AtomicPtr in core::sync::atomic - Rust
Description: A raw pointer type which can be safely shared between threads.

# Struct AtomicPtr

1.6.0 · Source

    #[repr(C, align(8))]pub struct AtomicPtr<T> { /* private fields */ }

Expand description

A raw pointer type which can be safely shared between threads.

This type has the same size and bit validity as a `*mut T`.

Note: This type is only available on platforms that support atomic loads and stores of pointers. Its size depends on the target pointer’s size.

## Implementations§

Source§

### impl<T> AtomicPtr<T>

1.0.0 (const: 1.24.0) · Source

#### pub const fn new(p: *mut T) -> AtomicPtr<T>

Creates a new `AtomicPtr`.

##### §Examples

    use std::sync::atomic::AtomicPtr;

    let ptr = &mut 5;
    let atomic_ptr = AtomicPtr::new(ptr);

1.75.0 (const: 1.84.0) · Source

#### pub const unsafe fn from_ptr<'a>(ptr: *mut *mut T) -> &'a AtomicPtr<T>

Creates a new `AtomicPtr` from a pointer.

##### §Examples

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

    // Get a pointer to an allocated value
    let ptr: *mut *mut u8 = Box::into_raw(Box::new(std::ptr::null_mut()));

    assert!(ptr.cast::<AtomicPtr<u8>>().is_aligned());

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

        // Use `atomic` for atomic operations, possibly share it with other threads
        atomic.store(std::ptr::NonNull::dangling().as_ptr(), 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!(!unsafe { *ptr }.is_null());

    // Deallocate the value
    unsafe { drop(Box::from_raw(ptr)) }

##### §Safety

- `ptr` must be aligned to `align_of::<AtomicPtr<T>>()` (note that on some platforms this can be bigger than `align_of::<*mut T>()`).
- `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 atomic and non-atomic accesses, or atomic accesses of different sizes, without synchronization.

1.15.0 · Source

#### pub fn get_mut(&mut self) -> &mut *mut T

Returns a mutable reference to the underlying pointer.

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

##### §Examples

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

    let mut data = 10;
    let mut atomic_ptr = AtomicPtr::new(&mut data);
    let mut other_data = 5;
    *atomic_ptr.get_mut() = &mut other_data;
    assert_eq!(unsafe { *atomic_ptr.load(Ordering::SeqCst) }, 5);

Source

#### pub fn from_mut(v: &mut *mut T) -> &mut Self

🔬This is a nightly-only experimental API. (`atomic_from_mut` #76314)

Gets atomic access to a pointer.

##### §Examples

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

    let mut data = 123;
    let mut some_ptr = &mut data as *mut i32;
    let a = AtomicPtr::from_mut(&mut some_ptr);
    let mut other_data = 456;
    a.store(&mut other_data, Ordering::Relaxed);
    assert_eq!(unsafe { *some_ptr }, 456);

Source

#### pub fn get_mut_slice(this: &mut [Self]) -> &mut [*mut T]

🔬This is a nightly-only experimental API. (`atomic_from_mut` #76314)

Gets non-atomic access to a `&mut [AtomicPtr]` 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::ptr::null_mut;
    use std::sync::atomic::{AtomicPtr, Ordering};

    let mut some_ptrs = [const { AtomicPtr::new(null_mut::<String>()) }; 10];

    let view: &mut [*mut String] = AtomicPtr::get_mut_slice(&mut some_ptrs);
    assert_eq!(view, [null_mut::<String>(); 10]);
    view
        .iter_mut()
        .enumerate()
        .for_each(|(i, ptr)| *ptr = Box::into_raw(Box::new(format!("iteration#{i}"))));

    std::thread::scope(|s| {
        for ptr in &some_ptrs {
            s.spawn(move || {
                let ptr = ptr.load(Ordering::Relaxed);
                assert!(!ptr.is_null());

                let name = unsafe { Box::from_raw(ptr) };
                println!("Hello, {name}!");
            });
        }
    });

Source

#### pub fn from_mut_slice(v: &mut [*mut T]) -> &mut [Self]

🔬This is a nightly-only experimental API. (`atomic_from_mut` #76314)

Gets atomic access to a slice of pointers.

