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node_modules/webpack/lib/util/ArrayQueue.js

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+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Tobias Koppers @sokra
+*/
+
+"use strict";
+
+/**
+ * @template T
+ */
+class ArrayQueue {
+	/**
+	 * @param {Iterable<T>=} items The initial elements.
+	 */
+	constructor(items) {
+		/** @private @type {T[]} */
+		this._list = items ? Array.from(items) : [];
+		/** @private @type {T[]} */
+		this._listReversed = [];
+	}
+
+	/**
+	 * Returns the number of elements in this queue.
+	 * @returns {number} The number of elements in this queue.
+	 */
+	get length() {
+		return this._list.length + this._listReversed.length;
+	}
+
+	/**
+	 * Empties the queue.
+	 */
+	clear() {
+		this._list.length = 0;
+		this._listReversed.length = 0;
+	}
+
+	/**
+	 * Appends the specified element to this queue.
+	 * @param {T} item The element to add.
+	 * @returns {void}
+	 */
+	enqueue(item) {
+		this._list.push(item);
+	}
+
+	/**
+	 * Retrieves and removes the head of this queue.
+	 * @returns {T | undefined} The head of the queue of `undefined` if this queue is empty.
+	 */
+	dequeue() {
+		if (this._listReversed.length === 0) {
+			if (this._list.length === 0) return undefined;
+			if (this._list.length === 1) return this._list.pop();
+			if (this._list.length < 16) return this._list.shift();
+			const temp = this._listReversed;
+			this._listReversed = this._list;
+			this._listReversed.reverse();
+			this._list = temp;
+		}
+		return this._listReversed.pop();
+	}
+
+	/**
+	 * Finds and removes an item
+	 * @param {T} item the item
+	 * @returns {void}
+	 */
+	delete(item) {
+		const i = this._list.indexOf(item);
+		if (i >= 0) {
+			this._list.splice(i, 1);
+		} else {
+			const i = this._listReversed.indexOf(item);
+			if (i >= 0) this._listReversed.splice(i, 1);
+		}
+	}
+
+	[Symbol.iterator]() {
+		let i = -1;
+		let reversed = false;
+		return {
+			next: () => {
+				if (!reversed) {
+					i++;
+					if (i < this._list.length) {
+						return {
+							done: false,
+							value: this._list[i]
+						};
+					}
+					reversed = true;
+					i = this._listReversed.length;
+				}
+				i--;
+				if (i < 0) {
+					return {
+						done: true,
+						value: undefined
+					};
+				}
+				return {
+					done: false,
+					value: this._listReversed[i]
+				};
+			}
+		};
+	}
+}
+
+module.exports = ArrayQueue;