public SeekableByteChannel getRWChannel() throws IOException {
      java.nio.file.Path p = FileSystems.getDefault().getPath(path.toString());
      return Files.newByteChannel(p, StandardOpenOption.READ, StandardOpenOption.WRITE,
        StandardOpenOption.DSYNC);
    }
Enables writing and rewriting portions of the file backing an {@link HFileBlock}.
hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/TestHFileBlockHeaderCorruption.java