text: // Copyright Joyent, Inc. and other Node contributors.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a
  // copy of this software and associated documentation files (the
  // "Software"), to deal in the Software without restriction, including
  // without limitation the rights to use, copy, modify, merge, publish,
  // distribute, sublicense, and/or sell copies of the Software, and to permit
  // persons to whom the Software is furnished to do so, subject to the
  // following conditions:
  //
  // The above copyright notice and this permission notice shall be included
  // in all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
  // NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  // USE OR OTHER DEALINGS IN THE SOFTWARE.
  
  var domain;
  var util = require('util');
  
  function EventEmitter() {
    EventEmitter.init.call(this);
  }
  module.exports = EventEmitter;
  
  // Backwards-compat with node 0.10.x
  EventEmitter.EventEmitter = EventEmitter;
  
  EventEmitter.usingDomains = false;
  
  EventEmitter.prototype.domain = undefined;
  EventEmitter.prototype._events = undefined;
  EventEmitter.prototype._maxListeners = undefined;
  
  // By default EventEmitters will print a warning if more than 10 listeners are
  // added to it. This is a useful default which helps finding memory leaks.
  EventEmitter.defaultMaxListeners = 10;
  
  EventEmitter.init = function() {
    this.domain = null;
    if (EventEmitter.usingDomains) {
      // if there is an active domain, then attach to it.
      domain = domain || require('domain');
      if (domain.active && !(this instanceof domain.Domain)) {
        this.domain = domain.active;
      }
    }
  
    if (!this._events || this._events === Object.getPrototypeOf(this)._events)
      this._events = {};
  
    this._maxListeners = this._maxListeners || undefined;
  };
  
  // Obviously not all Emitters should be limited to 10. This function allows
  // that to be increased. Set to zero for unlimited.
  EventEmitter.prototype.setMaxListeners = function setMaxListeners(n) {
    if (!util.isNumber(n) || n < 0 || isNaN(n))
      throw TypeError('n must be a positive number');
    this._maxListeners = n;
    return this;
  };
  
  EventEmitter.prototype.emit = function emit(type) {
    var er, handler, len, args, i, listeners;
  
    if (!this._events)
      this._events = {};
  
    // If there is no 'error' event listener then throw.
    if (type === 'error' && !this._events.error) {
      er = arguments[1];
      if (this.domain) {
        if (!er)
          er = new Error('Uncaught, unspecified "error" event.');
        er.domainEmitter = this;
        er.domain = this.domain;
        er.domainThrown = false;
        this.domain.emit('error', er);
      } else if (er instanceof Error) {
        throw er; // Unhandled 'error' event
      } else {
        throw Error('Uncaught, unspecified "error" event.');
      }
      return false;
    }
  
    handler = this._events[type];
  
    if (util.isUndefined(handler))
      return false;
  
    if (this.domain && this !== process)
      this.domain.enter();
  
    if (util.isFunction(handler)) {
      switch (arguments.length) {
        // fast cases
        case 1:
          handler.call(this);
          break;
        case 2:
          handler.call(this, arguments[1]);
          break;
        case 3:
          handler.call(this, arguments[1], arguments[2]);
          break;
        // slower
        default:
          len = arguments.length;
          args = new Array(len - 1);
          for (i = 1; i < len; i++)
            args[i - 1] = arguments[i];
          handler.apply(this, args);
      }
    } else if (util.isObject(handler)) {
      len = arguments.length;
      args = new Array(len - 1);
      for (i = 1; i < len; i++)
        args[i - 1] = arguments[i];
  
      listeners = handler.slice();
      len = listeners.length;
      for (i = 0; i < len; i++)
        listeners[i].apply(this, args);
    }
  
    if (this.domain && this !== process)
      this.domain.exit();
  
    return true;
  };
  
  EventEmitter.prototype.addListener = function addListener(type, listener) {
    var m;
  
    if (!util.isFunction(listener))
      throw TypeError('listener must be a function');
  
    if (!this._events)
      this._events = {};
  
