"
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472
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"Modified: 10.1.1997 / 20:23:36 / cg"
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! !
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!FilteringStream methodsFor:'access - push-writing'!
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nextPut:something
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"push something through the filter"
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|output|
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"/ filter it
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output := filter value:something.
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output notNil ifTrue:[
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outputStream nextPut:output
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]
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"Created: 2.7.1996 / 21:07:58 / cg"
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"Modified: 10.1.1997 / 20:23:56 / cg"
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! !
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!FilteringStream methodsFor:'accessing'!
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filter
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"return the filter"
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^ filter
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"Modified: 2.7.1996 / 21:03:36 / cg"
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"Created: 2.7.1996 / 21:06:42 / cg"
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!
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filter:something
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"set the filter"
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filter := something.
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"Modified: 2.7.1996 / 21:03:40 / cg"
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"Created: 2.7.1996 / 21:06:42 / cg"
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!
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inputStream
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"return the inputStream"
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^ inputStream
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"Modified: 2.7.1996 / 21:03:43 / cg"
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"Created: 2.7.1996 / 21:06:42 / cg"
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!
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inputStream:something
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"set the inputStream"
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inputStream := something.
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"Modified: 2.7.1996 / 21:03:46 / cg"
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"Created: 2.7.1996 / 21:06:42 / cg"
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!
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outputStream
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"return the outputStream"
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^ outputStream
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"Modified: 2.7.1996 / 21:03:49 / cg"
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"Created: 2.7.1996 / 21:06:42 / cg"
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!
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outputStream:something
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"set the outputStream"
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outputStream := something.
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"Modified: 2.7.1996 / 21:03:52 / cg"
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"Created: 2.7.1996 / 21:06:42 / cg"
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!
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unbound
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"return the unbound flag"
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^ unbound
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"Created: 2.7.1996 / 21:25:40 / cg"
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"Modified: 10.1.1997 / 20:21:53 / cg"
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!
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unbound:something
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"set the unbound flag"
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unbound := something.
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"Created: 2.7.1996 / 21:25:40 / cg"
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"Modified: 10.1.1997 / 20:21:59 / cg"
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! !
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!FilteringStream methodsFor:'queries'!
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atEnd
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"return true, if the receiver stream is at the end"
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unbound ifTrue:[^ false].
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^ inputStream atEnd
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"Created: 2.7.1996 / 21:19:51 / cg"
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"Modified: 10.1.1997 / 20:22:20 / cg"
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! !
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!FilteringStream class methodsFor:'documentation'!
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version
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^ '$Header: /cvs/stx/stx/libbasic2/FilteringStream.st,v 1.2 1997-01-10 20:51:24 cg Exp $'
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! !
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