code: @Override
    public int read(byte []buffer, int offset, int length)
      throws IOException
    {
      int sublen = _next.read(buffer, offset, length);
      
      if (sublen <= 0) {
        return 0;
      }
      
      _crc = Crc64.generate(_crc, buffer, offset, sublen);
      
      _length += sublen;
      
      return sublen;
    }
docs: Writes a buffer to the underlying stream.
  
  @param buffer the byte array to write.
  @param offset the offset into the byte array.
  @param length the number of bytes to write.
  @param
  @Override isEnd true when the write is flushing a close.