Source code
Revision control
Copy as Markdown
Other Tools
// This is a part of Chrono.
// See README.md and LICENSE.txt for details.
use core::cmp::Ordering;
use core::fmt;
use core::marker::Sized;
use core::ops::{Add, Sub};
use datetime::DateTime;
use oldtime::Duration;
#[cfg(any(feature = "std", test))]
use std;
use TimeZone;
use Timelike;
/// Extension trait for subsecond rounding or truncation to a maximum number
/// of digits. Rounding can be used to decrease the error variance when
/// serializing/persisting to lower precision. Truncation is the default
/// behavior in Chrono display formatting. Either can be used to guarantee
/// equality (e.g. for testing) when round-tripping through a lower precision
/// format.
pub trait SubsecRound {
/// Return a copy rounded to the specified number of subsecond digits. With
/// 9 or more digits, self is returned unmodified. Halfway values are
/// rounded up (away from zero).
///
/// # Example
/// ``` rust
/// # use chrono::{DateTime, SubsecRound, Timelike, TimeZone, Utc};
/// let dt = Utc.ymd(2018, 1, 11).and_hms_milli(12, 0, 0, 154);
/// assert_eq!(dt.round_subsecs(2).nanosecond(), 150_000_000);
/// assert_eq!(dt.round_subsecs(1).nanosecond(), 200_000_000);
/// ```
fn round_subsecs(self, digits: u16) -> Self;
/// Return a copy truncated to the specified number of subsecond
/// digits. With 9 or more digits, self is returned unmodified.
///
/// # Example
/// ``` rust
/// # use chrono::{DateTime, SubsecRound, Timelike, TimeZone, Utc};
/// let dt = Utc.ymd(2018, 1, 11).and_hms_milli(12, 0, 0, 154);
/// assert_eq!(dt.trunc_subsecs(2).nanosecond(), 150_000_000);
/// assert_eq!(dt.trunc_subsecs(1).nanosecond(), 100_000_000);
/// ```
fn trunc_subsecs(self, digits: u16) -> Self;
}
impl<T> SubsecRound for T
where
T: Timelike + Add<Duration, Output = T> + Sub<Duration, Output = T>,
{
fn round_subsecs(self, digits: u16) -> T {
let span = span_for_digits(digits);
let delta_down = self.nanosecond() % span;
if delta_down > 0 {
let delta_up = span - delta_down;
if delta_up <= delta_down {
self + Duration::nanoseconds(delta_up.into())
} else {
self - Duration::nanoseconds(delta_down.into())
}
} else {
self // unchanged
}
}
fn trunc_subsecs(self, digits: u16) -> T {
let span = span_for_digits(digits);
let delta_down = self.nanosecond() % span;
if delta_down > 0 {
self - Duration::nanoseconds(delta_down.into())
} else {
self // unchanged
}
}
}
// Return the maximum span in nanoseconds for the target number of digits.
fn span_for_digits(digits: u16) -> u32 {
// fast lookup form of: 10^(9-min(9,digits))
match digits {
0 => 1_000_000_000,
1 => 100_000_000,
2 => 10_000_000,
3 => 1_000_000,
4 => 100_000,
5 => 10_000,
6 => 1_000,
7 => 100,
8 => 10,
_ => 1,
}
}
/// Extension trait for rounding or truncating a DateTime by a Duration.
///
/// # Limitations
/// Both rounding and truncating are done via [`Duration::num_nanoseconds`] and
/// [`DateTime::timestamp_nanos`]. This means that they will fail if either the
/// `Duration` or the `DateTime` are too big to represented as nanoseconds. They
/// will also fail if the `Duration` is bigger than the timestamp.
pub trait DurationRound: Sized {
/// Error that can occur in rounding or truncating
#[cfg(any(feature = "std", test))]
type Err: std::error::Error;
/// Error that can occur in rounding or truncating
#[cfg(not(any(feature = "std", test)))]
type Err: fmt::Debug + fmt::Display;
/// Return a copy rounded by Duration.
///
/// # Example
/// ``` rust
/// # use chrono::{DateTime, DurationRound, Duration, TimeZone, Utc};
/// let dt = Utc.ymd(2018, 1, 11).and_hms_milli(12, 0, 0, 154);
/// assert_eq!(
/// dt.duration_round(Duration::milliseconds(10)).unwrap().to_string(),
/// "2018-01-11 12:00:00.150 UTC"
/// );
/// assert_eq!(
/// dt.duration_round(Duration::days(1)).unwrap().to_string(),
/// "2018-01-12 00:00:00 UTC"
/// );
/// ```
fn duration_round(self, duration: Duration) -> Result<Self, Self::Err>;
/// Return a copy truncated by Duration.
