Struct sharded_slab::pool::RefMut
source · [−]pub struct RefMut<'a, T, C = DefaultConfig> where
T: Clear + Default,
C: Config, { /* private fields */ }Expand description
A guard that allows exclusive mutable access to an object in a pool.
While the guard exists, it indicates to the pool that the item the guard references is currently being accessed. If the item is removed from the pool while a guard exists, the removal will be deferred until the guard is dropped. The slot cannot be accessed by other threads while it is accessed mutably.
Implementations
Downgrades the mutable guard to an immutable guard, allowing access to the pooled value from other threads.
Examples
let pool = Arc::new(Pool::<String>::new());
let mut guard_mut = pool.clone().create_owned().unwrap();
let key = guard_mut.key();
guard_mut.push_str("Hello");
// The pooled string is currently borrowed mutably, so other threads
// may not access it.
let pool2 = pool.clone();
thread::spawn(move || {
assert!(pool2.get(key).is_none())
}).join().unwrap();
// Downgrade the guard to an immutable reference.
let guard = guard_mut.downgrade();
// Now, other threads may also access the pooled value.
let pool2 = pool.clone();
thread::spawn(move || {
let guard = pool2.get(key)
.expect("the item may now be referenced by other threads");
assert_eq!(guard, String::from("Hello"));
}).join().unwrap();
// We can still access the value immutably through the downgraded guard.
assert_eq!(guard, String::from("Hello"));