nodejs · mscdex · Mar 17, 2018
diff --git a/benchmark/streams/creation.js b/benchmark/streams/creation.js
@@ -0,0 +1,55 @@
+'use strict';
+const common = require('../common.js');
+const Duplex = require('stream').Duplex;
+const Readable = require('stream').Readable;
+const Transform = require('stream').Transform;
+const Writable = require('stream').Writable;
+
+const bench = common.createBenchmark(main, {
+  n: [50e6],
+  kind: ['duplex', 'readable', 'transform', 'writable']
+});
+
+function main({ n, kind }) {
+  var i = 0;
+  switch (kind) {
+    case 'duplex':
+      new Duplex({});
+      new Duplex();
+
+      bench.start();
+      for (; i < n; ++i)
+        new Duplex();
+      bench.end(n);
+      break;
+    case 'readable':
+      new Readable({});
+      new Readable();
+
+      bench.start();
+      for (; i < n; ++i)
+        new Readable();
+      bench.end(n);
+      break;
+    case 'writable':
+      new Writable({});
+      new Writable();
+
+      bench.start();
+      for (; i < n; ++i)
+        new Writable();
+      bench.end(n);
+      break;
+    case 'transform':
+      new Transform({});
+      new Transform();
+
+      bench.start();
+      for (; i < n; ++i)
+        new Transform();
+      bench.end(n);
+      break;
+    default:
+      throw new Error('Invalid kind');
+  }
+}
diff --git a/benchmark/streams/transform-creation.js b/benchmark/streams/transform-creation.js
diff --git a/lib/_stream_readable.js b/lib/_stream_readable.js
@@ -64,15 +64,16 @@ function prependListener(emitter, event, fn) {
     emitter._events[event] = [fn, emitter._events[event]];
 }
 
-function ReadableState(options, stream) {
+function ReadableState(options, stream, isDuplex) {
   options = options || {};
 
   // Duplex streams are both readable and writable, but share
   // the same options object.
   // However, some cases require setting options to different
   // values for the readable and the writable sides of the duplex stream.
   // These options can be provided separately as readableXXX and writableXXX.
-  var isDuplex = stream instanceof Stream.Duplex;
+  if (typeof isDuplex !== 'boolean')
+    isDuplex = stream instanceof Stream.Duplex;
 
   // object stream flag. Used to make read(n) ignore n and to
   // make all the buffer merging and length checks go away
@@ -142,7 +143,11 @@ function Readable(options) {
   if (!(this instanceof Readable))
     return new Readable(options);
 
-  this._readableState = new ReadableState(options, this);
+  // Checking for a Stream.Duplex instance is faster here instead of inside
+  // the ReadableState constructor, at least with V8 6.5
+  const isDuplex = (this instanceof Stream.Duplex);
+
+  this._readableState = new ReadableState(options, this, isDuplex);
 
   // legacy
   this.readable = true;

diff --git a/lib/_stream_writable.js b/lib/_stream_writable.js
@@ -48,15 +48,16 @@ util.inherits(Writable, Stream);
 
 function nop() {}
 
-function WritableState(options, stream) {
+function WritableState(options, stream, isDuplex) {
   options = options || {};
 
   // Duplex streams are both readable and writable, but share
   // the same options object.
   // However, some cases require setting options to different
   // values for the readable and the writable sides of the duplex stream.
   // These options can be provided separately as readableXXX and writableXXX.
-  var isDuplex = stream instanceof Stream.Duplex;
+  if (typeof isDuplex !== 'boolean')
+    isDuplex = stream instanceof Stream.Duplex;
 
   // object stream flag to indicate whether or not this stream
   // contains buffers or objects.
@@ -201,12 +202,15 @@ function Writable(options) {
   // Trying to use the custom `instanceof` for Writable here will also break the
   // Node.js LazyTransform implementation, which has a non-trivial getter for
   // `_writableState` that would lead to infinite recursion.
-  if (!(realHasInstance.call(Writable, this)) &&
-      !(this instanceof Stream.Duplex)) {
+
+  // Checking for a Stream.Duplex instance is faster here instead of inside
+  // the WritableState constructor, at least with V8 6.5
+  const isDuplex = (this instanceof Stream.Duplex);
+
+  if (!isDuplex && !realHasInstance.call(Writable, this))
     return new Writable(options);
-  }
 
-  this._writableState = new WritableState(options, this);
+  this._writableState = new WritableState(options, this, isDuplex);
 
   // legacy.
   this.writable = true;