Struct tokio::sync::OwnedMutexGuard

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pub struct OwnedMutexGuard<T: ?Sized> { /* private fields */ }
Expand description

An owned handle to a held Mutex.

This guard is only available from a Mutex that is wrapped in an Arc. It is identical to MutexGuard, except that rather than borrowing the Mutex, it clones the Arc, incrementing the reference count. This means that unlike MutexGuard, it will have the 'static lifetime.

As long as you have this guard, you have exclusive access to the underlying T. The guard internally keeps a reference-counted pointer to the original Mutex, so even if the lock goes away, the guard remains valid.

The lock is automatically released whenever the guard is dropped, at which point lock will succeed yet again.

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impl<T: ?Sized> OwnedMutexGuard<T>

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pub fn map<U, F>(this: Self, f: F) -> OwnedMappedMutexGuard<T, U>where F: FnOnce(&mut T) -> &mut U,

Makes a new OwnedMappedMutexGuard for a component of the locked data.

This operation cannot fail as the OwnedMutexGuard passed in already locked the mutex.

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

Examples
use tokio::sync::{Mutex, OwnedMutexGuard};
use std::sync::Arc;

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

let foo = Arc::new(Mutex::new(Foo(1)));

{
    let mut mapped = OwnedMutexGuard::map(foo.clone().lock_owned().await, |f| &mut f.0);
    *mapped = 2;
}

assert_eq!(Foo(2), *foo.lock().await);
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pub fn try_map<U, F>( this: Self, f: F ) -> Result<OwnedMappedMutexGuard<T, U>, Self>where F: FnOnce(&mut T) -> Option<&mut U>,

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

This operation cannot fail as the OwnedMutexGuard passed in already locked the mutex.

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

Examples
use tokio::sync::{Mutex, OwnedMutexGuard};
use std::sync::Arc;

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

let foo = Arc::new(Mutex::new(Foo(1)));

{
    let mut mapped = OwnedMutexGuard::try_map(foo.clone().lock_owned().await, |f| Some(&mut f.0))
        .expect("should not fail");
    *mapped = 2;
}

assert_eq!(Foo(2), *foo.lock().await);
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pub fn mutex(this: &Self) -> &Arc<Mutex<T>>

Returns a reference to the original Arc<Mutex>.

use std::sync::Arc;
use tokio::sync::{Mutex, OwnedMutexGuard};

async fn unlock_and_relock(guard: OwnedMutexGuard<u32>) -> OwnedMutexGuard<u32> {
    println!("1. contains: {:?}", *guard);
    let mutex: Arc<Mutex<u32>> = OwnedMutexGuard::mutex(&guard).clone();
    drop(guard);
    let guard = mutex.lock_owned().await;
    println!("2. contains: {:?}", *guard);
    guard
}

Trait Implementations§

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impl<T: ?Sized + Debug> Debug for OwnedMutexGuard<T>

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl<T: ?Sized> Deref for OwnedMutexGuard<T>

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type Target = T

The resulting type after dereferencing.
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fn deref(&self) -> &Self::Target

Dereferences the value.
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impl<T: ?Sized> DerefMut for OwnedMutexGuard<T>

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fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.
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impl<T: ?Sized + Display> Display for OwnedMutexGuard<T>

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl<T: ?Sized> Drop for OwnedMutexGuard<T>

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fn drop(&mut self)

Executes the destructor for this type. Read more
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impl<T> Sync for OwnedMutexGuard<T>where T: ?Sized + Send + Sync,

Auto Trait Implementations§

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impl<T> !RefUnwindSafe for OwnedMutexGuard<T>

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impl<T: ?Sized> Send for OwnedMutexGuard<T>where T: Send,

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impl<T: ?Sized> Unpin for OwnedMutexGuard<T>

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impl<T> !UnwindSafe for OwnedMutexGuard<T>

Blanket Implementations§

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impl<T> Any for Twhere T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for Twhere T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for Twhere T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T, U> Into<U> for Twhere U: From<T>,

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fn into(self) -> U

Calls U::from(self).

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

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impl<T> ToString for Twhere T: Display + ?Sized,

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default fn to_string(&self) -> String

Converts the given value to a String. Read more
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impl<T, U> TryFrom<U> for Twhere U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for Twhere U: TryFrom<T>,

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

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.