Struct Arc 

pub struct Arc<T, A = Global>
where
    A: Allocator,
    T: ?Sized,
{ /* private fields */ }

A thread-safe reference-counting pointer. ‘Arc’ stands for ‘Atomically Reference Counted’.

The type Arc<T> provides shared ownership of a value of type T, allocated in the heap. Invoking clone on Arc produces a new Arc instance, which points to the same allocation on the heap as the source Arc, while increasing a reference count. When the last Arc pointer to a given allocation is destroyed, the value stored in that allocation (often referred to as “inner value”) is also dropped.

Shared references in Rust disallow mutation by default, and Arc is no exception: you cannot generally obtain a mutable reference to something inside an Arc. If you do need to mutate through an Arc, you have several options:

1. Use interior mutability with synchronization primitives like Mutex, RwLock, or one of the Atomic types.

2. Use clone-on-write semantics with Arc::make_mut which provides efficient mutation without requiring interior mutability. This approach clones the data only when needed (when there are multiple references) and can be more efficient when mutations are infrequent.

3. Use Arc::get_mut when you know your Arc is not shared (has a reference count of 1), which provides direct mutable access to the inner value without any cloning.

use std::sync::Arc;

let mut data = Arc::new(vec![1, 2, 3]);

// This will clone the vector only if there are other references to it
Arc::make_mut(&mut data).push(4);

assert_eq!(*data, vec![1, 2, 3, 4]);

Note: This type is only available on platforms that support atomic loads and stores of pointers, which includes all platforms that support the std crate but not all those which only support alloc. This may be detected at compile time using #[cfg(target_has_atomic = "ptr")].

Thread Safety

Unlike Rc<T>, Arc<T> uses atomic operations for its reference counting. This means that it is thread-safe. The disadvantage is that atomic operations are more expensive than ordinary memory accesses. If you are not sharing reference-counted allocations between threads, consider using Rc<T> for lower overhead. Rc<T> is a safe default, because the compiler will catch any attempt to send an Rc<T> between threads. However, a library might choose Arc<T> in order to give library consumers more flexibility.

Arc<T> will implement Send and Sync as long as the T implements Send and Sync. Why can’t you put a non-thread-safe type T in an Arc<T> to make it thread-safe? This may be a bit counter-intuitive at first: after all, isn’t the point of Arc<T> thread safety? The key is this: Arc<T> makes it thread safe to have multiple ownership of the same data, but it doesn’t add thread safety to its data. Consider Arc<RefCell<T>>. RefCell<T> isn’t Sync, and if Arc<T> was always Send, Arc<RefCell<T>> would be as well. But then we’d have a problem: RefCell<T> is not thread safe; it keeps track of the borrowing count using non-atomic operations.

In the end, this means that you may need to pair Arc<T> with some sort of std::sync type, usually Mutex<T>.

Breaking cycles with Weak

The downgrade method can be used to create a non-owning Weak pointer. A Weak pointer can be upgraded to an Arc, but this will return None if the value stored in the allocation has already been dropped. In other words, Weak pointers do not keep the value inside the allocation alive; however, they do keep the allocation (the backing store for the value) alive.

A cycle between Arc pointers will never be deallocated. For this reason, Weak is used to break cycles. For example, a tree could have strong Arc pointers from parent nodes to children, and Weak pointers from children back to their parents.

Cloning references

Creating a new reference from an existing reference-counted pointer is done using the Clone trait implemented for Arc<T> and Weak<T>.

use std::sync::Arc;
let foo = Arc::new(vec![1.0, 2.0, 3.0]);
// The two syntaxes below are equivalent.
let a = foo.clone();
let b = Arc::clone(&foo);
// a, b, and foo are all Arcs that point to the same memory location

Deref behavior

Arc<T> automatically dereferences to T (via the Deref trait), so you can call T’s methods on a value of type Arc<T>. To avoid name clashes with T’s methods, the methods of Arc<T> itself are associated functions, called using fully qualified syntax:

use std::sync::Arc;

let my_arc = Arc::new(());
let my_weak = Arc::downgrade(&my_arc);

Arc<T>’s implementations of traits like Clone may also be called using fully qualified syntax. Some people prefer to use fully qualified syntax, while others prefer using method-call syntax.

use std::sync::Arc;

let arc = Arc::new(());
// Method-call syntax
let arc2 = arc.clone();
// Fully qualified syntax
let arc3 = Arc::clone(&arc);

Weak<T> does not auto-dereference to T, because the inner value may have already been dropped.

Examples

Sharing some immutable data between threads:

use std::sync::Arc;
use std::thread;

let five = Arc::new(5);

for _ in 0..10 {
    let five = Arc::clone(&five);

    thread::spawn(move || {
        println!("{five:?}");
    });
}

Sharing a mutable AtomicUsize:

use std::sync::Arc;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::thread;

let val = Arc::new(AtomicUsize::new(5));

for _ in 0..10 {
    let val = Arc::clone(&val);

    thread::spawn(move || {
        let v = val.fetch_add(1, Ordering::Relaxed);
        println!("{v:?}");
    });
}

See the rc documentation for more examples of reference counting in general.

Implementations

impl<T> Arc<T>

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new Arc<T>.

Examples

use std::sync::Arc;

let five = Arc::new(5);

pub fn new_cyclic<F>(data_fn: F) -> Arc<T>

where F: FnOnce(&Weak<T>) -> T,

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new Arc<T> while giving you a Weak<T> to the allocation, to allow you to construct a T which holds a weak pointer to itself.

Generally, a structure circularly referencing itself, either directly or indirectly, should not hold a strong reference to itself to prevent a memory leak. Using this function, you get access to the weak pointer during the initialization of T, before the Arc<T> is created, such that you can clone and store it inside the T.

new_cyclic first allocates the managed allocation for the Arc<T>, then calls your closure, giving it a Weak<T> to this allocation, and only afterwards completes the construction of the Arc<T> by placing the T returned from your closure into the allocation.

Since the new Arc<T> is not fully-constructed until Arc<T>::new_cyclic returns, calling upgrade on the weak reference inside your closure will fail and result in a None value.

Panics

If data_fn panics, the panic is propagated to the caller, and the temporary Weak<T> is dropped normally.

Example

use std::sync::{Arc, Weak};

struct Gadget {
    me: Weak<Gadget>,
}

impl Gadget {
    /// Constructs a reference counted Gadget.
    fn new() -> Arc<Self> {
        // `me` is a `Weak<Gadget>` pointing at the new allocation of the
        // `Arc` we're constructing.
        Arc::new_cyclic(|me| {
            // Create the actual struct here.
            Gadget { me: me.clone() }
        })
    }

    /// Returns a reference counted pointer to Self.
    fn me(&self) -> Arc<Self> {
        self.me.upgrade().unwrap()
    }
}

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new Arc with uninitialized contents.

Examples

use std::sync::Arc;

let mut five = Arc::<u32>::new_uninit();

// Deferred initialization:
Arc::get_mut(&mut five).unwrap().write(5);

let five = unsafe { five.assume_init() };

assert_eq!(*five, 5)

pub fn new_zeroed() -> Arc<MaybeUninit<T>>

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new Arc with uninitialized contents, with the memory being filled with 0 bytes.

See MaybeUninit::zeroed for examples of correct and incorrect usage of this method.

Examples

use std::sync::Arc;

let zero = Arc::<u32>::new_zeroed();
let zero = unsafe { zero.assume_init() };

assert_eq!(*zero, 0)

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new Pin<Arc<T>>. If T does not implement Unpin, then data will be pinned in memory and unable to be moved.

pub fn try_pin(data: T) -> Result<Pin<Arc<T>>, AllocError>

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

Available on crate features mcp and tools only.

Constructs a new Pin<Arc<T>>, return an error if allocation fails.

pub fn try_new(data: T) -> Result<Arc<T>, AllocError>

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

Available on crate features mcp and tools only.

Constructs a new Arc<T>, returning an error if allocation fails.

Examples

#![feature(allocator_api)]
use std::sync::Arc;

let five = Arc::try_new(5)?;

pub fn try_new_uninit() -> Result<Arc<MaybeUninit<T>>, AllocError>

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

Available on crate features mcp and tools only.

Constructs a new Arc with uninitialized contents, returning an error if allocation fails.

Examples

#![feature(allocator_api)]

use std::sync::Arc;

let mut five = Arc::<u32>::try_new_uninit()?;

// Deferred initialization:
Arc::get_mut(&mut five).unwrap().write(5);

let five = unsafe { five.assume_init() };

assert_eq!(*five, 5);

pub fn try_new_zeroed() -> Result<Arc<MaybeUninit<T>>, AllocError>

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

Available on crate features mcp and tools only.

Constructs a new Arc with uninitialized contents, with the memory being filled with 0 bytes, returning an error if allocation fails.

See MaybeUninit::zeroed for examples of correct and incorrect usage of this method.

Examples

#![feature( allocator_api)]

use std::sync::Arc;

let zero = Arc::<u32>::try_new_zeroed()?;
let zero = unsafe { zero.assume_init() };

assert_eq!(*zero, 0);

pub fn map<U>(this: Arc<T>, f: impl FnOnce(&T) -> U) -> Arc<U>

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Maps the value in an Arc, reusing the allocation if possible.

f is called on a reference to the value in the Arc, and the result is returned, also in an Arc.

Note: this is an associated function, which means that you have to call it as Arc::map(a, f) instead of r.map(a). This is so that there is no conflict with a method on the inner type.

Examples

#![feature(smart_pointer_try_map)]

use std::sync::Arc;

let r = Arc::new(7);
let new = Arc::map(r, |i| i + 7);
assert_eq!(*new, 14);

pub fn try_map<R>( this: Arc<T>, f: impl FnOnce(&T) -> R, ) -> <<R as Try>::Residual as Residual<Arc<<R as Try>::Output>>>::TryType

where R: Try, <R as Try>::Residual: Residual<Arc<<R as Try>::Output>>,

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Attempts to map the value in an Arc, reusing the allocation if possible.

f is called on a reference to the value in the Arc, and if the operation succeeds, the result is returned, also in an Arc.

Note: this is an associated function, which means that you have to call it as Arc::try_map(a, f) instead of a.try_map(f). This is so that there is no conflict with a method on the inner type.

