@Override
    protected HFileBlock readBlockDataInternal(FSDataInputStream is, long offset,
      long onDiskSizeWithHeaderL, boolean pread, boolean verifyChecksum, boolean updateMetrics,
      boolean useHeap) throws IOException {
      if (verifyChecksum) {
        corruptDataStream = true;
      }
      HFileBlock b = super.readBlockDataInternal(is, offset, onDiskSizeWithHeaderL, pread,
        verifyChecksum, updateMetrics, useHeap);
      corruptDataStream = false;
      return b;
    }
If set to true, corrupt reads using readAtOffset(...).
hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/TestChecksum.java