private void cacheNextBlockHeader(final long offset, ByteBuff onDiskBlock,
      int onDiskSizeWithHeader, int headerLength) {
      PrefetchedHeader ph = new PrefetchedHeader();
      ph.offset = offset;
      onDiskBlock.get(onDiskSizeWithHeader, ph.header, 0, headerLength);
      this.prefetchedHeader.set(ph);
    }
Save away the next blocks header in atomic reference.
@see #getCachedHeader(long)
@see PrefetchedHeader
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlock.java