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NaiveDateTime::from_timestamp_millis(_opt) #818

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merged 5 commits into from Sep 19, 2022
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Pscheidl
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@Pscheidl Pscheidl commented Sep 11, 2022

Construct NaiveDateTime from millis since epoch.

Addresses #430.

@djc
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djc commented Sep 11, 2022

Despite the consistency argument I'm inclined to ditch the _opt() suffix from the fallible method and leave potential unwrapping to the caller (that is -- not add the panicking variant at all). This seems clearly better to me and the way of the future. @esheppa thoughts?

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Despite the consistency argument I'm inclined to ditch the _opt() suffix from the fallible method and leave potential unwrapping to the caller (that is -- not add the panicking variant at all). This seems clearly better to me and the way of the future. @esheppa thoughts?

Done (we can always revert to the original).

Construct NaiveDateTime from millis since epoch
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Thanks for working on this! LGTM modulo some documentation nits.

/// from the number of milliseconds
/// since the midnight UTC on January 1, 1970 (aka "UNIX timestamp").
///
/// Returns `None` on the out-of-range number of milliseconds and/or invalid nanosecond.
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In this case, there's no "invalid nanosecond", right? Also I think "the" -> "an" would read better?

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No, there are no invalid nanos in this case. Changed.

@@ -127,6 +127,28 @@ impl NaiveDateTime {
datetime.expect("invalid or out-of-range datetime")
}

/// Makes a new `NaiveDateTime` corresponding to a UTC date and time,
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You probably copy-pasted this from one of the other methods, but we're trying to make the first line of docstrings self-contained sentence fragments. After that we should have an empty line, then a more detailed description. Would you mind tweaking the docs for this new method at least?

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I think the whole doc can be simplified. Gave it a try. Please have a look.

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Seems like an improvement, some remaining nits.

///
/// Returns `None` on the out-of-range number of milliseconds and/or invalid nanosecond.
/// Returns `None` on an out-of-range number of milliseconds.
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Should ditch the prefix space here.

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done

/// Makes a new `NaiveDateTime` corresponding to a UTC date and time,
/// from the number of milliseconds
/// since the midnight UTC on January 1, 1970 (aka "UNIX timestamp").
/// Creates a new [NaiveDateTime] from milliseconds since UNIX Epoch.
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Both here and in the next line, I think prefixing "UNIX" with "the" ("the UNIX epoch") would read better.

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Sure, done,

@djc djc requested a review from esheppa September 13, 2022 09:47
#[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.

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esheppa commented Sep 13, 2022

Thanks for the PR @Pscheidl - this will be a useful helper function to have, and the docs look good - just noted a possible issue in the implementation when the input timestamp is negative

src/naive/datetime/mod.rs Outdated Show resolved Hide resolved
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All comments addressed.


if millis < 0 {
let nsecs = (millis % 1000).abs() as u32 * NANOS_IN_MILLISECOND;
NaiveDateTime::from_timestamp_opt(secs - 1, NANOS_IN_SECOND - nsecs)
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Thanks for the impl that handles negative millis. If possible could you subtract with checked_sub here to avoid potential overflow

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Done

let secs = millis / 1000;

if millis < 0 {
let nsecs = (millis % 1000).abs() as u32 * NANOS_IN_MILLISECOND;
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Do you mind switching as for u32::try_from(expr).ok()?

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Done

let nsecs = (millis % 1000).abs() as u32 * NANOS_IN_MILLISECOND;
NaiveDateTime::from_timestamp_opt(secs - 1, NANOS_IN_SECOND - nsecs)
} else {
let nsecs = (millis % 1000) as u32 * NANOS_IN_MILLISECOND;
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Do you mind switching as for u32::try_from(expr).ok()?

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Done

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esheppa commented Sep 18, 2022

Thanks @Pscheidl, the new negative millis handling looks good- I've just requested a few more small changes

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Awesome @esheppa , thank you. All comments addressed.

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Thanks for those changes @Pscheidl

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Learned a lot about the crate, thank you for the guidance.

I can't hit the merge button, as I don't have write access.

@djc djc merged commit 40800ce into chronotope:main Sep 19, 2022
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djc commented Sep 19, 2022

Oops, should have squashed this instead of rebasing. :(

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djc commented Sep 19, 2022

Backport to 0.4.x is in #823, which also includes some deduplication of the logic.

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3 participants