Struct bones_lib::prelude::Ref

pub struct Ref<'a, T>where
    T: ?Sized,
{ /* private fields */ }

Expand description

Wrapper for a borrowed AtomicCell that will released lock on drop.

This type can be dereferenced to &T.

Implements Borrow<T> and AsRef<T> for convenience.

Implements Debug, Display, PartialEq, PartialOrd and Hash by delegating to T.

Implementations§

§

impl<'a, T> Ref<'a, T>
where T: ?Sized,

pub fn new(r: &'a T) -> Ref<'a, T>

Wraps external reference into Ref.

This function’s purpose is to satisfy type requirements where Ref is required but reference does not live in AtomicCell.

§Examples

use atomicell::Ref;

let r = Ref::new(&42);

pub fn with_borrow(r: &'a T, borrow: AtomicBorrow<'a>) -> Ref<'a, T>

Wraps external reference into Ref. And associates it with provided AtomicBorrow

This function is intended to be used by AtomicCell or other abstractions that use AtomicBorrow for locking.

§Examples

use core::sync::atomic::AtomicIsize;
use atomicell::{borrow::{AtomicBorrow, new_lock}, Ref};
let counter = new_lock();
let borrow = AtomicBorrow::try_new(&counter).unwrap();

let r = Ref::with_borrow(&42, borrow);
assert_eq!(*r, 42);

pub fn into_split(r: Ref<'a, T>) -> (NonNull<T>, AtomicBorrow<'a>)

Splits wrapper into two parts. One is reference to the value and the other is AtomicBorrow that guards it from being borrowed mutably.

§Safety

User must ensure NonNull is not dereferenced after AtomicBorrow is dropped.

Also, the NonNull<T> that is returned is still only valid for reads, not writes.

§Examples

use atomicell::{AtomicCell, Ref};

let cell = AtomicCell::new(42);
let r: Ref<'_, i32> = cell.borrow();

unsafe {
    let (r, borrow) = Ref::into_split(r);
    assert_eq!(*r.as_ref(), 42);

    assert!(cell.try_borrow().is_some(), "Must be able to borrow immutably");
    assert!(cell.try_borrow_mut().is_none(), "Must not be able to borrow mutably yet");
    drop(borrow);
    assert!(cell.try_borrow_mut().is_some(), "Must be able to borrow mutably now");
}

pub fn map<F, U>(r: Ref<'a, T>, f: F) -> Ref<'a, U>
where F: FnOnce(&T) -> &U, U: ?Sized,

Makes a new Ref for a component of the borrowed data.

The AtomicCell is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as Ref::map(…). A method would interfere with methods of the same name on the contents of a AtomicCell used through Deref.

§Examples

use atomicell::{AtomicCell, Ref};

let c = AtomicCell::new((5, 'b'));
let b1: Ref<(u32, char)> = c.borrow();
let b2: Ref<u32> = Ref::map(b1, |t| &t.0);
assert_eq!(*b2, 5)

pub fn filter_map<U, F>(r: Ref<'a, T>, f: F) -> Result<Ref<'a, U>, Ref<'a, T>>
where F: FnOnce(&T) -> Option<&U>, U: ?Sized,

Makes a new Ref for an optional component of the borrowed data. The original guard is returned as an Err(..) if the closure returns None.

The AtomicCell is already mutably borrowed, so this cannot fail.

This is an associated function that needs to be used as Ref::filter_map(…). A method would interfere with methods of the same name on the contents of a AtomicCell used through Deref.

§Examples

use atomicell::{AtomicCell, Ref};
let c = AtomicCell::new(vec![1, 2, 3]);
let b1: Ref<Vec<u32>> = c.borrow();
let b2: Result<Ref<u32>, _> = Ref::filter_map(b1, |v| v.get(1));
assert_eq!(*b2.unwrap(), 2);

pub fn map_split<U, V, F>(r: Ref<'a, T>, f: F) -> (Ref<'a, U>, Ref<'a, V>)
where F: FnOnce(&T) -> (&U, &V), U: ?Sized, V: ?Sized,

Splits a Ref into multiple Refs for different components of the borrowed data.

