Struct tokio::sync::Semaphore

pub struct Semaphore { /* private fields */ }

Counting semaphore performing asynchronous permit aquisition.

A semaphore maintains a set of permits. Permits are used to synchronize access to a shared resource. A semaphore differs from a mutex in that it can allow more than one concurrent caller to access the shared resource at a time.

When acquire is called and the semaphore has remaining permits, the function immediately returns a permit. However, if no remaining permits are available, acquire (asynchronously) waits until an outstanding permit is dropped. At this point, the freed permit is assigned to the caller.

Implementations

impl Semaphore

pub fn new(permits: usize) -> Self

Creates a new semaphore with the initial number of permits.

pub fn available_permits(&self) -> usize

Returns the current number of available permits.

pub fn add_permits(&self, n: usize)

Adds n new permits to the semaphore.

The maximum number of permits is usize::MAX >> 3, and this function will panic if the limit is exceeded.

pub async fn acquire(&self) -> SemaphorePermit<'_>

Acquires permit from the semaphore.

pub fn try_acquire(&self) -> Result<SemaphorePermit<'_>, TryAcquireError>

Tries to acquire a permit from the semaphore.

pub async fn acquire_owned(self: Arc<Self>) -> OwnedSemaphorePermit

Acquires permit from the semaphore.

The semaphore must be wrapped in an Arc to call this method.

pub fn try_acquire_owned(
    self: Arc<Self>
) -> Result<OwnedSemaphorePermit, TryAcquireError>

Tries to acquire a permit from the semaphore.

The semaphore must be wrapped in an Arc to call this method.

Trait Implementations

impl Debug for Semaphore

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

Formats the value using the given formatter.