Examples

#![feature(smart_pointer_try_map)]

use std::sync::Arc;

let b = Arc::new(7);
let new = Arc::try_map(b, |&i| u32::try_from(i)).unwrap();
assert_eq!(*new, 7);

impl<T, A> Arc<T, A>

where A: Allocator,

pub fn new_in(data: T, alloc: A) -> Arc<T, A>

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new Arc<T> in the provided allocator.

Examples

#![feature(allocator_api)]

use std::sync::Arc;
use std::alloc::System;

let five = Arc::new_in(5, System);

pub fn new_uninit_in(alloc: A) -> Arc<MaybeUninit<T>, A>

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new Arc with uninitialized contents in the provided allocator.

Examples

#![feature(get_mut_unchecked)]
#![feature(allocator_api)]

use std::sync::Arc;
use std::alloc::System;

let mut five = Arc::<u32, _>::new_uninit_in(System);

let five = unsafe {
    // Deferred initialization:
    Arc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);

    five.assume_init()
};

assert_eq!(*five, 5)

pub fn new_zeroed_in(alloc: A) -> Arc<MaybeUninit<T>, A>

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new Arc with uninitialized contents, with the memory being filled with 0 bytes, in the provided allocator.

See MaybeUninit::zeroed for examples of correct and incorrect usage of this method.

Examples

#![feature(allocator_api)]

use std::sync::Arc;
use std::alloc::System;

let zero = Arc::<u32, _>::new_zeroed_in(System);
let zero = unsafe { zero.assume_init() };

assert_eq!(*zero, 0)

pub fn new_cyclic_in<F>(data_fn: F, alloc: A) -> Arc<T, A>

where F: FnOnce(&Weak<T, A>) -> T,

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new Arc<T, A> in the given allocator while giving you a Weak<T, A> to the allocation, to allow you to construct a T which holds a weak pointer to itself.

Generally, a structure circularly referencing itself, either directly or indirectly, should not hold a strong reference to itself to prevent a memory leak. Using this function, you get access to the weak pointer during the initialization of T, before the Arc<T, A> is created, such that you can clone and store it inside the T.

new_cyclic_in first allocates the managed allocation for the Arc<T, A>, then calls your closure, giving it a Weak<T, A> to this allocation, and only afterwards completes the construction of the Arc<T, A> by placing the T returned from your closure into the allocation.

Since the new Arc<T, A> is not fully-constructed until Arc<T, A>::new_cyclic_in returns, calling upgrade on the weak reference inside your closure will fail and result in a None value.

Panics

If data_fn panics, the panic is propagated to the caller, and the temporary Weak<T> is dropped normally.

Example

See new_cyclic

pub fn pin_in(data: T, alloc: A) -> Pin<Arc<T, A>>

where A: 'static,

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new Pin<Arc<T, A>> in the provided allocator. If T does not implement Unpin, then data will be pinned in memory and unable to be moved.

pub fn try_pin_in(data: T, alloc: A) -> Result<Pin<Arc<T, A>>, AllocError>

where A: 'static,

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

Available on crate features mcp and tools only.

Constructs a new Pin<Arc<T, A>> in the provided allocator, return an error if allocation fails.

pub fn try_new_in(data: T, alloc: A) -> Result<Arc<T, A>, AllocError>

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

Available on crate features mcp and tools only.

Constructs a new Arc<T, A> in the provided allocator, returning an error if allocation fails.

Examples

#![feature(allocator_api)]

use std::sync::Arc;
use std::alloc::System;

let five = Arc::try_new_in(5, System)?;

pub fn try_new_uninit_in(alloc: A) -> Result<Arc<MaybeUninit<T>, A>, AllocError>

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

Available on crate features mcp and tools only.

Constructs a new Arc with uninitialized contents, in the provided allocator, returning an error if allocation fails.

Examples

#![feature(allocator_api)]
#![feature(get_mut_unchecked)]

use std::sync::Arc;
use std::alloc::System;

let mut five = Arc::<u32, _>::try_new_uninit_in(System)?;

let five = unsafe {
    // Deferred initialization:
    Arc::get_mut_unchecked(&mut five).as_mut_ptr().write(5);

    five.assume_init()
};

assert_eq!(*five, 5);

pub fn try_new_zeroed_in(alloc: A) -> Result<Arc<MaybeUninit<T>, A>, AllocError>

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

Available on crate features mcp and tools only.

Constructs a new Arc with uninitialized contents, with the memory being filled with 0 bytes, in the provided allocator, returning an error if allocation fails.

See MaybeUninit::zeroed for examples of correct and incorrect usage of this method.

Examples

#![feature(allocator_api)]

use std::sync::Arc;
use std::alloc::System;

let zero = Arc::<u32, _>::try_new_zeroed_in(System)?;
let zero = unsafe { zero.assume_init() };

assert_eq!(*zero, 0);

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

Available on crate features mcp and tools only.

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

Otherwise, an Err is returned with the same Arc that was passed in.

This will succeed even if there are outstanding weak references.

It is strongly recommended to use Arc::into_inner instead if you don’t keep the Arc in the Err case. Immediately dropping the Err-value, as the expression Arc::try_unwrap(this).ok() does, can cause the strong count to drop to zero and the inner value of the Arc to be dropped. For instance, if two threads execute such an expression in parallel, there is a race condition without the possibility of unsafety: The threads could first both check whether they own the last instance in Arc::try_unwrap, determine that they both do not, and then both discard and drop their instance in the call to ok. In this scenario, the value inside the Arc is safely destroyed by exactly one of the threads, but neither thread will ever be able to use the value.

Examples

use std::sync::Arc;

let x = Arc::new(3);
assert_eq!(Arc::try_unwrap(x), Ok(3));

let x = Arc::new(4);
let _y = Arc::clone(&x);
assert_eq!(*Arc::try_unwrap(x).unwrap_err(), 4);

pub fn into_inner(this: Arc<T, A>) -> Option<T>

Available on crate features mcp and tools only.

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

Otherwise, None is returned and the Arc is dropped.

This will succeed even if there are outstanding weak references.

If Arc::into_inner is called on every clone of this Arc, it is guaranteed that exactly one of the calls returns the inner value. This means in particular that the inner value is not dropped.

Arc::try_unwrap is conceptually similar to Arc::into_inner, but it is meant for different use-cases. If used as a direct replacement for Arc::into_inner anyway, such as with the expression Arc::try_unwrap(this).ok(), then it does not give the same guarantee as described in the previous paragraph. For more information, see the examples below and read the documentation of Arc::try_unwrap.

Examples

Minimal example demonstrating the guarantee that Arc::into_inner gives.

use std::sync::Arc;

let x = Arc::new(3);
let y = Arc::clone(&x);

// Two threads calling `Arc::into_inner` on both clones of an `Arc`:
let x_thread = std::thread::spawn(|| Arc::into_inner(x));
let y_thread = std::thread::spawn(|| Arc::into_inner(y));

let x_inner_value = x_thread.join().unwrap();
let y_inner_value = y_thread.join().unwrap();

// One of the threads is guaranteed to receive the inner value:
assert!(matches!(
    (x_inner_value, y_inner_value),
    (None, Some(3)) | (Some(3), None)
));
// The result could also be `(None, None)` if the threads called
// `Arc::try_unwrap(x).ok()` and `Arc::try_unwrap(y).ok()` instead.

A more practical example demonstrating the need for Arc::into_inner:

use std::sync::Arc;

// Definition of a simple singly linked list using `Arc`:
#[derive(Clone)]
struct LinkedList<T>(Option<Arc<Node<T>>>);
struct Node<T>(T, Option<Arc<Node<T>>>);

// Dropping a long `LinkedList<T>` relying on the destructor of `Arc`
// can cause a stack overflow. To prevent this, we can provide a
// manual `Drop` implementation that does the destruction in a loop:
impl<T> Drop for LinkedList<T> {
    fn drop(&mut self) {
        let mut link = self.0.take();
        while let Some(arc_node) = link.take() {
            if let Some(Node(_value, next)) = Arc::into_inner(arc_node) {
                link = next;
            }
        }
    }
}

// Implementation of `new` and `push` omitted
impl<T> LinkedList<T> {
    /* ... */
}

// The following code could have still caused a stack overflow
// despite the manual `Drop` impl if that `Drop` impl had used
// `Arc::try_unwrap(arc).ok()` instead of `Arc::into_inner(arc)`.

// Create a long list and clone it
let mut x = LinkedList::new();
let size = 100000;
for i in 0..size {
    x.push(i); // Adds i to the front of x
}
let y = x.clone();

// Drop the clones in parallel
let x_thread = std::thread::spawn(|| drop(x));
let y_thread = std::thread::spawn(|| drop(y));
x_thread.join().unwrap();
y_thread.join().unwrap();

impl<T> Arc<[T]>

pub fn new_uninit_slice(len: usize) -> Arc<[MaybeUninit<T>]>

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new atomically reference-counted slice with uninitialized contents.

Examples

use std::sync::Arc;

let mut values = Arc::<[u32]>::new_uninit_slice(3);

// Deferred initialization:
let data = Arc::get_mut(&mut values).unwrap();
data[0].write(1);
data[1].write(2);
data[2].write(3);

let values = unsafe { values.assume_init() };

assert_eq!(*values, [1, 2, 3])

pub fn new_zeroed_slice(len: usize) -> Arc<[MaybeUninit<T>]>

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new atomically reference-counted slice with uninitialized contents, with the memory being filled with 0 bytes.

See MaybeUninit::zeroed for examples of correct and incorrect usage of this method.

Examples

use std::sync::Arc;

let values = Arc::<[u32]>::new_zeroed_slice(3);
let values = unsafe { values.assume_init() };

assert_eq!(*values, [0, 0, 0])

impl<T, A> Arc<[T], A>

where A: Allocator,

pub fn new_uninit_slice_in(len: usize, alloc: A) -> Arc<[MaybeUninit<T>], A>

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new atomically reference-counted slice with uninitialized contents in the provided allocator.

Examples

#![feature(get_mut_unchecked)]
#![feature(allocator_api)]

use std::sync::Arc;
use std::alloc::System;

let mut values = Arc::<[u32], _>::new_uninit_slice_in(3, System);

let values = unsafe {
    // Deferred initialization:
    Arc::get_mut_unchecked(&mut values)[0].as_mut_ptr().write(1);
    Arc::get_mut_unchecked(&mut values)[1].as_mut_ptr().write(2);
    Arc::get_mut_unchecked(&mut values)[2].as_mut_ptr().write(3);

    values.assume_init()
};

assert_eq!(*values, [1, 2, 3])

pub fn new_zeroed_slice_in(len: usize, alloc: A) -> Arc<[MaybeUninit<T>], A>

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new atomically reference-counted slice with uninitialized contents, with the memory being filled with 0 bytes, in the provided allocator.

