Struct Weak

pub struct Weak<'a, T> { /* private fields */ }

A reference-counting pointer to the allocation of an Rc.

TODO

Evaluate an interface:

fn reinit(&self, val: T) -> Result<Rc<T>, T>;

Implementations

impl<'a, T> Weak<'a, T>

pub fn try_unwrap(self) -> Result<Uninit<'a, ()>, Self>

Try to unwrap the original allocation of the Rc.

This will only work when this is the only pointer to the allocation. That is, there are neither Weak nor Rc still pointing at it.

Example

use without_alloc::{alloc::LocalAllocLeakExt, rc::Rc};
use static_alloc::Bump;

struct Foo;

let slab: Bump<[u8; 1024]> = Bump::uninit();
let rc = slab.rc(Foo).unwrap();
let (_, weak) = Rc::try_unwrap(rc).ok().unwrap();

// This is the only one pointing at the allocation.
let memory = weak.try_unwrap().ok().unwrap();

pub fn upgrade(&self) -> Option<Rc<'a, T>>

Attempt to upgrade to a shared pointer to the value.

This operation will only succeed if there are still strong pointers to the value, i.e. strong_count is not zero. Then the value has not been dropped yet and its lifetime is extended.

use without_alloc::{alloc::LocalAllocLeakExt, rc::Rc};
use static_alloc::Bump;

let memory: Bump<[u8; 1024]> = Bump::uninit();
let rc = memory.rc(0usize).unwrap();

let weak = Rc::downgrade(&rc);
let rc2 = weak.upgrade().unwrap();

drop(rc);
drop(rc2);

// No more strong pointers left.
assert!(weak.upgrade().is_none());

impl<T> Weak<'_, T>

pub fn strong_count(&self) -> usize

Gets the number of strong pointers pointing at the value.

Example

use without_alloc::{alloc::LocalAllocLeakExt, rc::Rc, rc::Weak};
use static_alloc::Bump;

struct Foo;

let slab: Bump<[u8; 1024]> = Bump::uninit();
let rc = slab.rc(Foo).unwrap();
let (_, weak) = Rc::try_unwrap(rc).ok().unwrap();

// We just destroyed the only one.
assert_eq!(Weak::strong_count(&weak), 0);

pub fn weak_count(&self) -> usize

Gets the number of weak pointers pointing at the value.

Example

use without_alloc::{alloc::LocalAllocLeakExt, rc::Rc, rc::Weak};
use static_alloc::Bump;

struct Foo;

let slab: Bump<[u8; 1024]> = Bump::uninit();
let rc = slab.rc(Foo).unwrap();
let (_, weak) = Rc::try_unwrap(rc).ok().unwrap();

// This is the only one pointing at the allocation.
assert_eq!(Weak::weak_count(&weak), 1);

Trait Implementations

impl<T> Clone for Weak<'_, T>

fn clone(&self) -> Self

Clone the Weak.

This will increment the weak reference count.

Examples

use without_alloc::{alloc::LocalAllocLeakExt, rc::Rc};
use static_alloc::Bump;

struct Foo;

let slab: Bump<[u8; 1024]> = Bump::uninit();
let foo = slab.rc(Foo).unwrap();

let (_, weak) = Rc::try_unwrap(foo).ok().unwrap();
assert_eq!(weak.weak_count(), 1);

let weak2 = weak.clone();
assert_eq!(weak.weak_count(), 2);
assert_eq!(weak2.weak_count(), 2);

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

Performs copy-assignment from source.

impl<T> Drop for Weak<'_, T>

fn drop(&mut self)

Executes the destructor for this type.