code: public void setDataPosition(int pos) {
        if (pos > dataSize) {
          // NOTE: Real parcel ignores this until a write occurs.
          throw new UnreliableBehaviorError(pos + " greater than dataSize " + dataSize);
        }
        dataPosition = pos;
        failNextReadIfPastEnd = false;
      }
docs: Sets the current data position.
  
  @param pos
  Desired position in bytes