[Pharo-project] Xtreams : first embryonary port on Squeak

Nicolas Cellier nicolas.cellier.aka.nice at gmail.com
Sat Oct 9 18:33:23 EDT 2010


So, I started a quick port of VW Xtreams to Squeak this evening.
Only the Xtreams-Core and the trivial Xtreams-Terminals (no
file/pipe/socket/pointer).
You'll find code at http://www.squeaksource.com/XTream.
My previous experimental Xtream project has been renamed SqueaXTream
to reduce confusion, but still sits in the same project.
Please find my report below.

cheers

Nicolas

--------------------- REPORT  ---------------------

THE CONTENTS:

This first port is made of 3 packages
- Xtreams-Core
- Xtreams-Terminals
- Xtreams-VWCompatible
Plus 2 tests
- Xtreams-CoreTests
- Xtreams-TerminalsTests
Please notice I removed one hyphen from test package names for MC compatibility.

THE PROCEDURE:

I didn't use FileOut30 not any more advanced tool, but just a simple
copy/paste strategy.
This gave me a chance to do a fast review of code.
For porting the future evolutions of VW Xtreams, more advanced tools
will be necessary, the manual approach does not scale.

THE MODIFICATIONS:

The changes I made are quite restricted, which indicates that Xtreams
is not that hard to port.
Main changes are due to lack of namespace in Squeak:
- I added a XT prefix to every Xtreams classes (no Namespace in Squeak)
- I added XTPools, a SharedPool for holding the single Xtreams
namespace variable DefaultBufferSize
- I transformed class SharedVariables into class variables and added
proper class side initialization for these in XTWriteStream

For the rest, I tried to not change Xtreams contents. but rather did
implement VW compatible messages when possible in the
Xtreams-VWCompatible package when they did not exist in Squeak.
These message are a full rewrite and are also released under MIT license.
The few exceptions are:
- I modified originator -> self originator in XTIncomplete.
- I changed the senders of #newInFixedSpace: to rather send an #error:
'not implemented in Squeak' in XTRecyclingBuffer
- I replaced #waitIfCurtailedSignal/#signal with a #critical: section
in XTRecyclingBuffer
- I replaced  Core.Timer after:do: with self after:do: in Xtreams-CoreTests

A DISCUSSION OF TECHNICAL DETAILS:

I first attempted to replace #growToAtLeast: with #grownBy: because
Squeak become: is notoriously inefficient.
But obviously, this did not work, the tests rely on destination
preserving its identity.
This clearly is going to degrade micro benchmarks when the destination
collection capacity is not well adjusted in advance.
I think we should discuss this particular point. Is identity
preservation absolutely required, or just convenient ?

THE STATUS OF TESTS:

Tests do not all pass. There seems to be a bug in Squeak
#replace:from:to:with: when the replacement is the collection itself,
moved to the right (this is with a COG VM).

THE FUTURE:

I will probably continue porting with reduced activity, so I invite
any interested person to help. Right now, the project is world
writeable, code commited here falling under MIT license.




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