gistfile1.rb

require "thread"

KNOWN_ACTORS = {}
THREAD_POOL = []
GLOBAL_MUTEX = Mutex.new

Thread.abort_on_exception = true

class JRubyActor
  attr_reader :name,:block
  def initialize p_name,&block
    @name = p_name
    @block = block
    @messages = Queue.new
    @outbox = Queue.new
  end

  def deliver address,message
    actor_instance = (Symbol === address) ? KNOWN_ACTORS[address] : address
    if actor_instance
      actor_instance.push_message(message.freeze,self)
    else
      klass = Struct.new(:message,:sender,:address)
      @outbox << klass.new(message.freeze,self,address)
    end
  end

  def react
    loop do
      begin
        mail = @messages.pop(true)
        yield(mail.message,mail.sender)
      rescue
        yield(nil,nil)
      end
      deliver_pending
    end
  end

  def deliver_pending
    unless @outbox.empty?
      mail = @outbox.pop
      actor_instance = KNOWN_ACTORS[mail.address]
      if actor_instance
        actor_instance.push_message(mail.message,mail.sender)
      else
        @outbox << mail
      end
    end
  end

  def push_message message,sender
    klass = Struct.new(:message,:sender)
    @messages << klass.new(message,sender)
  end
end

def actor p_name,&block
  THREAD_POOL << Thread.new(p_name,block) do
    a = JRubyActor.new(p_name,&block)
    GLOBAL_MUTEX.synchronize do
      KNOWN_ACTORS[p_name] = a
    end
    a.instance_eval &block
  end
end