public void writeSingleLevelIndex(DataOutput out, String description) throws IOException {
      expectNumLevels(1);

      if (!singleLevelOnly) throw new IOException("Single-level mode is turned off");

      if (rootChunk.getNumEntries() > 0)
        throw new IOException("Root-level entries already added in " + "single-level mode");

      rootChunk = curInlineChunk;
      curInlineChunk = new BlockIndexChunkImpl();

      if (LOG.isTraceEnabled()) {
        LOG.trace("Wrote a single-level " + description + " index with " + rootChunk.getNumEntries()
          + " entries, " + rootChunk.getRootSize() + " bytes");
      }
      indexBlockEncoder.encode(rootChunk, true, out);
    }
Writes the block index data as a single level only. Does not do any block framing.
@param out         the buffered output stream to write the index to. Typically a stream
                   writing into an {@link HFile} block.
@param description a short description of the index being written. Used in a log message.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlockIndex.java