1.0.0[][src]Struct std::rc::Rc

#[lang = "rc"]
pub struct Rc<T> where
    T: ?Sized
{ /* fields omitted */ }

A single-threaded reference-counting pointer. 'Rc' stands for 'Reference Counted'.

See the module-level documentation for more details.

The inherent methods of Rc are all associated functions, which means that you have to call them as e.g., Rc::get_mut(&mut value) instead of value.get_mut(). This avoids conflicts with methods of the inner type T.

Methods

impl<T> Rc<T>[src]

pub fn new(value: T) -> Rc<T>[src]

Constructs a new Rc<T>.

Examples

use std::rc::Rc;

let five = Rc::new(5);Run

pub fn new_uninit() -> Rc<MaybeUninit<T>>[src]

🔬 This is a nightly-only experimental API. (new_uninit #63291)

Constructs a new Rc with uninitialized contents.

Examples

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

use std::rc::Rc;

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

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

    five.assume_init()
};

assert_eq!(*five, 5)Run

Important traits for Pin<P>
pub fn pin(value: T) -> Pin<Rc<T>>1.33.0[src]

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

pub fn try_unwrap(this: Rc<T>) -> Result<T, Rc<T>>1.4.0[src]

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

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

This will succeed even if there are outstanding weak references.

Examples

use std::rc::Rc;

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

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

impl<T> Rc<[T]>[src]

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

🔬 This is a nightly-only experimental API. (new_uninit #63291)

Constructs a new reference-counted slice with uninitialized contents.

Examples

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

use std::rc::Rc;

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

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

    values.assume_init()
};

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

impl<T> Rc<MaybeUninit<T>>[src]

pub unsafe fn assume_init(self) -> Rc<T>[src]

🔬 This is a nightly-only experimental API. (new_uninit #63291)

Converts to Rc<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

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

use std::rc::Rc;

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

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

    five.assume_init()
};

assert_eq!(*five, 5)Run

impl<T> Rc<[MaybeUninit<T>]>[src]

pub unsafe fn assume_init(self) -> Rc<[T]>[src]

🔬 This is a nightly-only experimental API. (new_uninit #63291)

Converts to Rc<[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

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

use std::rc::Rc;

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

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

    values.assume_init()
};

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

impl<T> Rc<T> where
    T: ?Sized
[src]

pub fn into_raw(this: Rc<T>) -> *const T1.17.0[src]

Consumes the Rc, returning the wrapped pointer.

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

Examples

use std::rc::Rc;

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

pub unsafe fn from_raw(ptr: *const T) -> Rc<T>1.17.0[src]

Constructs an Rc from a raw pointer.

The raw pointer must have been previously returned by a call to a Rc::into_raw.

This function is unsafe because improper use may lead to memory problems. For example, a double-free may occur if the function is called twice on the same raw pointer.

Examples

use std::rc::Rc;

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

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

    // Further calls to `Rc::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!Run

pub fn into_raw_non_null(this: Rc<T>) -> NonNull<T>[src]

🔬 This is a nightly-only experimental API. (rc_into_raw_non_null #47336)

Consumes the Rc, returning the wrapped pointer as NonNull<T>.

Examples

#![feature(rc_into_raw_non_null)]

use std::rc::Rc;

let x = Rc::new("hello".to_owned());
let ptr = Rc::into_raw_non_null(x);
let deref = unsafe { ptr.as_ref() };
assert_eq!(deref, "hello");Run

pub fn downgrade(this: &Rc<T>) -> Weak<T>1.4.0[src]

Creates a new Weak pointer to this allocation.

Examples

use std::rc::Rc;

let five = Rc::new(5);

let weak_five = Rc::downgrade(&five);Run

pub fn weak_count(this: &Rc<T>) -> usize1.15.0[src]

Gets the number of Weak pointers to this allocation.

Examples

use std::rc::Rc;

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

assert_eq!(1, Rc::weak_count(&five));Run

pub fn strong_count(this: &Rc<T>) -> usize1.15.0[src]

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

Examples

use std::rc::Rc;

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

assert_eq!(2, Rc::strong_count(&five));Run

pub fn get_mut(this: &mut Rc<T>) -> Option<&mut T>1.4.0[src]

Returns a mutable reference into the given Rc, if there are no other Rc 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 pointers.