///
/// # Example
/// ``` rust
/// # use chrono::{DateTime, DurationRound, Duration, TimeZone, Utc};
/// let dt = Utc.ymd(2018, 1, 11).and_hms_milli(12, 0, 0, 154);
/// assert_eq!(
/// dt.duration_trunc(Duration::milliseconds(10)).unwrap().to_string(),
/// "2018-01-11 12:00:00.150 UTC"
/// );
/// assert_eq!(
/// dt.duration_trunc(Duration::days(1)).unwrap().to_string(),
/// "2018-01-11 00:00:00 UTC"
/// );
/// ```
fn duration_trunc(self, duration: Duration) -> Result<Self, Self::Err>;
}
/// The maximum number of seconds a DateTime can be to be represented as nanoseconds
const MAX_SECONDS_TIMESTAMP_FOR_NANOS: i64 = 9_223_372_036;
impl<Tz: TimeZone> DurationRound for DateTime<Tz> {
type Err = RoundingError;
fn duration_round(self, duration: Duration) -> Result<Self, Self::Err> {
if let Some(span) = duration.num_nanoseconds() {
if self.timestamp().abs() > MAX_SECONDS_TIMESTAMP_FOR_NANOS {
return Err(RoundingError::TimestampExceedsLimit);
}
let stamp = self.timestamp_nanos();
if span > stamp.abs() {
return Err(RoundingError::DurationExceedsTimestamp);
}
let delta_down = stamp % span;
if delta_down == 0 {
Ok(self)
} else {
let (delta_up, delta_down) = if delta_down < 0 {
(delta_down.abs(), span - delta_down.abs())
} else {
(span - delta_down, delta_down)
};
if delta_up <= delta_down {
Ok(self + Duration::nanoseconds(delta_up))
} else {
Ok(self - Duration::nanoseconds(delta_down))
}
}
} else {
Err(RoundingError::DurationExceedsLimit)
}
}
fn duration_trunc(self, duration: Duration) -> Result<Self, Self::Err> {
if let Some(span) = duration.num_nanoseconds() {
if self.timestamp().abs() > MAX_SECONDS_TIMESTAMP_FOR_NANOS {
return Err(RoundingError::TimestampExceedsLimit);
}
let stamp = self.timestamp_nanos();
if span > stamp.abs() {
return Err(RoundingError::DurationExceedsTimestamp);
}
let delta_down = stamp % span;
match delta_down.cmp(&0) {
Ordering::Equal => Ok(self),
Ordering::Greater => Ok(self - Duration::nanoseconds(delta_down)),
Ordering::Less => Ok(self - Duration::nanoseconds(span - delta_down.abs())),
}
} else {
Err(RoundingError::DurationExceedsLimit)
}
}
}
/// An error from rounding by `Duration`
///
/// See: [`DurationRound`]
#[derive(Debug, Clone, PartialEq, Eq, Copy)]
pub enum RoundingError {
/// Error when the Duration exceeds the Duration from or until the Unix epoch.
///
/// ``` rust
/// # use chrono::{DateTime, DurationRound, Duration, RoundingError, TimeZone, Utc};
/// let dt = Utc.ymd(1970, 12, 12).and_hms(0, 0, 0);
///
/// assert_eq!(
/// dt.duration_round(Duration::days(365)),
/// Err(RoundingError::DurationExceedsTimestamp),
/// );
/// ```
DurationExceedsTimestamp,
/// Error when `Duration.num_nanoseconds` exceeds the limit.
///
/// ``` rust
/// # use chrono::{DateTime, DurationRound, Duration, RoundingError, TimeZone, Utc};
/// let dt = Utc.ymd(2260, 12, 31).and_hms_nano(23, 59, 59, 1_75_500_000);
///
/// assert_eq!(
/// dt.duration_round(Duration::days(300 * 365)),
/// Err(RoundingError::DurationExceedsLimit)
/// );
/// ```
DurationExceedsLimit,
/// Error when `DateTime.timestamp_nanos` exceeds the limit.
