fs: refactor fs for performance

lib/_stream_readable.js

@@ -66,7 +66,7 @@ function ReadableState(options, stream) {
   // 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;
+  const 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
@@ -77,19 +77,15 @@ function ReadableState(options, stream) {
 
   // the point at which it stops calling _read() to fill the buffer
   // Note: 0 is a valid value, means "don't call _read preemptively ever"
-  var hwm = options.highWaterMark;
-  var readableHwm = options.readableHighWaterMark;
-  var defaultHwm = this.objectMode ? 16 : 16 * 1024;
+  const hwm = options.highWaterMark;
+  const readableHwm = options.readableHighWaterMark;
 
   if (hwm || hwm === 0)
-    this.highWaterMark = hwm;
+    this.highWaterMark = Math.floor(hwm);
   else if (isDuplex && (readableHwm || readableHwm === 0))
-    this.highWaterMark = readableHwm;
+    this.highWaterMark = Math.floor(readableHwm);
   else
-    this.highWaterMark = defaultHwm;
-
-  // cast to ints.
-  this.highWaterMark = Math.floor(this.highWaterMark);
+    this.highWaterMark = this.objectMode ? 16 : 16 * 1024;
 
   // A linked list is used to store data chunks instead of an array because the
   // linked list can remove elements from the beginning faster than

lib/_stream_writable.js

@@ -46,7 +46,7 @@ function WritableState(options, stream) {
   // 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;
+  const isDuplex = stream instanceof Stream.Duplex;
 
   // object stream flag to indicate whether or not this stream
   // contains buffers or objects.
@@ -58,19 +58,15 @@ function WritableState(options, stream) {
   // the point at which write() starts returning false
   // Note: 0 is a valid value, means that we always return false if
   // the entire buffer is not flushed immediately on write()
-  var hwm = options.highWaterMark;
-  var writableHwm = options.writableHighWaterMark;
-  var defaultHwm = this.objectMode ? 16 : 16 * 1024;
+  const hwm = options.highWaterMark;
+  const writableHwm = options.writableHighWaterMark;
 
   if (hwm || hwm === 0)
-    this.highWaterMark = hwm;
+    this.highWaterMark = Math.floor(hwm);
   else if (isDuplex && (writableHwm || writableHwm === 0))
-    this.highWaterMark = writableHwm;
+    this.highWaterMark = Math.floor(writableHwm);
   else
-    this.highWaterMark = defaultHwm;
-
-  // cast to ints.
-  this.highWaterMark = Math.floor(this.highWaterMark);
+    this.highWaterMark = this.objectMode ? 16 : 16 * 1024;
 
   // if _final has been called
   this.finalCalled = false;
@@ -90,7 +86,7 @@ function WritableState(options, stream) {
   // should we decode strings into buffers before passing to _write?
   // this is here so that some node-core streams can optimize string
   // handling at a lower level.
-  var noDecode = options.decodeStrings === false;
+  const noDecode = options.decodeStrings === false;
   this.decodeStrings = !noDecode;
 
   // Crypto is kind of old and crusty.  Historically, its default string
@@ -148,7 +144,7 @@ function WritableState(options, stream) {
 
   // allocate the first CorkedRequest, there is always
   // one allocated and free to use, and we maintain at most two
-  var corkReq = { next: null, entry: null, finish: undefined };
+  const corkReq = { next: null, entry: null, finish: undefined };
   corkReq.finish = onCorkedFinish.bind(undefined, corkReq, this);
   this.corkedRequestsFree = corkReq;
 }

lib/buffer.js

@@ -441,7 +441,7 @@ Buffer.compare = function compare(a, b) {
 
 Buffer.isEncoding = function isEncoding(encoding) {
   return typeof encoding === 'string' &&
-         typeof normalizeEncoding(encoding) === 'string';
+         normalizeEncoding(encoding) !== undefined;
 };
 Buffer[kIsEncodingSymbol] = Buffer.isEncoding;
 
@@ -465,7 +465,7 @@ Buffer.concat = function concat(list, length) {
     length = length >>> 0;
   }
 
-  var buffer = Buffer.allocUnsafe(length);
+  const buffer = Buffer.allocUnsafe(length);
   var pos = 0;
   for (i = 0; i < list.length; i++) {
     var buf = list[i];