"{ Package: 'stx:libbasic2' }"

"{ NameSpace: Smalltalk }"

PeekableStream subclass:#MultiReadStream

	instanceVariableNames:'streamStack'

	classVariableNames:''

	poolDictionaries:''

	category:'Streams-Misc'

!

!MultiReadStream class methodsFor:'documentation'!

documentation

"

    Stacked streams. At any time, another stream can be stacked onto

    a stream stack. Making this stream's contents to be returned before the

    rest. To the stream reader, this looks like a single stream delivering the

    embedded stream contents sequentially.

    Useful when reading files which include each other, or to handle

    define-macro expansion in a c-parser.

    [Author:]

        Claus Gittinger

    [instance variables:]

"

    "Created: / 21-05-2010 / 14:34:48 / cg"

!

examples

"

    |s|

    s := MultiReadStream on:('abcd' readStream).

    self assert:(s peek == $a).

    self assert:(s next == $a).

    s pushInputStream:('1234' readStream).

    self assert:(s next == $1).

    self assert:(s next == $2).

    s pushInputStream:('aa' readStream).

    self assert:(s next == $a).

    self assert:(s next == $a).

    self assert:(s atEnd not).

    self assert:(s next == $3).

    self assert:(s next == $4).

    self assert:(s next == $b).

    self assert:(s next == $c).

    self assert:(s next == $d).

    self assert:(s atEnd).

    self assert:(s peek == nil).

    self assert:(s next == nil).

"

    "Created: / 21-05-2010 / 14:27:53 / cg"

! !

!MultiReadStream class methodsFor:'instance creation'!

on:aReadStream

    ^ self basicNew pushInputStream:aReadStream

    "Created: / 21-05-2010 / 14:26:03 / cg"

! !

!MultiReadStream methodsFor:'private'!

checkCurrentStreamAtEnd

    [streamStack size > 1 and:[streamStack last atEnd]] whileTrue:[

        "keep the last stream, so that the #position kludge will work"

        self popInputStream

    ].

    "Created: / 21-05-2010 / 14:30:20 / cg"

! !

!MultiReadStream methodsFor:'stream protocol'!

atEnd

    self checkCurrentStreamAtEnd.

    ^ streamStack isEmptyOrNil or:[streamStack last atEnd]

    "Created: / 21-05-2010 / 14:31:48 / cg"

!

contentsSpecies 

    "return a class of which instances will be returned, when

     parts of the collection are asked for. 

     (see upTo-kind of methods in Stream)"

    streamStack isEmptyOrNil ifTrue:[^ super contentsSpecies].

    ^ streamStack first contentsSpecies

    "Created: / 21-05-2010 / 14:44:26 / cg"

!

next

    self checkCurrentStreamAtEnd.

    streamStack isEmptyOrNil ifTrue:[^ self pastEndRead].

    ^ streamStack last next

    "Created: / 21-05-2010 / 14:31:23 / cg"

!

peek

    self checkCurrentStreamAtEnd.

    streamStack isEmptyOrNil ifTrue:[^ self pastEndRead].

    ^ streamStack last peek

    "Created: / 21-05-2010 / 14:29:06 / cg"

!

position

    "/ that's debatable !!

    "/ the code below only makes sense, if we see the multiStream as some kind of

    "/ macro-expanding c-define stream

    streamStack isEmptyOrNil ifTrue:[

        "we assume we are at the beginning"

        ^ 0

    ].

    ^ streamStack first position

    "Created: / 21-05-2010 / 14:52:40 / cg"

!

position0Based

    <resource: #obsolete>

    ^ self position

    "Created: / 21-05-2010 / 14:52:40 / cg"

!

position1Based

    <resource: #obsolete>

    ^ self position + 1

    "Created: / 21-05-2010 / 14:52:40 / cg"

!

readStream

    ^ self

    "Created: / 21-05-2010 / 14:51:05 / cg"

! !

!MultiReadStream methodsFor:'stream stacking'!

popInputStream

    streamStack removeLast

    "Created: / 21-05-2010 / 14:25:30 / cg"

!

pushInputStream:aReadStream

    streamStack isNil ifTrue:[

        streamStack := OrderedCollection new.

    ].

    streamStack add:aReadStream

    "Created: / 21-05-2010 / 14:25:17 / cg"

! !

!MultiReadStream class methodsFor:'documentation'!

version_CVS

    ^ '$Header$'

! !