code: @Override
      public long getTotalBytes() {
          if (!useLoadBuf) {
              return in.capacity();
          }
          try {
              return channelSize;
          } catch (Exception e) {
              log.error("Error getTotalBytes", e);
              return 0;
          }
      }
docs: Get the total readable bytes in a file or ByteBuffer.
  
  @return Total readable bytes