Struct async_lock::RwLock

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

An async reader-writer lock.

This type of lock allows multiple readers or one writer at any point in time.

The locking strategy is write-preferring, which means writers are never starved. Releasing a write lock wakes the next blocked reader and the next blocked writer.

Examples

use async_lock::RwLock;

let lock = RwLock::new(5);

// Multiple read locks can be held at a time.
let r1 = lock.read().await;
let r2 = lock.read().await;
assert_eq!(*r1, 5);
assert_eq!(*r2, 5);
drop((r1, r2));

// Only one write lock can be held at a time.
let mut w = lock.write().await;
*w += 1;
assert_eq!(*w, 6);

Implementations§

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impl<T> RwLock<T>

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pub const fn new(t: T) -> RwLock<T>

Creates a new reader-writer lock.

Examples
use async_lock::RwLock;

let lock = RwLock::new(0);
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pub fn into_inner(self) -> T

Unwraps the lock and returns the inner value.

Examples
use async_lock::RwLock;

let lock = RwLock::new(5);
assert_eq!(lock.into_inner(), 5);
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pub fn try_read_arc(self: &Arc<Self>) -> Option<RwLockReadGuardArc<T>>

Attempts to acquire an an owned, reference-counted read lock.

If a read lock could not be acquired at this time, then None is returned. Otherwise, a guard is returned that releases the lock when dropped.

Examples
use std::sync::Arc;
use async_lock::RwLock;

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

let reader = lock.read_arc().await;
assert_eq!(*reader, 1);

assert!(lock.try_read_arc().is_some());
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pub fn read_arc<'a>(self: &'a Arc<Self>) -> ReadArc<'a, T>

Acquires an owned, reference-counted read lock.

Returns a guard that releases the lock when dropped.

Note that attempts to acquire a read lock will block if there are also concurrent attempts to acquire a write lock.

Examples
use std::sync::Arc;
use async_lock::RwLock;

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

let reader = lock.read_arc().await;
assert_eq!(*reader, 1);

assert!(lock.try_read_arc().is_some());
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impl<T: ?Sized> RwLock<T>

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pub fn try_read(&self) -> Option<RwLockReadGuard<'_, T>>

Attempts to acquire a read lock.

If a read lock could not be acquired at this time, then None is returned. Otherwise, a guard is returned that releases the lock when dropped.

Examples
use async_lock::RwLock;

let lock = RwLock::new(1);

let reader = lock.read().await;
assert_eq!(*reader, 1);

assert!(lock.try_read().is_some());
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pub fn read(&self) -> Read<'_, T>

Acquires a read lock.

Returns a guard that releases the lock when dropped.

Note that attempts to acquire a read lock will block if there are also concurrent attempts to acquire a write lock.

Examples
use async_lock::RwLock;

let lock = RwLock::new(1);

let reader = lock.read().await;
assert_eq!(*reader, 1);

assert!(lock.try_read().is_some());
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pub fn try_upgradable_read(&self) -> Option<RwLockUpgradableReadGuard<'_, T>>

Attempts to acquire a read lock with the possiblity to upgrade to a write lock.

If a read lock could not be acquired at this time, then None is returned. Otherwise, a guard is returned that releases the lock when dropped.

Upgradable read lock reserves the right to be upgraded to a write lock, which means there can be at most one upgradable read lock at a time.

Examples
use async_lock::{RwLock, RwLockUpgradableReadGuard};

let lock = RwLock::new(1);

let reader = lock.upgradable_read().await;
assert_eq!(*reader, 1);
assert_eq!(*lock.try_read().unwrap(), 1);

let mut writer = RwLockUpgradableReadGuard::upgrade(reader).await;
*writer = 2;
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pub fn upgradable_read(&self) -> UpgradableRead<'_, T>

Acquires a read lock with the possiblity to upgrade to a write lock.

Returns a guard that releases the lock when dropped.

Upgradable read lock reserves the right to be upgraded to a write lock, which means there can be at most one upgradable read lock at a time.

Note that attempts to acquire an upgradable read lock will block if there are concurrent attempts to acquire another upgradable read lock or a write lock.

Examples
use async_lock::{RwLock, RwLockUpgradableReadGuard};

let lock = RwLock::new(1);

let reader = lock.upgradable_read().await;
assert_eq!(*reader, 1);
assert_eq!(*lock.try_read().unwrap(), 1);

let mut writer = RwLockUpgradableReadGuard::upgrade(reader).await;
*writer = 2;
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pub fn try_upgradable_read_arc( self: &Arc<Self> ) -> Option<RwLockUpgradableReadGuardArc<T>>

Attempts to acquire an owned, reference-counted read lock with the possiblity to upgrade to a write lock.