    // To avoid recursion in the case that type === "newListener"! Before
    // adding it to the listeners, first emit "newListener".
    if (this._events.newListener)
      this.emit('newListener', type,
                util.isFunction(listener.listener) ?
                listener.listener : listener);
  
    if (!this._events[type])
      // Optimize the case of one listener. Don't need the extra array object.
      this._events[type] = listener;
    else if (util.isObject(this._events[type]))
      // If we've already got an array, just append.
      this._events[type].push(listener);
    else
      // Adding the second element, need to change to array.
      this._events[type] = [this._events[type], listener];
  
    // Check for listener leak
    if (util.isObject(this._events[type]) && !this._events[type].warned) {
      var m;
      if (!util.isUndefined(this._maxListeners)) {
        m = this._maxListeners;
      } else {
        m = EventEmitter.defaultMaxListeners;
      }
  
      if (m && m > 0 && this._events[type].length > m) {
        this._events[type].warned = true;
        console.error('(node) warning: possible EventEmitter memory ' +
                      'leak detected. %d listeners added. ' +
                      'Use emitter.setMaxListeners() to increase limit.',
                      this._events[type].length);
        console.trace();
      }
    }
  
    return this;
  };
  
  EventEmitter.prototype.on = EventEmitter.prototype.addListener;
  
  EventEmitter.prototype.once = function once(type, listener) {
    if (!util.isFunction(listener))
      throw TypeError('listener must be a function');
  
    var fired = false;
  
    function g() {
      this.removeListener(type, g);
  
      if (!fired) {
        fired = true;
        listener.apply(this, arguments);
      }
    }
  
    g.listener = listener;
    this.on(type, g);
  
    return this;
  };
  
  // emits a 'removeListener' event iff the listener was removed
  EventEmitter.prototype.removeListener =
      function removeListener(type, listener) {
    var list, position, length, i;
  
    if (!util.isFunction(listener))
      throw TypeError('listener must be a function');
  
    if (!this._events || !this._events[type])
      return this;
  
    list = this._events[type];
    length = list.length;
    position = -1;
  
    if (list === listener ||
        (util.isFunction(list.listener) && list.listener === listener)) {
      delete this._events[type];
      if (this._events.removeListener)
        this.emit('removeListener', type, listener);
  
    } else if (util.isObject(list)) {
      for (i = length; i-- > 0;) {
        if (list[i] === listener ||
            (list[i].listener && list[i].listener === listener)) {
          position = i;
          break;
        }
      }
  
      if (position < 0)
        return this;
  
      if (list.length === 1) {
        list.length = 0;
        delete this._events[type];
      } else {
        list.splice(position, 1);
      }
  
      if (this._events.removeListener)
        this.emit('removeListener', type, listener);
    }
  
    return this;
  };
  
  EventEmitter.prototype.removeAllListeners =
      function removeAllListeners(type) {
    var key, listeners;
  
    if (!this._events)
      return this;
  
    // not listening for removeListener, no need to emit
    if (!this._events.removeListener) {
      if (arguments.length === 0)
        this._events = {};
      else if (this._events[type])
        delete this._events[type];
      return this;
    }
  
    // emit removeListener for all listeners on all events
    if (arguments.length === 0) {
      for (key in this._events) {
        if (key === 'removeListener') continue;
        this.removeAllListeners(key);
      }
      this.removeAllListeners('removeListener');
      this._events = {};
      return this;
    }
  
    listeners = this._events[type];
  
    if (util.isFunction(listeners)) {
      this.removeListener(type, listeners);
    } else if (Array.isArray(listeners)) {
      // LIFO order
      while (listeners.length)
        this.removeListener(type, listeners[listeners.length - 1]);
    }
    delete this._events[type];
  
    return this;
  };
  
  EventEmitter.prototype.listeners = function listeners(type) {
    var ret;
    if (!this._events || !this._events[type])
      ret = [];
    else if (util.isFunction(this._events[type]))
      ret = [this._events[type]];
    else
      ret = this._events[type].slice();
    return ret;
  };
  
  EventEmitter.listenerCount = function(emitter, type) {
    var ret;
    if (!emitter._events || !emitter._events[type])
      ret = 0;
    else if (util.isFunction(emitter._events[type]))
      ret = 1;
    else
      ret = emitter._events[type].length;
    return ret;
  };
  