"{ Package: 'squeak:petitparser' }"

PPDelegateParser subclass:#PPMemoizedParser
	instanceVariableNames:'stream buffer'
	classVariableNames:''
	poolDictionaries:''
	category:'PetitParser-Parsers'
!

PPMemoizedParser comment:'A memoized parser, for refraining redundant computations.
Instance Variables:
	stream	<PositionableStream>	The stream of the associated memento objects.
	buffer	<Array of: PPMemento>	The buffer of memento objects.
'
!


!PPMemoizedParser methodsFor:'operations'!

memoized
	"Ther is no point in memoizing more than once."

	^ self
! !

!PPMemoizedParser methodsFor:'parsing'!

parseOn: aStream
	| memento |
	stream == aStream
		ifFalse: [ self reset: aStream ].
	memento := (buffer at: stream position + 1)
		ifNil: [ buffer at: stream position + 1 put: PPMemento new ].
	memento position isNil
		ifTrue: [
			memento result: (stream size - stream position + 2 < memento count
				ifTrue: [ PPFailure message: 'overflow' at: stream position ]
				ifFalse: [ memento increment. parser parseOn: stream ]).
			memento position: stream position ]
		ifFalse: [ stream position: memento position ].
	^ memento result
! !

!PPMemoizedParser methodsFor:'private'!

reset: aStream
	stream := aStream.
	buffer := Array new: aStream size + 1
! !

!PPMemoizedParser class methodsFor:'documentation'!

version_SVN
    ^ '$Id: PPMemoizedParser.st,v 1.1 2011-08-18 18:56:17 cg Exp $'
! !