1 files changed, 100 insertions, 0 deletions
diff --git a/ruby_1_8_6/lib/weakref.rb b/ruby_1_8_6/lib/weakref.rb
new file mode 100644
index 0000000000..591819c948
--- /dev/null
+++ b/ruby_1_8_6/lib/weakref.rb
@@ -0,0 +1,100 @@
+require "delegate"
+
+# WeakRef is a class to represent a reference to an object that is not seen by
+# the tracing phase of the garbage collector.  This allows the referenced
+# object to be garbage collected as if nothing is referring to it. Because
+# WeakRef delegates method calls to the referenced object, it may be used in
+# place of that object, i.e. it is of the same duck type.
+#
+# Usage:
+#
+#   foo = Object.new
+#   foo = Object.new
+#   p foo.to_s			# original's class
+#   foo = WeakRef.new(foo)
+#   p foo.to_s			# should be same class
+#   ObjectSpace.garbage_collect
+#   p foo.to_s			# should raise exception (recycled)
+class WeakRef<Delegator
+
+  # RefError is raised if an object cannot be referenced by a WeakRef.
+  class RefError<StandardError
+  end
+
+  @@id_map =  {}                # obj -> [ref,...]
+  @@id_rev_map =  {}            # ref -> obj
+  @@final = lambda{|id|
+    __old_status = Thread.critical
+    Thread.critical = true
+    begin
+      rids = @@id_map[id]
+      if rids
+	for rid in rids
+	  @@id_rev_map.delete(rid)
+	end
+	@@id_map.delete(id)
+      end
+      rid = @@id_rev_map[id]
+      if rid
+	@@id_rev_map.delete(id)
+	@@id_map[rid].delete(id)
+	@@id_map.delete(rid) if @@id_map[rid].empty?
+      end
+    ensure
+      Thread.critical = __old_status
+    end
+  }
+
+  # Create a new WeakRef from +orig+.
+  def initialize(orig)
+    super
+    __setobj__(orig)
+  end
+
+  # Return the object this WeakRef references. Raises RefError if the object
+  # has been garbage collected.  The object returned is the object to which
+  # method calls are delegated (see Delegator).
+  def __getobj__
+    unless @@id_rev_map[self.__id__] == @__id
+      raise RefError, "Illegal Reference - probably recycled", caller(2)
+    end
+    begin
+      ObjectSpace._id2ref(@__id)
+    rescue RangeError
+      raise RefError, "Illegal Reference - probably recycled", caller(2)
+    end
+  end
+
+  def __setobj__(obj)
+    @__id = obj.__id__
+    __old_status = Thread.critical
+    begin
+      Thread.critical = true
+      unless @@id_rev_map.key?(self)
+        ObjectSpace.define_finalizer obj, @@final
+        ObjectSpace.define_finalizer self, @@final
+      end
+      @@id_map[@__id] = [] unless @@id_map[@__id]
+    ensure
+      Thread.critical = __old_status
+    end
+    @@id_map[@__id].push self.__id__
+    @@id_rev_map[self.__id__] = @__id
+  end
+
+  # Returns true if the referenced object still exists, and false if it has
+  # been garbage collected.
+  def weakref_alive?
+    @@id_rev_map[self.__id__] == @__id
+  end
+end
+
+if __FILE__ == $0
+  require 'thread'
+  foo = Object.new
+  p foo.to_s			# original's class
+  foo = WeakRef.new(foo)
+  p foo.to_s			# should be same class
+  ObjectSpace.garbage_collect
+  p foo.to_s			# should raise exception (recycled)
+end