#[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 in-memory representation 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
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);Get 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);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);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);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);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);👎 Deprecated since 1.50.0: Use compare_exchange or compare_exchange_weak instead
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_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);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
and must be equivalent to or weaker than the success ordering.
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);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
and must be equivalent to or weaker than the success ordering.
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,
}
}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 and must be equivalent to or weaker than the
success ordering.
Note: This method is only available on platforms that support atomic operations on 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);