Struct Arc

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pub struct Arc<T: ?Sized> { /* private fields */ }

Expand description

Mock implementation of std::sync::Arc.

Implementations§

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impl<T> Arc<T>

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pub fn new(value: T) -> Arc<T>

Constructs a new Arc<T>.

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pub fn pin(data: T) -> Pin<Arc<T>>

Constructs a new Pin<Arc<T>>.

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pub fn try_unwrap(this: Arc<T>) -> Result<T, Arc<T>>

Returns the inner value, if the Arc has exactly one strong reference.

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impl<T: ?Sized> Arc<T>

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pub fn from_std(std: Arc<T>) -> Self

Converts std::sync::Arc to loom::sync::Arc.

This is needed to create a loom::sync::Arc<T> where T: !Sized.

§Panics

If the provided Arc has copies (i.e., if it is not unique).

§Examples

While std::sync::Arc with T: !Sized can be created by coercing an std::sync::Arc with a sized value:

let sized: std::sync::Arc<[u8; 3]> = std::sync::Arc::new([1, 2, 3]);
let _unsized: std::sync::Arc<[u8]> = sized; // coercion

loom::sync::Arc can’t be created in the same way:

use loom::sync::Arc;

let sized: Arc<[u8; 3]> = Arc::new([1, 2, 3]);
let _unsized: Arc<[u8]> = sized; // error: mismatched types

This is because std::sync::Arc uses an unstable trait called CoerceUnsized that loom can’t use. To create loom::sync::Arc with an unsized inner value first create a std::sync::Arc of an appropriate type and then use this method:

use loom::sync::Arc;

let std: std::sync::Arc<[u8]> = std::sync::Arc::new([1, 2, 3]);
let loom: Arc<[u8]> = Arc::from_std(std);

let std: std::sync::Arc<dyn Send + Sync> = std::sync::Arc::new([1, 2, 3]);
let loom: Arc<dyn Send + Sync> = Arc::from_std(std);

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pub fn strong_count(this: &Self) -> usize

Gets the number of strong (Arc) pointers to this value.

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pub unsafe fn increment_strong_count(ptr: *const T)

Increments the strong reference count on the Arc<T> associated with the provided pointer by one.

§Safety

The pointer must have been obtained through Arc::into_raw, and the associated Arc instance must be valid (i.e. the strong count must be at least 1) for the duration of this method.

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pub unsafe fn decrement_strong_count(ptr: *const T)

Decrements the strong reference count on the Arc<T> associated with the provided pointer by one.

§Safety

The pointer must have been obtained through Arc::into_raw, and the associated Arc instance must be valid (i.e. the strong count must be at least 1) when invoking this method. This method can be used to release the final Arc and backing storage, but should not be called after the final Arc has been released.

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pub fn get_mut(this: &mut Self) -> Option<&mut T>

Returns a mutable reference to the inner value, if there are no other Arc pointers to the same value.

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pub fn ptr_eq(this: &Self, other: &Self) -> bool

Returns true if the two Arcs point to the same value (not just values that compare as equal).

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pub fn into_raw(this: Self) -> *const T

Consumes the Arc, returning the wrapped pointer.

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pub fn as_ptr(this: &Self) -> *const T

Provides a raw pointer to the data.

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pub unsafe fn from_raw(ptr: *const T) -> Self

Constructs an Arc from a raw pointer.

§Safety

The raw pointer must have been previously returned by a call to Arc::into_raw where U must have the same size and alignment as T. This is trivially true if U is T. Note that if U is not T but has the same size and alignment, this is basically like transmuting references of different types. See mem::transmute for more information on what restrictions apply in this case.

The user of from_raw has to make sure a specific value of T is only dropped once.

This function is unsafe because improper use may lead to memory unsafety, even if the returned Arc<T> is never accessed.