Struct Clock

pub struct Clock { /* private fields */ }

Unified clock for taking measurements.

Implementations

impl Clock

pub fn new() -> Clock

Creates a new clock with the optimal reference and source clocks.

Support for TSC, etc, are checked at the time of creation, not compile-time.

pub fn mock() -> (Clock, Arc<Mock>)

Creates a new clock that is mocked for controlling the underlying time.

Returns a Clock instance and a handle to the underlying Mock source so that the caller can control the passage of time.

pub fn now(&self) -> Instant

Gets the current time, scaled to reference time.

This method is the spiritual equivalent of std::time::Instant::now. It is guaranteed to return a monotonically increasing value between calls to the same Clock instance.

Returns an Instant.

pub fn raw(&self) -> u64

Gets the underlying time from the fastest available clock source.

As the clock source may or may not be the TSC, value is not guaranteed to be in nanoseconds or to be monotonic. Value can be scaled to reference time by calling either scaled or delta.

pub fn scaled(&self, value: u64) -> Instant

Scales a raw measurement to reference time.

You must scale raw measurements to ensure your result is in nanoseconds. The raw measurement is not guaranteed to be in nanoseconds and may vary. It is only OK to avoid scaling raw measurements if you don’t need actual nanoseconds.

Returns an Instant.

pub fn delta_as_nanos(&self, start: u64, end: u64) -> u64

Calculates the delta, in nanoseconds, between two raw measurements.

This method is very similar to delta but reduces overhead for high-frequency measurements that work with nanosecond counts internally, as it avoids the conversion of the delta into Duration.

pub fn delta(&self, start: u64, end: u64) -> Duration

Calculates the delta between two raw measurements.

This method is slightly faster when you know you need the delta between two raw measurements, or a start/end measurement, than using scaled for both conversions.

In code that simply needs access to the whole number of nanoseconds between the two measurements, consider Clock::delta_as_nanos instead, which is slightly faster than having to call both this method and Duration::as_nanos.

pub fn recent(&self) -> 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 upkeep thread must be started in order to update the time. You can read the documentation for Upkeep for more information on starting the upkeep thread, as well as the details of the “current time” mechanism.

If the upkeep thread has not been started, the return value will be 0.

Returns an Instant.

Trait Implementations

impl Clone for Clock

fn clone(&self) -> Clock

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Clock

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

Formats the value using the given formatter.

impl Default for Clock

fn default() -> Clock

Returns the “default value” for a type.