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node_modules/webpack/lib/util/processAsyncTree.js

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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;