See MaybeUninit::zeroed for examples of correct and incorrect usage of this method.

Examples

#![feature(allocator_api)]

use std::sync::Arc;
use std::alloc::System;

let values = Arc::<[u32], _>::new_zeroed_slice_in(3, System);
let values = unsafe { values.assume_init() };

assert_eq!(*values, [0, 0, 0])

pub fn into_array<const N: usize>(self) -> Result<Arc<[T; N], A>, Arc<[T], A>>

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

Available on crate features mcp and tools only.

Converts the reference-counted slice into a reference-counted array.

This operation does not reallocate; the underlying array of the slice is simply reinterpreted as an array type.

Errors

Returns the original Arc<[T]> in the Err variant if self.len() does not equal N.

Examples

#![feature(alloc_slice_into_array)]
use std::sync::Arc;

let arc_slice: Arc<[i32]> = Arc::new([1, 2, 3]);

let arc_array: Arc<[i32; 3]> = arc_slice.into_array().unwrap();

impl<T, A> Arc<MaybeUninit<T>, A>

where A: Allocator,

pub unsafe fn assume_init(self) -> Arc<T, A>

Available on crate features mcp and tools only.

Converts to Arc<T>.

Safety

As with MaybeUninit::assume_init, it is up to the caller to guarantee that the inner value really is in an initialized state. Calling this when the content is not yet fully initialized causes immediate undefined behavior.

Examples

use std::sync::Arc;

let mut five = Arc::<u32>::new_uninit();

// Deferred initialization:
Arc::get_mut(&mut five).unwrap().write(5);

let five = unsafe { five.assume_init() };

assert_eq!(*five, 5)

impl<T> Arc<T>

where T: CloneToUninit + ?Sized,

pub fn clone_from_ref(value: &T) -> Arc<T>

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new Arc<T> with a clone of value.

Examples

#![feature(clone_from_ref)]
use std::sync::Arc;

let hello: Arc<str> = Arc::clone_from_ref("hello");

pub fn try_clone_from_ref(value: &T) -> Result<Arc<T>, AllocError>

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

Available on crate features mcp and tools only.

Constructs a new Arc<T> with a clone of value, returning an error if allocation fails

Examples

#![feature(clone_from_ref)]
#![feature(allocator_api)]
use std::sync::Arc;

let hello: Arc<str> = Arc::try_clone_from_ref("hello")?;

impl<T, A> Arc<T, A>

where T: CloneToUninit + ?Sized, A: Allocator,

pub fn clone_from_ref_in(value: &T, alloc: A) -> Arc<T, A>

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

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Constructs a new Arc<T> with a clone of value in the provided allocator.

Examples

#![feature(clone_from_ref)]
#![feature(allocator_api)]
use std::sync::Arc;
use std::alloc::System;

let hello: Arc<str, System> = Arc::clone_from_ref_in("hello", System);

pub fn try_clone_from_ref_in( value: &T, alloc: A, ) -> Result<Arc<T, A>, AllocError>

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

Available on crate features mcp and tools only.

Constructs a new Arc<T> with a clone of value in the provided allocator, returning an error if allocation fails

Examples

#![feature(clone_from_ref)]
#![feature(allocator_api)]
use std::sync::Arc;
use std::alloc::System;

let hello: Arc<str, System> = Arc::try_clone_from_ref_in("hello", System)?;

impl<T, A> Arc<[MaybeUninit<T>], A>

where A: Allocator,

pub unsafe fn assume_init(self) -> Arc<[T], A>

Available on crate features mcp and tools only.

Converts to Arc<[T]>.

Safety

As with MaybeUninit::assume_init, it is up to the caller to guarantee that the inner value really is in an initialized state. Calling this when the content is not yet fully initialized causes immediate undefined behavior.

Examples

use std::sync::Arc;

let mut values = Arc::<[u32]>::new_uninit_slice(3);

// Deferred initialization:
let data = Arc::get_mut(&mut values).unwrap();
data[0].write(1);
data[1].write(2);
data[2].write(3);

let values = unsafe { values.assume_init() };

assert_eq!(*values, [1, 2, 3])

impl<T> Arc<T>

where T: ?Sized,

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

Available on crate features mcp and tools only.

Constructs an Arc<T> from a raw pointer.

The raw pointer must have been previously returned by a call to Arc<U>::into_raw or Arc<U>::into_raw_with_allocator.

Safety

• Creating a Arc<T> from a pointer other than one returned from Arc<U>::into_raw or Arc<U>::into_raw_with_allocator is undefined behavior.
• If U is sized, it must have the same size and alignment as T. This is trivially true if U is T.
• If U is unsized, its data pointer must have the same size and alignment as T. This is trivially true if Arc<U> was constructed through Arc<T> and then converted to Arc<U> through an unsized coercion.
• Note that if U or U’s data pointer 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 raw pointer must point to a block of memory allocated by the global allocator.
• 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.

Examples

use std::sync::Arc;

let x = Arc::new("hello".to_owned());
let x_ptr = Arc::into_raw(x);

unsafe {
    // Convert back to an `Arc` to prevent leak.
    let x = Arc::from_raw(x_ptr);
    assert_eq!(&*x, "hello");

    // Further calls to `Arc::from_raw(x_ptr)` would be memory-unsafe.
}

// The memory was freed when `x` went out of scope above, so `x_ptr` is now dangling!

Convert a slice back into its original array:

use std::sync::Arc;

let x: Arc<[u32]> = Arc::new([1, 2, 3]);
let x_ptr: *const [u32] = Arc::into_raw(x);

unsafe {
    let x: Arc<[u32; 3]> = Arc::from_raw(x_ptr.cast::<[u32; 3]>());
    assert_eq!(&*x, &[1, 2, 3]);
}

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

Available on crate features mcp and tools only.

Consumes the Arc, returning the wrapped pointer.

To avoid a memory leak the pointer must be converted back to an Arc using Arc::from_raw.

Examples

use std::sync::Arc;

let x = Arc::new("hello".to_owned());
let x_ptr = Arc::into_raw(x);
assert_eq!(unsafe { &*x_ptr }, "hello");

pub unsafe fn increment_strong_count(ptr: *const T)

Available on crate features mcp and tools only.

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 must satisfy the same layout requirements specified in Arc::from_raw_in. The associated Arc instance must be valid (i.e. the strong count must be at least 1) for the duration of this method, and ptr must point to a block of memory allocated by the global allocator.

Examples

use std::sync::Arc;

let five = Arc::new(5);

unsafe {
    let ptr = Arc::into_raw(five);
    Arc::increment_strong_count(ptr);

    // This assertion is deterministic because we haven't shared
    // the `Arc` between threads.
    let five = Arc::from_raw(ptr);
    assert_eq!(2, Arc::strong_count(&five));
}

pub unsafe fn decrement_strong_count(ptr: *const T)

Available on crate features mcp and tools only.

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 must satisfy the same layout requirements specified in Arc::from_raw_in. The associated Arc instance must be valid (i.e. the strong count must be at least 1) when invoking this method, and ptr must point to a block of memory allocated by the global allocator. 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.

Examples

use std::sync::Arc;

let five = Arc::new(5);

unsafe {
    let ptr = Arc::into_raw(five);
    Arc::increment_strong_count(ptr);

    // Those assertions are deterministic because we haven't shared
    // the `Arc` between threads.
    let five = Arc::from_raw(ptr);
    assert_eq!(2, Arc::strong_count(&five));
    Arc::decrement_strong_count(ptr);
    assert_eq!(1, Arc::strong_count(&five));
}

impl<T, A> Arc<T, A>

where A: Allocator, T: ?Sized,

pub fn allocator(this: &Arc<T, A>) -> &A

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

Available on crate features mcp and tools only.

Returns a reference to the underlying allocator.

Note: this is an associated function, which means that you have to call it as Arc::allocator(&a) instead of a.allocator(). This is so that there is no conflict with a method on the inner type.

pub fn into_raw_with_allocator(this: Arc<T, A>) -> (*const T, A)

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

Available on crate features mcp and tools only.

Consumes the Arc, returning the wrapped pointer and allocator.

To avoid a memory leak the pointer must be converted back to an Arc using Arc::from_raw_in.

Examples

#![feature(allocator_api)]
use std::sync::Arc;
use std::alloc::System;

let x = Arc::new_in("hello".to_owned(), System);
let (ptr, alloc) = Arc::into_raw_with_allocator(x);
assert_eq!(unsafe { &*ptr }, "hello");
let x = unsafe { Arc::from_raw_in(ptr, alloc) };
assert_eq!(&*x, "hello");

pub fn as_ptr(this: &Arc<T, A>) -> *const T

Available on crate features mcp and tools only.

Provides a raw pointer to the data.

The counts are not affected in any way and the Arc is not consumed. The pointer is valid for as long as there are strong counts in the Arc.

Examples

use std::sync::Arc;

let x = Arc::new("hello".to_owned());
let y = Arc::clone(&x);
let x_ptr = Arc::as_ptr(&x);
assert_eq!(x_ptr, Arc::as_ptr(&y));
assert_eq!(unsafe { &*x_ptr }, "hello");

pub unsafe fn from_raw_in(ptr: *const T, alloc: A) -> Arc<T, A>

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

Available on crate features mcp and tools only.

Constructs an Arc<T, A> from a raw pointer.

The raw pointer must have been previously returned by a call to Arc<U, A>::into_raw or Arc<U, A>::into_raw_with_allocator.

Safety

• Creating a Arc<T, A> from a pointer other than one returned from Arc<U, A>::into_raw or Arc<U, A>::into_raw_with_allocator is undefined behavior.
• If U is sized, it must have the same size and alignment as T. This is trivially true if U is T.
• If U is unsized, its data pointer must have the same size and alignment as T. This is trivially true if Arc<U, A> was constructed through Arc<T, A> and then converted to Arc<U, A> through an unsized coercion.
• Note that if U or U’s data pointer 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 raw pointer must point to a block of memory allocated by alloc
• 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.