///
/// ``` rust
/// # use chrono::{DateTime, DurationRound, Duration, RoundingError, TimeZone, Utc};
/// let dt = Utc.ymd(2300, 12, 12).and_hms(0, 0, 0);
///
/// assert_eq!(dt.duration_round(Duration::days(1)), Err(RoundingError::TimestampExceedsLimit),);
/// ```
TimestampExceedsLimit,
}
impl fmt::Display for RoundingError {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match *self {
RoundingError::DurationExceedsTimestamp => {
write!(f, "duration in nanoseconds exceeds timestamp")
}
RoundingError::DurationExceedsLimit => {
write!(f, "duration exceeds num_nanoseconds limit")
}
RoundingError::TimestampExceedsLimit => {
write!(f, "timestamp exceeds num_nanoseconds limit")
}
}
}
}
#[cfg(any(feature = "std", test))]
impl std::error::Error for RoundingError {
#[allow(deprecated)]
fn description(&self) -> &str {
"error from rounding or truncating with DurationRound"
}
}
#[cfg(test)]
mod tests {
use super::{Duration, DurationRound, SubsecRound};
use offset::{FixedOffset, TimeZone, Utc};
use Timelike;
#[test]
fn test_round_subsecs() {
let pst = FixedOffset::east(8 * 60 * 60);
let dt = pst.ymd(2018, 1, 11).and_hms_nano(10, 5, 13, 084_660_684);
assert_eq!(dt.round_subsecs(10), dt);
assert_eq!(dt.round_subsecs(9), dt);
assert_eq!(dt.round_subsecs(8).nanosecond(), 084_660_680);
assert_eq!(dt.round_subsecs(7).nanosecond(), 084_660_700);
assert_eq!(dt.round_subsecs(6).nanosecond(), 084_661_000);
assert_eq!(dt.round_subsecs(5).nanosecond(), 084_660_000);
assert_eq!(dt.round_subsecs(4).nanosecond(), 084_700_000);
assert_eq!(dt.round_subsecs(3).nanosecond(), 085_000_000);
assert_eq!(dt.round_subsecs(2).nanosecond(), 080_000_000);
assert_eq!(dt.round_subsecs(1).nanosecond(), 100_000_000);
assert_eq!(dt.round_subsecs(0).nanosecond(), 0);
assert_eq!(dt.round_subsecs(0).second(), 13);
let dt = Utc.ymd(2018, 1, 11).and_hms_nano(10, 5, 27, 750_500_000);
assert_eq!(dt.round_subsecs(9), dt);
assert_eq!(dt.round_subsecs(4), dt);
assert_eq!(dt.round_subsecs(3).nanosecond(), 751_000_000);
assert_eq!(dt.round_subsecs(2).nanosecond(), 750_000_000);
assert_eq!(dt.round_subsecs(1).nanosecond(), 800_000_000);
assert_eq!(dt.round_subsecs(0).nanosecond(), 0);
assert_eq!(dt.round_subsecs(0).second(), 28);
}
#[test]
fn test_round_leap_nanos() {
let dt = Utc.ymd(2016, 12, 31).and_hms_nano(23, 59, 59, 1_750_500_000);
assert_eq!(dt.round_subsecs(9), dt);
assert_eq!(dt.round_subsecs(4), dt);
assert_eq!(dt.round_subsecs(2).nanosecond(), 1_750_000_000);
assert_eq!(dt.round_subsecs(1).nanosecond(), 1_800_000_000);
assert_eq!(dt.round_subsecs(1).second(), 59);
assert_eq!(dt.round_subsecs(0).nanosecond(), 0);
assert_eq!(dt.round_subsecs(0).second(), 0);
}
#[test]
fn test_trunc_subsecs() {
let pst = FixedOffset::east(8 * 60 * 60);
let dt = pst.ymd(2018, 1, 11).and_hms_nano(10, 5, 13, 084_660_684);
assert_eq!(dt.trunc_subsecs(10), dt);
assert_eq!(dt.trunc_subsecs(9), dt);
assert_eq!(dt.trunc_subsecs(8).nanosecond(), 084_660_680);
assert_eq!(dt.trunc_subsecs(7).nanosecond(), 084_660_600);
assert_eq!(dt.trunc_subsecs(6).nanosecond(), 084_660_000);
assert_eq!(dt.trunc_subsecs(5).nanosecond(), 084_660_000);
assert_eq!(dt.trunc_subsecs(4).nanosecond(), 084_600_000);
assert_eq!(dt.trunc_subsecs(3).nanosecond(), 084_000_000);
assert_eq!(dt.trunc_subsecs(2).nanosecond(), 080_000_000);
assert_eq!(dt.trunc_subsecs(1).nanosecond(), 0);
