@wicle/mutex

Simple Mutex and Semaphore implementation written in TypeScript.

Semaphore uses Promise to implement posix semaphore functions, wait, post, and get value.

Mutex uses Semaphore to implement posix mutex funtions, lock, unlock, and tryLock.

Installation

# npm
npm i '@wicle/mutex'

# yarn
yarn add '@wicle/mutex'

# pnpm
pnom add '@wicle/mutex'

Usage

Semaphore

import { Semaphore } from 'mutex'

const sem = new Semaphore()
setTimeout(() => { sem.release() }, 1000)

console.time('semaphore wait')
await sem.wait()
console.timeEnd('semaphore wait')

Mutex

import { Mutex } from 'mutex'

const mtx = new Mutex()
let crit_data = 1

console.log('Access crit data #1')
await mtx.lock()
setTimeout(() => { crit_data = 2; mtx.unlock() }, 1000)

console.log('Access crit data #2')
await mtx.lock()
console.log('crit_data = ', crit_data)
mtx.unlock()

API

Semaphore

constructor

const sem = new Semaphore([value]) Create a new Semaphore instance. value is number of available resources, whcich defaults to 0.

sem.wait()

POSIX semaphore interface for sem_wait(). Returns a promise waiting for the semaphore to be signaled (resource available). Use await or Proimise.then() to wait for the signal.

await sem.wait()
// your code...

// or
sem.wait().then(()=>{
    // your code...
})

sem.tryWait()

POSIX semaphore interface for sem_trywait(). Check if tghe semaphore is signaled without waiting. Returns true if the semaphoire is in signaled state, or false

sem.post()

POSIX semaphore interface for sem_post(). Alias fore release() Returns void

sem.value

Semapohore value, whichi means resouce count currently available or signaled count.

sem.aquire()

Aquire semaphore resource. Alias to sem.wait(). Use await or Proimise.then() to wait for the resource to be aquired.

sem.tryAquire()

Try aquiring semaphore resource. returns immediately if the access not available. Alias to sem.tryWait(). Returns true if the access aquired, or false.

sem.release()

Release semaphore resource. Alias to sem.post().

Mutex

constructor

const mtx = new Mutex() Create a new Mutex instance.

mtx.lock()

Get access to the exclusive resource. Returns Promise to get the access the resource (lock). Use await or Proimise.then() to wait for the resource to be available.

await mtx.lock()
// your code...

// or
mtx.lock().then(()=>{
    // your code...
})

mtx.tryLock()

Try to get access to the exclusive resource without waiting. Returns true if the aquired, or false.

mtx.unlock()

Unlock the exclusive resource.

License

MIT