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bin/gems/concurrent-ruby-1.3.5/lib/concurrent-ruby/concurrent/concern/dereferenceable.rb

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+module Concurrent
+  module Concern
+
+    # Object references in Ruby are mutable. This can lead to serious problems when
+    # the `#value` of a concurrent object is a mutable reference. Which is always the
+    # case unless the value is a `Fixnum`, `Symbol`, or similar "primitive" data type.
+    # Most classes in this library that expose a `#value` getter method do so using the
+    # `Dereferenceable` mixin module.
+    #
+    # @!macro copy_options
+    module Dereferenceable
+      # NOTE: This module is going away in 2.0. In the mean time we need it to
+      # play nicely with the synchronization layer. This means that the
+      # including class SHOULD be synchronized and it MUST implement a
+      # `#synchronize` method. Not doing so will lead to runtime errors.
+
+      # Return the value this object represents after applying the options specified
+      # by the `#set_deref_options` method.
+      #
+      # @return [Object] the current value of the object
+      def value
+        synchronize { apply_deref_options(@value) }
+      end
+      alias_method :deref, :value
+
+      protected
+
+      # Set the internal value of this object
+      #
+      # @param [Object] value the new value
+      def value=(value)
+        synchronize{ @value = value }
+      end
+
+      # @!macro dereferenceable_set_deref_options
+      #   Set the options which define the operations #value performs before
+      #   returning data to the caller (dereferencing).
+      #
+      #   @note Most classes that include this module will call `#set_deref_options`
+      #     from within the constructor, thus allowing these options to be set at
+      #     object creation.
+      #
+      #   @param [Hash] opts the options defining dereference behavior.
+      #   @option opts [String] :dup_on_deref (false) call `#dup` before returning the data
+      #   @option opts [String] :freeze_on_deref (false) call `#freeze` before returning the data
+      #   @option opts [String] :copy_on_deref (nil) call the given `Proc` passing
+      #     the internal value and returning the value returned from the proc
+      def set_deref_options(opts = {})
+        synchronize{ ns_set_deref_options(opts) }
+      end
+
+      # @!macro dereferenceable_set_deref_options
+      # @!visibility private
+      def ns_set_deref_options(opts)
+        @dup_on_deref = opts[:dup_on_deref] || opts[:dup]
+        @freeze_on_deref = opts[:freeze_on_deref] || opts[:freeze]
+        @copy_on_deref = opts[:copy_on_deref] || opts[:copy]
+        @do_nothing_on_deref = !(@dup_on_deref || @freeze_on_deref || @copy_on_deref)
+        nil
+      end
+
+      # @!visibility private
+      def apply_deref_options(value)
+        return nil if value.nil?
+        return value if @do_nothing_on_deref
+        value = @copy_on_deref.call(value) if @copy_on_deref
+        value = value.dup if @dup_on_deref
+        value = value.freeze if @freeze_on_deref
+        value
+      end
+    end
+  end
+end