code: function WritableFileStream(file, options) {
  	if ( !(this instanceof WritableFileStream) ) {
  		return new WritableFileStream(file, options);
  	}
  	Stream.call(this);
  	options = options || {};
  	this._file = file;
  	this._bufferSize = options.bufferSize || 0;
  	this._flags = options.flags || 'a';
  	this._mode = options.mode || parseInt('0644', 8);
  	this._encoding = options.encoding || 'utf8';
  
  	this._stream = null;
  	this._isReopening = false;
  	this._buffer = null;
  	this._open();
  
  	/** @see https://github.com/dominictarr/stream-spec/blob/master/stream_spec.md#writablestream **/
  	this.writable = false;
  }
docs: WritableFileStream
  
  @param {String} file Writable file name
  @param {[Integer]} options.bufferSize write memory buffer size, default: 0
  @param {[String]} options.flags fileopen flags, default: 'a'
  @param {[Integer]} options.mode Fileopen mode, default: 0644
  @param {[String]} options.encoding write stream encoding, default: utf8