128 lines
3.2 KiB
JavaScript
128 lines
3.2 KiB
JavaScript
import Queue from 'yocto-queue';
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export default function pLimit(concurrency) {
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let rejectOnClear = false;
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if (typeof concurrency === 'object') {
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({concurrency, rejectOnClear = false} = concurrency);
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}
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validateConcurrency(concurrency);
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if (typeof rejectOnClear !== 'boolean') {
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throw new TypeError('Expected `rejectOnClear` to be a boolean');
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}
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const queue = new Queue();
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let activeCount = 0;
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const resumeNext = () => {
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// Process the next queued function if we're under the concurrency limit
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if (activeCount < concurrency && queue.size > 0) {
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activeCount++;
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queue.dequeue().run();
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}
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};
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const next = () => {
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activeCount--;
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resumeNext();
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};
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const run = async (function_, resolve, arguments_) => {
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// Execute the function and capture the result promise
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const result = (async () => function_(...arguments_))();
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// Resolve immediately with the promise (don't wait for completion)
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resolve(result);
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// Wait for the function to complete (success or failure)
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// We catch errors here to prevent unhandled rejections,
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// but the original promise rejection is preserved for the caller
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try {
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await result;
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} catch {}
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// Decrement active count and process next queued function
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next();
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};
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const enqueue = (function_, resolve, reject, arguments_) => {
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const queueItem = {reject};
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// Queue the internal resolve function instead of the run function
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// to preserve the asynchronous execution context.
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new Promise(internalResolve => { // eslint-disable-line promise/param-names
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queueItem.run = internalResolve;
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queue.enqueue(queueItem);
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}).then(run.bind(undefined, function_, resolve, arguments_)); // eslint-disable-line promise/prefer-await-to-then
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// Start processing immediately if we haven't reached the concurrency limit
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if (activeCount < concurrency) {
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resumeNext();
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}
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};
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const generator = (function_, ...arguments_) => new Promise((resolve, reject) => {
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enqueue(function_, resolve, reject, arguments_);
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});
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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.size,
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},
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clearQueue: {
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value() {
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if (!rejectOnClear) {
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queue.clear();
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return;
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}
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const abortError = AbortSignal.abort().reason;
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while (queue.size > 0) {
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queue.dequeue().reject(abortError);
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}
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},
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},
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concurrency: {
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get: () => concurrency,
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set(newConcurrency) {
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validateConcurrency(newConcurrency);
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concurrency = newConcurrency;
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queueMicrotask(() => {
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// eslint-disable-next-line no-unmodified-loop-condition
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while (activeCount < concurrency && queue.size > 0) {
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resumeNext();
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}
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});
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},
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},
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map: {
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async value(iterable, function_) {
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const promises = Array.from(iterable, (value, index) => this(function_, value, index));
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return Promise.all(promises);
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},
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},
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});
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return generator;
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}
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export function limitFunction(function_, options) {
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const limit = pLimit(options);
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return (...arguments_) => limit(() => function_(...arguments_));
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}
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function validateConcurrency(concurrency) {
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if (!((Number.isInteger(concurrency) || concurrency === Number.POSITIVE_INFINITY) && concurrency > 0)) {
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throw new TypeError('Expected `concurrency` to be a number from 1 and up');
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}
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}
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