Struct tokio::sync::semaphore::OwnedSemaphorePermit

source ·

pub struct OwnedSemaphorePermit {
    sem: Arc<Semaphore>,
    permits: u32,
}

Expand description

An owned permit from the semaphore.

This type is created by the acquire_owned method.

Fields§

§sem: Arc<Semaphore>§permits: u32

Implementations§

source §

impl OwnedSemaphorePermit

source

pub fn forget(self)

Forgets the permit without releasing it back to the semaphore. This can be used to reduce the amount of permits available from a semaphore.

§Examples

use std::sync::Arc;
use tokio::sync::Semaphore;

let sem = Arc::new(Semaphore::new(10));
{
    let permit = sem.clone().try_acquire_many_owned(5).unwrap();
    assert_eq!(sem.available_permits(), 5);
    permit.forget();
}

// Since we forgot the permit, available permits won't go back to its initial value
// even after the permit is dropped.
assert_eq!(sem.available_permits(), 5);

source

pub fn merge(&mut self, other: Self)

Merge two OwnedSemaphorePermit instances together, consuming other without releasing the permits it holds.

Permits held by both self and other are released when self drops.

§Panics

This function panics if permits from different Semaphore instances are merged.

§Examples

use std::sync::Arc;
use tokio::sync::Semaphore;

let sem = Arc::new(Semaphore::new(10));
let mut permit = sem.clone().try_acquire_owned().unwrap();

for _ in 0..9 {
    let _permit = sem.clone().try_acquire_owned().unwrap();
    // Merge individual permits into a single one.
    permit.merge(_permit)
}

assert_eq!(sem.available_permits(), 0);

// Release all permits in a single batch.
drop(permit);

assert_eq!(sem.available_permits(), 10);

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pub fn split(&mut self, n: usize) -> Option<Self>

Splits n permits from self and returns a new OwnedSemaphorePermit instance that holds n permits.

If there are insufficient permits and it’s not possible to reduce by n, returns None.

§Note

It will clone the owned Arc<Semaphore> to construct the new instance.

§Examples

use std::sync::Arc;
use tokio::sync::Semaphore;

let sem = Arc::new(Semaphore::new(3));

let mut p1 = sem.try_acquire_many_owned(3).unwrap();
let p2 = p1.split(1).unwrap();

assert_eq!(p1.num_permits(), 2);
assert_eq!(p2.num_permits(), 1);