Simple message box implementation on top of Fletch

gistfile1.dart

// Example of a simple message box.

import 'dart:collection';

class MessageBox {
  final Port _port;
  MessageBox.fromPort(this._port);

  Port get port => _port;

  factory MessageBox() {
    Channel channel = new Channel();
    Process.spawn(_serve, new Port(channel));
    return new MessageBox.fromPort(channel.receive());
  }

  void send(message) {
    _port.sendMultiple([_SEND, message]);
  }

  receive() {
    Channel channel = new Channel();
    _port.sendMultiple([_RECEIVE, new Port(channel)]);
    return channel.receive();
  }

  static const int _SEND = 0;
  static const int _RECEIVE = 1;

  static void _serve(Port port) {
    Queue receivers = new Queue();
    Queue messages = new Queue();

    Channel channel = new Channel();
    port.send(new Port(channel));

    while (true) {
      List command = channel.receive();
      var operation = command[0];
      if (operation == _SEND) {
        var message = command[1];
        if (receivers.isEmpty) {
          messages.add(message);
        } else {
          receivers.removeFirst().send(message);
        }
      } else if (operation == _RECEIVE) {
        var receiver = command[1];
        if (messages.isEmpty) {
          receivers.add(receiver);
        } else {
          receiver.send(messages.removeFirst());
        }
      }
    }
  }
}

void producer(port) {
  MessageBox box = new MessageBox.fromPort(port);
  for (int i = 0; i < 25; i++) box.send(i);
}

void consumer0(port) {
  MessageBox box = new MessageBox.fromPort(port);
  while (true) {
    int value = box.receive();
    print('0: $value');
  }
}

void consumer1(port) {
  MessageBox box = new MessageBox.fromPort(port);
  while (true) {
    int value = box.receive();
    print('1: $value');
  }
}

main() {
  var box = new MessageBox();
  Process.spawn(producer, box.port);
  Process.spawn(consumer0, box.port);
  Process.spawn(consumer1, box.port);
}