import org.apache.hadoop.hbase.util.Bytes;

public class RowKeyConverter {

  private static final int STATION_ID_LENGTH = 12;

  /**
   * @return A row key whose format is: <station_id> <reverse_order_timestamp>
   */
  public static byte[] makeObservationRowKey(String stationId,
      long observationTime) {
    byte[] row = new byte[STATION_ID_LENGTH + Bytes.SIZEOF_LONG];
    Bytes.putBytes(row, 0, Bytes.toBytes(stationId), 0, STATION_ID_LENGTH);
    long reverseOrderTimestamp = Long.MAX_VALUE - observationTime;
    Bytes.putLong(row, STATION_ID_LENGTH, reverseOrderTimestamp);
    return row;
  }
}