55 lines
1 KiB
JavaScript
55 lines
1 KiB
JavaScript
'use strict';
|
|
|
|
const kDone = Symbol('kDone');
|
|
const kRun = Symbol('kRun');
|
|
|
|
/**
|
|
* A very simple job queue with adjustable concurrency. Adapted from
|
|
* https://github.com/STRML/async-limiter
|
|
*/
|
|
class Limiter {
|
|
/**
|
|
* Creates a new `Limiter`.
|
|
*
|
|
* @param {Number} [concurrency=Infinity] The maximum number of jobs allowed
|
|
* to run concurrently
|
|
*/
|
|
constructor(concurrency) {
|
|
this[kDone] = () => {
|
|
this.pending--;
|
|
this[kRun]();
|
|
};
|
|
this.concurrency = concurrency || Infinity;
|
|
this.jobs = [];
|
|
this.pending = 0;
|
|
}
|
|
|
|
/**
|
|
* Adds a job to the queue.
|
|
*
|
|
* @param {Function} job The job to run
|
|
* @public
|
|
*/
|
|
add(job) {
|
|
this.jobs.push(job);
|
|
this[kRun]();
|
|
}
|
|
|
|
/**
|
|
* Removes a job from the queue and runs it if possible.
|
|
*
|
|
* @private
|
|
*/
|
|
[kRun]() {
|
|
if (this.pending === this.concurrency) return;
|
|
|
|
if (this.jobs.length) {
|
|
const job = this.jobs.shift();
|
|
|
|
this.pending++;
|
|
job(this[kDone]);
|
|
}
|
|
}
|
|
}
|
|
|
|
module.exports = Limiter;
|