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This is really a question on how to use GetStateInformation() and SetStateInformation(). How do you pass different information into and out of the byte arrays those routines use for data transfer? In C or C++ the method would involve casting to a pointer type, but that's not an option in Java, and I can't find any sample code that shows how to do it. For instance, how would you save (or restore) say, a double, or a String to/from a byte array. I suppose for a string you could split out the characters one at a time and save them (although I'd bet character typing would get in the way), and it just don't seem right to break up a double by masking to get at byte-sized chunks. So I'm guessing there's some idiosyncratic syntax for doing this, and I'd really appreciate it if some kind soul would take pity on a poor ignorant code monkey and tell me what it is. Thanks.

Reid

Hi Reid,

I find using java.nio.ByteBuffer is very convenient for me when I'm implementing GetStateInformation() and SetStateInformation().

In GetStateInformation() I would do something like Then I use the putInt(), putDouble(), put() and similar methods of the ByteBuffer to fill it with the data I want to store. Strings can be stored like and add its length + 4 byte (for an int to store the length of stringBytes) to bufSize.
The final line in GetStateInformation() is then In SetStateInformation(byte[] stateInfo) I basically do it the other way around. I use to turn the byte[] into a ByteBuffer. The I use the getInt(), getDouble(), get() methods of the ByteBuffer to retrieve the information stored in the byte[].

In general you need to think of a "format" or "order" in which you want/need to store your data so you can easily get it back from the byte[], e.g. store the length of strings or data with variable size in general.

Hope this helps. Best regards,
Martin

Idiosyncratic I said, and idiosyncratic it is. Don't think that solution would have occurred to me, as that's a part of the library I'm not familiar with. Thanks mucho, mi amigo!

Reid

Good advice from Martin.

ByteBuffer is a great class, it all works and makes sense and saves you having to worry about a lot of things but it still feels a little clumsy converting between byte[] and ByteBuffer on top of the other conversions.

I still consider myself a beginner in Java so might be missing an easier way but I ended up with ByteBuffer.allocate( Integer.BYTES ).putInt( i ).array() as the correct way to convert an integer to a byte array. Which does look a little idiosyncratic. I have a small number of helper functions that wrap such weird stuff up, so for instance the above becomes just intAsByteArray( i ) in my main code.

For simple modules I just write String asString() and void fromString( String s ) methods to convert module state to a string and a string to module state and then use ...
I use the same methods to perform undo and redo.

Using strings for state is also handy for debugging as you can just look at the string.

Thanks, to both of you! I'm busy reading up on that end of the library, now that I'm aware of it. Since I'm coming from C++, idiosyncratic doesn't bother me.