Struct Counter 

pub struct Counter { /* private fields */ }

Available on AArch64 or x86-64 only.

The CPU’s free-running counter: cntvct_el0 on aarch64, the time-stamp counter on x86_64.

A reading is one instruction that touches no memory. Every core and process on a machine reads the same counter, so a Tickstamp one process took, another may subtract from. Only the difference of two readings means anything, and the counter’s rate turns it into a span.

The read is not ordered against the instructions around it: right for stamping, and for timing anything much longer than the read itself.

Examples

use t2t_clock::{Clock, Counter};
use t2t_core::Timedelta;

let counter = Counter::discover()?;
let start = counter.now();
let took = (counter.now() - start).to_timedelta(counter.rate());

assert!(took < Timedelta::from_millis(1), "two reads back to back");

Implementations

impl Counter

pub fn discover() -> Result<Self, CounterError>

The counter, at the rate the CPU reports for it; where it reports none, on x86_64 with std on 64-bit Linux or macOS, one measured against the OS clocks over 10 ms.

Errors

• CounterError::NotInvariant, the time-stamp counter’s rate follows the core’s.
• CounterError::NoRate, the CPU reports no rate, and none could be measured.
• CounterError::ImplausibleRate, the rate is outside 1 MHz to 10 GHz.

pub const fn new(rate: TickRate) -> Self

The counter, at rate: one discovered elsewhere, or known.

pub const fn rate(self) -> TickRate

The counter’s rate.

Trait Implementations

impl Clock for Counter

type Reading = Tickstamp

What the clock reads.

fn now(&self) -> Tickstamp

The time now.

impl Clone for Counter

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Counter

impl Debug for Counter

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

Formats the value using the given formatter.

impl Eq for Counter

impl Hash for Counter

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

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 PartialEq for Counter

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

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for Counter