code: function SingleType(value, nbBytes, readBufferCallback, writeBufferCallback, opt){
  	Type.call(this, opt);
  	this.value = value || 0;
  	this.nbBytes = nbBytes;
  	this.readBufferCallback = readBufferCallback;
  	this.writeBufferCallback = writeBufferCallback;
  }
docs: Leaf of tree type
  @param {number} value of type
  @param {function} readBufferCallback Buffer prototype read function
  @param {function} writeBufferCallback Buffer prototype write function
  @param {object} opt Type parameter