HSM + state-machine-cat

[edbek]

as a suggestion: can you link your amast(HSM) project with the https://state-machine-cat.js.org/ project so that based on the JSON-file obtained from state-machine-cat, it could be launched under your HSM project?

[adel-mamin]

Hi Eduard,

Maybe you could elaborate, but I take you are asking if an HSM description in JSON format could be converted to HSM implementation in C code using amast HSM library. Something like a standalone CLI utility?

I have not used state-machine-cat in the past, so if you have any example JSON description of an HSM, please share to get a better idea how it looks like.

[edbek]

I imagine it this way:

1. transform the JSON-schema "smcat-ast.schema.json" into a C code source file that can work at the object level with any JSON file obtained during the construction of the state machine in https://state-machine-cat.js.org/.
   Such a С source file can be obtained from the site https://app.quicktype.io/ by entering Source type = "JSON file schema" and the C language (cJSON).
   This way, there is access to the structure of any JSON file obtained by state-machine-cat.

2. the obtained C code source file will need to be linked to the logic of your HSM and EVENT. In essence, you will get an HSM interpreter.

Thus, state-machine-cat gives us a JSON file for any arbitrary constructed state machine. We load this file into your interpreter project, where it undergoes constant interpretation based on emerging events.

[adel-mamin]

It looks to me that your 1st step could essentially be implemented by doing json = cJSON_Parse(json_data_str);, where json_data_str is the full content of JSON formatted state machine description produced by state-machine-cat.

Your second step, as I understand it, is about producing C code of HSM out of the JSON object (json in above example).

Is this what you call HSM interpreter?

So, the user workflow is going to be something like this:

1. create HSM using state-machine-cat DSL.
2. generate JSON description of it by running smcat -T json user_hsm.smcat -o user_hsm.json
3. generate user_hsm.h and user_hsm.c by running amgen -i user_hsm.json -o user_hsm, where amgen is the converter utility, which takes the HSM JSON description and produces two files: C header and source of the resulting HSM using amast HSM lib.

Did I understand it right?

[edbek]

According to your proposal, we get the HSM compiler. This path may be more complicated.

I proposed the path of the HSM interpreter, which will walk along the structure of the JSON file obtained using cJSON_Parse(). And this walking along this structure will be determined by events, and executed by your HSM code.

II find the HSM interpreter more interesting than the compiler (though that is also important if you can do it) since the smcat JSON file can be sent remotely to the device and executed as a separate task.

[adel-mamin]

Right, I was talking about compiler.

What you describe sounds like an interesting idea. Although I am still trying to understand your proposal.

So, the interpreter is going to be a C code, which takes HSM JSON description as a string at initialization and then can accept events and execute them with the state machine.

Is this a correct picture?

Then I take the events are going to be just strings or IDs as they are described in JSON. What about the actions? They are defined as strings in the examples I saw. Just call printf() for them? Or maybe call some callbacks?

How do you see the API of the interpreter?

[edbek]

Yes, that's right. This is the correct picture.

And as you correctly pointed out, you can use callbacks of functions that should already be in the main application that launches the interpreter with the JSON file state-machine-cat.

But the choice is yours.
The main task is to launch the JSON file state-machine-cat into operation on IoT devices.

[adel-mamin]

Thank you for the input so far.

Let me review the design options and then I will come back to you with some ideas for further iteration.

[edbek]

Thank you also for your work. I am always in touch for further discussions.

[adel-mamin]

I added the initial draft in this PR. Any comments are welcome.