@Override
  public void close() throws IOException {
    channel.close();
    MmapUtil.clean(dataBuffer);
    MmapUtil.clean(compressedBuffer);
    dataBuffer = null;
    compressedBuffer = null;
  }
1 byte for whether enable compression, 4 byte for compressedSize
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/wal/io/WALInputStream.java