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Concurrent::Synchronization::Object

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

Public Class Methods

attr_atomic(*names) click to toggle source

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)`. @param [Array<Symbol>] names of the instance variables to be volatile with CAS. @return [Array<Symbol>] names of defined method names.

# File lib/concurrent/synchronization/object.rb, line 90
def self.attr_atomic(*names)
  @volatile_cas_fields ||= []
  @volatile_cas_fields += names
  safe_initialization!
  define_initialize_volatile_with_cas

  names.each do |name|
    ivar = :"@Atomic#{name.to_s.gsub(/(?:^|_)(.)/) { $1.upcase }}"
    class_eval             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, __FILE__, __LINE__ + 1
  end
  names.flat_map { |n| [n, :"#{n}=", :"swap_#{n}", :"compare_and_set_#{n}", :"update_#{n}"] }
end
ensure_safe_initialization_when_final_fields_are_present() click to toggle source

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?}.

# File lib/concurrent/synchronization/object.rb, line 69
def self.ensure_safe_initialization_when_final_fields_are_present
  Object.class_eval do
    def self.new(*)
      object = super
    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
end
new(*) click to toggle source
# File lib/concurrent/synchronization/object.rb, line 52
def self.new(*)
  object = super
ensure
  object.full_memory_barrier if object
end
new() click to toggle source

Has to be called by children.

# File lib/concurrent/synchronization/object.rb, line 32
def initialize
  super
  initialize_volatile_with_cas
end
safe_initialization!() click to toggle source

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. @example

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

  def initialize
    @AFinalValue = 'value' # published safely, does not have to be synchronized
  end
end
# File lib/concurrent/synchronization/object.rb, line 48
def self.safe_initialization!
  # define only once, and not again in children
  return if safe_initialization?

  def self.new(*)
    object = super
  ensure
    object.full_memory_barrier if object
  end

  @safe_initialization = true
end
safe_initialization?() click to toggle source

@return [true, false] if this class is safely initialized.

# File lib/concurrent/synchronization/object.rb, line 62
def self.safe_initialization?
  @safe_initialization = false unless defined? @safe_initialization
  @safe_initialization || (superclass.respond_to?(:safe_initialization?) && superclass.safe_initialization?)
end
volatile_cas_fields(inherited = true) click to toggle source

@param [true,false] inherited should inherited volatile with CAS fields be returned? @return [Array<Symbol>] Returns defined volatile with CAS fields on this class.

# File lib/concurrent/synchronization/object.rb, line 125
def self.volatile_cas_fields(inherited = true)
  @volatile_cas_fields ||= []
  ((superclass.volatile_cas_fields if superclass.respond_to?(:volatile_cas_fields) && inherited) || []) +
      @volatile_cas_fields
end

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