Struct tokio::sync::RwLockWriteGuard[][src]

pub struct RwLockWriteGuard<'a, T: ?Sized> { /* fields omitted */ }

RAII structure used to release the exclusive write access of a lock when dropped.

This structure is created by the write and method on RwLock.

Implementations

impl<'a, T: ?Sized> RwLockWriteGuard<'a, T>[src]

pub fn map<F, U: ?Sized>(this: Self, f: F) -> RwLockWriteGuard<'a, U> where
    F: FnOnce(&mut T) -> &mut U, 
[src]

Make a new RwLockWriteGuard for a component of the locked data.

This operation cannot fail as the RwLockWriteGuard passed in already locked the data.

This is an associated function that needs to be used as RwLockWriteGuard::map(..). A method would interfere with methods of the same name on the contents of the locked data.

This is an asynchronous version of RwLockWriteGuard::map from the parking_lot crate.

Examples

use tokio::sync::{RwLock, RwLockWriteGuard};

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
struct Foo(u32);

let lock = RwLock::new(Foo(1));

{
    let mut mapped = RwLockWriteGuard::map(lock.write().await, |f| &mut f.0);
    *mapped = 2;
}

assert_eq!(Foo(2), *lock.read().await);

pub fn try_map<F, U: ?Sized>(
    this: Self,
    f: F
) -> Result<RwLockWriteGuard<'a, U>, Self> where
    F: FnOnce(&mut T) -> Option<&mut U>, 
[src]

Attempts to make a new RwLockWriteGuard for a component of the locked data. The original guard is returned if the closure returns None.

This operation cannot fail as the RwLockWriteGuard passed in already locked the data.

This is an associated function that needs to be used as RwLockWriteGuard::try_map(...). A method would interfere with methods of the same name on the contents of the locked data.

This is an asynchronous version of RwLockWriteGuard::try_map from the parking_lot crate.

Examples

use tokio::sync::{RwLock, RwLockWriteGuard};

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
struct Foo(u32);

let lock = RwLock::new(Foo(1));

{
    let guard = lock.write().await;
    let mut guard = RwLockWriteGuard::try_map(guard, |f| Some(&mut f.0)).expect("should not fail");
    *guard = 2;
}

assert_eq!(Foo(2), *lock.read().await);

pub fn downgrade(self) -> RwLockReadGuard<'a, T>[src]

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 the read access of this rwlock when dropped.

Examples

let lock = Arc::new(RwLock::new(1));

let n = lock.write().await;
   
let cloned_lock = lock.clone();
let handle = tokio::spawn(async move {
    *cloned_lock.write().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");

Trait Implementations

impl<'a, T: ?Sized> Debug for RwLockWriteGuard<'a, T> where
    T: Debug
[src]

impl<T: ?Sized> Deref for RwLockWriteGuard<'_, T>[src]

type Target = T

The resulting type after dereferencing.

impl<T: ?Sized> DerefMut for RwLockWriteGuard<'_, T>[src]

impl<'a, T: ?Sized> Display for RwLockWriteGuard<'a, T> where
    T: Display
[src]

impl<'a, T: ?Sized> Drop for RwLockWriteGuard<'a, T>[src]

impl<T: ?Sized> Send for RwLockWriteGuard<'_, T> where
    T: Send + Sync
[src]

impl<T: ?Sized> Sync for RwLockWriteGuard<'_, T> where
    T: Send + Sync
[src]

Auto Trait Implementations

impl<'a, T> !RefUnwindSafe for RwLockWriteGuard<'a, T>

impl<'a, T: ?Sized> Unpin for RwLockWriteGuard<'a, T>

impl<'a, T> !UnwindSafe for RwLockWriteGuard<'a, T>

Blanket Implementations

impl<T> Any for T where
    T: 'static + ?Sized
[src]

impl<T> Borrow<T> for T where
    T: ?Sized
[src]

impl<T> BorrowMut<T> for T where
    T: ?Sized
[src]

impl<T> From<T> for T[src]

impl<T, U> Into<U> for T where
    U: From<T>, 
[src]

impl<T> ToString for T where
    T: Display + ?Sized
[src]

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 
[src]

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 
[src]

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.