From a510b3dd03af100425dbe9ecd248d88f46999834 Mon Sep 17 00:00:00 2001
From: Connor Peet <connor@peet.io>
Date: Fri, 19 Aug 2016 12:38:16 -0700
Subject: [PATCH] Update to Node 6's events API

---
 events.js | 551 +++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 359 insertions(+), 192 deletions(-)

diff --git a/events.js b/events.js
index 1619a62..6fb27dc 100644
--- a/events.js
+++ b/events.js
@@ -19,9 +19,11 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
+function EventHandlers() {}
+EventHandlers.prototype = Object.create(null);
+
 function EventEmitter() {
-  this._events = this._events || {};
-  this._maxListeners = this._maxListeners || undefined;
+  EventEmitter.init.call(this);
 }
 module.exports = EventEmitter;
 
@@ -33,270 +35,435 @@ 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;
+var defaultMaxListeners = 10;
+
+Object.defineProperty(EventEmitter, 'defaultMaxListeners', {
+  enumerable: true,
+  get: function() {
+    return defaultMaxListeners;
+  },
+  set: function(arg) {
+    // force global console to be compiled.
+    // see https://github.com/nodejs/node/issues/4467
+    console;
+    defaultMaxListeners = arg;
+  }
+});
+
+EventEmitter.init = function() {
+  if (!this._events || this._events === Object.getPrototypeOf(this)._events) {
+    this._events = new EventHandlers();
+    this._eventsCount = 0;
+  }
+
+  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(n) {
-  if (!isNumber(n) || n < 0 || isNaN(n))
-    throw TypeError('n must be a positive number');
+EventEmitter.prototype.setMaxListeners = function setMaxListeners(n) {
+  if (typeof n !== 'number' || n < 0 || isNaN(n))
+    throw new TypeError('"n" argument must be a positive number');
   this._maxListeners = n;
   return this;
 };
 
-EventEmitter.prototype.emit = function(type) {
-  var er, handler, len, args, i, listeners;
+function $getMaxListeners(that) {
+  if (that._maxListeners === undefined)
+    return EventEmitter.defaultMaxListeners;
+  return that._maxListeners;
+}
+
+EventEmitter.prototype.getMaxListeners = function getMaxListeners() {
+  return $getMaxListeners(this);
+};
+
+// These standalone emit* functions are used to optimize calling of event
+// handlers for fast cases because emit() itself often has a variable number of
+// arguments and can be deoptimized because of that. These functions always have
+// the same number of arguments and thus do not get deoptimized, so the code
+// inside them can execute faster.
+function emitNone(handler, isFn, self) {
+  if (isFn)
+    handler.call(self);
+  else {
+    var len = handler.length;
+    var listeners = arrayClone(handler, len);
+    for (var i = 0; i < len; ++i)
+      listeners[i].call(self);
+  }
+}
+function emitOne(handler, isFn, self, arg1) {
+  if (isFn)
+    handler.call(self, arg1);
+  else {
+    var len = handler.length;
+    var listeners = arrayClone(handler, len);
+    for (var i = 0; i < len; ++i)
+      listeners[i].call(self, arg1);
+  }
+}
+function emitTwo(handler, isFn, self, arg1, arg2) {
+  if (isFn)
+    handler.call(self, arg1, arg2);
+  else {
+    var len = handler.length;
+    var listeners = arrayClone(handler, len);
+    for (var i = 0; i < len; ++i)
+      listeners[i].call(self, arg1, arg2);
+  }
+}
+function emitThree(handler, isFn, self, arg1, arg2, arg3) {
+  if (isFn)
+    handler.call(self, arg1, arg2, arg3);
+  else {
+    var len = handler.length;
+    var listeners = arrayClone(handler, len);
+    for (var i = 0; i < len; ++i)
+      listeners[i].call(self, arg1, arg2, arg3);
+  }
+}
+
+function emitMany(handler, isFn, self, args) {
+  if (isFn)
+    handler.apply(self, args);
+  else {
+    var len = handler.length;
+    var listeners = arrayClone(handler, len);
+    for (var i = 0; i < len; ++i)
+      listeners[i].apply(self, args);
+  }
+}
 
