smalltalk_ffi

=== Smalltalk FFI

The MagLev VM is a GemStone VM that has been enhanced to run Ruby as well
as Smalltalk. GemStone provides a set of <tt>.rb</tt> files that allow Ruby
code to call into the GemStone/Smalltalk evnironment.

==== Create Ruby Wrappers for GemStone/Smalltalk Classes

To generate the ruby wrappers:

  $ cd $MAGLEV_HOME
  $ rake stwrappers

The wrapper files are placed in
<tt>$MAGLEV_HOME/lib/ruby/site_ruby/1.8/smalltalk</tt>

==== Using the Wrappers

To use a wrapper, simply require the appropriate file and call the methods:

  require 'smalltalk/System'
  puts Smalltalk::System._st_inTransaction

  require 'smalltalk/SymbolSet'
  s = Smalltalk::SymbolSet._st_new(10)

  require 'smalltalk/IdentityBag'
  b = Smalltalk::IdentityBag._st_new(10)
  puts b._st_hash
  puts b._st_getIndexInfo

==== Conventions

The naming conventions of the files, methods and classes have a Smalltalk
flavor to remind you that they are Smalltalk objects and follow Smalltalk
semantics rather than Ruby semantics.


* Do not use ruby <tt>new</tt> to initialize objects via the Smalltalk
  FFI.  Smalltalk objects need to be initialized with a send of
  <tt>_st_new</tt>.

* In order to call a method defined in a super class, the wrapper file for
  the super class must also be loaded into the system.  The wrapper files
  are generated with the proper includes.  E.g., <tt>Bag.rb</tt> contains;

    require 'smalltalk/UnorderedCollection'
    require 'smalltalk/Collection'
    require 'smalltalk/Object'