impl<T> AtomicPtr<T>

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);

unsafe const 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 conflicting atomic and non-atomic accesses, or atomic accesses of different sizes, without synchronization.

const fn null() -> AtomicPtr<T>

Creates a new AtomicPtr initialized with a null pointer.

Examples

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

let atomic_ptr = AtomicPtr::<()>::null();
assert!(atomic_ptr.load(Ordering::Relaxed).is_null());

fn get_mut(self: &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);

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

Gets atomic access to a pointer.

Note: This function is only available on targets where AtomicPtr<T> has the same alignment as *const T

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);

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

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}!");
        });
    }
});

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

Gets atomic access to a slice of pointers.

Note: This function is only available on targets where AtomicPtr<T> has the same alignment as *const T

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}!");
}

const fn into_inner(self: 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);

fn load(self: &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);

fn store(self: &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);

fn swap(self: &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);

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

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);

fn compare_exchange(self: &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);

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.

fn compare_exchange_weak(self: &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,
    }
}

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.

fn fetch_update<F>(self: &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, 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, which is a particularly common pitfall for pointers!

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);

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

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, 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, which is a particularly common pitfall for pointers!

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);

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

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, 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, which is a particularly common pitfall for pointers!

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);

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

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

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);

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

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

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]));

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

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

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);

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

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

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

let mut arr = [0i64, 1];
let atom = AtomicPtr::<i64>::new(&raw mut arr[1]);
assert_eq!(atom.fetch_byte_sub(8, Ordering::Relaxed).addr(), (&raw const arr[1]).addr());
assert_eq!(atom.load(Ordering::Relaxed).addr(), (&raw const arr[0]).addr());

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

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][crate::ptr] for details.

Examples

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);

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

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][crate::ptr] for details.

Examples

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);

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

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][crate::ptr] for details.

Examples

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);

const fn as_ptr(self: &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 requirements of the memory model.

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());
}

impl<T> Any for AtomicPtr<T>

fn type_id(self: &Self) -> TypeId

impl<T> Borrow for AtomicPtr<T>

fn borrow(self: &Self) -> &T

impl<T> BorrowMut for AtomicPtr<T>

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

impl<T> Debug for AtomicPtr<T>

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

impl<T> Default for AtomicPtr<T>

fn default() -> AtomicPtr<T>

Creates a null AtomicPtr<T>.

impl<T> Freeze for AtomicPtr<T>

impl<T> From for AtomicPtr<T>

fn from(t: T) -> T

Returns the argument unchanged.

impl<T> From for AtomicPtr<T>

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

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

impl<T> Pointer for AtomicPtr<T>

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

impl<T> RefUnwindSafe for crate::sync::atomic::AtomicPtr<T>

impl<T> Send for AtomicPtr<T>

impl<T> Sync for AtomicPtr<T>

impl<T> Unpin for AtomicPtr<T>

impl<T> UnwindSafe for AtomicPtr<T>

impl<T, U> Into for AtomicPtr<T>

fn into(self: Self) -> U

Calls U::from(self).

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

impl<T, U> TryFrom for AtomicPtr<T>

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

impl<T, U> TryInto for AtomicPtr<T>

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