"{ 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 $'

! !