Struct matrix_sdk_base::ruma::time::SystemTime

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

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 behaviour around a leap second is the same as the operating system’s wall clock. The precise behaviour 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.

Implementations

impl SystemTime

pub const UNIX_EPOCH: SystemTime = UNIX_EPOCH

An anchor in time which can be used to create new SystemTime instances or learn about where in time a SystemTime lies.

This constant is defined to be “1970-01-01 00:00:00 UTC” on all systems with respect to the system clock. Using duration_since on an existing SystemTime instance can tell how far away from this point in time a measurement lies, and using UNIX_EPOCH + duration can be used to create a SystemTime instance to represent another fixed point in time.

duration_since(UNIX_EPOCH).unwrap().as_secs() returns the number of non-leap seconds since the start of 1970 UTC. This is a POSIX time_t (as a u64), and is the same time representation as used in many Internet protocols.

Examples

use std::time::SystemTime;

match SystemTime::now().duration_since(SystemTime::UNIX_EPOCH) {
    Ok(n) => println!("1970-01-01 00:00:00 UTC was {} seconds ago!", n.as_secs()),
    Err(_) => panic!("SystemTime before UNIX EPOCH!"),
}

pub fn now() -> SystemTime

Returns the system time corresponding to “now”.

Examples

use std::time::SystemTime;

let sys_time = SystemTime::now();

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

Returns the amount of time elapsed from an earlier point in time.

This function may fail because measurements taken earlier are not guaranteed to always be before later measurements (due to anomalies such as the system clock being adjusted either forwards or backwards). Instant can be used to measure elapsed time without this risk of failure.

If successful, Ok(Duration) is returned where the duration represents the amount of time elapsed from the specified measurement to this one.

Returns an Err if earlier is later than self, and the error contains how far from self the time is.

Examples

use std::time::SystemTime;

let sys_time = SystemTime::now();
let new_sys_time = SystemTime::now();
let difference = new_sys_time.duration_since(sys_time)
    .expect("Clock may have gone backwards");
println!("{difference:?}");

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

Returns the difference from this system time to the current clock time.

This function may fail as the underlying system clock is susceptible to drift and updates (e.g., the system clock could go backwards), so this function might not always succeed. If successful, Ok(Duration) is returned where the duration represents the amount of time elapsed from this time measurement to the current time.

To measure elapsed time reliably, use Instant instead.

Returns an Err if self is later than the current system time, and the error contains how far from the current system time self is.

Examples

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

let sys_time = SystemTime::now();
let one_sec = Duration::from_secs(1);
sleep(one_sec);
assert!(sys_time.elapsed().unwrap() >= one_sec);

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

Returns Some(t) where t is the time self + duration if t can be represented as SystemTime (which means it’s inside the bounds of the underlying data structure), None otherwise.

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

Returns Some(t) where t is the time self - duration if t can be represented as SystemTime (which means it’s inside the bounds of the underlying data structure), None otherwise.

Trait Implementations

impl Add<Duration> for SystemTime

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

Panics

This function may panic if the resulting point in time cannot be represented by the underlying data structure. See SystemTime::checked_add for a version without panic.

type Output = SystemTime

The resulting type after applying the + operator.

impl Add<Duration> for SystemTime

Available on crate feature std only.

type Output = SystemTime

The resulting type after applying the + operator.

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

Performs the + operation.

impl AddAssign<Duration> for SystemTime

fn add_assign(&mut self, other: Duration)

Performs the += operation.

impl AddAssign<Duration> for SystemTime

Available on crate feature std only.

fn add_assign(&mut self, rhs: Duration)

Performs the += operation.

impl Clone for SystemTime

fn clone(&self) -> SystemTime

Returns a copy of the value.

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

Performs copy-assignment from source.

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>

Formats the value using the given formatter.

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

Available on crate feature std only.

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

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<UT> FfiConverter<UT> for SystemTime

Support for passing timestamp values via the FFI.

Timestamps values are currently always passed by serializing to a buffer.

Timestamps are represented on the buffer by an i64 that indicates the direction and the magnitude in seconds of the offset from epoch, and a u32 that indicates the nanosecond portion of the offset magnitude. The nanosecond portion is expected to be between 0 and 999,999,999.

To build an epoch offset the absolute value of the seconds portion of the offset should be combined with the nanosecond portion. This is because the sign of the seconds portion represents the direction of the offset overall. The sign of the seconds portion can then be used to determine if the total offset should be added to or subtracted from the unix epoch.

type FfiType = RustBuffer

The low-level type used for passing values of this type over the FFI.

fn lower(v: SystemTime) -> RustBuffer

Lower a rust value of the target type, into an FFI value of type Self::FfiType.

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

Lift a rust value of the target type, from an FFI value of type Self::FfiType.

