Struct async_std::sync::RwLock

source ·
pub struct RwLock<T>
where 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§

source§

impl<T> RwLock<T>

source

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

Creates a new reader-writer lock.

Examples
use async_lock::RwLock;

let lock = RwLock::new(0);
source

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);
source§

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

source

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());
source

pub async fn read(&self) -> RwLockReadGuard<'_, 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());
source

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;
source

pub async fn upgradable_read(&self) -> RwLockUpgradableReadGuard<'_, T>

Attempts to acquire 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;
source

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());
source

pub async fn write(&self) -> RwLockWriteGuard<'_, 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());
source

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§

source§

impl<T> Debug for RwLock<T>
where T: Debug + ?Sized,

source§

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

Formats the value using the given formatter. Read more
source§

impl<T> Default for RwLock<T>
where T: Default + ?Sized,

source§

fn default() -> RwLock<T>

Returns the “default value” for a type. Read more
source§

impl<T> From<T> for RwLock<T>

source§

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

Converts to this type from the input type.
source§

impl<T> Send for RwLock<T>
where T: Send + ?Sized,

source§

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

Auto Trait Implementations§

§

impl<T> !RefUnwindSafe for RwLock<T>

§

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

§

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

Blanket Implementations§

source§

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

source§

fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
source§

impl<T> Borrow<T> for T
where T: ?Sized,

source§

fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
source§

impl<T> BorrowMut<T> for T
where T: ?Sized,

source§

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

Mutably borrows from an owned value. Read more
source§

impl<T> From<!> for T

source§

fn from(t: !) -> T

Converts to this type from the input type.
source§

impl<T> From<T> for T

source§

fn from(t: T) -> T

Returns the argument unchanged.

source§

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

source§

fn into(self) -> U

Calls U::from(self).

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

source§

impl<T, U> TryFrom<U> for T
where U: Into<T>,

§

type Error = Infallible

The type returned in the event of a conversion error.
source§

fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
source§

impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

§

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

The type returned in the event of a conversion error.
source§

fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.