Struct tokio_util::sync::PollSemaphore

pub struct PollSemaphore {
    semaphore: Arc<Semaphore>,
    permit_fut: Option<(u32, ReusableBoxFuture<'static, Result<OwnedSemaphorePermit, AcquireError>>)>,
}

A wrapper around Semaphore that provides a poll_acquire method.

Fields

semaphore: Arc<Semaphore>

permit_fut: Option<(u32, ReusableBoxFuture<'static, Result<OwnedSemaphorePermit, AcquireError>>)>

Implementations

impl PollSemaphore

pub fn new(semaphore: Arc<Semaphore>) -> Self

Create a new PollSemaphore.

pub fn close(&self)

Closes the semaphore.

pub fn clone_inner(&self) -> Arc<Semaphore>

Obtain a clone of the inner semaphore.

pub fn into_inner(self) -> Arc<Semaphore>

Get back the inner semaphore.

pub fn poll_acquire( &mut self, cx: &mut Context<'_>, ) -> Poll<Option<OwnedSemaphorePermit>>

Poll to acquire a permit from the semaphore.

This can return the following values:

• Poll::Pending if a permit is not currently available.
• Poll::Ready(Some(permit)) if a permit was acquired.
• Poll::Ready(None) if the semaphore has been closed.

When this method returns Poll::Pending, the current task is scheduled to receive a wakeup when a permit becomes available, or when the semaphore is closed. Note that on multiple calls to poll_acquire, only the Waker from the Context passed to the most recent call is scheduled to receive a wakeup.

pub fn poll_acquire_many( &mut self, cx: &mut Context<'_>, permits: u32, ) -> Poll<Option<OwnedSemaphorePermit>>

Poll to acquire many permits from the semaphore.

This can return the following values:

• Poll::Pending if a permit is not currently available.
• Poll::Ready(Some(permit)) if a permit was acquired.
• Poll::Ready(None) if the semaphore has been closed.

When this method returns Poll::Pending, the current task is scheduled to receive a wakeup when the permits become available, or when the semaphore is closed. Note that on multiple calls to poll_acquire, only the Waker from the Context passed to the most recent call is scheduled to receive a wakeup.

pub fn available_permits(&self) -> usize

Returns the current number of available permits.

This is equivalent to the Semaphore::available_permits method on the tokio::sync::Semaphore type.

pub fn add_permits(&self, n: usize)

Adds n new permits to the semaphore.

The maximum number of permits is Semaphore::MAX_PERMITS, and this function will panic if the limit is exceeded.

This is equivalent to the Semaphore::add_permits method on the tokio::sync::Semaphore type.

Trait Implementations

impl AsRef<Semaphore> for PollSemaphore

fn as_ref(&self) -> &Semaphore

Converts this type into a shared reference of the (usually inferred) input type.

impl Clone for PollSemaphore

fn clone(&self) -> PollSemaphore

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for PollSemaphore

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

Formats the value using the given formatter.

impl Stream for PollSemaphore

type Item = OwnedSemaphorePermit

Values yielded by the stream.

fn poll_next( self: Pin<&mut Self>, cx: &mut Context<'_>, ) -> Poll<Option<OwnedSemaphorePermit>>

Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted.

fn size_hint(&self) -> (usize, Option<usize>)

Returns the bounds on the remaining length of the stream.