void checkCacheTime(BucketEntry be) throws IOException {
    long offset = be.offset();
    ByteBuff dstBuff = be.allocator.allocate(Long.BYTES);
    try {
      accessFile(readAccessor, dstBuff, offset);
    } catch (IOException ioe) {
      dstBuff.release();
      throw ioe;
    }
    dstBuff.rewind();
    long cachedNanoTime = dstBuff.getLong();
    if (be.getCachedTime() != cachedNanoTime) {
      dstBuff.release();
      throw new HBaseIOException("The cached time recorded within the cached block: "
        + cachedNanoTime + " differs from its bucket entry: " + be.getCachedTime());
    }
  }
Transfers data from file to the given byte buffer
@param be an {@link BucketEntry} which maintains an (offset, len, refCnt)
@return the {@link Cacheable} with block data inside.
@throws IOException if any IO error happen.
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/bucket/FileIOEngine.java