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