Calendar for time series

[JRoehrig]

A Calendar without the size overload from java.util.Calendar could be useful to work with time series from sensors. I did one similar to DateManagement, i.e. using only a long integer and an (static) time offset from chip time. I will upload it into a fork.

[JRoehrig]

See my commit here:
22f0fb8

[fclairamb]

How can it be useful ? How do you use it yourself ?

I'm using timeseries on the server side (using SQL & NoSQL database like cassandra) but I never use them on the device side. I just send data and store it to be sent afterwards when there are communication issues.

[JRoehrig]

First of all thank you for providing your lib.

The class is only a wrapper to transform time in milliseconds into calendar (e.g. 13.02.2014 01:30). I retrieve records with date and time from hydro-meterological sensors, save the data and send it per ftp. Each record has an attribute ShortCalendar and further hydro-meteo stuff. Indeed it allocates less memory using only the long integer instead of the object ShortCalendar, but the code is much easier to read an debug with Calendar objects. On the other had, the size of java.util.Calendar is prohibitive, some hundredths of bytes I guess.
In fact it is possible to work only with milliseconds in time series, but not so practical. ShortCalendar should be more or less like a GregorianCalendar, but thinner.
If you intend to use it, maybe you want to give a better name then ShortCalendar to the class and incorporate the static methods from DateManagement into it. I can also do it.
Some examples of use:

1. I retrieve data from some sensors with embedded dataloggers. The datalogger does not guarantee sorted records. I create objects using sc[0..n] = ShortCalendar(yy, MM, dd, hh, mm, ss) and sort them with sc0.compare(sc1).

2. To request data via sms "from to", the same: I parse both "from to" into Calendar and search for the records in the flash-datalogger, comparing their dates to from and to

3. to get data from the last e.g. three days: sc0.addDay(-3)

4. Example from one sensor:
   WeatherLinkSensor.assertACK(data, 0, 1)
   int date = (((sc.getYear() - 2000) << 9) & 0xFE00) + ((sc.getMonth() << 5) & 0x01E0) + ...
   int time = sc.getHour() * 100 + sc.getMinute();

5. In another place
   assertACK(data, 0, data.length);
   data = new byte[]{
   (byte) 0, (byte) sc1.getMinute(), (byte) sc1.getHour(),
   (byte) sc1.getDay(), (byte) sc1.getMonth(), (byte) (sc1.getYear() - 1900),
   0, 0
   };
   int crc = CRC.doCRC_CCITT_XModem(0, 6, data);

6. in a class public SMSIncomingMessage(String from, ShortCalendar cal, String content) because my TimeInitializer uses also sms if GPRS is down (for http)