Redesigning with Traits
- 1. Redesigning with Traits The Nile Stream trait-based Library Damien Cassou1 Stéphane Ducasse1 Roel Wuyts2 1LISTIC, University of Savoie, France 2IMEC, Leuven and Université Libre de Bruxelles European Smalltalk User Group, 2007
- 2. Outline Context Traits Problems Streams Nile Implementation Results Conclusion Further work D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 2 / 19
- 3. Context Outline Context Traits Problems Streams Nile Implementation Results Conclusion Further work D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 3 / 19
- 4. Context Traits Traits Introduction Traits • group of reusable methods • implemented and required methods • conflict management • implemented in Perl 6, Fortress, Scala, Smalltalk D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 4 / 19
- 5. Context Traits Trait sample > >= <= between:and: < = TMagnitude < = ... String < = ... Number < = ... Date • TMagnitude offers four methods and requires two • A class uses traits and implements required methods D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 5 / 19
- 6. Context Problems Problems Observation Never used to design framemorks/libraries from scratch Questions • ideal trait granularity? • how much code reuse? • trait or class? • limits, constraints, problems? D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 6 / 19
- 7. Context Problems Designing a New Trait-based Stream Library Solution • development of an adapted project • choosing the stream library Needs • compatibility with ANSI Smalltalk • compatibility with the current Squeak implementation • speed efficient D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 7 / 19
- 8. Context Problems Streams Streams Streams are used to read and write data sequentially in collections, files and network sockets. Reading • next • next: • peek Writing • nextPut: • nextPutAll: • next:put: Positioning • position: • reset • setToEnd Why streams ? • naturally modeled using multiple inheritance • existing implementations (some of them trait-based) • complex library D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 8 / 19
- 9. Context Streams Squeak Implementation atEnd close contents do: flush next next: next:put: nextPut: nextPutAll: upToEnd Stream atEnd contents isEmpty next: peek position position: reset setToEnd skip: upTo: upToEnd collection position readLimit Positionable Stream next next: nextPut: size upTo: upToEnd ReadStream contents flush next nextPut: nextPutAll: position: reset size space cr writeLimit WriteStream contents next next: ReadWriteStream atEnd close flush fullName next next: nextPut: nextPutAll: peek position position: reset size rwmode name fileID buffer1 FileStream • everything in the Stream class • methods disabled • reimplemented methods • methods reactivated • files inherit from collections D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 9 / 19
- 10. Context Streams Schärli’s Refactoring OOPSLA 2003 flush close TStreamCommon contents: last originalContents atEnd isEmpty position: reset resetContents setToEnd skip: error: position privatePosition: collection collection: readLimit readLimit: TStreamPositionable position: collection collection: readLimit: TStreamReadWrite Common nextMatchFor: upToEnd do: next: atEnd next TStreamReadable next next: peek peekFor: size upTo: upToEnd position collection position: readLimit: skip: TStreamReadable Positionable nextPutAll: nextPut: error: TStreamWriteable resetToStart nextPut: size position position: skip: collection collection: readLimit readLimit: writeLimit writeLimit: TStreamWriteable Positionable StreamTop collection position readLimit StreamPositionable Stream StreamReadStream close closed contents writeLimit StreamReadWrite Stream -{#size} writeLimit StreamWriteStream Only a refactoring • no positioning for files • peek depends on position and collection • . . . D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 10 / 19
- 11. Nile Outline Context Traits Problems Streams Nile Implementation Results Conclusion Further work D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 11 / 19
- 12. Nile Implementation Nile overview Core Collection-based Streams File-based Streams Character writing Decoders D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 12 / 19
- 13. Nile Implementation Collection-based Streams collection position ReadableCollectionStream collection position writeLimit Writeable CollectionStream collection position writeLimit ReadWriteCollectionStream do: nextMatchFor: next: peekFor: skip: skipTo: upTo: upToEnd upToElementSatisfying: atEnd next peek outputCollectionClass TGettableStream atEnd atStart close isEmpty position: reset setToEnd position setPosition: size TPositionableStream nextPutAll: next:put: print: flush nextPut: TPuttableStream contents size collection setCollection: TCollectionStream nextPut: size writeLimit writeLimit: TWriteableCollection Stream -{#size} Core next peek skip: outputCollectionClass TReadableCollectionStream • a trait per basic functionality • traits for collections and one class for each original Squeak class D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 13 / 19
- 14. Nile Implementation Other Implemented Libraries Core Collection-based Streams File-based Streams Character writing Decoders Other Implemented Libraries Files file-based streams Random random number generator SharedQueue queue concurrent access Decoder pipe system to chain streams (compression, multiplexing. . . ) and many others. . . D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 14 / 19
- 15. Nile Results New Design Good Code Reuse • good code reuse : 22 classes use TGettableStream • important gain : TCharacterWriting requires implementing one method to gain 8 Better Implementation • 18% fewer methods • 15% less byte-code • not forced to use unwanted behavior Better Performance • faster execution • traits don’t prevent optimization D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 15 / 19
- 16. Nile Results Trait-related Problems Discovered • interface pollution • traits require accessors • sometimes an extra getter or setter • IDE support for traits needs improvement • difficult to visualize and navigate D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 16 / 19
- 17. Conclusion Outline Context Traits Problems Streams Nile Implementation Results Conclusion Further work D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 17 / 19
- 18. Conclusion Further work Further Work • Having an equivalent implementation? • much more entities (11 traits+classes compared to 4 classes in Squeak) • simplify using only read/write access? • lot’s of ugly code in the original implementation D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 18 / 19
- 19. Conclusion Further work Conclusion • Context • traits needed to be tested in a new project • a stream library is a good project example • Realized work • existing implementation was analyzed • new design was created • efficient implementation • problem analysis • really improves the design • needs further work D. Cassou, S. Ducasse, R. Wuyts (Savoie, Bruxelles) Redesigning with Traits ESUG 2007 19 / 19