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events: improve events performance #50422

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eb29e97
events: improve creation performance
rluvaton Oct 27, 2023
249c2b8
events: replace _events with Map
rluvaton Oct 27, 2023
9d626b9
events: remove `__proto__` null from `_events`
rluvaton Oct 27, 2023
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122 changes: 75 additions & 47 deletions lib/events.js
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Original file line number Diff line number Diff line change
Expand Up @@ -42,13 +42,15 @@ const {
PromiseReject,
PromiseResolve,
ReflectApply,
ReflectOwnKeys,
String,
ObjectFromEntries,
ArrayFrom,
StringPrototypeSplit,
Symbol,
SymbolFor,
SymbolAsyncIterator,
SymbolDispose,
SafeMap,
} = primordials;
const kRejection = SymbolFor('nodejs.rejection');

Expand Down Expand Up @@ -85,6 +87,7 @@ const {
validateString,
} = require('internal/validators');

const kEvents = Symbol('kEvents');
const kCapture = Symbol('kCapture');
const kErrorMonitor = Symbol('events.errorMonitor');
const kMaxEventTargetListeners = Symbol('events.maxEventTargetListeners');
Expand Down Expand Up @@ -262,8 +265,7 @@ ObjectDefineProperty(EventEmitter.prototype, kCapture, {
enumerable: false,
});

EventEmitter.prototype._events = undefined;
EventEmitter.prototype._eventsCount = 0;
EventEmitter.prototype[kEvents] = undefined;
EventEmitter.prototype._maxListeners = undefined;

// By default EventEmitters will print a warning if more than 10 listeners are
Expand All @@ -287,6 +289,37 @@ ObjectDefineProperty(EventEmitter, 'defaultMaxListeners', {
},
});

// _events and _eventsCount are Legacy
ObjectDefineProperty(EventEmitter.prototype, '_events', {
__proto__: null,
enumerable: true,
get: function() {
// TODO - maybe in order to not break the ecosystem, create a Proxy that will update the events map
const events = this[kEvents];
if (events === undefined) {
return undefined;
}

return ObjectFromEntries(events.entries());
},
set: function(events) {
this[kEvents] = new SafeMap(events);
},
});

ObjectDefineProperty(EventEmitter.prototype, '_eventsCount', {
__proto__: null,
enumerable: true,
get: function() {
const events = this[kEvents];
if (events === undefined) {
return 0;
}

return events.size;
},
});

ObjectDefineProperties(EventEmitter, {
kMaxEventTargetListeners: {
__proto__: null,
Expand Down Expand Up @@ -339,11 +372,9 @@ EventEmitter.setMaxListeners =
// If you're updating this function definition, please also update any
// re-definitions, such as the one in the Domain module (lib/domain.js).
EventEmitter.init = function(opts) {

if (this._events === undefined ||
this._events === ObjectGetPrototypeOf(this)._events) {
this._events = { __proto__: null };
this._eventsCount = 0;
if (this[kEvents] === undefined ||
this[kEvents] === ObjectGetPrototypeOf(this)[kEvents]) {
this[kEvents] = new SafeMap();
}

this._maxListeners = this._maxListeners || undefined;
Expand Down Expand Up @@ -462,11 +493,11 @@ function enhanceStackTrace(err, own) {
EventEmitter.prototype.emit = function emit(type, ...args) {
let doError = (type === 'error');

const events = this._events;
const events = this[kEvents];
if (events !== undefined) {
if (doError && events[kErrorMonitor] !== undefined)
if (doError && events.has(kErrorMonitor))
this.emit(kErrorMonitor, ...args);
doError = (doError && events.error === undefined);
doError = (doError && !events.has('error'));
} else if (!doError)
return false;

Expand Down Expand Up @@ -506,7 +537,7 @@ EventEmitter.prototype.emit = function emit(type, ...args) {
throw err; // Unhandled 'error' event
}

const handler = events[type];
const handler = events.get(type);

if (handler === undefined)
return false;
Expand Down Expand Up @@ -547,33 +578,32 @@ function _addListener(target, type, listener, prepend) {

checkListener(listener);

events = target._events;
events = target[kEvents];
if (events === undefined) {
events = target._events = { __proto__: null };
target._eventsCount = 0;
events = target[kEvents] = new SafeMap();
} else {
// To avoid recursion in the case that type === "newListener"! Before
// adding it to the listeners, first emit "newListener".
if (events.newListener !== undefined) {
target.emit('newListener', type,
listener.listener ?? listener);