-  if (!this._events)
-    this._events = {};
+EventEmitter.prototype.emit = function emit(type) {
+  var er, handler, len, args, i, events;
+  var doError = (type === 'error');
+
+  events = this._events;
+  if (events)
+    doError = (doError && events.error == null);
+  else if (!doError)
+    return false;
 
   // If there is no 'error' event listener then throw.
-  if (type === 'error') {
-    if (!this._events.error ||
-        (isObject(this._events.error) && !this._events.error.length)) {
-      er = arguments[1];
-      if (er instanceof Error) {
-        throw er; // Unhandled 'error' event
-      } else {
-        // At least give some kind of context to the user
-        var err = new Error('Uncaught, unspecified "error" event. (' + er + ')');
-        err.context = er;
-        throw err;
-      }
+  if (doError) {
+    er = arguments[1];
+    if (er instanceof Error) {
+      throw er; // Unhandled 'error' event
+    } else {
+      // At least give some kind of context to the user
+      var err = new Error('Uncaught, unspecified "error" event. (' + er + ')');
+      err.context = er;
+      throw err;
     }
+    return false;
   }
 
-  handler = this._events[type];
+  handler = events[type];
 
-  if (isUndefined(handler))
+  if (!handler)
     return false;
 
-  if (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:
-        args = Array.prototype.slice.call(arguments, 1);
-        handler.apply(this, args);
-    }
-  } else if (isObject(handler)) {
-    args = Array.prototype.slice.call(arguments, 1);
-    listeners = handler.slice();
-    len = listeners.length;
-    for (i = 0; i < len; i++)
-      listeners[i].apply(this, args);
+  var isFn = typeof handler === 'function';
+  len = arguments.length;
+  switch (len) {
+    // fast cases
+    case 1:
+      emitNone(handler, isFn, this);
+      break;
+    case 2:
+      emitOne(handler, isFn, this, arguments[1]);
+      break;
+    case 3:
+      emitTwo(handler, isFn, this, arguments[1], arguments[2]);
+      break;
+    case 4:
+      emitThree(handler, isFn, this, arguments[1], arguments[2], arguments[3]);
+      break;
+    // slower
+    default:
+      args = new Array(len - 1);
+      for (i = 1; i < len; i++)
+        args[i - 1] = arguments[i];
+      emitMany(handler, isFn, this, args);
   }
 
   return true;
 };
 
-EventEmitter.prototype.addListener = function(type, listener) {
+function _addListener(target, type, listener, prepend) {
   var m;
+  var events;
+  var existing;
+
+  if (typeof listener !== 'function')
+    throw new TypeError('"listener" argument must be a function');
+
+  events = target._events;
+  if (!events) {
+    events = target._events = new EventHandlers();
+    target._eventsCount = 0;
+  } else {
+    // To avoid recursion in the case that type === "newListener"! Before
+    // adding it to the listeners, first emit "newListener".
+    if (events.newListener) {
+      target.emit('newListener', type,
+                  listener.listener ? listener.listener : listener);
+
+      // Re-assign `events` because a newListener handler could have caused the
+      // this._events to be assigned to a new object
+      events = target._events;
+    }
+    existing = events[type];
+  }
 
-  if (!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,
-              isFunction(listener.listener) ?
-              listener.listener : listener);
-
-  if (!this._events[type])
+  if (!existing) {
     // Optimize the case of one listener. Don't need the extra array object.
-    this._events[type] = listener;
-  else if (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 (isObject(this._events[type]) && !this._events[type].warned) {
-    if (!isUndefined(this._maxListeners)) {
-      m = this._maxListeners;
+    existing = events[type] = listener;
+    ++target._eventsCount;
+  } else {
+    if (typeof existing === 'function') {
+      // Adding the second element, need to change to array.
+      existing = events[type] = prepend ? [listener, existing] :
+                                          [existing, listener];
     } else {
-      m = EventEmitter.defaultMaxListeners;
+      // If we've already got an array, just append.
+      if (prepend) {
+        existing.unshift(listener);
+      } else {
+        existing.push(listener);
+      }
     }
 