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

Write a rust value into a buffer, to send over the FFI in serialized form.

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

Read a rust value from a buffer, received over the FFI in serialized form.

const TYPE_ID_META: MetadataBuffer = _

Type ID metadata, serialized into a MetadataBuffer.

impl From<OffsetDateTime> for SystemTime

Available on crate feature std only.

fn from(datetime: OffsetDateTime) -> SystemTime

Converts to this type from the input type.

impl From<SystemTime> for OffsetDateTime

Available on crate feature std only.

fn from(system_time: SystemTime) -> OffsetDateTime

Converts to this type from the input type.

impl Hash for SystemTime

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

where __H: Hasher,

Feeds this value into the given Hasher.

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

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<UT> Lift<UT> for SystemTime

type FfiType = <SystemTime as FfiConverter<UT>>::FfiType

fn try_lift(v: <SystemTime as Lift<UT>>::FfiType) -> Result<SystemTime, Error>

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

const TYPE_ID_META: MetadataBuffer = _

fn try_lift_from_rust_buffer(v: RustBuffer) -> Result<Self, Error>

Convenience method

impl<UT> LiftRef<UT> for SystemTime

type LiftType = SystemTime

impl<UT> LiftReturn<UT> for SystemTime

type ReturnType = <SystemTime as Lift<UT>>::FfiType

FFI return type for trait interfaces

fn try_lift_successful_return( v: <SystemTime as LiftReturn<UT>>::ReturnType ) -> Result<SystemTime, Error>

Lift a successfully returned value from a trait interface

const TYPE_ID_META: MetadataBuffer = _

fn lift_foreign_return( ffi_return: Self::ReturnType, call_status: RustCallStatus ) -> Self

Lift a foreign returned value from a trait interface

fn lift_error(_buf: RustBuffer) -> Self

Lift a Rust value for a callback interface method error result

fn handle_callback_unexpected_error(e: UnexpectedUniFFICallbackError) -> Self

Lift a Rust value for an unexpected callback interface error

impl<UT> Lower<UT> for SystemTime

type FfiType = <SystemTime as FfiConverter<UT>>::FfiType

fn lower(obj: SystemTime) -> <SystemTime as Lower<UT>>::FfiType

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

const TYPE_ID_META: MetadataBuffer = _

fn lower_into_rust_buffer(obj: Self) -> RustBuffer

Convenience method

impl<UT> LowerReturn<UT> for SystemTime

type ReturnType = <SystemTime as Lower<UT>>::FfiType

The type that should be returned by scaffolding functions for this type.

fn lower_return( obj: SystemTime ) -> Result<<SystemTime as LowerReturn<UT>>::ReturnType, RustBuffer>

Lower this value for scaffolding function return

const TYPE_ID_META: MetadataBuffer = _

fn handle_failed_lift(arg_name: &str, e: Error) -> Self

If possible, get a serialized error for failed argument lifts

impl Ord for SystemTime

fn cmp(&self, other: &SystemTime) -> Ordering

This method returns an Ordering between self and other.

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

where Self: Sized,

Compares and returns the maximum of two values.

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

where Self: Sized,

Compares and returns the minimum of two values.

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

where Self: Sized + PartialOrd,

Restrict a value to a certain interval.

impl PartialEq<OffsetDateTime> for SystemTime

Available on crate feature std only.

fn eq(&self, rhs: &OffsetDateTime) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialEq for SystemTime

fn eq(&self, other: &SystemTime) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd<OffsetDateTime> for SystemTime

Available on crate feature std only.

fn partial_cmp(&self, other: &OffsetDateTime) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl PartialOrd for SystemTime

fn partial_cmp(&self, other: &SystemTime) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Serialize for SystemTime

Available on crate feature std only.

fn serialize<S>( &self, serializer: S ) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl Sub<Duration> for SystemTime

type Output = SystemTime

The resulting type after applying the - operator.

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

Performs the - operation.

impl Sub<Duration> for SystemTime

Available on crate feature std only.

type Output = SystemTime

The resulting type after applying the - operator.

fn sub(self, duration: Duration) -> <SystemTime as Sub<Duration>>::Output

Performs the - operation.

impl Sub<OffsetDateTime> for SystemTime

Available on crate feature std only.

fn sub(self, rhs: OffsetDateTime) -> <SystemTime as Sub<OffsetDateTime>>::Output

Panics

This may panic if an overflow occurs.

type Output = Duration

The resulting type after applying the - operator.

impl SubAssign<Duration> for SystemTime

fn sub_assign(&mut self, other: Duration)

Performs the -= operation.

impl SubAssign<Duration> for SystemTime

Available on crate feature std only.

fn sub_assign(&mut self, rhs: Duration)

Performs the -= operation.

impl Copy for SystemTime

impl Eq for SystemTime

impl StructuralPartialEq for SystemTime