Examples

#![feature(allocator_api)]

use std::sync::Arc;
use std::alloc::System;

let x = Arc::new_in("hello".to_owned(), System);
let (x_ptr, alloc) = Arc::into_raw_with_allocator(x);

unsafe {
    // Convert back to an `Arc` to prevent leak.
    let x = Arc::from_raw_in(x_ptr, System);
    assert_eq!(&*x, "hello");

    // Further calls to `Arc::from_raw(x_ptr)` would be memory-unsafe.
}

// The memory was freed when `x` went out of scope above, so `x_ptr` is now dangling!

Convert a slice back into its original array:

#![feature(allocator_api)]

use std::sync::Arc;
use std::alloc::System;

let x: Arc<[u32], _> = Arc::new_in([1, 2, 3], System);
let x_ptr: *const [u32] = Arc::into_raw_with_allocator(x).0;

unsafe {
    let x: Arc<[u32; 3], _> = Arc::from_raw_in(x_ptr.cast::<[u32; 3]>(), System);
    assert_eq!(&*x, &[1, 2, 3]);
}

pub fn downgrade(this: &Arc<T, A>) -> Weak<T, A>

where A: Clone,

Available on crate features mcp and tools only.

Creates a new Weak pointer to this allocation.

Examples

use std::sync::Arc;

let five = Arc::new(5);

let weak_five = Arc::downgrade(&five);

pub fn weak_count(this: &Arc<T, A>) -> usize

Available on crate features mcp and tools only.

Gets the number of Weak pointers to this allocation.

Safety

This method by itself is safe, but using it correctly requires extra care. Another thread can change the weak count at any time, including potentially between calling this method and acting on the result.

Examples

use std::sync::Arc;

let five = Arc::new(5);
let _weak_five = Arc::downgrade(&five);

// This assertion is deterministic because we haven't shared
// the `Arc` or `Weak` between threads.
assert_eq!(1, Arc::weak_count(&five));

pub fn strong_count(this: &Arc<T, A>) -> usize

Available on crate features mcp and tools only.

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

Safety

This method by itself is safe, but using it correctly requires extra care. Another thread can change the strong count at any time, including potentially between calling this method and acting on the result.

Examples

use std::sync::Arc;

let five = Arc::new(5);
let _also_five = Arc::clone(&five);

// This assertion is deterministic because we haven't shared
// the `Arc` between threads.
assert_eq!(2, Arc::strong_count(&five));

pub unsafe fn increment_strong_count_in(ptr: *const T, alloc: A)

where A: Clone,

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

Available on crate features mcp and tools only.

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 must satisfy the same layout requirements specified in Arc::from_raw_in. The associated Arc instance must be valid (i.e. the strong count must be at least 1) for the duration of this method, and ptr must point to a block of memory allocated by alloc.

Examples

#![feature(allocator_api)]

use std::sync::Arc;
use std::alloc::System;

let five = Arc::new_in(5, System);

unsafe {
    let (ptr, _alloc) = Arc::into_raw_with_allocator(five);
    Arc::increment_strong_count_in(ptr, System);

    // This assertion is deterministic because we haven't shared
    // the `Arc` between threads.
    let five = Arc::from_raw_in(ptr, System);
    assert_eq!(2, Arc::strong_count(&five));
}

pub unsafe fn decrement_strong_count_in(ptr: *const T, alloc: A)

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

Available on crate features mcp and tools only.

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 must satisfy the same layout requirements specified in Arc::from_raw_in. The associated Arc instance must be valid (i.e. the strong count must be at least 1) when invoking this method, and ptr must point to a block of memory allocated by alloc. 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.

Examples

#![feature(allocator_api)]

use std::sync::Arc;
use std::alloc::System;

let five = Arc::new_in(5, System);

unsafe {
    let (ptr, _alloc) = Arc::into_raw_with_allocator(five);
    Arc::increment_strong_count_in(ptr, System);

    // Those assertions are deterministic because we haven't shared
    // the `Arc` between threads.
    let five = Arc::from_raw_in(ptr, System);
    assert_eq!(2, Arc::strong_count(&five));
    Arc::decrement_strong_count_in(ptr, System);
    assert_eq!(1, Arc::strong_count(&five));
}

pub fn ptr_eq(this: &Arc<T, A>, other: &Arc<T, A>) -> bool

Available on crate features mcp and tools only.

Returns true if the two Arcs point to the same allocation in a vein similar to ptr::eq. This function ignores the metadata of dyn Trait pointers.

Examples

use std::sync::Arc;

let five = Arc::new(5);
let same_five = Arc::clone(&five);
let other_five = Arc::new(5);

assert!(Arc::ptr_eq(&five, &same_five));
assert!(!Arc::ptr_eq(&five, &other_five));

impl<T, A> Arc<T, A>

where T: CloneToUninit + ?Sized, A: Allocator + Clone,

pub fn make_mut(this: &mut Arc<T, A>) -> &mut T

Available on crate feature mcp and crate feature tools and non-no_global_oom_handling only.

Makes a mutable reference into the given Arc.

If there are other Arc pointers to the same allocation, then make_mut will clone the inner value to a new allocation to ensure unique ownership. This is also referred to as clone-on-write.

However, if there are no other Arc pointers to this allocation, but some Weak pointers, then the Weak pointers will be dissociated and the inner value will not be cloned.

See also get_mut, which will fail rather than cloning the inner value or dissociating Weak pointers.

Examples

use std::sync::Arc;

let mut data = Arc::new(5);

*Arc::make_mut(&mut data) += 1;         // Won't clone anything
let mut other_data = Arc::clone(&data); // Won't clone inner data
*Arc::make_mut(&mut data) += 1;         // Clones inner data
*Arc::make_mut(&mut data) += 1;         // Won't clone anything
*Arc::make_mut(&mut other_data) *= 2;   // Won't clone anything

// Now `data` and `other_data` point to different allocations.
assert_eq!(*data, 8);
assert_eq!(*other_data, 12);

Weak pointers will be dissociated:

use std::sync::Arc;

let mut data = Arc::new(75);
let weak = Arc::downgrade(&data);

assert!(75 == *data);
assert!(75 == *weak.upgrade().unwrap());

*Arc::make_mut(&mut data) += 1;

assert!(76 == *data);
assert!(weak.upgrade().is_none());

impl<T, A> Arc<T, A>

where T: Clone, A: Allocator,

pub fn unwrap_or_clone(this: Arc<T, A>) -> T

Available on crate features mcp and tools only.

If we have the only reference to T then unwrap it. Otherwise, clone T and return the clone.

Assuming arc_t is of type Arc<T>, this function is functionally equivalent to (*arc_t).clone(), but will avoid cloning the inner value where possible.

Examples

let inner = String::from("test");
let ptr = inner.as_ptr();

let arc = Arc::new(inner);
let inner = Arc::unwrap_or_clone(arc);
// The inner value was not cloned
assert!(ptr::eq(ptr, inner.as_ptr()));

let arc = Arc::new(inner);
let arc2 = arc.clone();
let inner = Arc::unwrap_or_clone(arc);
// Because there were 2 references, we had to clone the inner value.
assert!(!ptr::eq(ptr, inner.as_ptr()));
// `arc2` is the last reference, so when we unwrap it we get back
// the original `String`.
let inner = Arc::unwrap_or_clone(arc2);
assert!(ptr::eq(ptr, inner.as_ptr()));

impl<T, A> Arc<T, A>

where A: Allocator, T: ?Sized,

pub fn get_mut(this: &mut Arc<T, A>) -> Option<&mut T>

Available on crate features mcp and tools only.

Returns a mutable reference into the given Arc, if there are no other Arc or Weak pointers to the same allocation.

Returns None otherwise, because it is not safe to mutate a shared value.

See also make_mut, which will clone the inner value when there are other Arc pointers.

Examples

use std::sync::Arc;

let mut x = Arc::new(3);
*Arc::get_mut(&mut x).unwrap() = 4;
assert_eq!(*x, 4);

let _y = Arc::clone(&x);
assert!(Arc::get_mut(&mut x).is_none());

pub unsafe fn get_mut_unchecked(this: &mut Arc<T, A>) -> &mut T

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

Available on crate features mcp and tools only.

Returns a mutable reference into the given Arc, without any check.

See also get_mut, which is safe and does appropriate checks.

Safety

If any other Arc or Weak pointers to the same allocation exist, then they must not be dereferenced or have active borrows for the duration of the returned borrow, and their inner type must be exactly the same as the inner type of this Arc (including lifetimes). This is trivially the case if no such pointers exist, for example immediately after Arc::new.

Examples

#![feature(get_mut_unchecked)]

use std::sync::Arc;

let mut x = Arc::new(String::new());
unsafe {
    Arc::get_mut_unchecked(&mut x).push_str("foo")
}
assert_eq!(*x, "foo");

Other Arc pointers to the same allocation must be to the same type.

#![feature(get_mut_unchecked)]

use std::sync::Arc;

let x: Arc<str> = Arc::from("Hello, world!");
let mut y: Arc<[u8]> = x.clone().into();
unsafe {
    // this is Undefined Behavior, because x's inner type is str, not [u8]
    Arc::get_mut_unchecked(&mut y).fill(0xff); // 0xff is invalid in UTF-8
}
println!("{}", &*x); // Invalid UTF-8 in a str

Other Arc pointers to the same allocation must be to the exact same type, including lifetimes.

#![feature(get_mut_unchecked)]

use std::sync::Arc;

let x: Arc<&str> = Arc::new("Hello, world!");
{
    let s = String::from("Oh, no!");
    let mut y: Arc<&str> = x.clone();
    unsafe {
        // this is Undefined Behavior, because x's inner type
        // is &'long str, not &'short str
        *Arc::get_mut_unchecked(&mut y) = &s;
    }
}
println!("{}", &*x); // Use-after-free

pub fn is_unique(this: &Arc<T, A>) -> bool

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

Available on crate features mcp and tools only.

Determine whether this is the unique reference to the underlying data.

Returns true if there are no other Arc or Weak pointers to the same allocation; returns false otherwise.

If this function returns true, then is guaranteed to be safe to call get_mut_unchecked on this Arc, so long as no clones occur in between.

