8 stable releases
Uses old Rust 2015
2.1.0 | Dec 12, 2020 |
---|---|
2.0.3 | Jun 24, 2020 |
2.0.2 | Jul 27, 2019 |
2.0.1 | Dec 1, 2018 |
1.0.0 | Nov 2, 2017 |
#1150 in Concurrency
627 downloads per month
Used in 4 crates
(3 directly)
19KB
153 lines
double-checked-cell
A thread-safe lazily initialized cell using double-checked locking.
Deprecated
You should probably use once_cell instead of this crate. It provides a superset of this crate's functionality, with a nicely consistent API. Its functionality is also being considered for inclusion in the standard library.
Introduction
Provides a memory location that can be safely shared between threads and initialized at most once. Once the cell is initialized it becomes immutable.
If you do not need to change the value after initialization
DoubleCheckedCell<T>
is more efficient than a Mutex<Option<T>>
.
extern crate double_checked_cell;
use double_checked_cell::DoubleCheckedCell;
fn main() {
let cell = DoubleCheckedCell::new();
// The cell starts uninitialized.
assert_eq!(cell.get(), None);
// Perform potentially expensive initialization.
let value = cell.get_or_init(|| 21 + 21);
assert_eq!(*value, 42);
assert_eq!(cell.get(), Some(&42));
// The cell is already initialized.
let value = cell.get_or_init(|| unreachable!());
assert_eq!(*value, 42);
assert_eq!(cell.get(), Some(&42));
}
Related crates
- once_cell – See above.
These crates are similar but distinct by design:
- lazy-init – Based on a
LazyTransform<T, U>
which can lazily consumeT
to produce anU
. Therefore cannot support fallible initialization. - lazycell –
AtomicLazyCell
does not support lazy initialization (unlike its non-thread-safe counterpartLazyCell
usingLazyCell::borrow_with()
). - mitochondria – Not
Sync
. - lazy_static - With the optional (currently nightly only)
const_fn
feature,DoubleCheckedCell::new()
can also be used in static/const context. Howeverlazy_static!
is more convenient when there is only a single way to initialize the cell.
Documentation
Changelog
- 2.1.0
- Fix
UnwindSafe
andRefUnwindSafe
bounds. This is technically a breaking change, but published under the same major version because it is a bugfix.
- Fix
- 2.0.3
- Update to parking_lot 0.11.
- 2.0.2
- Update to parking_lot 0.9.
- 2.0.1
- Update to parking_lot 0.7.
- 2.0.0
- Changed unwinding behavior:
DoubleCheckedCell
no longer implements poisoning. - New optional cargo features:
parking_lot_mutex
,const_fn
.
- Changed unwinding behavior:
- 1.1.0
- Fix unsoundness:
DoubleCheckedCell<T>
whereT: !Send
cannot beSync
.
- Fix unsoundness:
- 1.0.1
- Ignore
unused_unsafe
warning due toUnsafeCell::into_inner()
no longer beeing unsafe.
- Ignore
- 1.0.0
- Initial release.
License
double-checked-cell is licensed under the Apache 2.0 and MIT license, at your option.
Dependencies
~10–315KB