Created
August 6, 2019 17:09
-
-
Save TerrorJack/60b6a5b7b28902f7569ccfc5542e2c1f to your computer and use it in GitHub Desktop.
Async JavaScript Semaphores
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
function semSetPromise(sem) { | |
delete sem.promise; | |
delete sem.resolve; | |
sem.promise = new Promise(resolve => { | |
if (sem.left) { | |
--sem.left; | |
resolve(); | |
} else { | |
sem.resolve = resolve; | |
} | |
}); | |
} | |
function semTake(sem) { | |
return sem.promise.then(() => semSetPromise(sem)); | |
} | |
function semPut(sem) { | |
++sem.left; | |
if (sem.resolve) { | |
sem.resolve(); | |
semSetPromise(sem); | |
} | |
} | |
export class Sem { | |
static async create(n) { | |
const sem = new Sem(); | |
sem.left = n; | |
semSetPromise(sem); | |
return sem; | |
} | |
take() { | |
return semTake(this); | |
} | |
put() { | |
semPut(this); | |
} | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment