code: public static int getCheckSumOctalBytes(long value, byte[] buf, int offset, int length) {
          TarHeader.getOctalBytes(value, buf, offset, length);
          buf[offset + length - 1] = (byte) ' ';
          buf[offset + length - 2] = 0;
          return offset + length;
      }
docs: Parse the checksum octal integer from a header buffer.
  
  @param header
  The header buffer from which to parse.
  @param offset
  The offset into the buffer from which to parse.
  @param length
  The number of header bytes to parse.
  @return The integer value of the entry's checksum.