Struct haphazard::Replaced

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#[repr(transparent)]
pub struct Replaced<T, F, P> { /* private fields */ }

Expand description

A *mut T that was previously stored in an AtomicPtr.

This type exists primarily to capture the family and pointer type of the AtomicPtr the value was previously stored in, so that callers don’t need to provide F and P to Replaced::retire and Replaced::retire_in.

This type has the same in-memory representation as a std::ptr::NonNull.

Implementations§

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impl<T, F, P> Replaced<T, F, P>

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pub fn into_inner(self) -> NonNull<T>

Extract the pointer originally stored in the AtomicPtr.

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impl<T, P> Replaced<T, Global, P>where
P: Pointer<T>,

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pub unsafe fn retire(self) -> usizewhere
T: Send,

Retire the referenced object, and reclaim it once it is safe to do so.

T must be Send since it may be reclaimed by a different thread.

Safety

The pointed-to object will never again be returned by any AtomicPtr::load.
The pointed-to object has not already been retired.

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impl<T, F, P> Replaced<T, F, P>where
P: Pointer<T>,

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pub unsafe fn retire_in(self, domain: &Domain<F>) -> usizewhere
T: Send,

Retire the referenced object, and reclaim it once it is safe to do so, through the given domain.

T must be Send since it may be reclaimed by a different thread.

Safety

The pointed-to object will never again be returned by any AtomicPtr::load.
The pointed-to object has not already been retired.
All calls to load that can have seen the pointed-to object were using hazard pointers from domain.

Note that requirement #3 is partially enforced by the domain family (F), but it’s on you to ensure that you don’t “cross the streams” between multiple Domain<F>, if those can arise in your application.

Methods from Deref<Target = NonNull<T>>§

1.25.0 · source

pub unsafe fn as_ref<'a>(&self) -> &'a T

Returns a shared reference to the value. If the value may be uninitialized, as_uninit_ref must be used instead.

For the mutable counterpart see as_mut.

Safety

When calling this method, you have to ensure that all of the following is true:

The pointer must be properly aligned.
It must be “dereferenceable” in the sense defined in the module documentation.
The pointer must point to an initialized instance of T.
You must enforce Rust’s aliasing rules, since the returned lifetime 'a is arbitrarily chosen and does not necessarily reflect the actual lifetime of the data. In particular, while this reference exists, the memory the pointer points to must not get mutated (except inside UnsafeCell).

This applies even if the result of this method is unused! (The part about being initialized is not yet fully decided, but until it is, the only safe approach is to ensure that they are indeed initialized.)

Examples

use std::ptr::NonNull;

let mut x = 0u32;
let ptr = NonNull::new(&mut x as *mut _).expect("ptr is null!");

let ref_x = unsafe { ptr.as_ref() };
println!("{ref_x}");

1.25.0 · source

pub unsafe fn as_mut<'a>(&mut self) -> &'a mut T

Returns a unique reference to the value. If the value may be uninitialized, as_uninit_mut must be used instead.

For the shared counterpart see as_ref.

Safety

When calling this method, you have to ensure that all of the following is true:

The pointer must be properly aligned.
It must be “dereferenceable” in the sense defined in the module documentation.
The pointer must point to an initialized instance of T.
You must enforce Rust’s aliasing rules, since the returned lifetime 'a is arbitrarily chosen and does not necessarily reflect the actual lifetime of the data. In particular, while this reference exists, the memory the pointer points to must not get accessed (read or written) through any other pointer.

This applies even if the result of this method is unused! (The part about being initialized is not yet fully decided, but until it is, the only safe approach is to ensure that they are indeed initialized.)

Examples

use std::ptr::NonNull;

let mut x = 0u32;
let mut ptr = NonNull::new(&mut x).expect("null pointer");

let x_ref = unsafe { ptr.as_mut() };
assert_eq!(*x_ref, 0);
*x_ref += 2;
assert_eq!(*x_ref, 2);