TAI64 library for std

[kristate]

Implements TAI64N

https://cr.yp.to/libtai/tai64.html

[andrewrk]

Thanks for the implementation.

If this standard is popular enough, I think it makes sense for it to be the type returned by the cross platform abstraction for getting the current time.

[andrewrk]

Why store this encoded? Seems like this should be:

sec: u64,
nsec: u30,

to_bytes can be:

pub fn encode(self: TAI64N) [12]u8 {
    var result: [12]u8 = undefined;
    mem.writeInt(result[0..8], self.sec, builtin.Endian.Big);
    mem.writeInt(result[8..12], self.nsec, builtin.Endian.Big);
    return result;
}

Then we can have a corresponding decode function.

[andrewrk]

Forgot to add, with #287 this would be guaranteed to not memcpy.

[kristate]

It is used heavily as a wire format, so it's easy to create the TAI64N by simply grabbing it off the wire -- likewise for placing it back on the wire. The less CPU cycles the better.

[kristate]

Also, I don't know if it is a wise idea to use it platform internal. to reiterate, TAI64N is a wire encoding format (think databases and packet headers).

[andrewrk]

In general if you want to grab something off the wire and save cpu cycles, then you'll keep it encoded and never decode it. So you'll have a []u8 and we don't need to put it in a struct and give it a name. That's optimal and simpler.

The reason you would want to put it in a struct and give it a name is to do something with the decoded information. For example, from_unixtime(), now(), to_unixtime() all deal with the decoded information.

Equality comparison and ordering comparison can be done directly on the encoded bytes as you demonstrated, and as we do with utf8-encoded strings.

[andrewrk]

I'd like to see this used in a real life zig project before accepting it into the standard library.

My recommendation is to continue working on whatever project it was where you needed this, and include the implementation in your project. Once you get to a certain milestone where we can see your project in action, and we can see how this TAI64 API is used, we can determine whether and how to upstream it into the zig standard library.