private boolean checkCheckSumTypeOnHeaderBuf(ByteBuff headerBuf) {
      if (headerBuf == null) {
        return true;
      }
      byte b = headerBuf.get(HFileBlock.Header.CHECKSUM_TYPE_INDEX);
      for (ChecksumType t : ChecksumType.values()) {
        if (t.getCode() == b) {
          return true;
        }
      }
      return false;
    }
Check that checksumType on {@code headerBuf} read from a block header seems reasonable,
within the known value range.
@return {@code true} if the headerBuf is safe to proceed, {@code false} otherwise.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlock.java