Struct tokio::sync::OwnedRwLockWriteGuard
source · pub struct OwnedRwLockWriteGuard<T: ?Sized> { /* private fields */ }
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§
source§impl<T: ?Sized> OwnedRwLockWriteGuard<T>
impl<T: ?Sized> OwnedRwLockWriteGuard<T>
sourcepub fn map<F, U: ?Sized>(this: Self, f: F) -> OwnedRwLockMappedWriteGuard<T, U>
pub fn map<F, U: ?Sized>(this: Self, f: F) -> OwnedRwLockMappedWriteGuard<T, U>
Makes 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);
sourcepub fn downgrade_map<F, U: ?Sized>(
this: Self,
f: F,
) -> OwnedRwLockReadGuard<T, U>
pub fn downgrade_map<F, U: ?Sized>( this: Self, f: F, ) -> OwnedRwLockReadGuard<T, U>
Makes a new OwnedRwLockReadGuard
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::downgrade_map(..)
. A method would interfere with methods of
the same name on the contents of the locked data.
Inside of f
, you retain exclusive access to the data, despite only being given a &T
. Handing out a
&mut T
would result in unsoundness, as you could use interior mutability.
§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 mapped = OwnedRwLockWriteGuard::downgrade_map(guard, |f| &f.0);
let foo = lock.read_owned().await;
assert_eq!(foo.0, *mapped);
sourcepub fn try_map<F, U: ?Sized>(
this: Self,
f: F,
) -> Result<OwnedRwLockMappedWriteGuard<T, U>, Self>
pub fn try_map<F, U: ?Sized>( this: Self, f: F, ) -> Result<OwnedRwLockMappedWriteGuard<T, U>, Self>
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);
sourcepub fn try_downgrade_map<F, U: ?Sized>(
this: Self,
f: F,
) -> Result<OwnedRwLockReadGuard<T, U>, Self>
pub fn try_downgrade_map<F, U: ?Sized>( this: Self, f: F, ) -> Result<OwnedRwLockReadGuard<T, U>, Self>
Attempts to make a new OwnedRwLockReadGuard
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_downgrade_map(...)
. A method would interfere with
methods of the same name on the contents of the locked data.
Inside of f
, you retain exclusive access to the data, despite only being given a &T
. Handing out a
&mut T
would result in unsoundness, as you could use interior mutability.
If this function returns Err(...)
, the lock is never unlocked nor downgraded.
§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 guard = OwnedRwLockWriteGuard::try_downgrade_map(guard, |f| Some(&f.0)).expect("should not fail");
let foo = lock.read_owned().await;
assert_eq!(foo.0, *guard);
sourcepub fn into_mapped(this: Self) -> OwnedRwLockMappedWriteGuard<T>
pub fn into_mapped(this: Self) -> OwnedRwLockMappedWriteGuard<T>
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)
.
sourcepub fn downgrade(self) -> OwnedRwLockReadGuard<T>
pub fn downgrade(self) -> OwnedRwLockReadGuard<T>
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");
sourcepub fn rwlock(this: &Self) -> &Arc<RwLock<T>>
pub fn rwlock(this: &Self) -> &Arc<RwLock<T>>
Returns a reference to the original Arc<RwLock>
.
§Examples
use std::sync::Arc;
use tokio::sync::{RwLock, OwnedRwLockWriteGuard};
let lock = Arc::new(RwLock::new(1));
let guard = lock.clone().write_owned().await;
assert!(Arc::ptr_eq(&lock, OwnedRwLockWriteGuard::rwlock(&guard)));