Struct quanta::Instant

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

A point-in-time wall-clock measurement.

Mimics most of the functionality of std::time::Instant but provides an additional method for using the “recent time” feature of quanta.

Monotonicity

On all platforms, Instant will try to use an OS API that guarantees monotonic behavior if available, which is the case for all supported platforms. In practice such guarantees are – under rare circumstances – broken by hardware, virtualization or operating system bugs. To work around these bugs and platforms not offering monotonic clocks duration_since, elapsed and sub saturate to zero. In older quanta versions this lead to a panic instead. checked_duration_since can be used to detect and handle situations where monotonicity is violated, or Instants are subtracted in the wrong order.

This workaround obscures programming errors where earlier and later instants are accidentally swapped. For this reason future quanta versions may reintroduce panics.

Implementations

impl Instant

pub fn now() -> Instant

Gets the current time, scaled to reference time.

This method depends on a lazily initialized global clock, which can take up to 200ms to initialize and calibrate itself.

This method is the spiritual equivalent of Instant::now. It is guaranteed to return a monotonically increasing value.

pub fn recent() -> Instant

Gets the most recent current time, scaled to reference time.

This method provides ultra-low-overhead access to a slightly-delayed version of the current time. Instead of querying the underlying source clock directly, a shared, global value is read directly without the need to scale to reference time.

The value is updated by running an “upkeep” thread or by calling set_recent. An upkeep thread can be configured and spawned via Upkeep.

If the upkeep thread has not been started, or no value has been set manually, a lazily initialized global clock will be used to get the current time. This clock can take up to 200ms to initialize and calibrate itself.

pub fn duration_since(&self, earlier: Instant) -> Duration

Returns the amount of time elapsed from another instant to this one.

Panics

Previous versions of this method panicked when earlier was later than self. Currently, this method saturates to zero. Future versions may reintroduce the panic in some circumstances. See Monotonicity.

Examples

use quanta::Clock;
use std::time::Duration;
use std::thread::sleep;

let mut clock = Clock::new();
let now = clock.now();
sleep(Duration::new(1, 0));
let new_now = clock.now();
println!("{:?}", new_now.duration_since(now));

pub fn checked_duration_since(&self, earlier: Instant) -> Option<Duration>

Returns the amount of time elapsed from another instant to this one, or None if that instant is earlier than this one.

Due to monotonicity bugs, even under correct logical ordering of the passed Instants, this method can return None.

Examples

use quanta::Clock;
use std::time::Duration;
use std::thread::sleep;

let mut clock = Clock::new();
let now = clock.now();
sleep(Duration::new(1, 0));
let new_now = clock.now();
println!("{:?}", new_now.checked_duration_since(now));
println!("{:?}", now.checked_duration_since(new_now)); // None

pub fn saturating_duration_since(&self, earlier: Instant) -> Duration

Returns the amount of time elapsed from another instant to this one, or zero duration if that instant is earlier than this one.

Due to monotonicity bugs, even under correct logical ordering of the passed Instants, this method can return None.

Examples

use quanta::Clock;
use std::time::Duration;
use std::thread::sleep;

let mut clock = Clock::new();
let now = clock.now();
sleep(Duration::new(1, 0));
let new_now = clock.now();
println!("{:?}", new_now.saturating_duration_since(now));
println!("{:?}", now.saturating_duration_since(new_now)); // 0ns

pub fn elapsed(&self) -> Duration

Returns the amount of time elapsed since this instant was created.

Panics

Previous quanta versions panicked when the current time was earlier than self. Currently this method returns a Duration of zero in that case. Future versions may reintroduce the panic. See Monotonicity.

Examples

use quanta::Clock;
use std::time::Duration;
use std::thread::sleep;

let mut clock = Clock::new();
let now = clock.now();
sleep(Duration::new(1, 0));
let elapsed = now.elapsed();
println!("{:?}", elapsed); // ≥ 1s

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

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

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

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

Trait Implementations

impl Add<Duration> for Instant

fn add(self, other: Duration) -> Instant

Panics

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

type Output = Instant

The resulting type after applying the + operator.

impl AddAssign<Duration> for Instant

fn add_assign(&mut self, other: Duration)

Performs the += operation.

impl Clone for Instant

fn clone(&self) -> Instant

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Instant

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

Formats the value using the given formatter.

impl Ord for Instant

fn cmp(&self, other: &Self) -> 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 for Instant

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

Tests for self and other values to be equal, and is used by ==.

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

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

impl PartialOrd for Instant

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

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

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

Tests less than (for self and other) and is used by the < operator.

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

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

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

Tests greater than (for self and other) and is used by the > operator.

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

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

impl Sub<Duration> for Instant

type Output = Instant

The resulting type after applying the - operator.

fn sub(self, other: Duration) -> Instant

Performs the - operation.

impl Sub for Instant

fn sub(self, other: Instant) -> Duration

Returns the amount of time elapsed from another instant to this one, or zero duration if that instant is later than this one.

Panics

Previous quanta versions panicked when other was later than self. Currently this method saturates. Future versions may reintroduce the panic in some circumstances. See Monotonicity.

type Output = Duration

The resulting type after applying the - operator.

impl SubAssign<Duration> for Instant

fn sub_assign(&mut self, other: Duration)

Performs the -= operation.

impl Copy for Instant

impl Eq for Instant

impl StructuralPartialEq for Instant