Struct RwLockUpgradableReadGuard

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

Expand description

A guard that releases the upgradable read lock when dropped.

Implementations§

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impl<'a, T: ?Sized> RwLockUpgradableReadGuard<'a, T>

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pub fn downgrade(guard: Self) -> RwLockReadGuard<'a, T>

Downgrades into a regular reader guard.

§Examples

use async_lock::{RwLock, RwLockUpgradableReadGuard};

let lock = RwLock::new(1);

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

assert!(lock.try_upgradable_read().is_none());

let reader = RwLockUpgradableReadGuard::downgrade(reader);

assert!(lock.try_upgradable_read().is_some());

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pub fn try_upgrade(guard: Self) -> Result<RwLockWriteGuard<'a, T>, Self>

Attempts to upgrade into a write lock.

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

This function can only fail if there are other active read locks.

§Examples

use async_lock::{RwLock, RwLockUpgradableReadGuard};

let lock = RwLock::new(1);

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

let reader2 = lock.read().await;
let reader = RwLockUpgradableReadGuard::try_upgrade(reader).unwrap_err();

drop(reader2);
let writer = RwLockUpgradableReadGuard::try_upgrade(reader).unwrap();

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pub fn upgrade(guard: Self) -> Upgrade<'a, T> ⓘ

Upgrades into a write lock.

§Examples

use async_lock::{RwLock, RwLockUpgradableReadGuard};

let lock = RwLock::new(1);

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

let mut writer = RwLockUpgradableReadGuard::upgrade(reader).await;
*writer = 2;

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pub fn upgrade_blocking(guard: Self) -> RwLockWriteGuard<'a, T>

Upgrades into a write lock.

§Blocking

This function will block the current thread until it is able to acquire the write lock.

§Examples

use async_lock::{RwLock, RwLockUpgradableReadGuard};

let lock = RwLock::new(1);

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

let mut writer = RwLockUpgradableReadGuard::upgrade_blocking(reader);
*writer = 2;