72 lines
1.6 KiB
Plaintext
72 lines
1.6 KiB
Plaintext
import Queue from 'yocto-queue';
|
|
import {AsyncResource} from '#async_hooks';
|
|
|
|
export default function pLimit(concurrency) {
|
|
if (!((Number.isInteger(concurrency) || concurrency === Number.POSITIVE_INFINITY) && concurrency > 0)) {
|
|
throw new TypeError('Expected `concurrency` to be a number from 1 and up');
|
|
}
|
|
|
|
const queue = new Queue();
|
|
let activeCount = 0;
|
|
|
|
const next = () => {
|
|
activeCount--;
|
|
|
|
if (queue.size > 0) {
|
|
queue.dequeue()();
|
|
}
|
|
};
|
|
|
|
const run = async (function_, resolve, arguments_) => {
|
|
activeCount++;
|
|
|
|
const result = (async () => function_(...arguments_))();
|
|
|
|
resolve(result);
|
|
|
|
try {
|
|
await result;
|
|
} catch {}
|
|
|
|
next();
|
|
};
|
|
|
|
const enqueue = (function_, resolve, arguments_) => {
|
|
queue.enqueue(
|
|
AsyncResource.bind(run.bind(undefined, function_, resolve, arguments_)),
|
|
);
|
|
|
|
(async () => {
|
|
// This function needs to wait until the next microtask before comparing
|
|
// `activeCount` to `concurrency`, because `activeCount` is updated asynchronously
|
|
// when the run function is dequeued and called. The comparison in the if-statement
|
|
// needs to happen asynchronously as well to get an up-to-date value for `activeCount`.
|
|
await Promise.resolve();
|
|
|
|
if (activeCount < concurrency && queue.size > 0) {
|
|
queue.dequeue()();
|
|
}
|
|
})();
|
|
};
|
|
|
|
const generator = (function_, ...arguments_) => new Promise(resolve => {
|
|
enqueue(function_, resolve, arguments_);
|
|
});
|
|
|
|
Object.defineProperties(generator, {
|
|
activeCount: {
|
|
get: () => activeCount,
|
|
},
|
|
pendingCount: {
|
|
get: () => queue.size,
|
|
},
|
|
clearQueue: {
|
|
value() {
|
|
queue.clear();
|
|
},
|
|
},
|
|
});
|
|
|
|
return generator;
|
|
}
|