"{ Package: 'stx:goodies/xtreams/substreams' }"

"{ NameSpace: Xtreams }"

WriteSubstream subclass:#PositionWriteSubstream

	instanceVariableNames:'position'

	classVariableNames:''

	poolDictionaries:''

	category:'Xtreams-Substreams'

!

PositionWriteSubstream comment:'This is an abstract substreams that keeps track of its own position and allows positioning if the underlying stream is positionable.

Instance Variables

	position	<Integer> current position within the substream

'

!

!PositionWriteSubstream methodsFor:'accessing'!

insert: anInteger from: aSequenceableCollection at: startIndex

	[destination insert: anInteger from: aSequenceableCollection at: startIndex] on: Incomplete do: [:incomplete |

		position := position + incomplete count.

		incomplete pass].

	position := position + anInteger.

	^anInteger

!

put: anObject

	| object |

	object := destination put: anObject.

	position := position + 1.

	^object

!

write: anInteger from: aSequenceableCollection at: startIndex

	[destination write: anInteger from: aSequenceableCollection at: startIndex] on: Incomplete do: [:incomplete |

		position := position + incomplete count.

		incomplete pass].

	position := position + anInteger.

	^anInteger

! !

!PositionWriteSubstream methodsFor:'initialize-release'!

on: aDestination

	super on: aDestination.

	position := 0

! !

!PositionWriteSubstream methodsFor:'seeking'!

++ anInteger

	| count |

	anInteger < 0 ifTrue: [ ^self -- anInteger negated ].

	count := self available min: anInteger.

	count := [destination ++ count. count] on: Incomplete do: [ :ex | ex count ].

	position := position + count.

	count < anInteger ifTrue: [destinationAtEnd := true. (Incomplete count: count) raise].

	^anInteger

!

-- anInteger

	| count |

	anInteger < 0 ifTrue: [ ^self ++ anInteger negated ].

	count := anInteger min: position.

	count := [destination -- count. count] on: Incomplete do: [ :ex | ex count ].

	position := position - count.

	count < anInteger ifTrue: [(Incomplete count: count) raise].

	anInteger isZero ifFalse: [destinationAtEnd := false].

	^anInteger

!

-= anInteger

	position := self length - anInteger max: 0.

	^destination -= anInteger.

!

length

	^destination available + position

!

position

	^position

!

position: anInteger

	| available adjustment |

	self isPositionable ifFalse: [self error: 'This stream is not positionable.'].

	anInteger < 0 ifTrue: [Incomplete zero raise].

	available := anInteger min: self length.

	adjustment := available - position.

	adjustment positive

		ifTrue: [ destination ++ adjustment ]

		ifFalse: [ destination -- adjustment negated ].

	position := available.

	available = anInteger ifTrue: [^anInteger].

	(Incomplete count: available) raise

! !

!PositionWriteSubstream methodsFor:'testing'!

isPositionable

	^destination isPositionable

! !

!PositionWriteSubstream class methodsFor:'documentation'!

version_SVN

    ^ '$Id$'

! !