@Override
  public SubscriptionPollPayload deserialize(final ByteBuffer buffer) {
    commitContext = SubscriptionCommitContext.deserialize(buffer);
    writingOffset = ReadWriteIOUtils.readLong(buffer);
    return this;
  }
The offset from which the file content should be read.
iotdb-client/service-rpc/src/main/java/org/apache/iotdb/rpc/subscription/payload/poll/PollFilePayload.java