##### §Examples

    #![feature(atomic_from_mut)]
    use std::ptr::null_mut;
    use std::sync::atomic::{AtomicPtr, Ordering};

    let mut some_ptrs = [null_mut::<String>(); 10];
    let a = &*AtomicPtr::from_mut_slice(&mut some_ptrs);
    std::thread::scope(|s| {
        for i in 0..a.len() {
            s.spawn(move || {
                let name = Box::new(format!("thread{i}"));
                a[i].store(Box::into_raw(name), Ordering::Relaxed);
            });
        }
    });
    for p in some_ptrs {
        assert!(!p.is_null());
        let name = unsafe { Box::from_raw(p) };
        println!("Hello, {name}!");
    }

1.15.0 (const: 1.79.0) · Source

#### pub const fn into_inner(self) -> *mut T

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::AtomicPtr;

    let mut data = 5;
    let atomic_ptr = AtomicPtr::new(&mut data);
    assert_eq!(unsafe { *atomic_ptr.into_inner() }, 5);

1.0.0 · Source

#### pub fn load(&self, order: Ordering) -> *mut T

Loads a value from the pointer.

`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::{AtomicPtr, Ordering};

    let ptr = &mut 5;
    let some_ptr = AtomicPtr::new(ptr);

    let value = some_ptr.load(Ordering::Relaxed);

1.0.0 · Source

#### pub fn store(&self, ptr: *mut T, order: Ordering)

Stores a value into the pointer.

`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::{AtomicPtr, Ordering};

    let ptr = &mut 5;
    let some_ptr = AtomicPtr::new(ptr);

    let other_ptr = &mut 10;

    some_ptr.store(other_ptr, Ordering::Relaxed);

1.0.0 · Source

#### pub fn swap(&self, ptr: *mut T, order: Ordering) -> *mut T

Stores a value into the pointer, 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 pointers.

##### §Examples

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

    let ptr = &mut 5;
    let some_ptr = AtomicPtr::new(ptr);

    let other_ptr = &mut 10;

    let value = some_ptr.swap(other_ptr, Ordering::Relaxed);

1.0.0 · Source

#### pub fn compare_and_swap( &self, current: *mut T, new: *mut T, order: Ordering, ) -> *mut T

👎Deprecated since 1.50.0: Use `compare_exchange` or `compare_exchange_weak` instead

Stores a value into the pointer 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 pointers.

##### §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::{AtomicPtr, Ordering};

    let ptr = &mut 5;
    let some_ptr = AtomicPtr::new(ptr);

    let other_ptr = &mut 10;

    let value = some_ptr.compare_and_swap(ptr, other_ptr, Ordering::Relaxed);

1.10.0 · Source

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

Stores a value into the pointer 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 pointers.

##### §Examples

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

    let ptr = &mut 5;
    let some_ptr = AtomicPtr::new(ptr);

    let other_ptr = &mut 10;

    let value = some_ptr.compare_exchange(ptr, other_ptr,
                                          Ordering::SeqCst, Ordering::Relaxed);

1.10.0 · Source

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

Stores a value into the pointer if the current value is the same as the `current` value.

Unlike `AtomicPtr::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 pointers.

##### §Examples

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

    let some_ptr = AtomicPtr::new(&mut 5);

    let new = &mut 10;
    let mut old = some_ptr.load(Ordering::Relaxed);
    loop {
        match some_ptr.compare_exchange_weak(old, new, Ordering::SeqCst, Ordering::Relaxed) {
            Ok(_) => break,
            Err(x) => old = x,
        }
    }

1.53.0 · Source

#### pub fn fetch_update<F>( &self, set_order: Ordering, fetch_order: Ordering, f: F, ) -> Result<*mut T, *mut T>
where F: FnMut(*mut T) -> Option<*mut T>,

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 `AtomicPtr::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 pointers.

