#[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

Extract the pointer originally stored in the AtomicPtr.

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

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
  1. The pointed-to object will never again be returned by any AtomicPtr::load.
  2. The pointed-to object has not already been retired.
  3. 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>>

🔬 This is a nightly-only experimental API. (ptr_as_uninit)

Returns a shared references to the value. In contrast to as_ref, this does not require that the value has to be initialized.

For the mutable counterpart see as_uninit_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.

  • 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, for the duration of this lifetime, the memory the pointer points to must not get mutated (except inside UnsafeCell).

This applies even if the result of this method is unused!

🔬 This is a nightly-only experimental API. (ptr_as_uninit)

Returns a unique references to the value. In contrast to as_mut, this does not require that the value has to be initialized.

For the shared counterpart see as_uninit_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.

  • 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, for the duration of this lifetime, 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!

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, for the duration of this lifetime, 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}");

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, for the duration of this lifetime, 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);
🔬 This is a nightly-only experimental API. (ptr_as_uninit)

Returns a shared reference to a slice of possibly uninitialized values. In contrast to as_ref, this does not require that the value has to be initialized.

For the mutable counterpart see as_uninit_slice_mut.

Safety

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

  • The pointer must be valid for reads for ptr.len() * mem::size_of::<T>() many bytes, and it must be properly aligned. This means in particular:

    • The entire memory range of this slice must be contained within a single allocated object! Slices can never span across multiple allocated objects.

    • The pointer must be aligned even for zero-length slices. One reason for this is that enum layout optimizations may rely on references (including slices of any length) being aligned and non-null to distinguish them from other data. You can obtain a pointer that is usable as data for zero-length slices using NonNull::dangling().

  • The total size ptr.len() * mem::size_of::<T>() of the slice must be no larger than isize::MAX. See the safety documentation of pointer::offset.

  • 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, for the duration of this lifetime, the memory the pointer points to must not get mutated (except inside UnsafeCell).

This applies even if the result of this method is unused!

See also slice::from_raw_parts.

🔬 This is a nightly-only experimental API. (ptr_as_uninit)

Returns a unique reference to a slice of possibly uninitialized values. In contrast to as_mut, this does not require that the value has to be initialized.

For the shared counterpart see as_uninit_slice.

Safety

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

  • The pointer must be valid for reads and writes for ptr.len() * mem::size_of::<T>() many bytes, and it must be properly aligned. This means in particular:

    • The entire memory range of this slice must be contained within a single allocated object! Slices can never span across multiple allocated objects.

    • The pointer must be aligned even for zero-length slices. One reason for this is that enum layout optimizations may rely on references (including slices of any length) being aligned and non-null to distinguish them from other data. You can obtain a pointer that is usable as data for zero-length slices using NonNull::dangling().

  • The total size ptr.len() * mem::size_of::<T>() of the slice must be no larger than isize::MAX. See the safety documentation of pointer::offset.

  • 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, for the duration of this lifetime, 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!

See also slice::from_raw_parts_mut.

Examples
#![feature(allocator_api, ptr_as_uninit)]

use std::alloc::{Allocator, Layout, Global};
use std::mem::MaybeUninit;
use std::ptr::NonNull;

let memory: NonNull<[u8]> = Global.allocate(Layout::new::<[u8; 32]>())?;
// This is safe as `memory` is valid for reads and writes for `memory.len()` many bytes.
// Note that calling `memory.as_mut()` is not allowed here as the content may be uninitialized.
let slice: &mut [MaybeUninit<u8>] = unsafe { memory.as_uninit_slice_mut() };

Trait Implementations

Converts this type into a shared reference of the (usually inferred) input type.

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

The resulting type after dereferencing.

Dereferences the value.

Mutably dereferences the value.

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

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

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into)

Uses borrowed data to replace owned data, usually by cloning. Read more

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.