Examples

use std::rc::Rc;

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

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

Important traits for &'_ mut I
pub unsafe fn get_mut_unchecked(this: &mut Rc<T>) -> &mut T[src]

🔬 This is a nightly-only experimental API. (get_mut_unchecked #63292)

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

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

Safety

Any other Rc or [Weak] pointers to the same allocation must not be dereferenced for the duration of the returned borrow. This is trivially the case if no such pointers exist, for example immediately after Rc::new.

Examples

#![feature(get_mut_unchecked)]

use std::rc::Rc;

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

pub fn ptr_eq(this: &Rc<T>, other: &Rc<T>) -> bool1.17.0[src]

Returns true if the two Rcs point to the same allocation (in a vein similar to ptr::eq).

Examples

use std::rc::Rc;

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

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

impl<T> Rc<T> where
    T: Clone
[src]

Important traits for &'_ mut I
pub fn make_mut(this: &mut Rc<T>) -> &mut T1.4.0[src]

Makes a mutable reference into the given Rc.

If there are other Rc 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.

If there are no other Rc pointers to this allocation, then Weak pointers to this allocation will be disassociated.

See also get_mut, which will fail rather than cloning.

Examples

use std::rc::Rc;

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

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

Weak pointers will be disassociated:

use std::rc::Rc;

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

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

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

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

impl Rc<dyn Any + 'static>[src]

pub fn downcast<T>(self) -> Result<Rc<T>, Rc<dyn Any + 'static>> where
    T: Any
1.29.0[src]

Attempt to downcast the Rc<dyn Any> to a concrete type.

Examples

use std::any::Any;
use std::rc::Rc;

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

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

Trait Implementations

impl<T> AsRef<T> for Rc<T> where
    T: ?Sized
1.5.0[src]

impl<T> Ord for Rc<T> where
    T: Ord + ?Sized
[src]

fn cmp(&self, other: &Rc<T>) -> Ordering[src]

Comparison for two Rcs.

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

Examples

use std::rc::Rc;
use std::cmp::Ordering;

let five = Rc::new(5);

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

impl<T, U> DispatchFromDyn<Rc<U>> for Rc<T> where
    T: Unsize<U> + ?Sized,
    U: ?Sized
[src]

impl<T> Borrow<T> for Rc<T> where
    T: ?Sized
[src]

impl<T> From<T> for Rc<T>1.6.0[src]

impl<'_> From<&'_ str> for Rc<str>1.21.0[src]

impl From<String> for Rc<str>1.21.0[src]

impl<'_, T> From<&'_ [T]> for Rc<[T]> where
    T: Clone
1.21.0[src]

impl<T> From<Box<T>> for Rc<T> where
    T: ?Sized
1.21.0[src]

impl<T> From<Vec<T>> for Rc<[T]>1.21.0[src]

impl<T> Deref for Rc<T> where
    T: ?Sized
[src]

type Target = T

The resulting type after dereferencing.

impl<T> Drop for Rc<T> where
    T: ?Sized
[src]

fn drop(&mut self)[src]

Drops the Rc.

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::rc::Rc;

struct Foo;

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

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

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

impl<T> PartialEq<Rc<T>> for Rc<T> where
    T: PartialEq<T> + ?Sized
[src]

fn eq(&self, other: &Rc<T>) -> bool[src]

Equality for two Rcs.

Two Rcs 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 Rcs that point to the same allocation are always equal.

Examples

use std::rc::Rc;

let five = Rc::new(5);

assert!(five == Rc::new(5));Run

fn ne(&self, other: &Rc<T>) -> bool[src]

Inequality for two Rcs.

Two Rcs are unequal if their inner values are unequal.

If T also implements Eq (implying reflexivity of equality), two Rcs that point to the same allocation are never unequal.

Examples

use std::rc::Rc;

let five = Rc::new(5);

assert!(five != Rc::new(6));Run

impl<T> Pointer for Rc<T> where
    T: ?Sized
[src]

impl<T> PartialOrd<Rc<T>> for Rc<T> where
    T: PartialOrd<T> + ?Sized
[src]

fn partial_cmp(&self, other: &Rc<T>) -> Option<Ordering>[src]

Partial comparison for two Rcs.

