Struct AtomicTime

#[repr(C)]
pub struct AtomicTime {
    pub realtime: AtomicBool,
    pub timestamp_ns: AtomicU64,
}

Represents an atomic timekeeping structure.

AtomicTime can act as a real-time clock or static clock based on its mode. It uses AtomicU64 to atomically update the value using only immutable references.

This struct provides thread-safe access to a stored nanosecond time value, useful for when concurrent access to time information is required.

Fields

realtime: AtomicBool

Indicates whether the clock is operating in real-time mode. When false, the clock is in a manual or static mode, allowing for controlled time setting.

timestamp_ns: AtomicU64

The last recorded time for the clock in UNIX nanoseconds. This value is atomically updated and represents the precise time measurement.

Implementations

impl AtomicTime

pub fn new(realtime: bool, time: UnixNanos) -> Self

Creates a new AtomicTime instance.

The realtime flag will determine whether the atomic time is based off system time. The time will be set to the given UNIX time (nanoseconds).

pub fn get_time_ns(&self) -> UnixNanos

Get time in nanoseconds.

• Real-time mode returns current wall clock time since UNIX epoch (unique and monotonic).
• Static mode returns currently stored time.

pub fn get_time_us(&self) -> u64

Get time as microseconds.

pub fn get_time_ms(&self) -> u64

Get time as milliseconds.

pub fn get_time(&self) -> f64

Get time as seconds.

pub fn set_time(&self, time: UnixNanos)

Sets new time for the clock.

pub fn increment_time(&self, delta: u64) -> UnixNanos

Increments current time with a delta and returns the updated time.

pub fn time_since_epoch(&self) -> UnixNanos

Stores and returns current time.

pub fn make_realtime(&self)

Switches the clock to real-time mode.

pub fn make_static(&self)

Switches the clock to static mode.

Methods from Deref<Target = AtomicU64>

pub fn load(&self, order: Ordering) -> u64

Loads a value from the atomic integer.

load takes an Ordering argument which describes the memory ordering of this operation. Possible values are SeqCst, Acquire and Relaxed.

Panics

Panics if order is Release or AcqRel.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let some_var = AtomicU64::new(5);

assert_eq!(some_var.load(Ordering::Relaxed), 5);

pub fn store(&self, val: u64, order: Ordering)

Stores a value into the atomic integer.

store takes an Ordering argument which describes the memory ordering of this operation. Possible values are SeqCst, Release and Relaxed.

Panics

Panics if order is Acquire or AcqRel.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let some_var = AtomicU64::new(5);

some_var.store(10, Ordering::Relaxed);
assert_eq!(some_var.load(Ordering::Relaxed), 10);

pub fn swap(&self, val: u64, order: Ordering) -> u64

Stores a value into the atomic integer, returning the previous value.

swap takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Note: This method is only available on platforms that support atomic operations on u64.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let some_var = AtomicU64::new(5);

assert_eq!(some_var.swap(10, Ordering::Relaxed), 5);

pub fn compare_and_swap(&self, current: u64, new: u64, order: Ordering) -> u64

👎Deprecated since 1.50.0: Use compare_exchange or compare_exchange_weak instead

Stores a value into the atomic integer if the current value is the same as the current value.

The return value is always the previous value. If it is equal to current, then the value was updated.

compare_and_swap also takes an Ordering argument which describes the memory ordering of this operation. Notice that even when using AcqRel, the operation might fail and hence just perform an Acquire load, but not have Release semantics. Using Acquire makes the store part of this operation Relaxed if it happens, and using Release makes the load part Relaxed.

Note: This method is only available on platforms that support atomic operations on u64.

Migrating to compare_exchange and compare_exchange_weak

compare_and_swap is equivalent to compare_exchange with the following mapping for memory orderings:

Original	Success	Failure
Relaxed	Relaxed	Relaxed
Acquire	Acquire	Acquire
Release	Release	Relaxed
AcqRel	AcqRel	Acquire
SeqCst	SeqCst	SeqCst

compare_exchange_weak is allowed to fail spuriously even when the comparison succeeds, which allows the compiler to generate better assembly code when the compare and swap is used in a loop.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let some_var = AtomicU64::new(5);

assert_eq!(some_var.compare_and_swap(5, 10, Ordering::Relaxed), 5);
assert_eq!(some_var.load(Ordering::Relaxed), 10);

assert_eq!(some_var.compare_and_swap(6, 12, Ordering::Relaxed), 10);
assert_eq!(some_var.load(Ordering::Relaxed), 10);

pub fn compare_exchange( &self, current: u64, new: u64, success: Ordering, failure: Ordering, ) -> Result<u64, u64>

Stores a value into the atomic integer if the current value is the same as the current value.

