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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'
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classVariableNames:''
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poolDictionaries:''
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474
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category:'Streams-Misc'
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!
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472
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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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"
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474
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pushing the contents of a stream onto another stream
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(here, the Transcript) without a need to read everyting into a
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buffer or to reinvent the read-loop:
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(notice, a FilteringLineStream does this with less overhead)
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[exBegin]
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|in pusher|
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in := 'Makefile' asFilename readStream.
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pusher := FilteringStream readingFrom:in writingTo:Transcript.
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pusher filterUpToEnd
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[exEnd]
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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 readingFrom: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 class methodsFor:'instance creation'!
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new
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"create and return a new filteringStream.
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The resulting stream must be connected to some other stream,
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before being used"
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^ self basicNew initialize.
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"Created: 11.1.1997 / 15:31:30 / cg"
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"Modified: 11.1.1997 / 15:33:13 / cg"
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!
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readingFrom:aReadStream
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"create and return a new filteringStream, which reads from
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another stream"
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^ self basicNew initialize inputStream:aReadStream.
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"Created: 11.1.1997 / 15:32:15 / cg"
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!
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readingFrom:aReadStream writingTo:aWriteStream
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"create and return a new filteringStream, which reads from
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aReadStream and writes to aWriteStream."
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|newStream|
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newStream := self basicNew initialize.
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newStream inputStream:aReadStream.
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newStream outputStream:aWriteStream.
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^ newStream
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"Created: 11.1.1997 / 15:32:28 / cg"
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!
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writingTo:aWriteStream
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"create and return a new filteringStream, which writes to
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another stream"
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^ self basicNew initialize outputStream:aWriteStream.
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"Created: 11.1.1997 / 15:32:36 / cg"
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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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"Created: 2.7.1996 / 21:06:42 / cg"
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"Modified: 11.1.1997 / 16:08:35 / 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 isNil ifTrue:[
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^ input
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].
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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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"Modified: 11.1.1997 / 16:12:22 / 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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filter isNil ifTrue:[
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outputStream nextPut:something
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] ifFalse:[
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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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]
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"Modified: 11.1.1997 / 16:12:52 / 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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!FilteringStream methodsFor:'misc'!
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close
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"when I am closed, close my input - if any"
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inputStream notNil ifTrue:[
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inputStream close
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]
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"Created: 11.1.1997 / 15:27:17 / 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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^ inputStream atEnd
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"Modified: 11.1.1997 / 16:26:10 / cg"
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!
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contentsSpecies
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"return the kind of collection I should return when asked
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for multiple elements."
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^ inputStream contentsSpecies
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"Created: 11.1.1997 / 16:23:22 / cg"
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! !
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472
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!FilteringStream class methodsFor:'documentation'!
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version
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474
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^ '$Header: /cvs/stx/stx/libbasic2/FilteringStream.st,v 1.3 1997-01-11 15:50:52 cg Exp $'
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! !
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