feat: msgpack encoding

[lino-levan]

Closes #2194.

[lino-levan]

I should note that I plan for at least one follow-up PR. We don't support the timestamp extension to the spec yet, but I think that's fine for making the first PR reviewable.

[aapoalas]

Nice work in general! Needs a bit of work.

[nmarks413]

lgtm

[idranme]

@aapoalas What do you think?

[aapoalas]

I'll try to review this fully in some hours.

[lino-levan]

How am I failing CI if main isn't? Super strange.

[aapoalas]

Found some nits to pick and a few remaining issues from the encode side.

[aapoalas]

Nice work! I think in a followup we could try to optimise the encoding side via eg. eagerly allocating a larger buffer that we use as needed and reallocate a bigger one if needed. Or we could precalculate the size we need (strings would need to be "eyeballed" or allocated to the theoretical maximum of length * 3).

Also, an "encodeInto" API is probably a good idea in the future.

[lino-levan]

Lots of good ideas for follow up PRs. Copying this from discord so that we have all of the ideas in the same thread:

Later we'll probably want encode options in the vein of:

• BigInt representation: Always 64 bit / Size-optimized
• Number representation: Always f64 / Size-optimized
• Undefined representation: Not allowed / Use null / Ignore in maps

And decode options to go with them:

• 64-bit integers: Mixed / Always BigInt / Always number (unsafe)
• Small integers: Number / BigInt

[lino-levan]

Let me finish up some final cleanups around comments and bitshift stuff and I think this PR is good.

[lino-levan]

@kt3k please take a look!

[idranme]

@kt3k What do you think?

[kt3k]

Does this mean integer type in msgpack could become both number and bigint in JS? Is this the same as the other decoders such as msgpackr?

[lino-levan]

Does this mean integer type in msgpack could become both number and bigint in JS?

There are multiple integer types, but yes. Some integer types (u64 + i64) will be converted to a bigint instead of a number.

Is this the same as the other decoders such as msgpackr?

It appears that msgpack does the same thing (always storing it in a u64/i64 and erroring out if the number is too big)

[kt3k]

Let's add jsdocs to encode and decode with examples. Those will be main docs for this module.

[kt3k]

Other part looks good to me

[kt3k]

LGTM. Looks nice addition to std. Thanks for your contribution! @lino-levan