module Concurrent::ThreadSafe::Util::Volatile

@!visibility private

Public Instance Methods

attr_volatile(*attr_names) click to toggle source

Provides volatile (in the JVM’s sense) attribute accessors implemented atop of Concurrent::AtomicReference.

Usage:

class Foo
  extend Concurrent::ThreadSafe::Util::Volatile
  attr_volatile :foo, :bar

  def initialize(bar)
    super() # must super() into parent initializers before using the volatile attribute accessors
    self.bar = bar
  end

  def hello
    my_foo = foo # volatile read
    self.foo = 1 # volatile write
    cas_foo(1, 2) # => true | a strong CAS
  end
end
# File lib/concurrent-ruby/concurrent/thread_safe/util/volatile.rb, line 33
        def attr_volatile(*attr_names)
          return if attr_names.empty?
          include(Module.new do
            atomic_ref_setup = attr_names.map {|attr_name| "@__#{attr_name} = Concurrent::AtomicReference.new"}
            initialize_copy_setup = attr_names.zip(atomic_ref_setup).map do |attr_name, ref_setup|
              "#{ref_setup}(other.instance_variable_get(:@__#{attr_name}).get)"
            end
            class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
            def initialize(*)
              super
            #{atomic_ref_setup.join('; ')}
            end

            def initialize_copy(other)
              super
            #{initialize_copy_setup.join('; ')}
            end
            RUBY_EVAL

            attr_names.each do |attr_name|
              class_eval <<-RUBY_EVAL, __FILE__, __LINE__ + 1
              def #{attr_name}
                @__#{attr_name}.get
              end

              def #{attr_name}=(value)
                @__#{attr_name}.set(value)
              end

              def compare_and_set_#{attr_name}(old_value, new_value)
                @__#{attr_name}.compare_and_set(old_value, new_value)
              end
              RUBY_EVAL

              alias_method :"cas_#{attr_name}", :"compare_and_set_#{attr_name}"
              alias_method :"lazy_set_#{attr_name}", :"#{attr_name}="
            end
          end)
        end