Enforce monotonicity in same millisecond about ulid-rs HOT 5 CLOSED

Hi! Thank you for your contribution. You're right that this isn't currently implemented; It wasn't in the spec when this project was created. This will likely be implemented with adding a Generator/Factory struct to the library that can store the state of the last ulid created.

Is this something you wanted to implement, or that you have an immediate need for?

from ulid-rs.

I don't have any real immediate need. I may try and put together a pull request for it. Unsure if I will have time. Do you have any other architecture suggestions besides having a generator that keeps track of the last ulid?

from ulid-rs.

The generator will likely use an algorithm similar to:

1. Create a new DateTime using the chrono library
2. Compare that with the last ulid's datetime to see if it's in the same millisecond (see Ulid::datetime())
3. If it's within the same millisecond call Ulid::increment() to get a monotonic ulid. (needs implementation, signature: fn increment(&self) -> Option<Ulid>)
   • If an overflow occurs, None will be returned
4. Otherwise use Ulid::from_datetime() to create a new Ulid

struct Generator {
    previous: Option<Ulid>;
}

impl Generator {
    fn new() -> Generator { ... }
    fn generate(&mut self) -> Result<Ulid, MontonicError> { ... }
}

enum MonotonicError {
    Overflow,
}

from ulid-rs.

I'll assign this to you for the next week. If you don't get around to it, it's no big deal.

from ulid-rs.

I found some time this afternoon, and it was easier to knock out than expected. of course if this is not the direction you were expecting then I can change it up.

If you do like it then I can work on putting documentation in the readme as part of the pull request as well.

from ulid-rs.