Implement coder module

[TerryE]

Implement coder module with methods:

• toBase64
• fromBase64
• toHex
• fromHex

Denormalise crypto to call the coder.toXXX routines. Discussion on #486 refers

[marcelstoer]

Denormalise crypto to call the coder.toXXX routines.

Not sure I understand.

Would that be the first time that two non-core modules actually depend on each other (see #386 (comment))? Why wouldn't you want to remove the methods in crypto? Calling the old crypto.xxx functions would still fail on a firmware that doesn't have the coder module, right?

[jmattsson]

Hmm, that's a good point. I hadn't thought of that added complication for the backwards compatibiilty. Maybe that's enough to not do it and "fix it in documentation" instead? From a user perspective I'd still prefer backwards compatibility, but I definitely hear you on the technical difficulties.

Maybe we should start out with an

#if defined(LUA_USE_MODULES_CRYPTO) && !defined(LUA_USE_MODULES_CODER)
# define LUA_USE_MODULES_CODER
#endif

and then officially split them a bit later down the track when we feel we have time to maintain "stuff that has changed from version x to y that you need to be aware of" notes?

[marcelstoer]

A software that is properly released usually has some deprecation policy based on a release plan in place. We don't have that and would have to rely on time-based deprecation. That would/could mean we create the new module, copy the methods and add a deprecation note to the docs for crypto. It could state that the deprecated methods are removed in n weeks or months.

[TerryE]

I can leave the old code in crypto with a #ifdef LUA_USE_MODULES_CODER option to substitute the the calls to coder instead. But I won't add any new methods to crypto.

[Alkorin]

encoding isn't a better name than coder ?
It's the name of golang's package for this kind of stuff

https://golang.org/pkg/encoding/hex/
https://golang.org/pkg/encoding/base64/

[TerryE]

Done

[devyte]

@TerryE Thank you for this, I really want to get rid of the lua implementation of fromBase64() in my code.
@marcelstoer Is it possible to add the encoder module to the nodemcu firmware build service?

[marcelstoer]

Yes, it is possible and sooner or later I will. There are a number of other modules that were merged into the dev branch recently which are not yet integrated into the cloud builder.

[jmattsson]

One of these days we'll get a chance to rework how the whole module inclusion system works, and hopefully to something the cloud builder automatically picks up on.