If a read lock could not be acquired at this time, then None is returned. Otherwise, a guard is returned that releases the lock when dropped.

Upgradable read lock reserves the right to be upgraded to a write lock, which means there can be at most one upgradable read lock at a time.

Examples
use std::sync::Arc;
use async_lock::{RwLock, RwLockUpgradableReadGuardArc};

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

let reader = lock.upgradable_read_arc().await;
assert_eq!(*reader, 1);
assert_eq!(*lock.try_read_arc().unwrap(), 1);

let mut writer = RwLockUpgradableReadGuardArc::upgrade(reader).await;
*writer = 2;
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pub fn upgradable_read_arc<'a>(self: &'a Arc<Self>) -> UpgradableReadArc<'a, T>

Acquires an owned, reference-counted read lock with the possiblity to upgrade to a write lock.

Returns a guard that releases the lock when dropped.

Upgradable read lock reserves the right to be upgraded to a write lock, which means there can be at most one upgradable read lock at a time.

Note that attempts to acquire an upgradable read lock will block if there are concurrent attempts to acquire another upgradable read lock or a write lock.

Examples
use std::sync::Arc;
use async_lock::{RwLock, RwLockUpgradableReadGuardArc};

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

let reader = lock.upgradable_read_arc().await;
assert_eq!(*reader, 1);
assert_eq!(*lock.try_read_arc().unwrap(), 1);

let mut writer = RwLockUpgradableReadGuardArc::upgrade(reader).await;
*writer = 2;
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pub fn try_write(&self) -> Option<RwLockWriteGuard<'_, T>>

Attempts to acquire a write lock.

If a write lock could not be acquired at this time, then None is returned. Otherwise, a guard is returned that releases the lock when dropped.

Examples
use async_lock::RwLock;

let lock = RwLock::new(1);

assert!(lock.try_write().is_some());
let reader = lock.read().await;
assert!(lock.try_write().is_none());
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pub fn write(&self) -> Write<'_, T>

Acquires a write lock.

Returns a guard that releases the lock when dropped.

Examples
use async_lock::RwLock;

let lock = RwLock::new(1);

let writer = lock.write().await;
assert!(lock.try_read().is_none());
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pub fn try_write_arc(self: &Arc<Self>) -> Option<RwLockWriteGuardArc<T>>

Attempts to acquire an owned, reference-counted write lock.

If a write lock could not be acquired at this time, then None is returned. Otherwise, a guard is returned that releases the lock when dropped.

Examples
use std::sync::Arc;
use async_lock::RwLock;

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

assert!(lock.try_write_arc().is_some());
let reader = lock.read_arc().await;
assert!(lock.try_write_arc().is_none());
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pub fn write_arc<'a>(self: &'a Arc<Self>) -> WriteArc<'a, T>

Acquires an owned, reference-counted write lock.

Returns a guard that releases the lock when dropped.

Examples
use std::sync::Arc;
use async_lock::RwLock;

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

let writer = lock.write_arc().await;
assert!(lock.try_read_arc().is_none());
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pub fn get_mut(&mut self) -> &mut T

Returns a mutable reference to the inner value.

Since this call borrows the lock mutably, no actual locking takes place. The mutable borrow statically guarantees no locks exist.

Examples
use async_lock::RwLock;

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

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

Trait Implementations§

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impl<T: Debug + ?Sized> Debug for RwLock<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: Default + ?Sized> Default for RwLock<T>

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fn default() -> RwLock<T>

Returns the “default value” for a type. Read more
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impl<T> From<T> for RwLock<T>

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fn from(val: T) -> RwLock<T>

Converts to this type from the input type.
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impl<T: Send + ?Sized> Send for RwLock<T>

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impl<T: Send + Sync + ?Sized> Sync for RwLock<T>

Auto Trait Implementations§

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impl<T> !RefUnwindSafe for RwLock<T>

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impl<T: ?Sized> Unpin for RwLock<T>where T: Unpin,

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impl<T: ?Sized> UnwindSafe for RwLock<T>where T: UnwindSafe,

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<!> for T

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fn from(t: !) -> T

Converts to this type from the input type.
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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, 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.