The AtomicCell is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as Ref::map_split(...). A method would interfere with methods of the same name on the contents of a AtomicCell used through Deref.

§Examples

use atomicell::{Ref, AtomicCell};

let cell = AtomicCell::new([1, 2, 3, 4]);
let borrow = cell.borrow();
let (begin, end) = Ref::map_split(borrow, |slice| slice.split_at(2));
assert_eq!(*begin, [1, 2]);
assert_eq!(*end, [3, 4]);

pub fn leak(r: Ref<'a, T>) -> &'a T

Convert into a reference to the underlying data.

The underlying AtomicCell can never be mutably borrowed from again and will always appear already immutably borrowed. It is not a good idea to leak more than a constant number of references. The AtomicCell can be immutably borrowed again if only a smaller number of leaks have occurred in total.

This is an associated function that needs to be used as Ref::leak(…). A method would interfere with methods of the same name on the contents of a AtomicCell used through Deref.

§Examples

use atomicell::{AtomicCell, Ref};
let cell = AtomicCell::new(0);

let value = Ref::leak(cell.borrow());
assert_eq!(*value, 0);

assert!(cell.try_borrow().is_some());
assert!(cell.try_borrow_mut().is_none());

pub fn as_ref(r: Ref<'a, T>) -> Ref<'a, U>
where T: AsRef, U: ?Sized,

Converts reference and returns result wrapped in the Ref.

The AtomicCell is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as Ref::map_split(...). A method would interfere with methods of the same name on the contents of a AtomicCell used through Deref.

§Examples

use atomicell::{AtomicCell, Ref};

let c = AtomicCell::new(String::from("hello"));
let b1: Ref<String> = c.borrow();
let b2: Ref<str> = Ref::as_ref(b1);
assert_eq!(*b2, *"hello")

pub fn as_deref(r: Ref<'a, T>) -> Ref<'a, <T as Deref>::Target>
where T: Deref,

Dereferences and returns result wrapped in the Ref.

The AtomicCell is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as Ref::map_split(...). A method would interfere with methods of the same name on the contents of a AtomicCell used through Deref.

§Examples

use atomicell::{AtomicCell, Ref};

let c = AtomicCell::new(String::from("hello"));
let b1: Ref<String> = c.borrow();
let b2: Ref<str> = Ref::as_deref(b1);
assert_eq!(*b2, *"hello")

§

impl<'a, T> Ref<'a, Option<T>>

pub fn transpose(r: Ref<'a, Option<T>>) -> Option<Ref<'a, T>>

Transposes a Ref of an Option into an Option of a Ref. Releases shared lock of AtomicCell if the value is None.

The AtomicCell is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as Ref::map_split(...). A method would interfere with methods of the same name on the contents of a AtomicCell used through Deref.

§Examples

use atomicell::{AtomicCell, Ref};

let c = AtomicCell::new(Some(5));
let b1: Ref<Option<i32>> = c.borrow();
let b2: Option<Ref<i32>> = Ref::transpose(b1);
assert!(b2.is_some());

let c = AtomicCell::new(None);
let b1: Ref<Option<i32>> = c.borrow();
let b2: Option<Ref<i32>> = Ref::transpose(b1);
assert!(b2.is_none());
assert!(c.try_borrow_mut().is_some());

§

impl<'a, T> Ref<'a, [T]>

pub fn slice<R>(r: Ref<'a, [T]>, range: R) -> Ref<'a, [T]>
where R: RangeBounds<usize>,

Makes a new Ref for a sub-slice of the borrowed slice.

The AtomicCell is already immutably borrowed, so this cannot fail.

This is an associated function that needs to be used as Ref::map(…). A method would interfere with methods of the same name on the contents of a AtomicCell used through Deref.

§Examples

use atomicell::{AtomicCell, Ref};

let c: &AtomicCell<[i32]> = &AtomicCell::new([1, 2, 3, 4, 5]);
let b1: Ref<[i32]> = c.borrow();
let b2: Ref<[i32]> = Ref::slice(b1, 2..4);
assert_eq!(*b2, [3, 4])