events: improve arrayClone performance

PR-URL: #33774 Reviewed-By: Robert Nagy <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Michaël Zasso <[email protected]> Reviewed-By: Zeyu Yang <[email protected]>

Author: mscdex

benchmark/events/ee-emit.js

@@ -10,6 +10,7 @@ const bench = common.createBenchmark(main,{
 
 functionmain({ n, argc, listeners }){
 constee=newEventEmitter();
+ee.setMaxListeners(listeners+1);
 
 for(letk=0;k<listeners;k+=1)
 ee.on('dummy',()=>{});

benchmark/events/ee-listeners-many.js

@@ -2,20 +2,34 @@
 constcommon=require('../common.js');
 constEventEmitter=require('events').EventEmitter;
 
-constbench=common.createBenchmark(main,{n: [5e6]});
+constbench=common.createBenchmark(main,{
+n: [5e6],
+listeners: [5,50],
+raw: ['true','false']
+});
 
-functionmain({ n }){
+functionmain({ n, listeners, raw}){
 constee=newEventEmitter();
+ee.setMaxListeners(listeners*2+1);
 
-for(letk=0;k<5;k+=1){
+for(letk=0;k<listeners;k+=1){
 ee.on('dummy0',()=>{});
 ee.on('dummy1',()=>{});
 }
 
-bench.start();
-for(leti=0;i<n;i+=1){
-constdummy=(i%2===0) ? 'dummy0' : 'dummy1';
-ee.listeners(dummy);
+if(raw==='true'){
+bench.start();
+for(leti=0;i<n;i+=1){
+constdummy=(i%2===0) ? 'dummy0' : 'dummy1';
+ee.rawListeners(dummy);
+}
+bench.end(n);
+}else{
+bench.start();
+for(leti=0;i<n;i+=1){
+constdummy=(i%2===0) ? 'dummy0' : 'dummy1';
+ee.listeners(dummy);
+}
+bench.end(n);
 }
-bench.end(n);
 }

benchmark/events/ee-listeners.js

@@ -322,7 +322,7 @@ EventEmitter.prototype.emit = function emit(type, ...args){
 }
 }else{
 constlen=handler.length;
-constlisteners=arrayClone(handler,len);
+constlisteners=arrayClone(handler);
 for(leti=0;i<len;++i){
 constresult=ReflectApply(listeners[i],this,args);
 
@@ -563,7 +563,7 @@ function _listeners(target, type, unwrap){
 returnunwrap ? [evlistener.listener||evlistener] : [evlistener];
 
 returnunwrap ?
-unwrapListeners(evlistener) : arrayClone(evlistener,evlistener.length);
+unwrapListeners(evlistener) : arrayClone(evlistener);
 }
 
 EventEmitter.prototype.listeners=functionlisteners(type){
@@ -602,11 +602,17 @@ EventEmitter.prototype.eventNames = function eventNames(){
 returnthis._eventsCount>0 ? ReflectOwnKeys(this._events) : [];
 };
 
-functionarrayClone(arr,n){
-constcopy=newArray(n);
-for(leti=0;i<n;++i)
-copy[i]=arr[i];
-returncopy;
+functionarrayClone(arr){
+// At least since V8 8.3, this implementation is faster than the previous
+// which always used a simple for-loop
+switch(arr.length){
+case2: return[arr[0],arr[1]];
+case3: return[arr[0],arr[1],arr[2]];
+case4: return[arr[0],arr[1],arr[2],arr[3]];
+case5: return[arr[0],arr[1],arr[2],arr[3],arr[4]];
+case6: return[arr[0],arr[1],arr[2],arr[3],arr[4],arr[5]];
+}
+returnarr.slice();
 }
 
 functionunwrapListeners(arr){