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57 lines
1.1 KiB
JavaScript
57 lines
1.1 KiB
JavaScript
module.exports = class Queue {
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/**
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* A really simple queue with concurrency that optionally
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* only adds unique tasks.
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*
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* @param {Function(Object, Function)} worker
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* @param {Object} options
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*/
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constructor(worker, options) {
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this._worker = worker;
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options = options || {};
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this._concurrency = options.concurrency || 1;
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this.tasks = [];
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this.active = 0;
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}
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/**
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* Push a task to the queue.
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*
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* @param {Object} item
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* @param {Function(Error)} callback
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*/
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push() {
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this.tasks.push(arguments);
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this._next();
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}
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/**
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* Process next job in queue.
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*/
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_next() {
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if (this.active >= this._concurrency || !this.tasks.length) { return; }
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let task = this.tasks.shift();
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let item = task[0];
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let callback = task[1];
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let callbackCalled = false;
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this.active++;
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this._worker(item, (err) => {
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if (callbackCalled) { return; }
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this.active--;
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callbackCalled = true;
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if (callback) { callback(err); }
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this._next();
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});
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}
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/**
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* Stops processing queued jobs.
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*/
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die() {
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this.tasks = [];
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}
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};
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