Examples

#![feature(arc_is_unique)]

use std::sync::Arc;

let x = Arc::new(3);
assert!(Arc::is_unique(&x));

let y = Arc::clone(&x);
assert!(!Arc::is_unique(&x));
drop(y);

// Weak references also count, because they could be upgraded at any time.
let z = Arc::downgrade(&x);
assert!(!Arc::is_unique(&x));

Pointer invalidation

This function will always return the same value as Arc::get_mut(arc).is_some(). However, unlike that operation it does not produce any mutable references to the underlying data, meaning no pointers to the data inside the Arc are invalidated by the call. Thus, the following code is valid, even though it would be UB if it used Arc::get_mut:

#![feature(arc_is_unique)]

use std::sync::Arc;

let arc = Arc::new(5);
let pointer: *const i32 = &*arc;
assert!(Arc::is_unique(&arc));
assert_eq!(unsafe { *pointer }, 5);

Atomic orderings

Concurrent drops to other Arc pointers to the same allocation will synchronize with this call - that is, this call performs an Acquire operation on the underlying strong and weak ref counts. This ensures that calling get_mut_unchecked is safe.

Note that this operation requires locking the weak ref count, so concurrent calls to downgrade may spin-loop for a short period of time.

impl<A> Arc<dyn Any + Sync + Send, A>

where A: Allocator,

pub fn downcast<T>(self) -> Result<Arc<T, A>, Arc<dyn Any + Sync + Send, A>>

where T: Any + Send + Sync,

Available on crate features mcp and tools only.

Attempts to downcast the Arc<dyn Any + Send + Sync> to a concrete type.

Examples

use std::any::Any;
use std::sync::Arc;

fn print_if_string(value: Arc<dyn Any + Send + Sync>) {
    if let Ok(string) = value.downcast::<String>() {
        println!("String ({}): {}", string.len(), string);
    }
}

let my_string = "Hello World".to_string();
print_if_string(Arc::new(my_string));
print_if_string(Arc::new(0i8));

pub unsafe fn downcast_unchecked<T>(self) -> Arc<T, A>

where T: Any + Send + Sync,

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

Available on crate features mcp and tools only.

Downcasts the Arc<dyn Any + Send + Sync> to a concrete type.

For a safe alternative see downcast.

Examples

#![feature(downcast_unchecked)]

use std::any::Any;
use std::sync::Arc;

let x: Arc<dyn Any + Send + Sync> = Arc::new(1_usize);

unsafe {
    assert_eq!(*x.downcast_unchecked::<usize>(), 1);
}

Safety

The contained value must be of type T. Calling this method with the incorrect type is undefined behavior.

Trait Implementations

impl<T, A> Allocator for Arc<T, A>

where T: Allocator + ?Sized, A: Allocator,

fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError>

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

Attempts to allocate a block of memory.

fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError>

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

Behaves like allocate, but also ensures that the returned memory is zero-initialized.

unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout)

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

Deallocates the memory referenced by ptr.

unsafe fn grow( &self, ptr: NonNull<u8>, old_layout: Layout, new_layout: Layout, ) -> Result<NonNull<[u8]>, AllocError>

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

Attempts to extend the memory block.

unsafe fn grow_zeroed( &self, ptr: NonNull<u8>, old_layout: Layout, new_layout: Layout, ) -> Result<NonNull<[u8]>, AllocError>

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

Behaves like grow, but also ensures that the new contents are set to zero before being returned.

unsafe fn shrink( &self, ptr: NonNull<u8>, old_layout: Layout, new_layout: Layout, ) -> Result<NonNull<[u8]>, AllocError>

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

Attempts to shrink the memory block.

fn by_ref(&self) -> &Self

where Self: Sized,

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

Creates a “by reference” adapter for this instance of Allocator.

impl<T> AsBacktrace for Arc<T>

where T: AsBacktrace,

Available on crate feature std, or target_has_atomic=ptr and crate feature rust_1_61 only.

fn as_backtrace(&self) -> Option<&Backtrace>

Retrieve the optional backtrace

impl<T> AsFd for Arc<T>

where T: AsFd + ?Sized,

This impl allows implementing traits that require AsFd on Arc.

use std::net::UdpSocket;
use std::sync::Arc;

trait MyTrait: AsFd {}
impl MyTrait for Arc<UdpSocket> {}
impl MyTrait for Box<UdpSocket> {}

fn as_fd(&self) -> BorrowedFd<'_>

Borrows the file descriptor.

impl<T> AsRawFd for Arc<T>

where T: AsRawFd,

This impl allows implementing traits that require AsRawFd on Arc.

use std::net::UdpSocket;
use std::sync::Arc;
trait MyTrait: AsRawFd {
}
impl MyTrait for Arc<UdpSocket> {}
impl MyTrait for Box<UdpSocket> {}

fn as_raw_fd(&self) -> i32

Extracts the raw file descriptor.

impl<T, A> AsRef<T> for Arc<T, A>

where A: Allocator, T: ?Sized,

fn as_ref(&self) -> &T

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

impl<T, A> Borrow<T> for Arc<T, A>

where A: Allocator, T: ?Sized,

fn borrow(&self) -> &T

Immutably borrows from an owned value.

impl<T> Bos<T> for Arc<T>

where T: ?Sized,

Available on target_has_atomic=ptr and non-no_rc and non-no_sync only.

type Ref<'this> = &'this T where Arc<T>: 'this

The resulting reference type. May only be &T.

fn borrow_or_share(this: &Arc<T>) -> <Arc<T> as Bos<T>>::Ref<'_>

Borrows from *this or from behind a reference it holds, returning a reference of type Self::Ref.

impl<T> ClientHandler for Arc<T>

where T: ClientHandler,

fn ping( &self, context: RequestContext<RoleClient>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

fn create_message( &self, params: CreateMessageRequestParams, context: RequestContext<RoleClient>, ) -> impl Future<Output = Result<CreateMessageResult, ErrorData>> + MaybeSendFuture

fn list_roots( &self, context: RequestContext<RoleClient>, ) -> impl Future<Output = Result<ListRootsResult, ErrorData>> + MaybeSendFuture

fn create_elicitation( &self, request: ElicitRequestParams, context: RequestContext<RoleClient>, ) -> impl Future<Output = Result<ElicitResult, ErrorData>> + MaybeSendFuture

Handle an elicitation request from a server asking for user input.

fn on_custom_request( &self, request: CustomRequest, context: RequestContext<RoleClient>, ) -> impl Future<Output = Result<CustomResult, ErrorData>> + MaybeSendFuture

fn on_cancelled( &self, params: CancelledNotificationParam, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_progress( &self, params: ProgressNotificationParam, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_logging_message( &self, params: LoggingMessageNotificationParam, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_resource_updated( &self, params: ResourceUpdatedNotificationParam, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_resource_list_changed( &self, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_tool_list_changed( &self, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_prompt_list_changed( &self, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_subscriptions_acknowledged( &self, params: SubscriptionsAcknowledgedNotificationParams, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_task_status( &self, params: TaskStatusNotificationParams, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_custom_notification( &self, notification: CustomNotification, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn get_info(&self) -> InitializeRequestParams

impl<T, A> Clone for Arc<T, A>

where A: Allocator + Clone, T: ?Sized,

fn clone(&self) -> Arc<T, A>

Makes a clone of the Arc pointer.

This creates another pointer to the same allocation, increasing the strong reference count.

Examples

use std::sync::Arc;

let five = Arc::new(5);

let _ = Arc::clone(&five);

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

Performs copy-assignment from source.

impl<T> CloneFromCell for Arc<T>

where T: ?Sized,

impl<T, U, A> CoerceUnsized<Arc<U, A>> for Arc<T, A>

where T: Unsize<U> + ?Sized, A: Allocator, U: ?Sized,

impl Config for Arc<dyn Config>

fn headers(&self) -> HeaderMap

fn url(&self, path: &str) -> String

fn query(&self) -> Vec<(&str, &str)>

fn api_base(&self) -> &str

fn api_key(&self) -> &SecretBox<str>

impl<T, A> Debug for Arc<T, A>

where T: Debug + ?Sized, A: Allocator,

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

Formats the value using the given formatter.

impl<T> Default for Arc<T>

where T: Default,

Available on non-no_global_oom_handling only.

fn default() -> Arc<T>

Creates a new Arc<T>, with the Default value for T.

Examples

use std::sync::Arc;

let x: Arc<i32> = Default::default();
assert_eq!(*x, 0);

impl Default for Arc<str>

Available on non-no_global_oom_handling only.

fn default() -> Arc<str>

Creates an empty str inside an Arc

This may or may not share an allocation with other Arcs.

impl Default for Arc<CStr>

Available on non-no_global_oom_handling only.

fn default() -> Arc<CStr>

Creates an empty CStr inside an Arc

This may or may not share an allocation with other Arcs.

impl<T> Default for Arc<[T]>

Available on non-no_global_oom_handling only.

fn default() -> Arc<[T]>

Creates an empty [T] inside an Arc

This may or may not share an allocation with other Arcs.

impl<T> Default for Pin<Arc<T>>

where Arc<T>: Default, T: ?Sized,

Available on non-no_global_oom_handling only.

fn default() -> Pin<Arc<T>>

Returns the “default value” for a type.

impl<T, A> Deref for Arc<T, A>

where A: Allocator, T: ?Sized,

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &T

Dereferences the value.

impl<T, A> DerefPure for Arc<T, A>

where A: Allocator, T: ?Sized,

impl<'de, T> Deserialize<'de> for Arc<T>

where Box<T>: Deserialize<'de>, T: ?Sized,

Available on crate feature rc and (crate features alloc or std) only.

This impl requires the "rc" Cargo feature of Serde.

Deserializing a data structure containing Arc will not attempt to deduplicate Arc references to the same data. Every deserialized Arc will end up with a strong count of 1.

fn deserialize<D>( deserializer: D, ) -> Result<Arc<T>, <D as Deserializer<'de>>::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<T, U> DispatchFromDyn<Arc<U>> for Arc<T>

where T: Unsize<U> + ?Sized, U: ?Sized,

impl<T, A> Display for Arc<T, A>

where T: Display + ?Sized, A: Allocator,

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

Formats the value using the given formatter.

impl<T, A> Drop for Arc<T, A>

where A: Allocator, T: ?Sized,

fn drop(&mut self)

Drops the Arc.

This will decrement the strong reference count. If the strong reference count reaches zero then the only other references (if any) are Weak, so we drop the inner value.

Examples

use std::sync::Arc;

struct Foo;

impl Drop for Foo {
    fn drop(&mut self) {
        println!("dropped!");
    }
}

let foo  = Arc::new(Foo);
let foo2 = Arc::clone(&foo);

drop(foo);    // Doesn't print anything
drop(foo2);   // Prints "dropped!"

fn pin_drop(self: Pin<&mut Self>)

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

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.

impl ElementQueryable for Arc<SessionHandle>

fn query(&self, by: By) -> ElementQuery

Return an ElementQuery instance for more executing powerful element queries.

