make library thread save by replacing autoloads with requires

add support for ruby 2.0

Add handling for BasicObject in ruby 1.8/1.9 implementation

Author: Brian Durand

HISTORY.txt

@@ -1,3 +1,8 @@
+1.0.3
+
+- Support Ruby 2.0 WeakRef implementation
+- Replace autoload with require to make library thread safe
+
 1.0.2
 
 - Fix mock object used for testing (Burgestrand)

MIT_LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2011 Brian Durand
+Copyright (c) 2013 Brian Durand
 
 Permission is hereby granted, free of charge, to any person obtaining
 a copy of this software and associated documentation files (the

README.rdoc

@@ -33,3 +33,8 @@ Ruby does come with the WeakRef class in the standard library. However, there ar
 2. YARV 1.9 - WeakRef is unsafe to use because the garbage collector can run in a different system thread than a thread allocating memory. This exposes a bug where a WeakRef may end up pointing to a completely different object than it originally referenced.
 3. Jruby and IronRuby - Jruby and IronRuby using the Ruby 1.8 libraries suffers from the same performance issue with the Delegator class. Furthermore, these VM's don't implement the method used to load an object from the heap using an object id and so cannot use a pure Ruby method to implement weak references.
 4. Rubinius - Rubinius implements WeakRef with a lighter weight version of delegation and works very well.
+5. MRI Ruby 2.0 has a good implementation of WeakRef.
+
+= BasicObject
+
+Not that weak references will not work with MRI/REE 1.8 or YARV 1.9. References will be created, but the objects will never be stored so the reference object will always treat the object as if it is always garbage collected. BasicObject does not implement the necessary methods to maintain the reference.

VERSION

@@ -1 +1 @@
-1.0.2
+1.0.3

lib/ref.rb

@@ -1,15 +1,9 @@
 module Ref
-  autoload :AbstractReferenceValueMap, File.join(File.dirname(__FILE__), "ref", "abstract_reference_value_map.rb")
-  autoload :AbstractReferenceKeyMap, File.join(File.dirname(__FILE__), "ref", "abstract_reference_key_map.rb")
-  autoload :Mock, File.join(File.dirname(__FILE__), "ref", "mock.rb")
-  autoload :Reference, File.join(File.dirname(__FILE__), "ref", "reference.rb")
-  autoload :ReferenceQueue, File.join(File.dirname(__FILE__), "ref", "reference_queue.rb")
-  autoload :SafeMonitor, File.join(File.dirname(__FILE__), "ref", "safe_monitor.rb")
-  autoload :SoftKeyMap, File.join(File.dirname(__FILE__), "ref", "soft_key_map.rb")
-  autoload :SoftValueMap, File.join(File.dirname(__FILE__), "ref", "soft_value_map.rb")
-  autoload :StrongReference, File.join(File.dirname(__FILE__), "ref", "strong_reference.rb")
-  autoload :WeakKeyMap, File.join(File.dirname(__FILE__), "ref", "weak_key_map.rb")
-  autoload :WeakValueMap, File.join(File.dirname(__FILE__), "ref", "weak_value_map.rb")
+  require File.join(File.dirname(__FILE__), "ref", "abstract_reference_value_map.rb")
+  require File.join(File.dirname(__FILE__), "ref", "abstract_reference_key_map.rb")
+  require File.join(File.dirname(__FILE__), "ref", "reference.rb")
+  require File.join(File.dirname(__FILE__), "ref", "reference_queue.rb")
+  require File.join(File.dirname(__FILE__), "ref", "safe_monitor.rb")
 