##### §Considerations

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

##### §Examples

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

    let ptr: *mut _ = &mut 5;
    let some_ptr = AtomicPtr::new(ptr);

    let new: *mut _ = &mut 10;
    assert_eq!(some_ptr.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |_| None), Err(ptr));
    let result = some_ptr.fetch_update(Ordering::SeqCst, Ordering::SeqCst, |x| {
        if x == ptr {
            Some(new)
        } else {
            None
        }
    });
    assert_eq!(result, Ok(ptr));
    assert_eq!(some_ptr.load(Ordering::SeqCst), new);

Source

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

🔬This is a nightly-only experimental API. (`atomic_try_update` #135894)

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 `AtomicPtr::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 pointers.

##### §Considerations

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

##### §Examples

    #![feature(atomic_try_update)]
    use std::sync::atomic::{AtomicPtr, Ordering};

    let ptr: *mut _ = &mut 5;
    let some_ptr = AtomicPtr::new(ptr);

    let new: *mut _ = &mut 10;
    assert_eq!(some_ptr.try_update(Ordering::SeqCst, Ordering::SeqCst, |_| None), Err(ptr));
    let result = some_ptr.try_update(Ordering::SeqCst, Ordering::SeqCst, |x| {
        if x == ptr {
            Some(new)
        } else {
            None
        }
    });
    assert_eq!(result, Ok(ptr));
    assert_eq!(some_ptr.load(Ordering::SeqCst), new);

Source

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

🔬This is a nightly-only experimental API. (`atomic_try_update` #135894)

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 `AtomicPtr::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 pointers.

##### §Considerations

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

##### §Examples

    #![feature(atomic_try_update)]

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

    let ptr: *mut _ = &mut 5;
    let some_ptr = AtomicPtr::new(ptr);

    let new: *mut _ = &mut 10;
    let result = some_ptr.update(Ordering::SeqCst, Ordering::SeqCst, |_| new);
    assert_eq!(result, ptr);
    assert_eq!(some_ptr.load(Ordering::SeqCst), new);

Source

#### pub fn fetch_ptr_add(&self, val: usize, order: Ordering) -> *mut T

🔬This is a nightly-only experimental API. (`strict_provenance_atomic_ptr` #99108)

Offsets the pointer’s address by adding `val` (in units of `T`), returning the previous pointer.

This is equivalent to using `wrapping_add` to atomically perform the equivalent of `ptr = ptr.wrapping_add(val);`.

This method operates in units of `T`, which means that it cannot be used to offset the pointer by an amount which is not a multiple of `size_of::<T>()`. This can sometimes be inconvenient, as you may want to work with a deliberately misaligned pointer. In such cases, you may use the `fetch_byte_add` method instead.

`fetch_ptr_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 `AtomicPtr`.

##### §Examples

    #![feature(strict_provenance_atomic_ptr)]
    use core::sync::atomic::{AtomicPtr, Ordering};

    let atom = AtomicPtr::<i64>::new(core::ptr::null_mut());
    assert_eq!(atom.fetch_ptr_add(1, Ordering::Relaxed).addr(), 0);
    // Note: units of `size_of::<i64>()`.
    assert_eq!(atom.load(Ordering::Relaxed).addr(), 8);

Source

#### pub fn fetch_ptr_sub(&self, val: usize, order: Ordering) -> *mut T

🔬This is a nightly-only experimental API. (`strict_provenance_atomic_ptr` #99108)

Offsets the pointer’s address by subtracting `val` (in units of `T`), returning the previous pointer.

This is equivalent to using `wrapping_sub` to atomically perform the equivalent of `ptr = ptr.wrapping_sub(val);`.

This method operates in units of `T`, which means that it cannot be used to offset the pointer by an amount which is not a multiple of `size_of::<T>()`. This can sometimes be inconvenient, as you may want to work with a deliberately misaligned pointer. In such cases, you may use the `fetch_byte_sub` method instead.

`fetch_ptr_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 `AtomicPtr`.

##### §Examples

    #![feature(strict_provenance_atomic_ptr)]
    use core::sync::atomic::{AtomicPtr, Ordering};

    let array = [1i32, 2i32];
    let atom = AtomicPtr::new(array.as_ptr().wrapping_add(1) as *mut _);

    assert!(core::ptr::eq(
        atom.fetch_ptr_sub(1, Ordering::Relaxed),
        &array[1],
    ));
    assert!(core::ptr::eq(atom.load(Ordering::Relaxed), &array[0]));

Source

#### pub fn fetch_byte_add(&self, val: usize, order: Ordering) -> *mut T

🔬This is a nightly-only experimental API. (`strict_provenance_atomic_ptr` #99108)

Offsets the pointer’s address by adding `val` bytes, returning the previous pointer.