assert_eq!(dt.trunc_subsecs(0).nanosecond(), 0);
assert_eq!(dt.trunc_subsecs(0).second(), 13);
let dt = pst.ymd(2018, 1, 11).and_hms_nano(10, 5, 27, 750_500_000);
assert_eq!(dt.trunc_subsecs(9), dt);
assert_eq!(dt.trunc_subsecs(4), dt);
assert_eq!(dt.trunc_subsecs(3).nanosecond(), 750_000_000);
assert_eq!(dt.trunc_subsecs(2).nanosecond(), 750_000_000);
assert_eq!(dt.trunc_subsecs(1).nanosecond(), 700_000_000);
assert_eq!(dt.trunc_subsecs(0).nanosecond(), 0);
assert_eq!(dt.trunc_subsecs(0).second(), 27);
}
#[test]
fn test_trunc_leap_nanos() {
let dt = Utc.ymd(2016, 12, 31).and_hms_nano(23, 59, 59, 1_750_500_000);
assert_eq!(dt.trunc_subsecs(9), dt);
assert_eq!(dt.trunc_subsecs(4), dt);
assert_eq!(dt.trunc_subsecs(2).nanosecond(), 1_750_000_000);
assert_eq!(dt.trunc_subsecs(1).nanosecond(), 1_700_000_000);
assert_eq!(dt.trunc_subsecs(1).second(), 59);
assert_eq!(dt.trunc_subsecs(0).nanosecond(), 1_000_000_000);
assert_eq!(dt.trunc_subsecs(0).second(), 59);
}
#[test]
fn test_duration_round() {
let dt = Utc.ymd(2016, 12, 31).and_hms_nano(23, 59, 59, 175_500_000);
assert_eq!(
dt.duration_round(Duration::milliseconds(10)).unwrap().to_string(),
"2016-12-31 23:59:59.180 UTC"
);
// round up
let dt = Utc.ymd(2012, 12, 12).and_hms_milli(18, 22, 30, 0);
assert_eq!(
dt.duration_round(Duration::minutes(5)).unwrap().to_string(),
"2012-12-12 18:25:00 UTC"
);
// round down
let dt = Utc.ymd(2012, 12, 12).and_hms_milli(18, 22, 29, 999);
assert_eq!(
dt.duration_round(Duration::minutes(5)).unwrap().to_string(),
"2012-12-12 18:20:00 UTC"
);
assert_eq!(
dt.duration_round(Duration::minutes(10)).unwrap().to_string(),
"2012-12-12 18:20:00 UTC"
);
assert_eq!(
dt.duration_round(Duration::minutes(30)).unwrap().to_string(),
"2012-12-12 18:30:00 UTC"
);
assert_eq!(
dt.duration_round(Duration::hours(1)).unwrap().to_string(),
"2012-12-12 18:00:00 UTC"
);
assert_eq!(
dt.duration_round(Duration::days(1)).unwrap().to_string(),
"2012-12-13 00:00:00 UTC"
);
}
#[test]
fn test_duration_round_pre_epoch() {
let dt = Utc.ymd(1969, 12, 12).and_hms(12, 12, 12);
assert_eq!(
dt.duration_round(Duration::minutes(10)).unwrap().to_string(),
"1969-12-12 12:10:00 UTC"
);
}
#[test]
fn test_duration_trunc() {
let dt = Utc.ymd(2016, 12, 31).and_hms_nano(23, 59, 59, 1_75_500_000);
assert_eq!(
dt.duration_trunc(Duration::milliseconds(10)).unwrap().to_string(),
"2016-12-31 23:59:59.170 UTC"
);
// would round up
let dt = Utc.ymd(2012, 12, 12).and_hms_milli(18, 22, 30, 0);
assert_eq!(
dt.duration_trunc(Duration::minutes(5)).unwrap().to_string(),
"2012-12-12 18:20:00 UTC"
);
// would round down
let dt = Utc.ymd(2012, 12, 12).and_hms_milli(18, 22, 29, 999);
assert_eq!(
dt.duration_trunc(Duration::minutes(5)).unwrap().to_string(),
"2012-12-12 18:20:00 UTC"
);
assert_eq!(
dt.duration_trunc(Duration::minutes(10)).unwrap().to_string(),
"2012-12-12 18:20:00 UTC"
);
assert_eq!(
dt.duration_trunc(Duration::minutes(30)).unwrap().to_string(),
"2012-12-12 18:00:00 UTC"
);
assert_eq!(
dt.duration_trunc(Duration::hours(1)).unwrap().to_string(),
"2012-12-12 18:00:00 UTC"
);
assert_eq!(
dt.duration_trunc(Duration::days(1)).unwrap().to_string(),
"2012-12-12 00:00:00 UTC"
);
}
#[test]
fn test_duration_trunc_pre_epoch() {
let dt = Utc.ymd(1969, 12, 12).and_hms(12, 12, 12);
assert_eq!(
dt.duration_trunc(Duration::minutes(10)).unwrap().to_string(),
"1969-12-12 12:10:00 UTC"
);
}
}