Struct SystemTime

1.8.0 · Source

pub struct SystemTime(/* private fields */);

Expand description

A measurement of the system clock, useful for talking to external entities like the file system or other processes.

Distinct from the Instant type, this time measurement is not monotonic. This means that you can save a file to the file system, then save another file to the file system, and the second file has a SystemTime measurement earlier than the first. In other words, an operation that happens after another operation in real time may have an earlier SystemTime!

Consequently, comparing two SystemTime instances to learn about the duration between them returns a Result instead of an infallible Duration to indicate that this sort of time drift may happen and needs to be handled.

Although a SystemTime cannot be directly inspected, the UNIX_EPOCH constant is provided in this module as an anchor in time to learn information about a SystemTime. By calculating the duration from this fixed point in time, a SystemTime can be converted to a human-readable time, or perhaps some other string representation.

The size of a SystemTime struct may vary depending on the target operating system.

A SystemTime does not count leap seconds. SystemTime::now()’s behavior around a leap second is the same as the operating system’s wall clock. The precise behavior near a leap second (e.g. whether the clock appears to run slow or fast, or stop, or jump) depends on platform and configuration, so should not be relied on.

Example:

use std::time::{Duration, SystemTime};
use std::thread::sleep;

fn main() {
   let now = SystemTime::now();

   // we sleep for 2 seconds
   sleep(Duration::new(2, 0));
   match now.elapsed() {
       Ok(elapsed) => {
           // it prints '2'
           println!("{}", elapsed.as_secs());
       }
       Err(e) => {
           // an error occurred!
           println!("Error: {e:?}");
       }
   }
}

§Platform-specific behavior

The precision of SystemTime can depend on the underlying OS-specific time format. For example, on Windows the time is represented in 100 nanosecond intervals whereas Linux can represent nanosecond intervals.

The following system calls are currently being used by now() to find out the current time:

Platform	System call
SGX	`insecure_time` usercall. More information on timekeeping in SGX
UNIX	clock_gettime (Realtime Clock)
Darwin	clock_gettime (Realtime Clock)
VXWorks	clock_gettime (Realtime Clock)
SOLID	`SOLID_RTC_ReadTime`
WASI	__wasi_clock_time_get (Realtime Clock)
Windows	GetSystemTimePreciseAsFileTime / GetSystemTimeAsFileTime

Disclaimer: These system calls might change over time.

Note: mathematical operations like add may panic if the underlying structure cannot represent the new point in time.

Struct SystemTimeCopy item path

§Platform-specific behavior

Implementations§

impl SystemTime

pub const UNIX_EPOCH: SystemTime = UNIX_EPOCH

§Examples

pub fn now() -> SystemTime

§Examples

pub fn duration_since( &self, earlier: SystemTime, ) -> Result<Duration, SystemTimeError>

§Examples

pub fn elapsed(&self) -> Result<Duration, SystemTimeError>

§Examples

pub fn checked_add(&self, duration: Duration) -> Option<SystemTime>

pub fn checked_sub(&self, duration: Duration) -> Option<SystemTime>

Trait Implementations§

impl Add<Duration> for SystemTime

fn add(self, dur: Duration) -> SystemTime

§Panics

type Output = SystemTime

impl Add<Duration> for SystemTime

type Output = SystemTime

fn add(self, duration: Duration) -> <SystemTime as Add<Duration>>::Output

impl AddAssign<Duration> for SystemTime

fn add_assign(&mut self, other: Duration)

impl AddAssign<Duration> for SystemTime

fn add_assign(&mut self, rhs: Duration)

impl Clone for SystemTime

fn clone(&self) -> SystemTime

fn clone_from(&mut self, source: &Self)

impl<UT> ConvertError<UT> for SystemTime

fn try_convert_unexpected_callback_error( e: UnexpectedUniFFICallbackError, ) -> Result<SystemTime, Error>

impl Debug for SystemTime

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

impl<'a> DecodeValue<'a> for SystemTime

fn decode_value<R>(reader: &mut R, header: Header) -> Result<SystemTime, Error>where R: Reader<'a>,

impl<'de> Deserialize<'de> for SystemTime

fn deserialize<D>( deserializer: D, ) -> Result<SystemTime, <D as Deserializer<'de>>::Error>where D: Deserializer<'de>,

impl EncodeValue for SystemTime

fn value_len(&self) -> Result<Length, Error>

fn encode_value(&self, writer: &mut impl Writer) -> Result<(), Error>

fn header(&self) -> Result<Header, Error>where Self: Tagged,

impl<UT> FfiConverter<UT> for SystemTime

const TYPE_ID_META: MetadataBuffer = _

type FfiType = RustBuffer

fn lower(v: SystemTime) -> RustBuffer

fn try_lift(buf: RustBuffer) -> Result<SystemTime, Error>

fn write(obj: SystemTime, buf: &mut Vec<u8>)

fn try_read(buf: &mut &[u8]) -> Result<SystemTime, Error>

impl FixedTag for SystemTime

const TAG: Tag = Tag::GeneralizedTime

impl From<&DateTime> for SystemTime

fn from(time: &DateTime) -> SystemTime

impl From<&GeneralizedTime> for SystemTime

fn from(time: &GeneralizedTime) -> SystemTime

impl From<Date> for SystemTime

fn from(date: Date) -> SystemTime

impl<Tz> From<DateTime<Tz>> for SystemTimewhere Tz: TimeZone,

fn from(dt: DateTime<Tz>) -> SystemTime

impl From<DateTime> for SystemTime

fn from(time: DateTime) -> SystemTime

impl From<Expires> for SystemTime

fn from(date: Expires) -> SystemTime

impl From<GeneralizedTime> for SystemTime

fn from(time: GeneralizedTime) -> SystemTime

impl From<HttpDate> for SystemTime

fn from(v: HttpDate) -> SystemTime

impl From<HttpDate> for SystemTime

fn from(date: HttpDate) -> SystemTime

impl From<IfModifiedSince> for SystemTime

fn from(date: IfModifiedSince) -> SystemTime

impl From<IfUnmodifiedSince> for SystemTime

fn from(date: IfUnmodifiedSince) -> SystemTime

impl From<LastModified> for SystemTime

fn from(date: LastModified) -> SystemTime

impl From<OffsetDateTime> for SystemTime

fn from(datetime: OffsetDateTime) -> SystemTime

impl From<SystemTime> for Date

fn from(time: SystemTime) -> Date

impl From<SystemTime> for DateTime<Local>

fn from(t: SystemTime) -> DateTime<Local>

Struct SystemTime

fn decode_value<R>(reader: &mut R, header: Header) -> Result<SystemTime, Error>
where R: Reader<'a>,

fn deserialize<D>( deserializer: D, ) -> Result<SystemTime, <D as Deserializer<'de>>::Error>
where D: Deserializer<'de>,

fn header(&self) -> Result<Header, Error>
where Self: Tagged,

impl<Tz> From<DateTime<Tz>> for SystemTime
where Tz: TimeZone,

fn hash<H>(&self, state: &mut H)
where __H: Hasher,

fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

fn max(self, other: Self) -> Self
where Self: Sized,

fn min(self, other: Self) -> Self
where Self: Sized,

fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized,