stream: pre-allocate _events

PR-URL: #50428
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Vinícius Lourenço Claro Cardoso <contact@viniciusl.com.br>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

Author: ronag

lib/events.js

@@ -86,6 +86,7 @@ const {
 
 constkCapture=Symbol('kCapture');
 constkErrorMonitor=Symbol('events.errorMonitor');
+constkShapeMode=Symbol('shapeMode');
 constkMaxEventTargetListeners=Symbol('events.maxEventTargetListeners');
 constkMaxEventTargetListenersWarned=
 Symbol('events.maxEventTargetListenersWarned');
@@ -343,6 +344,9 @@ EventEmitter.init = function(opts) {
 this._events===ObjectGetPrototypeOf(this)._events){
 this._events={__proto__: null};
 this._eventsCount=0;
+this[kShapeMode]=false;
+}else{
+this[kShapeMode]=true;
 }
 
 this._maxListeners=this._maxListeners||undefined;
@@ -685,9 +689,13 @@ EventEmitter.prototype.removeListener =
 returnthis;
 
 if(list===listener||list.listener===listener){
-if(--this._eventsCount===0)
+this._eventsCount-=1;
+
+if(this[kShapeMode]){
+events[type]=undefined;
+}elseif(this._eventsCount===0){
 this._events={__proto__: null};
-else{
+}else{
 deleteevents[type];
 if(events.removeListener)
 this.emit('removeListener',type,list.listener||listener);
@@ -749,6 +757,7 @@ EventEmitter.prototype.removeAllListeners =
 else
 deleteevents[type];
 }
+this[kShapeMode]=false;
 returnthis;
 }
 
@@ -761,6 +770,7 @@ EventEmitter.prototype.removeAllListeners =
 this.removeAllListeners('removeListener');
 this._events={__proto__: null};
 this._eventsCount=0;
+this[kShapeMode]=false;
 returnthis;
 }
 

lib/internal/streams/duplex.js

@@ -63,6 +63,24 @@ function Duplex(options) {
 if(!(thisinstanceofDuplex))
 returnnewDuplex(options);
 
+this._events??={
+close: undefined,
+error: undefined,
+prefinish: undefined,
+finish: undefined,
+drain: undefined,
+data: undefined,
+end: undefined,
+readable: undefined,
+// Skip uncommon events...
+// pause: undefined,
+// resume: undefined,
+// pipe: undefined,
+// unpipe: undefined,
+// [destroyImpl.kConstruct]: undefined,
+// [destroyImpl.kDestroy]: undefined,
+};
+
 this._readableState=newReadable.ReadableState(options,this,true);
 this._writableState=newWritable.WritableState(options,this,true);
 

lib/internal/streams/readable.js

@@ -319,6 +319,21 @@ function Readable(options) {
 if(!(thisinstanceofReadable))
 returnnewReadable(options);
 
+this._events??={
+close: undefined,
+error: undefined,
+data: undefined,
+end: undefined,
+readable: undefined,
+// Skip uncommon events...
+// pause: undefined,
+// resume: undefined,
+// pipe: undefined,
+// unpipe: undefined,
+// [destroyImpl.kConstruct]: undefined,
+// [destroyImpl.kDestroy]: undefined,
+};
+
 this._readableState=newReadableState(options,this,false);
 
 if(options){

lib/internal/streams/writable.js

@@ -385,6 +385,17 @@ function Writable(options) {
 if(!(thisinstanceofWritable))
 returnnewWritable(options);
 
+this._events??={
+close: undefined,
+error: undefined,
+prefinish: undefined,
+finish: undefined,
+drain: undefined,
+// Skip uncommon events...
+// [destroyImpl.kConstruct]: undefined,
+// [destroyImpl.kDestroy]: undefined,
+};
+
 this._writableState=newWritableState(options,this,false);
 
 if(options){

test/parallel/test-readline-interface.js

@@ -44,7 +44,7 @@ class FakeInput extends EventEmitter {
 functionisWarned(emitter){
 for(constnameinemitter){
 constlisteners=emitter[name];
-if(listeners.warned)returntrue;
+if(listeners&&listeners.warned)returntrue;
 }
 returnfalse;
 }

test/parallel/test-readline-promises-interface.js

@@ -22,7 +22,7 @@ class FakeInput extends EventEmitter {
 functionisWarned(emitter){
 for(constnameinemitter){
 constlisteners=emitter[name];
-if(listeners.warned)returntrue;
+if(listeners&&listeners.warned)returntrue;
 }
 returnfalse;
 }