streams: Speed up by doing less work in the state ctors

lib/_stream_readable.js

@@ -24,7 +24,6 @@ Readable.ReadableState = ReadableState;
 
 var Stream = require('stream');
 var util = require('util');
-var assert = require('assert');
 var StringDecoder;
 
 util.inherits(Readable, Stream);
@@ -33,29 +32,21 @@ function ReadableState(options, stream) {
   options = options || {};
 
   // the argument passed to this._read(n,cb)
-  this.bufferSize = options.hasOwnProperty('bufferSize') ?
-      options.bufferSize : 16 * 1024;
+  this.bufferSize = options.bufferSize || 16 * 1024;
 
   // the point at which it stops calling _read() to fill the buffer
-  this.highWaterMark = options.hasOwnProperty('highWaterMark') ?
-      options.highWaterMark : 16 * 1024;
+  // Note: 0 is a valid value, means "don't call _read preemptively ever"
+  var hwm = options.highWaterMark;
+  this.highWaterMark = (hwm || hwm === 0) ? hwm : 16 * 1024;
 
   // the minimum number of bytes to buffer before emitting 'readable'
   // default to pushing everything out as fast as possible.
-  this.lowWaterMark = options.hasOwnProperty('lowWaterMark') ?
-      options.lowWaterMark : 0;
+  this.lowWaterMark = options.lowWaterMark || 0;
 
   // cast to ints.
-  assert(typeof this.bufferSize === 'number');
-  assert(typeof this.lowWaterMark === 'number');
-  assert(typeof this.highWaterMark === 'number');
   this.bufferSize = ~~this.bufferSize;
   this.lowWaterMark = ~~this.lowWaterMark;
   this.highWaterMark = ~~this.highWaterMark;
-  assert(this.bufferSize >= 0);
-  assert(this.lowWaterMark >= 0);
-  assert(this.highWaterMark >= this.lowWaterMark,
-         this.highWaterMark + '>=' + this.lowWaterMark);
 
   this.buffer = [];
   this.length = 0;

lib/_stream_writable.js

@@ -36,22 +36,18 @@ function WritableState(options, stream) {
   options = options || {};
 
   // the point at which write() starts returning false
-  this.highWaterMark = options.hasOwnProperty('highWaterMark') ?
-      options.highWaterMark : 16 * 1024;
+  // 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;
+  this.highWaterMark = (hwm || hwm === 0) ? hwm : 16 * 1024;
 
   // the point that it has to get to before we call _write(chunk,cb)
   // default to pushing everything out as fast as possible.
-  this.lowWaterMark = options.hasOwnProperty('lowWaterMark') ?
-      options.lowWaterMark : 0;
+  this.lowWaterMark = options.lowWaterMark || 0;
 
   // cast to ints.
-  assert(typeof this.lowWaterMark === 'number');
-  assert(typeof this.highWaterMark === 'number');
   this.lowWaterMark = ~~this.lowWaterMark;
   this.highWaterMark = ~~this.highWaterMark;
-  assert(this.lowWaterMark >= 0);
-  assert(this.highWaterMark >= this.lowWaterMark,
-         this.highWaterMark + '>=' + this.lowWaterMark);
 
   this.needDrain = false;
   // at the start of calling end()
@@ -66,8 +62,8 @@ 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.
-  this.decodeStrings = options.hasOwnProperty('decodeStrings') ?
-      options.decodeStrings : true;
+  var noDecode = options.decodeStrings === false;
+  this.decodeStrings = !noDecode;
 
   // not an actual buffer we keep track of, but a measurement
   // of how much we're waiting to get pushed to some underlying