Struct ContractCell

Source

pub struct ContractCell<T: ?Sized>(/* private fields */);

Expand description

A wrapped core::cell::Cell that implements Sync so it can be used in statics. Methods of the inner Cell are available via this wrapper’s Deref implementation. The wrapper adds no costs to Cell.

Note: For static storage that works in the test environment, use the contract_local! macro, e.g.:

contract_local! {
    static VAR: ContractCell<u32> = const { ContractCell::new(0) };
}

(This macro is a no-op in the guest environment.)

Implementations§

Source §

impl<T> ContractCell<T>

Source

pub const fn new(value: T) -> Self

Methods from Deref<Target = Cell<T>>§

1.0.0 · Source

pub fn set(&self, val: T)

Sets the contained value.

§Examples

use std::cell::Cell;

let c = Cell::new(5);

c.set(10);

1.17.0 · Source

pub fn swap(&self, other: &Cell<T>)

Swaps the values of two Cells.

The difference with std::mem::swap is that this function doesn’t require a &mut reference.

§Panics

This function will panic if self and other are different Cells that partially overlap. (Using just standard library methods, it is impossible to create such partially overlapping Cells. However, unsafe code is allowed to e.g. create two &Cell<[i32; 2]> that partially overlap.)

§Examples

use std::cell::Cell;

let c1 = Cell::new(5i32);
let c2 = Cell::new(10i32);
c1.swap(&c2);
assert_eq!(10, c1.get());
assert_eq!(5, c2.get());

1.17.0 · Source

pub fn replace(&self, val: T) -> T

Replaces the contained value with val, and returns the old contained value.

§Examples

use std::cell::Cell;

let cell = Cell::new(5);
assert_eq!(cell.get(), 5);
assert_eq!(cell.replace(10), 5);
assert_eq!(cell.get(), 10);

1.0.0 · Source

pub fn get(&self) -> T

Returns a copy of the contained value.

§Examples

use std::cell::Cell;

let c = Cell::new(5);

let five = c.get();

1.88.0 · Source

pub fn update(&self, f: impl FnOnce(T) -> T)

Updates the contained value using a function.

§Examples

use std::cell::Cell;

let c = Cell::new(5);
c.update(|x| x + 1);
assert_eq!(c.get(), 6);

1.12.0 · Source

pub fn as_ptr(&self) -> *mut T

Returns a raw pointer to the underlying data in this cell.

§Examples

use std::cell::Cell;

let c = Cell::new(5);

let ptr = c.as_ptr();

1.17.0 · Source

pub fn take(&self) -> T
where T: Default,

Takes the value of the cell, leaving Default::default() in its place.

§Examples

use std::cell::Cell;

let c = Cell::new(5);
let five = c.take();

assert_eq!(five, 5);
assert_eq!(c.into_inner(), 0);

Source

pub fn get_cloned(&self) -> Cell<T>

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

Get a clone of the Cell that contains a copy of the original value.

This allows a cheaply Clone-able type like an Rc to be stored in a Cell, exposing the cheaper clone() method.

§Examples

#![feature(cell_get_cloned)]

use core::cell::Cell;
use std::rc::Rc;

let rc = Rc::new(1usize);
let c1 = Cell::new(rc);
let c2 = c1.get_cloned();
assert_eq!(*c2.into_inner(), 1);