Struct Semaphore

pub struct Semaphore { /* private fields */ }

A type that asynchronously distributes “permits.”

A permit is a token that allows the holder to perform some action. The semaphore itself does not dictate this action, but instead handles only the distribution of permits. This is useful for cases where you want to limit the number of concurrent operations, such as in a mutex.

n permits can be acquired through acquire. They can later be released through release.

Examples

For examples, look at the implementations of Mutex and RwLock. Mutex uses a semaphore with a maximum of 1 permit to allow a single lock at a time. RwLock uses a semaphore with a maximum of max_readers permits to allow any number of readers. When a write call is encountered, it acquires all of the permits, blocking any new readers from locking.

Implementations

impl Semaphore

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

Creates a new Semaphore with the given initial number of permits.

pub fn acquire(&self, n: usize) -> Acquire<'_>

Acquires n permits from the semaphore. These permits should be released later, or they will be permanently removed.

pub fn release(&self, n: usize)

Releases n permits back to the semaphore.

pub fn remaining(&self) -> usize

Returns the number of remaining permits.