This uses the builder pattern to construct queries that will return one or more elements, depending on the method specified at the end of the chain.

See ElementQuery for more documentation.

impl<T, A> Eq for Arc<T, A>

where T: Eq + ?Sized, A: Allocator,

impl<T> Error for Arc<T>

where T: Error + ?Sized,

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn provide<'a>(&'a self, req: &mut Request<'a>)

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

Provides type-based access to context intended for error reports.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

impl<S> Filter<S> for Arc<dyn Filter<S> + Sync + Send>

Available on crate feature registry only.

fn enabled(&self, meta: &Metadata<'_>, cx: &Context<'_, S>) -> bool

Returns true if this layer is interested in a span or event with the given Metadata in the current Context, similarly to Subscriber::enabled.

fn callsite_enabled(&self, meta: &'static Metadata<'static>) -> Interest

Returns an Interest indicating whether this layer will always, sometimes, or never be interested in the given Metadata.

fn max_level_hint(&self) -> Option<LevelFilter>

Returns an optional hint of the highest verbosity level that this Filter will enable.

fn event_enabled(&self, event: &Event<'_>, cx: &Context<'_, S>) -> bool

Called before the filtered [Layer]'s [on_event], to determine if on_event` should be called.

fn on_new_span(&self, attrs: &Attributes<'_>, id: &Id, ctx: Context<'_, S>)

Notifies this filter that a new span was constructed with the given Attributes and Id.

fn on_record(&self, id: &Id, values: &Record<'_>, ctx: Context<'_, S>)

Notifies this filter that a span with the given Id recorded the given values.

fn on_enter(&self, id: &Id, ctx: Context<'_, S>)

Notifies this filter that a span with the given ID was entered.

fn on_exit(&self, id: &Id, ctx: Context<'_, S>)

Notifies this filter that a span with the given ID was exited.

fn on_close(&self, id: Id, ctx: Context<'_, S>)

Notifies this filter that a span with the given ID has been closed.

impl From<&CStr> for Arc<CStr>

Available on target_has_atomic=ptr only.

fn from(s: &CStr) -> Arc<CStr>

Converts a &CStr into a Arc<CStr>, by copying the contents into a newly allocated Arc.

impl From<&OsStr> for Arc<OsStr>

fn from(s: &OsStr) -> Arc<OsStr>

Copies the string into a newly allocated Arc<OsStr>.

impl From<&Path> for Arc<Path>

fn from(s: &Path) -> Arc<Path>

Converts a Path into an Arc by copying the Path data into a new Arc buffer.

impl<T> From<&[T]> for Arc<[T]>

where T: Clone,

Available on non-no_global_oom_handling only.

fn from(v: &[T]) -> Arc<[T]>

Allocates a reference-counted slice and fills it by cloning v’s items.

Example

let original: &[i32] = &[1, 2, 3];
let shared: Arc<[i32]> = Arc::from(original);
assert_eq!(&[1, 2, 3], &shared[..]);

impl From<&mut CStr> for Arc<CStr>

Available on target_has_atomic=ptr only.

fn from(s: &mut CStr) -> Arc<CStr>

Converts a &mut CStr into a Arc<CStr>, by copying the contents into a newly allocated Arc.

impl From<&mut OsStr> for Arc<OsStr>

fn from(s: &mut OsStr) -> Arc<OsStr>

Copies the string into a newly allocated Arc<OsStr>.

impl From<&mut Path> for Arc<Path>

fn from(s: &mut Path) -> Arc<Path>

Converts a Path into an Arc by copying the Path data into a new Arc buffer.

impl<T> From<&mut [T]> for Arc<[T]>

where T: Clone,

Available on non-no_global_oom_handling only.

fn from(v: &mut [T]) -> Arc<[T]>

Allocates a reference-counted slice and fills it by cloning v’s items.

Example

let mut original = [1, 2, 3];
let original: &mut [i32] = &mut original;
let shared: Arc<[i32]> = Arc::from(original);
assert_eq!(&[1, 2, 3], &shared[..]);

impl From<&mut str> for Arc<str>

Available on non-no_global_oom_handling only.

fn from(v: &mut str) -> Arc<str>

Allocates a reference-counted str and copies v into it.

Example

let mut original = String::from("eggplant");
let original: &mut str = &mut original;
let shared: Arc<str> = Arc::from(original);
assert_eq!("eggplant", &shared[..]);

impl From<&str> for Arc<str>

Available on non-no_global_oom_handling only.

fn from(v: &str) -> Arc<str>

Allocates a reference-counted str and copies v into it.

Example

let shared: Arc<str> = Arc::from("eggplant");
assert_eq!("eggplant", &shared[..]);

impl From<Arc<ByteStr>> for Arc<[u8]>

Available on target_has_atomic=ptr and non-no_rc and non-no_sync only.

fn from(s: Arc<ByteStr>) -> Arc<[u8]>

Converts to this type from the input type.

impl From<Arc<CertifiedKey>> for SingleCertAndKey

fn from(certified_key: Arc<CertifiedKey>) -> SingleCertAndKey

Converts to this type from the input type.

impl From<Arc<ClientConfig>> for TlsConnector

fn from(inner: Arc<ClientConfig>) -> TlsConnector

Converts to this type from the input type.

impl From<Arc<ServerConfig>> for TlsAcceptor

fn from(inner: Arc<ServerConfig>) -> TlsAcceptor

Converts to this type from the input type.

impl<W> From<Arc<W>> for Waker

where W: Wake + Send + Sync + 'static,

Available on target_has_atomic=ptr only.

fn from(waker: Arc<W>) -> Waker

Use a Wake-able type as a Waker.

No heap allocations or atomic operations are used for this conversion.

impl<W> From<Arc<W>> for RawWaker

where W: Wake + Send + Sync + 'static,

Available on target_has_atomic=ptr only.

fn from(waker: Arc<W>) -> RawWaker

Use a Wake-able type as a RawWaker.

No heap allocations or atomic operations are used for this conversion.

impl From<Arc<[u8]>> for Arc<ByteStr>

Available on target_has_atomic=ptr and non-no_rc and non-no_sync only.

fn from(s: Arc<[u8]>) -> Arc<ByteStr>

Converts to this type from the input type.

impl From<Arc<str>> for Arc<[u8]>

fn from(rc: Arc<str>) -> Arc<[u8]>

Converts an atomically reference-counted string slice into a byte slice.

Example

let string: Arc<str> = Arc::from("eggplant");
let bytes: Arc<[u8]> = Arc::from(string);
assert_eq!("eggplant".as_bytes(), bytes.as_ref());

impl<T, A> From<Box<T, A>> for Arc<T, A>

where A: Allocator, T: ?Sized,

Available on non-no_global_oom_handling only.

fn from(v: Box<T, A>) -> Arc<T, A>

Move a boxed object to a new, reference-counted allocation.

Example

let unique: Box<str> = Box::from("eggplant");
let shared: Arc<str> = Arc::from(unique);
assert_eq!("eggplant", &shared[..]);

impl From<CString> for Arc<CStr>

Available on target_has_atomic=ptr only.

fn from(s: CString) -> Arc<CStr>

Converts a CString into an Arc<CStr> by moving the CString data into a new Arc buffer.

impl From<CompactString> for Arc<str>

Available on target_has_atomic=ptr only.

fn from(value: CompactString) -> Arc<str>

Converts to this type from the input type.

impl<'a, B> From<Cow<'a, B>> for Arc<B>

where B: ToOwned + ?Sized, Arc<B>: From<&'a B> + From<<B as ToOwned>::Owned>,

fn from(cow: Cow<'a, B>) -> Arc<B>

Creates an atomically reference-counted pointer from a clone-on-write pointer by copying its content.

Example

let cow: Cow<'_, str> = Cow::Borrowed("eggplant");
let shared: Arc<str> = Arc::from(cow);
assert_eq!("eggplant", &shared[..]);

impl From<OsString> for Arc<OsStr>

fn from(s: OsString) -> Arc<OsStr>

Converts an OsString into an Arc<OsStr> by moving the OsString data into a new Arc buffer.

impl From<PathBuf> for Arc<Path>

fn from(s: PathBuf) -> Arc<Path>

Converts a PathBuf into an Arc<Path> by moving the PathBuf data into a new Arc buffer.

impl From<String> for Arc<str>

Available on non-no_global_oom_handling only.

fn from(v: String) -> Arc<str>

Allocates a reference-counted str and copies v into it.

Example

let unique: String = "eggplant".to_owned();
let shared: Arc<str> = Arc::from(unique);
assert_eq!("eggplant", &shared[..]);

impl<T> From<T> for Arc<T>

Available on non-no_global_oom_handling only.

fn from(t: T) -> Arc<T>

Converts a T into an Arc<T>

The conversion moves the value into a newly allocated Arc. It is equivalent to calling Arc::new(t).

Example

let x = 5;
let arc = Arc::new(5);

assert_eq!(Arc::from(x), arc);

impl<T, A> From<Vec<T, A>> for Arc<[T], A>

where A: Allocator + Clone,

Available on non-no_global_oom_handling only.

fn from(v: Vec<T, A>) -> Arc<[T], A>

Allocates a reference-counted slice and moves v’s items into it.

Example

let unique: Vec<i32> = vec![1, 2, 3];
let shared: Arc<[i32]> = Arc::from(unique);
assert_eq!(&[1, 2, 3], &shared[..]);

impl<T, const N: usize> From<[T; N]> for Arc<[T]>

Available on non-no_global_oom_handling only.

fn from(v: [T; N]) -> Arc<[T]>

Converts a [T; N] into an Arc<[T]>.

The conversion moves the array into a newly allocated Arc.

Example

let original: [i32; 3] = [1, 2, 3];
let shared: Arc<[i32]> = Arc::from(original);
assert_eq!(&[1, 2, 3], &shared[..]);

impl<T> FromIterator<T> for Arc<[T]>

Available on non-no_global_oom_handling only.

fn from_iter<I>(iter: I) -> Arc<[T]>

where I: IntoIterator<Item = T>,

Takes each element in the Iterator and collects it into an Arc<[T]>.