The return value is a result indicating whether the new value was written and containing the previous value. On success this value is guaranteed to be equal to current.

compare_exchange takes two Ordering arguments to describe the memory ordering of this operation. success describes the required ordering for the read-modify-write operation that takes place if the comparison with current succeeds. failure describes the required ordering for the load operation that takes place when the comparison fails. Using Acquire as success ordering makes the store part of this operation Relaxed, and using Release makes the successful load Relaxed. The failure ordering can only be SeqCst, Acquire or Relaxed.

Note: This method is only available on platforms that support atomic operations on u64.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let some_var = AtomicU64::new(5);

assert_eq!(some_var.compare_exchange(5, 10,
                                     Ordering::Acquire,
                                     Ordering::Relaxed),
           Ok(5));
assert_eq!(some_var.load(Ordering::Relaxed), 10);

assert_eq!(some_var.compare_exchange(6, 12,
                                     Ordering::SeqCst,
                                     Ordering::Acquire),
           Err(10));
assert_eq!(some_var.load(Ordering::Relaxed), 10);

pub fn compare_exchange_weak( &self, current: u64, new: u64, success: Ordering, failure: Ordering, ) -> Result<u64, u64>

Stores a value into the atomic integer if the current value is the same as the current value.

Unlike AtomicU64::compare_exchange, this function is allowed to spuriously fail even when the comparison succeeds, which can result in more efficient code on some platforms. The return value is a result indicating whether the new value was written and containing the previous value.

compare_exchange_weak takes two Ordering arguments to describe the memory ordering of this operation. success describes the required ordering for the read-modify-write operation that takes place if the comparison with current succeeds. failure describes the required ordering for the load operation that takes place when the comparison fails. Using Acquire as success ordering makes the store part of this operation Relaxed, and using Release makes the successful load Relaxed. The failure ordering can only be SeqCst, Acquire or Relaxed.

Note: This method is only available on platforms that support atomic operations on u64.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let val = AtomicU64::new(4);

let mut old = val.load(Ordering::Relaxed);
loop {
    let new = old * 2;
    match val.compare_exchange_weak(old, new, Ordering::SeqCst, Ordering::Relaxed) {
        Ok(_) => break,
        Err(x) => old = x,
    }
}

pub fn fetch_add(&self, val: u64, order: Ordering) -> u64

Adds to the current value, returning the previous value.

This operation wraps around on overflow.

fetch_add takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Note: This method is only available on platforms that support atomic operations on u64.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let foo = AtomicU64::new(0);
assert_eq!(foo.fetch_add(10, Ordering::SeqCst), 0);
assert_eq!(foo.load(Ordering::SeqCst), 10);

pub fn fetch_sub(&self, val: u64, order: Ordering) -> u64

Subtracts from the current value, returning the previous value.

This operation wraps around on overflow.

fetch_sub takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Note: This method is only available on platforms that support atomic operations on u64.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let foo = AtomicU64::new(20);
assert_eq!(foo.fetch_sub(10, Ordering::SeqCst), 20);
assert_eq!(foo.load(Ordering::SeqCst), 10);

pub fn fetch_and(&self, val: u64, order: Ordering) -> u64

Bitwise “and” with the current value.

Performs a bitwise “and” operation on the current value and the argument val, and sets the new value to the result.

Returns the previous value.

fetch_and takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Note: This method is only available on platforms that support atomic operations on u64.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let foo = AtomicU64::new(0b101101);
assert_eq!(foo.fetch_and(0b110011, Ordering::SeqCst), 0b101101);
assert_eq!(foo.load(Ordering::SeqCst), 0b100001);

pub fn fetch_nand(&self, val: u64, order: Ordering) -> u64

Bitwise “nand” with the current value.

Performs a bitwise “nand” operation on the current value and the argument val, and sets the new value to the result.

Returns the previous value.

fetch_nand takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Note: This method is only available on platforms that support atomic operations on u64.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let foo = AtomicU64::new(0x13);
assert_eq!(foo.fetch_nand(0x31, Ordering::SeqCst), 0x13);
assert_eq!(foo.load(Ordering::SeqCst), !(0x13 & 0x31));

pub fn fetch_or(&self, val: u64, order: Ordering) -> u64

Bitwise “or” with the current value.

Performs a bitwise “or” operation on the current value and the argument val, and sets the new value to the result.

Returns the previous value.

fetch_or takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Note: This method is only available on platforms that support atomic operations on u64.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let foo = AtomicU64::new(0b101101);
assert_eq!(foo.fetch_or(0b110011, Ordering::SeqCst), 0b101101);
assert_eq!(foo.load(Ordering::SeqCst), 0b111111);

pub fn fetch_xor(&self, val: u64, order: Ordering) -> u64

Bitwise “xor” with the current value.

Performs a bitwise “xor” operation on the current value and the argument val, and sets the new value to the result.

