init

马宇豪

2024-07-16 f591c27b57e2418c9495bc02ae8cfff84d35bc18

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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;
 
    const push = item => {
        queue.push(item);
        if (!processScheduled && processing < concurrency) {
            processScheduled = true;
            process.nextTick(processQueue);
        }
    };
 
    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 = queue.pop();
            processor(item, push, processorCallback);
        }
        processScheduled = false;
        if (queue.length === 0 && processing === 0 && !finished) {
            finished = true;
            callback();
        }
    };
 
    processQueue();
};
 
module.exports = processAsyncTree;