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

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

This structure is created by the write method on RwLock.

Implementations

Makes a new RwLockMappedWriteGuard 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);

Attempts to make a new RwLockMappedWriteGuard 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);

Converts this RwLockWriteGuard into an RwLockMappedWriteGuard. 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 RwLockWriteGuard::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.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

Formats the value using the given formatter. Read more
The resulting type after dereferencing.
Dereferences the value.
Mutably dereferences the value.
Formats the value using the given formatter. Read more
Executes the destructor for this type. Read more

Auto Trait Implementations

Blanket Implementations

A guard object containing the value and keeping it alive. Read more
The loading method. Read more
Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more
The equivalent of Access::load.

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

Converts the given value to a String. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.