Struct ArcBox 

pub struct ArcBox<T: ?Sized>(/* private fields */);

An Arc that is known to be uniquely owned

When Arcs are constructed, they are known to be uniquely owned. In such a case it is safe to mutate the contents of the Arc. Normally, one would just handle this by mutating the data on the stack before allocating the Arc, however it’s possible the data is large or unsized and you need to heap-allocate it earlier in such a way that it can be freely converted into a regular Arc once you’re done.

ArcBox exists for this purpose, when constructed it performs the same allocations necessary for an Arc, however it allows mutable access. Once the mutation is finished, you can call .shareable() and get a regular Arc out of it.

let data = [1, 2, 3, 4, 5];
let mut x = ArcBox::new(data);
x[4] = 7; // mutate!
let y = x.shareable(); // y is an Arc<T>

Implementations

impl<T> ArcBox<T>

pub fn new(data: T) -> Self

Construct a new ArcBox

pub fn new_uninit() -> ArcBox<MaybeUninit<T>>

Construct an uninitialized ArcBox

pub fn into_inner(this: Self) -> T

Gets the inner value of this ArcBox

pub fn shareable_ref(self) -> ArcRef<'static, T>

Convert to a shareable ArcRef<'static, T> once we’re done mutating it

impl<T: ?Sized> ArcBox<T>

pub fn shareable(self) -> Arc<T>

Convert to a shareable Arc<T> once we’re done mutating it

impl<T> ArcBox<MaybeUninit<T>>

pub unsafe fn assume_init(this: Self) -> ArcBox<T>

Convert to an initialized Arc.

Safety

This function is equivalent to MaybeUninit::assume_init and has the same safety requirements. You are responsible for ensuring that the T has actually been initialized before calling this method.

Trait Implementations

impl<S: ?Sized + SliceDst> AllocSliceDst<S> for ArcBox<S>

This implementation is based on that in the documentation for slice-dst.

Safety

This function merely calls try_new_slice with an initializer statically guaranteed never to fail, and therefore is safe if and only if try_new_slice is.

unsafe fn new_slice_dst<I>(len: usize, init: I) -> Self

where I: FnOnce(NonNull<S>),

Create a new custom slice DST.

impl<T: ?Sized> AsMut<T> for ArcBox<T>

fn as_mut(&mut self) -> &mut T

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

impl<T: ?Sized> AsRef<T> for ArcBox<T>

fn as_ref(&self) -> &T

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

impl<T: ?Sized> Borrow<T> for ArcBox<T>

fn borrow(&self) -> &T

Immutably borrows from an owned value.

impl<T: ?Sized> BorrowMut<T> for ArcBox<T>

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

Mutably borrows from an owned value.

impl<T: Clone> Clone for ArcBox<T>

fn clone(&self) -> ArcBox<T>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T, U: ?Sized> CoerciblePtr<U> for ArcBox<T>

Safety

This leverages the correctness of Arc’s CoerciblePtr impl. Additionally, we must ensure that this can not be used to violate the safety invariants of ArcBox, which require that we can not duplicate the Arc, such that replace_ptr returns a valid instance. This holds since it consumes a unique owner of the contained ArcInner.

type Pointee = T

The type we point to. This influences which kinds of unsizing are possible.

type Output = ArcBox<U>

The output type when unsizing the pointee to U.

fn as_sized_ptr(&mut self) -> *mut T

Get the raw inner pointer.

unsafe fn replace_ptr(self, new: *mut U) -> ArcBox<U>

Replace the container inner pointer with an unsized version.

impl<T: Debug> Debug for ArcBox<T>

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

Formats the value using the given formatter.

impl<T: Default> Default for ArcBox<T>

fn default() -> ArcBox<T>

Returns the “default value” for a type.

impl<T: ?Sized> Deref for ArcBox<T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Dereferences the value.

impl<T: ?Sized> DerefMut for ArcBox<T>

fn deref_mut(&mut self) -> &mut T

Mutably dereferences the value.

impl<T: Display> Display for ArcBox<T>

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

Formats the value using the given formatter.

impl<S: ?Sized + SliceDst> TryAllocSliceDst<S> for ArcBox<S>

Safety

unsafe fn try_new_slice_dst<I, E>(len: usize, init: I) -> Result<Self, E>

where I: FnOnce(NonNull<S>) -> Result<(), E>,

Create a new custom slice DST with a fallible initialization function.

impl<T: ?Sized> TryFrom<Arc<T>> for ArcBox<T>

type Error = Arc<T>

The type returned in the event of a conversion error.

fn try_from(arc: Arc<T>) -> Result<Self, Self::Error>

Performs the conversion.