   # Set the best implementation for weak references based on the runtime.
   if defined?(RUBY_PLATFORM) && RUBY_PLATFORM == 'java'
@@ -21,19 +15,31 @@ module Ref
       $LOAD_PATH.shift if $LOAD_PATH.first == File.dirname(__FILE__)
     end
   else
-    autoload :SoftReference, File.join(File.dirname(__FILE__), "ref", "soft_reference.rb")
+    require File.join(File.dirname(__FILE__), "ref", "soft_reference.rb")
     if defined?(RUBY_ENGINE) && RUBY_ENGINE == 'ironruby'
       # IronRuby has it's own implementation of weak references.
-      autoload :WeakReference, File.join(File.dirname(__FILE__), "ref", "weak_reference", "iron_ruby.rb")
+      require File.join(File.dirname(__FILE__), "ref", "weak_reference", "iron_ruby.rb")
     elsif defined?(RUBY_ENGINE) && RUBY_ENGINE == 'rbx'
       # If using Rubinius set the implementation to use WeakRef since it is very efficient and using finalizers is not.
-      autoload :WeakReference, File.join(File.dirname(__FILE__), "ref", "weak_reference", "weak_ref.rb")
-    elsif defined?(ObjectSpace._id2ref)
+      require File.join(File.dirname(__FILE__), "ref", "weak_reference", "weak_ref.rb")
+    elsif defined?(::ObjectSpace::WeakMap)
+      # Ruby 2.0 has a working implementation of weakref.rb backed by the new ObjectSpace::WeakMap
+      require File.join(File.dirname(__FILE__), "ref", "weak_reference", "weak_ref.rb")
+    elsif defined?(::ObjectSpace._id2ref)
       # If ObjectSpace can lookup objects from their object_id, then use the pure ruby implementation.
-      autoload :WeakReference, File.join(File.dirname(__FILE__), "ref", "weak_reference", "pure_ruby.rb")
+      require File.join(File.dirname(__FILE__), "ref", "weak_reference", "pure_ruby.rb")
     else
       # Otherwise, wrap the standard library WeakRef class
-      autoload :WeakReference, File.join(File.dirname(__FILE__), "ref", "weak_reference", "weak_ref.rb")
+      require File.join(File.dirname(__FILE__), "ref", "weak_reference", "weak_ref.rb")
     end
   end
+  
+  require File.join(File.dirname(__FILE__), "ref", "soft_key_map.rb")
+  require File.join(File.dirname(__FILE__), "ref", "soft_value_map.rb")
+  require File.join(File.dirname(__FILE__), "ref", "strong_reference.rb")
+  require File.join(File.dirname(__FILE__), "ref", "weak_key_map.rb")
+  require File.join(File.dirname(__FILE__), "ref", "weak_value_map.rb")
+  
+  # Used for testing
+  autoload :Mock, File.join(File.dirname(__FILE__), "ref", "mock.rb")
 end

lib/ref/weak_reference/pure_ruby.rb

@@ -1,8 +1,8 @@
 module Ref
   # This is a pure ruby implementation of a weak reference. It is much more
-  # efficient than the bundled WeakRef implementation because it does not
+  # efficient than the WeakRef implementation bundled in MRI 1.8 and 1.9
   # subclass Delegator which is very heavy to instantiate and utilizes a
-  # fair amount of memory under Ruby 1.8.
+  # because it does not fair amount of memory under Ruby 1.8.
   class WeakReference < Reference
 
     class ReferencePointer
@@ -26,12 +26,14 @@ def object
       private
         # Verify that the object is the same one originally set for the weak reference.
         def verify_backreferences(obj) #:nodoc:
+          return nil unless supports_backreference?(obj)
           backreferences = obj.instance_variable_get(:@__weak_backreferences__) if obj.instance_variable_defined?(:@__weak_backreferences__)
           backreferences && backreferences.include?(object_id)
         end
 
         # Add a backreference to the object.
         def add_backreference(obj) #:nodoc:
+          return unless supports_backreference?(obj)
           backreferences = obj.instance_variable_get(:@__weak_backreferences__) if obj.instance_variable_defined?(:@__weak_backreferences__)
           unless backreferences
             backreferences = []
@@ -42,12 +44,17 @@ def add_backreference(obj) #:nodoc:
 
         # Remove backreferences from the object.
         def remove_backreference(obj) #:nodoc:
+          return unless supports_backreference?(obj)
           backreferences = obj.instance_variable_get(:@__weak_backreferences__) if obj.instance_variable_defined?(:@__weak_backreferences__)
           if backreferences
             backreferences.dup.delete(object_id)
             obj.send(:remove_instance_variable, :@__weak_backreferences__) if backreferences.empty?
           end
         end
+        
+        def supports_backreference?(obj)
+          obj.respond_to?(:instance_variable_get) && obj.respond_to?(:instance_variable_defined?)
+        end
     end
 
     @@weak_references = {}

test/weak_reference_test.rb

@@ -43,4 +43,14 @@ def test_inspect
     GC.start
     assert ref.inspect
   end
+  
+  class TestBasicObject < Object
+    undef_method(:instance_variable_defined?)
+    undef_method(:instance_variable_get)
+  end
+  
+  def test_basic_object_does_not_throw_exception
+    obj = TestBasicObject.new
+    Ref::WeakReference.new(obj)
+  end
 end