Performance characteristics

The general case

In the general case, collecting into Arc<[T]> is done by first collecting into a Vec<T>. That is, when writing the following:

let evens: Arc<[u8]> = (0..10).filter(|&x| x % 2 == 0).collect();

this behaves as if we wrote:

let evens: Arc<[u8]> = (0..10).filter(|&x| x % 2 == 0)
    .collect::<Vec<_>>() // The first set of allocations happens here.
    .into(); // A second allocation for `Arc<[T]>` happens here.

This will allocate as many times as needed for constructing the Vec<T> and then it will allocate once for turning the Vec<T> into the Arc<[T]>.

Iterators of known length

When your Iterator implements TrustedLen and is of an exact size, a single allocation will be made for the Arc<[T]>. For example:

let evens: Arc<[u8]> = (0..10).collect(); // Just a single allocation happens here.

impl<T> GenerateImplicitData for Arc<T>

where T: GenerateImplicitData,

Available on crate feature std, or target_has_atomic=ptr and crate feature rust_1_61 only.

fn generate() -> Arc<T>

Build the data.

fn generate_with_source(source: &dyn Error) -> Arc<T>

where Arc<T>: Sized,

Build the data using the given source

impl<T> GetSize for Arc<T>

where T: GetSize,

fn get_heap_size_with_tracker<Tr>(&self, tracker: Tr) -> (usize, Tr)

where Tr: GetSizeTracker,

Determines how many bytes this object occupies inside the heap while using a tracker.

fn get_stack_size() -> usize

Determines how may bytes this object occupies inside the stack.

fn get_heap_size(&self) -> usize

Determines how many bytes this object occupies inside the heap.

fn get_size(&self) -> usize

Determines the total size of the object.

fn get_size_with_tracker<T>(&self, tracker: T) -> (usize, T)

where T: GetSizeTracker,

Determines the total size of the object while using a tracker.

impl<T> GetSize for Arc<[T]>

where T: GetSize,

fn get_heap_size_with_tracker<Tr>(&self, tracker: Tr) -> (usize, Tr)

where Tr: GetSizeTracker,

Determines how many bytes this object occupies inside the heap while using a tracker.

fn get_stack_size() -> usize

Determines how may bytes this object occupies inside the stack.

fn get_heap_size(&self) -> usize

Determines how many bytes this object occupies inside the heap.

fn get_size(&self) -> usize

Determines the total size of the object.

fn get_size_with_tracker<T>(&self, tracker: T) -> (usize, T)

where T: GetSizeTracker,

Determines the total size of the object while using a tracker.

impl GetSize for Arc<str>

fn get_heap_size_with_tracker<T>(&self, tracker: T) -> (usize, T)

where T: GetSizeTracker,

Determines how many bytes this object occupies inside the heap while using a tracker.

fn get_stack_size() -> usize

Determines how may bytes this object occupies inside the stack.

fn get_heap_size(&self) -> usize

Determines how many bytes this object occupies inside the heap.

fn get_size(&self) -> usize

Determines the total size of the object.

fn get_size_with_tracker<T>(&self, tracker: T) -> (usize, T)

where T: GetSizeTracker,

Determines the total size of the object while using a tracker.

impl<T> GetSizeTracker for Arc<Mutex<T>>

where T: GetSizeTracker,

fn track<A>(&mut self, addr: *const A) -> bool

Tracks an arbitrary object located at addr.

impl<T> GetSizeTracker for Arc<RwLock<T>>

where T: GetSizeTracker,

fn track<A>(&mut self, addr: *const A) -> bool

Tracks an arbitrary object located at addr.

impl<T, A> Hash for Arc<T, A>

where T: Hash + ?Sized, A: Allocator,

fn hash<H>(&self, state: &mut H)

where H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<T> JsonSchema for Arc<T>

where T: JsonSchema + ?Sized,

fn inline_schema() -> bool

Whether JSON Schemas generated for this type should be included directly in parent schemas, rather than being re-used where possible using the $ref keyword.

fn schema_name() -> Cow<'static, str>

The name of the generated JSON Schema.

fn schema_id() -> Cow<'static, str>

Returns a string that uniquely identifies the schema produced by this type.

fn json_schema(generator: &mut SchemaGenerator) -> Schema

Generates a JSON Schema for this type.

impl<T> LifetimeFree for Arc<T>

where T: LifetimeFree,

Available on target_has_atomic=ptr only.

impl<Sp> LocalSpawn for Arc<Sp>

where Sp: LocalSpawn + ?Sized,

fn spawn_local_obj( &self, future: LocalFutureObj<'static, ()>, ) -> Result<(), SpawnError>

Spawns a future that will be run to completion.

fn status_local(&self) -> Result<(), SpawnError>

Determines whether the executor is able to spawn new tasks.

impl<T> Log for Arc<T>

where T: Log + ?Sized,

Available on crate feature std only.

fn enabled(&self, metadata: &Metadata<'_>) -> bool

Determines if a log message with the specified metadata would be logged.

fn log(&self, record: &Record<'_>)

Logs the Record.

fn flush(&self)

Flushes any buffered records.

impl<'a, W> MakeWriter<'a> for Arc<W>

where &'a W: Write + 'a,

type Writer = &'a W

The concrete io::Write implementation returned by make_writer.

fn make_writer(&'a self) -> <Arc<W> as MakeWriter<'a>>::Writer

Returns an instance of Writer.

fn make_writer_for(&'a self, meta: &Metadata<'_>) -> Self::Writer

Returns a Writer for writing data from the span or event described by the provided Metadata.

impl<T, A> Ord for Arc<T, A>

where T: Ord + ?Sized, A: Allocator,

fn cmp(&self, other: &Arc<T, A>) -> Ordering

Comparison for two Arcs.

The two are compared by calling cmp() on their inner values.

Examples

use std::sync::Arc;
use std::cmp::Ordering;

let five = Arc::new(5);

assert_eq!(Ordering::Less, five.cmp(&Arc::new(6)));

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<T, A> PartialEq for Arc<T, A>

where T: PartialEq + ?Sized, A: Allocator,

fn eq(&self, other: &Arc<T, A>) -> bool

Equality for two Arcs.

Two Arcs are equal if their inner values are equal, even if they are stored in different allocation.

If T also implements Eq (implying reflexivity of equality), two Arcs that point to the same allocation are always equal.

Examples

use std::sync::Arc;

let five = Arc::new(5);

assert!(five == Arc::new(5));

fn ne(&self, other: &Arc<T, A>) -> bool

Inequality for two Arcs.

Two Arcs are not equal if their inner values are not equal.

If T also implements Eq (implying reflexivity of equality), two Arcs that point to the same value are always equal.

Examples

use std::sync::Arc;

let five = Arc::new(5);

assert!(five != Arc::new(6));

impl<T, A> PartialOrd for Arc<T, A>

where T: PartialOrd + ?Sized, A: Allocator,

fn partial_cmp(&self, other: &Arc<T, A>) -> Option<Ordering>

Partial comparison for two Arcs.

The two are compared by calling partial_cmp() on their inner values.

Examples

use std::sync::Arc;
use std::cmp::Ordering;

let five = Arc::new(5);

assert_eq!(Some(Ordering::Less), five.partial_cmp(&Arc::new(6)));

fn lt(&self, other: &Arc<T, A>) -> bool

Less-than comparison for two Arcs.

The two are compared by calling < on their inner values.

Examples

use std::sync::Arc;

let five = Arc::new(5);

assert!(five < Arc::new(6));

fn le(&self, other: &Arc<T, A>) -> bool

‘Less than or equal to’ comparison for two Arcs.

The two are compared by calling <= on their inner values.

Examples

use std::sync::Arc;

let five = Arc::new(5);

assert!(five <= Arc::new(5));

fn gt(&self, other: &Arc<T, A>) -> bool

Greater-than comparison for two Arcs.

The two are compared by calling > on their inner values.

Examples

use std::sync::Arc;

let five = Arc::new(5);

assert!(five > Arc::new(4));

fn ge(&self, other: &Arc<T, A>) -> bool

‘Greater than or equal to’ comparison for two Arcs.

The two are compared by calling >= on their inner values.

Examples

use std::sync::Arc;

let five = Arc::new(5);

assert!(five >= Arc::new(5));

impl<T, A> PinSafePointer for Arc<T, A>

where A: Allocator + 'static, T: ?Sized,

impl<T, A> Pointer for Arc<T, A>

where A: Allocator, T: ?Sized,

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

Formats the value using the given formatter.

impl<T> Ranged for Arc<T>

where T: Ranged,

fn range(&self) -> TextRange

The range of this item in the source text.

fn start(&self) -> TextSize

The start offset of this item in the source text.

fn end(&self) -> TextSize

The end offset of this item in the source text.

impl<R> Read for Arc<R>

where R: Read + IoHandle + ?Sized, &'a R: for<'a> Read,

Available on target_has_atomic=ptr and non-no_rc and non-no_sync only.

fn read(&mut self, buf: &mut [u8]) -> Result<usize, Error>

Pull some bytes from this source into the specified buffer, returning how many bytes were read.

fn read_buf(&mut self, cursor: BorrowedCursor<'_, u8>) -> Result<(), Error>

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

Pull some bytes from this source into the specified buffer.

fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize, Error>

Like read, except that it reads into a slice of buffers.

fn is_read_vectored(&self) -> bool

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

Determines if this Reader has an efficient read_vectored implementation.

