public static int headerSize(boolean usesHBaseChecksum) {
    return usesHBaseChecksum
      ? HConstants.HFILEBLOCK_HEADER_SIZE
      : HConstants.HFILEBLOCK_HEADER_SIZE_NO_CHECKSUM;
  }
Maps a minor version to the size of the header.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlock.java