Stream subclass:#FilteringStream

	instanceVariableNames:'inputStream outputStream filter unbound'

	classVariableNames:''

	poolDictionaries:''

	category:'Streams'

!

!FilteringStream  class methodsFor:'documentation'!

examples

"

  filter random numbers:

    |in filter|

    in := Random new.

    filter := FilteringLineStream basicNew.

    filter inputStream:in.

    filter filter:[:num | ((num >= 0.5) and:[num <= 0.6]) ifTrue:[num] ifFalse:[nil]].

    20 timesRepeat:[

        Transcript showCR:(filter next printString).

    ]

  filtering prime numbers:

    |num generator primeFilter addFilter|

    num := 1.

    generator := Plug new.

    generator respondTo:#next

                   with:[num := num + 1. num].

    generator respondTo:#atEnd

                   with:[false].

    addFilter := [:prime | |newFilter|

        newFilter := FilteringLineStream basicNew.

        newFilter unbound:true.

        newFilter filter:[:num | (num \\ prime) == 0 ifTrue:[

                                    nil

                                 ] ifFalse:[

                                    num

                                 ]

                         ].

        newFilter inputStream:primeFilter.

        primeFilter := newFilter

    ].

    addFilter value:2.

    primeFilter inputStream:generator.

    100000 timesRepeat:[

        |nextPrime|

        nextPrime := primeFilter next.

        addFilter value:nextPrime.

        Transcript showCR:nextPrime.

    ]

"

! !

!FilteringStream methodsFor:'access - pull-reading'!

filterUpToEnd

    "pull input from inputStream up to the end,

     push it filtered into the outputStream"

    [inputStream atEnd] whileFalse:[

        self nextPut:(inputStream next)

    ].

    "Modified: 2.7.1996 / 21:02:49 / cg"

    "Created: 2.7.1996 / 21:06:42 / cg"

!

next

    "pull input from inputStream and

     push it filtered into the outputStream"

    |input output|

    [inputStream atEnd] whileFalse:[

        input := inputStream next.

        output := filter value:input.

        output notNil ifTrue:[

            ^ output.

        ].

    ].

    ^ nil

    "Created: 2.7.1996 / 21:09:58 / cg"

! !

!FilteringStream methodsFor:'access - push-writing'!

nextPut:something

    "push something through the filter"

    |output|

    output := filter value:something.

    output notNil ifTrue:[

        outputStream nextPut:output

    ]

    "Created: 2.7.1996 / 21:07:58 / cg"

! !

!FilteringStream methodsFor:'accessing'!

filter

    "return the filter"

    ^ filter

    "Modified: 2.7.1996 / 21:03:36 / cg"

    "Created: 2.7.1996 / 21:06:42 / cg"

!

filter:something

    "set the filter"

    filter := something.

    "Modified: 2.7.1996 / 21:03:40 / cg"

    "Created: 2.7.1996 / 21:06:42 / cg"

!

inputStream

    "return the inputStream"

    ^ inputStream

    "Modified: 2.7.1996 / 21:03:43 / cg"

    "Created: 2.7.1996 / 21:06:42 / cg"

!

inputStream:something

    "set the inputStream"

    inputStream := something.

    "Modified: 2.7.1996 / 21:03:46 / cg"

    "Created: 2.7.1996 / 21:06:42 / cg"

!

outputStream

    "return the outputStream"

    ^ outputStream

    "Modified: 2.7.1996 / 21:03:49 / cg"

    "Created: 2.7.1996 / 21:06:42 / cg"

!

outputStream:something

    "set the outputStream"

    outputStream := something.

    "Modified: 2.7.1996 / 21:03:52 / cg"

    "Created: 2.7.1996 / 21:06:42 / cg"

!

unbound

    "return unbound"

    ^ unbound

    "Created: 2.7.1996 / 21:25:40 / cg"

!

unbound:something

    "set unbound"

    unbound := something.

    "Created: 2.7.1996 / 21:25:40 / cg"

! !

!FilteringStream methodsFor:'queries'!

atEnd

    unbound ifTrue:[^ false].

    ^ inputStream atEnd

    "Created: 2.7.1996 / 21:19:51 / cg"

    "Modified: 2.7.1996 / 21:25:53 / cg"

! !

!FilteringStream  class methodsFor:'documentation'!

version

    ^ '$Header: /cvs/stx/stx/libbasic2/FilteringStream.st,v 1.1 1996-07-02 19:28:43 cg Exp $'

! !