private static String getReceiverDir() {
    return CommonDescriptor.getInstance().getConfig().getSyncDir()
        + File.separator
        + RECEIVER_DIR_NAME;
  }
Get current FileStartIndex.

@return startIndex of file: -1 if file doesn't exist
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/pipe/receiver/protocol/legacy/IoTDBLegacyPipeReceiverAgent.java