1 files changed, 41 insertions, 0 deletions
diff --git a/lib/roo/helpers/weak_instance_cache.rb b/lib/roo/helpers/weak_instance_cache.rb
new file mode 100644
index 0000000..db26de1
--- /dev/null
+++ b/lib/roo/helpers/weak_instance_cache.rb
@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require "weakref"
+
+module Roo
+  module Helpers
+    module WeakInstanceCache
+      private
+
+      def instance_cache(key)
+        object = nil
+
+        if instance_variable_defined?(key) && (ref = instance_variable_get(key)) && ref.weakref_alive?
+          begin
+            object = ref.__getobj__
+          rescue => e
+            unless (defined?(::WeakRef::RefError) && e.is_a?(::WeakRef::RefError)) || (defined?(RefError) && e.is_a?(RefError))
+              raise e
+            end
+          end
+        end
+
+        unless object
+          object = yield
+          ObjectSpace.define_finalizer(object, instance_cache_finalizer(key))
+          instance_variable_set(key, WeakRef.new(object))
+        end
+
+        object
+      end
+
+      def instance_cache_finalizer(key)
+        proc do |object_id|
+          if instance_variable_defined?(key) && (ref = instance_variable_get(key)) && (!ref.weakref_alive? || ref.__getobj__.object_id == object_id)
+            remove_instance_variable(key)
+          end
+        end
+      end
+    end
+  end
+end