Struct serde::lib::core::sync::atomic::AtomicU64

1.34.0 · source ·
pub struct AtomicU64 {
    v: UnsafeCell<u64>,
}
Expand description

An integer type which can be safely shared between threads.

This type has the same in-memory representation as the underlying integer type, u64. For more about the differences between atomic types and non-atomic types as well as information about the portability of this type, please see the module-level documentation.

Note: This type is only available on platforms that support atomic loads and stores of u64.

Fields§

§v: UnsafeCell<u64>

Implementations§

source§

impl AtomicU64

const: 1.34.0 · source

pub const fn new(v: u64) -> AtomicU64

Creates a new atomic integer.

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

let atomic_forty_two = AtomicU64::new(42);
const: unstable · source

pub unsafe fn from_ptr<'a>(ptr: *mut u64) -> &'a AtomicU64

🔬This is a nightly-only experimental API. (atomic_from_ptr)

Creates a new reference to an atomic integer from a pointer.

Examples
#![feature(atomic_from_ptr, pointer_is_aligned)]
use std::sync::atomic::{self, AtomicU64};
use std::mem::align_of;

// Get a pointer to an allocated value
let ptr: *mut u64 = Box::into_raw(Box::new(0));

assert!(ptr.is_aligned_to(align_of::<AtomicU64>()));

{
    // Create an atomic view of the allocated value
    let atomic = unsafe {AtomicU64::from_ptr(ptr) };

    // Use `atomic` for atomic operations, possibly share it with other threads
    atomic.store(1, atomic::Ordering::Relaxed);
}

// It's ok to non-atomically access the value behind `ptr`,
// since the reference to the atomic ended its lifetime in the block above
assert_eq!(unsafe { *ptr }, 1);

// Deallocate the value
unsafe { drop(Box::from_raw(ptr)) }
Safety
  • ptr must be aligned to align_of::<AtomicBool>() (note that on some platforms this can be bigger than align_of::<bool>()).
  • ptr must be aligned to align_of::<AtomicU64>() (note that on some platforms this can be bigger than align_of::<u64>()).
  • ptr must be valid for both reads and writes for the whole lifetime 'a.
  • The value behind ptr must not be accessed through non-atomic operations for the whole lifetime 'a.
source

pub fn get_mut(&mut self) -> &mut u64

Returns a mutable reference to the underlying integer.

This is safe because the mutable reference guarantees that no other threads are concurrently accessing the atomic data.

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

let mut some_var = AtomicU64::new(10);
assert_eq!(*some_var.get_mut(), 10);
*some_var.get_mut() = 5;
assert_eq!(some_var.load(Ordering::SeqCst), 5);
source

pub fn from_mut(v: &mut u64) -> &mut AtomicU64

🔬This is a nightly-only experimental API. (atomic_from_mut)

Get atomic access to a &mut u64.

Note: This function is only available on targets where u64 has an alignment of 8 bytes.

Examples
#![feature(atomic_from_mut)]
use std::sync::atomic::{AtomicU64, Ordering};

let mut some_int = 123;
let a = AtomicU64::from_mut(&mut some_int);
a.store(100, Ordering::Relaxed);
assert_eq!(some_int, 100);
source

pub fn get_mut_slice(this: &mut [AtomicU64]) -> &mut [u64]

🔬This is a nightly-only experimental API. (atomic_from_mut)

Get non-atomic access to a &mut [AtomicU64] slice

This is safe because the mutable reference guarantees that no other threads are concurrently accessing the atomic data.

Examples
#![feature(atomic_from_mut, inline_const)]
use std::sync::atomic::{AtomicU64, Ordering};

let mut some_ints = [const { AtomicU64::new(0) }; 10];

let view: &mut [u64] = AtomicU64::get_mut_slice(&mut some_ints);
assert_eq!(view, [0; 10]);
view
    .iter_mut()
    .enumerate()
    .for_each(|(idx, int)| *int = idx as _);

std::thread::scope(|s| {
    some_ints
        .iter()
        .enumerate()
        .for_each(|(idx, int)| {
            s.spawn(move || assert_eq!(int.load(Ordering::Relaxed), idx as _));
        })
});
source

pub fn from_mut_slice(v: &mut [u64]) -> &mut [AtomicU64]

🔬This is a nightly-only experimental API. (atomic_from_mut)

Get atomic access to a &mut [u64] slice.

Examples
#![feature(atomic_from_mut)]
use std::sync::atomic::{AtomicU64, Ordering};

let mut some_ints = [0; 10];
let a = &*AtomicU64::from_mut_slice(&mut some_ints);
std::thread::scope(|s| {
    for i in 0..a.len() {
        s.spawn(move || a[i].store(i as _, Ordering::Relaxed));
    }
});
for (i, n) in some_ints.into_iter().enumerate() {
    assert_eq!(i, n as usize);
}
const: unstable · source

pub fn into_inner(self) -> u64

Consumes the atomic and returns the contained value.

This is safe because passing self by value guarantees that no other threads are concurrently accessing the atomic data.

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

let some_var = AtomicU64::new(5);
assert_eq!(some_var.into_inner(), 5);
source

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);
source

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);
source

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);
source

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

👎Deprecated since 1.50.0: Use <code>compare_exchange</code> or <code>compare_exchange_weak</code> 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:

OriginalSuccessFailure
RelaxedRelaxedRelaxed
AcquireAcquireAcquire
ReleaseReleaseRelaxed
AcqRelAcqRelAcquire
SeqCstSeqCstSeqCst

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);
source

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);
source

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,
    }
}
source

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);
source

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);
source

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);
source

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));
source

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);
source

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);
1.45.0 · source

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);
1.45.0 · source

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);
1.45.0 · source

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);
1.70.0-nightly (const: 1.70.0-nightly) · source

pub const 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§

source§

impl Debug for AtomicU64

source§

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

Formats the value using the given formatter. Read more
const: unstable · source§

impl Default for AtomicU64

const: unstable · source§

fn default() -> AtomicU64

Returns the “default value” for a type. Read more
source§

impl<'de> Deserialize<'de> for AtomicU64

source§

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

Deserialize this value from the given Serde deserializer. Read more
const: unstable · source§

impl From<u64> for AtomicU64

const: unstable · source§

fn from(v: u64) -> AtomicU64

Converts an u64 into an AtomicU64.

source§

impl Serialize for AtomicU64

source§

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

Serialize this value into the given Serde serializer. Read more
source§

impl RefUnwindSafe for AtomicU64

source§

impl Sync for AtomicU64

Auto Trait Implementations§

Blanket Implementations§

source§

impl<T> Any for Twhere T: 'static + ?Sized,

source§

fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
source§

impl<T> Borrow<T> for Twhere T: ?Sized,

const: unstable · source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
source§

impl<T> BorrowMut<T> for Twhere T: ?Sized,

const: unstable · source§

fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
source§

impl<T> From<T> for T

const: unstable · source§

fn from(t: T) -> T

Returns the argument unchanged.

source§

impl<T, U> Into<U> for Twhere U: From<T>,

const: unstable · source§

fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

source§

impl<T, U> TryFrom<U> for Twhere U: Into<T>,

§

type Error = Infallible

The type returned in the event of a conversion error.
const: unstable · source§

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
source§

impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

§

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
const: unstable · source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
source§

impl<T> DeserializeOwned for Twhere T: for<'de> Deserialize<'de>,