@Override
    public void unbufferStream() {
      // To handle concurrent reads, ensure that no other client is accessing the streams while we
      // unbuffer it.
      if (streamLock.tryLock()) {
        try {
          this.streamWrapper.unbuffer();
        } finally {
          streamLock.unlock();
        }
      }
    }
Generates the checksum for the header as well as the data and then validates it. If the block
doesn't uses checksum, returns false.
@return True if checksum matches, else false.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlock.java