stream: improve Transform performance

PR-URL: #13322 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Matteo Collina <[email protected]>

Author: mscdex

benchmark/streams/transform-creation.js

@@ -0,0 +1,23 @@
+'use strict';
+varcommon=require('../common.js');
+varTransform=require('stream').Transform;
+varinherits=require('util').inherits;
+
+varbench=common.createBenchmark(main,{
+n: [1e6]
+});
+
+functionMyTransform(){
+Transform.call(this);
+}
+inherits(MyTransform,Transform);
+MyTransform.prototype._transform=function(){};
+
+functionmain(conf){
+varn=+conf.n;
+
+bench.start();
+for(vari=0;i<n;++i)
+newMyTransform();
+bench.end(n);
+}

lib/_stream_transform.js

@@ -70,41 +70,29 @@ const util = require('util');
 util.inherits(Transform,Duplex);
 
 
-functionTransformState(stream){
-this.afterTransform=function(er,data){
-returnafterTransform(stream,er,data);
-};
-
-this.needTransform=false;
-this.transforming=false;
-this.writecb=null;
-this.writechunk=null;
-this.writeencoding=null;
-}
-
-functionafterTransform(stream,er,data){
-varts=stream._transformState;
+functionafterTransform(er,data){
+varts=this._transformState;
 ts.transforming=false;
 
 varcb=ts.writecb;
 
 if(!cb){
-returnstream.emit('error',
-newError('write callback called multiple times'));
+returnthis.emit('error',
+newError('write callback called multiple times'));
 }
 
 ts.writechunk=null;
 ts.writecb=null;
 
-if(data!==null&&data!==undefined)
-stream.push(data);
+if(data!=null)// single equals check for both `null` and `undefined`
+this.push(data);
 
 cb(er);
 
-varrs=stream._readableState;
+varrs=this._readableState;
 rs.reading=false;
 if(rs.needReadable||rs.length<rs.highWaterMark){
-stream._read(rs.highWaterMark);
+this._read(rs.highWaterMark);
 }
 }
 
@@ -115,9 +103,14 @@ function Transform(options){
 
 Duplex.call(this,options);
 
-this._transformState=newTransformState(this);
-
-varstream=this;
+this._transformState={
+afterTransform: afterTransform.bind(this),
+needTransform: false,
+transforming: false,
+writecb: null,
+writechunk: null,
+writeencoding: null
+};
 
 // start out asking for a readable event once data is transformed.
 this._readableState.needReadable=true;
@@ -136,14 +129,17 @@ function Transform(options){
 }
 
 // When the writable side finishes, then flush out anything remaining.
-this.once('prefinish',function(){
-if(typeofthis._flush==='function')
-this._flush(function(er,data){
-done(stream,er,data);
-});
-else
-done(stream);
-});
+this.on('prefinish',prefinish);
+}
+
+functionprefinish(){
+if(typeofthis._flush==='function'){
+this._flush((er,data)=>{
+done(this,er,data);
+});
+}else{
+done(this,null,null);
+}
 }
 
 Transform.prototype.push=function(chunk,encoding){
@@ -208,18 +204,15 @@ function done(stream, er, data){
 if(er)
 returnstream.emit('error',er);
 
-if(data!==null&&data!==undefined)
+if(data!=null)// single equals check for both `null` and `undefined`
 stream.push(data);
 
 // if there's nothing in the write buffer, then that means
 // that nothing more will ever be provided
-varws=stream._writableState;
-varts=stream._transformState;
-
-if(ws.length)
+if(stream._writableState.length)
 thrownewError('Calling transform done when ws.length != 0');
 
-if(ts.transforming)
+if(stream._transformState.transforming)
 thrownewError('Calling transform done when still transforming');
 
 returnstream.push(null);