Unix timestamp in nanoseconds

help
1

Hello.
I need functions for conversion:

  1. the UNIX timestamp (in nanoseconds) to NaiveDateTime
    and
  2. NaiveDateTime to the UNIX timestamp (in nanoseconds);

I wrote this

use chrono::Utc;
use chrono::NaiveDateTime;

fn get_unix_nanos(secs: u64, ns: u32) -> u64 
{
    let dt = NaiveDateTime::from_timestamp(secs as i64, ns);
    let dt_nanos : i64 = dt.timestamp_nanos();
    dt_nanos as u64
}

fn get_naive_date_time(unix_ns: u64) -> NaiveDateTime 
{
    let secs = unix_ns / 1_000_000_000;
    let ns = unix_ns - (secs * 1_000_000_000);

    let dt = NaiveDateTime::from_timestamp(secs as i64, ns as u32);
    dt
}

Please check my code and write your suggestions.

2

What is NaiveDateTime?

3
4

Well, I guess it works!

5

(Background: reasonably experienced at programming in general but not a Rust expert, so anything I recommend you may have perfectly good reasons for not doing.)

  • You don't solve problem 2 - there's nothing here that takes a NaiveDateTime as input. Presumably the answer would be just to use .timestamp_nanos() as u64.

  • Chrono::Utc isn't used.

  • I would be inclined as a general stylistic point to replace this

let ns = unix_ns - (secs * 1_000_000_000);

with

let ns = unix_ns % 1_000_000_000;

  • I also wonder why you go to the trouble of allocating a temporary variable when you can just end this second function with

NaiveDateTime::from_timestamp(secs as i64, ns as u32)

  • You could go further and dump the other temporary variables too:
fn get_naive_date_time(unix_ns: u64) -> NaiveDateTime {
    NaiveDateTime::from_timestamp(
        (unix_ns / 1_000_000_000) as i64,
        (unix_ns % 1_000_000_000) as u32,
    )
}
  • Similarly the first function could become
fn get_unix_nanos(secs: u64, ns: u32) -> u64 {
    NaiveDateTime::from_timestamp(secs as i64, ns).timestamp_nanos() as u64
}

I'm not saying that these are better than your way of doing things but they're a way I suspect I'd find easier to understand when I was coming back to look at the code six months later.

On that head, I'd probably call the functions something like "sns_to_unixnanos" and "unixnanos_to_naivedatetime", i.e. naming their inputs as well as their outputs.

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6

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