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

Examples

use std::rc::Rc;
use std::cmp::Ordering;

let five = Rc::new(5);

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

fn lt(&self, other: &Rc<T>) -> bool[src]

Less-than comparison for two Rcs.

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

Examples

use std::rc::Rc;

let five = Rc::new(5);

assert!(five < Rc::new(6));Run

fn le(&self, other: &Rc<T>) -> bool[src]

'Less than or equal to' comparison for two Rcs.

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

Examples

use std::rc::Rc;

let five = Rc::new(5);

assert!(five <= Rc::new(5));Run

fn gt(&self, other: &Rc<T>) -> bool[src]

Greater-than comparison for two Rcs.

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

Examples

use std::rc::Rc;

let five = Rc::new(5);

assert!(five > Rc::new(4));Run

fn ge(&self, other: &Rc<T>) -> bool[src]

'Greater than or equal to' comparison for two Rcs.

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

Examples

use std::rc::Rc;

let five = Rc::new(5);

assert!(five >= Rc::new(5));Run

impl<T> Default for Rc<T> where
    T: Default
[src]

fn default() -> Rc<T>[src]

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

Examples

use std::rc::Rc;

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

impl<T> Debug for Rc<T> where
    T: Debug + ?Sized
[src]

impl<T> Unpin for Rc<T> where
    T: ?Sized
1.33.0[src]

impl<T, U> CoerceUnsized<Rc<U>> for Rc<T> where
    T: Unsize<U> + ?Sized,
    U: ?Sized
[src]

impl<T> Eq for Rc<T> where
    T: Eq + ?Sized
[src]

impl<T> !Send for Rc<T> where
    T: ?Sized
[src]

impl<const N: usize, T> TryFrom<Rc<[T]>> for Rc<[T; N]> where
    [T; N]: LengthAtMost32
[src]

type Error = Rc<[T]>

The type returned in the event of a conversion error.

impl<T> Clone for Rc<T> where
    T: ?Sized
[src]

fn clone(&self) -> Rc<T>[src]

Makes a clone of the Rc pointer.

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

Examples

use std::rc::Rc;

let five = Rc::new(5);

let _ = Rc::clone(&five);Run

impl<T> Hash for Rc<T> where
    T: Hash + ?Sized
[src]

impl<T> Display for Rc<T> where
    T: Display + ?Sized
[src]

impl<T> !Sync for Rc<T> where
    T: ?Sized
[src]

impl<T> FromIterator<T> for Rc<[T]>1.37.0[src]

fn from_iter<I>(iter: I) -> Rc<[T]> where
    I: IntoIterator<Item = T>, 
[src]

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

Performance characteristics

The general case

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

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

this behaves as if we wrote:

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

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 Rc<[T]>.

Iterators of known length

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

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

impl<T: RefUnwindSafe + ?Sized> UnwindSafe for Rc<T>1.9.0[src]

impl From<CString> for Rc<CStr>1.24.0[src]

fn from(s: CString) -> Rc<CStr>[src]

Converts a CString into a Rc<CStr> without copying or allocating.

impl<'_> From<&'_ CStr> for Rc<CStr>1.24.0[src]

impl From<OsString> for Rc<OsStr>1.24.0[src]

fn from(s: OsString) -> Rc<OsStr>[src]

Converts a OsString into a Rc<OsStr> without copying or allocating.

impl<'_> From<&'_ OsStr> for Rc<OsStr>1.24.0[src]

impl From<PathBuf> for Rc<Path>1.24.0[src]

fn from(s: PathBuf) -> Rc<Path>[src]

Converts a PathBuf into an Rc by moving the PathBuf data into a new Rc buffer.

impl<'_> From<&'_ Path> for Rc<Path>1.24.0[src]

fn from(s: &Path) -> Rc<Path>[src]

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

Auto Trait Implementations

impl<T> !RefUnwindSafe for Rc<T>

Blanket Implementations

impl<T> From<T> for T[src]

impl<T> From<!> for T[src]

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

impl<T> Any for T where
    T: 'static + ?Sized
[src]

impl<T> ToOwned for T where
    T: Clone
[src]

type Owned = T

The resulting type after obtaining ownership.

impl<T> ToString for T where
    T: Display + ?Sized
[src]