Struct Semaphore 

pub struct Semaphore { /* private fields */ }

Counted async semaphore.

Implementations

impl Semaphore

pub const fn new(permits: usize) -> Self

Build a semaphore with permits initial permits.

Under --cfg loom, async_lock::Semaphore::new and event_listener::Event::new are deliberately non-const (loom’s model needs a runtime execution context). Only the const qualifier is affected; the constructed Semaphore is identical either way. Semaphore isn’t part of the loom-tested Notify/watch protocol, but the crate is built as one unit under --cfg loom, so this split just keeps it compiling.

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

Acquire one permit, awaiting if necessary. Returns Err(AcquireError) if the semaphore is (or becomes) closed while waiting.

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

Try to acquire one permit without waiting.

pub fn add_permits(&self, n: usize)

Inject n additional permits into the pool.

pub fn available_permits(&self) -> usize

Current available permit count. Snapshot only — may change concurrently before the caller observes the return value.

pub fn close(&self)

Close the semaphore. Pending and subsequent acquires return Err(AcquireError). Idempotent.

pub fn is_closed(&self) -> bool

true iff close() has been called.

Trait Implementations

impl Debug for Semaphore

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

Formats the value using the given formatter.