AtomicU64 in std::sync::atomic - Rust
Description: An integer type which can be safely shared between threads.

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## AtomicU64

# Struct AtomicU64

1.34.0 · Source

    pub struct AtomicU64 { /* private fields */ }

Expand description

An integer type which can be safely shared between threads.

This type has the same size and bit validity as the underlying integer type, `u64`. However, the alignment of this type is always equal to its size, even on targets where `u64` has a lesser alignment.

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`.

## Implementations§

Source§

### impl AtomicU64

1.34.0 (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);

1.75.0 (const: 1.84.0) · Source

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

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

##### §Examples

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

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

    assert!(ptr.cast::<AtomicU64>().is_aligned());

    {
        // 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::<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`.
- You must adhere to the Memory model for atomic accesses. In particular, it is not allowed to mix conflicting atomic and non-atomic accesses, or atomic accesses of different sizes, without synchronization.

1.34.0 · 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` #76314)
Available on `target_has_atomic_equal_alignment=64` only.

Get atomic access to a `&mut u64`.

Note: This function is only available on targets where `AtomicU64` has the same alignment as `u64`.

##### §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` #76314)

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)]
    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` #76314)
Available on `target_has_atomic_equal_alignment=64` only.

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

Note: This function is only available on targets where `AtomicU64` has the same alignment as `u64`.

##### §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);
    }

1.34.0 (const: 1.79.0) · Source

#### pub const 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);

1.34.0 · 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);

1.34.0 · 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);

1.34.0 · Source

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

Available on `target_has_atomic=64` only.

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);

1.34.0 · Source

#### 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
Available on `target_has_atomic=64` only.

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_and_swap` and `compare_exchange` also differ in their return type. You can use `compare_exchange(...).unwrap_or_else(|x| x)` to recover the behavior of `compare_and_swap`, but in most cases it is more idiomatic to check whether the return value is `Ok` or `Err` rather than to infer success vs failure based on the value that was read.

During migration, consider whether it makes sense to use `compare_exchange_weak` instead. `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);

1.34.0 · Source

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

Available on `target_has_atomic=64` only.

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);

##### §Considerations

`compare_exchange` is a compare-and-swap operation and thus exhibits the usual downsides of CAS operations. In particular, a load of the value followed by a successful `compare_exchange` with the previous load does not ensure that other threads have not changed the value in the interim! This is usually important when the equality check in the `compare_exchange` is being used to check the identity of a value, but equality does not necessarily imply identity. This is a particularly common case for pointers, as a pointer holding the same address does not imply that the same object exists at that address! In this case, `compare_exchange` can lead to the ABA problem.

1.34.0 · Source

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

Available on `target_has_atomic=64` only.

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,
        }
    }

##### §Considerations

`compare_exchange` is a compare-and-swap operation and thus exhibits the usual downsides of CAS operations. In particular, a load of the value followed by a successful `compare_exchange` with the previous load does not ensure that other threads have not changed the value in the interim. This is usually important when the equality check in the `compare_exchange` is being used to check the identity of a value, but equality does not necessarily imply identity. This is a particularly common case for pointers, as a pointer holding the same address does not imply that the same object exists at that address! In this case, `compare_exchange` can lead to the ABA problem.

1.34.0 · Source

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

Available on `target_has_atomic=64` only.

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);

1.34.0 · Source

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

Available on `target_has_atomic=64` only.

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);

1.34.0 · Source

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

Available on `target_has_atomic=64` only.

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);

1.34.0 · Source

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

Available on `target_has_atomic=64` only.

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));

1.34.0 · Source

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

Available on `target_has_atomic=64` only.

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);

1.34.0 · Source

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

Available on `target_has_atomic=64` only.

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>,

👎Deprecating in 1.99.0: renamed to `try_update` for consistency
Available on `target_has_atomic=64` only.

An alias for `AtomicU64::try_update` .

1.95.0 · Source

#### pub fn try_update( &self, set_order: Ordering, fetch_order: Ordering, f: impl FnMut(u64) -> Option<u64>, ) -> Result<u64, u64>

Available on `target_has_atomic=64` only.

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)`.

See also: `update`.

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.

`try_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, and does not act like a critical section or mutex.

It is implemented on top of an atomic compare-and-swap operation, and thus is subject to the usual drawbacks of CAS operations. In particular, be careful of the ABA problem if this atomic integer is an index or more generally if knowledge of only the bitwise value of the atomic is not in and of itself sufficient to ensure any required preconditions.

##### §Examples

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

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

1.95.0 · Source

#### pub fn update( &self, set_order: Ordering, fetch_order: Ordering, f: impl FnMut(u64) -> u64, ) -> u64

Available on `target_has_atomic=64` only.

Fetches the value, applies a function to it that it return a new value. The new value is stored and the old value is returned.

See also: `try_update`.

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

`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, and does not act like a critical section or mutex.

It is implemented on top of an atomic compare-and-swap operation, and thus is subject to the usual drawbacks of CAS operations. In particular, be careful of the ABA problem if this atomic integer is an index or more generally if knowledge of only the bitwise value of the atomic is not in and of itself sufficient to ensure any required preconditions.

##### §Examples

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

    let x = AtomicU64::new(7);
    assert_eq!(x.update(Ordering::SeqCst, Ordering::SeqCst, |x| x + 1), 7);
    assert_eq!(x.update(Ordering::SeqCst, Ordering::SeqCst, |x| x + 1), 8);
    assert_eq!(x.load(Ordering::SeqCst), 9);

1.45.0 · Source

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

Available on `target_has_atomic=64` only.

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

Available on `target_has_atomic=64` only.

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 (const: 1.70.0) · 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 requirements of the memory model.

##### §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§

1.34.0 · Source§

### impl Debug for AtomicU64

Source§

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

Formats the value using the given formatter. Read more
1.34.0 · Source§

### impl Default for AtomicU64

Source§

#### fn default() -> AtomicU64

Returns the “default value” for a type. Read more
1.34.0 (const: unstable) · Source§

### impl From<u64> for AtomicU64

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#### fn from(v: u64) -> AtomicU64

Converts an `u64` into an `AtomicU64`.

1.34.0 · Source§

### impl RefUnwindSafe for AtomicU64

Available on `target_has_atomic_load_store=64` only.
1.34.0 · Source§

### impl Sync for AtomicU64

## Auto Trait Implementations§

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### impl !Freeze for AtomicU64

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### impl Send for AtomicU64

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### impl Unpin for AtomicU64

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### impl UnsafeUnpin for AtomicU64

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### impl UnwindSafe for AtomicU64

## Blanket Implementations§

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

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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

Mutably borrows from an owned value. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

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

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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.