Struct tokio::sync::SemaphorePermit

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pub struct SemaphorePermit<'a> { /* private fields */ }
Expand description

A permit from the semaphore.

This type is created by the acquire method.

Implementations§

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impl<'a> SemaphorePermit<'a>

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

Merge two SemaphorePermit 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.try_acquire().unwrap();

for _ in 0..9 {
    let _permit = sem.try_acquire().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 SemaphorePermit instance that holds n permits.

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

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

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

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

assert_eq!(p1.num_permits(), 2);
assert_eq!(p2.num_permits(), 1);
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pub fn num_permits(&self) -> usize

Returns the number of permits held by self.

Trait Implementations§

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impl<'a> Debug for SemaphorePermit<'a>

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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 Drop for SemaphorePermit<'_>

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fn drop(&mut self)

Executes the destructor for this type. Read more

Auto Trait Implementations§

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impl<'a> Freeze for SemaphorePermit<'a>

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impl<'a> !RefUnwindSafe for SemaphorePermit<'a>

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impl<'a> Send for SemaphorePermit<'a>

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impl<'a> Sync for SemaphorePermit<'a>

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impl<'a> Unpin for SemaphorePermit<'a>

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impl<'a> !UnwindSafe for SemaphorePermit<'a>

Blanket Implementations§

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impl<T> Any for T
where 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 T
where 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 T
where 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 T
where 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 T
where 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 T
where 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.