Returns the previous value.

fetch_xor takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Note: This method is only available on platforms that support atomic operations on u64.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let foo = AtomicU64::new(0b101101);
assert_eq!(foo.fetch_xor(0b110011, Ordering::SeqCst), 0b101101);
assert_eq!(foo.load(Ordering::SeqCst), 0b011110);

pub fn fetch_update<F>( &self, set_order: Ordering, fetch_order: Ordering, f: F, ) -> Result<u64, u64>

where F: FnMut(u64) -> Option<u64>,

Fetches the value, and applies a function to it that returns an optional new value. Returns a Result of Ok(previous_value) if the function returned Some(_), else Err(previous_value).

Note: This may call the function multiple times if the value has been changed from other threads in the meantime, as long as the function returns Some(_), but the function will have been applied only once to the stored value.

fetch_update takes two Ordering arguments to describe the memory ordering of this operation. The first describes the required ordering for when the operation finally succeeds while the second describes the required ordering for loads. These correspond to the success and failure orderings of AtomicU64::compare_exchange respectively.

Using Acquire as success ordering makes the store part of this operation Relaxed, and using Release makes the final successful load Relaxed. The (failed) load ordering can only be SeqCst, Acquire or Relaxed.

Note: This method is only available on platforms that support atomic operations on u64.

Considerations

This method is not magic; it is not provided by the hardware. It is implemented in terms of AtomicU64::compare_exchange_weak, and suffers from the same drawbacks. In particular, this method will not circumvent the ABA Problem.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let x = AtomicU64::new(7);
assert_eq!(x.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |_| None), Err(7));
assert_eq!(x.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |x| Some(x + 1)), Ok(7));
assert_eq!(x.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |x| Some(x + 1)), Ok(8));
assert_eq!(x.load(Ordering::SeqCst), 9);

pub fn fetch_max(&self, val: u64, order: Ordering) -> u64

Maximum with the current value.

Finds the maximum of the current value and the argument val, and sets the new value to the result.

Returns the previous value.

fetch_max takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Note: This method is only available on platforms that support atomic operations on u64.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let foo = AtomicU64::new(23);
assert_eq!(foo.fetch_max(42, Ordering::SeqCst), 23);
assert_eq!(foo.load(Ordering::SeqCst), 42);

If you want to obtain the maximum value in one step, you can use the following:

use std::sync::atomic::{AtomicU64, Ordering};

let foo = AtomicU64::new(23);
let bar = 42;
let max_foo = foo.fetch_max(bar, Ordering::SeqCst).max(bar);
assert!(max_foo == 42);

pub fn fetch_min(&self, val: u64, order: Ordering) -> u64

Minimum with the current value.

Finds the minimum of the current value and the argument val, and sets the new value to the result.

Returns the previous value.

fetch_min takes an Ordering argument which describes the memory ordering of this operation. All ordering modes are possible. Note that using Acquire makes the store part of this operation Relaxed, and using Release makes the load part Relaxed.

Note: This method is only available on platforms that support atomic operations on u64.

Examples

use std::sync::atomic::{AtomicU64, Ordering};

let foo = AtomicU64::new(23);
assert_eq!(foo.fetch_min(42, Ordering::Relaxed), 23);
assert_eq!(foo.load(Ordering::Relaxed), 23);
assert_eq!(foo.fetch_min(22, Ordering::Relaxed), 23);
assert_eq!(foo.load(Ordering::Relaxed), 22);

If you want to obtain the minimum value in one step, you can use the following:

use std::sync::atomic::{AtomicU64, Ordering};

let foo = AtomicU64::new(23);
let bar = 12;
let min_foo = foo.fetch_min(bar, Ordering::SeqCst).min(bar);
assert_eq!(min_foo, 12);

pub fn as_ptr(&self) -> *mut u64

Returns a mutable pointer to the underlying integer.

Doing non-atomic reads and writes on the resulting integer can be a data race. This method is mostly useful for FFI, where the function signature may use *mut u64 instead of &AtomicU64.

Returning an *mut pointer from a shared reference to this atomic is safe because the atomic types work with interior mutability. All modifications of an atomic change the value through a shared reference, and can do so safely as long as they use atomic operations. Any use of the returned raw pointer requires an unsafe block and still has to uphold the same restriction: operations on it must be atomic.

Examples

use std::sync::atomic::AtomicU64;

extern "C" {
    fn my_atomic_op(arg: *mut u64);
}

let atomic = AtomicU64::new(1);

// SAFETY: Safe as long as `my_atomic_op` is atomic.
unsafe {
    my_atomic_op(atomic.as_ptr());
}

Trait Implementations

impl Debug for AtomicTime

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

Formats the value using the given formatter.

impl Default for AtomicTime

fn default() -> Self

Creates a new default AtomicTime instance.

impl Deref for AtomicTime

type Target = AtomicU64

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.