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