This is equivalent to using `wrapping_byte_add` to atomically perform `ptr = ptr.wrapping_byte_add(val)`.

`fetch_byte_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 `AtomicPtr`.

##### §Examples

    #![feature(strict_provenance_atomic_ptr)]
    use core::sync::atomic::{AtomicPtr, Ordering};

    let atom = AtomicPtr::<i64>::new(core::ptr::null_mut());
    assert_eq!(atom.fetch_byte_add(1, Ordering::Relaxed).addr(), 0);
    // Note: in units of bytes, not `size_of::<i64>()`.
    assert_eq!(atom.load(Ordering::Relaxed).addr(), 1);

Source

#### pub fn fetch_byte_sub(&self, val: usize, order: Ordering) -> *mut T

🔬This is a nightly-only experimental API. (`strict_provenance_atomic_ptr` #99108)

Offsets the pointer’s address by subtracting `val` bytes, returning the previous pointer.

This is equivalent to using `wrapping_byte_sub` to atomically perform `ptr = ptr.wrapping_byte_sub(val)`.

`fetch_byte_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 `AtomicPtr`.

##### §Examples

    #![feature(strict_provenance_atomic_ptr)]
    use core::sync::atomic::{AtomicPtr, Ordering};

    let atom = AtomicPtr::<i64>::new(core::ptr::without_provenance_mut(1));
    assert_eq!(atom.fetch_byte_sub(1, Ordering::Relaxed).addr(), 1);
    assert_eq!(atom.load(Ordering::Relaxed).addr(), 0);

Source

#### pub fn fetch_or(&self, val: usize, order: Ordering) -> *mut T

🔬This is a nightly-only experimental API. (`strict_provenance_atomic_ptr` #99108)

Performs a bitwise “or” operation on the address of the current pointer, and the argument `val`, and stores a pointer with provenance of the current pointer and the resulting address.

This is equivalent to using `map_addr` to atomically perform `ptr = ptr.map_addr(|a| a | val)`. This can be used in tagged pointer schemes to atomically set tag bits.

Caveat: This operation returns the previous value. To compute the stored value without losing provenance, you may use `map_addr`. For example: `a.fetch_or(val).map_addr(|a| a | val)`.

`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 `AtomicPtr`.

This API and its claimed semantics are part of the Strict Provenance experiment, see the module documentation for `ptr` for details.

##### §Examples

    #![feature(strict_provenance_atomic_ptr)]
    use core::sync::atomic::{AtomicPtr, Ordering};

    let pointer = &mut 3i64 as *mut i64;

    let atom = AtomicPtr::<i64>::new(pointer);
    // Tag the bottom bit of the pointer.
    assert_eq!(atom.fetch_or(1, Ordering::Relaxed).addr() & 1, 0);
    // Extract and untag.
    let tagged = atom.load(Ordering::Relaxed);
    assert_eq!(tagged.addr() & 1, 1);
    assert_eq!(tagged.map_addr(|p| p & !1), pointer);

Source

#### pub fn fetch_and(&self, val: usize, order: Ordering) -> *mut T

🔬This is a nightly-only experimental API. (`strict_provenance_atomic_ptr` #99108)

Performs a bitwise “and” operation on the address of the current pointer, and the argument `val`, and stores a pointer with provenance of the current pointer and the resulting address.

This is equivalent to using `map_addr` to atomically perform `ptr = ptr.map_addr(|a| a & val)`. This can be used in tagged pointer schemes to atomically unset tag bits.

Caveat: This operation returns the previous value. To compute the stored value without losing provenance, you may use `map_addr`. For example: `a.fetch_and(val).map_addr(|a| a & val)`.

`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 `AtomicPtr`.

This API and its claimed semantics are part of the Strict Provenance experiment, see the module documentation for `ptr` for details.

