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events: improve performance for emit(), on(), and listeners() #13155
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Original file line number | Diff line number | Diff line change |
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@@ -86,74 +86,18 @@ EventEmitter.prototype.setMaxListeners = function setMaxListeners(n) { | |
}; | ||
|
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function $getMaxListeners(that) { | ||
if (that._maxListeners === undefined) | ||
const maxListeners = that._maxListeners; | ||
if (maxListeners === undefined) | ||
return EventEmitter.defaultMaxListeners; | ||
return that._maxListeners; | ||
return 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); | ||
} | ||
} | ||
|
||
EventEmitter.prototype.emit = function emit(type) { | ||
var er, handler, len, args, i, events, domain; | ||
var er, fn, i, events, domain; | ||
var needDomainExit = false; | ||
var doError = (type === 'error'); | ||
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|
@@ -189,38 +133,103 @@ EventEmitter.prototype.emit = function emit(type) { | |
return false; | ||
} | ||
|
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handler = events[type]; | ||
fn = events[type]; | ||
|
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if (!handler) | ||
if (!fn) | ||
return false; | ||
|
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if (domain && this !== process) { | ||
domain.enter(); | ||
needDomainExit = true; | ||
} | ||
|
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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); | ||
var len = arguments.length; | ||
var args; | ||
if (typeof fn === 'function') { | ||
switch (len) { | ||
case 1: fn.call(this); break; | ||
case 2: fn.call(this, arguments[1]); break; | ||
case 3: fn.call(this, arguments[1], arguments[2]); break; | ||
case 4: fn.call(this, arguments[1], arguments[2], arguments[3]); | ||
break; | ||
default: | ||
args = new Array(len - 1); | ||
for (i = 1; i < len; i++) | ||
args[i - 1] = arguments[i]; | ||
fn.apply(this, args); | ||
} | ||
} else { | ||
var fnlen = fn.length; | ||
fn = arrayClone(fn, fnlen); | ||
switch (len) { | ||
case 1: | ||
fn[0].call(this); | ||
fn[1].call(this); | ||
if (fnlen === 2) break; | ||
fn[2].call(this); | ||
if (fnlen === 3) break; | ||
fn[3].call(this); | ||
if (fnlen === 4) break; | ||
fn[4].call(this); | ||
if (fnlen === 5) break; | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more.
Is there any significance of unrolling the loop for |
||
for (i = 5; i < fnlen; ++i) | ||
fn[i].call(this); | ||
break; | ||
case 2: | ||
fn[0].call(this, arguments[1]); | ||
fn[1].call(this, arguments[1]); | ||
if (fnlen === 2) break; | ||
fn[2].call(this, arguments[1]); | ||
if (fnlen === 3) break; | ||
fn[3].call(this, arguments[1]); | ||
if (fnlen === 4) break; | ||
fn[4].call(this, arguments[1]); | ||
if (fnlen === 5) break; | ||
for (i = 5; i < fnlen; ++i) | ||
fn[i].call(this, arguments[1]); | ||
break; | ||
case 3: | ||
fn[0].call(this, arguments[1], arguments[2]); | ||
fn[1].call(this, arguments[1], arguments[2]); | ||
if (fnlen === 2) break; | ||
fn[2].call(this, arguments[1], arguments[2]); | ||
if (fnlen === 3) break; | ||
fn[3].call(this, arguments[1], arguments[2]); | ||
if (fnlen === 4) break; | ||
fn[4].call(this, arguments[1], arguments[2]); | ||
if (fnlen === 5) break; | ||
for (i = 5; i < fnlen; ++i) | ||
fn[i].call(this, arguments[1], arguments[2]); | ||
break; | ||
case 4: | ||
fn[0].call(this, arguments[1], arguments[2], arguments[3]); | ||
fn[1].call(this, arguments[1], arguments[2], arguments[3]); | ||
if (fnlen === 2) break; | ||
fn[2].call(this, arguments[1], arguments[2], arguments[3]); | ||
if (fnlen === 3) break; | ||
fn[3].call(this, arguments[1], arguments[2], arguments[3]); | ||
if (fnlen === 4) break; | ||
fn[4].call(this, arguments[1], arguments[2], arguments[3]); | ||
if (fnlen === 5) break; | ||
for (i = 5; i < fnlen; ++i) | ||
fn[i].call(this, arguments[1], arguments[2], arguments[3]); | ||
break; | ||
default: | ||
args = new Array(len - 1); | ||
for (i = 1; i < len; i++) | ||
args[i - 1] = arguments[i]; | ||
fn[0].apply(this, args); | ||
fn[1].apply(this, args); | ||
if (fnlen === 2) break; | ||
fn[2].apply(this, args); | ||
if (fnlen === 3) break; | ||
fn[3].apply(this, args); | ||
if (fnlen === 4) break; | ||
fn[4].apply(this, args); | ||
if (fnlen === 5) break; | ||
for (i = 5; i < fnlen; ++i) | ||
fn[i].apply(this, args); | ||
} | ||
} | ||
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if (needDomainExit) | ||
|
@@ -230,7 +239,6 @@ EventEmitter.prototype.emit = function emit(type) { | |
}; | ||
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function _addListener(target, type, listener, prepend) { | ||
var m; | ||
var events; | ||
var existing; | ||
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@@ -275,7 +283,7 @@ function _addListener(target, type, listener, prepend) { | |
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// Check for listener leak | ||
if (!existing.warned) { | ||
m = $getMaxListeners(target); | ||
const m = $getMaxListeners(target); | ||
if (m && m > 0 && existing.length > m) { | ||
existing.warned = true; | ||
const w = new Error('Possible EventEmitter memory leak detected. ' + | ||
|
@@ -497,16 +505,31 @@ function spliceOne(list, index) { | |
} | ||
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function arrayClone(arr, n) { | ||
var copy = new Array(n); | ||
switch (n) { | ||
case 2: return [arr[0], arr[1]]; | ||
case 3: return [arr[0], arr[1], arr[2]]; | ||
case 4: return [arr[0], arr[1], arr[2], arr[3]]; | ||
case 5: return [arr[0], arr[1], arr[2], arr[3], arr[4]]; | ||
} | ||
const copy = new Array(n); | ||
for (var i = 0; i < n; ++i) | ||
copy[i] = arr[i]; | ||
return copy; | ||
} | ||
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function unwrapListeners(arr) { | ||
const ret = new Array(arr.length); | ||
for (var i = 0; i < ret.length; ++i) { | ||
ret[i] = arr[i].listener || arr[i]; | ||
const first = arr[0].listener || arr[0]; | ||
const second = arr[1].listener || arr[1]; | ||
const n = arr.length; | ||
switch (n) { | ||
case 2: return [first, second]; | ||
case 3: return [first, second, arr[2].listener || arr[2]]; | ||
case 4: return [first, second, arr[2].listener || arr[2], | ||
arr[3].listener || arr[3]]; | ||
default: | ||
const copy = new Array(n); | ||
for (var i = 0; i < n; ++i) | ||
copy[i] = arr[i].listener || arr[i]; | ||
return copy; | ||
} | ||
return ret; | ||
} |
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Maybe if simplified to will be faster?