1 "{ Package: 'squeak:petitparser' }"

     2 

     3 PPDelegateParser subclass:#PPMemoizedParser

     4 	instanceVariableNames:'stream buffer'

     5 	classVariableNames:''

     6 	poolDictionaries:''

     7 	category:'PetitParser-Parsers'

     8 !

     9 

    10 PPMemoizedParser comment:'A memoized parser, for refraining redundant computations.

    11 Instance Variables:

    12 	stream	<PositionableStream>	The stream of the associated memento objects.

    13 	buffer	<Array of: PPMemento>	The buffer of memento objects.

    14 '

    15 !

    16 

    17 

    18 !PPMemoizedParser methodsFor:'operations'!

    19 

    20 memoized

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

    22 

    23 	^ self

    24 ! !

    25 

    26 !PPMemoizedParser methodsFor:'parsing'!

    27 

    28 parseOn: aStream

    29 	| memento |

    30 	stream == aStream

    31 		ifFalse: [ self reset: aStream ].

    32 	memento := (buffer at: stream position + 1)

    33 		ifNil: [ buffer at: stream position + 1 put: PPMemento new ].

    34 	memento position isNil

    35 		ifTrue: [

    36 			memento result: (stream size - stream position + 2 < memento count

    37 				ifTrue: [ PPFailure message: 'overflow' at: stream position ]

    38 				ifFalse: [ memento increment. parser parseOn: stream ]).

    39 			memento position: stream position ]

    40 		ifFalse: [ stream position: memento position ].

    41 	^ memento result

    42 ! !

    43 

    44 !PPMemoizedParser methodsFor:'private'!

    45 

    46 reset: aStream

    47 	stream := aStream.

    48 	buffer := Array new: aStream size + 1

    49 ! !

    50 

    51 !PPMemoizedParser class methodsFor:'documentation'!

    52 

    53 version_SVN

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

    55 ! !