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'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;
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