Build msgpack for micropython

[bokolob]

Hello.

I'm a newbie in python and especially micropython worlds, so I need some help Could somebody give me a clue how I could build msgpack (https://github.com/msgpack/msgpack-python). Maybe somebody had done it already. Or maybe there is an instruction (not about this library but general one)?

I know, there is a pure-python library, but I want to try binary one.

[jimmo]

I'm a newbie in python and especially micropython worlds, so I need some help Could somebody give me a clue how I could build msgpack (https://github.com/msgpack/msgpack-python). Maybe somebody had done it already. Or maybe there is an instruction (not about this library but general one)?

Unfortunately this is not a simple process as the way CPython bindings work is very different to MicroPython bindings.

The starting point for extending MicroPython in C would be http://docs.micropython.org/en/latest/d ... dules.html

[bokolob]

Thanks.
Is there some examples of iterating through an object content in C ? How to walk trough all the fields recursively ?

[jimmo]

Is there some examples of iterating through an object content in C ? How to walk trough all the fields recursively ?

I wish I could just say "look at how the JSON serialiser works" -- https://github.com/micropython/micropyt ... modujson.c

Unfortunately, it's a bit complicated because the JSON serialiser is part of the core... you'll see the key line in modujson.c is:

Code: Select all

mp_obj_print_helper(&print, obj, PRINT_JSON);

But you can follow the implementation of print and the various places that PRINT_JSON is used and get some hints.

However, in general the way to walk an object is via iterable:

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mp_obj_t iter = mp_getiter(iterable, NULL);
mp_obj_t item;
while ((item = mp_iternext(iter)) != MP_OBJ_STOP_ITERATION) {
    // do something with item
}

[pythoncoder]

I appreciate this doesn't answer your question, but this doc describes the four serialisation protocols which do work with MicroPython. Alas msgpack is not one of them.

[bokolob]

I need some serialiser that is efficient for the cpu (to consume less battery) and the result "size" (to consume less network). About that four serializers - json is fast, but its result is longer, other libraries are pure python, and I suppose that they are quite slow..

[bokolob]

Isn't it a good ide to add other serialisers into core? At the same level as json is? They can be disabled with preprocessor directives.
Msgpack has C-library that could be used.

[stijn]

See https://github.com/micropython/micropython/issues/4241
In short: the fallback implementation of msgpack is pure Python and almost works out of the box

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Isn't it a good ide to add other serialisers into core? 

There are just too many of them to choose. Also see e.g. https://github.com/micropython/micropython/issues/5597

[bokolob]

I know about that library, but I suppose it would be too slow and inefficient for IO-heavy applications (on microcontroller). And in my case every uA of battery is crucial.

[stijn]

I suppose it would be too slow.

That is understandable, but unless you actually measure it you don't know for sure.