Struct tokio::sync::OwnedRwLockMappedWriteGuard
source · pub struct OwnedRwLockMappedWriteGuard<T: ?Sized, U: ?Sized = T> { /* private fields */ }sync only.Expand description
Owned RAII structure used to release the exclusive write access of a lock when dropped.
This structure is created by mapping an OwnedRwLockWriteGuard. It is a
separate type from OwnedRwLockWriteGuard to disallow downgrading a mapped
guard, since doing so can cause undefined behavior.
Implementations§
source§impl<T: ?Sized, U: ?Sized> OwnedRwLockMappedWriteGuard<T, U>
impl<T: ?Sized, U: ?Sized> OwnedRwLockMappedWriteGuard<T, U>
sourcepub fn map<F, V: ?Sized>(this: Self, f: F) -> OwnedRwLockMappedWriteGuard<T, V>where
F: FnOnce(&mut U) -> &mut V,
pub fn map<F, V: ?Sized>(this: Self, f: F) -> OwnedRwLockMappedWriteGuard<T, V>where F: FnOnce(&mut U) -> &mut V,
Makes a new OwnedRwLockMappedWriteGuard for a component of the locked
data.
This operation cannot fail as the OwnedRwLockMappedWriteGuard 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 try_map<F, V: ?Sized>(
this: Self,
f: F
) -> Result<OwnedRwLockMappedWriteGuard<T, V>, Self>where
F: FnOnce(&mut U) -> Option<&mut V>,
pub fn try_map<F, V: ?Sized>( this: Self, f: F ) -> Result<OwnedRwLockMappedWriteGuard<T, V>, Self>where F: FnOnce(&mut U) -> Option<&mut V>,
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 OwnedRwLockMappedWriteGuard passed
in already locked the data.
This is an associated function that needs to be
used as OwnedRwLockMappedWriteGuard::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);