Initial revision

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@8 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/weakref.rb

@@ -0,0 +1,70 @@
+# Weak Reference class that does not bother GCing.
+#
+# Usage:
+#   foo = Object.new
+#   foo.hash
+#   foo = WeakRef.new(foo)
+#   foo.hash
+#   ObjectSpace.garbage_collect
+#   foo.hash	# => Raises WeakRef::RefError (because original GC'ed)
+
+require "delegate"
+
+class WeakRef<Delegater
+
+  Exception :RefError
+
+  ID_MAP =  {}
+  ID_REV_MAP =  {}
+  ObjectSpace.add_finalizer(lambda{|id|
+			      rid = ID_MAP[id]
+			      if rid
+				ID_REV_MAP[rid] = nil
+				ID_MAP[id] = nil
+			      end
+			      rid = ID_REV_MAP[id]
+			      if rid
+				ID_REV_MAP[id] = nil
+				ID_MAP[rid] = nil
+			      end
+			    })
+			    
+  def initialize(orig)
+    super
+    @id = orig.id
+    ObjectSpace.call_finalizer orig
+    ID_MAP[@id] = self.id
+    ID_REV_MAP[self.id] = @id
+  end
+
+  def __getobj__
+    unless ID_MAP[@id]
+      $@ = caller(1)
+      $! = RefError.new("Illegal Reference - probably recycled")
+      raise
+    end
+    ObjectSpace.id2ref(@id)
+#    ObjectSpace.each_object do |obj|
+#      return obj if obj.id == @id
+#    end
+  end
+
+  def weakref_alive?
+    if ID_MAP[@id]
+      true
+    else
+      false
+    end
+  end
+
+  def []
+    __getobj__
+  end
+end
+
+foo = Object.new
+p foo.hash
+foo = WeakRef.new(foo)
+p foo.hash
+ObjectSpace.garbage_collect
+p foo.hash