-    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);
-      if (typeof console.trace === 'function') {
-        // not supported in IE 10
-        console.trace();
+    // Check for listener leak
+    if (!existing.warned) {
+      m = $getMaxListeners(target);
+      if (m && m > 0 && existing.length > m) {
+        existing.warned = true;
+        console.warn('Possible EventEmitter memory leak detected. ' +
+                     existing.length + ' ' + type + ' listeners added. ' +
+                     'Use emitter.setMaxListeners() to increase limit');
       }
     }
   }
 
-  return this;
+  return target;
+}
+
+EventEmitter.prototype.addListener = function addListener(type, listener) {
+  return _addListener(this, type, listener, false);
 };
 
 EventEmitter.prototype.on = EventEmitter.prototype.addListener;
 
-EventEmitter.prototype.once = function(type, listener) {
-  if (!isFunction(listener))
-    throw TypeError('listener must be a function');
+EventEmitter.prototype.prependListener =
+    function prependListener(type, listener) {
+      return _addListener(this, type, listener, true);
+    };
 
+function _onceWrap(target, type, listener) {
   var fired = false;
-
   function g() {
-    this.removeListener(type, g);
-
+    target.removeListener(type, g);
     if (!fired) {
       fired = true;
-      listener.apply(this, arguments);
+      listener.apply(target, arguments);
     }
   }
-
   g.listener = listener;
-  this.on(type, g);
+  return g;
+}
 
+EventEmitter.prototype.once = function once(type, listener) {
+  if (typeof listener !== 'function')
+    throw new TypeError('"listener" argument must be a function');
+  this.on(type, _onceWrap(this, type, listener));
   return this;
 };
 
+EventEmitter.prototype.prependOnceListener =
+    function prependOnceListener(type, listener) {
+      if (typeof listener !== 'function')
+        throw new TypeError('"listener" argument must be a function');
+      this.prependListener(type, _onceWrap(this, type, listener));
+      return this;
+    };
+
 // emits a 'removeListener' event iff the listener was removed
-EventEmitter.prototype.removeListener = function(type, listener) {
-  var list, position, length, i;
-
-  if (!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 ||
-      (isFunction(list.listener) && list.listener === listener)) {
-    delete this._events[type];
-    if (this._events.removeListener)
-      this.emit('removeListener', type, listener);
-
-  } else if (isObject(list)) {
-    for (i = length; i-- > 0;) {
-      if (list[i] === listener ||
-          (list[i].listener && list[i].listener === listener)) {
-        position = i;
-        break;
+EventEmitter.prototype.removeListener =
+    function removeListener(type, listener) {
+      var list, events, position, i, originalListener;
+
+      if (typeof listener !== 'function')
+        throw new TypeError('"listener" argument must be a function');
+
+      events = this._events;
+      if (!events)
+        return this;
+
+      list = events[type];
+      if (!list)
+        return this;
+
+      if (list === listener || (list.listener && list.listener === listener)) {
+        if (--this._eventsCount === 0)
+          this._events = new EventHandlers();
+        else {
+          delete events[type];
+          if (events.removeListener)
+            this.emit('removeListener', type, list.listener || listener);
+        }
+      } else if (typeof list !== 'function') {
+        position = -1;
+
+        for (i = list.length; i-- > 0;) {
+          if (list[i] === listener ||
+              (list[i].listener && list[i].listener === listener)) {
+            originalListener = list[i].listener;
+            position = i;
+            break;
+          }
+        }
+
+        if (position < 0)
+          return this;
+
+        if (list.length === 1) {
+          list[0] = undefined;
+          if (--this._eventsCount === 0) {
+            this._events = new EventHandlers();
+            return this;
+          } else {
+            delete events[type];
+          }
+        } else {
+          spliceOne(list, position);
+        }
+
+        if (events.removeListener)
+          this.emit('removeListener', type, originalListener || listener);
       }
-    }
 
