Struct tokio::sync::OwnedRwLockWriteGuard [−][src]
pub struct OwnedRwLockWriteGuard<T: ?Sized> { /* fields omitted */ }Expand description
Owned RAII structure used to release the exclusive write access of a lock when dropped.
This structure is created by the write_owned method
on RwLock.
Implementations
Make a new OwnedRwLockMappedWriteGuard for a component of the locked
data.
This operation cannot fail as the OwnedRwLockWriteGuard passed in
already locked the data.
This is an associated function that needs to be used as
OwnedRwLockWriteGuard::map(..). A method would interfere with methods
of the same name on the contents of the locked data.
Examples
use std::sync::Arc;
use tokio::sync::{RwLock, OwnedRwLockWriteGuard};
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
struct Foo(u32);
let lock = Arc::new(RwLock::new(Foo(1)));
{
let lock = Arc::clone(&lock);
let mut mapped = OwnedRwLockWriteGuard::map(lock.write_owned().await, |f| &mut f.0);
*mapped = 2;
}
assert_eq!(Foo(2), *lock.read().await);Attempts to make a new OwnedRwLockMappedWriteGuard for a component
of the locked data. The original guard is returned if the closure
returns None.
This operation cannot fail as the OwnedRwLockWriteGuard passed in
already locked the data.
This is an associated function that needs to be
used as OwnedRwLockWriteGuard::try_map(...). A method would interfere
with methods of the same name on the contents of the locked data.
Examples
use std::sync::Arc;
use tokio::sync::{RwLock, OwnedRwLockWriteGuard};
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
struct Foo(u32);
let lock = Arc::new(RwLock::new(Foo(1)));
{
let guard = Arc::clone(&lock).write_owned().await;
let mut guard = OwnedRwLockWriteGuard::try_map(guard, |f| Some(&mut f.0)).expect("should not fail");
*guard = 2;
}
assert_eq!(Foo(2), *lock.read().await);Converts this OwnedRwLockWriteGuard into an
OwnedRwLockMappedWriteGuard. This method can be used to store a
non-mapped guard in a struct field that expects a mapped guard.
This is equivalent to calling OwnedRwLockWriteGuard::map(guard, |me| me).
Atomically downgrades a write lock into a read lock without allowing any writers to take exclusive access of the lock in the meantime.
Note: This won’t necessarily allow any additional readers to acquire
locks, since RwLock is fair and it is possible that a writer is next
in line.
Returns an RAII guard which will drop this read access of the RwLock
when dropped.
Examples
let lock = Arc::new(RwLock::new(1));
let n = lock.clone().write_owned().await;
let cloned_lock = lock.clone();
let handle = tokio::spawn(async move {
*cloned_lock.write_owned().await = 2;
});
let n = n.downgrade();
assert_eq!(*n, 1, "downgrade is atomic");
drop(n);
handle.await.unwrap();
assert_eq!(*lock.read().await, 2, "second writer obtained write lock");