DataInputStream getByteStream() {
    ByteBuff dup = this.bufWithoutChecksum.duplicate();
    dup.position(this.headerSize());
    return new DataInputStream(new ByteBuffInputStream(dup));
  }
Returns a byte stream reading the data(excluding header and checksum) of this block
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlock.java