Class: Concurrent::Synchronization::Object

Inherits:
ObjectImplementation
  • Object
show all
Defined in:
lib/concurrent/synchronization/object.rb

Overview

Abstract object providing final, volatile, ans CAS extensions to build other concurrent abstractions.

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Object

Has to be called by children.



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# File 'lib/concurrent/synchronization/object.rb', line 36

def initialize
  super
  __initialize_atomic_fields__
end

Class Method Details

.atomic_attribute?(name) ⇒ true, false

Returns is the attribute with name atomic?.

Returns:

  • (true, false) —

    is the attribute with name atomic?



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# File 'lib/concurrent/synchronization/object.rb', line 157

def self.atomic_attribute?(name)
  atomic_attributes.include? name
end

.atomic_attributes(inherited = true) ⇒ ::Array<Symbol>

Returns defined volatile with CAS fields on this class.

Parameters:

  • inherited (true, false) (defaults to: true) —

    should inherited volatile with CAS fields be returned?

Returns:

  • (::Array<Symbol>) —

    Returns defined volatile with CAS fields on this class.



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# File 'lib/concurrent/synchronization/object.rb', line 151

def self.atomic_attributes(inherited = true)
  @__atomic_fields__ ||= []
  ((superclass.atomic_attributes if superclass.respond_to?(:atomic_attributes) && inherited) || []) + @__atomic_fields__
end

.attr_atomic(*names) ⇒ ::Array<Symbol>

Creates methods for reading and writing to a instance variable with volatile (Java) semantic as attr_volatile does. The instance variable should be accessed oly through generated methods. This method generates following methods: value, value=(new_value) #=> new_value, swap_value(new_value) #=> old_value, compare_and_set_value(expected, value) #=> true || false, update_value(&block).

Parameters:

  • names (::Array<Symbol>) —

    of the instance variables to be volatile with CAS.

Returns:

  • (::Array<Symbol>) —

    names of defined method names.



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# File 'lib/concurrent/synchronization/object.rb', line 116

def self.attr_atomic(*names)
  @__atomic_fields__ ||= []
  @__atomic_fields__ += names
  safe_initialization!
  define_initialize_atomic_fields

  names.each do |name|
    ivar = :"@Atomic#{name.to_s.gsub(/(?:^|_)(.)/) { $1.upcase }}"
    class_eval <<-RUBY, __FILE__, __LINE__ + 1
      def #{name}
        #{ivar}.get
      end

      def #{name}=(value)
        #{ivar}.set value
      end

      def swap_#{name}(value)
        #{ivar}.swap value
      end

      def compare_and_set_#{name}(expected, value)
        #{ivar}.compare_and_set expected, value
      end

      def update_#{name}(&block)
        #{ivar}.update(&block)
      end
    RUBY
  end
  names.flat_map { |n| [n, :"#{n}=", :"swap_#{n}", :"compare_and_set_#{n}", :"update_#{n}"] }
end

.attr_volatile(*names) ⇒ ::Array<Symbol>

Creates methods for reading and writing (as attr_accessor does) to a instance variable with volatile (Java) semantic. The instance variable should be accessed only through generated methods.

Parameters:

  • names (::Array<Symbol>) —

    of the instance variables to be volatile

Returns:

  • (::Array<Symbol>) —

    names of defined method names




# File 'lib/concurrent/synchronization/object.rb', line 28

.ensure_safe_initialization_when_final_fields_are_present ⇒ true

For testing purposes, quite slow. Injects assert code to new method which will raise if class instance contains any instance variables with CamelCase names and isn't safe_initialization?.

Returns:

  • (true)

Raises:

  • when offend found



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# File 'lib/concurrent/synchronization/object.rb', line 77

def self.ensure_safe_initialization_when_final_fields_are_present
  Object.class_eval do
    def self.new(*args, &block)
      object = super(*args, &block)
    ensure
      has_final_field = object.instance_variables.any? { |v| v.to_s =~ /^@[A-Z]/ }
      if has_final_field && !safe_initialization?
        raise "there was an instance of #{object.class} with final field but not marked with safe_initialization!"
      end
    end
  end
  true
end

.safe_initialization! ⇒ true

By calling this method on a class, it and all its children are marked to be constructed safely. Meaning that all writes (ivar initializations) are made visible to all readers of newly constructed object. It ensures same behaviour as Java's final fields.

Examples:

class AClass < Concurrent::Synchronization::Object
  safe_initialization!

  def initialize
    @AFinalValue = 'value' # published safely, does not have to be synchronized
  end
end

Returns:

  • (true) 


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# File 'lib/concurrent/synchronization/object.rb', line 53

def self.safe_initialization!
  # define only once, and not again in children
  return if safe_initialization?

  # @!visibility private
  def self.new(*args, &block)
    object = super(*args, &block)
  ensure
    object.full_memory_barrier if object
  end

  @safe_initialization = true
end

.safe_initialization? ⇒ true, false

Returns if this class is safely initialized.

Returns:

  • (true, false) —

    if this class is safely initialized.



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# File 'lib/concurrent/synchronization/object.rb', line 68

def self.safe_initialization?
  @safe_initialization = false unless defined? @safe_initialization
  @safe_initialization || (superclass.respond_to?(:safe_initialization?) && superclass.safe_initialization?)
end