add DRb::WeakIdConv (Bug #15711)

1 files changed, 59 insertions, 0 deletions

diff --git a/lib/drb/weakidconv.rb b/lib/drb/weakidconv.rb
new file mode 100644
index 0000000000..7f973dc8cc
--- /dev/null
+++ b/lib/drb/weakidconv.rb
@@ -0,0 +1,59 @@
+# frozen_string_literal: false
+require_relative 'drb'
+require 'monitor'
+
+module DRb
+
+  # To use WeakIdConv:
+  #
+  #  DRb.start_service(nil, nil, {:idconv => DRb::WeakIdConv.new})
+
+  class WeakIdConv < DRbIdConv
+    class WeakSet
+      include MonitorMixin
+      def initialize
+        super()
+        @immutable = {}
+        @map = ObjectSpace::WeakMap.new
+      end
+
+      def add(obj)
+        synchronize do
+          begin
+            @map[obj] = self 
+          rescue ArgumentError
+            @immutable[obj.__id__] = obj
+          end
+          return obj.__id__
+        end
+      end
+
+      def fetch(ref)
+        synchronize do
+          @immutable.fetch(ref) { 
+            @map.each { |key, _|
+              return key if key.__id__ == ref
+            }
+            raise RangeError.new("invalid reference")
+          }
+        end
+      end
+    end
+
+    def initialize()
+      super()
+      @weak_set = WeakSet.new
+    end
+
+    def to_obj(ref) # :nodoc:
+      return super if ref.nil?
+      @weak_set.fetch(ref)
+    end
+
+    def to_id(obj) # :nodoc:
+      return @weak_set.add(obj)
+    end
+  end
+end
+
+# DRb.install_id_conv(WeakIdConv.new)