public void addEntry(byte[] firstKey, long blockOffset, int blockDataSize) {
      curInlineChunk.add(firstKey, blockOffset, blockDataSize);
      ++totalNumEntries;
    }
Add one index entry to the current leaf-level block. When the leaf-level block gets large
enough, it will be flushed to disk as an inline block.
@param firstKey      the first key of the data block
@param blockOffset   the offset of the data block
@param blockDataSize the on-disk size of the data block ({@link HFile} format version 2), or
                     the uncompressed size of the data block ( {@link HFile} format version
                     1).
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlockIndex.java