-    if (position < 0)
       return this;
+    };
+
+EventEmitter.prototype.removeAllListeners =
+    function removeAllListeners(type) {
+      var listeners, events;
+
+      events = this._events;
+      if (!events)
+        return this;
+
+      // not listening for removeListener, no need to emit
+      if (!events.removeListener) {
+        if (arguments.length === 0) {
+          this._events = new EventHandlers();
+          this._eventsCount = 0;
+        } else if (events[type]) {
+          if (--this._eventsCount === 0)
+            this._events = new EventHandlers();
+          else
+            delete events[type];
+        }
+        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);
-  }
+      // emit removeListener for all listeners on all events
+      if (arguments.length === 0) {
+        var keys = Object.keys(events);
+        for (var i = 0, key; i < keys.length; ++i) {
+          key = keys[i];
+          if (key === 'removeListener') continue;
+          this.removeAllListeners(key);
+        }
+        this.removeAllListeners('removeListener');
+        this._events = new EventHandlers();
+        this._eventsCount = 0;
+        return this;
+      }
 
-  return this;
-};
+      listeners = events[type];
 
-EventEmitter.prototype.removeAllListeners = function(type) {
-  var key, listeners;
+      if (typeof listeners === 'function') {
+        this.removeListener(type, listeners);
+      } else if (listeners) {
+        // LIFO order
+        do {
+          this.removeListener(type, listeners[listeners.length - 1]);
+        } while (listeners[0]);
+      }
 
-  if (!this._events)
-    return this;
+      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;
-  }
+EventEmitter.prototype.listeners = function listeners(type) {
+  var evlistener;
+  var ret;
+  var events = this._events;
 
-  // 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;
+  if (!events)
+    ret = [];
+  else {
+    evlistener = events[type];
+    if (!evlistener)
+      ret = [];
+    else if (typeof evlistener === 'function')
+      ret = [evlistener.listener || evlistener];
+    else
+      ret = unwrapListeners(evlistener);
   }
 
-  listeners = this._events[type];
+  return ret;
+};
 
-  if (isFunction(listeners)) {
-    this.removeListener(type, listeners);
-  } else if (listeners) {
-    // LIFO order
-    while (listeners.length)
-      this.removeListener(type, listeners[listeners.length - 1]);
+EventEmitter.listenerCount = function(emitter, type) {
+  if (typeof emitter.listenerCount === 'function') {
+    return emitter.listenerCount(type);
+  } else {
+    return listenerCount.call(emitter, type);
   }
-  delete this._events[type];
-
-  return this;
 };
 
-EventEmitter.prototype.listeners = function(type) {
-  var ret;
-  if (!this._events || !this._events[type])
-    ret = [];
-  else if (isFunction(this._events[type]))
-    ret = [this._events[type]];
-  else
-    ret = this._events[type].slice();
-  return ret;
-};
+EventEmitter.prototype.listenerCount = listenerCount;
+function listenerCount(type) {
+  const events = this._events;
 
-EventEmitter.prototype.listenerCount = function(type) {
-  if (this._events) {
-    var evlistener = this._events[type];
+  if (events) {
+    const evlistener = events[type];
 
-    if (isFunction(evlistener))
+    if (typeof evlistener === 'function') {
       return 1;
-    else if (evlistener)
+    } else if (evlistener) {
       return evlistener.length;
+    }
   }
+
   return 0;
-};
+}
 
-EventEmitter.listenerCount = function(emitter, type) {
-  return emitter.listenerCount(type);
+EventEmitter.prototype.eventNames = function eventNames() {
+  return this._eventsCount > 0 ? Reflect.ownKeys(this._events) : [];
 };
 
-function isFunction(arg) {
-  return typeof arg === 'function';
+// About 1.5x faster than the two-arg version of Array#splice().
+function spliceOne(list, index) {
+  for (var i = index, k = i + 1, n = list.length; k < n; i += 1, k += 1)
+    list[i] = list[k];
+  list.pop();
 }
 
-function isNumber(arg) {
-  return typeof arg === 'number';
+function arrayClone(arr, i) {
+  var copy = new Array(i);
+  while (i--)
+    copy[i] = arr[i];
+  return copy;
 }
 
-function isObject(arg) {
-  return typeof arg === 'object' && arg !== null;
-}
-
-function isUndefined(arg) {
-  return arg === void 0;
+function unwrapListeners(arr) {
+  const ret = new Array(arr.length);
+  for (var i = 0; i < ret.length; ++i) {
+    ret[i] = arr[i].listener || arr[i];
+  }
+  return ret;
 }