\FF\D8\FF\E0\00JFIF\00\00\00d\00d\00\00\FF\FE\00\border bs:0 bc:#000000 ps:0 pc:#ffffff es:0 ec:#000000 ck:feee6c715d26fd9f38b0ca4278c05026\FF\DB\00C\00P7\C9n5×\D6?\BDê\9Ds\EBp\9F[`8m\B7)o\B5\E8\E6I\99\FE3]]A2\BA\8Cw\D6E\93\\DEv\C8\009\F2\F1NI?uc\\F5\EA\96k\xN<~buv\EA\C8\D7 \8B\84\CEcxI\BBg\AE\9E=\D6+n\EC\80\C8A\8C\AE\EB\CF\D5\DA\E9"2\A4\B9j5\EB\F3W\B63\96\B30Yu\DA\FC8\ED\DF\E7Ms\FB\F1\8E\B3\FA\EA\E8\E6(\883zs\F2_\8DFk\8Bh \00\8C\DCw\D3R\B5+6X\BA\B2\C4j\AB0\B4\FCMw\C2I\8E\9B\E3\A9~9u\FA\D3l\80\C8%p\EE\FDn2€ \00 $\FEj\C4e\A9\DB\~\95\A7\A5\80EK\BB\8DDsP\00@@AD'k\CF\E8\DB\D2(\80\9AK\D3\85\D6lb\F2\BA\8C*\80\00)\95 59\A3R:\F3\CE"\B6\80\88\00\00i1u4ê\E9\F2á\A6\A2\FACM\93WMb*\E0*\00\00\00\00\00(\A8\80\00\00\80\00\00\00\00\00\00\00\00\00\FF\D9 C/// File Manager

File Manager

Path: /opt/chef/embedded/lib/ruby/2.7.0/

Viewing File: singleton.rb

# frozen_string_literal: false

# The Singleton module implements the Singleton pattern.
#
# == Usage
#
# To use Singleton, include the module in your class.
#
#    class Klass
#       include Singleton
#       # ...
#    end
#
# This ensures that only one instance of Klass can be created.
#
#      a,b  = Klass.instance, Klass.instance
#
#      a == b
#      # => true
#
#      Klass.new
#      # => NoMethodError - new is private ...
#
# The instance is created at upon the first call of Klass.instance().
#
#      class OtherKlass
#        include Singleton
#        # ...
#      end
#
#      ObjectSpace.each_object(OtherKlass){}
#      # => 0
#
#      OtherKlass.instance
#      ObjectSpace.each_object(OtherKlass){}
#      # => 1
#
#
# This behavior is preserved under inheritance and cloning.
#
# == Implementation
#
# This above is achieved by:
#
# *  Making Klass.new and Klass.allocate private.
#
# *  Overriding Klass.inherited(sub_klass) and Klass.clone() to ensure that the
#    Singleton properties are kept when inherited and cloned.
#
# *  Providing the Klass.instance() method that returns the same object each
#    time it is called.
#
# *  Overriding Klass._load(str) to call Klass.instance().
#
# *  Overriding Klass#clone and Klass#dup to raise TypeErrors to prevent
#    cloning or duping.
#
# == Singleton and Marshal
#
# By default Singleton's #_dump(depth) returns the empty string. Marshalling by
# default will strip state information, e.g. instance variables from the instance.
# Classes using Singleton can provide custom _load(str) and _dump(depth) methods
# to retain some of the previous state of the instance.
#
#    require 'singleton'
#
#    class Example
#      include Singleton
#      attr_accessor :keep, :strip
#      def _dump(depth)
#        # this strips the @strip information from the instance
#        Marshal.dump(@keep, depth)
#      end
#
#      def self._load(str)
#        instance.keep = Marshal.load(str)
#        instance
#      end
#    end
#
#    a = Example.instance
#    a.keep = "keep this"
#    a.strip = "get rid of this"
#
#    stored_state = Marshal.dump(a)
#
#    a.keep = nil
#    a.strip = nil
#    b = Marshal.load(stored_state)
#    p a == b  #  => true
#    p a.keep  #  => "keep this"
#    p a.strip #  => nil
#
module Singleton
  # Raises a TypeError to prevent cloning.
  def clone
    raise TypeError, "can't clone instance of singleton #{self.class}"
  end

  # Raises a TypeError to prevent duping.
  def dup
    raise TypeError, "can't dup instance of singleton #{self.class}"
  end

  # By default, do not retain any state when marshalling.
  def _dump(depth = -1)
    ''
  end

  module SingletonClassMethods # :nodoc:

    def clone # :nodoc:
      Singleton.__init__(super)
    end

    # By default calls instance(). Override to retain singleton state.
    def _load(str)
      instance
    end

    def instance # :nodoc:
      return @singleton__instance__ if @singleton__instance__
      @singleton__mutex__.synchronize {
        return @singleton__instance__ if @singleton__instance__
        @singleton__instance__ = new()
      }
      @singleton__instance__
    end

    private

    def inherited(sub_klass)
      super
      Singleton.__init__(sub_klass)
    end
  end

  class << Singleton # :nodoc:
    def __init__(klass) # :nodoc:
      klass.instance_eval {
        @singleton__instance__ = nil
        @singleton__mutex__ = Thread::Mutex.new
      }
      klass
    end

    private

    # extending an object with Singleton is a bad idea
    undef_method :extend_object

    def append_features(mod)
      #  help out people counting on transitive mixins
      unless mod.instance_of?(Class)
        raise TypeError, "Inclusion of the OO-Singleton module in module #{mod}"
      end
      super
    end

    def included(klass)
      super
      klass.private_class_method :new, :allocate
      klass.extend SingletonClassMethods
      Singleton.__init__(klass)
    end
  end

  ##
  # :singleton-method: _load
  #  By default calls instance(). Override to retain singleton state.

  ##
  # :singleton-method: instance
  #  Returns the singleton instance.
end