// TODO - revisit this comment, user can set it to new object?
// Re-assign `events` because a newListener handler could have caused the
// this._events to be assigned to a new object
events = target._events;
// this[kEvents] to be assigned to a new object
events = target[kEvents];
}
existing = events[type];
existing = events.get(type);
}

if (existing === undefined) {
// Optimize the case of one listener. Don't need the extra array object.
events[type] = listener;
++target._eventsCount;
events.set(type, listener);
} else {
if (typeof existing === 'function') {
// Adding the second element, need to change to array.
existing = events[type] =
prepend ? [listener, existing] : [existing, listener];
existing = prepend ? [listener, existing] : [existing, listener];
events.set(type, existing);
// If we've already got an array, just append.
} else if (prepend) {
existing.unshift(listener);
Expand Down Expand Up @@ -677,20 +707,20 @@ EventEmitter.prototype.removeListener =
function removeListener(type, listener) {
checkListener(listener);

const events = this._events;
const events = this[kEvents];
if (events === undefined)
return this;

const list = events[type];
const list = events.get(type);
if (list === undefined)
return this;

if (list === listener || list.listener === listener) {
if (--this._eventsCount === 0)
this._events = { __proto__: null };
if (this[kEvents].size === 1)
this[kEvents] = new SafeMap();
else {
delete events[type];
if (events.removeListener)
events.delete(type);
if (events.has('removeListener'))
this.emit('removeListener', type, list.listener || listener);
}
} else if (typeof list !== 'function') {
Expand All @@ -715,9 +745,9 @@ EventEmitter.prototype.removeListener =
}

if (list.length === 1)
events[type] = list[0];
events.set(type, list[0]);

if (events.removeListener !== undefined)
if (events.has('removeListener'))
this.emit('removeListener', type, listener);
}

Expand All @@ -735,37 +765,35 @@ EventEmitter.prototype.off = EventEmitter.prototype.removeListener;
*/
EventEmitter.prototype.removeAllListeners =
function removeAllListeners(type) {
const events = this._events;
const events = this[kEvents];
if (events === undefined)
return this;

// Not listening for removeListener, no need to emit
if (events.removeListener === undefined) {
if (!events.has('removeListener')) {
if (arguments.length === 0) {
this._events = { __proto__: null };
this._eventsCount = 0;
} else if (events[type] !== undefined) {
if (--this._eventsCount === 0)
this._events = { __proto__: null };
this[kEvents] = new SafeMap();
} else if (events.has(type)) {
if (this[kEvents].size === 1)
this[kEvents] = new SafeMap();
else
delete events[type];
this[kEvents].delete(type);
}
return this;
}

// Emit removeListener for all listeners on all events
if (arguments.length === 0) {
for (const key of ReflectOwnKeys(events)) {
for (const key of events.keys()) {
if (key === 'removeListener') continue;
this.removeAllListeners(key);
}
this.removeAllListeners('removeListener');
this._events = { __proto__: null };
this._eventsCount = 0;
this[kEvents] = new SafeMap();
return this;
}

const listeners = events[type];
const listeners = events.get(type);

if (typeof listeners === 'function') {
this.removeListener(type, listeners);
Expand All @@ -780,12 +808,12 @@ EventEmitter.prototype.removeAllListeners =
};

function _listeners(target, type, unwrap) {
const events = target._events;
const events = target[kEvents];

if (events === undefined)
return [];

const evlistener = events[type];
const evlistener = events.get(type);
if (evlistener === undefined)
return [];

Expand Down Expand Up @@ -841,10 +869,10 @@ EventEmitter.prototype.listenerCount = listenerCount;
* @returns {number}
*/
function listenerCount(type, listener) {
const events = this._events;
const events = this[kEvents];

if (events !== undefined) {
const evlistener = events[type];
const evlistener = events.get(type);

if (typeof evlistener === 'function') {
if (listener != null) {
Expand Down Expand Up @@ -878,7 +906,7 @@ function listenerCount(type, listener) {
* @returns {any[]}
*/
EventEmitter.prototype.eventNames = function eventNames() {
return this._eventsCount > 0 ? ReflectOwnKeys(this._events) : [];
return this[kEvents].size > 0 ? ArrayFrom(this[kEvents].keys()) : [];
};

function arrayClone(arr) {
Expand Down