Thanks! Sorry it's taken a while to get back to you. Looking at this code, it seems that there are actually quite a few memory leaks, which could be causing you problems. Basically pretty much every time you get a pointer to a JsVar, you need to call jsvUnLock - for instance when you do jsvObjectSetChild you'd need to do it on what is returned.

If you created a test that went in the tests directory, and then tested it on the standard Linux compile of Espruino ./espruino --test tests/test_sha.js then it should tell you if it thinks there are any memory leaks.

As far as I can see, all leaks are gone. But i can't get 384 & 512 to work. My guess is that the Espruino runs out of memory or some kind of issue with uint64 or the sha512_ctx itself.

Triggering every minute, my code has now been running for a week non-stop. Performing SHA256 HMAC on a JSON object with five 1-wire sensors.

I decided not to merge the HMAC C code. Since It only took me about 70 lines of JS code to create a working HMAC library on top of hashlib. This library will be added to EspruinoDocs if hashlib gets accepted into mainline.

Thanks! looks really good.