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events: use spread function param in emit

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With recent changes in V8, it is now as performant or faster to use
spread parameter within EventEmitter.prototype.emit, especially
in cases where looping over arguments is required.

events/ee-emit.js n=2000000               4.40 %    *** 1.505543e-06
events/ee-emit-1-arg.js n=2000000         2.16 %    *** 2.434584e-10
events/ee-emit-2-args.js n=2000000        1.05 %     ** 0.001764852
events/ee-emit-3-args.js n=2000000        2.18 %    *** 3.234954e-08
events/ee-emit-6-args.js n=2000000       17.17 %    *** 1.298702e-103
events/ee-emit-10-args.js n=2000000      17.14 %    *** 1.144958e-97

This has a knock-on effect for modules that use events extensively,
such as http2:

http2/headers.js nheaders=0 n=1000        2.10 %    *** 6.792106e-11

PR-URL: https://github.com/nodejs/node/pull/16212
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
This commit is contained in:
Anatoli Papirovski 2017-10-15 00:44:47 -04:00
parent fd166a8759
commit d5fb78982a
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1 changed files with 17 additions and 23 deletions
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40
lib/events.js
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@ -162,23 +162,22 @@ function emitMany(handler, isFn, self, args) {
} }
} }
EventEmitter.prototype.emit = function emit(type) { EventEmitter.prototype.emit = function emit(type, ...args) {
var er, handler, len, args, i, events, domain; let doError = (type === 'error');
var needDomainExit = false;
var doError = (type === 'error');
events = this._events; const events = this._events;
if (events !== undefined) if (events !== undefined)
doError = (doError && events.error === undefined); doError = (doError && events.error === undefined);
else if (!doError) else if (!doError)
return false; return false;
domain = this.domain; const domain = this.domain;
// If there is no 'error' event listener then throw. // If there is no 'error' event listener then throw.
if (doError) { if (doError) {
if (arguments.length > 1) let er;
er = arguments[1]; if (args.length > 0)
er = args[0];
if (domain !== null && domain !== undefined) { if (domain !== null && domain !== undefined) {
if (!er) { if (!er) {
const errors = lazyErrors(); const errors = lazyErrors();
@ -202,37 +201,32 @@ EventEmitter.prototype.emit = function emit(type) {
return false; return false;
} }
handler = events[type]; const handler = events[type];
if (handler === undefined) if (handler === undefined)
return false; return false;
let needDomainExit = false;
if (domain !== null && domain !== undefined && this !== process) { if (domain !== null && domain !== undefined && this !== process) {
domain.enter(); domain.enter();
needDomainExit = true; needDomainExit = true;
} }
var isFn = typeof handler === 'function'; const isFn = typeof handler === 'function';
len = arguments.length; switch (args.length) {
switch (len) { case 0:
// fast cases
case 1:
emitNone(handler, isFn, this); emitNone(handler, isFn, this);
break; break;
case 1:
emitOne(handler, isFn, this, args[0]);
break;
case 2: case 2:
emitOne(handler, isFn, this, arguments[1]); emitTwo(handler, isFn, this, args[0], args[1]);
break; break;
case 3: case 3:
emitTwo(handler, isFn, this, arguments[1], arguments[2]); emitThree(handler, isFn, this, args[0], args[1], args[2]);
break; break;
case 4:
emitThree(handler, isFn, this, arguments[1], arguments[2], arguments[3]);
break;
// slower
default: default:
args = new Array(len - 1);
for (i = 1; i < len; i++)
args[i - 1] = arguments[i];
emitMany(handler, isFn, this, args); emitMany(handler, isFn, this, args);
} }