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize, Error>

Reads all bytes until EOF in this source, placing them into buf.

fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>

Reads all bytes until EOF in this source, appending them to buf.

fn read_exact(&mut self, buf: &mut [u8]) -> Result<(), Error>

Reads the exact number of bytes required to fill buf.

fn read_buf_exact( &mut self, cursor: BorrowedCursor<'_, u8>, ) -> Result<(), Error>

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

Reads the exact number of bytes required to fill cursor.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Read.

fn bytes(self) -> Bytes<Self>

where Self: Sized,

Transforms this Read instance to an Iterator over its bytes.

fn chain<R>(self, next: R) -> Chain<Self, R>

where R: Read, Self: Sized,

Creates an adapter which will chain this stream with another.

fn take(self, limit: u64) -> Take<Self>

where Self: Sized,

Creates an adapter which will read at most limit bytes from it.

fn read_array<const N: usize>(&mut self) -> Result<[u8; N], Error>

where Self: Sized,

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

Read and return a fixed array of bytes from this source.

fn read_le<T>(&mut self) -> Result<T, Error>

where T: FromEndianBytes, Self: Sized,

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

Read and return a type (e.g. an integer) in little-endian order.

fn read_be<T>(&mut self) -> Result<T, Error>

where T: FromEndianBytes, Self: Sized,

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

Read and return a type (e.g. an integer) in big-endian order.

impl<T> RefCnt for Arc<T>

type Base = T

The base type the pointer points to.

fn into_ptr(me: Arc<T>) -> *mut T

Converts the smart pointer into a raw pointer, without affecting the reference count.

fn as_ptr(me: &Arc<T>) -> *mut T

Provides a view into the smart pointer as a raw pointer.

unsafe fn from_ptr(ptr: *const T) -> Arc<T>

Converts a raw pointer back into the smart pointer, without affecting the reference count.

fn inc(me: &Self) -> *mut Self::Base

Increments the reference count by one.

unsafe fn dec(ptr: *const Self::Base)

Decrements the reference count by one.

impl<T> RefCnt for Pin<Arc<T>>

type Base = T

The base type the pointer points to.

fn into_ptr(me: Pin<Arc<T>>) -> *mut T

Converts the smart pointer into a raw pointer, without affecting the reference count.

fn as_ptr(me: &Pin<Arc<T>>) -> *mut T

Provides a view into the smart pointer as a raw pointer.

unsafe fn from_ptr(ptr: *const T) -> Pin<Arc<T>>

Converts a raw pointer back into the smart pointer, without affecting the reference count.

fn inc(me: &Self) -> *mut Self::Base

Increments the reference count by one.

unsafe fn dec(ptr: *const Self::Base)

Decrements the reference count by one.

impl<S> Seek for Arc<S>

where S: Seek + IoHandle + ?Sized, &'a S: for<'a> Seek,

Available on target_has_atomic=ptr and non-no_rc and non-no_sync only.

fn seek(&mut self, pos: SeekFrom) -> Result<u64, Error>

Seek to an offset, in bytes, in a stream.

fn rewind(&mut self) -> Result<(), Error>

Rewind to the beginning of a stream.

fn stream_len(&mut self) -> Result<u64, Error>

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

Returns the length of this stream (in bytes).

fn stream_position(&mut self) -> Result<u64, Error>

Returns the current seek position from the start of the stream.

fn seek_relative(&mut self, offset: i64) -> Result<(), Error>

Seeks relative to the current position.

impl<T, A> Send for Arc<T, A>

where T: Sync + Send + ?Sized, A: Allocator + Send,

impl<T> Serialize for Arc<T>

where T: Serialize + ?Sized,

Available on crate feature rc and (crate features alloc or std) only.

This impl requires the "rc" Cargo feature of Serde.

Serializing a data structure containing Arc will serialize a copy of the contents of the Arc each time the Arc is referenced within the data structure. Serialization will not attempt to deduplicate these repeated data.

fn serialize<S>( &self, serializer: S, ) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl<T> ServerHandler for Arc<T>

where T: ServerHandler,

fn ping( &self, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

fn initialize( &self, request: InitializeRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<InitializeResult, ErrorData>> + MaybeSendFuture

fn supported_protocol_versions(&self) -> Cow<'static, [ProtocolVersion]>

Return the protocol versions supported by this server.

fn discover( &self, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<DiscoverResult, ErrorData>> + MaybeSendFuture

Return this server’s discovery information.

fn complete( &self, request: CompleteRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<CompleteResult, ErrorData>> + MaybeSendFuture

fn set_level( &self, request: SetLevelRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

fn get_prompt( &self, request: GetPromptRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<GetPromptResponse, ErrorData>> + MaybeSendFuture

fn list_prompts( &self, request: Option<PaginatedRequestParams>, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ListPromptsResult, ErrorData>> + MaybeSendFuture

fn list_resources( &self, request: Option<PaginatedRequestParams>, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ListResourcesResult, ErrorData>> + MaybeSendFuture

fn list_resource_templates( &self, request: Option<PaginatedRequestParams>, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ListResourceTemplatesResult, ErrorData>> + MaybeSendFuture

fn read_resource( &self, request: ReadResourceRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ReadResourceResponse, ErrorData>> + MaybeSendFuture

fn accepted_subscription_filter( &self, requested: &SubscriptionFilter, ) -> Option<SubscriptionFilter>

Return the subset of a requested notification filter this server accepts.

fn listen( &self, context: SubscriptionContext, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

Run one established subscription until it is cancelled or closed gracefully.

fn subscribe( &self, request: SubscribeRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

👎Deprecated:

resources/subscribe is legacy-only; implement accepted_subscription_filter and listen for protocol version 2026-07-28

fn unsubscribe( &self, request: UnsubscribeRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

👎Deprecated:

resources/unsubscribe is legacy-only; subscriptions/listen is cancelled through its request lifecycle

fn call_tool( &self, request: CallToolRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<CallToolResponse, ErrorData>> + MaybeSendFuture

Handle a tools/call request from a client.

fn list_tools( &self, request: Option<PaginatedRequestParams>, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ListToolsResult, ErrorData>> + MaybeSendFuture

fn get_tool(&self, name: &str) -> Option<Tool>

Get a tool definition by name.

fn on_custom_request( &self, request: CustomRequest, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<CustomResult, ErrorData>> + MaybeSendFuture

fn on_cancelled( &self, notification: CancelledNotificationParam, context: NotificationContext<RoleServer>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_progress( &self, notification: ProgressNotificationParam, context: NotificationContext<RoleServer>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_initialized( &self, context: NotificationContext<RoleServer>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_roots_list_changed( &self, context: NotificationContext<RoleServer>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_custom_notification( &self, notification: CustomNotification, context: NotificationContext<RoleServer>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn get_info(&self) -> InitializeResult

fn get_task( &self, request: GetTaskParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<GetTaskResult, ErrorData>> + MaybeSendFuture

SEP-2663 tasks/get: return the current DetailedTask state.

fn update_task( &self, request: UpdateTaskParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

SEP-2663 tasks/update: accept responses to outstanding in-task input requests. Returns an empty acknowledgement on success.

fn cancel_task( &self, request: CancelTaskParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

SEP-2663 tasks/cancel: cooperative cancellation. Returns an empty acknowledgement; the task’s observable status may lag.

impl<Request, S> Service<Request> for Arc<S>

where S: Service<Request> + ?Sized,

type Response = <S as Service<Request>>::Response

Responses given by the service.

type Error = <S as Service<Request>>::Error

Errors produced by the service.

type Future = <S as Service<Request>>::Future

The future response value.

fn call(&self, req: Request) -> <Arc<S> as Service<Request>>::Future

Process the request and return the response asynchronously. call takes &self instead of mut &self because:

impl<T, A> Share for Arc<T, A>

where A: Allocator + Clone, T: ?Sized,

final fn share(&self) -> Self

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

Creates another alias to the same underlying resource or shared state.

impl<Sp> Spawn for Arc<Sp>

where Sp: Spawn + ?Sized,

fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError>

Spawns a future that will be run to completion.

fn status(&self) -> Result<(), SpawnError>

Determines whether the executor is able to spawn new tasks.

impl<S> Subscriber for Arc<S>

where S: Subscriber + ?Sized,

fn register_callsite(&self, metadata: &'static Metadata<'static>) -> Interest

Registers a new callsite with this subscriber, returning whether or not the subscriber is interested in being notified about the callsite.

fn enabled(&self, metadata: &Metadata<'_>) -> bool

Returns true if a span or event with the specified metadata would be recorded.

fn max_level_hint(&self) -> Option<LevelFilter>

Returns the highest verbosity level that this Subscriber will enable, or None, if the subscriber does not implement level-based filtering or chooses not to implement this method.

fn new_span(&self, span: &Attributes<'_>) -> Id

Visit the construction of a new span, returning a new span ID for the span being constructed.

fn record(&self, span: &Id, values: &Record<'_>)

Record a set of values on a span.

fn record_follows_from(&self, span: &Id, follows: &Id)

Adds an indication that span follows from the span with the id follows.

fn event_enabled(&self, event: &Event<'_>) -> bool

Determine if an Event should be recorded.

fn event(&self, event: &Event<'_>)

Records that an Event has occurred.

fn enter(&self, span: &Id)

Records that a span has been entered.

fn exit(&self, span: &Id)

Records that a span has been exited.

fn clone_span(&self, id: &Id) -> Id

Notifies the subscriber that a span ID has been cloned.

fn try_close(&self, id: Id) -> bool

Notifies the subscriber that a span ID has been dropped, and returns true if there are now 0 IDs that refer to that span.

fn drop_span(&self, id: Id)

👎Deprecated since 0.1.2:

use Subscriber::try_close instead

This method is deprecated.

fn current_span(&self) -> Current

Returns a type representing this subscriber’s view of the current span.

unsafe fn downcast_raw(&self, id: TypeId) -> Option<*const ()>

If self is the same type as the provided TypeId, returns an untyped *const pointer to that type. Otherwise, returns None.

fn on_register_dispatch(&self, subscriber: &Dispatch)

Invoked when this subscriber becomes a Dispatch.

impl<T, A> Sync for Arc<T, A>

where T: Sync + Send + ?Sized, A: Allocator + Sync,

impl<T, A, const N: usize> TryFrom<Arc<[T], A>> for Arc<[T; N], A>

where A: Allocator,

type Error = Arc<[T], A>

The type returned in the event of a conversion error.

fn try_from( boxed_slice: Arc<[T], A>, ) -> Result<Arc<[T; N], A>, <Arc<[T; N], A> as TryFrom<Arc<[T], A>>>::Error>

Performs the conversion.

impl<T, A> Unpin for Arc<T, A>

where A: Allocator, T: ?Sized,

impl<T, A> UnwindSafe for Arc<T, A>

where T: RefUnwindSafe + ?Sized, A: Allocator + UnwindSafe,

impl<T, A> UseCloned for Arc<T, A>

where A: Allocator + Clone, T: ?Sized,

impl<W> Write for Arc<W>

where W: Write + IoHandle + ?Sized, &'a W: for<'a> Write,

Available on target_has_atomic=ptr and non-no_rc and non-no_sync only.

fn write(&mut self, buf: &[u8]) -> Result<usize, Error>

Writes a buffer into this writer, returning how many bytes were written.

fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

fn is_write_vectored(&self) -> bool

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

Determines if this Writer has an efficient write_vectored implementation.

fn flush(&mut self) -> Result<(), Error>

Flushes this output stream, ensuring that all intermediately buffered contents reach their destination.

fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>

Attempts to write an entire buffer into this writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

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

Attempts to write multiple buffers into this writer.

fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Write.