##### §Examples

    #![feature(strict_provenance_atomic_ptr)]
    use core::sync::atomic::{AtomicPtr, Ordering};

    let pointer = &mut 3i64 as *mut i64;
    // A tagged pointer
    let atom = AtomicPtr::<i64>::new(pointer.map_addr(|a| a | 1));
    assert_eq!(atom.fetch_or(1, Ordering::Relaxed).addr() & 1, 1);
    // Untag, and extract the previously tagged pointer.
    let untagged = atom.fetch_and(!1, Ordering::Relaxed)
        .map_addr(|a| a & !1);
    assert_eq!(untagged, pointer);

Source

#### pub fn fetch_xor(&self, val: usize, order: Ordering) -> *mut T

🔬This is a nightly-only experimental API. (`strict_provenance_atomic_ptr` #99108)

Performs a bitwise “xor” operation on the address of the current pointer, and the argument `val`, and stores a pointer with provenance of the current pointer and the resulting address.

This is equivalent to using `map_addr` to atomically perform `ptr = ptr.map_addr(|a| a ^ val)`. This can be used in tagged pointer schemes to atomically toggle tag bits.

Caveat: This operation returns the previous value. To compute the stored value without losing provenance, you may use `map_addr`. For example: `a.fetch_xor(val).map_addr(|a| a ^ val)`.

`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 `AtomicPtr`.

This API and its claimed semantics are part of the Strict Provenance experiment, see the module documentation for `ptr` for details.

##### §Examples

    #![feature(strict_provenance_atomic_ptr)]
    use core::sync::atomic::{AtomicPtr, Ordering};

    let pointer = &mut 3i64 as *mut i64;
    let atom = AtomicPtr::<i64>::new(pointer);

    // Toggle a tag bit on the pointer.
    atom.fetch_xor(1, Ordering::Relaxed);
    assert_eq!(atom.load(Ordering::Relaxed).addr() & 1, 1);

1.70.0 (const: 1.70.0) · Source

#### pub const fn as_ptr(&self) -> *mut *mut T

Returns a mutable pointer to the underlying pointer.

Doing non-atomic reads and writes on the resulting pointer can be a data race. This method is mostly useful for FFI, where the function signature may use `*mut *mut T` instead of `&AtomicPtr<T>`.

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::AtomicPtr;

    extern "C" {
        fn my_atomic_op(arg: *mut *mut u32);
    }

    let mut value = 17;
    let atomic = AtomicPtr::new(&mut value);

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

## Trait Implementations§

1.3.0 · Source§

### impl<T> Debug for AtomicPtr<T>

Source§

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

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

### impl<T> Default for AtomicPtr<T>

Source§

#### fn default() -> AtomicPtr<T>

Creates a null `AtomicPtr<T>`.

1.23.0 · Source§

### impl<T> From<*mut T> for AtomicPtr<T>

Source§

#### fn from(p: *mut T) -> Self

Converts a `*mut T` into an `AtomicPtr<T>`.

1.24.0 · Source§

### impl<T> Pointer for AtomicPtr<T>

Source§

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

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

### impl<T> RefUnwindSafe for AtomicPtr<T>

1.0.0 · Source§

### impl<T> Send for AtomicPtr<T>

1.0.0 · Source§

### impl<T> Sync for AtomicPtr<T>

## Auto Trait Implementations§

§

### impl<T> !Freeze for AtomicPtr<T>

§

### impl<T> Unpin for AtomicPtr<T>

§

### impl<T> UnwindSafe for AtomicPtr<T>
where T: RefUnwindSafe,

## Blanket Implementations§

Source§

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

Source§

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

Gets the `TypeId` of `self`. Read more
Source§

### impl<T> Borrow<T> for T
where T: ?Sized,

Source§

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

Immutably borrows from an owned value. Read more
Source§

### impl<T> BorrowMut<T> for T
where T: ?Sized,

Source§

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

Mutably borrows from an owned value. Read more
Source§

### impl<T> From<T> for T

Source§

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

Returns the argument unchanged.

Source§

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

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 T
where U: Into<T>,

Source§

#### type Error = Infallible

The type returned in the event of a conversion error.
Source§

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

Performs the conversion.
Source§

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

Source§

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

The type returned in the event of a conversion error.
Source§

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

Performs the conversion.