53 lines
1.0 KiB
JavaScript
53 lines
1.0 KiB
JavaScript
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'use strict';
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const pTry = require('p-try');
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const pLimit = concurrency => {
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if (!((Number.isInteger(concurrency) || concurrency === Infinity) && concurrency > 0)) {
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return Promise.reject(new TypeError('Expected `concurrency` to be a number from 1 and up'));
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}
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const queue = [];
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let activeCount = 0;
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const next = () => {
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activeCount--;
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if (queue.length > 0) {
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queue.shift()();
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}
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};
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const run = (fn, resolve, ...args) => {
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activeCount++;
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const result = pTry(fn, ...args);
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resolve(result);
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result.then(next, next);
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};
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const enqueue = (fn, resolve, ...args) => {
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if (activeCount < concurrency) {
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run(fn, resolve, ...args);
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} else {
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queue.push(run.bind(null, fn, resolve, ...args));
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}
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};
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const generator = (fn, ...args) => new Promise(resolve => enqueue(fn, resolve, ...args));
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Object.defineProperties(generator, {
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activeCount: {
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get: () => activeCount
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},
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pendingCount: {
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get: () => queue.length
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}
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});
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return generator;
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};
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module.exports = pLimit;
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module.exports.default = pLimit;
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