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NaiveDateTime::from_timestamp_millis(_opt) #818

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merged 5 commits into from Sep 19, 2022
Merged

NaiveDateTime::from_timestamp_millis(_opt) #818

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341ed5a
NaiveDateTime::from_timestamp_millis(_opt)
Pscheidl Sep 11, 2022
80885d8
docs: Simplify documentation for NaiveDateTime::from_timestamp_millis
Pscheidl Sep 12, 2022
63b26bb
docs: prefix UNIX with `the`, remove whitespaces
Pscheidl Sep 12, 2022
b175f9c
fix: Negative UNIX timestamps accepted by `from_timestamp_millis`
Pscheidl Sep 14, 2022
de12842
refactor: Use checked substitution & convert u32 conversiont to None …
Pscheidl Sep 18, 2022
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21 changes: 21 additions & 0 deletions src/naive/datetime/mod.rs
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Expand Up @@ -126,6 +126,27 @@ impl NaiveDateTime {
let datetime = NaiveDateTime::from_timestamp_opt(secs, nsecs);
datetime.expect("invalid or out-of-range datetime")
}
/// Creates a new [NaiveDateTime] from milliseconds since the UNIX Epoch.
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///
/// The UNIX epoch starts on midnight, January 1, 1970, UTC.
///
/// Returns `None` on an out-of-range number of milliseconds.
///
/// # Example
///
/// ```
/// use chrono::NaiveDateTime;
/// let timestamp_millis: i64 = 1662921288; //Sunday, September 11, 2022 6:34:48 PM
/// let naive_datetime = NaiveDateTime::from_timestamp_millis(timestamp_millis);
/// assert!(naive_datetime.is_some());
/// assert_eq!(timestamp_millis, naive_datetime.unwrap().timestamp_millis());
/// ```
#[inline]
pub fn from_timestamp_millis(millis: i64) -> Option<NaiveDateTime> {
let secs = millis / 1000;
let nsecs = (millis % 1000) as u32 * 1_000_000;
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this looks problematic as the input millis could be negative, and will still be negative after taking the modulo (playground)

One option would be to have two cases, depending on whether millis is positive or negative, similar to the logic used here

The other option is just:
NaiveDate::from_ymd(1970,1, 1).and_hms(0, 0, 0) + TimeDelta::from_millis(millis)

Also it would be preferable to use TryFrom instead of as

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Awesome, let's deal with that. I'm super busy ATM, please give me by the end of the week :)

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I don't think we should go through TimeDelta here, which adds a bunch of overhead and feels like a layering violation. Would be better to do a minimal calculation and still defer to NaiveDateTime::from_timestamp_opt().

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Good call RE. avoiding TimeDelta especially as from_millis may well get deprecated anyway

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Done. The nanos calculation is split, as when the timestamp in millis is negative, an additional abs() op is done.

NaiveDateTime::from_timestamp_opt(secs, nsecs)
}

/// Makes a new `NaiveDateTime` corresponding to a UTC date and time,
/// from the number of non-leap seconds
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