Struct Semaphore 

pub struct Semaphore { /* private fields */ }

A counting semaphore: .acquire().await waits (without blocking the OS thread) until a permit is available, then holds it until the returned SemaphorePermit is dropped.

Implementations

impl Semaphore

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

Create a semaphore with permits available immediately.

pub fn available_permits(&self) -> usize

Current number of permits available for immediate acquisition.

pub fn add_permits(&self, n: usize)

Add n permits, waking waiters as needed.

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

Acquire one permit, waiting if none are currently available.

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

Acquire one permit if immediately available, without waiting.

Errors

Returns TryAcquireError::NoPermits if none are currently free.