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/*
MIT License http://www.opensource.org/licenses/mit-license.php
Author Tobias Koppers @sokra
*/
"use strict";
/**
* @template T
* @template {Error} E
* @param {Iterable<T>} items initial items
* @param {number} concurrency number of items running in parallel
* @param {function(T, function(T): void, function(E=): void): void} processor worker which pushes more items
* @param {function(E=): void} callback all items processed
* @returns {void}
*/
const processAsyncTree = (items, concurrency, processor, callback) => {
const queue = Array.from(items);
if (queue.length === 0) return callback();
let processing = 0;
let finished = false;
let processScheduled = true;
/**
* @param {T} item item
*/
const push = item => {
queue.push(item);
if (!processScheduled && processing < concurrency) {
processScheduled = true;
process.nextTick(processQueue);
}
};
/**
* @param {E | null | undefined} err error
*/
const processorCallback = err => {
processing--;
if (err && !finished) {
finished = true;
callback(err);
return;
}
if (!processScheduled) {
processScheduled = true;
process.nextTick(processQueue);
}
};
const processQueue = () => {
if (finished) return;
while (processing < concurrency && queue.length > 0) {
processing++;
const item = /** @type {T} */ (queue.pop());
processor(item, push, processorCallback);
}
processScheduled = false;
if (queue.length === 0 && processing === 0 && !finished) {
finished = true;
callback();
}
};
processQueue();
};
module.exports = processAsyncTree;
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